PATELLA FRACTURES AND EXTENSOR MECHANISM INJURIES

Transcription

LWBK1304-C54_p01-34.indd Page 1 11/26/13 12:42 PM user
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Patella Fractures and
Extensor Mechanism
Injuries
J. Stuart Melvin and Madhav A. Karunakar
INTRODUCTION TO PATELLAR FRACTURES
ASSESSMENT OF PATELLAR FRACTURES
[AU1] Patellar Fracture Injury Mechanisms
Injuries Associated with Patellar Fractures
Signs and Symptoms
Imaging and Other Diagnostic Studies
Classification
Outcome Measures
PATHOANATOMY AND APPLIED ANATOMY RELATING
TO PATELLA FRACTURES
Osseous Anatomy
Arterial Blood Supply
Soft Tissue Anatomy
BIOMECHANICS OF THE EXTENSOR MECHANISM
PATELLAR FRACTURE TREATMENT OPTIONS
Nonoperative Treatment
Operative Treatment
Open Fractures
AUTHOR’S PREFERRED METHOD OF TREATMENT FOR
PATELLA FRACTURES
Patients with an Intact Extensor Mechanism, Vertical
Fractures, and Minimal Articular Displacement or
Patients Unfit for Anesthesia
Displaced Fractures
Postoperative Management
INTRODUCTION TO EXTENSOR MECHANISM
INJURIES
ASSESSMENT OF EXTENSOR MECHANISM INJURIES
Extensor Injury Mechanisms
Injuries Associated with Extensor Mechanism
Signs and Symptoms
PATHOANATOMY AND APPLIED ANATOMY RELATING
TO EXTENSOR MECHANISM INJURIES
Imaging and Other Diagnostic Studies
EXTENSOR MECHANISM INJURY TREATMENT
OPTIONS
Historical Perspective
Nonoperative Treatment
Operative Treatment
AUTHOR’S PREFERRED TECHNIQUE FOR QUADRICEPS
TENDON REPAIR
Acute Patellar Tendon Rupture
Tibial Tubercle Avulsions
Acute Patellar Dislocations
AUTHOR’S PREFERRED TECHNIQUE FOR ACUTE
PATELLAR DISLOCATIONS
MANAGEMENT OF EXPECTED ADVERSE OUTCOMES
AND UNEXPECTED COMPLICATIONS IN EXTENSOR
MECHANISM INJURIES
[AU2]
Loss of Knee Motion
Extensor Mechanism Weakness
Symptomatic Retained Hardware
Infection and Wound Complications
Loss of Fixation/Refracture/Rerupture
Delayed Union and Nonunion
Post-traumatic Arthritis/Pain
SUMMARY, CONTROVERSIES, AND FUTURE
DIRECTIONS
1
2 Section four Lower Extremity
Introduction to Patellar
Fractures
The treatment of patella fractures has evolved with improvements in both fracture fixation techniques and an improved
understanding of patellar function. Until the 19th century, the
vast majority of patella fractures were treated nonoperatively
with extension splinting. The critical structural and biomechanical functions of the patella were not understood, such
that excision of a “vestigial embryologic remnant” was felt to
be a reasonable option.1 Brooke1 published results showing
increased limb strength after patellectomy compared to normal controls, and advocated patellectomy as a viable surgical option. Hey-Groves2 and Watson-Jones3 believed that the
patella inhibited quadriceps function, and concluded that the
strength of the knee was improved after patellectomy. Blodgett
and Fairchild,4 Thompson,5 and Seligo6 published additional
clinical series describing excellent clinical results with partial
or complete patellar excision for fracture.
The appeal of nonoperative treatment or total excision was
tempered, however, by modest functional outcomes. Extension
splinting was associated with high rates of residual pain, nonunion, and permanent disability.7 Furthermore, laboratory and
clinical studies raised concern regarding outcomes after pat[AU3] ellectomy. Cohn8 and Kelly et al.9 demonstrated degenerative
changes on the femoral articular surface after patellectomy in a
rabbit model. A high rate of patient dissatisfaction, decreased
quadriceps strength, residual pain, and functional disability
were also reported after total patellectomy.10–16
In the 1940s, laboratory studies by Haxton17 and others demonstrated the critical biomechanical function of the patella and
highlighted the importance of its preservation to optimize function of the extensor mechanism. With advances in aseptic surgery
and techniques in fracture fixation, significant interest developed
in identifying alternative means of treatment for these injuries.
Malgaigne designed the “griffe metallique” in 1843, a metal claw
connected to sliding plates designed to reapproximate fragments
in displaced patellar fracture patterns.18,19 Sir Hector Cameron20
of Glasgow, Scotland performed the first open reduction and
internal fixation of a patella fracture in 1877 with interfragmentary wiring. Lister21 and Trendelenburg performed similar procedures in Germany using drill holes and wire fixation. Numerous
techniques of fracture reduction and fixation emerged, but stable
fixation was difficult to achieve.2,22–24 Materials used for fixation
included percutaneous pins, metal loops, kangaroo tendon xenografts, fascial strips, and screws.2,22–24
The greatest advance in patellar fracture fixation, however,
occurred in the 1950s with presentation of the anterior tension
[AU4] band technique by Muller et al.25 The Arbeitsgemeinschaft für
Osteosynthesefragen/Association for the Study of Internal Fixation (AO/ASIF) subsequently modified and advocated tension
band fixation as a rigid construct that allowed for early range
of motion and rehabilitation of patella fractures.25 Weber et al.26
demonstrated superior biomechanical strength with modified
anterior tension banding and retinacular repair in a transverse
patellar fracture model compared to cerclage or interfragmentary
wiring techniques. Numerous clinical series have subsequently
confirmed a high rate of success with tension band wiring techniques.27–30 Currently three forms of operative treatment for displaced patella fractures are most commonly utilized.
• Open reduction and internal fixation, usually with a tension
band wiring technique or cannulated screw tension band
technique
• Partial patellectomy
• Total patellectomy
The indications for each technique are individualized and
dependent on the fracture pattern, patient activity level, and
functional expectations. Each procedure can achieve good to
excellent results with proper patient selection and application.
Regardless of the selected technique, the goals of surgical treatment include the following.
• Restoration of the functional integrity and strength of the
extensor mechanism
• Maximizing articular congruity
• Preservation of patellar bone
Assessment of Patellar Fractures
Patellar Fracture Injury Mechanisms
Fractures of the patella account for approximately 1% of all skeletal fractures and may result from direct, indirect, or combined
injury patterns.31 The patella is prone to injury from a direct
blow as a consequence of its anterior location and thin overlying
soft tissue envelope. Direct injuries may be low energy, such as
after a fall from a sitting or standing height, or high energy, as
from a dashboard impact in a motor vehicle collision. Comminuted fracture patterns are often the result of high-energy, direct
injuries. In these cases, it is critical to survey for associated injuries of the ipsilateral limb, including hip dislocation, proximal
femur fractures, or fractures about the knee.
Indirect injuries occur secondary to the large forces generated through the extensor mechanism, and typically result from
forceful contraction of the quadriceps with the knee in a flexed
position. The substantial force generated by a violent quadriceps
contraction fractures the patella and may propagate through the
adjacent retinaculum of the extensor mechanism. As a result,
indirect injuries frequently cause a greater degree of retinacular
disruption compared with direct injuries and active knee extension is compromised in most cases. The degree of fragment
displacement is generally representative of occult injury to the
adjacent soft tissue envelope. While transverse fracture patterns
are associated with an indirect injury mechanism, it is clear that
fracture pattern is not solely determined by injury mechanism,
and is also dependent on various other factors such as patient
age, bone quality, and the degree of knee flexion. In reality,
patellar fractures likely reflect a combination of both direct and
indirect forces: The culmination of a direct blow, quadriceps
muscle contraction, and secondary joint collapse.
The majority of patellar fractures have a transverse fracture pattern resulting from excessive tensile forces through the
extensor mechanism. These may occur through the body, apex,
Chapter 54 Patella Fractures and Extensor Mechanism Injuries 3
or distal pole of the patella. Small proximal or distal avulsiontype fractures should not be ignored, as they are often associated
with substantial soft tissue injury to the quadriceps or patellar tendon. Vertical fractures are typically the result of a direct
blow to a partially flexed knee, and may be nondisplaced if the
retinaculum and extensor mechanism are intact. Comminuted,
stellate fracture patterns are typically the result of a direct blow
with impaction against the femoral condyles, and can be associated with substantial injury to both the femoral and patellar
chondral surfaces.
Injuries Associated with Patellar Fractures
Concomitant injuries occur commonly in association with
patella fractures and, as expected, occur more frequently in
higher-energy injures.32 Without stratifying according to injury
mechanism, two large series of patella fractures reported by
Boström31 and Noble and Hakek33 demonstrated associated
injury rates of 15% and 28.1%, respectively. Associated injury
occurred even more frequently with open patellar fractures with
rates approaching 80%.32,34 Most often, associated injuries occur
in the ipsilateral lower extremity. A recent investigation at the
author’s institution of 300 consecutive patellar fractures found
ipsilateral distal femur or proximal tibia fracture to accompany
26% of patella fractures. Catalano et al.34 reported a 44% rate
of ipsilateral lower-extremity fracture in a series of open patellar fractures. This contrasts ipsilateral with lower-extremity
[AU5] fracture rates of around 5% by Boström31 and Günal et al.,128
and highlights the increasing rate of high-energy patella fractures encountered today. Less literature exists regarding extensor mechanism rupture and associated injuries. While these
injuries are more frequently the result of low-energy trauma
compared to patellar fractures, a similar association between
increasing energy of injury mechanism and increasing rate of
ipsilateral knee injury has been described.35 Thus, knowledge
of a high-energy mechanism should alert the surgeon to the
increased probability of associated injuries, especially of the
ipsilateral lower extremity.
Signs and Symptoms of Patellar Fractures
Patient history typically includes a direct blow to the patella, a
fall from a standing height, or a near fall with forceful contraction of the quadriceps on a partially flexed knee. Correlation
of the fracture with the mechanism of injury will help the surgeon to anticipate both the fracture pattern and the degree of
soft tissue injury. Complaints of anterior knee pain, swelling,
and difficulty ambulating after a fall are also common and may
reflect an injury to the extensor mechanism. With high-energy
injuries, the surgeon must have a low threshold of suspicion for
associated musculoskeletal injuries.
On physical examination, displaced patella fractures typically present with an acute hemarthrosis and a tender, palpable defect between the fracture fragments. The absence
of a large effusion in the presence of a palpable bony defect
should raise concern for associated retinacular tears. Competence of the extensor mechanism must be assessed by asking
the patient to perform a straight-leg raise or extend a partially
flexed knee against gravity. A large hemarthrosis may be very
painful, and limit the ability of the patient to comply with this
part of the examination. In these situations, aspiration of the
hemarthrosis followed by injection of a local anesthetic into
the joint may be helpful. It is critical to note, however, that
the patient’s ability to extend the knee does not rule out a patella
fracture, but rather it suggests that the continuity of the extensor
mechanism is maintained via an intact retinacular sleeve.
Lacerations or abrasions to the skin overlying the patella
are of particular concern, and may reflect an occult open fracture or communication with the knee joint. Any concern warrants further investigation with a saline load test.36 A large bore,
18-gauge needle and syringe are used to perform a joint aspiration, followed by infusion of 150 mL of saline into the knee
joint. Communication between the knee joint and the wound is
marked by egress of the infused saline from the wound. Methylene blue may be added to the saline infusion to facilitate detection. Open fractures or traumatic arthrotomies warrant urgent
irrigation and debridement in the operating room.
After a careful examination is completed, the knee should be
splinted, iced, and elevated. The knee is typically immobilized
in a slightly flexed position for comfort until definitive treatment is rendered.
Patellar Fracture Imaging and Other
Diagnostic Studies
[AU6]
Plain Radiographs
Plain radiography is typically sufficient to confirm the diagnosis of patellar fracture or injury to the extensor mechanism.
Anteroposterior (AP), lateral, and tangential or axial views of
the patellofemoral joint should be obtained (Fig. 54-1). Views
of the contralateral knee are helpful for comparison and may
prevent the erroneous diagnosis of a normal anatomical variant
as a fracture.
In the setting of a patellar fracture, the AP view should be
taken with the largest cassette possible (typically 14 × 17 in) [AU7]
placed behind the knee of the supine patient. If full knee extension is not possible secondary to pain, the x-ray beam trajectory
must be adjusted accordingly. Leg rotation must be controlled,
so that the patella is pointing straight up and will be centered on
the film. The patella should lie within the midline of the femoral
sulcus, and the distal pole should be no higher than 20 mm
above a tangential line connecting the distal femoral condyles.
Vertical and horizontal fracture lines should be carefully noted.
Typically, the degree of fracture comminution is underestimated
by the radiographically evident fracture lines. The distal femur
and proximal tibia should not be ignored and must be carefully
inspected for occult condylar or plateau fractures.
A bipartite or tripartite patella can often be mistaken for a
fracture in the setting of a trauma history (Fig. 54-2). These
anatomical variants reflect incomplete fusion of two or more
ossification centers. The opposing edges are usually smooth
and corticated on plain radiographs. The finding is typically
bilateral, and contralateral knee radiographs often confirm the
diagnosis. The most common bipartite pattern is located in the
superolateral aspect of the patella, and is not associated with
A,B
C
Figure 54-1 Anteroposterior (A), lateral (B), and axial (C) views of a displaced transverse patella
fracture.
any pain, tenderness, or functional compromise of the extensor
mechanism on physical examination. A true unilateral bipartite
patella is extremely rare, and may represent an old avulsiontype patellar fracture.
The lateral radiographic view is critical to define fracture
pattern and associated extensor mechanism disruption. Controlling limb rotation, however, is essential to obtain a true
lateral view that allows for reliable determination of patellar
height and identification of occult injuries. The distal patellar
pole and tibial tubercle should be carefully inspected for subtle
avulsion fractures. Patellar height should be assessed using the
Insall–Salvati ratio, which compares the height of the patella to
the length of the patellar tendon. In a normal subject, a ratio of
1.02 ± 0.13 is expected.37 A ratio of less than 1 suggests patella
alta and disruption of the patellar tendon. A ratio of greater
than 1 is associated with patella baja and quadriceps tendon
A
B
Figure 54-2 Anteroposterior (A) and lateral (B) radiographs of a bipartite patella. Note the superolateral fragment with well-defined cortical margins.
a
b
b
2 cm
B
A
ration b/a > 1.2
Figure 54-3 The red lines depict abnormal conditions. A: The length of the patellar
tendon should approximate the midsagittal
length of the patella and the inferior pole of
the patella projects to the level of Blumensaat line (dashed line). A ratio of the length
of the tendon to the length of the patella
greater than 1.2 indicates possible injury
to the patellar tendon (method of Insall).
B: On the anteroposterior radiograph, the
inferior pole of the patella should lie within
2 cm of a plane formed by the distal femoral condyles. C: At 90 degrees of flexion
the superior pole of the patella should lie
inferior to the anterior surface of the femoral shaft. D: The lateral view gives the best
view of the fracture pattern and of frag[AU19] ment separation.
3–4 mm
C
disruption.37 Other, less sensitive indices of patellar height can
also be assessed on the lateral view. With the knee flexed 90
degrees, the proximal patellar pole normally rests at or below
the level of the anterior cortex of the femur (Fig. 54-3).37,38
With the knee flexed 30 degrees, the inferior patellar pole normally projects to the level of Blumensaat line (the distal physeal scar remnant).37,38 Loss of this relationship is suggestive of
extensor mechanism disruption.
A tangential or axial view of the patellofemoral joint is also
useful. With patellar fractures, vertical or marginal fracture lines
and associated osteochondral defects may only be visualized
on this view. Merchant et al.39 described their technique for
obtaining an axial view of the patella. With the patient supine
and the knees flexed 45 degrees over the edge of the table, the
x-ray beam is angled 30 degrees below horizontal with the cassette placed approximately 6 to 12 in below the knees and perpendicular to the beam. This technique is easily performed in
patients with knee trauma, as supporting the knee in a partially
flexed position often confers maximal comfort in the setting of
an acute hemarthrosis.
D
Computed Tomography
Computed tomography (CT) scanning is rarely necessary in the
evaluation and treatment of isolated patellar fractures. Frequently,
however, the patella may be incidentally imaged during the evaluation of an ipsilateral distal femoral or proximal tibial fracture.
While CT allows for improved evaluation of articular congruity
and fracture comminution, it rarely provides additional information that will alter the treatment plan that has been determined
on the basis of physical examination and plain radiographs.
