Journal o f Sport Rehabilitation, 2014, 23, 216-222 http://dx.dOi.Org/10.1123/JSR .2013-0047 © 2 0 1 4 Human Kinetics, Inc.
Management of Osteochondritis Dissecans of the Knee Simon M. Thompson, Mary Jones, Jonathon R. Lavelle, and Andy Williams The etiology of osteochondritis dissecans is hypothesized as repetitive microtrauma, resulting in an interruption of blood supply. Due to the location of the most common lesions on the medial femoral condyle, impinge ment of either the medial tibial spine or inferior pole of the patella against the adjacent medial femur may be responsible. It is much more common in athletic males than other groups. This article reviews the current treatment options for lesions around the knee.
Keywords: cartilage, surgery, OCD, rehabilitation Osteochondritis dissecans (OCD) is a disorder of subchondral bone that can affect the overlying articular cartilage. Advanced lesions may separate, causing pain and mechanical symptoms. Although OCD was first described in 1738, its etiology, natural history, and man agement are still not fully understood. OCD is commonly divided into juvenile and adult forms. It is classed as juvenile OCD when it presents in a skeletally immature patient with an open physis of the involved bone. It affects 15 to 29 people per 100,000 of the general population each year, with the knee being the most commonly involved joint.1It is most frequently seen between the age of 13 and 21 and is more common in males by a ratio of 5:3.2 However, it is thought that greater partici pation in competitive sport by children is resulting in OCD at a younger age and also increasing its prevalence in girls.3 Juvenile OCD lesions are often stable, with an intact articular surface, and have the greatest potential to heal with conservative treatment, whereas adult OCD lesions are more likely to be unstable (ie, separated) and require surgery and have a worse prognosis. However, even in juvenile OCD the failure rates o f conservative treatment have been reported as over 50%.4 The early identification and treatment of OCD in the knee are therefore essential to optimize healing potential and outcome, as OCD lesions that do not heal can lead to premature joint degeneration. After a brief overview of OCD this article aims to describe its management based on the disease stage of OCD at diagnosis.
Etiology OCD was originally named by Konig in 1887,5 who believed it to occur as a result of inflammation between The authors are with the Dept of Trauma and Orthopaedics. Chelsea and Westminster Hospital NHS Trust, London, UK. Address author correspondence to Simon Thompson at [email protected].
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the subchondral bone and articular cartilage, although subsequent histological studies have not supported this. Other hypotheses have included ischemia, genetic causes, endocrinopathies, spontaneous osteonecrosis, and repetitive trauma. Fairbanks’ theory6 of repeated trauma between the lateral aspect of the medial femoral condyle and the medial tibial spine explains the siting of lesions found on the medial condyle but does not explain those in other areas. However, as several studies have suggested, a link between OCD and regular involvement in sport or other strenuous activity involving repetitive minor trauma is currently the most accepted possible cause.7 The exact pathophysiology of OCD also remains unclear, but it is believed to be an acquired lesion of the subchondral bone, with varying degrees of bony reabsorption, collapse, and sequestrum formation, ultimately resulting in separation of the articular cartilage with its associated segment of subchondral bone.
Clinical Presentation The clinical presentation varies according to the stabil ity and severity of the lesion. Presenting symptoms, particularly in juvenile OCD, with nonseparated stable lesions are of nonspecific pain, often over a long period. It is often worse with activity and can result in mildly antalgic gait. Where the lesions are unstable, mechanical symptoms such as locking and catching, swelling, and stiffness can be found. Quadriceps atrophy may be seen if there has been a long history. Diagnosis of OCD can be confirmed on plain radio graphs, as most lesions can be identified if a knee series of 4 views (anteroposterior, lateral, tunnel, and merchant) is obtained. Magnetic resonance imaging (MRI) is com monly used to detect lesions that are not visible on X-ray and to determine the stability of the lesion. Although there is a lack of evidence regarding the use of MRI to detect lesions, there is evidence to support its use in determining
Management of Osteochondritis Dissecans
lesion stability.8 Fluid seen between the host bone and the lesion implies separation and potential instability. Ander son9 classified the M RI findings of O CD to illustrate the progression o f the disease. Stage 1 (flattened subchondral bone before closure o f the growth plate) and stage 2a (the presence o f a subchondral cyst) are both stable lesions. Stage 2b (incomplete OCD separation) and stage 3 (fluid around an undisplaced lesion) are deemed unstable, with stage 4 (detachment and loose-body formation) as an endstage event. Within the knee, 51% % o f OCD lesions are found on the lateral aspect of the medial femoral condyle, compared with 19% on the center and 7% on the medial side. Seven teen percent o f cases involve the lateral femoral condyle, whereas only 7% involve the patella.10
T re a tm e n t The aims o f treatment are to enhance the healing poten tial o f the subchondral bone, where possible to retain the articular cartilage fragment, and to ensure joint congruency. Retaining normal hyaline cartilage is the best outcome for the patient, as repaired cartilage (eg, after microfracture, autologous chondrocyte im plantation [ACI], and other methods o f chondral resurfacing such as osteochondral autologous transplantation, also known as mosaicplasty) is suboptimal by comparison. Stable lesions can be treated conservatively, but unstable lesions require surgery aiming where possible to fix the unstable fragment in place. If the fragment is not salvageable the aim is to stimulate articular cartilage repair or to replace affected bone and cartilage with implanted tissues or cells that can grow cartilage.
