of the KneeAbstract Osteochondritis dissecans is a condition of the joints that appears to affect subchondral bone primarily, with secondary effects on articular cartilage.. This theory
Trang 1of the Knee
Abstract
Osteochondritis dissecans is a condition of the joints that appears
to affect subchondral bone primarily, with secondary effects on articular cartilage With progression, this pathology may present clinically with symptoms related to the integrity of the articular cartilage Early signs, associated with intact cartilage, may be related to a softening phenomenon and alteration in the mechanical properties of cartilage Later stages, because of the lack
of underlying support of the cartilage, can present with signs of articular cartilage separation, cartilage flaps, loose bodies, inflammatory synovitis, persistent or intermittent joint effusion, and, in severe cases, secondary joint degeneration Selecting and recommending a surgical intervention require balancing
application of nonsurgical interventions with assessment of the degree of articular cartilage stability and the potential for spontaneous recovery
The etiology of osteochondritis dissecans (OCD), in contrast to its etymology, remains unclear Al-though also described by Pare and Paget, the disease was named by Konig1in 1888, who by his nomen-clature indicated an inflammatory basis to explain a phenomenon of loose bodies in the joint.1,2No theory regarding the cause of OCD is uni-versally accepted, even though, as Konig later recognized, an inflamma-tory origin is unlikely Repetitive mi-crotrauma, secondary effects associ-ated with vascular insufficiency, and potentially inherited factors remain important areas for investigation and clarification Classification of OCD
in the knee involves identification of
a specific location, potential frag-mentation and/or displacement, and the status of the growth plate (Table 1) Skeletal age at onset of symptoms appears to be the most important
de-terminant of prognosis and remains
an essential factor, directing the tim-ing and nature of treatment deci-sions Confusion regarding the etiol-ogy, treatment, and natural history of these lesions is compounded by the common practice of referring to both osteochondritis dissecans and osteo-chondral defects (which can be sec-ondary to osteochondritis dissecans
or to traumatic osteochondral frac-ture) as OCD
Incidence of OCD has been esti-mated at between 0.02% and 0.03%, based on a survey of knee radio-graphs, and at 1.2%, based on knee arthroscopy.3,4The highest rates ap-pear among patients aged between
10 and 15 years Male-to-female ra-tio historically is approximately 2:1 Bilateral lesions, typically in differ-ent phases of developmdiffer-ent, are re-ported in 15% to 30% of cases, man-dating assessment of both knees in
Dennis C Crawford, MD, PhD
Marc R Safran, MD
Dr Crawford is Assistant Professor,
Sports Orthopaedic and Arthroscopic
Surgery, Department of Orthopaedics
and Rehabilitation, Oregon Health &
Science University, Portland, OR.
Dr Safran is Associate Professor and
Director, Sports Medicine, Department
of Orthopaedic Surgery, University of
California, San Francisco, San
Francisco, CA.
None of the following authors or the
departments with which they are
affiliated has received anything of value
from or owns stock in a commercial
company or institution related directly or
indirectly to the subject of this article:
Dr Crawford and Dr Safran.
Reprint requests: Dr Safran,
Department of Orthopaedic Surgery,
University of California, 500 Parnassus
Avenue, MU 320W, San Francisco, CA
94143-0728.
J Am Acad Orthop Surg
2006;14:90-100
Copyright 2006 by the American
Academy of Orthopaedic Surgeons.