CT scanning plays a more important role in the evaluation
of patellar stress fracture, nonunion, or malunion. Apple et al.40
demonstrated a 71% sensitivity of tomography in detecting
stress fractures in elderly, osteopenic patients, compared to 30%
with bone scans and 0% with plain radiographs alone. CT is also
useful to characterize trochlear anatomy and lower-extremity
rotational alignment with patellofemoral tracking disorders.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) has been used increasingly
to evaluate suspected extensor mechanism injuries as well as
chondral injuries associated with patellar dislocations.41,42 In
addition, MRI may have a role in the evaluation of acute patellar fractures considered for nonoperative treatment in which
suspicion exists for an osteochondral fracture. However, MRI
for acute patellar fractures is not routinely utilized.
The normal quadriceps and patellar tendons have a laminated appearance with homogeneous, low signal intensity on
MRI. Trauma to the patella or adjacent soft tissues results in
hemorrhage and edema, and is associated with increased signal
intensity on T2-weighted images. Furthermore, loss of continuity of patellar or quadriceps tendon fibers can be readily seen to
define both partial and complete disruptions.41,42 Lateral patellar dislocations are associated with a characteristic edema pattern on MRI that allows for confirmation of the diagnosis even
after spontaneous reduction following the injury. In addition to
a traumatic effusion, contusion of the lateral femoral condyle
and medial patellar facet with increased signal on T2-weighted
images, disruption of the medial patellofemoral ligament, retinacular tears, and osteochondral loose bodies are frequently
seen.41 In the absence of patella fracture on radiographs, blunt
direct trauma to the patella such as with a dashboard mechanism
has been found to be associated with subchondral microfracture
on MRI in approximately 40% of cases. The long-term significance of these subchondral microfractures remains uncertain.43
More sophisticated imaging techniques to evaluate the
articular cartilage such as T2 mapping, T1rho or delayed gadolinium-enhanced imaging of articular cartilage (dGEMRIC)
allow for the identification of chondral injuries that may not be
visualized on plain radiographs; however, these sequences have
most often been employed in the management of osteoarthrosis
and sports injuries rather than acute traumatic patellar injury.44
Patellar Fracture Classification
Patellar fracture classification is typically descriptive in nature,
and can be based on fracture pattern, degree of displacement,
or mechanism of injury. A formal classification has been proposed by the Orthopaedic Trauma Association (OTA) and is
based on the degree of articular involvement and the number
of fracture fragments. However, this classification has not been
validated and the clinical utility of this system remains uncertain. Despite these deficiencies, the current OTA classification
is important for standardizing the classification of patellar fractures for clinical research. Prior to the OTA classification, patellar fracture classification lacked standardization and thus most
clinical series have reported outcomes based on the type of fixation rather than fracture pattern.27,28,31,33,45–47
A useful approach in the clinical setting begins with classifying patellar fractures as displaced or nondisplaced. Displaced
patellar fractures are defined by separation of fracture fragments by more than 3 mm or articular incongruity of more
than 2 mm. After the fracture is classified as displaced or nondisplaced, the injury can be further categorized on the basis
of the geometric configuration of fracture lines. Described patterns include transverse or horizontal, stellate or comminuted,
vertical or longitudinal, apical or marginal, and osteochondral
(Fig. 54-4). In addition, a special category of patellar sleeve
fractures can occur in skeletally immature patients in which
Undisplaced
Transverse
Multifragmented
displaced
Lower or
upper pole
Vertical
Multifragmented
undisplaced
Osteochondral
Figure 54-4 Descriptive classification of patellar fractures.
a distal pole fragment with a large component of the articular
surface avulses from the remaining patella.48,49
Nondisplaced Fractures
Transverse. As many as 35% of transverse patellar fractures are nondisplaced.31,50 While the mechanism may be multifactorial in nature, these injuries are typically associated with
indirect, longitudinal forces that fracture the patella but are
insufficient to tear the medial and lateral patellar retinacula.
As a result, the extensor mechanism remains competent. The
preserved integrity of the soft tissue envelope helps to maintain
the reduction. Approximately 80% of these fractures occur in
the middle to lower third of the patella.51
Stellate. Stellate fractures typically result from direct blow
injuries to the patella with the knee in a partially flexed position.
Approximately 65% of these injuries are nondisplaced.31,52 Active
knee extension is preserved, as the medial and lateral patellar
retinacula are usually not torn with the injury. Damage to the
patellar and femoral articular surface is not uncommon given the
mechanism of injury, and careful evaluation on tangential views
or MRI is necessary to identify occult osteochondral lesions.
Vertical. A vertical or longitudinal fracture pattern is not
uncommon and has been reported to account for 12% to 22%
of patellar fractures in several large series.51,53,54 The fracture
line is most commonly seen involving the lateral facet and lying
between the middle and lateral third of the patella. Different
mechanisms of injury have been implicated. Boström55 reported
that lateral avulsion was the most common mechanism in 75%
of their series. Dowd,54 however, reported that direct compression of the patella in a hyperflexed knee is responsible for this
pattern of injury. The patellar retinacula are intact, preserving
active knee extension by the patient. The fracture pattern is easily missed on an AP radiograph, emphasizing the importance of
an axial view to identify this injury.
Displaced Fractures
Transverse. Noncomminuted, transverse fractures account
for approximately 52% of displaced patellar fractures.13,27,28,31
Evaluation of the integrity of the extensor mechanism is critical with this pattern of injury. The fracture fragment separation
(>3 mm) is suggestive but not diagnostic of retinacular and
extensor mechanism disruption. A subset of these fractures with
fragment displacement but intact retinacula exists, and is characterized by preservation of full active knee extension. These fractures may respond more favorably to nonoperative treatment.
Boström31 has reported that preservation of the retinacula allows
satisfactory healing without surgery. McMaster,56 however, has
warned of a high risk of nonunion with nonoperative treatment
in these patients.
Stellate. Displaced, stellate fractures usually result from a
high energy, direct blow to the patella. These fractures typically
demonstrate a high degree of comminution. Anterior soft tissue
contusion and/or lacerations are not uncommon, and careful
evaluation for an open fracture or traumatic arthrotomy is warranted. Transverse fracture lines with extensive comminution
may result in propagation into the retinaculum and disruption of the extensor mechanism. However, even if the extensor
mechanism is preserved, the significant articular incongruity
may warrant operative intervention.
Pole Fractures. Fractures at the proximal pole of the
patella are typically bony avulsions of the quadriceps mechanism. Displacement is rare and has been reported to be approximately 4% in large clinical series.6,31 Active knee extension
may be preserved if the medial and lateral retinacula remain
intact. The lateral radiograph may demonstrate patella baja and
a reduced Insall–Salvati ratio. Distal pole fractures are bony
avulsions of the patellar tendon. Displacement is much more
common with these injuries and has been reported to occur in
up to 11.5% in large series.6,31 Retinacular disruption with loss
of knee extension is virtually universal with distal pole fractures. A lateral radiograph will demonstrate patella alta and an
increased Insall–Salvati ratio.37
Osteochondral Fractures. Osteochondral fractures of
the femur or patella are also seen in association with highenergy, stellate patellar fractures or after patellar dislocation.
Plain radiographs may not demonstrate these lesions. MRI with
cartilage-sensitive sequences can improve the detection of these
injuries.42 Osteochondral fracture fragments can shear from the
lateral femoral condyle or medial patellar facet after patellar
subluxation or dislocation, and may warrant surgical intervention. Kroner57 first reported on a series of these fractures after
patellar subluxation in patients 15 to 20 years of age.
Fractures after Bone–Tendon–Bone Harvest. Patellar fractures have been infrequently reported after graft harvest
for bone–tendon–bone anterior cruciate ligament (ACL) reconstruction. An incidence of 0.2% has been reported in one series
of over 1,700 ACL reconstructions.58 While these may occur
intraoperatively secondary to technical error, the majority of
cases have been attributed to postoperative trauma from a fall
or overly aggressive rehabilitation protocols. Both transverse
and vertical fracture patterns have been reported. Rigid fixation
of these fractures, even in the setting of minimal displacement,
has been advocated to allow for early motion and avoid delayed
rehabilitation of the ACL reconstruction.
Masqueraders. A bipartite or tripartite patella is a normal
anatomical variant and should not be misdiagnosed as a displaced patellar fracture. A bipartite fragment typically presents
as a well-corticated fragment in the superolateral aspect of the
patella, and is the result of incomplete fusion of ossification
centers. The incidence of a bipartite patella is approximately
8% and is almost always seen bilaterally.59,60 Radiographs of the
contralateral knee will confirm the diagnosis.
Measures of Patellar Fracture and Extensor
Mechanism Injury Outcomes
No validated outcome measure exists specifically for fractures
of the patella or injuries to the extensor mechanism. Hence,
a plethora of clinical outcome measures have been utilized
to report results of patella fractures over the years. This has
severely limited the ability to compare between studies. The
most commonly reported scale has been that described by
Böstman et al.27 This scale incorporates objective measures such
as range of motion and thigh atrophy while evaluating subjective parameters such as pain and giving way. Catalano et al.34
modified the HSS knee score by excluding evaluation of varus
and valgus instability to report outcomes of open patella fractures. A modified form of the Cincinnati Rating System, incorporating a subjective component as well as objective physical
examination and radiographic assessments, was first employed
by Saltzman and subsequently utilized by others.61 Validated
knee scores such as the Lysholm, the Knee Osteoarthritis Outcome Score (KOOS), and the Knee Society score, have also been
utilized, however, these scores were not specifically designed
for use in isolated knee extensor mechanism injuries. Design
and validation of an outcome score specific to the pathology and
complaints of injuries to the extensor mechanism is needed and
will improve future research.
Pathoanatomy and Applied
Anatomy Relating to Patella
Fractures
Osseous Anatomy of the Patella
The patella is the largest sesamoid in the body, lying deep to
the fascia lata within the tendon fibers of the rectus femoris.
Its proximal margin is termed the basis, and the rounded inferior margin, the apex. Ossification centers typically appear at
2 to 3 years of age. While its shape can vary considerably, the
patella is typically ovoid and flat anteriorly on its nonarticular
surface.31
The proximal three-fourths of the patella is covered with
thick articular cartilage, while the distal pole is entirely devoid
of articular cartilage. For this reason, most distal pole fractures
are extra-articular. The articular cartilage can be 1 cm or greater
in thickness in a normal patella.62 The proximal articular region
is divided into medial and lateral facets by a longitudinal ridge.
A second, vertical ridge along the medial border of the patella
defines a small medial region termed the odd facet.62 Small,
transverse ridges further subdivide the medial and lateral facets into superior, intermediate, and inferior facets. While the
[AU8]
lateral facet is usually the largest, considerable variation in the
size and shape of patellar facets has been observed. Wiberg63
classified patellar osteology into three major groups based on
the size of the medial and lateral facets.
• Type I: Medial and lateral facets are both concave and
approximately equal in size
• Type II: The medial, concave facet is smaller than the lateral
facet
• Type III: The medial, convex facet is smaller than the lateral
facet
Varying degrees of medial facet dysplasia were further
defined by Baumgartl64 Type II and III patellas have a small,
flat medial facet, while Type IV patellas have a small, steeply
sloped medial facet with a medial ridge. Type V, termed the
Jaegerhut patella, is devoid of a medial facet or vertical ridge.64
Arterial Blood Supply in the Patella
The patella is nourished by an extensive, dorsal plexus of blood
vessels that can be separated into both an extraosseous and an
intraosseous vascular system (Fig. 54-5). Six separate arteries
contribute to this vascular plexus, and help to preserve fragment vascularity even in the setting of comminuted fracture
patterns.65,66 The supreme geniculate artery arises from the
S
LS
MS
LI
MI
ATR
Quadriceps tendon
Midpatella
Inferior pole
Figure 54-5 Arterial blood supply of the patella. A: Extraosseous
geniculate arterial system. S, supreme geniculate; MS, medial superior geniculate; MI, medial inferior geniculate; ATR, anterior tibial
recurrent; LI, lateral inferior geniculate; LS, lateral superior geniculate. B: Intraosseous arterial supply.
superficial femoral artery at the level of Hunter canal, while the
four geniculate arteries take origin from the popliteal artery. The
recurrent anterior tibial artery is a branch of the anterior tibial
artery, taking origin approximately 1 cm below the proximal
tibiofibular joint. The superior portion of the plexus lies dorsal to the quadriceps tendon, while the inferior aspect passes
deep to the patellar tendon in the fat pad. Scapinelli65 has shown
that the primary intraosseous blood supply of the patella enters
through the middle third of the anterior body and the distal
pole, and perfuses in a distal to proximal fashion. This pattern
of retrograde perfusion is important in understanding the risk of
osteonecrosis after patellar fracture.
The patellar tendon is nourished by deep vessels in the fat
pad receiving contributions from the inferior medial and lateral
geniculate arteries. The superficial surface of the tendon is supplied by retinacular vessels that arise from the inferior medial
geniculate and recurrent tibial arteries.66
Soft Tissue Anatomy of the Patella
The patella is firmly invested within the quadriceps tendon
deep to the fascia lata. The extensor mechanism, however, collectively refers to the quadriceps tendon, medial and lateral
retinacula, patella, and patellar tendon.
The quadriceps muscle complex is composed of the vastus
lateralis, vastus medialis, rectus femoris, and vastus intermedius. The vastus lateralis originates from the femur and inserts
on the patella at an approximately 30-degree angle relative
to the longitudinal axis of the femur. Its most medial fibers
insert on the superolateral patella, and its most lateral fibers
run lateral to the patella to insert into the lateral retinaculum
and the iliotibial tract.46,62 The vastus medialis consists of two
distinct portions separated by fascia and innervated by distinct
branches of the femoral nerve.46,62 The vastus medialis longus
inserts on the patella proximally at an angle of 15 to 18 degrees
relative to the long axis of the femur, while the vastus medialis
obliquus (VMO) inserts more distally on the patella at an angle
of 50 to 55 degrees.46,62 The rectus femoris is a long, fusiform
muscle that lies central and superficial in the quadriceps complex. The fibers run 7 to 10 degrees medially relative to the
long axis of the femur in the coronal plane. The vastus intermedius lies deep to the rectus femoris and inserts directly into
the superior base of the patella.46,62
The anatomy of the quadriceps tendon has been variably
described. Previous studies have reported a trilaminar organization, with the rectus femoris tendon superficial, the vastus
medialis and lateralis tendons in the middle, and the vastus
intermedius fibers deep.46 In reality, however, the insertion
reflects an intricate blending of all tendon fibers at the insertion
into the superior patella.62
The patellar retinaculum and iliotibial band function as secondary extensors of the knee. The retinaculum is formed by the
continuation of the deep investing fascia lata in the thigh, and
reinforced by inserting aponeurotic fibers from both the vastus
medialis and lateralis. Both the medial and lateral retinacula
insert directly into the proximal tibia, and can thereby provide active knee extension in the setting of an isolated patellar
fracture.31
The medial patellofemoral ligament is an extracapsular
continuation of the deep retinacular surface of the VMO that
extends from the superior medial border of the patella and
attaches to bone just anterior to the medial collateral ligament
on the medial epicondyle.67,68 The medial patellofemoral ligament is accepted to be the major restraint to lateral patellar displacement and contributes 50% to 60% of the total restraining
force of the medial patellar stabilizers.67,68 It has a fan-shaped
configuration that runs from the upper medial margin of the
patella to a femoral insertion posterosuperior to the epicondyle
and just distal to the adductor tubercle. Cadaveric dissections
have revealed the ligament to be 58.8 ± 4.7 mm in length, 12 ±
3.1 mm in width, and inclined 15.9 ± 5.6 degree proximally.68
The patellar tendon originates from the apex of the patella
proximally and inserts into the tibial tubercle distally. Its average length is 5 cm. The patellar tendon is formed primarily from
a continuation of the central fibers of the rectus femoris tendon.