Nonoperative Treatment The majority o f authors believe that nonoperative manage ment should be the treatment o f choice for stable lesions in juveniles. The rationale for this approach is that reducing loading o f the vulnerable area may allow spontaneous heal ing. Although there is agreement that conservative treatment should continue for 3 to 6 months, there is no clear evidence for any specific nonoperative treatment program ." W all12 suggested w eight-bearing im m obilization in a long-leg cylinder or cast for 6 weeks for OCD o f the distal femoral condyle. If no reossification was visible on radiographs at that stage, a further 4 to 6 weeks of immobilization was given after a few days break for range-of-movement exercises. After this, an off-loader brace was used with a gradual return to activity while in the brace if the lesion was progressing to healing well. Complete, unrestricted brace-free activity was allowed after total reossification o f the lesion. M ore recently there has been a move away from immobilization and for partial weight bearing with crutches recommended until the patient has been symptom free for 4 weeks.4 The prognosis for healing o f the OCD lesion varies according to the site of the lesion and age of the patient. Patellar O CD carries the w orst prognosis, and m edial femoral condyle O CD the best. Greater healing potential
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in OCD is thought to be found in the younger age group, in narrower lesions, and where cystic-like lesions, as visual ized on M RI, are less than 1.3 mm.4
Surgical Treatment Surgical treatm ent is usually indicated for stable OCD lesions that have failed to heal with conservative treatment and in unstable lesions. Although there is consensus that surgery should be offered in these cases, there is no clear evidence as to which surgical procedures are best." The type o f surgery depends on the type o f OCD lesion. A rthroscopic drilling of the rim of the lesion, either retroarticular or transarticular, is a com mon treatm ent that in the senior author’s opinion should be considered in skeletally im m ature patients who remain sym ptom atic after 12 weeks o f conservative treatment. D rilling is thought to increase the flow of inflammatory factors and stem cells, resulting in neovascularization and ossification o f the cartilaginous lesion. However, this is an unproven hypothesis, and although the results are better in patients with open physes the literature is inconclusive as to the benefit o f drilling." Stable Lesions.
Undisplaced OCD Fragments Attached by a Chondral BridgelHinge. As the aim is to retain normal hyaline
articular cartilage, undisplaced O CD fragments should be secured into the correct anatomical position, taking care to ensure joint congruity. There is a lack of evidence regarding the best method of fixation, which can include metallic and bioabsorbable screws, biological fixation with osteochondral autograft plugs, or, if the underlying subchondral bone is very thin and at risk for fragmenting, absorbable sutures.13-15 Metal cancellous lag screws seem to have the best com pres sive effect but do “back out” at times and so need routine rem oval when the lesion is healed. Figure 1 shows an attached trochlea lesion in a professional footballer before treatment with small metal cancellous lag screws, which we feel offers the best compression. Figure 2 shows that the lesion is stable and integrated after removal of the screws. W here the lesion has a significant underlying cyst, elevation o f the fragment, freshening o f the deep bony
Figure 1 — Trochlea lesion still attached.
surface, and bone grafting of the cyst are recommended in addition to fixation of the fragment. Although pos sible with arthroscopic techniques, it is often best to undertake this surgery via an open arthrotomy so that no compromise is made with preparation of the lesion and its bony bed or fixation. Displaced Unstable Lesions. Large OCD lesions that have separated and displaced can still often be replaced and fixed. Often the lesion has hypertrophied over time and will not fit into its bed and therefore may need trim ming to ensure joint congruity. Both the deep surface
Figure 2 — After removal of 3 screws used to treat this lesion,
it can be seen that the trochlea lesion is still intact.
Figure 3 — A single hypertrophied segment—resected to fit and the bone bed drilled with a 2-mm k-wire.
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of the fragment (Figure 3) and the base of the crater should be curetted and drilled to stimulate healing (Figure 4) before fixation of the lesion (Figure 5). This is often achieved with more certainty via an open wound. The lesion illustrated had been separated for several years (Figure 6). Traditionally these cases were treated with removal of the loose body alone. However, our positive experience has led us to fixing these fragments even in cases that present late; the postoperative radiograph is shown in Figure 7. Figure 8 demonstrates a repaired lesion on the medial femoral condyle after removal of screws 1 year postoperatively.
Figure 4 — The base of the lesion is drilled with a 2-mm k-wire to encourage a bleeding bed.
Figure 5 — The replaced fragment held in place with 2 smallfragment cancellous lag screws.
Figure 6 — Osteochondritis dissecans of the medial femoral condyle on (left) plain radiograph and (right) magnetic resonance
imaging.
Figure 7 — Immediate postoperative radiographs showing the repaired lesion.
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the subchondral bone defect. Alternatively, mosaicplasty can be used. This is a process whereby plugs of subchon dral bone and articular cartilage are harvested from joint margins where weight bearing is limited and transferred into the defect. At present there is a lack of evidence to recommend either for or against any of these procedures in skeletally mature patients with unsalvageable O CD.11 Finally, surgical options could also include limb realignment with osteotomy to offload the OCD defect or focal replacements such as Hemicap (TM Arthrosurface).
Rehabilitation
F ig u re 8 — Notch view showing the repaired lesion after removal of the screws 1 year postoperatively.