Trang 2all patients presenting with this
di-agnosis.5
Etiology
Lesions described as OCD can be
caused by several factors, the
signif-icance of which may vary depending
on the area of the knee affected.1,6
The essential mechanisms
responsi-ble are divided into constitutional or
hereditary, vascular, and traumatic
Constitutional Factors
may represent a variation or
sub-group of epiphyseal dysplasia and
thus may display a similar
inheri-tance pattern One report of familial
predisposition to OCD-type lesions
supports this idea;8however, Petrie,9
in a study showing minimal
trans-mittance to first-degree relatives,
found limited evidence for a genetic
pattern and suggested that the usual
presentation is not familial Despite
this determination, an association of
OCD has been found with a variety
of inherited conditions, including
dwarfism (described only as “short
stature”), tibia vara,
Legg-Calvé-Perthes disease, and Stickler’s
syn-drome.5
The relationship between the
na-ture of developing OCD lesions,
pos-sible hereditary factors, and the
po-tential for abnormal ossification of
the growth plate remains uncertain
Abnormalities of epiphyseal
matura-tion are common and typically
re-solve without long-term sequelae
Distinguishing normal ossification
centers of the distal femur is critical
in evaluating the young patient with
knee pain Caffey et al10describe the
presence of irregularities of
ossifica-tion in the distal femoral growth
plates as the rule and explain them
as an imbalance between rapid
carti-lage proliferation and ossification
These areas are typically benign,
re-solve without sequelae, and should
not be confused with OCD lesions
Some investigators, however, have
might separate from these epiphys-eal areas and subsequently act as the precursors for OCD lesions.9,11More recent data from equine OCD stud-ies suggest a role for elevated matrix-metalloproteinase activity in
predisposition to this condition is manifest in genetic inheritance is likely to prove to be multifactorial
Vascular Factors
Analogous pathophysiology be-tween osteonecrosis and OCD con-stituted a popular theory for
etiolo-gy among many early investigators (eg, Paget, Ficat, Enneking).2 En-neking specifically championed a theory centered on poor end-arterial cascades in the distal femur and a predisposition for this bone to
devel-op and behave in a manner analo-gous to a sequestrum Often cited as evidence against this hypothesis is
an anatomic study of 200 adult, 16 newborn, and 4 “juvenile” femurs that indicated extensive vascular anastomosis.14 Further proof is found in another study that exam-ined six detached lesions from pa-tients with diagnosed osteochondri-tis with no histopathologic evidence
of osteonecrosis.11Despite these in-vestigations, several recent reports have suggested that the cause is a paucity of vascular supply to the me-dial femoral condyle subjacent to the posterior cruciate ligament inser-tion, an area most commonly
OCD.15,16Similarly, Linden and Tel-hag17 demonstrated limited uptake
of tetracycline and radionucleotide
in 14 adults with OCD lesions and
so concluded that the reparative pro-cess of subchondral bone was
arrest-ed at a fibrocartilage stage, possibly the result of poor blood supply
Traumatic Factors
A history of injury is reported in
as many as 40% of patients with OCD, although some studies suggest
a far more limited role for direct in-jury.18 Cahill and colleagues19,20 found no specific history of direct trauma among 204 patients in whom they attributed the pathology
to a stress fracture This theory is based on the unproven hypothesis that a series of pathologic reactions within articular cartilage and sub-chondral bone occur secondary to re-petitive microtrauma and yield a chronic osteochondral injury that manifests as an OCD lesion Shear forces particular to the lat-eral aspect of the medial femoral condyle may be a contributing fac-tor Fairbank21 described repetitive impingement from the tibial spine
as causal for OCD of the lateral as-pect of the medial femoral condyle
In this hypothesis, supported by bio-mechanical studies later performed
caused by impingement are
generat-ed as the knee rotates mgenerat-edially with
Table 1
Imaging and Arthroscopic Criteria for Classifying Osteochondritis Dissecans Lesions in the Knee
Radiographic
Magnetic Resonance
Open vs closed physis Location of lesion Size of lesion Presence of loose bodies
Low signal between the osseous fragments Low signal breaching the cartilage Focal defect≥5 mm
Stable: Cartilage softening, cartilage breach
Unstable: Cartilage flag tears, osteochondral loose body
Osteochondral defects
* T2-weighted (fluid-weighted) sequence
Trang 3loading in flexion Smillie23also
fa-vored this hypothesis, citing factors
