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Osteochondritis Dissecans Ankle Classification Essay

Osteochondritis Dissecans (OCD), Osteochondral Fracture of the Ankle

Osteochondritis Dissecans is also known as an osteochondral bone defect. This condition is one in which a piece of bone and cartilage within a joint are damaged and in some cases separate from the underlying bone. It occurs most often in the knee and next most often in the ankle. We will focus on the ankle in this article.

This clinical entity was first described in the literature by Franz König in 1888. The description was of knee pain caused by what Konig termed “osteochondritis dissecans”. It was described in the ankle in 1922 by Kappis. A classification system for ankle osteochondral injuries was devised by Berndt and Harty in 1959 which was used unchanged for 40 years. In 1989 Johnson et. al. proposed a modification of the Berndt and Harty classification which has become so popular that one can almost no longer find mention of the Berndt and Harty classification which Johnson specifically stated he was modifying. The classification systems are detailed below.

In the ankle OCD can occur anterolateral or posteriomedial. On the lateral aspect of the ankle it most often occurs from trauma. The lateral injuries to the Talus (ankle bone) are usually shallow and cup shaped. The injury occurring on the medial aspect of the Talus is often deeper and cup shaped. It often develops above a bone cyst.

Osteochondral injuries are a possible cause of continued ankle pain after a sprain. Osteochondral injuries occur more often than thought and result in significant disability and pain. A high level of suspicion is needed with continued pain and disability. At the initial physical evaluation following injury, the dorsolateral aspect of the talus should be examined for tenderness. Although in most cases, the Ottawa Criteria for ankle injuries is the standard of care and should be followed. Diagnostic testing for osteochondral injury should include an x-ray, possible bone scan, and MRI in the event the x-ray does not show the injury.

An early stage injury may progress to a late stage if inadequate immobilization is used. An injury that is not displaced may heal with proper immobilization. I recommend using a Pneumatic Walker as immobilization for high grade ankle sprains, inversion injuries with much pain and swelling, even when further evaluation for an osteochondral injury is not being done. In the event of pain and disability lasting longer than 6 weeks (as described by Anderson, and noted clinically by many) an osteochondral fracture should be

... A pneumatic walking cast used during the initial injury period, in many cases would assist healing ...

suspected and evaluation for this injury should be done. Prolonged swelling and pain are possible indicators to this condition. A pneumatic walking cast used during the initial injury period, in many cases could assist healing a severe sprain with a low grade undiagnosed osteochondral injury. Immobilization for low grade injury would have likely been the recommended therapy. When, in spite of immobilization. or in any case in which pain persists and only minimal progress has been made and normal activities can not be resumed, further evaluation is in order.

Anderson in the article in which he proposed a modification of the Berndt and Harty classification system recommended immobilization for six weeks for Stage I and Stage II osteochondral fractures. For Stage IIA, III and IV surgery was recommended. Procedures are improving and still evolving.

Osteochondral plugs have been used from autologous tissue and also from donor tissue. The characteristics of the cartilage needed for the ankle differ from that of the knee. The forces are greater and the structure and dimensions of the cartilage are different from the knee (and hip) compared to the ankle.

“... Osteochondral injuries occur more often than thought and result in significant disability and pain. ...”

 

Classification and Staging:

Berndt and Harty (1959):
Stage 1 – Compression fracture (small)
Stage 2 – incomplete avulsion of fragment
Stage 3 – complete avulsion without displacement
Stage 4 - Avulsion of fragment with displacement

Anderson (1989) (Modified Berndt and Harty)

This classification would better be termed a modified Berndt and Harty classification in view of the historical background, and the specific mention by Anderson that it is a modification of the original system. Academicians and clinicians will find Anderson’s article well worth reading.

Stage I – Subchondral trabecular compression. No visible injury seen on x-ray. Bone scan will demonstrate an injury. If so, then MRI will help define the injury, showing marrow edema.
Stage II – Incomplete separation of the osteochondral fragment. Can readily be seen on computerized tomography (CT Scan) or magnetic resonance imaging (MRI Scan).
Stage IIA – Formation of a Subcondral Cyst. Thought to be a progression of a Stage I injury. May occur in areas of resorption of necrotic (dead) trabeculae or post traumatic necrotic changes occur. Osteonecrosis is thought to follow a patter of first the death of hematopoietic cells and bone marrow. Next is a response of fluid transudate, production of fibrin and inflammatory infiltrate. A narrow line of demarcation of the osteonecrosis will form. MRI will detail this area well.
Stage III – Unattached, but undisplaced fragment.
An attachment to the talus cannot be seen, but the fragment is not displaced. T2 image may demonstrate synovial fluid around a fragment. This will help distinguish a Stage II from a Stage III injury.
Stage IV – Displaced fragment.
The displacement can at times be so severe that the fragment is inverted to its original position.