Unsalvageable Lesions. Unfortunately, not all lesions are amenable to fixation, often due to excessive frag mentation. Although excision of the lesion can give short-term relief, long-term results show high rates of degeneration over time.16Therefore, excision of the lesion alone should be limited to patients with a low functional demand. In other patient groups additional procedures aimed at stimulating cartilage formation and restoring joint congruency should be used. Surgical procedures for this group can be divided into reparative methods, for example, microfracture and drilling, which aim to stimulate the formation of fibrocartilage, and restorative methods, for example, ACI and osteochondral autologous transplantation, which aim to fill the defect with transplanted tissue. Microfracture is more commonly used in traumatic chondral defects, where the integrity of the subchondral bone is not affected, than in OCD, where its effective ness is less well understood or illogical in view of bone loss. In OCD microfracture is more effective in smaller lesions, as debridement of larger lesions causes a deep defect that affects subchondral support and joint congru ency. Although macroscopically the repaired tissue has been variously reported as normal or nearly normal in 45% to 77% of cases, histologically they are found to mainly contain fibrocartilage or a hybrid fibrohyaline cartilage.17-19 This is of inferior quality to hyaline carti lage and is more prone to tissue degradation over time.18 This highlights the rationale of retaining the patient’s own hyaline cartilage where possible. Larger isolated defects in younger patients can be treated with ACI, which involves harvesting a small volume of articular cartilage at arthroscopy that is then grown in the laboratory. This is then inserted into the defect, if necessary in conjunction with bone grafting to
Although there is consensus that rehabilitation has an important role after any articular cartilage surgery,11 there is very little evidence regarding the specifics of the rehabilitation programs or their effectiveness.2021 The aim of rehabilitation is to restore full function, but this has to be achieved without overloading the healing articular cartilage or the stabilized fragment. Rehabilita tion is based on presumed knowledge and understanding of the healing process combined with an appreciation of the biomechanics of the knee during weight bearing and exercises to avoid excessive compressive and shearing forces within the knee. To optimize the healing process, rehabilitation needs to be tailored to the individual based on the quality of his or her articular cartilage, the size and location of the lesion, the type of surgery, and any concomitant knee pathology or surgery. Patient factors known to affect articular cartilage are age, obesity, poor nutrition, previ ous injury, and a history of repetitive-impact activities either through work or recreation.21 Smaller lesions are likely to progress more quickly than large, deep lesions. Generally, OCD fragments that have been fixed and reparative surgeries such as micro fracture will heal and rehabilitate more quickly than restorative procedures such as ACI. The rehabilitation program will vary with the site of the lesion based on the compression and shearing forces that affect that area of the knee. In the patellofemoral joint there is no articulation between the patella and trochlea in extension, and there fore early full weight bearing can often be allowed for patellar or trochlear lesions as long as the knee is held straight in a brace for 8 weeks. At surgery it should be noted at what flexion angles the patella makes contact with a trochlear lesion so that any safe zones for load ing may be defined. For patellar lesions there is less likelihood of safe zones, but the femoral contact with the patella moves from distal patellar in early flexion to proximal patella in deep flexion. In the tibiofemoral joint, articulation between the tibia and femur varies with flexion, so lesions on the ante rior femoral condyle can permit deep-flexion exercises earlier than those on the posterior femoral condyle. Again, noting the exact flexion arc of contact of the femoral lesion with the tibia will allow loading angles, where
Management of Osteochondritis Dissecans
possible, to be defined. O pen kinetic chain extension exercises can cause anterior and posterior tibial transla tion, except at the quadriceps-neutral angle (60-75°). W hether these shearing forces are detrim ental to cartilage in the normal knee is not known, but extra care m ust be taken if other pathologies such as ligam ent laxity exist, as these increase shearing forces. Shear forces are reduced in closed kinetic chain (CKC) exercises, due to the combined effect o f joint-com pression forces and muscle cocontrac tion in CK C exercise.22 Both open kinetic chain and CKC exercises are recom m ended, as CK C exercises alone may not restore full quadriceps strength.20 W eight-bearing restrictions will be determ ined by the location and size o f the lesion, but there is a lack o f evidence regarding the most appropriate weight-bearing regimens. Trochlear lesions are the exception and permitted to bear weight early providing the knee is braced in exten sion to ensure that there is no patellofemoral articulation. A lthough n o n -w e ig h t bearing is used for larger lesions, touch w eight bearing has been suggested after microfracture o f lesions o f less than 2 cm. Touch weight bearing for 6 to 8 weeks has also been suggested after bone graft o f the defect and fragm ent fixation using screws.23 However, there is no agreem ent regarding w eight bearing after internal fixation o f O CD lesions, with som e authors using both non-weight-bearing and touch-w eight-bearing regimens for 6 weeks postsurgery.13 Partial weight bearing o f 20% o f body w eight from 2 weeks progressing to full weight bearing at 8 weeks after matrix-induced ACI proce dure has been shown to be as safe as a traditional protocol that progressed to full w eight bearing at 12 w eeks.24 Progressing rehabilitation too quickly can have a detrimental effect on healing tissue, particularly after pro cedures such as microfracture and ACI. For O CD lesions that have been fixed in situ it is com m only assum ed that healing o f the subchondral bone continues for 12 weeks. The rate o f progression o f the rehabilitation will vary according to the