The tendon is reinforced medially and laterally by the extensor
retinaculum and the iliotibial tract as it inserts into the tibia.62
Biomechanics of the
Extensor Mechanism
The extensor mechanism is biomechanically responsible for
active knee extension and the ability to maintain an erect position. Numerous activities of daily living, including walking,
ascending stairs, or rising from a chair depend on the extensor
mechanism to generate sufficient force to overcome gravity.69,70
The patella provides the critical biomechanical functions
of both linking and displacement.69 During initial knee extension from a fully flexed position, the patella functions as a link
between the quadriceps and the patellar tendon. In this capacity, it allows for transmission of torque generated by the quadriceps muscle to the proximal tibia. For young men, these forces
can exceed 6,000 N and can approach up to eight times body
weight.71 At 135 degrees of flexion, linking occurs via transmission of forces between the extensive contact area of the trochlea
with the patellar facets and the posterior surface of the quadriceps tendon.72 From 135 to 45 degrees of flexion, the odd
facet engages the femur. The odd facet is the only portion of
the patella that articulates with the tibial surface of the medial
femoral condyle but not the trochlea.72 Albanese et al.73 studied
knee extension mechanics after subtotal excision of the patella
The quadriceps force as a function of knee flexion angle was
recorded for varying amounts of excision and compared with
the results for total patellectomy.73 Excision of the proximal onehalf or less resulted in lower force requirements when compared
with total patellectomy. The effects of distal to proximal excisions indicate a biomechanical advantage to maintaining a fragment equal to at least three-fourths the length of the proximal
patella.73
The displacement function of the patella is most critical from
45 degrees of flexion to terminal extension. Twice as much
torque is required to extend the knee the final 15 degrees as is
necessary to bring it from a fully flexed position to 15 degrees.46
The patella displaces the tendon away from the center of rotation of the knee, increasing the moment arm and providing a
mechanical advantage that increases the force of knee extension
by as much as 50% depending on the angle of knee flexion.69
It is this displacement action of the patella that provides the
additional 60% of torque necessary to gain the last 15 degrees
of terminal extension.
The high torques generated by the extensor mechanism can
result in substantial patellofemoral contact forces. Compressive forces as large as three to seven times body weight have
been recorded during squatting or climbing stairs.74,75 Given
the small contact area of the patellofemoral articulation, it has
been estimated that the contact stresses generated are greater
than in any other weight-bearing joint in the body.75
The patellofemoral contact zones are dynamic and shift
with varying degrees of knee flexion. The patella engages the
trochlear sulcus at approximately 20 degrees of flexion. With
increasing knee flexion, a horizontal band of contact area across
the patellar facets moves proximally and reaches a maximum at
90 degrees of flexion. Beyond 90 degrees, the contact area on
the patella shifts into two discrete locations on the medial and
lateral facets. Corresponding with the proximal shift of contact
on the patella, the contact zone on the femur shifts distally on
the trochlea and separates into two discrete zones on the medial
and lateral condyles with hyperflexion.72,76
Patellar Fracture
Treatment Options
The management of patellar fractures is largely based on the
fracture classification and findings on physical examination,
with particular attention on the integrity of the extensor mechanism. Age, bone quality, patient expectation, and the presence
of associated injuries may also influence surgical decision making. Regardless of the treatment strategy, the goals of surgical
intervention are:
• Maximal preservation of the patella to maintain its linking
and displacement functions
• Restoration of the articular congruity of the patella
• Preservation of the functional integrity and strength of the
extensor mechanism
Currently, the main treatment options for patellar fractures
are:
• Nonoperative management
• Open reduction and internal fixation, most commonly with
a tension band wiring or cannulated screw tension band
construct
• Partial patellectomy
• Complete patellectomy
Nonoperative Treatment of Patellar
Fractures
Indications and Contraindications
Nonoperative treatment may be indicated for patellar fractures
with <3 mm of fragment displacement or <2 mm of articular
incongruity in which the extensor mechanism remains intact
Indications
Contraindications
rospective series of delayed union or nonunion of patella fractures and found that minimally symptomatic nonunions could
be successfully managed conservatively. In addition, Nathan
et al.80 showed that in a low-demand patient, patellar nonunion
may be successfully managed nonoperatively despite the inability to achieve radiographic union with nonoperative care.
Intact extensor mechanism
Extensor lag or incompetent
extensor mechanism
Operative Treatment of Patellar Fractures
<2 mm articular incongruity
>2 mm articular incongruity
<3 mm fracture displacement
>3 mm fracture displacement
Severe medical comorbidity
Open fracture
Severe osteopenia
Loose bone or chondral
fragments
Table 54-1
onoperative Indication and
N
Contraindications
Patellar Fractures—Nonoperative Treatment
(Table 54-1). Almost any fracture pattern (transverse, stellate,
or vertical) may be addressed with closed treatment if the above
criteria are satisfied. Relative indications for nonoperative management, sometimes even in circumstances of greater fragment
displacement, include medical conditions that are contraindications to anesthesia and elderly, debilitated patients with severe
osteopenia that precludes the ability to achieve rigid internal
fixation.
Techniques
Acute nonoperative treatment typically consists of 4 to 6 weeks
of extension splinting or bracing. If patient compliance and reliability are a concern, however, long leg cylinder casting may be
preferable with careful molding about the knee and above the
ankle to help prevent displacement of the cast as edema resolves.
Straight-leg raises and isometric quadriceps exercises are initiated
early in the cast or brace to minimize atrophy. Range of motion
is gradually initiated after there is evidence of callus formation
and fracture consolidation on plain radiographs. Radiographs are
obtained shorty after range of motion is initiated to evaluate for
displacement. In regard to weight bearing, most modern protocols allow for some degree of early weight bearing in full exten[AU9] sion. Takebe and Hirohata77 recommended early partial weight
bearing in extension, while Boström31 recommended weight
bearing as tolerated with crutches for support.
Outcomes
Nonoperative treatment of minimally displaced fractures has
been reported with good clinical outcomes. In a large series of
422 patellar fractures reported by Boström,31 219 minimally displaced fractures were treated nonoperatively, and 98% had good
to excellent results at final follow-up. Only two failures occurred
with nonoperative treatment. Other series have reported low
failure rates of less than 5% with closed management of minimally displaced fractures.15,62
In a series of 18 patients with significant medical comorbidities and displaced patella fractures, Pritchett78 reported satisfactory outcomes in 12 patients at 2-year follow-up, with 9 of these
12 patients without significant limitations in activities of daily
living. Furthermore, Klassen and Trousdale79 reported on a ret-
Operative treatment is indicated for patellar fractures with
>3 mm of fragment displacement, >2 mm of articular incongruity, osteochondral fractures with associated intra-articular loose
bodies, and/or a compromised extensor mechanism with loss of
active extension. Internal fixation or partial or total patellectomy
with repair of the extensor mechanism are all surgical interventions performed with the goal of achieving stable fixation and
a functional extensor mechanism that allows for early range of
motion and rehabilitation.
Surgical Procedure
Internal Fixation Background. Numerous variations
of internal fixation techniques for patellar fracture stabilization have been described in the literature (Fig. 54-6). The first
description of cerclage wiring for patellar fracture fixation was
made by Berger in 1892.81 Anderson81 discussed the use of
an equatorial circumferential wire placed around the patella,
and Magnuson and Payr82,83 described successful fixation with
wires passed through vertical drill holes. Screw fixation for longitudinal and transverse fracture patterns with large fragments
has also been described.10,26,84 The potential concern of these
fixation strategies, however, has been (i) an inability to initiate
early motion due to the risk of displacement with large tensile
forces from quadriceps contraction, and (ii) lack of compressive forces at the articular surface. The AO/ASIF popularized the
technique of tension band wire fixation for patellar fractures to
address these concerns, based on biomechanical studies demonstrating increased construct strength with wires placed on
the anterior, tension-side cortical surface of the patella.25
Biomechanics of Tension Band and Modified
Tension Band Fixation. The principle of tension band wire
fixation for patellar fractures is to convert the tensile forces
generated from the quadriceps complex at the anterior cortical
surface of the patella into compressive forces at the articular
surface. With progressive knee flexion, the passive tensile forces
in the extensor mechanism in addition to the pressure of the
femoral condyles against the patella increase interfragmentary
compression at the articular surface.
Biomechanical testing has been performed on a variety of
internal fixation constructs. Weber et al., in a cadaver study,
found Magnusson wiring and modified anterior tension banding to perform better than cerclage wiring or standard tension
banding. Their study also demonstrated that repair of the retinaculum increased the strength of the constructs.26 A study by
Benjamin et al.85 compared the strength of four different fixation
strategies (tension band wiring, modified tension band wiring
over Kirschner wires [K-wires], Lotke and Ecker longitudinal
Figure 54-6 A–L: Illustrations of patellar
fracture fixation constructs.
A
B
C
D
E
F
G
H
I
J
K
L
anterior banding, and circumferential cerclage wiring) in a
transverse patellar fracture and retinacular disruption model.
Cerclage wiring provided the weakest fixation strength with
up to 20 mm of gapping at the fracture site with tensile stress.
The modified anterior tension band technique of transosseous
K-wire fixation with anterior banding demonstrated superior
strength to all other constructs.85 John et al.86 found that utilizing a horizontal figure-of-eight with four strands crossing the
fracture rather than the more common vertical tension band
improved interfragmentary compression. Isolated screw fixation
with 3.5-mm or 4.5-mm screws may be sufficient, particularly
in the setting of simple transverse or longitudinal fractures in
patients with good bone stock. Burvant et al.87 investigated tension banding with screws and found them to perform biomechanically superior to five other techniques of transverse patellar
fracture fixation, including screw fixation alone, however, placing tension band wires around the screw tips and heads are
often difficult in the clinical setting. Carpenter et al.88 compared
a modified tension band, parallel 4.5-mm interfragmentary lag
screws, and 4-mm cannulated lag screws augmented with a tension band passed through them in a transverse patellar fracture cadaver model. The highest load-to-failure was seen with
the modified tension band and the cannulated lag screw technique.88 Regardless of which tension band construct is selected,
Baran et al.89 used MRI in a knee cadaveric model to advocate
for placement of the tension band wire as close to the bone as
possible with minimal interposing tendinous tissue.
Due to the frequent soft tissue irritation from stainless steel
wire as well as its difficult handing properties, alternative such
as braided cable or suture has been investigated. Scilaris et al.90
compared anterior tension banding with 1-mm wire versus
1-mm braided cable. The braided cable allowed for less fragment displacement with cyclical loading. In addition, tightening of the wire by twisting at two different sites compared to a
single site has been shown to provide greater interfragmentary
compression.91 John et al.86 demonstrated improved stability
with cyclic loading if wire twists were placed at the corners of
the figure-of-eight loop.
McGreal et al.92 demonstrated that braided polyester suture
was 75% as strong as wire and performed equivalent to cerclage
wire with cyclical loading. Braided No. 5 Ethibond has also
been shown to be comparable to wire fixation with anterior
tension banding or Lotke and Ecker anterior longitudinal banding procedures for displaced, transverse fractures.93 Wright
et al. investigated the properties of FiberWire, a reinforced
braided polyblend suture, in comparison to stainless steel wire
for tension band fixation in a patellar fracture model. Double
strand FiberWire was found to have a significantly higher loadto-failure than stainless steel wire.94
Small clinical series have reported favorable outcomes with
alternatives to stainless steel cable. Chen et al.95 demonstrated
equivalent clinical outcomes with wire versus biodegradable
tension band fixation of patellar fractures at a mean of 2-year
follow-up. Gosal et al.96 found a reduced reoperation rate for
fractures treated with a modified anterior tension band utilizing
braided polyester suture compared to stainless steel wire.
Preoperative Planning. When planning for internal fixation of a patellar fracture, it is important to have a good understanding of the fracture pattern and the location of fragments
(Table 54-2). Scrutinizing the injury radiographs often provides
enough information about the fracture to formulate a detailed
plan for location of the fixation construct as well as the order of
reduction and insertion of internal fixation. Often, the fracture
will consist of more than two fragments or the fragments will be
oriented in an oblique direction. In these cases, the “textbook”
descriptions of tension band constructs may need to be customized or combined with other techniques to fit the unique
Table 54-2
reoperative Checklist Operative
P
Treatment of Patellar Fractures
• OR table
• Radiolucent OR table
• Position/positioning aids
• Supine positioning
• Often a small bump under the hip is helpful in controlling
external rotation of the limb
• A small towel bump that can be moved below the knee for
slight flexion or under the ankle for knee extension is useful
• Fluoroscopy location
• Positioned perpendicular to the extremity on contralateral
side of bed
• Equipment
• Small and large pointed reduction clamps
• K-wires
• 18-gauge wire or heavy braided nonabsorbable suture
• 3.5, 4, or 4.5 cannulated screws
• Mini-fragment screws
• Suture passer
• Dental pick
• Power drill
• Tourniquet
• Nonsterile if desired
fracture pattern. Consideration should be given to “simplifying”
the fracture pattern, which involves reducing and fixing minor
fragments to create a fracture pattern that is amenable to an
anterior tension band construct. Lag screws, K-wires, and bioabsorbable pins all may be utilized to hold smaller fragments
together and their need should be anticipated preoperatively.
Positioning. The patient is positioned supine on a radiolucent operating table. A small bump under the hip is useful
for controlling external rotation of the limb. In addition, a small
bump of towels that can be moved from beneath the knee and
ankle and vice versa, helps in providing slight knee flexion and
extension, respectively, during the case. A tourniquet is rarely
needed; however, one may be placed in nonsterile fashion and
only inflated if uncontrollable bleeding is encountered.
Surgical Approaches. Numerous skin incisions have
been utilized for the treatment of patellar fractures. However,
a midline longitudinal extensile skin incision centered over the
patella is most often recommended. This incision allows for
extension both proximally and distally in the acute and revision
fracture setting and provides the most versatility for future knee
procedures, especially knee arthroplasty. After incising skin and
subcutaneous tissues, the articular surface is typically exposed
by either working through the fracture site or retinacular rents.
The medial and lateral retinacular rents may be extended if
needed to allow finger access to the articular surface. If the
retinaculum is not damaged or visual exposure of the articular
surface is desired, Gardner et al.97 developed a technique for
exposure and fixation of comminuted patellar fractures using a
lateral arthrotomy and inversion of the patella. This approach
provides direct visualization for articular reduction.
Modified Tension Band with Vertical Figure-ofeight Wire Technique. The patient is positioned supine
on a radiolucent table (Table 54-3, Fig. 54-6C). A longitudinal
midline incision is typically performed except in the case of an
open fracture or a traumatic arthrotomy in which the laceration
may be incorporated into the incision if possible. Superficial
Table 54-3
odified Anterior Tension
M
Band—Surgical Steps
• Anterior longitudinal midline incision
• Avoid unnecessary undermining of tissue
• Expose fracture and clear of debris
• Assess degree of injury and define fracture pattern
• Simplify fracture pattern with K-wires or screws when able
• Reduce fracture
• Place two 1.6-mm K-wires perpendicularly across fracture,
5 mm below anterior cortical surface
• Pass 18-gauge wire beneath patellar tendon posterior to
K-wires
• Cross limbs of wire over anterior patella
• Pass wire through quadriceps tendon posterior to K-wires
• Tighten wires by twisting both limbs of the wire simultaneously
• Bend ends of K-wires 180 degrees posteriorly
• Impact bent ends of K-wires into patella
dissection should be avoided regardless of incision orientation
to preserve the blood supply and the viability of skin flaps.
After exposure of the fracture lines, all clots and devitalized
debris should be cleared. Prior to any fixation, the degree of
injury should be carefully assessed. The articular surfaces of
the femur and patella should be inspected, and any intraarticular loose bodies flushed out of the joint. In addition, the
integrity of the medial and lateral retinaculum as well as the
proximal and distal soft tissue attachments of the patella must
be evaluated. The fracture pattern should be generally defined.
Complex fracture patterns with moderate comminution may
be simplified with the use of interfragmentary lag screws to create a transverse pattern that is then amenable to tension band
fixation. With the knee slightly flexed, the fracture should be
reduced and maintained with a pointed reduction forceps. The
quality of the articular reduction should be palpated through
the defect in the retinaculum. Occasionally, extension of the
arthrotomy or retinacular tear may be necessary to allow palpation of the articular surface. Gardner et al.97 have developed
a technique for exposure and fixation of comminuted patellar
fractures using a lateral arthrotomy and inversion of the patella.
This allows for direct visualization and reduction of articular
surfaces without soft tissue interposition and allows for confirmation of articular congruity, compared to more traditional
techniques that rely on palpation alone. Intraoperative fluoroscopy with imaging in multiple planes may also be utilized to
confirm an anatomic reduction.
Two parallel 1.6-mm K-wires are placed perpendicularly
across the fracture line to maintain the reduction and anchor
the tension band wire. The K-wires can be placed in an antegrade or retrograde fashion. Using the antegrade technique, the
wires are advanced from proximal to distal at a level 5 mm
below the anterior cortical surface and parallel to it. The wires
are spaced apart to divide the patella longitudinally into thirds.
When using the retrograde technique, the reduction is taken
down and the proximal fracture fragment is flexed 90 degrees
to expose the fracture surface. Starting 5 mm below the anterior
cortical surface and dividing the patella longitudinally into the
thirds, the K-wires are advanced proximally through the fracture site, exiting at the locations of the starting points for the
antegrade technique. The reduction is then re-established and
held with a pointed reduction forceps. The K-wires are subsequently advanced from proximal to distal across the fracture
site until they exit distally at the inferior patellar margin.