that could increase contact forces,
including meniscectomy, instability,
genu recurvatum, and condylar
flat-tening Several investigators
subse-quently have shown an association
between discoid lateral meniscus
and the less common lateral femoral
condylar lesion.24-26Specifically, the
amount of direct microtrauma or
macrotrauma necessary to produce
an osteochondritis cannot be
ascer-tained from the literature What is
clear is that distinguishing
osteo-chondral fractures that fail to unite
from lesions of OCD based on static
radiographic and histologic evidence
has proved to be difficult and
re-mains controversial
Smillie23distinguished two
essen-tial forms of OCD, juvenile and
adult, and suggested unique
etiolo-gies In the variety manifested in the
skeletally immature individual, there
may be a fundamental disturbance of
the epiphyseal development, with
re-sultant formation of small accessory
areas of subchondral bone that
sepa-rate from the principal ossification
center of the epiphyseal plate
Min-imal trauma, whether repetitive
mi-crotrauma or direct mami-crotrauma,
then may cause osteonecrosis within
this region, as separation of the
frag-ments disturbs the balance of oxygen
tension necessary for ossification In
contrast to this type of
developmen-tal etiology, Smillie postulated a
more direct traumatic causation for
the adult form
Clinical Presentation
Cahill19 and Mubarak and Carroll8
emphasized a distinction between
the juvenile and adult types of OCD,
based on the osseous age of the
pa-tient at the time of symptom onset
Those with open physes are
consid-ered to have juvenile-onset OCD,
whereas those with skeletal maturity
are considered to have the adult
form Cahill19reported cases of
adult-onset OCD in which radiographs
taken during childhood did not reveal OCD Later, during adulthood, the patients did have radiographically ap-parent OCD However, the patients presented by Cahill likely had child-hood OCD that may not have been apparent on the plain radiographs, possibly because of the position of the lesion relative to the angle of the knee during radiography It has clearly been shown that OCD (in the
“classic” location, the lateral aspect
of the medial femoral condyle) may
be missed on posteroanterior radio-graphs with the knee in full exten-sion, yet may be visualized on flexed-knee views.26Adult-onset OCD may simply be a delayed onset of previ-ously asymptomatic juvenile OCD that failed to heal and presents later with loosening and joint degenera-tion
Early presentation often encom-passes poorly defined complaints
Pain is generalized to the anterior knee, with variable amounts of swelling that is typically intermit-tent Anecdotal but consistent re-ports suggest an association between periods of increased activity and ep-isodes of swelling and effusion An effusion may be found in association with joint synovitis and does not necessarily reflect a loose osteocarti-laginous fragment The true source
of this synovitis and/or effusion is elusive In patients with more ad-vanced OCD, persistent swelling or effusion may be accompanied by catching, locking, or giving way In late-stage disease, the sensation of a loose body is often described
Physical findings may be
correlat-ed with the area of the lesion Wil-son27describes an external rotation
of the tibia during gait as signifying compensation for impingement of the tibial eminence on an OCD le-sion of the medial femoral condyle
Wilson’s test involves reproduction
of pain on examination by
internal-ly rotating the tibia during extension
of the knee between 90° and 30°, then relieving the pain with tibial external rotation The presumption
is that, in internal rotation and ex-tension, the tibial eminence
imping-es on the OCD limping-esion, causing pain, and that external rotation moves the eminence away from the lesion, re-lieving the pain A recent case series has shown a poor predictive value of this maneuver with radiographically proven OCD.28 However, the same authors suggest use of this maneu-ver, when it is initially positive, as a tool for following disease resolution Standard techniques for testing sta-bility and joint palpation are neces-sary to identify concurrent
patholo-gy, including loose bodies, associated meniscal tears, malalignment, and ligamentous injury
Imaging Studies
Characterizing the lesion type and assessing growth plate status typically begins by making standard weight-bearing anteroposterior and lateral radiographs of both knees Lateral radiographs allow recogni-tion of a relatively anteroposterior lesion location and identification of normal, benign accessory ossifica-tion centers in the skeletally imma-ture knee, as described by Caffey et