size and type o f the lesion, the patient, and the type o f surgical procedure. During the early postoperative phase after fixation or after cartilage repair and restoration procedures, the goal o f rehabilitation is to reduce pain and swelling, optimize the healing environm ent, increase movement and loading, within safe limits to avoid sheering and compressive forces, and optim ize volitional quadriceps activation. Rest, ice, com pression, and elevation should be used to minimize swelling and help reduce pain. Continuous cooling has been suggested to help lower intra-articular tem perature,25 which is important, as increased tem pera ture is deleterious to articular cartilage. Patients should be taught to limit upright activity to a level that does not provoke an increase in pain and swelling and to always rest with their knee elevated in full extension to prevent developm ent o f a fixed flexion contracture. M inim izing pain and effusion is important due to the inhibition o f quadriceps activity they cause. Excessive sw elling and loss o f the ability to voluntarily activate the quadriceps contribute to the development o f a fixed flexion deformity, with the concom itant problem s this can
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cause. Frequent isometric quadriceps exercises during the early postoperative period can help maintain volitional quadriceps control, enhance patella mobility, and reduce joint effusion. There is no consensus regarding restoration o f move ment after fixation o f O CD fragm ents, with com plete im m obilization for 4 weeks, staged increase in m ove ment but limited to a maximum o f 90° for the first 6 to 8 w eeks,13 and immediate postoperative free range o f motion all being used.26 Range-of-m otion braces are com monly used to ensure that movement is restricted to the perm it ted safe range. Range o f m ovem ent should be progressed in a con trolled m anner with the aim o f full range o f m ovement at 3 months for restorative procedures or earlier for reparative ones. Although it is recognized that full range o f m ove m ent is likely to be achieved earlier after fixation o f an O CD fragment, there is no agreem ent on how quickly this should be allowed. Chondrocytes require some joint loading and m ove ment for nutrition, but at this stage the lesion is very sus ceptible to shearing forces, particularly if cartilage-repair techniques have been used. Passive movements produce less force within the joint than active movement, so patella mobilizations and passive ROM can usually be started early to regain m ovement and prevent formation o f adhesions. Repetitive passive movements can intensify synovial fluid flow and cause changes in intra-articular pressure, which will provide nutrition and stimulation to the healing carti lage. Several authors recommend using continuous passive motion for 6 to 8 h/d for 6 weeks to enhance cartilage healing after cartilage-repair procedures.21-24 25 Over time as the fragment or cartilage heals, progres sion o f w eight bearing is perm itted and a normal gait pat tern should be restored. Again, there is a lack o f consensus regarding the progression o f weight bearing after fragment fixation, with both non-w eight bearing and touch weight bearing being recommended for 6 w eeks.13-26 The time scales for progression to full w eight bearing vary between 8 weeks and 3 months21-24-25 for cartilage-repair procedures. Regardless o f surgical technique, walking aids should continue to be used to offload the joint in cases where decreased m uscle control is resulting in a flexed-knee gait. There should be a gradual increase in stresses through the jo in t by progression o f strengthening and functional exercises. As proprioceptive deficits have been found after knee surgery, rehabilitation should include proprioceptive and neuromuscular-control exercises. This progression of strength, endurance, and neurom uscular training should continue through the progression o f im pact activities until the patient has returned to prem orbid or desired activity levels. Reinold et al21 suggest return to highim pact activities after m icrofracture at betw een 4 and 8 m onths depending on lesion size. There is considerable variation in recom m endations for this after ACI, ranging betw een 12 and 18 m onths,20 w hereas recom m endations for im pact activities after O CD fragm ent fixation are not com m only known.
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Conclusion A s O C D is a relativ ely rare c o n d itio n , th ere is a lack o f c le a r ev id en c e re g a rd in g its b e st m an a g e m e n t, b o th su rg ic a lly an d fro m a re h a b ilita tio n p e rsp e c tiv e . T h e reten tio n o f the p a tie n t’s ow n h y alin e c a rtila g e w h en ev er p o ssib le sh o u ld b e the p rim ary g o al, w h ile reh ab ilita tio n sh o u ld be tailo re d to in d iv id u al p a tie n ts a c c o rd in g to the in terv en tio n they received.
References 1. O bedian RS, G relsam er RP. O steo ch o n d ritis d isse cans of the distal femur and patella. Clin Sports Med. 1997;16(1): 1 5 7 -1 7 4 . P ubM ed d o i: 10.1016/S 02785919(05)70012-0 2. Guhl JF. Arthroscopic treatment of osteochondritis disse cans. Clin Orthop Relat Res. 1982; (167):65—74. PubMed 3. Kocher MS, Tucker R, Ganley TJ, Flyn JM. Management of osteochondritis dissecans of the knee: current concepts review. Am J Sports Med. 2006;34(7): 1181-1191. PubMed doi: 10.1177/0363546506290127 4. K rause M, H a p fe lm e ie r A, M o ller M, A m ling M, B o h n d o rf K, M eenen NM . H e a lin g p re d ic to rs of stable juvenile osteochondritis dissecans knee lesions a fter 6 and 12 m onths o f n o n o p erativ e treatm en t. Am J Sports Med. 2013 ;4 1(10 ):2 3 8 4 -2 3 9 1. PubM ed doi: 10.1177/0363546513496049 5. Barrie HJ. Osteochondritis dissecans 1887-1987: a centen nial look at Konig’s memorable phrase. J Bone Joint Surg Br. 1987;69(5):693—695. PubMed 6. Fairbanks HA. O steo-chondritis dissecans. Br J Surg. 1933;21:67-82. 7. Edmunds EW. Polousky J. A review o f knowledge in osteochondritis dissecans: 123 years of minimal evolution from Konig to the ROCK study group. Clin Orthop Relat Res. 2013;471:1118-1126. 8. Quatman CE, Quatman-Yates CC, Schmitt LC, Patemo MV. The clinical utility and diagnostic performance of MR1 for identification and classification of knee osteochondritis dissecans. J Bone Joint Surg Am. 2012;94( 11): 1036—1044. 9. Anderson IF, Crichton KJ, Grattan-Smith T, Cooper RA, Brazier D. Osteochondral fractures of the dome of the talus. J Bone Joint Surg Am. 1989;71 (8): 1143-1152. PubMed 10. Hefti F, Beguiristain J, Krauspe P, et al. Osteochondritis dissecans: a multicentre study o f the European Paediatric Orthopaedic Society. JPaediatr Orthop B. 1999;(8)231—245. 11. American Academy o f Orthopaedic Surgeons. American
