The Evolution of the Ilizarov Technique

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Bulletin of the Hospital for Joint Diseases 2013;71(1):96-103
The Evolution of the Ilizarov Technique
Part 2: The Principles of Distraction Osteosynthesis
Rachel Y. Goldstein, M.D., Charles J. Jordan, M.D., Toni M. McLaurin, M.D., and Alfred
Grant, M.D.
Abstract
The history of limb-lengthening surgery can be traced
back to the 19th Century. Since that time, the orthopaedic
community has made tremendous progress in performing
successful lengthening procedures. Among the important
contributors to the field is Dr. Gavril Ilizarov. Because of
advancements over the past century, limb lengthening has
become a viable method of treating severe bony deformities
and defects. This article, the second of a two-part series,
reviews the principles of distraction osteosynthesis, including a thorough discussion of indications, instrumentation,
and surgical technique.
S
ince Ilizarov, significant strides have been made in
furthering the understanding of the biology of limb
lengthening. Much of this work originated with
Ilizarov and was confirmed with further studies across
the United States and Europe. It has been found that the
ligaments and capsule will stretch under gradual tension to
improve joint contractures, while nerves, vessels, and muscle
have been shown to stretch by local neogenesis.1 However,
considerably more attention has been paid to understanding
how distraction affects bone growth.
Distraction osteogenesis is a term used to describe the
de novo production of bone between corticotomy surfaces
undergoing gradual distraction (Fig. 1). New bone forms
by a processes resembling intramembranous ossification.1,2
Within the normal intramembranous ossification, areas of
Rachel Y. Goldstein, M.D., Charles J. Jordan, M.D., Toni M.
McLaurin, M.D., and Alfred Grant, M.D., are in the Department
of Orthopaedic Surgery, NYU Hospital for Joint Diseases, New
York, New York.
Correspondence: Alfred Grant, M.D., Department of Orthopaedic
Surgery, NYU Hospital for Joint Diseases, 301 East 17th Street
#1402, New York, NY 10003;[email protected].
endochondral ossification may also be present.2 Whether
these areas of endochondral ossification within the regenerate are normal or not is controversial. Some investigators
argue that its occurrence is inherent to the normal process
of regenerate formation.3,4 However, Ilizarov and others
have argued that its presence is indicative of instability or
of localized ischemia.5-8
The site where the transported segment meets the target
segment at the end of bone transport is termed the “docking
site.”9,10 The tissue of the docking site is histologically different than that which is seen in the regenerate. Endochondral
ossification predominates over intramembranous ossification
in this region. There is a progressive increase in the quantity
of bony tissue seen here with a concomitant decrease and
final disappearance of necrotic tissue and hematoma. This
region displays a variable quantity of blood vessels. The
histological findings at the docking site do not differ significantly from the normal process of secondary consolidation
seen in a fracture but appear in a slower manner.2
The direction of consolidation of the regenerate is also
a topic of some controversy. Ilizarov and others describe
“zone growth.”1,6,7,11 Zone growth argues that the process
of regenerate ossification occurs simultaneously in the regions adjacent to the osteotomized surfaces. A physis-like
structure ossifies in both the proximal and distal directions
from a central growth zone during distraction. The fibrous
interzone, a collagen-rich central region, is the last zone to
ossify. Under optimal conditions, this growth zone is hardly
visible during distraction. During the neutral fixation period
following distraction, the central growth zone gradually
ossifies. Fibroblast-like cells become metabolically active
and secrete collagen. The collagen eventually forms fibers
that align parallel to the distraction force. Osteoblast activity
results in osteoid and eventually new bone formation. The
new bone formation is greatest at the proximal and distal
ends of the regenerate.
Goldstein RY, Jordan CJ, McLaurin TM, Grant A. The evolution of the Ilizarov technique: Part 2: the principles of distraction osteosynthesis. Bull Hosp
Jt Dis. 2013;71(1):96-103.
Bulletin of the Hospital for Joint Diseases 2013;71(1):96-103
A
B
97
C
Figure 1 The phases of distraction osteogenesis: A, latency, B, distraction, and C, consolidation.
A second school of thought argues that ossification of the
regenerate site progresses in a single direction accompanying
the transported segment of bone.2 This directional growth
has only been seen in animal models.
