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ALTERNATIVE TECHNIQUES
SUBCHONDROPLASTY
AS AN EMERGING
TREATMENT OPTION
FOR SPORTS-RELATED
SUBCHONDRAL STRESS
FRACTURES
®
– Written by Jack Farr and Steven Cohen, USA
For athletes, a speedy recovery from injury
is vital. This article will describe how knee
overuse injury and arthritis can lead to
stress fractures and bone marrow lesions
in the subchondral bone. We then discuss
prognosis with traditional treatment options and present an emerging option – subchondroplasty – for treating bone marrow
lesions. Finally, we present case studies from
our practices in which sports-injury-related
bone marrow lesions were treated with subchondroplasty.
Overuse, injury and osteoarthritis (OA)
place undue stress on the knee joint, leading
to microtrabecular fractures, visualised
as bone marrow lesions on MRI. The
subchondral bone is exposed to high loads,
especially during exercise, when muscledriven accelerations increase the effective
load by multiples of body weight (e.g.
walking 1 to 2x; running 3 to 5x; explosive
jumping/landing 6 to 8x body weight).
Several anatomical adaptations allow the
subchondral bone to accept these loads. The
meniscal cartilage in the knee joint serves
to spread the femur’s load over a larger area
of the tibial plateau (stress = force/area).
Additionally, the articular cartilage and
properly functioning muscle units cushion
dynamic articular forces, spreading impact
loads over a greater number of milliseconds,
thereby reducing peak load.
The subchondral bone
The subchondral bone’s ability to bear
load can be compromised by a host of
injuries to the knee joint, ranging from
overuse to exercise-related injury. For
example, a meniscus tear resulting in a
partial meniscectomy surgery will reduce
the contact area of the articulation between
the femur and tibia, thus increasing the
stress in the subchondral bone in both the
tibia and femoral condyle. Sports injuries
such as ACL tear and patellar dislocation can
delaminate the articular cartilage, resulting
in compromised dynamic load sharing. In
Figure 1a, such injuries are represented as a
leftward shift along the X-axis.
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Load
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Healthy
• Articular cartilage
delamination
• Meniscus removal
• Osteoarthritis
Normal
Capacity to bear load
3z
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1y
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• Articular cartilage
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• Meniscus removal
• Osteoarthritis
Normal
Capacity to bear load
Figure 1: (a) Relationship between load, capacity to bear load and fractures. (b) Illustration
of typical clinical courses. Scenario 1: patient exercised too much and developed a classic
stress fracture (1x). Diagnosis led to the recommendation of extended rest of the joint, which
eventually resulted in healing of the affected tibial trabecular bone (1y). Scenario 2: patient
developed a classic stress fracture (2x), but did not reduce exercise, resulting in progression
to a macroscropic fracture (2y). Scenario 3: patient tore her ACL, resulting in delamination
of articular cartilage (3x). She did not heed exercise restriction recommendations, resulting
in an insufficiency fracture (3y). She was treated with subchondroplasty and rest and her
fracture healed (3z).
Microtrabecular fractures
Normal trabecular bone maintains
structural homeostasis: microtrabecular
fractures occur naturally and injured bone
is removed and replaced to maintain the
health and strength of the bone. This steady
state cannot be maintained when higher
loads (represented in Figure 1a as upward
shifts along the Y-axis) cause the rate of
microtrabecular fractures to exceed the
bone’s ability to repair them. The result
is a stress fracture (shaded region above
the diagonal in Figure 1a), which can be
detected by bone scan and MRI. At first
the stress fracture is asymptomatic, but
as it progresses it becomes increasingly
painful. When a stress fracture occurs in a
healthy and uncompromised knee joint (i.e.
involvement of abnormal stress on a normal
joint), it is termed a ‘classic’ or ‘fatigue’
stress fracture. When it occurs in a kneejoint-compromised patient (i.e. normal
stress on an abnormal joint), it is termed an
‘insufficiency’ stress fracture.
Microtrabecular stress fractures and imaging
Microtrabecular stress fractures lead to
changes in the marrow between trabeculae.
These trabecular fractures are rarely
detectable on plain film radiographs. When
radiologists first saw these changes on MRI,
they noted the signal was similar to that
associated with water and thus assigned
the misnomer 'bone marrow oedema'. In
the early stages of overloading, it may truly
be water content1. However, over time these
changes, known as bone marrow lesions
(BMLs) by orthopaedic surgeons, are actually
indicative of microtrabecular fractures and
associated bone remodelling. Radiologists
are concerned that the term BML could
imply sarcoma or other pathology and are
slowly changing their terminology to ‘bone
marrow oedema-like lesions’. Histological
analyses of BMLs from bone retrieval studies
demonstrate trabecular abnormalities,
necrosis and fibrosis consistent with the
appearance of a non-healing chronic stress
fracture2,3. These MRI findings are also
frequently present with the altered loading
during deterioration due to OA4. Importantly,
stress fractures invariably compromise the
ability of the bone to bear load. An athlete
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ALTERNATIVE TECHNIQUES
a
continuing to overload a stress-fracturecompromised joint risks escalation to a
macroscopic fracture, as illustrated by
Scenario 2 in Figure 1b.