Academy o f Orthopaedic Surgeons Clinical Practice Guideline on the Diagnosis and Treatment o f Osteochon dritis Dissecans. Rosemont, IL: Author; 2010. 12. Wall EJ, Vourazeris J, Myer GD, et al. The healing potential of stable juvenile osteochondritis dissecans knee lesions. J Bone Joint Surg Am. 2008;(90):2655-2664. 13. Kocher MS, Czamecki JJ, Andersen JS, Micheli LJ. Internal fixation of juvenile osteochondritis dissecans lesions of the knee. Am J Sports Med. 2007;35(5):712-718. PubMed doi: 10.1177/0363546506296608
14. W om bw ell JH , N unley JA. C o m p re ssiv e fix atio n of osteochondritis dissecans fragm ents with H erbert screws. J Orthop Trauma. 1987; 1(1 ):74—77. PubM ed doi: 10.1097/00005131-198701010-00013 15. Miniaci A, Tytherleigh-Strong G. Fixation of unstable osteo chondritis dissecans lesions of the knee using arthroscopic au to g en o u s o steo ch o n d ral g raftin g (m o saicp lasty). Arthroscopy. 2007;23(8):845—851. PubMed doi: 10.1016/j. arthro.2007.02.017 16. W right RW, M cL ean M, M atava M J, S hively RA. Osteochondritis dissecans of the knee: long term results of excision o f the fragm ent. Clin Orthop Relat Res. 2004;(424):239-243. PubMed 17. Gudas R, Kalesinskas RJ. Kimtys V, et al. A prospective randomized clinical study of mosaic osteochondral autolo gous transplantation versus microfracture for the treatment of osteochondral defects in the knee joint in young athletes. Arthroscopy. 2005;21:1066-1075. PubMed doi: 10.1016/j. arthro.2005.06.018 18. Knutsen G, Drogset JO, Engebretsen L, et al. A randomized trial comparing autologous chondrocyte implantation with microfracture: findings at five years. J Bone Joint Surg Am. 2007;89:2105-2112. PubMed doi:10.2106/JBJS.G.00003 19. Knutsen G, Engebretsen L, Ludvigsen TC, et al. Autologous chondrocyte implantation compared with microfracture in the knee: a randomized trial. J Bone Joint Surg Am. 2004;86A:455^t64. PubMed 20. H am bly K, Bobic V, W ondrasch B, Van A ssche D, Marlovits S. Autologous chondrocyte implantation post operative care and rehabilitation: science and practice. Am J Sports Med. 2006;34(6): 1 0 2 0-1038. PubM ed doi:10.1177/0.363546505281918 21. Reinold MM, Wilk KE, M acrina LC, Dugas JR, Cain EL. Current concepts in rehabilitation following articular cartilage repair procedures in the knee. J Orthop Sports Phys Ther. 2006;36(10):774-794. PubMed doi: 10.2519/ jospt.2006.2228 22. Escamilla RF. Knee biomechanics of the dynamic squat exercise. Med Sci Sports Exerc. 2001 ;33:127—141. PubMed doi: 10.1097/00005768-200101000-00020 23. Detterline AJ, Goldstein JL, Rue J-PH, Bach BR. Evaluation and treatment of osteochondritis lesions of the knee. J Knee Surg. 2008;21 (2): 106—115. PubMed 24. Ebert JR, Fallon M, Zheng MH, Wood DJ, Ackland TR. A randomised trial comparing accelerated and traditional approaches to postoperative weightbearing rehabilitation after matrix-induced autologous chondrocyte implanta tion. Am J Sports Med. 2012;40(7): 1527-1537. PubMed doi: 10.1177/0363546512445167 25. Hirschmuller A, Baur H, Braun S, Kreuz PC, Sudkamp NP, Niemayer P. Rehabilitation after autologous chon drocyte implantation for isolated cartilage defects of the knee. Am J Sports Med. 2011 ;39( 12):2686-2696. PubMed doi: 10.1177/0363546511404204 26. Millington KL, Shah JP, Dahm DL, Levy BA, Stuart MJ. Bioabsorbable fixation of unstable osteochondritis dissecans lesions. Am J Sports Med. 2010;38( 10):2065—2070. PubMed doi: 10.1177/0363546510371369
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Management of Osteochondritis Dissecans of the Knee Simon M. Thompson, Mary Jones, Jonathon R. Lavelle, and Andy Williams The etiology of osteochondritis dissecans is hypothesized as repetitive microtrauma, resulting in an interruption of blood supply. Due to the location of the most common lesions on the medial femoral condyle, impinge ment of either the medial tibial spine or inferior pole of the patella against the adjacent medial femur may be responsible. It is much more common in athletic males than other groups. This article reviews the current treatment options for lesions around the knee.
Keywords: cartilage, surgery, OCD, rehabilitation Osteochondritis dissecans (OCD) is a disorder of subchondral bone that can affect the overlying articular cartilage. Advanced lesions may separate, causing pain and mechanical symptoms. Although OCD was first described in 1738, its etiology, natural history, and man agement are still not fully understood. OCD is commonly divided into juvenile and adult forms. It is classed as juvenile OCD when it presents in a skeletally immature patient with an open physis of the involved bone. It affects 15 to 29 people per 100,000 of the general population each year, with the knee being the most commonly involved joint.1It is most frequently seen between the age of 13 and 21 and is more common in males by a ratio of 5:3.2 However, it is thought that greater partici pation in competitive sport by children is resulting in OCD at a younger age and also increasing its prevalence in girls.3 Juvenile OCD lesions are often stable, with an intact articular surface, and have the greatest potential to heal with conservative treatment, whereas adult OCD lesions are more likely to be unstable (ie, separated) and require surgery and have a worse prognosis. However, even in juvenile OCD the failure rates o f conservative treatment have been reported as over 50%.4 The early identification and treatment of OCD in the knee are therefore essential to optimize healing potential and outcome, as OCD lesions that do not heal can lead to premature joint degeneration. After a brief overview of OCD this article aims to describe its management based on the disease stage of OCD at diagnosis.
Etiology OCD was originally named by Konig in 1887,5 who believed it to occur as a result of inflammation between The authors are with the Dept of Trauma and Orthopaedics. Chelsea and Westminster Hospital NHS Trust, London, UK. Address author correspondence to Simon Thompson at [email protected].