The Corticotomy
One of the core tenets of Ilizarov’s technique is the use of
a percutaneous corticotomy that minimizes trauma to the
periosteum and preserves the blood supply of the marrow
and periosteum.6 The use of a corticotomy instead of an osteotomy emphasizes the importance of the blood supply to osteogenesis. Both the periosteal and medullary blood supplies
can be preserved by cutting only the cortex. Aronson found
that by minimally displacing the edges of the corticotomy,
the highly elastic spongiosa within the medullary canal can
be preserved along with the medullary blood supply.1 Significant retardation of osteogenesis has been observed in animal
studies with damage to the intramedullary nutrient vessels in
osteotomized bones.7 Animals treated by corticotomy with
preservation of the nutrient vessel, however, demonstrated
a more rapid rate of bone formation.6,7
Ilizarov performed the procedure known as “closed osteoclasis,” whereby wires were placed around the bone and
attached to the frame so that tensioning of the wires would
produce a three-point bending force and fracture the bone
(Fig. 2). Another more common technique involves making
a corticotomy by transecting approximately two-thirds of
the cortex and completing the corticotomy by osteoclasis
produced by rotating the external fixation rings in opposite
directions.1,7 Others have described inserting the osteotome
Figure 2 Closed osteoclasis.
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Bulletin of the Hospital for Joint Diseases 2013;71(1):96-103
into the corticotomy site and rotating it 90° until the remaining cortex fractures.7 Other techniques described include
a complete transverse osteotomy to ensure division of the
entire cross section of the bone or connecting multiple drill
holes with an osteotome. It is also common to perform the
corticotomy with the use of a Gigli saw.
A 1994 animal study demonstrated no histologic, density,
or perfusion differences between the regenerate of dogs that
underwent corticotomy with osteoclasis and the regenerate of dogs that underwent osteotomy with multiple drill
holes.7,12 However, an increased rate of delayed consolidation
was noted in the group that underwent osteotomy performed
with an oscillating saw. The investigators postulated that
this was secondary to thermal necrosis. Yasui found that
a transverse osteotomy was as reliable as a corticotomy in
rabbits as long as the periosteum was protected.13
Distraction
Prior to the initiation of distraction, Ilizarov advocated for
a postoperative waiting period.6 The duration of the latency
period required depends on the preoperative regional blood
flow1 and the amount of damage done during the corticotomy.3 This period generally lasts 3 to 7 days and allows
for neovascularization prior to initiation of distraction.1,11
Ilizarov’s experiments with distraction osteogenesis made
it clear that both rate and rhythm of distraction affect the
quality of the regenerate.6,7,14 Ilizarov performed his experiments in canine tibiae. He found that 0.5 mm of distraction
per day often resulted in premature consolidation of the
regenerate, while 2 mm of distraction per day produced
a poor regenerate often with intervening fibrous tissue.6,15
Distraction of 0.25 mm carried out 4 times per day produced
an excellent regenerate and allowed organization of early
mesenchymal growth into parallel bundles of collagen (Fig.
3). However, he found that the results were further enhanced
when distraction was carried out with an autodistractor that
broke the millimeter daily lengthening into 60 equal steps.
The distraction period proceeds until the desired length
of gap formation is obtained. Collagen bundles begin to
undergo mineralization from both corticotomy sites towards
the center.1,9,10 As long as distraction is continued, the central
region remains fibrous, allowing for viscoelastic lengthening. Mineralization initially protects through the entire cross
section of the gap. At the completion of distraction, this solid
cylinder of new bone remodels into cortex and medullary
canal.
Transformational Osteogenesis
Ilizarov also described the technique of transformation
osteogenesis, which involves the mechanical stimulation of
pathologic bony interfaces through variations in compression and distraction to induce osteogenesis and regenerate
normal bony continuity.6,10,16 He recommended this technique
for the treatment of nonunions. Transformational osteogenesis is less well documented histologically than distraction
Figure 3 Electron micrograph showing healthy regenerate
organized into parallel columnar collagen bundles.
osteogenesis. Success of the technique is dependent on the
stability and composition of the pathologic interface. Ilizarov
argued that a stiff, fibrous nonunion should be treated with
initial distraction.16 Tension is applied across the nonunion
site using the Ilizarov device to induce distraction neogenesis. Once new bone formation is visualized radiographically, the bone ends can then be compressed to transform the
osteogenic bridge into a solid cylinder of bone.1,16
Transformational osteogenesis can be used similarly to
treat a site of mobile pseudoarthrosis. The site must first be
compressed progressively at a rate of 1 mm per day for 10
to 15 days.16 Compressive forces induce local necrosis and
subsequent neovascularization of the cartilaginous interface.