BMLs are associated with pain and
loss of function and indicate an increased
likelihood of total knee replacement when
they occur in OA patients.
Athletes may develop BMLs as a result
of overuse or from mechanical overloading
due to malalignment or meniscal loss and/
or dysfunction. BMLs may also be associated
with a focal cartilage lesion. Finally, a BML
may be present after an impact injury such
as a direct blow to the knee, traumatic ACL
tear, patellar subluxation, dislocation or
impaction injury.
The presence of a BML on MRI is strongly
associated with the presence and severity
of knee pain4 and is even predictive of
subchondral bone attrition5 and loss of
cartilage volume6. In OA joints, the presence
of a BML predicts further progression of
the disease and a possible need for joint
replacement in the future7,8. Scher et al
found that OA patients with a BML on MRI
were nearly nine times as likely to progress
to total knee arthroplasty compared to
those without a BML8.
Treatment of bone marrow lesions
Current treatment options for BMLs can
be slow, ineffective or invasive.
Conservative treatment options may
include activity modification or periods of
non-weight-bearing, particularly for stress
fractures.
• Bracing may also be utilised to unload
the compartment associated with a
BML or to stabilise the patella. In a
recent study of patellofemoral OA,
Callaghan et al found that patients who
used a patellofemoral brace for 6 weeks
saw a reduction both in BML volume in
the patellofemoral compartment and in
knee pain9.
• Physical therapy can also be useful:
incorporating exercises to increase core
stability, pelvic tilt and to strengthen
and co-ordinate the muscles of the
hip and knee, may serve to alleviate
overloading due to muscle imbalance.
Successful
implementation
of
conservative treatment is illustrated by
Scenario 1 in Figure 1b.
b
Figure 2: Subchondroplasty. (a) Red area of tibial plateau indicates region of stress fracture.
(b) Calcium phosphate bone substitute material is injected into the subchondral defect in the
trabeculae of cancellous bone of the knee joint.
•
In some cases, surgery may be warranted
to correct significant mechanical
deficiencies:
• For patients with compartments
overloaded due to malalignment,
osteotomy may be helpful. Meniscal
deficiencies may be corrected
through meniscal transplant.
• For patients with BML associated
with a focal cartilage lesion,
cartilage restoration may be
indicated.
In many cases, chronic BMLs persist even
after conservative care and/or surgery to
correct deficiencies. Additionally, many
athletes are unable to rest for the long
recovery durations required for conservative
care.
Consequently, there is a need for a BMLtargeted therapeutic option which allows
for a shorter recovery time.
Subchondroplasty
Subchondroplasty is a minimally invasive surgical technique that targets
and treats subchondral bone pathology
associated with BMLs, which in turn allows
bone healing. It is usually performed along
with arthroscopy for guided insertion and
concurrent treatment of other pathology
inside the joint. During subchondroplasty, a
calcium phosphate bone substitute material
(BSM), is injected into the trabeculae of
cancellous bone in the subchondral region
of the knee joint (Figure 2). The flowable,
synthetic calcium phosphate readily
fills subchondral defects, crystallising
endothermically in approximately 10
minutes with a porosity and strength
that mimics healthy cancellous bone.
This provides a scaffold for endogenous
osteoclasts and osteoblasts to grow into
and repair the bone. Over time, the calcium
phosphate is resorbed and replaced with
new healthy bone.
Subchondroplasty
treatment
of
subchondral defects can result in reduced
pain and improved function in OA patients.
OA can result in BMLs, which herald
severe joint degeneration and progression
towards the need for joint replacement.
Joint-preserving treatments that reverse
the progression of pain and immobility are
limited for patients who have OA.
A recent retrospective study evaluated
the effectiveness of subchondroplasty for
relieving pain and improving function
in 66 patients with documented BMLs
and advanced knee OA10. Significant
improvements in both pain and
function following subchondroplasty
with arthroscopic debridement were
observed, as measured by the visual
analog scale and the International Knee
Documentation Committee Subjective
Knee Evaluation Form, through 2 years
post-operative follow-up. Given that
arthroscopic debridement alone has been
previously shown to yield insignificant
pain relief beyond 6 months post-surgery,
the results of Cohen et al suggest that
subchondroplasty may be a promising
approach for the treatment of BMLs that
may be associated with OA10.