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the subchondral bone and articular cartilage, although subsequent histological studies have not supported this. Other hypotheses have included ischemia, genetic causes, endocrinopathies, spontaneous osteonecrosis, and repetitive trauma. Fairbanks’ theory6 of repeated trauma between the lateral aspect of the medial femoral condyle and the medial tibial spine explains the siting of lesions found on the medial condyle but does not explain those in other areas. However, as several studies have suggested, a link between OCD and regular involvement in sport or other strenuous activity involving repetitive minor trauma is currently the most accepted possible cause.7 The exact pathophysiology of OCD also remains unclear, but it is believed to be an acquired lesion of the subchondral bone, with varying degrees of bony reabsorption, collapse, and sequestrum formation, ultimately resulting in separation of the articular cartilage with its associated segment of subchondral bone.
Clinical Presentation The clinical presentation varies according to the stabil ity and severity of the lesion. Presenting symptoms, particularly in juvenile OCD, with nonseparated stable lesions are of nonspecific pain, often over a long period. It is often worse with activity and can result in mildly antalgic gait. Where the lesions are unstable, mechanical symptoms such as locking and catching, swelling, and stiffness can be found. Quadriceps atrophy may be seen if there has been a long history. Diagnosis of OCD can be confirmed on plain radio graphs, as most lesions can be identified if a knee series of 4 views (anteroposterior, lateral, tunnel, and merchant) is obtained. Magnetic resonance imaging (MRI) is com monly used to detect lesions that are not visible on X-ray and to determine the stability of the lesion. Although there is a lack of evidence regarding the use of MRI to detect lesions, there is evidence to support its use in determining
Management of Osteochondritis Dissecans
lesion stability.8 Fluid seen between the host bone and the lesion implies separation and potential instability. Ander son9 classified the M RI findings of O CD to illustrate the progression o f the disease. Stage 1 (flattened subchondral bone before closure o f the growth plate) and stage 2a (the presence o f a subchondral cyst) are both stable lesions. Stage 2b (incomplete OCD separation) and stage 3 (fluid around an undisplaced lesion) are deemed unstable, with stage 4 (detachment and loose-body formation) as an endstage event. Within the knee, 51% % o f OCD lesions are found on the lateral aspect of the medial femoral condyle, compared with 19% on the center and 7% on the medial side. Seven teen percent o f cases involve the lateral femoral condyle, whereas only 7% involve the patella.10
T re a tm e n t The aims o f treatment are to enhance the healing poten tial o f the subchondral bone, where possible to retain the articular cartilage fragment, and to ensure joint congruency. Retaining normal hyaline cartilage is the best outcome for the patient, as repaired cartilage (eg, after microfracture, autologous chondrocyte im plantation [ACI], and other methods o f chondral resurfacing such as osteochondral autologous transplantation, also known as mosaicplasty) is suboptimal by comparison. Stable lesions can be treated conservatively, but unstable lesions require surgery aiming where possible to fix the unstable fragment in place. If the fragment is not salvageable the aim is to stimulate articular cartilage repair or to replace affected bone and cartilage with implanted tissues or cells that can grow cartilage.
Nonoperative Treatment The majority o f authors believe that nonoperative manage ment should be the treatment o f choice for stable lesions in juveniles. The rationale for this approach is that reducing loading o f the vulnerable area may allow spontaneous heal ing. Although there is agreement that conservative treatment should continue for 3 to 6 months, there is no clear evidence for any specific nonoperative treatment program ." W all12 suggested w eight-bearing im m obilization in a long-leg cylinder or cast for 6 weeks for OCD o f the distal femoral condyle. If no reossification was visible on radiographs at that stage, a further 4 to 6 weeks of immobilization was given after a few days break for range-of-movement exercises. After this, an off-loader brace was used with a gradual return to activity while in the brace if the lesion was progressing to healing well. Complete, unrestricted brace-free activity was allowed after total reossification o f the lesion. M ore recently there has been a move away from immobilization and for partial weight bearing with crutches recommended until the patient has been symptom free for 4 weeks.4 The prognosis for healing o f the OCD lesion varies according to the site of the lesion and age of the patient. Patellar O CD carries the w orst prognosis, and m edial femoral condyle O CD the best. Greater healing potential
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in OCD is thought to be found in the younger age group, in narrower lesions, and where cystic-like lesions, as visual ized on M RI, are less than 1.3 mm.4
Surgical Treatment Surgical treatm ent is usually indicated for stable OCD lesions that have failed to heal with conservative treatment and in unstable lesions. Although there is consensus that surgery should be offered in these cases, there is no clear evidence as to which surgical procedures are best." The type o f surgery depends on the type o f OCD lesion. A rthroscopic drilling of the rim of the lesion, either retroarticular or transarticular, is a com mon treatm ent that in the senior author’s opinion should be considered in skeletally im m ature patients who remain sym ptom atic after 12 weeks o f conservative treatment. D rilling is thought to increase the flow of inflammatory factors and stem cells, resulting in neovascularization and ossification o f the cartilaginous lesion. However, this is an unproven hypothesis, and although the results are better in patients with open physes the literature is inconclusive as to the benefit o f drilling." Stable Lesions.
Undisplaced OCD Fragments Attached by a Chondral BridgelHinge. As the aim is to retain normal hyaline
articular cartilage, undisplaced O CD fragments should be secured into the correct anatomical position, taking care to ensure joint congruity. There is a lack of evidence regarding the best method of fixation, which can include metallic and bioabsorbable screws, biological fixation with osteochondral autograft plugs, or, if the underlying subchondral bone is very thin and at risk for fragmenting, absorbable sutures.13-15 Metal cancellous lag screws seem to have the best com pres sive effect but do “back out” at times and so need routine rem oval when the lesion is healed. Figure 1 shows an attached trochlea lesion in a professional footballer before treatment with small metal cancellous lag screws, which we feel offers the best compression. Figure 2 shows that the lesion is stable and integrated after removal of the screws. W here the lesion has a significant underlying cyst, elevation o f the fragment, freshening o f the deep bony
Figure 1 — Trochlea lesion still attached.
surface, and bone grafting of the cyst are recommended in addition to fixation of the fragment. Although pos sible with arthroscopic techniques, it is often best to undertake this surgery via an open arthrotomy so that no compromise is made with preparation of the lesion and its bony bed or fixation. Displaced Unstable Lesions. Large OCD lesions that have separated and displaced can still often be replaced and fixed. Often the lesion has hypertrophied over time and will not fit into its bed and therefore may need trim ming to ensure joint congruity. Both the deep surface
Figure 2 — After removal of 3 screws used to treat this lesion,
it can be seen that the trochlea lesion is still intact.