When local resorption occurs, distraction of the site then
renews osteoneogenesis. Following the induction of local
osteogenesis, compression can then be reapplied to successfully unite the bone ends.
Internal bone transportation requires a combination of
distraction osteogenesis and transformational osteogenesis.1,6,10,11 Internal bone transport is used to manage a large
defect within the diaphyseal bone by transporting a metadiaphyseal fragment across the gap. The transported fragment
is created by a corticotomy. Using a series of external fixation
rings, the proximal and distal ends of the bone are maintained
in a stable, fixed alignment. A central ring is connected to
Bulletin of the Hospital for Joint Diseases 2013;71(1):96-103
the bone fragment and is used to transport the fragment
axially across the intercalary defect. The trailing edge of
this fragment undergoes distraction osteogenesis, while the
leading edge of the fragment undergoes transformational
osteogenesis when it contacts the target bone surface.
Biomechanics
The biomechanical goals of external fixation in bone transport are threefold: to maintain the bone ends in stable alignment, to control the movement of the bone projectile, and to
allow compression of the bone in the target zone.1,11 Stable
fixation of the bone fragments is one of the most important
principles in the Ilizarov technique.6 A stable frame permits
full weightbearing, does not restrict the function of adjacent
joints, and permits physiologic function of the entire limb,
ensuring optimal mechanical and biologic conditions.6
Secure fixation limits translational micromotion between
bone fragments. Weightbearing and active muscle function
enhance local circulation and shortens the period required
for osseous callus formation and remodeling.6
The degree of stability of the apparatus depends on
multiple factors.6,15 The number of, and tension on, the
wires influences the stability of the construct. In addition,
the angles between the wires can affect stability. Optimal
stability with two transfixation wires is obtained when the
wires are perpendicular to each other. When anatomic and
functional constraints prevent perpendicular wire placement, supplementary wires may be required. Stability is
also dependent on the number and size of the rings in the
apparatus and the rigidity of the fixator construct. The
amount of compression or distraction incorporated into the
configuration can also contribute to the stability. The shape,
cross-sectional area, and the density of the bone fragments,
as well as the shape, location, and plane of the fracture or
osteotomy relative to the longitudinal axis of the bone are
also important determinants of the stability of the construct.
Myofascial and ligamentous tissues, along with the vectors
of the muscles within the limb, contribute as well.
Inadequate stability can lead to inhibition of union,
damage to the local circulation, and the formation of callus
through fibrocartilage.6 It may also lead to patient discomfort, which can reduce functional use and result in altered
vascularity, edema, joint stiffness, osteoporosis, and complex
regional pain syndrome. Patient discomfort also limits joint
motion, decreases weightbearing on the limb, and can result
in progressive osteoporosis that may lessen the efficacy
of the wire function. Finally, inadequate stability can also
increase the likelihood of wire sepsis.
Essential to the stability of Ilizarov’s construct are thin,
tensioned wires.17,18 These wires form a nonlinear, selfstiffening mechanical structure and provide rigidity against
displacement of the bone ends in six degrees of freedom.
The wires are pre-tensioned to provide an initial stiffness
against displacement perpendicular to the axis of the wire.