Next, the tension band wire is passed and tightened to complete the construct. The limbs of the wire are crossed over the
anterior cortex of the patella and one limb is passed below the
patellar tendon immediately adjacent to its inferior margin as
described above. After anatomic reduction is confirmed with
direct palpation and fluoroscopy, the wire is tensioned with
slow twisting of the wire limbs. Twisting is performed at two
locations (one in each wire limb), as tightening at only the
ends of the wire may lead to asymmetric fracture compression
and excess slack on the contralateral side. Care must be taken
to avoid overtensioning of the wires which can result in wire
breakage and loss of reduction or malreduction secondary to
iatrogenic fragment comminution. In addition, tensioning the
Table 54-4
annulated Screw Tension
C
Band—Surgical Steps
• Refer to modified anterior tension band for exposure and
reduction
• Place two cannulated screw guidewires perpendicularly
across fracture 5 mm below anterior cortical surface
• Drill with cannulated drill over guidewires
• Use depth gauge for screw lengths
• Insert screws
• Pass a single 18-gauge wire separately through each
cannulated screw
• Cross limbs of wire over anterior patella
• Tighten wires by twisting both limbs of the wire simultaneously
• Bend wire twists posteriorly into deep soft tissue
wire at the superior portion of the patella places the twists in a
region with more soft tissue which may lessen the rate of soft
tissue irritation. After satisfactory wire tension is achieved, the
K-wires are cut at both ends and bent posteriorly 180 degrees
over the tension band wire both proximally and distally. They
are gently impacted and buried into the patella to prevent
migration. The arthrotomy is copiously irrigated and the retinacular tears and arthrotomy are closed in a water-tight fashion
with interrupted, figure-of-eight nonabsorbable sutures. The
wound is closed in a standard, layered fashion (Table 54-3).
Cannulated Screw Tension Band Technique. The
positioning, exposure, and reduction technique are identical to
that for the modified anterior tension band (Table 54-4, Fig.
54-6I). However, rather than K-wires, 4-mm cannulated screws
are placed across the reduced fracture. This allows for lagged
interfragmentary compression, and has been shown to be biomechanically stronger than the K-wire construct.88 In this technique, guidewires are placed in an identical fashion to K-wires
as described above. This is followed by drilling and cannulated
lag screw advancement across the fracture over the wires. Use a
depth gauge to measure screw lengths. Take care to avoid having
the screw tips protrude from the patellar bone as this can lead
to rapid wire failure. Two individual 18-gauge wires are then
passed; one wire through each cannulated screw. The wires are
then passed anteriorly over the patella in a figure-of-eight fashion and tightened simultaneously to the adjacent wire end after
anatomic reduction of the fracture has been confirmed.98
Longitudinal Anterior Banding and Cerclage
Wiring—The Lotke–Ecker Technique. Stellate fracture
patterns that are not amenable to a modified anterior tension
band technique may be treated with longitudinal anterior banding plus cerclage wire fixation (the Lotke–Ecker technique)
(Fig. 54-6G).13 The positioning, exposure, and reduction technique is identical to that for the modified anterior tension band.
Minimally displaced fractures are fixed in situ, while severely
comminuted and displaced stellate fractures are reduced
through indirect techniques.13 In these cases, a cerclage wire is
first placed around the circumference of the patella immediately
adjacent to the bone with the assistance of a 14- or 16-gauge
angiocatheter or pulled through with a hemostat. Gross manual
reduction is performed without clamps, followed by articular
surface reduction with progressive tightening of the cerclage wire.
Longitudinal anterior banding is then performed by drilling
two parallel tunnels, 1 cm from the medial and lateral edges of
the patella respectively, with a 2-mm drill bit in an antegrade
fashion.13 A large gauge wire (18- to 22-gauge) is then inserted
into both drill holes, preserving a closed loop distally. The
distal loop is brought anteriorly and one free proximal end of
the wire is passed through this anterior loop. The wire is then
secured to its other end and tightened with progressive twisting. This fixation results in a hybrid of anterior tension banding
and intraosseous wire fixation.13
Postoperative Care. No specific postoperative protocols
have been scientifically evaluated, however, most recent authors
have recommended early knee range of motion and protected
weight bearing. Prolonged immobilization in the presence
of stable fracture fixation has generally been discouraged.26,98
In addition, postoperative continuous passive motion (CPM)
has been suggested to help reduce postoperative stiffness and
improve articular cartilage healing.74
Potential Pitfalls and Preventative Measures. There
are numerous potential pitfalls that can be encountered during
internal fixation of patellar fractures (Table 54-5). The limited
anterior soft tissue over the knee and its frequent injury from
a direct blow makes it important to avoid elevating unnecessary subcutaneous flaps. This will minimize soft tissue healing
problems and hematoma formation.
Table 54-5
otential Pitfalls and Preventions
P
for Internal Fixation
• Pitfall #1 – Wound breakdown
• Prevention – Avoid creating subcutaneous flaps
• Pitfall #2 – Intraoperative loss of reduction
• Prevention – Avoid overtightening of tension band wires
• Pitfall #3 – Early tension band wire failure
• Prevention – Avoid protrusion of cannulated screw tips from
patella
• Pitfall #4 – Malreduction
• Prevention – Do not rely solely on fluoroscopy to assess
reduction, use palpation through retinacular rent, or visually
assess articular reduction with lateral parapatellar arthrotomy
and patellar eversion if needed
• Pitfall #5 – Asymmetric wire tension
• Prevention – Simultaneously tension wire from two places to
provide equal tension
• Pitfall #6 – K-wire migration
• Prevention – Bend K-wire ends 180 degrees posteriorly and
impact into patella
• Pitfall #7 – Prominent Hardware
• Prevention – Tension wire at superior aspect of construct to
provide more soft tissue coverage for twists, and bend wire
twists posteriorly into deeper soft tissue, or consider braided
nonabsorbable suture as an alternative
• Pitfall #8 – Intra-articular screw or K-wire penetration
• Prevention – Drill wires retrograde through the fracture site to
avoid articular penetration
Another common pitfall results from soft tissue irritation
from prominent hardware. Bending K-wires posteriorly and
impacting them into the patella to prevent migration and placing wire twists superiorly where more abundant soft tissue exists
may help avoid soft tissue irritation. Alternatively, braided nonabsorbable suture can be used rather than stainless steel wire
for a tension band.
Avoid hardware failure by tensioning the tension band wire
in two places to apply equivalent tension to both sides of the
construct. Moreover, do not overtension the wires as this may
lead to articular gapping or wire failure. Lastly, avoidance of
prominent cannulated screw tips will prevent rapid wire breakage as the wires are tensioned over the edge of the patella rather
than the sharp screw tips when this method is used.
Treatment Specific Outcomes. The lack of a uniform
surgical technique or a standardized assessment scale limits the utility of reported outcomes after operative fixation of
patellar fractures. As a result, the literature provides generalizations about “good” or “excellent” outcomes based on subjective patient complaints of pain, loss or motion, or limitations
in daily activities. Moreover, these subjective results may not
correlate with articular damage. Haklar et al.99 found Grade II
or III cartilage irregularities of the patella and/or trochlea in 73%
of patients who underwent arthroscopy at the time of anterior
tension band hardware removal despite all patients in the series
having good to excellent Lysholm Knee Scores at follow-up.
The authors felt these findings may predict future symptomatic
patellofemoral arthritis. Despite the likely presence of articular irregularities, the combined results of many small series for
open reduction and internal fixation have produced a good to
excellent result in most cases (Table 54-6). The results of operative repair of patella fractures need to be interpreted with some
caution; however, as series are more often reported by repair
construct rather than fracture pattern. Modified anterior tension
band wiring has produced the best results, with 86% good to
excellent outcomes reported.9108 Böstman et al.28 reported significantly better results with anterior tension banding compared to
cerclage wiring, partial patellectomy, or interfragmentary screw
fixation. While small series have reported excellent outcomes
with cerclage wiring, a review of the combined results reveals
inferior performance to tension band wire fixation, with only
70% good to excellent results. However, a more recent report by
Yang et al.104 reported 100% good to excellent results in 21 comminuted patellar fractures treated with braided titanium cerclage
cable. The anterior longitudinal banding technique of Lotke and
Ecker13 can also be effective, with 81% excellent results reported
in their small series. Results of cannulated screw tension band
constructs are still emerging. This technique is now commonly
employed and early series demonstrate favorable results with
96% good to excellent outcomes (Fig. 54-7).
Minimally Invasive and Arthroscopic-assisted
Fixation. The use of arthroscopy to assist with patellar fracture
reduction and fixation has been described. Appel and Siegel109
presented a series of cases with arthroscopic-assisted reduction of displaced patellar fractures followed by percutaneous
screw and wire fixation with satisfactory outcomes. Theoretical
[Au:
9108
Reference
not in
list pls.
check]
Table 54-6
Outcomes after Internal Fixation of Patella Fractures
Author/Year
6
Patients
Technique
Outcomes (Excellent or Good Results)
Seligo 1971
35
Cerclage
80%
Nummi51 1971
112
Tension band wire/cerclage
32%; 11% complications; 18 cases of
bone necrosis after cerclage
Boström31 1972
75
Stainless steel wire through
longitudinal drill holes
81%
Böstman et al.28 1983
48
79%
Ma100 1984
107
Percutaneous suture
91%
Levack et al.101 1985
30
63%
Catalano34 1995
76 open fractures
Open reduction internal fixation
77%; 4% fixation failure; no deep infection
Torchia and Lewallen102
1996
44 open fractures
Open reduction internal fixation 50%
Partial patellectomy 50%
77%
10.7% deep infection
Smith et al.103 1997
51
Modified tension band wire
Loss of reduction >2 mm in 22%
10 transverse
fractures
Parallel screws/tension band wire
70%
98
Berg 1997
Yang et al.104 2010
21
Cerclage (titanium braided cable)
100%
Qi et al.105 2011
15
Bioabsorbable parallel screws/
absorbable tension band suture
100%
Tian et al.106 2011
101
51% tension band wire
49% Parallel screws/tension band
cable
87% tension band wire
100% parallel screws/tension band cable
Chang and Ji107 2011
10 (inferior pole
fractures)
Parallel screws/tension band wire
100%
advantages include direct visualization of the articular surface during internal fixation, limited dissection and soft tissue
stripping, and the ability to address associated intra-articular
pathology in the knee including osteochondral fractures. Concerns include fluid extravasation and a limited ability to repair
the retinacular tissues. While this technique may have a role in
selected cases, we do not feel that it supplants open techniques
which allow for anatomic fracture reduction, rigid fixation, and
retinacular and extensor mechanism repair.
Pizarro et al.110 recently presented a randomized series of
53 patients treated with percutaneous patellar osteosynthesis
(PPOS) versus standard open reduction and internal fixation
for closed, displaced transverse patellar fractures. In the PPOS
group, a special device was secured via four percutaneous portals in order to maintain the reduction while an anterior tension
band was placed. In the group of patients treated with PPOS,
the authors reported shorter surgical times, less pain, less complications, and improved functional outcome scores by the Knee
Society Clinical Rating Scale (KSCRS) at 1-year follow-up. Clinical outcome scores were not statistically different between the
two groups by 2-year follow-up.110
Partial Patellectomy
Biomechanical Background. As mentioned previously,
by elevating the extensor mechanism and increasing the lever
arm, the patella increases the force of knee extension by as
much as 50% depending on the angle of knee flexion.69 In addition, Albanese et al.73 demonstrated lower force requirements
for knee extension with increasing amounts of retained patella.
Thus, preserving any portion of the patella likely improves
knee extensor function.
While the value of retaining maximal patellar length and height
is rarely debated, the location of drill holes for tendon reattachment after partial patellectomy has been controversial. Studies
have suggested that the holes be placed near the articular surface
to avoid abnormal tilting of the patella and increased patellofemoral contact forces.111 In 1958, Duthie and Hutchinson111 reported
tilting of the patella in five of seven patients with postoperative
arthritis, and attributed these changes to malalignment from
attachment of the patellar tendon to the anterior cortex. In contrast, Marder et al.112 completed contact pressure studies demonstrating improved mechanics with anterior tendon reattachment
for 20% and 40% partial patellectomy models. Furthermore,
Zhao et al.113 have reported an increase in the force required to
extend the knee with tendon attachment to the articular surface
compared to the anterior cortex. With these conflicting results,
further investigation is warranted.
Indications and Contraindications. Partial patellectomy may
be indicated when comminution of the distal pole or a fragment of the patella is extensive and cannot be stabilized with
internal fixation. In addition, fragments that are dysvascular or
free with limited soft tissue attachments and likely to become
loose bodies within the knee joint should be removed. Partial
patellectomy should be avoided when the entire patella is salvageable or a tendon repair can be performed without removal
of bony fragments.
A
B
C
Figure 54-7 Modified tension band wiring through
cannulated screws. Lateral view (A) of injury. AP
(B) and lateral (C) view of internal fixation.
Surgical Procedure
Preoperative Planning. Most frequently the final decision
to perform partial patellectomy is made during the surgical
procedure, however, operative planning should prepare for the
possibility of partial patellectomy. Heavy braided nonabsorbable suture, suture passers, and mini-fragment fixation should
be available.
Positioning. Refer to the positioning description for internal fixation.
Surgical Approach. The surgical approach is the same as for
open reduction and consists of a longitudinal midline exposure.
[AU10]
Technique. Care is taken to preserve as many large, viable
fragments as possible (Table 54-7). Retained fragments are
anatomically reduced and secured to one another with screws
or K-wires. If the comminution primarily involves the central
patella with preserved proximal and distal fragments, the central
Table 54-7
Partial Patellectomy—Surgical
Steps
• Expose fracture
• Assess degree of injury and determine which fragments are
salvageable
• Remove nonviable patellar fragments
• Reduce and internally fix retained fragments
• Place grasping stitch in tendon
• Reattach patellar or quadriceps tendon through three parallel
drill holes
• Secure suture over bone bridges in full extension
• Assess strength of repair with controlled flexion
• Consider adding cerclage wire from quadriceps tendon to
tibial tubercle
• Perform multilayer closure
comminution can be excised and the remaining fragments
secured as congruously as possible with screw fixation.
With severe inferior pole comminution, resection of fragments with patellar tendon reattachment can be performed. Most
of these fractures are extra-articular, as the distal pole is devoid of
articular cartilage. Three longitudinal drill holes are then placed
through the remaining patella to serve as tunnels for suture passage. A tendon-grasping, woven or locking nonabsorbable suture
(such as a Krackow suture) is placed in the patellar tendon, and
the sutures are passed with a ligature passer through the tunnels
and firmly tied over bone bridges with the knee in hyperextension. Tantamount to the tendon repair, however, is a meticulous
repair of the associated medial and lateral retinacular injury.26
Based on the energy of the injury and strength of the repair, the
construct may be protected with a cerclage wire, a tendon graft,
or a Mersilene tape that is passed immediately proximal to the
superior pole of the patella and inferiorly through the proximal
tibia posterior to the tibial tubercle. The cerclage should be tightened with the knee flexed to 90 degrees, as tightening in extension may constrain the postoperative flexion that is achievable by
the patient. The strength of the repair should always be evaluated
intraoperatively, with the surgeon observing for interfragmentary motion and the integrity of the tendon–bone interface with
progressive knee flexion. Rigid constructs may allow for early,
controlled motion of the knee.
Postoperative Care. An extension brace is applied and
partial weight bearing with crutch assistance is maintained for
6 weeks postoperatively. Gradual active and active-assisted
range of motion is implemented at 6 weeks from surgery. If the
surgeon obtains excellent fixation, early gradual range of motion
in a hinged brace, not to exceed 90 degrees, may begin prior to
6 weeks from injury.