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3
Figure 3: Case
study 1: preoperative radiograph
demonstrating no
visible transverse stress
fracture at the medial
tibial plateau.
4a
Sports-related injuries and subchondroplasty
Subchondroplasty may be a valid
treatment for bone repair after injury. Sportsrelated injuries that have not responded to
conservative therapies are problematic for
the pathophysiological reasons outlined
above. In addition, chronic BMLs that result
from untreated injuries can contribute
to the progression of OA. The success of
subchondroplasty in treating OA-related
BMLs provides a rationale for exploring
whether this approach will extend to
chronic sports-injury-related BMLs and the
associated trabecular homeostasis that is
critical to long-term bone health.
Case study 1
A 38-year-old male engineer presented
with left medial knee pain that began when
4b
he increased his running mileage to train
for a mini marathon. The patient described
the pain as a constant, dull ache, becoming
moderately intense and sharp with weightbearing activity. The symptoms caused
him to limp and were unresponsive to
medication.
Upon examination, there were no
associated signs such as redness, effusion or
swelling. There was no patellar instability
or loose body sensation. Imaging revealed a
transverse stress fracture at the medial tibial
plateau (Figures 3 and 4). An initial trial of
minimal weight-bearing with crutches was
not tolerated by the patient, who needed
unaided ambulation to work. We discussed
that the MRI was normal and, therefore,
there was no reason to perform arthroscopy.
The patient underwent subchondroplasty
of the tibial plateau (Figure 5).
Figure 4: Case study
1: pre-operative MRI
confirming visible
transverse stress
fracture reaction at the
medial tibial plateau.
Note the stress fracture
reaction is more
readily seen on T2 fatsuppressed sequence
(a).
A needle was placed intra-articularly at
the joint line for reference. Fluoroscopy was
used and the fracture was noted to be 2 cm
distal to the joint line. This was estimated
and a spinal needle was placed at this point.
It was noted that the stress fracture was
now actually a macroscopic fracture and
was visible under fluoroscopy. Therefore, the
needle was placed at that site. A #11 blade
was used to make a slit at this medial aspect
of the proximal pretibial skin. The obturator
was then placed adjacent to the periosteum
and the drill pin inserted. It was positioned
directly over the fracture and then drilled
to the extent of the fracture. The cannula
was then inserted and positioned such
that the openings on the cannula would
allow egress of the BSM into the region of
the fracture. The BSM was mixed and then
injected in four syringes. The obturator was
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ALTERNATIVE TECHNIQUES
5a
6a
5b
6b
Figure 5: Case atudy 1: intra-operative
radiographs. (a) Injection of calcium
phosphate BSM into the region of the
bone marrow lesion. (b) Radiograph
blush of calcium phosphate BSM
following injection.
Figure 6: Case study 1: post-operative
radiographs. (a and b) 1 month postoperative radiographs demonstrating
calcium phosphate persists at site of
injection. (c and d) 18 months postoperative radiographs demonstrating
evidence of some degree of calcium
phosphate resorption.
BSM=bone substitute material.
6c
6d
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7a
7b
Figure 7: Case study 2: preoperative radiographs. (a)
Anteroposterior. (b) Lateral. (c)
Sunrise.
7c
then reinserted and held in position for
10 minutes while the BSM solidified. The
obturator and cannula were removed. There
was no extraneous BSM at the site of the
hole. The skin was approximated with #3-0
nylon using vertical mattress technique and
Steri-Strips. The wound was dressed with
Adaptic gauze, 4x4 flats, ABD pads, Kerlix
wrap and a thigh-high TED hose.
At 1 week after surgery the patient had
decreasing pain and no swelling and showed
no signs of infection. He was completely painfree at 2 weeks and after 5 weeks he was able
to return to light jogging (against medical
advice) and use of an elliptical machine.
By 18 months post surgery the patient had
fully recovered and was able to resume all
preoperative activities. Radiographs at 18
months showed the presence of residual
calcium phosphate in the tibia around the
area of the original fracture (Figure 6). He
was running 10 miles per week and able
to participate in approximately three halfmarathons per year. The patient was pleased
with the overall comfort and functional
status of the knee.
Many athletes are unable to rest
for the long recovery durations
required for conservative care.
Consequently, there is a need for
a bone marrow lesion-targeted
therapeutic option which allows for
a shorter recovery time
Case study 2
A 31-year-old male professional football
player presented with a long history of left
knee problems. He had undergone multiple
arthroscopic procedures on the knee relating
to meniscal tears and chondral defects.