Rotational and translational displacements about each wire
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are resisted by coupled forces between adjacent wires within
each ring-wire-bone construct. The system is relatively flexible in the axial direction of the long bone, perpendicular to
the wires, compared with constructions using larger diameter
transfixation pins.9-11,17,18 Bone displacement causes distortions in the wire geometry, creating reaction forces. When
the bone forces and displacements equal the wire forces and
displacements, the system reaches a new equilibrium. The
wires then act as small springs within the more rigid system
of rings and threaded connecting rods.11
In bone transport, the bone projectile movement must
be carefully controlled. Strains across the osteogenic zone
trailing the bone projectile must be controlled though adjustment of both the magnitude and the temporal rate of the
movement.11 The bone projectile must also be moved with a
precise orientation so that the cortical surfaces at the target
site will be aligned. At the end of the transportation cycle,
the target site is then loaded in compression. This will initiate
transformational osteogenesis.1
The Ilizarov Device
The Ilizarov device is a modular construct consisting of 32
individual pieces that allows for 100s of possible configurations. The wires (1.5 mm and 1.8 mm diameter) are connected to modular rings by connecting bolts and are secured
under tensions of 50 to 130 kg. Special stopper, or “olive,”
wires have a 4 mm bead welded along the mid-wire. This
wire can be used to stabilize the near cortex and can function
to dynamically compress fragments or internally transport
bone fragments following corticotomy.
Two to four wires are secured to each ring to stabilize
each bone fragment. Longer bone fragments may require
connecting two rings by threaded rods. After obtaining
fixation, bony transport, compression, or distraction can be
accomplished by gradual tightening or loosening of threaded
connecting rods. The device can then be modified to correct
axial, angular, or rotational deformities.
For bone transport, the simplest most commonly used
configuration consists of three rings, with one proximal to the
corticotomy site, one distal to the zone of the original defect,
and one in the transport segment. The fixator can transfer
loads around the osteogenic site and provide a reaction point
for mechanical forces created during transportation. This
construct may be augmented by additional rings to provide
additional rotational stability.11
Multiple variations exist on this simple construct.11 One
construct employs stopper wires and inclined rods. Stopper
wires are essentially obliquely placed olive wires that pierce
the bone projectile cortices and are fastened only on one
end to inclined threaded rods mounted on a hinged support.
The construct essentially “drags” the segment to the target.
A minimum of two stopper wires are required to provide
stability to the transported bone. Simultaneous rotation of
the threaded rod at its pivot point is required to prevent
bending of the stopper wire. The stopper wire and threaded
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rod construct essentially function as linearly elastic steel lag
screws. If the hinge is left freely mobile, the tension will
automatically rotate the threaded rod into proper alignment.
A second variation is known as the “transportation
ring.”11 This commonly used construct employs transosseous pre-tensioned wires through the bone projectile. The
ring is advanced along threaded connecting rods. While
this configuration is simpler to construct and maintain, there
are difficulties with its use. The movement of the transport
segment may not mirror the transportation ring movement
until the wire forces are equal and opposite to the soft tissue restraining forces. In addition, the transportation ring
requires that the tensioned wires cut linear tracts in the
skin and underlying soft tissues as the transport proceeds.
A variation of this technique is now commonly used which
utilizes half-pins in the transport segment for fixation rather
than wires.
A “stopper wires and transport ring” construct combines
characteristics of both of the constructs.11 Instead of pivots,
the stopper wires are fixed to the transport ring at their initial
angle. The ring is then advanced at the desired rate, as the
stopper wires “pull” the ring. The stopper wire transport
reduces the cutting path of the wires through the soft tissues.
However, it requires a more complex maintenance program
than any of the other constructs. Moreover, successful
transformational osteogenesis may require an additional
procedure to exchange a transport ring for the stopper wires
in order to achieve adequate compression forces.
Complications
Depending on the criteria used, complication rates have been
reported to be anywhere from one to two complications per
lengthening.19 A recent study of patients treated with the
Wagner technique found an average of two complications
per lengthening, at least one of which was usually serious
enough to prevent achieving the original goals of the surgery.20 With the introduction of more physiologic methods
of lengthening pioneered by Ilizarov, bone healing problems have become far less common, severe complications
have decreased, and the goals of treatment are now usually
achieved.19 However, the spectrum of potential complications remains the same irrespective of the technique used.
Tension on the muscle is considered to be the principle
stimulating mechanism for muscle regeneration under conditions of limb lengthening.1 However, this tension can result
in muscle contractures. They occur usually as a result of tension generated due to distraction, occurring when the muscle
length becomes relatively short compared to that of bone.
Contractures tend to occur in the over-powering muscle group
secondary to an imbalance of strength between the flexors
and extensors.19 The muscles most frequently involved in
contracture are those that cross two joints. These muscles
tend to have fibers of various lengths while those that cross
only one joint tend to have fibers of equal length. This may
lead to variations of tension within the same muscle.