Distal Pole Osteosynthesis—Basket Plate. Traditionally,
comminuted fractures of the distal pole have been managed
with partial patellectomy with satisfactory outcomes. Recently,
a technique for osteosynthesis of these fractures using a novel
basket plate device has been described.114–117 The basket plate
is contoured to fit the geometry of the patellar apex and is augmented with several anterior and posterior flanges to collect the
comminuted fragments. Fibers of the proximal patellar tendon
are spread apart by the flanges to allow positioning at the inferior
pole without detachment. Four holes are provided to place parallel and oblique screws that engage the proximal fragment and
resist both tensile and shear forces.115,116 Biomechanical studies
have demonstrated an ultimate load-to-failure of approximately
420 N for this construct, approximately 70% higher than that of
a separate vertical wiring fixation construct.115,118
Preliminary clinical outcomes with the basket plate osteosynthesis technique have been favorable. Matejcic et al.116 reported
90% good to excellent outcomes at a mean 5-year follow-up for
51 patients who underwent basket plate osteosynthesis of comminuted distal pole fractures. These data must be approached
with caution, however, as 61% of the included patients were
lost to follow-up.116 A retrospective cohort study by Kastelec
and Veselko114 compared 11 patients who had internal fixation of a distal pole avulsion fracture to 13 patients who had
Table 54-8
utcomes after Partial
O
Patellectomy
Author/Year
Number of
Patients
Seligo6 1971
3
51
Nummi 1971
112
Outcomes (Excellent or
Good Results)
33%
62%; shortest period of
disability compared to
open reduction internal
fixation or total patellectomy
Mishra119 1972
4
75%
Boström31 1972
28
82%
Saltzman61 1990
40
78%
Quad strength 85%
uninjured side
Hung et al.120 1993
56
20% symptoms with
kneeling/squatting
>50% arthritis
a pole resection. At an average follow-up of 4.6 years, average
patellofemoral scores were significantly better in the osteosynthesis compared to the resection group.114 Furthermore, there
was a significantly greater incidence of patella baja in the pole
resection group as assessed radiographically by the method of
Kastelec and Veselko.114 Sample sizes were small, however, and
randomized control trials are necessary to further define potential advantages of osteosynthesis compared to resection in the
surgical management of comminuted distal pole fractures.
Treatment Specific Outcomes. When appropriate selec- [AU11]
tion criteria are utilized, partial patellectomy can yield functional
outcomes that are equivalent to open reduction and internal
fixation (Table 54-8).6,28,31,51,61,119 Multiple authors have reported
nearly normal functional outcome when large fragments of the
patella and articular congruity are preserved. Retention of small,
nonviable fracture fragments or those devoid of cartilage did not
improve function, while retention of large fragments provided a
lever arm for improved extensor mechanism function. Combined
results in 138 cases have shown good to excellent outcomes in
72% of cases. With extensive inferior pole comminution, superior results have been reported with partial patellectomy compared to internal fixation.31 Boström31 reported 88% good to
excellent results with partial patellectomy for transverse patellar
fractures with inferior pole comminution, compared to only 74%
good to excellent results with internal fixation.
Total Patellectomy
Indications and Contraindications. Total patellectomy
is occasionally performed for highly displaced, comminuted fractures in which stable fixation cannot be achieved and when no
large fragments can be retained (Table 54-9). We have reserved
this as a salvage procedure in the rare setting of failed internal
fixation or patellar osteomyelitis. Retention of even a single fragment is usually possible, and can substantially help to preserve
the biomechanical function of the extensor mechanism.73
Table 54-9
otal Patellectomy Indications
T
and Contraindications
Total Patellectomy
Indications
Contraindications
Severely comminuted fractures
unable to accept internal fixation or suture repair
Ability to retain any portion
of the patella
Failed internal fixation
Patellar osteomyelitis
Surgical Procedure
Preoperative Planning. Often the final decision to perform
total patellectomy is made during the surgical procedure, however, operative planning should prepare for the possibility of
total patellectomy. Heavy braided nonabsorbable suture should
be available.
Positioning. Refer to positioning for the modified anterior
tension band.
Surgical Approach. Refer to approach for the modified
anterior tension band.
Total Patellectomy Surgical Technique. If a total patellectomy is required, all bony fragments are removed, with care
being taken to preserve the retinacula and restore the integrity of the extensor mechanism (Table 54-10). Removal of the
patella effectively lengthens the extensor mechanism, such that
end-to-end repair will result in an increased slack distance
and extension lag after surgery. This is avoided by imbrication
or use of a purse-string suturing technique that shortens the
tendinous repair. Tension should be evident on the repair at
90 degrees of flexion when length has been adequately restored.
For additional extensor mechanism strength, the VMO can be
isolated and advanced according to the technique described by
Gosal et al.96 Since the VMO is separately innervated and does
not normally contribute to knee extension, distal and lateral
advancement of the VMO tendon over the patellectomy repair
has been shown to result in increased quadriceps strength and
improved outcomes.
Table 54-10
Total Patellectomy—Surgical
Steps
• Expose fracture
• Assess degree of injury and determine if patellar salvage is
possible
• Remove patellar fragments
• Imbricate redundant extensor mechanism tissue with heavy
braided nonabsorbable suture
• Check extensor mechanism tension at 90 degrees of flexion
• Advance VMO
Techniques for Extensor Mechanism Deficiency. In
certain situations, there may be an inadequate amount of soft
tissue available for primary repair of the extensor mechanism.
In general, the absence of prepatellar soft tissues is addressed
with quadriceps turndown procedures. Absence of the quadriceps tendon, however, usually requires fascia or tendon weaving procedures.
Shorbe and Dobson121 described the inverted V-plasty quadriceps turndown procedure. The quadriceps tendon is exposed
for approximately 3 in, and a full-thickness V-shaped incision
is made into the tendon with the apex of the “V” located 2.5 in
proximal to the former superior pole of the patella. The V-limbs
extend distally for 2 in, creating a base that preserves approximately ½ in of tendon that is continuous with the retinaculum
on both the medial and lateral sides. The V-flap is folded inferiorly, inserting it through the proximal patellar tendon and
suturing it in place with several interrupted sutures. The quadriceps tendon defect is then closed in a side-to-side fashion
with multiple interrupted sutures.
If the quadriceps tendon is deficient, Gallie and Lemesurier122 have described a free fascia or tendon weave procedure.
After nonviable tendon remnants have been debrided, the
length of the defect is measured with the knee in full extension.
This length is doubled and 2 in added to harvest the appropriate size fascial graft. Through a separate lateral incision, a
1.5-cm wide graft of fascia lata or iliotibial band of appropriate
length is harvested and tubularized along its long axis. Alternatively, allograft tissue of appropriate length can be utilized.
The graft is then woven through the quadriceps tendon and/or
muscle, passed through the patellar tendon, and sewn back on
itself. Tension should be evident on the repair at 90 degrees of
flexion when length has been adequately restored. Excess tissue
is excised and all edges firmly sutured down.
Potential Pitfalls and Preventive Measures. The most
important pitfall is performing total patellectomy in a case in
which a portion of the patella can be salvaged. Careful assessment of the fracture at the time of surgery will most often reveal
a portion of the patella that can be retained and total patellectomy avoided. When total patellectomy is performed, extensor
lag is one of the most common complication. As the patella is
removed, the extensor mechanism is effectively lengthened, thus
imbricating sufficient redundant tissue so that the repair under
tension at 90 degrees of flexion will limit this complication.
Treatment Specific Outcomes. The outcomes of total
patellectomy are generally inferior to those reported after internal fixation or partial patellectomy for fracture. However, these
results are difficult to interpret as fractures treated with total
patellectomy likely reflect higher-energy, comminuted injuries.
Before the introduction of anterior tension band techniques,
poor methods of achieving rigid internal fixation may have justified total patellectomy in these early series. Recent studies,
however, have reported a higher rate of fair-to-poor outcomes
with total patellectomy (Table 54-11). Böstman et al.27 recommended total patellectomy only in the setting of severely comminuted fractures. Sutton et al.123 evaluated quadriceps strength
and functional abilities in patients who had undergone partial
Table 54-11
Outcomes after Total Patellectomy
Author/Year
Number of Patients
Follow-up
(yrs) Mean
Outcome (Excellent or Good Results)
Seligo6 1971
44
NR
89%
Nummi 1971
24
1–8
38%
Boström31 1972
5
8
20%
Mishra119 1972
26
4
69%
Einola11 1976
28
7.4
21%
Quad atrophy and weakness common; only 25% had strength
≥75% of normal side
Sutton123 1976
33
5.3
Complete patellectomy associated with reduction in stancephase flexion during walking and stairs; Loss of quadriceps
strength and atrophy
Wilkinson124 1977
31
7.7
61%
Maximal recovery up to 3 yrs
Peeples125 1978
14
4.6
85%
Böstman
10
Not specified
Partial superior to total patellectomy
Jakobsen12 1985
28
20
79%
Mean quadriceps strength 66% of normal side
51
Levack101 1985
34
6.2
80%
Muller126 2003
12 acute patellectomy
9 delayed patellectomy
9.3
Mean hospital for Special surgery score 68.4 (primary 71;
delayed 63.8); primary group better range of motion
(123 degrees vs.114 degrees)
or complete patellectomy, with the contralateral normal knee
serving as a control. Total excision was associated with a 49%
reduction in strength of the extensor mechanism and a mean
loss of 18 degrees in range of motion. Functionally, there was a
high incidence of instability, with an inability of the patients to
support their weight on the loaded knee with stair climbing.123
Einola et al.11 reported on 28 patients with a mean 7.5 years of
follow-up, and reported a good result in only 6 patients. Quadriceps power was within 75% of the contralateral knee in only
7 patients. Scott14 similarly reported a good outcome in only 4
of 71 patients, with 90% complaining of chronic pain. Quadriceps atrophy, pain, and instability in the knee during running
or stair climbing were common complaints of patients in both
series. Wilkinson124 evaluated 31 patients with up to 13 years of
follow-up, and reported an excellent outcome in less than 25%
of patients. Furthermore, Sorensen127 noted that no patients
regained full quadriceps strength after patellectomy, and that
none of their operative reconstructions would have fared better
with primary excision. For these reasons, it is our recommendation to avoid total patellectomy whenever possible. We have
not encountered a patella so comminuted that a single fragment could not be preserved acutely. Maintaining even a single
fragment provides a lever arm that substantially improves the
function of the extensor mechanism.69 If a total patellectomy is
performed, consideration should be given to augmenting the
repair with VMO advancement. Günal et al.128 in a prospective
randomized trial compared the results of 16 traditional total
patellectomy procedures with 12 cases augmented by VMO lateral and distal advancement. Strength, limitation of activity, and
subjective functional assessment were significantly improved
with VMO advancement. Lastly, the decision to operate acutely
compared to a delayed fashion remains controversial. Muller
et al.126 retrospectively reviewed their results of early (<4 weeks)
versus delayed patellectomy, and identified no differences in
range of motion or clinical outcome scores between the groups.
Open Fractures
Open patellar fractures constitute a surgical urgency and warrant timely irrigation, debridement, and stable fixation. A thorough debridement includes removal of all devitalized fragments
and soft tissue, followed by serial debridement, skin grafting,
and the use of local or free tissue flaps if necessary for wound
closure. Appropriate antibiotic coverage is also essential.
Catalano et al.34 reported on a series of 79 open patella fractures with a mean of 21-month follow-up. Almost all fractures
were displaced, with 22% transverse patterns and 39% comminuted, stellate injuries. The majority (53%) were Gustilo and
Anderson Grade II injuries. Surgical intervention consisted of a
thorough irrigation and debridement followed by open reduction and internal fixation in 57% and partial patellectomy in
32% of cases. Outcomes were satisfactory in most cases with
only case of revision internal fixation for failure and no cases of
deep infection. The Mayo Clinic’s retrospective review of open
patellar fractures also reported 77% good to excellent results,
with no infections in type I or II open injuries that were treated
with immediate internal fixation after irrigation and debridement.102 Anand et al.32 recently presented long-term outcomes
of 16 open patellar fractures and compared their results to a
matched group of closed injuries. The injury severity score
(ISS) and the incidence of associated musculoskeletal injuries
were significantly higher in the open patellar fracture group.
At a mean of 45-month follow-up, patients with open patellar fractures had a higher incidence of complications, a lower
KOOS, and a higher visual analog score for pain.32
Author’s Preferred Method of
Treatment for Patella Fractures
Patients with an Intact Extensor
Mechanism, Vertical Fractures, and Minimal
Articular Displacement or Patients Unfit for
Anesthesia
In these situations, we employ nonoperative care (Fig. 54-8).
The exception is the patient with normal extensor mechanism
function, but with significant articular incongruity or fracture
gap. In patients with a large traumatic hemarthrosis, we will
consider aspiration of the joint and injection of a local anesthetic to facilitate physical examination.
With compliant and reliable patients, we use a hinged knee
brace locked in full extension. The brace is lightweight, allows
for patient hygiene and monitoring of any abrasions or associated soft tissue injuries. Furthermore, controlled range of
motion may be initiated once fracture callus is radiographically
confirmed. In patients with questionable compliance or elderly
patients who are at significant risk for falls, we prefer to utilize
a fiberglass cylinder cast applied from the groin to just above
the ankle, molded with the knee in full extension. Care must be
taken, particularly in elderly or diabetic patients, to pad carefully to avoid iatrogenic soft tissue injury from a poorly molded
cast. In patients with lower-extremity venous stasis ulcers or
compromised circulation, an Unna boot can be applied prior
to cast molding to protect the soft tissues.
Isometric quadriceps exercises with straight-leg raises are
initiated 1 week after immobilization to minimize quadriceps
atrophy. Partial weight bearing with crutch assistance is allowed
immediately with advancement to full weight bearing in extension as tolerated. Follow-up radiographs are obtained at regular intervals to confirm that reduction has been maintained. If
fracture displacement occurs early, surgical stabilization should
be considered. After fracture consolidation is radiographically
confirmed, controlled range of motion of the knee is initiated.
Marginal or small nonarticular fractures of the patella are
often stable due to the preserved integrity of the soft tissues. In
these cases, cast or brace immobilization is often unnecessary,
and early, controlled range of motion with activity modification
is initiated as tolerated.
Displaced Fractures
Preoperative planning is often difficult with patellar fractures
as the fracture lines and comminution are not always clearly
visualized using standard imaging. It is imperative to have all
of the necessary equipment available in the operating room to
perform either internal fixation or a partial patellectomy. At
minimum, small and mini-fragment implant sets with 3.5- and
2.7-mm cortical screws for interfragmentary fixation, 1.6- and
2-mm Kirschner wires, 18-gauge wire, and 14- or 16-gauge
angiocatheters for wire passage are needed. A 4-mm cannulated
screw set can be made available as well to fix transverse fracture patterns. Small and medium pointed reduction forceps are
helpful for maintaining a provisional reduction. A power drill
with wire driver attachment and wire twisters should be available. If significant distal pole comminution is encountered, a
Patella fracture
Extra-articular
[Au: Pls.
check setting of
Algoritham
for correctness]
Avulsion
partial
patellectomy
Partial articular
extensor mechanism intact
Isolated body
nonoperative
Transverse
cannulated screw
tension band wire
Complete articular
extensor mechanism
disrupted
Transverse + 2nd fragment
ORIF + cannulated screw
or tension band wire
Nonoperative
<2 mm displaced
Complex
Lotke–Ecker
ORIF
Figure 54-8 Algorithm for author’s preferred treatment of patellar fractures.
ORIF
>2 mm displaced
partial patellectomy may be necessary. A Hewson suture passer
may be helpful for passing suture through bone tunnels if a
partial patellectomy is performed.
In the case of open injuries, immediate irrigation and
debridement of the fracture is performed followed by rigid
internal fixation for Type I and II open injuries without gross
contamination. Appropriate antibiotic coverage is selected, and
serial debridement and/or soft tissue coverage are performed
based on the contamination of the wound and the status of
the soft tissues. If there is a question of an open fracture or
traumatic arthrotomy, a saline load test should be performed
in the emergency department. For closed fractures, the status
of the skin and soft tissues helps guide the timing of operative
intervention. Typically, we will wait 1 to 2 weeks in the setting of significant soft tissue swelling or superficial abrasions to
minimize the risk of postoperative wound complications.
We perform the procedure with the patient supine on a
radiolucent table. Intraoperative fluoroscopy is used to obtain
true AP and lateral images. A high nonsterile thigh tourniquet is
placed, but rarely inflated. The fracture is approached through
a longitudinal midline incision with full-thickness skin flaps
and minimal superficial dissection. This extensile approach
provides excellent exposure of the fracture as well as the medial
and lateral retinacular tears.
The fracture lines are carefully defined by debridement of
clot and devitalized debris. In the setting of transverse fracture patterns (OTA C1.1), we prefer a cannulated screw tension band construct (Fig. 54-7). With more complex fractures
in which the larger fragments have additional fracture lines
(OTA C2.1), we attempt to simplify the fracture into a transverse pattern by securing the smaller fragments together with
interfragmentary screws or K-wires. Screws of various sizes may
be necessary based on fragment size and bone quality. Purely
longitudinal fractures (OTA B1.1, B1.2, B2.1, B2.2) can often
be secured with interfragmentary screws alone.
Provisional reduction of the fracture is obtained with the
assistance of a pointed reduction forceps and manual manipulation. The reduction is assessed by both direct palpation of
the articular surface through the retinacular tear and multiplanar fluoroscopy. If the retinacular tissues are intact, we create
a small arthrotomy in the medial retinaculum to allow direct
palpation of the articular surface. Guidewires for cannulated
screws are placed in a retrograde fashion via the fracture line
into the proximal pole. We prefer this technique to assure a
depth 5 mm posterior to the anterior cortical surface. After
drilling, the parallel screws are placed over the guidewires, conferring compression and rotational stability to the construct.