Nineteen months prior to his presentation
he had undergone an osteochondral
autograft transfer to the medial femoral
condyle for a full thickness chondral
defect. Prior to that procedure he had a
microfracture of the same chondral defect.
He was performing well with minimal knee
issues during the early part of a training
camp until his knee began swelling and
he developed increasing medial pain. He
initially had a corticosteroid injection which
failed to improve his symptoms, followed by
a viscosupplementation series.
Examination revealed a standing
alignment of 5 degrees of varus and a range
of motion of full extension to 112 degrees
of flexion. He had a positive effusion of
approximately 20 cm3 with medial joint
line and medial femoral condyle tenderness.
His ligamentous examination was stable.
Weight-bearing X-rays revealed medial
compartment joint space narrowing and
spurring (Figure 7). An MRI scan revealed
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8a
8b
Figure 8: Case study 2: pre-operative MRI. Subchondral oedema in the medial femoral condyle and medial tibial plateau.
evidence of a prior osteochondral autograft
transfer procedure to the medial femoral
condyle with residual medial compartment
chondral loss, synovitis, loose chondral
debris in the supra-patella space and
significant bone marrow oedema in the
medial femoral condyle and medial tibial
plateau (Figure 8).
The surgical and nonsurgical options
were reviewed with the patient at
that point and included continued
conservative management with oral
nonsteroidal anti-inflammatory drugs,
bracing, injections (platelet-rich plasma,
viscosupplementation, corticosteroid) and
return to play as tolerated. The surgical
options included arthroscopic debridement,
synovectomy, loose body excision and
subchondroplasty. The patient elected for
arthroscopy with subchondroplasty, which
was performed. At the time of surgery, the
patient had significant synovitis with 3
loose chondral bodies measuring 5 mm.
He had International Cartilage Repair
Society grade 3 chondral changes to the
trochlea and medial femoral condyle and
grade 2 changes to the central/lateral
facet of the patella. There was no meniscal
or ligamentous pathology. There were
osteophytes and spurring of the medial
femoral condyle and tibial plateau. A
debridement was performed in the medial
and patellofemoral compartments as well
as partial synovectomy and loose body
excision. Subchondroplasty was performed
under fluoroscopic guidance and a total of
6 cm3 of BSM was injected into the medial
femoral condyle and 4 cm3 in the medial
tibial plateau.
The patient was allowed weight-bearing
and range of motion as tolerated. He
advanced his rehabilitation with the team’s
athletic training staff. He began a jogging/
running programme by 2 to 3 weeks after
surgery and returned to full practice by 5
weeks. At 7 weeks his postoperative MRI
showed injection of calcium phosphate
into the femoral condyle and tibia plateau
with some residual oedema (Figure 9). The
patient was allowed to continue progression
of activity as tolerated and returned to full
game participation at 7 weeks.
from sports-related injury/overuse. The
demonstrated success of subchondroplasty
in treating BMLs related to OA and the
initial success shown in these case studies
warrants further exploration of the benefits
of using subchondroplasty to treat BMLs
resulting from sports-related injuries.
Acknowledgements
The authors would like to thank Vanessa
Bender, Dillen Wischmeier, Iman Ahmad
and Margeaux Rogers for critical review
of the manuscript and Brett Mensh for the
conceptualisation of Figure 1.
CONCLUSION
Subchondroplasty is a minimally
invasive surgical technique that targets and
treats subchondral bone pathology to allow
bone healing. Prior work indicates that
subchondroplasty is a promising treatment
for bone marrow lesions related to OA. In the
case studies presented, subchondroplasty
successfully repaired the underlying defect,
thereby restoring full knee functionality
to two patients who had BMLs resulting
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9a
9b
Figure 9: Case study 2: 7 weeks post-operative MRI. Calcium phosphate in the femoral condyle and tibial plateau with some residual
subchondral oedema.
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Jack Farr M.D.
Clinical Professor of Orthopaedic Surgery
OrthoIndy Knee Care Institute
Indiana University Medical Center
Indianapolis, USA
Steven Cohen M.D.
Associate Professor
Rothman Institute of Orthopaedics
Department of Orthopaedic Surgery
Thomas Jefferson University
Philadelphia, USA
Contact: [email protected]
9. Callaghan MJ, Parkes MJ, Hutchinson
CE, Gait AD, Forsythe LM, Marjanovic EJ
et al. A randomised trial of a brace for
patellofemoral osteoarthritis targeting
knee pain and bone marrow lesions. Ann
Rheum Dis 2015; 74:1164-1170.
10.Cohen SB, Sharkey PF. Subchondroplasty
with Arthroscopy Reduces Pain and
Improves Function in Patients with
Symptomatic Bone Marrow Lesions. J
Knee Surg. Forthcoming 2015.
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