Muscle contractures may also occur secondary to trans-
fixation of muscles or tendons by the pins. The risk of occurrence of these types of contractures is increased by the
use of transfixation pins instead of wires, increased diameter
of the pins, or longitudinal clustering of several pins in the
same plane.19 Transfixation of the tendons and fascia tends
to restrict joint motion more than transfixation of muscle.
In order to prevent the occurrence of these contractures,
physiotherapy has been recommended. However, stretching
exercises do not prevent contractures unless they can be
maintained for at least 6 hours per day.19 Paley suggests that
splinting or transfixation across joints is recommended if the
patient is felt to be at risk of developing contractures.19 For
patients who have already developed muscle contractures,
dynamic splinting may be helpful in stretching out the
contracture.19 If non-operative management fails to correct
the problem, several options exist. The bone can be overdistracted to allow for lengthening of the muscle followed
by compression. Alternatively, the apparatus can be applied
across the joint, and the contracture can be corrected. Finally,
tendon lengthening can be considered after removal of the
apparatus.
Joint complications, such as subluxation and stiffness,
are other possible complications of this procedure.19,21 The
most common predisposing factor for joint subluxation is
preexisting joint instability (most commonly secondary to
congenital causes).19 Imbalanced muscle tension that can
develop during lengthening procedures may lead to joint
subluxation. The knee is the most susceptible joint secondary to its inherent lack of bony stability.21 On flexion of the
knee, the hamstring muscles can work unopposed to pull the
tibia posteriorly on the femoral condyles. This complication, if mild, may be treated with physiotherapy to stretch
the deforming muscle force. More commonly, however,
treatment of joint subluxation will require the apparatus
to be extended across the joint in order to first distract the
joint and then reduce it.19 Joint stiffness is generally a late
complication that occurs secondary to persistent muscle
contractures or increased pressure on the joint surface during
the lengthening.19 This may be treated by extension of the
apparatus across the affected joint and distracting the joint.
If this technique is employed, the apparatus must be used
to mobilize the joint prior to its removal.
During the lengthening process, there is a tendency for
the limb segment being lengthened to gradually veer off its
intended course, resulting in axial deviation.19 The direction
of this deviation depends on the bone involved and the level
of the osteotomy. Axial deviation may be caused by muscle
imbalances or instability secondary to an inadequate construct, loss of tension in the pins, or loosening of the pins.
In order to prevent this complication, pins should be placed
5° to 10° inclined to the opposite direction of the expected
deviation. If axial deviation does occur, treatment is possible. If there is less than 5° of angulation, the treatment of
choice involves over-lengthening the side of the deviation.
If the deviation is greater than 5°, the apparatus must be
modified. In larger lengthenings, additional olive wires may
Bulletin of the Hospital for Joint Diseases 2013;71(1):96-103
be required to pull the bone into the proper position.
Neurologic and vascular injuries may occur with limb
lengthening procedures. Neurologic injury may be related
to either surgical technique or the distraction itself.19 Injury related to the surgical technique may occur with pin
placement, or it may occur as a stretch injury during the
osteoclasis maneuver used to complete the osteotomy. Pin
related nerve injuries can best be prevented by a thorough
knowledge of the cross sectional anatomy at the level of
pin placement as well as the placement of pins in “safe”
anatomic planes. A distraction related nerve injury is much
less common. Patients will usually report significant discomfort with this type of complication.19 The first signs of
a distraction related nerve injury are hyperesthesia and pain,
followed by hypoesthesia, decreased muscle strength, and
finally paralysis. Treatment of a distraction related nerve injury includes increased physiotherapy, functional unloading,
and decreased weightbearing of the affected limb. It is also
possible to slow down or temporarily stop the distraction to
allow the nerve injury to resolve.
Vascular injuries may be related either to surgical technique or distraction.19 Rarely, an arteriovenous fistula can
occur secondary to perforation of a vein and an artery at the
same time by a pin. Additionally, placement of a pin directly
adjacent to a pulsating artery can result in late erosions with
pseudo-aneurysm formation. Other vascular-related complications include compartment syndrome and DVTs. Commonly, patients will suffer from edema during lengthening,
particularly in patients who are active and walk frequently.19
Patients must be counseled that it may take several months
after the removal of the apparatus for the edema to resolve
completely.