The screw lengths are confirmed under fluoroscopy to avoid
leaving the screw tips proud. The 18-gauge wire is then passed
in a figure-of-eight fashion through the cannulated screws and
the free limbs are twisted to achieve appropriate tension. The
ends are then cut and bent backward into the patellar bone to
minimize subcutaneous irritation from the wire.
In the setting of a displaced, stellate fracture pattern in
which anterior tension banding is not feasible (OTA C3.1,
C3.2), we will utilize indirect reduction with cerclage wiring
followed by the longitudinal anterior banding of technique
Lotke and Ecker13 With severe inferior pole comminution that
is not salvageable (OTA C1.3, C2.3), we perform a partial patellectomy while attempting to preserve as much of the remaining
patella as possible. Interfragmentary screws may be utilized to
stabilize large salvageable independent fragments. Two locking
Krackow sutures are then run in the patellar tendon, resulting
in four core strands which are passed through three tunnels in
the residual patella. The drill holes are placed at the articular
margin to avoid iatrogenic patellar tilt. A burr or rongeur is
used to make a small trough at the inferior margin of the patella
to allow tendon apposition against bleeding, cancellous bone.
We typically protect the partial patellectomy with an 18-gauge
cerclage wire passed superior to the patella across the quadriceps tendon and through the proximal tibia.
Postoperative Management
For fractures with stable internal fixation, we recommend early
physiotherapy and weight bearing as tolerated while limiting
flexion to 30 degrees for 4 weeks at which time range of motion
is progressed. When fixation is tenuous, partial patellectomy is
performed, or when the patient is noncompliant, full weight
bearing in a cylinder cast in extension for 6 weeks is instituted
prior to progression to a hinged knee brace. Isometric quadriceps exercises and straight-leg raises are encouraged as soon as
pain subsides. Range of motion may be delayed in any situation
in which the soft tissue envelope, wound closure, or fracture
fixation is tenuous.
Introduction to Extensor
Mechanism Injuries
Patients with a loss of active knee extension as a result of trauma
without signs of a patellar fracture may have a disruption of the
extensor mechanism. Injuries to the extensor mechanism can
include quadriceps or patellar tendon ruptures, patellar dislocations, or tibial tubercle avulsions. Demographic data suggest
a difference in the occurrence of quadriceps and patellar tendon
ruptures based on age.15 Patellar tendon ruptures occur more
commonly in patients less than 40 years old while quadriceps
tendon ruptures occur more commonly in patients greater than
40 years of age.
Assessment of Extensor
Mechanism Injuries
Extensor Injury Mechanisms
Quadriceps and patellar tendon ruptures are typically lowenergy injuries. A thorough history and physical examination is
helpful in diagnosing a patellar or quadriceps tendon rupture.
Typically, the patient sustains a forceful quadriceps contraction
against a fixed or sudden load of full body weight with the knee
in a flexed position resulting in eccentric loading.
Injuries Associated with
Extensor Mechanism
Quadriceps and patellar tendon injuries most often occur as
low-energy injuries in isolation. However, ACL tears have
accompanied up to 12.5% of high-level sporting injuries resulting in patellar tendon rupture and should be sought during the
initial evaluation or with MRI.129
Signs and Symptoms of Extensor
Mechanism Injuries
Patients may often note prodromal signs and symptoms including pain, atrophy, and tenderness around the distal or proximal patellar pole and/or a history of Osgood-Schlatter disease
or jumper knee.130 Quadriceps tendon ruptures occur more
commonly in patients with systemic disease or degenerative
changes.40,131 Numerous reports of simultaneous bilateral quadriceps tendon rupture have been published and include patients
with systemic illness and obesity.47,132–135 Bilateral rupture of the
patellar tendon can occur but is less frequent.136–139
Pain with an associated tearing or popping sensation is typical, as is the inability to bear weight. The key to diagnosing an
extensor mechanism rupture is the lack of active knee extension
or the inability to maintain the passively extended knee against
gravity. Most commonly, patellar tendon ruptures extend completely through the retinacular tissue resulting in complete loss
of knee extension. Quadriceps tendon ruptures may not involve
as much of the retinacular tissue, and as a result some extension still may be possible. Typically, however, some degree of
extensor lag is almost always present when compared with the
uninjured limb. Immediately after injury, a defect may be palpable at the level of the rupture. However, when the diagnosis
is delayed, the tendon defect may not be palpable secondary to
consolidation of the hematoma and early scar formation.
A traumatic hemarthrosis is common after extensor mechanism injuries. Ice, compression, elevation, and anti-inflammatory
medications can be used to treat local symptoms. Although
no studies have shown a benefit for knee aspiration in these
injuries, aspiration of a tense hematoma may be considered to
reduce pain and promoting recovery.
Pathoanatomy and Applied
Anatomy Relating to Extensor
Mechanism Injuries
In general, healthy tendons do not rupture. Under normal conditions, tensile overload of the extensor mechanism usually
leads to fracture of the patella which is considered the weakest
link in the extensor mechanism.139 McMaster56 studied the tensile strength and location of tendon ruptures in a rabbit model.
Between 50% and 75% of the tendon fibers had to be transected
to result in a rupture under forces greater than those seen under
physiologic conditions. Patellar tendon ruptures secondary to
indirect trauma have been considered the end stage of longstanding chronic tendon degeneration secondary to repetitive
microtrauma. Biopsy specimens of spontaneously ruptured tendons reveal pathologic findings that are degenerative in nature,
including hypoxic tendinopathy, mucoid degeneration, tendolipomatosis, and calcifying tendinopathy140; however, ruptures
may occur in the absence of pathologic tendon degeneration.141
The frequent prevalence of prodromal symptoms associated
with tendon failure seems to support the finding of tendon
degeneration prior to rupture. Kelly et al.130 reviewed 13 athletes
with chronic jumper knee that resulted in tendon rupture. In
this series, younger patients had more severe symptoms than
older patients leading him to conclude that more advanced
degeneration is required to weaken younger healthier tendons.
Prodromal symptoms were present in 46% of NFL players prior
to patellar tendon rupture.129
Extensor Mechanism Injury Imaging and
Other Diagnostic Studies
[AU12]
An AP and lateral plain radiograph should be obtained in all
patients with suspected injury to the knee extensor mechanism.
Plain radiographs are the most cost-effective radiographic means
to diagnose a patellar tendon rupture. The unopposed pull of
the quadriceps muscle will result in proximal migration of the
patella. Patella alta, defined as the position of the patella superior
to Blumensaat line on the lateral radiograph, is consistent with
rupture of the patellar tendon. In addition, if bone fragments are
identified an avulsion injury may be suspected.9 Radiographic
findings suggestive of a quadriceps tendon rupture include
obliteration of the quadriceps tendon shadow, a suprapatellar
mass, suprapatellar calcific densities, or an inferiorly displaced
patella. A study of 18 patients with known quadriceps tendon
ruptures identified at least three of these abnormalities in 17 of
the 18 patients.142
High-resolution ultrasonography has been recognized as
an effective method of examining the patellar and quadriceps
tendons in both acute and chronic injuries.143,144 Raatikainen
et al.145 reported on the successful use of ultrasound in diagnosing partial quadriceps tendon ruptures. MRI is also an effective,
albeit expensive, method of diagnosing extensor mechanism
injuries.91,146,187 It is not recommended in the evaluation of
most suspected extensor mechanism injuries, but may be helpful in patients with neglected tears or partial tendon injuries.
Extensor Mechanism Injury
Treatment Options
Historical Perspective on Extensor
Mechanism Injury
The first known description of a patient with an extensor mechanism injury is found in the translated writing of the Greek physician Galen ca. 80 to 87 AD.147 In 1887, McBurney148 published [AU13]
the first case in the American literature. Conservative treatment
prevailed until the end of the 19th century when Quenu149 pub- [AU14]
lished a review of 26 cases treated surgically and recommended
operative repair. In 1927, Gallie and LeMesurier122 described a
technique utilizing a fascia lata strip to repair a quadriceps tendon
rupture. Following these reports, surgical management became
increasingly accepted and numerous surgeons have subsequently
published their techniques and results.
Nonoperative Treatment of Extensor
Mechanism Rupture
Incomplete ruptures are usually managed conservatively without surgical intervention if full active extension is present on
physical examination (Table 54-12). In addition, nonoperative
[AU15]
Table 54-12
onoperative Treatment of
N
Extensor Tendon Rupture—
[AU16] Contraindications
Indications
Open injury
Medically unfit for surgery
Extensor lag
Full knee extensor function
Loss of knee extensor function
management should be pursued if the patient is medically unfit
for surgery.
Nonsurgical management of a complete quadriceps and
patellar tendon rupture generally yields poor results with longterm disability in gait and weakness.122,150 Untreated complete
ruptures will result in ambulation with a stiff-knee gait or circumduction to allow the foot to clear the ground during the
swing phase of gait. Patients will also complain of knee buckling and difficulty in climbing stairs. Loss of extensor mechanism function is an indication for surgery in all but the most
unhealthy and nonambulatory patients.
Technique for Nonoperative Treatment of
Quadriceps and Patellar Tendon Ruptures
The limb is initially immobilized with the knee in full extension for 4 to 6 weeks after which protected range of motion
and strengthening is begun. Initially, flexion of greater than
90 degree is avoided to reduce stress on the tendon. Restrictions are removed once the patient achieves good quadriceps
muscle control and is able to perform a straight-leg raise without discomfort.
Operative Treatment of Extensor
Mechanism Rupture
Operative treatment is indicated for all extensor tendon ruptures in which extensor mechanism function is compromised,
the soft tissues are adequate for healing, and the patient is fit for
surgery. Many different repair techniques have been described
with no single technique demonstrating superiority.15,150–152
Table 54-13
xtensor Tendon Repair
E
Case Checklist
• OR table
• Standard table
• Position/positioning aids
• Supine positioning
• Often a small bump under the hip is helpful in controlling
external rotation of the limb
• A small towel bump that can be moved below the knee for
slight flexion or under the ankle for knee extension is useful
• Equipment
• Heavy braided nonabsorbable suture
• Suture passer
• 18-gauge wire
• Power drill
• Tourniquet
• Nonsterile if desired
needed, however, one may be placed in a nonsterile fashion and
only inflated if uncontrollable bleeding is encountered.
Surgical Approaches for Quadriceps Tendon and
Patellar Tendon Repair. An extensile straight midline incision is most often employed to expose the knee from the inferior patella to 5 cm proximal to the quadriceps tendon rupture
and from the superior patella to the tibial tubercle for patellar
tendon ruptures. Full-thickness flaps are elevated medially and
laterally to identify the apex of the retinacular tears, if present.
The joint is irrigated to remove hematoma, allow identification
and assessment of the tear, and examination of the patella and
distal femoral articular surfaces.
Technique for Acute Quadriceps Tendon Repair. Avulsion of the quadriceps tendon from the superior pole of the
patella can be treated by debridement of the tendon, followed
by the passage of two heavy nonabsorbable sutures into the
tendon (Table 54-14). Three parallel drill holes are then created
from superior to inferior through the patella. The sutures are
passed through the drill holes and tied at the inferior patella
and the retinacular tissue is repaired (Fig. 54-9).
A midsubstance rupture can be repaired with end-to-end
approximation of the tendon rupture. If the repair is tenuous,
the Scuderi150 technique or quadriceps turndown flap has been
Surgical Procedure
Preoperative Planning for Quadriceps and Patellar
Tendon Ruptures. Inspection of the soft tissues for abrasions, lacerations, or prior incisions should occur prior to
surgery and may influence the placement of the skin incision
(Table 54-13). Equipment considerations for repair are relatively straightforward. Heavy nonabsorbable suture, a suture
passer, and a drill are typically required.
Positioning for Quadriceps and Patellar Tendon
Ruptures. The patient is positioned supine on a standard
operating table. A small bump under the hip is often useful for
controlling external rotation of the limb. In addition, a small
bump of towels that can be moved from beneath the knee and
ankle and vice versa helps in providing slight knee flexion and
extension, respectively, during the case. A tourniquet is rarely
Table 54-14
xtensor Tendon Repair
E
Surgical Steps
• Expose tendon rupture
• Remove nonviable tendon edges
• Place grasping stitches in tendon
• Reattach patellar or quadriceps tendon through three parallel
longitudinal drill holes in the patella
• Secure sutures over bone bridges in full extension
• Assess strength of repair with controlled flexion
• Consider adding a cerclage wire from quadriceps tendon to
tibial tubercle for patellar tendon injury
A
B
Figure 54-9 Acute quadriceps tendon repair. A: Approach is
through a midline longitudinal incision. B: Repair through three parallel drill holes in the patella.
described as a method to reinforce the surgical repair. A partialthickness triangular flap is developed from the anterior surface
of the proximal tendon that is 2 in along the base and 3 in along
each side. The flap is folded distally over the rupture/repair and
sutured into place.
Several authors have suggested techniques for reinforcing
the repair using wire, Dacron tape, or suture.15,47,153 Recently,
no complications and 100% good and excellent results were
reported with use of a braided nonabsorbable relaxing suture
tensioned at 30 degrees of flexion in 20 quadriceps repairs. The
authors felt the relaxing suture reinforced the repair and allowed
early active motion and brace-free ambulation at 6 weeks.154
However, most repairs for tendon avulsions are sufficiently
strong that secondary stress-relieving devices are not required.
Technique for Acute Patellar Tendon Repair. The
site of the tear (proximal, midsubstance, or distal) will dictate
the preferred surgical repair technique. Most patellar tendon
ruptures occur at the insertion on the inferior pole of the patella
as an avulsion. This is believed to be the result of a relative
decrease in the collagen fiber stiffness at the insertion site and
the greater tensile strain occurring at the inferior pole fibers
than in the midtendon.140
Avulsion of the patellar tendon from the inferior pole of the
patella can be treated by debridement of the tendon, followed
by the passage of two heavy nonabsorbable sutures into the tendon. Three parallel drill holes are then created from inferior to
superior in the patella. The sutures are passed through the drill
holes and tied at the superior pole of the patella. The medial
and lateral retinacular tears are identified and repaired. A cerclage or reinforcement suture or wire is recommended for most
cases (Fig. 54-10). This is performed by drilling a transverse
tunnel 1 cm posterior to the tibial tubercle and passing heavy
Acute
A
B
C
Chronic
Semitendinosus
D
Gracilis
E
Figure 54-10 Suture technique of patellar tendon repair. A: A suture passer is used to guide the
core sutures through the drill holes. B: The suture is retrieved and tied at the superior margin of the
patella. C: Direct repair to the inferior pole of the patella through three parallel drill holes. D: Addition
of a cerclage wire through the tibial tubercle for protection of the tendon. E: Use of hamstring tendons
placed through bone tunnels for repair of a chronic rupture.
nonabsorbable suture or wire through the hole. This wire or
suture is brought proximally, and passed under the quadriceps
tendon close to the superior border of the patella and tensioned
at 30 degrees of flexion. The knee is flexed to 90 degrees to test
the integrity of the repair. Recently, no complications and 100%
good and excellent results were reported in 30 patients with
this technique employing a braided nonabsorbable suture. The
authors felt this reinforced the repair and allowed early active
motion and brace-free ambulation at 6 weeks.154 Alternatively,
hamstring autograft can be utilized. The semitendinosus tendon
is harvested with an open tendon stripper leaving the insertion
intact. The proximal aspect of the tendon is then passed through
a transverse drill hole in the patella and sutured to the distal
lateral retinaculum or patellar tendon. This method has been
shown to lead to less gap formation at the repair in biomechanical studies.155 The patellar tendon suture line is then reinforced
with absorbable sutures, the wound is closed in layers and a
well-padded dressing is applied. A hinged knee brace is applied
with the knee in full extension.