al.10 An axial view can be added when lesions of the patella or troch-lea are suspected In addition, the ra-diographic “notch view,” taken with the knees bent 30° to 50°, may help identify the lesions in the posterior condyles
Plain radiographs provide initial data to determine lesion size, pres-ence or abspres-ence of sclerosis, poten-tial dissection, and assignment to one of several classification systems Cahill and Berg29describe a method
of localizing lesions by dividing the knee into 15 distinct alphanumeric zones (Figure 1) From medial to lat-eral, five zones numbered 1 through
5 are divided centrally by the notch; each compartment is then divided in half The lateral radiograph uses Blu-mensaat’s line anteriorly and the posterior cortical line to divide zone
A (anterior) from B (central) and C (posterior) This alphanumeric
Trang 4sys-tem provides standardization for
re-search purposes, although it has
date.6,26
Cahill and Berg29also describe a
classification system for juvenile
OCD based on technetium Tc 99m
phosphate scintigraphy findings
Grading is based on the relative
de-gree of scintigraphic activity in
rela-tion to plain radiographs Stage 0 is
normal in both Stage 1
demon-strates a defect on plain radiographs
but no increased activity on the bone
scan Stage 2 shows increased uptake
in the lesion but not in the adjacent
femoral condyle Stage 3 indicates
isotope uptake in both the lesion and
the adjacent condyle Finally, stage 4
demonstrates increased isotope
up-take in both the lesion and adjacent
tibial surface Patients with stage 3
or 4 disease were described as having
symptomatic OCD Cahill et al20
lat-er reported limited correlation
be-tween this staging system and
pre-diction of lesion stability or the need
for subsequent surgery However,
Paletta et al30 suggested a role for
this imaging technique that
distin-guishes between results in juveniles
and those in adults They reported
that four of four patients with open
physeal plates and increased activity
on bone scan healed with
nonsurgi-cal treatment, whereas the two
pa-tients without increased activity did
not heal In contrast, among patients
with closed growth plates, only 33%
(2/6) healed despite having similar
increased activity within the
le-sion
(MRI) has proved to be particularly
valuable in assessing osteochondral
lesions Several investigators have
attempted to characterize the
stabil-ity of the OCD lesion with findings
on MRI Dipaola et al31classified
le-sions according to appearance on
MRI and associated specific findings
with the potential for fragment
de-tachment They described lesions
containing fluid behind the joint as
partially or completely detached, as
evidenced by high signal intensity
on T2-weighted images when a breach of the cartilage surface was detected They distinguished carti-lage breach with an attached frag-ment by interpreting interposed low signal intensity on the rim as fibrous tissue (Figure 2)
Others have added criteria for fragment instability to include the following: an area of increased ho-mogenous signal≥5 mm in diameter beneath the lesion; a focal defect≥5
mm in the articular surface; and a high signal line traversing the sub-chondral plate into the lesion.32 In cases of limited joint effusion, Kramer et al33expressed a high level
of confidence for predicting lesion stability using intra-articular gado-linium Gd 153 contrast material
More recent advances in MRI
tech-nology (eg, cartilage-specific se-quences) may eliminate the
necessi-ty of intra-articular injections and allow distinction between areas of interposed synovial fluid, fibrocarti-lage, and degenerated or lytic sub-chondral bone
Classification and Characterization
Distribution of OCD lesions in the knee are most commonly associ-ated with the lateral aspect of the medial femoral condyle Aichroth26 described this as the classic location and confirmed it in 69% (72) of 105 knees (Figure 3) The patella was in-volved in five patients (5%); the re-mainder of the lesions involved the lateral femoral condyle (15% [16]) and the medial femoral condyle (69% [72]) In a large multicenter
ret-Figure 1
Anteroposterior (A) and lateral (B) views of the knee, demonstrating the 15
alphanumeric radiographic regions described by Cahill and Berg.29The five numbered zones on the anteroposterior view are divided centrally by the notch (zone 3) The lettered zones on the lateral view are divided by Blumensaat’s line anteriorly and the posterior cortical line The half-moon–shaped shaded area in each view of the distal femur represents an old lesion (Adapted with permission from Cahill BR, Berg BC: 99m-Technetium phosphate compound joint scintigraphy in the management of juvenile osteochondritis dissecans of the femoral condyles
Am J Sports Med 1988;11:329-335.)