Other complications may be related to the rate of consolidation at the distraction site. Failure of the osteotomy
site to open after the initiation of distraction is more often
secondary to an incomplete osteotomy than true premature
consolidation.19 When true premature consolidation does
occur, it is likely to be secondary to an excessive latency
period.19 This allows significant callus healing to block the
distraction of the osteotomy site. This complication is most
commonly seen in the femur and fibula, and commonly
occurs in patients with Ollier’s disease. Premature consolidation may be treated with continued distraction until the
consolidated bridge of bone ruptures.19 This type of treatment
results in a rupture that is sudden, unexpected, and painful.
Once the consolidated bridge has been ruptured, the patient
must back up the distraction by the same number of millimeters that had been applied since the bone consolidated. This
technique risks delayed or nonunion. Premature consolidation may also be treated with attempted closed rotational
osteoclasis. If these techniques fail to break the consolidated
bridge of bone, repeat corticotomy may be required.
In contrast to premature consolidation, delayed consolidation of either the regenerate or the docking site may
occur. Rates of delayed consolidation have been reported
anywhere from 35% to 68%.19,22-27 This complication may
101
occur secondary to technical factors including a traumatic
corticotomy, initial diastasis, or excessively rapid distraction. With regards to the docking site, DeCoster reported
that for every day of transport, 2 to 3 days of consolidation
are needed at the docking site.23 Delayed consolidation may
also occur secondary to patient factors including infection,
malnutrition, or metabolic problems. Delayed consolidation requires identification of the underlying etiology with
targeted treatment. Alternating compression and distraction
of the moving segment, or the “accordion maneuver,” may
be applied if consolidation continues to be delayed.28
Pin site problems may also occur. These complications
are related to motion at the pin-skin interface, the amount of
soft tissue between the skin and bone, and the diameter of
the pin used.19 The risk of pin site problems can be lowered
by maintaining adequate wire tension in order to minimize
pin-skin and pin-bone motion. In addition, using rubber
stoppers or cubicle foam sponges may apply pressure to
the skin and stabilize the pin. Pin tract problems always
develop from the outside in and careful inspection of the
pin sites can provide the practitioners with the first sign of
pin tract problems. Problems begin with soft tissue inflammation, progressing to soft-tissue infection, and finally to
bone infection.19 Oral antibiotics may be used to treat soft
tissue infections. However, recalcitrant infections, infections
around wires that pass through joints, and cellulitis about the
pin site may require treatment by removal of the offending
wire.19
After removal of the apparatus, fracture through the
regenerate may occur.19 This can present as gradual axis
deviation of the bone due to incomplete healing, a complete fracture, or buckling of the bone with some loss in
length. This can best be avoided by careful analysis of the
regenerate bone in the distraction gap prior to removal of
the apparatus.19 The ossifying regenerate should have an
even consistency with evidence of neocorticalization and an
opaque appearance similar to the surrounding normal bone
prior to removal of the apparatus. If regenerate fracture does
occur, it may be treated with a cast or with reapplication of
the apparatus.
At times, a fracture may occur as an osteoporotic stress
fracture.19 This is a fracture that occurs through an area
of normal bone and is secondary to marked osteoporosis.
Osteoporosis can occur in these patients secondary to lack
of weightbearing, a hypervascular response to distraction,
pain, or reflex sympathetic dystrophy. The stress fracture
similarly may be treated with either a cast or reapplication
of the apparatus.
Pain is an important consideration in the use of the
Ilizarov technique. Postoperative pain may be intense for
the first few days after the initial operation.19 Contraction
of any muscle transfixed by pins is initially painful but resolves within 1 to 2 weeks. Distraction pain is distinct from
post-surgical pain. Distraction pain is more of a chronic,
dull aching pain that can be extremely variable in patients.
This pain is more common in longer lengthening, double
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level lengthening, or fixation or splinting above or below
the lengthening segment.19 This type of pain is most likely
secondary to stretching of muscles and nerves and rarely is
severe enough to require narcotic administration.
Psychological complications are also commonplace in
patients undergoing limb lengthening by these techniques.