Figure 3 — A single hypertrophied segment—resected to fit and the bone bed drilled with a 2-mm k-wire.
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of the fragment (Figure 3) and the base of the crater should be curetted and drilled to stimulate healing (Figure 4) before fixation of the lesion (Figure 5). This is often achieved with more certainty via an open wound. The lesion illustrated had been separated for several years (Figure 6). Traditionally these cases were treated with removal of the loose body alone. However, our positive experience has led us to fixing these fragments even in cases that present late; the postoperative radiograph is shown in Figure 7. Figure 8 demonstrates a repaired lesion on the medial femoral condyle after removal of screws 1 year postoperatively.
Figure 4 — The base of the lesion is drilled with a 2-mm k-wire to encourage a bleeding bed.
Figure 5 — The replaced fragment held in place with 2 smallfragment cancellous lag screws.
Figure 6 — Osteochondritis dissecans of the medial femoral condyle on (left) plain radiograph and (right) magnetic resonance
imaging.
Figure 7 — Immediate postoperative radiographs showing the repaired lesion.
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the subchondral bone defect. Alternatively, mosaicplasty can be used. This is a process whereby plugs of subchon dral bone and articular cartilage are harvested from joint margins where weight bearing is limited and transferred into the defect. At present there is a lack of evidence to recommend either for or against any of these procedures in skeletally mature patients with unsalvageable O CD.11 Finally, surgical options could also include limb realignment with osteotomy to offload the OCD defect or focal replacements such as Hemicap (TM Arthrosurface).
Rehabilitation
F ig u re 8 — Notch view showing the repaired lesion after removal of the screws 1 year postoperatively.
Unsalvageable Lesions. Unfortunately, not all lesions are amenable to fixation, often due to excessive frag mentation. Although excision of the lesion can give short-term relief, long-term results show high rates of degeneration over time.16Therefore, excision of the lesion alone should be limited to patients with a low functional demand. In other patient groups additional procedures aimed at stimulating cartilage formation and restoring joint congruency should be used. Surgical procedures for this group can be divided into reparative methods, for example, microfracture and drilling, which aim to stimulate the formation of fibrocartilage, and restorative methods, for example, ACI and osteochondral autologous transplantation, which aim to fill the defect with transplanted tissue. Microfracture is more commonly used in traumatic chondral defects, where the integrity of the subchondral bone is not affected, than in OCD, where its effective ness is less well understood or illogical in view of bone loss. In OCD microfracture is more effective in smaller lesions, as debridement of larger lesions causes a deep defect that affects subchondral support and joint congru ency. Although macroscopically the repaired tissue has been variously reported as normal or nearly normal in 45% to 77% of cases, histologically they are found to mainly contain fibrocartilage or a hybrid fibrohyaline cartilage.17-19 This is of inferior quality to hyaline carti lage and is more prone to tissue degradation over time.18 This highlights the rationale of retaining the patient’s own hyaline cartilage where possible. Larger isolated defects in younger patients can be treated with ACI, which involves harvesting a small volume of articular cartilage at arthroscopy that is then grown in the laboratory. This is then inserted into the defect, if necessary in conjunction with bone grafting to
Although there is consensus that rehabilitation has an important role after any articular cartilage surgery,11 there is very little evidence regarding the specifics of the rehabilitation programs or their effectiveness.2021 The aim of rehabilitation is to restore full function, but this has to be achieved without overloading the healing articular cartilage or the stabilized fragment. Rehabilita tion is based on presumed knowledge and understanding of the healing process combined with an appreciation of the biomechanics of the knee during weight bearing and exercises to avoid excessive compressive and shearing forces within the knee. To optimize the healing process, rehabilitation needs to be tailored to the individual based on the quality of his or her articular cartilage, the size and location of the lesion, the type of surgery, and any concomitant knee pathology or surgery. Patient factors known to affect articular cartilage are age, obesity, poor nutrition, previ ous injury, and a history of repetitive-impact activities either through work or recreation.21 Smaller lesions are likely to progress more quickly than large, deep lesions. Generally, OCD fragments that have been fixed and reparative surgeries such as micro fracture will heal and rehabilitate more quickly than restorative procedures such as ACI. The rehabilitation program will vary with the site of the lesion based on the compression and shearing forces that affect that area of the knee. In the patellofemoral joint there is no articulation between the patella and trochlea in extension, and there fore early full weight bearing can often be allowed for patellar or trochlear lesions as long as the knee is held straight in a brace for 8 weeks. At surgery it should be noted at what flexion angles the patella makes contact with a trochlear lesion so that any safe zones for load ing may be defined. For patellar lesions there is less likelihood of safe zones, but the femoral contact with the patella moves from distal patellar in early flexion to proximal patella in deep flexion. In the tibiofemoral joint, articulation between the tibia and femur varies with flexion, so lesions on the ante rior femoral condyle can permit deep-flexion exercises earlier than those on the posterior femoral condyle. Again, noting the exact flexion arc of contact of the femoral lesion with the tibia will allow loading angles, where
Management of Osteochondritis Dissecans