Trang 5rospective study of 713 patients and
798 knees, Hefti et al5 described a
slightly different distribution The
medial femoral condyle was
typical-ly affected, with the majority of
le-sions involving the lateral aspect
(51%), 19% the central, and 7% the medial aspect Involvement of the lateral condyle in all areas encom-passed 17% of lesions; those of the patella, 7%; and 0.2% (one lesion), the tibial plateau Lateral condylar
lesions are more commonly associ-ated with discoid meniscus or with
sur-gery.26,34 Knee radiographs provide not only the initial basis for distinction of growth plate maturation but also as-sessment of lesion location and sta-bility (ie, free or loose bodies) Berndt and Harty35described four stages of chondral lesions based on plain ra-diographs of the talus; this system has been widely applied to lesions about the knee: stage I, involvement
of a small area of compression of the subchondral bone; stage II, partially detached osteochondral fragment; stage III, completely detached frag-ment that remains in the underlying crater; and stage IV, complete detachment/loose body Other crite-ria, such as lesion size, have been used to assess the potential for heal-ing with nonsurgical intervention Several authors20,32,36 have thought that patients could be successfully treated nonsurgically when the mean area was smaller than between
194 and 424 mm2 In contrast, le-sions larger than between 436 to 815
mm2were associated with poor out-comes Others have suggested the presence of “marked sclerosis” as a poor predictor of successful nonsur-gical management.37-39
Understanding and characterizing the spectrum of OCD lesions as sta-ble or unstasta-ble is often considered central to the treatment plan
proved to be difficult to determine prior to surgical intervention and of-ten remains a clinical judgment MRI criteria have proved to be rea-sonably accurate compared with the gold standard of arthroscopic find-ings in predicting lesion integrity Strict adherence to the MRI criteria
of Dipaola was shown in one study40to have an 85% correlation with arthroscopic findings when ap-plying Guhl’s arthroscopic staging system Guhl’s intraoperative classi-fication is defined by cartilage integ-rity and fragment stability.37Type I
Figure 2
Sagittal MRI scans of unstable osteochondritis lesions of the distal femur
T2-weighted (fluid-T2-weighted) images of osteochondral separation are indicated by high
signal line between the osseous components (A) and extending from the
intraosseous portion to the joint surface, “breaching” the cartilage (B).
Figure 3
Anteroposterior radiographs demonstrating an OCD lesion on the lateral aspect of
the medial femoral condyle before (A) and after (B) displacement.
Trang 6represents softening of cartilage but
no breach; type II, breached cartilage
that is stable; type III, a definable
fragment that remains partially
at-tached (flap lesion); and type IV, a
loose body and osteochondral defect
at the donor site
Further surgical characterization
of OCD lesions, however, should not
be limited to this system
Assess-ment of the size and number of loose
fragments, the presence of bone
as-sociated with each chondral
frag-ment and its potential reparability,
and the quality and character of the
underlying subchondral bone
(pres-ence of fibrocartilage or cystic
de-generative material) are important
factors in characterizing and
surgi-cally treating this heterogenous
pa-thology
Natural History and
Prognosis
No randomized, controlled clinical
trials exist for either surgical or
non-surgical interventions for OCD of
the knee In general, physeal
maturi-ty, dissection of the lesion from the
adjacent subchondral bone
(stabili-ty), size and location of lesions, and
integrity of the cartilage surface
have been used as predictive criteria
for surgical intervention
Historical-ly, data from case reports, case
se-ries, and retrospective reviews have
directed care of patients with OCD
of the knee Thus, caution should be
exercised in proceeding with
recom-mendations from these studies
be-cause they provide only a limited
ability to predict the natural history
of OCD; that is, they are level IV and
V evidence-based studies
A large, recent multicenter
re-view of the European Paediatric
Or-thopedic Society study (509 knees
[318 juvenile, 191 adult] in 452
pa-tients) has provided notable data.5
The authors made several important
distinctions and reached a number of
conclusions (1) When there are no
signs of dissection (defined as a
sta-ble fragment), the prognosis is
mark-edly better than it is with signs of dissection (2) Pain and swelling are not good indicators of dissection (3) Plain radiography and computed to-mography are not useful in predict-ing dissection (4) Sclerosis on plain radiography predicts poor response
to drilling (5) Lesions >2 cm in di-ameter have a worse prognosis than smaller lesions (6) When there is ev-idence of dissection, surgical results are better than those of nonsurgical treatment (7) Lesions in the classic location had a better prognosis (8) Although patients with adult-onset symptoms had a higher proportion
of abnormal findings on radiographs after the treatment period (42%), more than one in five of those with open epiphyseal plates (22%) had ab-normal knee radiographs an average