A midsubstance tear is more difficult to repair as the quality
of tissue may be compromised and caution should be observed
to prevent shortening of the tendon and creating patella baja
with placement of the sutures. The most common method of
repair involves simple end-to-end repair, with or without a reinforcing cerclage suture of wire or nonabsorbable suture material
or tape. A distal patellar tendon rupture from the tibial tubercle
is the least common pattern. A suture repair through bone tunnels with semitendinosus and gracilis augmentation as described
for late reconstruction is recommended (see below).156
Postoperative Care for Acute Patellar and Quadriceps
Tendon Repair. The postoperative rehabilitation regimen is
based on the surgeon’s assessment of the repair strength. A
repair with poor quality tissue should be immobilized for 4 to
6 weeks in a cylinder cast with weight bearing as tolerated
restrictions. This is more often the case in quadriceps tendon
repair. However, a sturdy repair with reinforcement may be
placed in a hinged knee brace locked in extension and can be
started on early range of motion within 7 to 10 days postoperatively with active and active-assisted exercises.154 In these
cases, initially full flexion is not allowed, but range of motion
is started at 0 to 45 degrees and advancing 30 degrees every
2 weeks. At 6 weeks, the brace may be weaned and a rehabilitation program stressing closed chain eccentric strengthening, to
avoid possible reinjury, may be implemented. Weight bearing
is allowed; immediately, however, the hinged brace is locked in
extension and crutches are used for at least 6 weeks. Competitive sports should not be allowed for 4 to 6 months until the
majority of isokinetic strength has been regained.
Chronic or Neglected Quadriceps Tendon Repair
Techniques. Chronic or neglected tendon ruptures may present significant treatment challenges. When the tendon end can be
approximated to the patella, a primary repair can be performed.
However, a large defect may be present between the ends of the
tendon and the patella preventing tendon apposition. Patients
with a quadriceps tendon rupture older than 2 weeks may have
muscle retraction of up to 5 cm.157 If the tendon has retracted
proximally resulting in a gap, the quadriceps muscle can be
elevated from the femur and adhesions released in an attempt
to gain length. If the tendon ends still cannot be opposed, a
Codivilla lengthening procedure should be considered.158 In this
procedure a full-thickness inverted V is created in the proximal
segment of the quadriceps tendon. The lower margin of the V
should be 1.3 to 2 cm proximal to the site of the rupture. The
ends of the ruptured tendon are approximated and repaired with
heavy nonabsorbable suture. The triangular flap is turned down
distally and sutured into place. The open upper portion of the V
is then repaired in a side-to-side fashion. Scuderi150 described a
variation of this technique for late reconstruction. After the tendon is exposed, a Codivilla or Bennett lengthening is performed.
An inverted V-cut is made through the tendon proximal to the
rupture. The triangular flap is then divided into two flaps: Onehalf thickness flap is incorporated into the Y-plasty and the other
is folded distally to reinforce the tendon repair.
Chronic Patellar Tendon Repair Techniques. Siwek
and Rao15 described a technique of preoperative traction used
in the treatment of three of five chronic patellar tendon ruptures. Preoperative traction was used in the following circumstances: Neglected rupture of the patellar tendon with marked
radiographic or clinical displacement with an inability to move
the patella manually distally. A Steinmann pin was placed transversely through the proximal portion of the patella and 5 lb
of traction was applied from 4 days for up to 2 weeks preoperatively. Knee range of motion was initiated after the traction
procedure. All repairs were augmented with a fascial graft or
Bunnell wire. They reported 90% good to excellent results in
five patients.
Kelikian et al.159 was the first to describe a case using the
semitendinosus tendon to augment chronic patellar tendon
rupture (Fig. 54-10E). In this technique, a staged surgical procedure was performed with skeletal traction applied until the
patella descends to a level 1 in proximal to the tibial articular
surface. Through a proximal incision the semitendinosus tendon was divided at its musculotendinous junction. A longitudinal paramedian incision was performed and drill holes made
in the tibial tubercle and the distal patella. The free end of the
tendon was passed from medial to lateral through the tibial
tunnel and then from lateral to medial through the patella. The
tendon was then brought down and sutured on itself. A cylinder cast was applied for 6 weeks.
Ecker et al.156 reported on four patients who underwent
late reconstruction of the patellar tendon with semitendinosus
and gracilis tendons. Preoperative traction was not used in this
series. Intraoperatively, a Steinmann pin was placed transversely
through the patella and distal traction was applied. The Insall–
Salvati ratio was used to determine the correct height of the
patella. The semitendinosus and gracilis were harvested leaving the distal insertion at the pes anserinus intact. Three large
drill holes were made to accommodate the tendons: An oblique
drill hole through the tubercle beginning proximally on the lateral aspect and extending distally to the medial aspect and two
parallel transverse holes through the patella. The semitendinosus tendon was then inserted from medial to lateral through
Table 54-15
[AU17]
xtensor Tendon Repair Potential
E
Pitfalls and Preventative Measures
Pitfall #1 – Cutting grasping suture with suture needles
Prevention #1 – Use tapered needles and carefully place
sutures
Pitfall #2 – Slack in suture repair
Prevention #2 – Apply tension to grasping suture with each
throw to avoid slack
Pitfall #3 – Patellar tendon repair failure
Prevention #3 – Consider placing a relaxing suture or wire
through the tibial tubercle when there is questionable
tissue quality
Pitfall #4 – Suture repair failure
Prevention #4 – Gently flex the knee after repair to test repair
integrity
advanced 20 to 30 degrees every 2 weeks until full motion is
regained. At that time, gentle active and active-assisted range of
motion as well as light eccentric resistance training is started.
Potential Pitfalls and Preventative Measures. With
repair of extensor mechanism ruptures, the integrity and
strength of the suture repair is paramount (Table 54-15). Using
tapered needles and carefully placing sutures to avoid cutting
previously placed sutures is important. In addition, all slack
should be removed from the suture lines before securing the
knots. The addition of a relaxing suture or wire should be considered for all repairs in which tissue quality is questionable.
When drilling transosseous tunnels, care should be taken to
avoid violation of the articular cartilage with the drill. Finally,
the repair should be taken through a 90-degree range of motion
under direct visualization in the operating room prior to closure to ensure its security.
Treatment Specific Outcomes
the oblique hole in the tibial tubercle and then from lateral to
medial through one of the transverse holes in the patella. The
gracilis tendon was then passed from medial to lateral through
the remaining transverse hole in the patella. A heavy gauge wire
was placed through the tubercle and the distal hole of the patella.
While the patella was maintained in a normal position with the
traction pin, the wire was tightened to hold the position of the
patella. The tendons were then sutured to each other. The wound
was closed and a cylinder cast was applied for 6 weeks. The knee
was manipulated and the wire removed at 6 weeks. Satisfactory
results were reported with all four patients returning to work and
achieving full active extension and 100 degrees of flexion.
Postoperative Care for Chronic Patellar and
Quadriceps Tendon Repair. Repairs of chronic ruptures
are protected more vigorously and for longer duration than
acute repairs. Generally, weight bearing as tolerated is allowed
in a cylinder cast for 6 weeks. Straight-leg raises may be performed. The patient is then transitioned to a hinged knee brace
and allowed to move the knee from 0 to 45 degrees and then
Table 54-16
Acute Quadriceps Tendon Repair. Several authors
have reported good to excellent results in 80% to 100% of operatively treated quadriceps tendon ruptures (Table 54-16). Many
different techniques of primary repair have been described and
no single technique has demonstrated superiority. In early series,
primary end-to-end repair was performed with cast immobilization while in more recent series heavy nonabsorbable sutures
have been passed through bone tunnels and early rehabilitation
undertaken. The only factor that has been associated with inferior results is delay in timing of surgical repair of greater than
2 to 3 weeks.15,161 Scuderi150 reported good to excellent results
in 85% of patients treated using the turndown flap. Siwek and
Rao15 evaluated 36 ruptures and found that the 30 patients who
underwent early treatment obtained good to excellent results
while the three patients treated after 4 weeks all had unsatisfactory results. Larsen and Lund153 reported good to excellent
results in 15 of 18 patients. This study attempted to correlate
radiographic patellofemoral congruence with clinical outcome.
Thirteen of the 18 patients demonstrated incongruence when
Outcomes after Acute Quadriceps Tendon Repair
Ruptures/
Patients
[AU18] Author/Year
Scuderi150 1958
Siwek and Rao15 1981
153
Larsen and Lund
1986
Outcomes (Excellent
or Good Results [%])
Technique
Postoperative
20/18
Suture with turndown flap
Cylinder cast 6 wks
Weight bear as tolerated
100
30/30
Suture end-to-end
Cylinder cast 6–10 wks
100
18/17
Suture end-to-end
Cast 6 wks
83
Rasul and Fischer160 1993
17/17
Suture with drill holes
Cast 6 wks
100
Rougraff161 1996
38/29
Primary suture or drill holes
Cast 6 wks
80
Konrath162 1998
51/39
Suture through drill holes
Early motion with brace
92
Ramseier et al.163 2006
15/15
Cast 6 wks
100
O’Shea et al.164 2002
19/19
Primary suture, screw or wire
augmentation
Cast 6 wks
100
West et al.154 2008
20/20
Suture through drill holes with
relaxing suture
Hinged knee brace, progression to ROM at 7 d
100
Table 54-17
Outcomes after Acute Patellar Tendon Repair
Author/Year
Ruptures/
Patients
Technique
Postoperative
Outcomes (Excellent
or Good Results [%])
Siwek and Rao15 1981
25/25
Suture with Bunnell wire
reinforcement
Cast extension 6–11 wks
96
Kelly130 1984
10/10
Suture through bone tunnels
Not specified
80
Larsen and Lund153 1986
10/10
Suture with reinforcement
cerclage
Cast 6 wks
70
Hsu167 1994
41/35
Suture with wire cerclage
Cylinder cast 6 wks
86
Marder and Timmerman168
1999
14/14
Primary repair without cerclage
Hinged knee brace early
motion
85
Ramseier163 2006
14/14
Limit flexion to 60 degrees
for 6 wks
100
West et al.154 2008
30/30
Suture through drill holes with
relaxing suture
Hinged knee brace, progression to ROM at 7 d
100
compared with the contralateral knee. All patients with residual
pain had patellofemoral incongruence. However, it is unclear
what this finding means as 9 of the 13 patients with patellofemoral incongruence were asymptomatic. They concluded that
patellar congruence was not the only factor contributing to persistent pain after repair. Rougraff et al.161 reviewed 53 ruptures
treated with multiple surgical techniques and postoperative
regimens and found no differences based on repair technique
or postoperative protocol. Patients with delayed surgery had
poorer functional outcome and decreased satisfaction scores.
Konrath et al.162 reviewed 51 quadriceps tendon ruptures in
39 patients treated with heavy nonabsorbable suture placed
through bone tunnels using functional surveys and objective
testing. Ninety-two percent were satisfied and 84% returned to
previous occupations. However, 51% were unable to return to
their presurgery level of recreational activity. Objective testing
demonstrated on average a 12% strength loss in the quadriceps
muscle and 14% strength loss in the hamstrings as well as an
8-degree loss of range of motion. Recently, West et al.154 demonstrated no complications and excellent results in 20 quadriceps ruptures treated with transosseous sutures and a braided
nonabsorbable relaxing suture placed through the quadriceps
tendon and retinaculum and around the distal patella tensioned
at 30 degrees of flexion. The authors then instituted range of
motion from 0 to 55 degrees at 7 days and weaned the patient
to brace-free ambulation at 6 weeks.
Chronic Quadriceps Tendon Repair Outcomes. Overall, the reported results for chronic quadriceps tendon repairs are
less satisfactory than those reported after repair of an acute tear
with residual functional deficits present in most patients.84,150,161
Scuderi and Schrey158 reported good to excellent results in seven
of nine patients treated with their modification of the Codivilla
lengthening technique. Oni165 described the medial transposition
of a 2- to 5-cm strip of vastus lateralis to bridge a large defect in
five chronic quadriceps tendon ruptures. Ramsey and Muller166
reported that four of seven delayed repairs lost between 10 and
20 degrees of full active extension at final follow-up.
Acute Patellar Tendon Repair. Most series have report
between 70% and 100% good to excellent results (Table 54-17).
The majority of patients who undergo early primary repair
achieve a functional range of motion and normal quadriceps
strength. Persistent quadriceps muscle atrophy commonly
occurs, but has not been correlated with loss of strength.15,167
No relationship has been demonstrated between the configuration of the rupture, the method of repair, and clinical
outcome.15,153,160,162 An early repair within 2 to 3 weeks of injury
is the only factor that has been associated with better outcomes.
Siwek and Rao15 reviewed 25 patients treated within 7 days
found that 96% had good to excellent results while only two of
the six patients with a delayed repair had excellent results. They
also noted a greater degree of persistent quadriceps atrophy in
patients treated with delayed repair. Hsu et al.167 reviewed 35
traumatic patellar tendon ruptures treated acutely with primary
repair and a neutralization wire. They reported 20 excellent
(57%) and 10 (29%) good results. The majority of the patients
in this series had sustained the injury on a motorcycle and onethird of the patients had multiple injuries which the authors
concluded may have contributed to the slightly lower success
rate observed. Larsen and Lund153 performed a radiographic
analysis of patellar congruence in a series of patients who underwent operative repair of acute patellar tendon ruptures. Seven
of 10 patients demonstrated incongruity on the Merchant and
lateral radiographs. Patients with residual patellofemoral symptoms all had incongruity but the majority were asymptomatic.
They concluded that articular incongruity may not be the only
cause of persistent knee pain in patients who undergo patellar
tendon repair. Recently, West et al.154 demonstrated no complications and excellent results in 30 patellar tendon ruptures
treated with transosseous sutures and a braided nonabsorbable
relaxing suture placed through the quadriceps tendon and retinaculum and around the distal patella tensioned at 30 degrees
of flexion. The authors then instituted range of motion from 0
to 55 degrees at 7 days and weaned the patient to brace-free
ambulation at 6 weeks.
Chronic or Neglected Patellar Tendon Rupture. Chronic or neglected patellar tendon ruptures present significant operative challenges. The unopposed pull of the quadriceps muscles can result in significant contraction of the
extensor mechanism. Early series recommended preoperative
traction to overcome the contracted quadriceps muscle so that
the tendon ends could be reapproximated.15,159 To our knowledge there have been no large series evaluating the outcomes
after reconstruction of a chronic patellar tendon rupture. Isolated case reports have described different techniques and grafts
including autogenous or allogenic grafts when local tissue is
unavailable.77,122,156,159,169–172 Results have generally been less
satisfactory compared to acute repair.
Author’s Preferred Technique for
Quadriceps Tendon Repair
The most common method of repair we use employs two grasping stitches passed through three longitudinal drill holes in the
patella and tied over bone bridges. To begin, the edges of the
quadriceps tendon are sharply debrided of grossly degenerated
tissue providing a fresh surface to approximate to the patella.
Absorbable sutures are placed into the medial and lateral retinacular tissues, but left untied until after the tendon repair
has been completed. Two heavy nonabsorbable sutures (No.
5 Ticron or Fiberwire) are placed using a running Kessler or
Krackow configuration leaving four strands of suture at the distal quadriceps stump. A trough is then created in the superior
patella using a small burr or rongeur.
Three 2-mm drill holes are made parallel to each other along
the longitudinal axis of the patella from superior to inferior.
A Hewson suture passer is passed from the proximal patella
through the drill hole. A No. 2 nylon suture is looped and
placed into the suture passer which is then pulled out proximally. The nylon suture is used as a shuttle or relay to pass
the tendon sutures through the bone tunnels. The two central
sutures are passed through the middle drill hole and retrieved
at the inferior margin of the patella. The two remaining sutures
are passed in a similar fashion through each of the peripheral
drill holes and retrieved distally. Each of the central strands is
passed under the patellar tendon and retrieved with its match
so that the knots when tied will lie against the patella and not
on top of the tendon. The sutures are tied with the knee in full
extension. A drain is placed in the joint at this time as it can
still be accessed through the retinacular defect. The retinacular
sutures are then tied. If used, the tourniquet is deflated, and
hemostasis is obtained. The hip is flexed and the knee is allowed
to bend passively into flexion. A passive range of motion from
0 to 90 degrees is ideal. Patellar tracking and tension on the
repair are also assessed. Finally, the repair is reinforced with
0 nonabsorbable sutures. The wound is closed with absorbable
suture and the skin with nylon suture.
Acute Patellar Tendon Rupture
A straight midline incision is made from the midpatella to the
tibial tubercle. Full-thickness skin flaps are created to expose
the ruptured tendon and retinacular tissue. The edges of the
patellar tendon are sharply debrided of grossly degenerated
tissue providing a fresh surface to approximate to the patella.
If there are small loose bone fragments they can be excised.
The extent of the medial and lateral retinacular tears must
be defined. These tissues are sutured but not tied with No.
1 nonabsorbable suture (Ethibond). Two No. 5 nonabsorbable
sutures (Ticron, Fiberwire) are woven in a running Bunnell
stitch resulting in one medial and one lateral suture strand and
two central strands. A trough is created in the inferior patella
with a small burr or rongeur to obtain a fresh cancellous bed to
allow tendon–to–bone healing.