Depression is common but usually responds well to temporary anti-depressant medication.19 Similarly, patients often
report difficulty sleeping, loss of appetite, and unintentional
weight loss. All of these psychological complications usually resolve spontaneously within 1 week of stopping the
distraction.19
The Use of Distraction Osteogenesis
Distraction osteogenesis has been applied to the treatment
of a wide variety of problems including severe limb length
discrepancy, acquired and congenital deformities, fracture
nonunion, and osteomyelitis.14,15,29 Regardless of the reason
for use, the general technique remains unchanged: bone division, stable fixation of the fragments, a 7 to 14 day latency
period, distraction, consolidation, assessment of regenerate
bone, and removal of the frame.7,23,28,30,31 Care must be taken
to allow for at least 2 to 3 days of consolidation for each
day of distraction. Prior to removal of the frame, a careful
assessment of the regenerate and docking site, if present,
is required.
Similarly, this technique may also be applied in acute
limb shortening followed by limb lengthening.23,32-34 The
theoretical advantage of this technique is that it will allow
for faster healing of a traumatic defect as it does not require
waiting until docking is achieved to begin callous healing.
Shortening assists with the closure of soft tissue defects,
though it may result in soft tissue redundancy and swelling.
These techniques can be readily applied to the treatment
of various types of nonunions. Atrophic nonunions may be
treated with bifocal osteosynthesis, which involves resection of the nonunion site, compression at the nonunion site,
and bone lengthening at an osteotomy site remote to the
nonunion site.28,35 This technique also allows for alignment
if deformity is also present.
Hypertrophic nonunions have traditionally been treated
by revision to rigid fixation. These fractures have a vital
blood supply from each bone end and a dense collagenous
interface. These characteristics allow the nonunion to be
treated by stimulating bone formation with primary distraction and realignment when necessary.36 Nonunions with bone
loss can be transported with bone transport or shorteningdistraction.28,37
Infected nonunions require resection of the focus of infection, with removal of all necrotic and poorly-vascularized
tissues.28 The remaining osseous segments must have an adequate blood supply to promote bone formation at its trailing
end and healing at its leading end.11 Bone transport can then
subsequently be used to eliminate the residual defect. When
compared to treatment with bone graft, antibiotic beads,
and vascularized bone grafts, patients who are treated with
bone transport experience similar rates of healing, duration
of treatment, final deformity, complication rates, and total
number of operative procedures.22,24,28,38 However, patients
who undergo bone transport have improved limb length discrepancy, decreased cost of treatment, and shorter duration
of disability than those treated with bone graft, antibiotic
beads, and vascularized bone graft.22,28
The benefits of treating nonunions with bone transport
include the ability to achieve regeneration of living bone
with the same strength and width as that of native bone.28
In addition, this technique can be used to treat very large
defects, up to 30 cm, in both children and adults.39 Moreover,
this technique allows for simultaneous deformity correction
as well as allowing for the treatment of concomitant soft
tissue problems.
Unfortunately, bone transport is not the answer for all
nonunions. Its use requires specialized training and equipment. Frequently, bone transport requires a long treatment
duration during which numerous complications may occur.
This technique can also be costly. A 1994 cost analysis
determined that the cost of limb salvage using the Ilizarov
technique was $60,000 compared with $30,000 for an acute
amputation, although this does not take into account lifetime
prosthetic costs.40
Conclusion
Surgical limb lengthening and bone transportation techniques have undergone significant evolution over the past
century. While numerous potential complications continue
to exist, most complications are now minor and easily treatable. Distraction osteogenesis has become a viable treatment
option when applied in a cooperative patient by a surgeon
with appropriate training. Advances in technique continue
to be made, and the introduction of new devices has made
ring external fixation a more accessible treatment option.
Disclosure Statement
None of the authors have a financial or proprietary interest
in the subject matter or materials discussed, including, but
not limited to, employment, consultancies, stock ownership,
honoraria, and paid expert testimony.
References
1. Aronson J, Harrison BH, Stewart CL, Harp JH Jr. The histology of distraction osteogenesis using different external
fixators. Clin Orthop Relat Res. 1989 Apr;(241):106-16.
2. Garcia FL, Picado CH, Garcia SB. Histology of the regenerate
and docking site in bone transport. Arch Orthop Trauma Surg.
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