of 3 years after starting treatment
Pill et al6recently compared the value of MRI and clinical criteria for predicting the success of nonsurgical treatment of OCD Their retrospec-tive review correlated outcomes to radiographic measures using the MRI criteria of DeSmet et al32 and the radiographic criteria of Cahill and Berg.29Although they found no single factor to be uniformly predic-tive of successful nonsurgical treat-ment, several important associa-tions were found Older patients with one or more signs of chondral disruption by MRI failed nonsurgical treatment most often Similarly, larger lesions and lesions deemed to
be within the weight-bearing area, as indicated by the lateral radiograph, also were most likely to fail nonsur-gical treatment Younger patients with no MRI criteria for instability were most likely to recover with nonsurgical treatment
Management and Outcomes
An algorithm for management deci-sions is given in Figure 4 The goal of nonsurgical treatment is to promote healing of lesions in situ and prevent lesion displacement The preferred
surgical goals are salvage of native cartilage, when possible, followed by restoration procedures
Initial discussion in early OCD involves patient, family, and physi-cian education Understanding the nature of this disease, the potential long-term implications, and the timeline for management are crucial early strategies to help both the pa-tient and surgeon avoid frustration Symptoms that are exacerbated by activity, particularly episodes of trauma and athletic and weight-bearing activities, should be identi-fied Significantly limiting sports and high-impact activities is univer-sally recommended
Nonsurgical treatment is
primari-ly mitigated through activity modi-fication It may include a wide spec-trum of approaches that historically have included crutches (for limited weight bearing) as well as braces or even casts for noncompliant pa-tients The efficacy of limiting activ-ity compared with limited or non– weight-bearing activity has not been studied in a controlled trial Sales de Gauzy et al38followed a group of 30 children (mean age, 11 years 4 months) to complete resolution of symptoms by discontinuing sports activities; the authors recommended
no surgical intervention because symptoms resolved with discontinu-ation of sports activities In patients without marked sports participa-tion, prescribing a non–weight-bearing status and range-of-motion knee exercises may be beneficial to cartilage and may help avoid the po-tential disaster of “cast disease” (eg, joint stiffness, muscle atrophy, os-teoporosis) and arthrofibrosis associ-ated with cast immobilization Symptom relief may be gained with nonsteroidal anti-inflammatory drugs (NSAIDs), but doing so may in-terfere with monitoring disease pro-gression In young patients with ra-diographically and clinically stable lesions, we prefer to control pain with a non–anti-inflammatory med-ication (eg, acetaminophen) This
Trang 7avoids the theoretical negative
influ-ence of NSAIDs on bone healing In
this strategy, we record days with
swelling and those without and plot
trends versus compliance with
peri-ods of inactivity This semiobjective,
patient-reliant practice helps support
recommendations for reduced
activ-ity over a potentially long period of limited intervention For patients with persistent pain or continued ep-isodes of swelling/effusions, deci-sions about surgical intervention may be supported by the data In adults without evidence of loose fragments or unstable lesions, we
employ a strategy similar to that used for patients with early, focal os-teoarthritis Pain medication, activ-ity modification, strengthening, and weight control are the central tenets Concurrent pathology (ie, malalign-ment, instability, osteoarthritis) is more likely in older patients and is
an important consideration for both surgical and nonsurgical manage-ment of OCD
Choosing surgical intervention for OCD, and selecting a strategy for repair versus reconstruction or re-moval of osteochondral lesions, es-sentially depend on the stability of the inciting lesion and the integrity
of the overlying cartilage With fail-ure of the nonsurgical approach, sur-gical management often begins with arthroscopy Classification using ar-throscopic findings is based on a de-scription of the lesion using two es-sential criteria: the integrity of the overlying articular cartilage and the stability of the lesion to distinguish three categories (intact, not intact but stable, not intact and unsta-ble).19,37Lesions with intact cartilage are considered either stable or unsta-ble Lesions with damaged cartilage surfaces comprise a mixture of ad-vanced lesions and may be either disrupted or macerated, and by hill’s definition are unstable
unstable-cartilage, injured lesion as predetached, hinged, or loose, attrib-uting characteristics of temporal symptoms and reduction congruity
to each Using this system, he rec-ommended a treatment algorithm, based on arthroscopic findings and scintigraphic data We employ a sim-ilar approach using symptoms, ra-diographic and MRI findings, and ar-throscopic observations to apply treatments based on skeletal