possible, to be defined. O pen kinetic chain extension exercises can cause anterior and posterior tibial transla tion, except at the quadriceps-neutral angle (60-75°). W hether these shearing forces are detrim ental to cartilage in the normal knee is not known, but extra care m ust be taken if other pathologies such as ligam ent laxity exist, as these increase shearing forces. Shear forces are reduced in closed kinetic chain (CKC) exercises, due to the combined effect o f joint-com pression forces and muscle cocontrac tion in CK C exercise.22 Both open kinetic chain and CKC exercises are recom m ended, as CK C exercises alone may not restore full quadriceps strength.20 W eight-bearing restrictions will be determ ined by the location and size o f the lesion, but there is a lack o f evidence regarding the most appropriate weight-bearing regimens. Trochlear lesions are the exception and permitted to bear weight early providing the knee is braced in exten sion to ensure that there is no patellofemoral articulation. A lthough n o n -w e ig h t bearing is used for larger lesions, touch w eight bearing has been suggested after microfracture o f lesions o f less than 2 cm. Touch weight bearing for 6 to 8 weeks has also been suggested after bone graft o f the defect and fragm ent fixation using screws.23 However, there is no agreem ent regarding w eight bearing after internal fixation o f O CD lesions, with som e authors using both non-weight-bearing and touch-w eight-bearing regimens for 6 weeks postsurgery.13 Partial weight bearing o f 20% o f body w eight from 2 weeks progressing to full weight bearing at 8 weeks after matrix-induced ACI proce dure has been shown to be as safe as a traditional protocol that progressed to full w eight bearing at 12 w eeks.24 Progressing rehabilitation too quickly can have a detrimental effect on healing tissue, particularly after pro cedures such as microfracture and ACI. For O CD lesions that have been fixed in situ it is com m only assum ed that healing o f the subchondral bone continues for 12 weeks. The rate o f progression o f the rehabilitation will vary according to the size and type o f the lesion, the patient, and the type o f surgical procedure. During the early postoperative phase after fixation or after cartilage repair and restoration procedures, the goal o f rehabilitation is to reduce pain and swelling, optimize the healing environm ent, increase movement and loading, within safe limits to avoid sheering and compressive forces, and optim ize volitional quadriceps activation. Rest, ice, com pression, and elevation should be used to minimize swelling and help reduce pain. Continuous cooling has been suggested to help lower intra-articular tem perature,25 which is important, as increased tem pera ture is deleterious to articular cartilage. Patients should be taught to limit upright activity to a level that does not provoke an increase in pain and swelling and to always rest with their knee elevated in full extension to prevent developm ent o f a fixed flexion contracture. M inim izing pain and effusion is important due to the inhibition o f quadriceps activity they cause. Excessive sw elling and loss o f the ability to voluntarily activate the quadriceps contribute to the development o f a fixed flexion deformity, with the concom itant problem s this can
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cause. Frequent isometric quadriceps exercises during the early postoperative period can help maintain volitional quadriceps control, enhance patella mobility, and reduce joint effusion. There is no consensus regarding restoration o f move ment after fixation o f O CD fragm ents, with com plete im m obilization for 4 weeks, staged increase in m ove ment but limited to a maximum o f 90° for the first 6 to 8 w eeks,13 and immediate postoperative free range o f motion all being used.26 Range-of-m otion braces are com monly used to ensure that movement is restricted to the perm it ted safe range. Range o f m ovem ent should be progressed in a con trolled m anner with the aim o f full range o f m ovement at 3 months for restorative procedures or earlier for reparative ones. Although it is recognized that full range o f m ove m ent is likely to be achieved earlier after fixation o f an O CD fragment, there is no agreem ent on how quickly this should be allowed. Chondrocytes require some joint loading and m ove ment for nutrition, but at this stage the lesion is very sus ceptible to shearing forces, particularly if cartilage-repair techniques have been used. Passive movements produce less force within the joint than active movement, so patella mobilizations and passive ROM can usually be started early to regain m ovement and prevent formation o f adhesions. Repetitive passive movements can intensify synovial fluid flow and cause changes in intra-articular pressure, which will provide nutrition and stimulation to the healing carti lage. Several authors recommend using continuous passive motion for 6 to 8 h/d for 6 weeks to enhance cartilage healing after cartilage-repair procedures.21-24 25 Over time as the fragment or cartilage heals, progres sion o f w eight bearing is perm itted and a normal gait pat tern should be restored. Again, there is a lack o f consensus regarding the progression o f weight bearing after fragment fixation, with both non-w eight bearing and touch weight bearing being recommended for 6 w eeks.13-26 The time scales for progression to full w eight bearing vary between 8 weeks and 3 months21-24-25 for cartilage-repair procedures. Regardless o f surgical technique, walking aids should continue to be used to offload the joint in cases where decreased m uscle control is resulting in a flexed-knee gait. There should be a gradual increase in stresses through the jo in t by progression o f strengthening and functional exercises. As proprioceptive deficits have been found after knee surgery, rehabilitation should include proprioceptive and neuromuscular-control exercises. This progression of strength, endurance, and neurom uscular training should continue through the progression o f im pact activities until the patient has returned to prem orbid or desired activity levels. Reinold et al21 suggest return to highim pact activities after m icrofracture at betw een 4 and 8 m onths depending on lesion size. There is considerable variation in recom m endations for this after ACI, ranging betw een 12 and 18 m onths,20 w hereas recom m endations for im pact activities after O CD fragm ent fixation are not com m only known.
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Conclusion A s O C D is a relativ ely rare c o n d itio n , th ere is a lack o f c le a r ev id en c e re g a rd in g its b e st m an a g e m e n t, b o th su rg ic a lly an d fro m a re h a b ilita tio n p e rsp e c tiv e . T h e reten tio n o f the p a tie n t’s ow n h y alin e c a rtila g e w h en ev er p o ssib le sh o u ld b e the p rim ary g o al, w h ile reh ab ilita tio n sh o u ld be tailo re d to in d iv id u al p a tie n ts a c c o rd in g to the in terv en tio n they received.
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