Diagnostic Flow Chart:

X-ray – if positive – CT Scan and appropriate treatment
If Normal
Bone Scan (or jump to MRI) – if negative – no OCD - use appropriate treatment
if Positive – MRI for evaluation and staging
CT may be useful for monitoring progress.


Cllick For Enlarged View

Treatment Possibilities (see current literature):

Reduction and stabilization of fracture site and osteochondral fragment. Often for adolescents with large lesions.

Debridement, removal of the fragment with bone marrow stimulation to the level of the subchondral bone. Bone marrow stimulation may be achieved by drilling, abrasion, or microfracture. Particularly for fragments under 15 mm in size.

Transplantation (osteochondral autograft or in some cases fresh cadaver osteochondral bone, Allograft transplantation, has been used) Note that the Knee cartilage has thinner dense layer and is not always up to the high stresses in the ankle. Primarily for larger, often cystic (medial lesions).

Mosaicplasty/osteochondral autograft transplantation

Osteochondral autograft with autologous chondrocyte implantation (ACI), with or without a cancellous bone graft

For general evaluation and treatment of lateral ankle inversion injuries see: Dr. Pribut on Ankle Injuries

References:

Anderson IF, et al: Osteochondral fractures of the dome of the talus JBJS – Am. 71(8):1143-52, Sept. 1989. 3.

Berndt, AL, Harty, M. Transchondral fractures (osteochondritis dissecans) of the talus. JBJS. Vol 41-A. 988-1020, 1959.

Chodos, M. , Schon, L. Osteochondral lesions of the talus: Current treatment modalities and future possibilities. Current Opinion in Orthopaedics
Volume 17, Issue 2, April 2006, Pages 111-116

Kappis M (1922). "Weitere beitrage zur traumatisch-mechanischen entstehung der "spontanen" knorpela biosungen". Deutsche Zeitschrift für Chirurgie 171: 13-29.

König F (December 1888). "Uber freie Korper in den gelenken". Deutsche Zeitschrift für Chirurgie 27 (1-2): 90-109.
http://www.springerlink.com/content/m57696053j598h56/fulltext.pdf?page=1.

Tamai N, Myoui A, Hirao M, et al. A new biotechnology for articular cartilage repair: subchondral implantation of a composite of interconnected porous hydroxyapatite, synthetic polymer (PLA-PEG), and bone morphogenetic protein-2 (rhBMP-2). Osteoarthritis Cartilage 2005; 13:405–417.

van Bergen, C.J.A., de Leeuw, P.A.J., van Dijk, C.N . Treatment of osteochondral defects of the talus. Revue de Chirurgie Orthopedique et Reparatrice de l'Appareil Moteur . Volume 94, Issue 8 SUPPL., December 2008, Pages 398-408

Whittaker JP, Smith G, Makwana N, et al. Early results of autologous chondrocyte implantation in the talus. J Bone Joint Surg Br 2005; 87:179–183

Osteochondral defects are focal areas of articular damage with cartilage damage and injury of the adjacent subchondral bone. It is a term that encompasses osteochondritis dissecans and is used synonymously with osteochondral injury/defect in the paediatric population.

On this page:

Aetiology
Location

The recognised sites of osteochondral defects are:

  • femoral condyle (most common)
  • humeral head
  • talus
  • capitellum of the humerus
Staging

Osteochondral injuries are graded according to the stability and location of the fragment and presence of secondary degenerative changes (see: osteochondral injury staging).

Plain radiograph and CT

Both x-rays and CT are able to detect displaced defects with ease. However, they are insensitive to grading lower stage lesions and are inadequate in predicting stability.

MRI

MRI is the modality of choice, with high sensitivity and specificity for the detection of separation of the osteochondral fragment (see: osteochondral injury staging and osteochondritis dissecans surgical staging). This is essential in determining management.

  • T1
    • the signal is variable with intermediate to low signal adjacent to fragment and variable fragment signal
  • T2
    • high signal line (rim sign) demarcating fragment from bone usually indicates an unstable lesion, however, false positives can result from oedema
    • low signal loose bodies, outlined by high signal fluid
    • donor defect filled with high signal fluid
    • high signal subchondral cysts

Treatment and prognosis

Treatment depends on the location and size of the defect as well as presence of secondary degenerative changes. When the latter is present, then joint replacement is often the only feasible treatment.

At earlier stages (stage 1 to 4), a number of options exist including:

  • osteochondral autograft (same patient)
  • osteochondral allografts (cadaveric donor)
  • subchondral bone drilling
  • chondral shaving and abrasion

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