maturi-ty, osteochondral stability and re-ducibility, and articular cartilage in-tegrity (Figure 4)
Surgical treatment for stable le-sions with normal articular cartilage involves drilling the subchondral bone with the intention of
stimulat-Figure 4
Juvenile
(open physis) Radiographs (closed physis)Adult
Stable
Physical examination
Stable
MRI
Stable
Bone scan
Activity restriction (3 mos)
• Impending physeal closure
• Clinical signs of instability
• Expanding lesion on plain films
Arthroscopy
Stable
Physical examination
MRI
Stable
Malalignment
Yes
Treat symptomatically
Stable
Unstable
Osteotomy
Stable Unstable
reducible
Fixation graft
Fixation and graft
chondrocyte transplant, or osteochondral graft
Not positive
No Positive
Unstable with fragmentation
or osteolysis
Unstable and chondral damage
Fixation and grafts, Transchondral
drilling
Treatment algorithm for knee osteochondritis dissecans
Trang 8ing vascular ingrowth and
subchon-dral bone healing Retrograde
tech-niques (defined as methods that
avoid articular cartilage disruption
using a transosseous approach) have
given way to arthroscopically
assist-ed methods that have provassist-ed to be
highly efficacious in skeletally
im-mature patients Anderson and
col-leagues39,41 described success with
this technique in 24 patients
fol-lowed for an average of 5 years
Av-erage time to healing was 4 months
Twenty-two patients had good or
ex-cellent results based on the
Hugh-ston rating scale; in two of four
skel-etally mature patients, the lesion did
not heal
Kocher et al42treated 30 knees in
23 skeletally immature patients who
had failed 6 months of nonsurgical
therapy (average age, 12.3 years)
Us-ing arthroscopically directed
ante-grade (transchondral) drilling of
sta-ble lesions, the authors reported
radiographic healing in all 30 knees
at an average of 4.4 months They
advocated this treatment in patients
with intact articular surfaces who
had failed nonsurgical treatment
Our experience has been the same,
that drilling works better in
skeletal-ly immature patients than in older
patients, although it is still worth
at-tempting in all patients with a
per-sistently symptomatic lesion and
in-tact articular cartilage
Surgical treatment for unstable
lesions typically is attributed to
Smillie23because he developed a nail
for open reduction and internal
fixa-tion of displaced and unstable
le-sions Surgical intervention to
en-hance union has included Kirschner
wires, cannulated screws, Herbert
screws, and bone pegs These
typi-cally require a second surgery to
re-move the device and have been
asso-ciated with several complications,
including wire migration, adjacent
cartilage damage, and implant
frac-ture Biodegradable implants (ie, pins
and screws) have the potential
ad-vantage of not requiring removal;
however, some of these devices have
been associated with sterile abscess formation, synovitis, and loss of fix-ation.43Compressive devices provide the possibility of loading the osseous components, a technical advantage that may facilitate healing (Figure 5, E) When indicated, hardware re-moval often can be done arthroscop-ically, with low morbidity, and can provide an opportunity to directly assess healing and cartilage integrity
Simple removal of a loose or de-tached fragment is rarely considered
to be an effective treatment, aside from cases in which the fragment is macerated and irreparable Wright et
al44reported only 35% good and ex-cellent results with fragment exci-sion at an average of 9 years after surgery
In cases in which simple trans-chondral drilling is unsuccessful, or when the lesion is hinged, loose, or displaced, the objective is to restore articular congruency by stimulating subchondral bone repair via com-pression and bone grafting, when necessary In this manner, the os-seous portion of the fragment may heal and allow stabilization of the overlying articular surface This strategy also would provide protec-tion to the adjacent uninjured carti-lage that, after fragment excision, could be subject to increased contact stress and shear forces secondary to surface irregularity, step-off, and re-sultant edge loading Green18used a similar argument to suggest that the technical difficulty of repairing loose fragments and subsequent malreduc-tion could have similar
consequenc-es His advice, which remains a te-net of joint surgery, was to replace larger fragments and remove those that were essentially too small to be fixed anatomically Cahill19
similar-ly advocated fixation whenever pos-sible because the results of excision usually are ineffective
Discrepancy in the size of a lesion
as a result of overgrowth of displaced fragments, loss of fragment substance because of mechanical damage, or craterization of the donor site all have
been described and provide technical challenges Several strategies have been described to address these poten-tial issues Johnson et al45treated 35 knees via an arthroscopically assisted technique that involved fragment fix-ation using cannulated AO-type screws Results, comparable with other in situ methods, were good or excellent in 90% of cases
When poor congruency of the fragment-donor interface exists, a technique similar to that described