Three 2-mm drill holes are made parallel to each other along
the longitudinal axis of the patella from inferior to superior. A
Hewson suture passer is passed from the distal patella through
the drill hole. A No. 2 nylon suture is looped and placed into the
suture passer, which is then pulled out distally. This technique
shuttles the nylon suture through the hole so that the core tendon sutures can be passed easily and retrieved proximal to the
patella. The two central sutures are passed through the middle
drill hole and retrieved at the superior margin of the patella.
The two peripheral sutures are each passed through a drill hole
in a similar manner. Each of the central strands is then passed
under the quadriceps tendon so that the knots when tied will
lie close to the patella and not on top of the quadriceps tendon. Tension is applied to the sutures which are clamped but
not tied. A lateral radiograph is obtained to assess the patellar
height in relation to Blumensaat line and in comparison to the
contralateral knee. Suture tension can be increased or decreased
to control the patellar tendon length. The sutures are then tied.
A deep drain is placed and the retinacular tissue sutures are tied.
Reinforcement is often necessary with a patellar tendon repair
to counteract the force of the quadriceps muscle contraction. A
transverse 2.5-mm drill hole is made 1 cm posterior to the tibial
tubercle. An 18-gauge wire is passed through the hole, brought
proximally, and passed under the quadriceps tendon close to
the superior border of the patella and twisted until it is tight.
The reinforcement wire is tightened with the knee in some flexion in order to avoid shortening the tendon. The knee is flexed
to 90 degrees to test the integrity of the repair. The patellar tendon suture line is then reinforced with absorbable sutures. The
wound is closed in layers and a well-padded dressing is applied.
A hinged knee brace is applied with the knee in full extension.
Active flexion and passive extension are begun by 2 weeks
postoperatively starting at 0 to 45 degrees and advancing 20 to
30 degrees every 2 weeks. Active knee extension is permitted at
6 weeks. Weight bearing is allowed immediately and crutches
are used for at least 6 weeks. The hinged knee brace and crutches
are discontinued when the patient is able to ambulate with good
quadriceps control.
Tibial Tubercle Avulsions
Tibial tubercle avulsions represent an uncommon variant of
extensor mechanism injuries. Treatment concepts are similar
to those employed in the treatment of distal pole patellar avulsions. If the bone fragment is large enough, internal fixation
with 3.5-mm or 4.5-mm screws should be performed with the
addition of a stress-relieving cerclage wire to the protect repair.
If the tubercle fragment is too small for screw fixation, the tendon should be reapproximated to the proximal tibia through
bone tunnels similar to the treatment used in other tendon
avulsion injuries.
Acute traumatic patellar dislocations occur with an average
annual incidence of 5.8 per 100,000 increasing to 29 per
100,000 in the 10- to 17-year age group.173 Lateral patellar dislocations occur most commonly and conservative treatment is
usually recommended.67,173–175 The majority of patients experience no further instability with reported recurrence rates after
conservative treatment of 15% to 44%.173 Following a knee
injury, osteochondral fractures at the medial inferior edge of
the patella are highly suggestive of this injury pattern. Treatment of an acute lateral patellar dislocation typically consists of
reduction and the use of an extension brace or cast for 3 weeks
with immediate weight bearing. Range of motion in flexion is
increasingly permitted over the following 3 to 4 weeks. Atkin
et al.174 prospectively studied 74 patients with primary acute
patellar dislocations treated initially with a knee immobilizer
for comfort allowing them to bear weight as tolerated with
crutches. As soon as patient comfort allowed, a patellar stabilizing brace was used and resisted close-chain exercises and
passive range of motion in the brace were permitted. Return
to sports was allowed when full passive range of motion was
regained, when no effusion was present, and when quadriceps
muscle strength achieved 80% of the contralateral side. No
recurrences were seen at 6 months with this protocol.
Despite the low recurrence rate there remains much controversy regarding the management of these injuries particularly
with respect to operative indications. Most authors support
operative fixation of a large displaced osteochondral fracture.67,173–175 The presence of a hemarthrosis increases the likelihood that a significant osteochondral fracture has occurred.
Articular cartilage injuries are common and have been reported
to occur in up to 95% of first-time dislocators.68 This reported
high rate of articular cartilage injury has led some authors to
advocate routine arthroscopy to evaluate this injury.67,176 However, a consensus statement issued by the International Patellofemoral Study Group in 2007 recommended that patients at
high risk (i.e., those with a large hemarthrosis) undergo MRI
to detect osteochondral fractures.173 MRI is also helpful in
determining medial soft tissue injuries specifically injury to the
medial retinaculum, the medial patellofemoral ligament, and/
or the VMO.177 This recommendation was made based on the
observation that while articular injuries are common not all
require treatment. A second controversy is whether primary
patellar dislocators should undergo acute surgical management
to decrease the risk of future instability. While there are many
reports in the literature, there are only three studies that directly
compare operative and nonoperative management.173,178,179
None of these studies were able to identify any difference in
outcome between the two treatment groups. Therefore, relative
indications for early surgical treatment have included concurrent
osteochondral injury, palpable disruption of the medial patellofemoral ligament-VMO-adductor mechanism, MRI findings of
a large complete avulsion or midsubstance tear of the medial
patellofemoral ligament, patellar subluxation on a Merchant
view, and early failure of nonoperative management with subsequent redislocation.175
Author’s Preferred Technique for
Patients sustaining a first-time patellar dislocation are treated with
closed reduction and immobilization of the knee in extension for
1 to 2 weeks. Radiographs are obtained after reduction. Patients
are permitted to fully weight bear in the immobilizer. If a large
hemarthrosis is present or plain-film evidence of osteochondral
fracture exists, an MRI scan is obtained. At 1 to 2 weeks, the
patient is transitioned to a patellar stabilizing brace and begins
therapy focusing on range of motion and quadriceps, especially
VMO strengthening. Patients may return to athletics when range
of motion and strength approach the uninjured side.
Management of Expected Adverse
Outcomes and Unexpected
Complications in Extensor
Mechanism Injuries
Loss of Knee Motion
The most common reasons for a suboptimal outcome after an
extensor mechanism injury are the loss of knee flexion and
quadriceps weakness (Table 54-18).28 In general, these complications are more closely associated with the injury itself than
with the technical aspects of the surgical procedure. An aggressive postoperative program emphasizing early range of motion
and quadriceps strengthening is recommended. In order to
achieve this goal, it is paramount to achieve an operative repair
that is strong enough to allow early postoperative rehabilitation. Most patients will ultimately be able to achieve 90 degrees
of flexion. This is critical as it allows for sitting in tight places
and also helps with arising from a sitting position. If 90 degrees
of flexion is not obtained by 8 weeks postoperatively, a closed
manipulation under anesthesia may be considered. However,
caution should be used to avoid iatrogenic rerupture of the
Table 54-18
ommon Adverse Outcomes and
C
Complications following Extensor
Mechanism Injury
• Loss of knee range of motion
• Quadriceps weakness
• Extensor Lag
• Painful hardware
• Infection
• Wound breakdown
• Loss of fixation
• Refracture
• Tendon rerupture
• Nonunion
• Knee arthritis
tendon or refracture. Arthroscopic debridement and manipulation may also be considered to treat a flexion contracture or
more severe flexion loss.180
Extensor Mechanism Weakness
Persistent quadriceps atrophy is noted in many patients but
may not compromise final function. Siwek and Rao15 reported
that 75% of their patients who underwent acute quadriceps
tendon repair had persistent quadriceps atrophy ranging from
2 to 4 cm. However, despite the marked atrophy most had
strength which was adequate for normal knee function. In
regard to patellar fracture, persistent articular step-off has been
correlated with decreased quadriceps strength.181 The treatment
for an extensor lag secondary to weakness or atrophy is a vigorous rehabilitation program.
Symptomatic Retained Hardware
The subcutaneous location of the patella and extensor mechanism results in a high incidence of prominent or symptomatic
hardware. The problem is more common with the addition of
a cerclage or tension band wire. Symptoms are related to irritation of the capsule and tendons by the implants. Up to a 40%
incidence of soft tissue irritation from hardware that necessitated removal was reported in three series.29,103,182 Removal of
prominent cerclage or K-wires usually alleviate symptoms and
can be performed on an elective basis. The use of nonabsorbable suture in place of metal wire has become more popular in
an attempt to avoid this complication and comparatively fewer
reoperations for symptomatic hardware been reported.92,95,96
Infection and Wound Complications
Infection and wound complications are infrequent in closed
injuries and often are related to patient-specific conditions
and the subcutaneous positioning of heavy sutures or wires
used in surgical repair. Sutures should not be placed directly
in line with the incision to minimize the risk of delayed wound
healing. Placing the skin incision lateral to the tibial tubercle
may provide better soft tissue coverage. A postoperative hematoma can result in pain and an increased risk of wound dehiscence and infection. The use of closed suction drainage is
recommended to avoid hemarthrosis formation.
While infection after surgical management of closed injuries
is relatively uncommon, the rate of postoperative infection following open patella fractures has been reported to be as high as
10.7%.102 Surgical debridement of nonviable tissue (soft tissue
or bone) and evaluation of the stability of fixation remain the
standard tenets of care. After thorough irrigation and debridement, stable fixation can be retained. Intraoperative cultures
should be used to guide an organism-specific, 6-week course of
intravenous antibiotics. Suppressive oral antibiotics can be considered until fracture union is secured and hardware removal
can be undertaken. In the vast majority of cases, early recognition of infection and aggressive debridement of nonviable tissue
will allow for preservation of the patella. A total patellectomy,
however, rarely may be necessary in situations of intractable
osteomyelitis and secondary nonunion.
Loss of Fixation/Refracture/Rerupture
The rate of loss of reduction after open reduction and internal
fixation of patellar fractures has been reported to range from 0%
to 20% in clinical series.28,29,103 Inadequate fixation, severe comminution, early aggressive rehabilitation, and patient noncompliance have all been implicated as risk factors. Smith et al.103
noted 11 cases of lost reduction in a series of 51 patients. Five
cases were attributed to technical errors in tension band wire
placement, five to patient noncompliance, and one to sequelae
of infection. Nine cases had symptomatic hardware that ultimately required removal. Nonoperative management with a
period of immobilization may be acceptable with minimal displacement (≤2 mm) or incongruity of the fracture fragments
after loss of reduction. However, reoperation is warranted if
the extensor mechanism is compromised or separation of fragments or incongruity of more than 3 to 4 mm has developed.
Rerupture after tendon repair can be seen in patients who
return to activities too early before the bone–tendon junction
has healed. Timely diagnosis and revision is usually successful in re-establishing knee motion and strength. Competitive
sports should not be allowed for 4 to 6 months to allow time for
sufficient tendon healing and remodeling. Isokinetic strength
should be regained before resuming high-risk activities.
Delayed Union and Nonunion
Nonunion occurs infrequently in patellar fractures with an incidence ranging between 1% and 12.5%.26,51,74 Factors associated
with nonunion include transverse fractures, open fractures, and
nonoperative treatment.80 Elderly patients may tolerate a nonunion well with minimal functional deficits even with persistent
muscle weakness and an extensor lag. However, reoperation
should be considered in young, active patients as a recent systematic review reported no cases of successful union in conservatively treated patellar nonunions.80 Revision surgery with rigid
internal fixation and autogenous bone grafting provides better
opportunity for union. Weber et al.26 achieved a 100% union
rate in their series of patellar fracture nonunions using these
techniques. Uvaraj et al.183 recently presented outcomes of surgical management of 22 patellar nonunions treated at a median
of 3 months from injury to surgery. Nineteen cases were treated
with tension band wiring +/– cerclage and three cases were managed with patellectomy. At a median of 5.5-year follow-up, 91%
good to excellent results were seen.183 Intraoperatively, if extensive cartilage injury is noted or the fragment appears to have a
poor blood supply, a partial patellectomy may be considered.
Whether revision internal fixation or partial patellectomy is
undertaken, reconstruction of the extensor mechanism should
be performed whenever possible. For long-standing nonunions,
a shortened and contracted quadriceps tendon may necessitate
tendon mobilization and quadricepsplasty.184,185
Post-traumatic Arthritis/Pain
Post-traumatic osteoarthritis can be the sequela of patellar
fractures. The etiology is likely multifactorial, and may include
(i) articular cartilage damage at the time of injury, (ii) inadequate reduction and restoration of articular congruity, and
(iii) excessive callus formation and secondary articular incongruity. Nummi51 reviewed more than 700 patellar fractures
and found radiographic evidence of patellofemoral arthritis in
56.4% of the patients. Sorensen127 at 10 to 30 years followup reported a 70% rate of radiographic signs of arthritis after
patellar fracture. Despite its frequency, most patellofemoral
pain can be managed conservatively with rest, physical therapy, and nonsteroidal anti-inflammatory medications. Severe
debilitating patellofemoral arthritis can be treated with a
patellectomy or patellofemoral arthroplasty.186 Nonanatomic
attachment of the patellar tendon to the patellar remnant after
partial patellectomy can lead to abnormal patellar tilt, and has
been implicated as a cause of patellofemoral arthritis. In 1958,
Duthie and Hutchinson111 reported tilting of the patella in five
of seven patients with postoperative arthritis, and attributed
these changes to malalignment from attachment of the patellar
tendon to the anterior cortex of the patella.
Summary, Controversies, and
Future Directions
Extensor mechanism injuries encompass a wide array of injury
patterns. Good to excellent outcomes can be achieved in the
treatment of acute injuries with numerous treatment strategies;
however, close attention to the specific injury pattern and careful nonoperative and surgical technique is paramount in the
successful treatment of these injuries.
In the event of complete extensor mechanism disruption, the
indications for operative intervention are rarely debated; however, the treatment constructs and postoperative rehabilitation
remain somewhat controversial. The paucity of high-quality literature contributes to this ongoing debate. Continued research
on alternatives to stainless steel wire in tension band constructs
holds promise in minimizing soft tissue irritation and subsequent
reoperation, while limited reports of suture anchor fixation for
quadriceps or patellar tendon ruptures as well as partial patellectomy indicate this technique may be a less invasive alternative
with similar outcomes.187,188 In addition, validation of a patellar
fracture classification and development of a validated outcome
score specific to extensor tendon ruptures and patellar fractures
will increase the quality of future research.
[AU20]
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AU1: Head levels H1 and H2 have been updated according to the template (in text also). Please check and confirm the change made
in local toc and text
AU2: As per layout received, “Author’s Preferred Treatment Method” was in box format. But in the sample approval chapter they were
set in local TOC also. Please check and confirm.
AU3: “Bruce and Walmsley” have been changed to Kelly et al.9 as per reference list. Please check and confirm.
AU4: The author name “Pauwel” has been changed to “Muller et al.25” as per the reference list. Please check and confirm.
AU5: “Nummi” has been changed to “Günal et al.128” as per reference list. Please check and confirm.
AU6: The heading “Patellar Fracture and Extensor Mechanism Injury Imaging and other diagnostic Studies” has been changed to
“Patellar Fracture Imaging and Other Diagnostic Studies” as per template. Please check and confirm.
AU7: Please check whether the unit provided in “inch” can be converted to “unit in centimeters” (similar for units in “pound” can
be changed to unit in “kg”).
AU8: The heading “Patellar Fracture and Extensor Mechanism Injury Outcome Measures” has been changed to “Measures of Patellar
Fracture and Extensor Mechanism Injury Outcomes” as per template. Please check and confirm.
AU9: “DePalma” has been changed to “Takebe and Hirohata77” as per reference list. Please check.
AU10: Please check whether the heading “Technique” can be changed to “Partial Patellectomy Surgical Technique.”
AU11: The heading “Outcomes” has been changed to “Treatment Specific Outcomes” as per template (similar cases). Please check
and confirm.
AU12: Please check whether “Imaging and Other Diagnostic Studies’ can be given under the heading of “ASSESSMENT OF EXTENSOR MECHANISM INJURIES.”
AU13: Please check the inserted text.
AU14: “Quenu and Duval” have been changed to “Quenu149” as per reference list. Please check.
AU15: Please check whether “Extensor Mechanism Rupture” can be changed to “Extensor Mechanism Injury” throughout the chapter.
AU16: As per table caption please confirm whether we can change Indications and Contraindications in the first and second columns,
respectively.
AU17: As per template, can we change “Potential Pitfalls and Preventions” in two separate columns.
AU18: Please check whether we can remove the year along with the author names and their cross-references (similar cases in other
tables).
AU19: Author for Figure 3 - the label for the ratio was changed per the note from the editor – was unsure if there were any other
changes needed to the figure. If so please mark up the proof and either the typesetter or publisher will make the change and
send you a revised proof for review and approval.
AU20: References have been updated as per pubmed. Please check and confirm.

PATELLA FRACTURES AND EXTENSOR MECHANISM INJURIES

Transcription

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