by Anderson et al41may be used In this method, the lesion is evaluated arthroscopically, followed by ante-grade open curettage, grafting, reduc-tion, and fixation (Figure 5, C and D) This method is done by reflecting a partially attached fragment, or re-moving it temporarily, to allow in-spection of the osseous surfaces and removal of fibrocartilage from the op-posing subchondral interface The ensuing fragment-crater mismatch then can be grafted with autogenous bone (tibial metaphysis) before com-pression screw fixation We have used cannulated Acutrak (Acumed, Hillsboro, OR) headless screws or a 4.0-mm headed screw countersunk 1
to 2 mm below the cartilage surface
to avoid causing articular cartilage le-sions on the opposing surface Fol-lowing a period of strict non–weight-bearing and range-of-motion exercise, hardware is removed arthroscopically after a minimum of 6 weeks to as long as 12 weeks
Several techniques for salvage of full-thickness defects of articular
chondrocyte implantation, mosaic-plasty, and osteochondral allograft, have been advocated Browne and Branch46 have presented an algo-rithm for approaching these types of injuries The efficacy of their tech-niques for addressing the symptoms
of advanced OCD has been mixed Some have advocated fixing loose osteochondral fragments with autol-ogous osteochondral autografts or by using autologous osteochondral au-tografts for filling empty craters to
Trang 9decrease edge loading Case reports
have indicated generally favorable
results for these procedures but have
limited follow-ups Yoshizumi et
al47 describe successful union by 6
months in three cases of adult OCD
using a modification of a method
de-scribed by Berlet et al.48In the Berlet
technique, the OCD lesion is
essen-tially fixed in situ by applying
pe-ripheral autologous osteochondral plugs However, Yoshizumi et al47 describe a technique using one cen-tral plug to fix the lesion Others have advocated using either tech-nique to reduce edge loading
Anoth-er method for unloading cartilage for adult OCD patients was described
by Slawski.49 He performed seven valgus osteotomies for medial
femo-ral condyle OCD and, at 2 years, de-scribed an average improvement in the Lysholm score from 39 to 89, with an average postoperative knee angle of 9º valgus
Use of autologous chondrocyte transplantation has been discussed and advocated by several authors Peterson et al50reviewed their expe-rience with autologous chondrocyte
Figure 5
Surgical reduction and fixation of an unstable osteochondritis dissecans
injury A, Preoperative anteroposterior
radiograph demonstrating a loose and fragmenting chondritis dissecans
of the medial femoral condyle B,
Intraoperative photograph indicating the margin (dotted area) of the extent of the loose/unattached articular
cartilage C, The osteochondral
fragment is elevated The fibrocartilage has been débrided from the interval between the osseous component prior
to bone grafting D, Fixation with two
compression screws and absorbable
pins E, Postoperative anteroposterior
radiograph
Trang 10implantation in 94 patients at a
min-imum of 2 years; 18 patients (19%)
had chondral defects secondary to
OCD Defects in this group were
characterized as particularly
recalci-trant to previous surgery and often
required a longer period to mature,
compared with the other articular
le-sions studied Interestingly, 89% of
patients (16/18) improved, with a
similar distribution of excellent,
good, and fair results compared with
condyle lesions
Subsequently, these authors51
re-ported results of 58 patients with a
variety of OCD lesions Results at a
mean of 5.6 years were similar to
those at a minimum of 2 years in the
previous study.50 Interestingly, in
this larger study, a small group of
pa-tients received bone graft for
sub-chondral defects to provide a
chon-drocyte bed prior to transplantation
Results of autologous osteochondral
and allograft transplantation are
gen-erally difficult to interpret;
indica-tions in most studies for such
proce-dures involve a variety of conditions,
including osteonecrosis,
osteoarthri-tis, trauma, osteochondral fracture,
and OCD
Summary
Understanding of the origins and
natural history of OCD of the knee
continues to progress Two principle
factors, skeletal maturity at
symp-tom onset and contiguity of the
sub-chondral and bone-cartilage surface,
remain the most important
determi-nants in choosing treatment The
challenge is identifying those
deter-minants within the spectrum of
dis-ease (eg, who may benefit from
longer periods of nonsurgical
man-agement versus earlier surgical
treat-ment) OCD is not a benign
immature knee Despite the fact that
many patients are asymptomatic,
the potential for arthrosis and
degen-eration, demonstrated
radiographi-cally, remains a problem, the exact
consequences of which remain un-certain Additional significant chal-lenges include dissecting and defin-ing the different subtypes of OCD, determining the potential of each for spontaneous healing or progression, and improving opportunities and techniques for intervention to main-tain and restore joint integrity
References
Evidence-based Medicine: The au-thors note that there are no Level I or Level II evidence-based studies
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