Osteochondritis dissecans (OCD) is the end result of the aseptic separation of an osteochondral fragment with the gradual fragmentation of the articular surface and results in an osteochondral defect. It is often associated with intraarticular loose bodies.
Onset is between childhood and young adults age, with the majority of patients being between 10 and 40 years of age, with approximately a 2:1 male to female ratio .
- repetitive throwing / valgus stress and gymnastics / weight bearing on upper extremity
- valgus stress / compressive force on the vulnerable chondroepiphysis of the radiocapitellar joint in skeletally immature patients is supported as the etiology for OCD of the capitellum
- ankle sprain/instability
- In the talus, 96% of lateral lesions and 62% of medial lesions were associated with direct trauma
- competitive athletics
- family history: epiphyseal dysplasia has been postulated as a subset of OCD
Symptoms are variable and range from asymptomatic to significant pain and locking (suggesting loose body formation). Joint effusions and synovitis are often present.
The exact etiology is uncertain and controversial, with the majority of cases thought to be the result of trauma . In up to 40% of cases, patients give a history of trauma as the inciting event . Other postulated causes include :
Many joints can be affected, but typical locations include:
- femoral condyles are most common site accounting for ~95% of all cases: osteochondritis dissecans of the knee
- talus: osteochondritis dissecans of the ankle
- capitellum: osteochondritis dissecans of the elbow
Plain radiographs should be the first step in the evaluation of knee pain, however, unless advanced changes are present and/or a meticulous technique employed, early findings of osteochondritis dissecans may be occult. The intercondylar "notch" view is very helpful.
Early findings include subtle flattening or indistinct radiolucency about the cortical surface. As the process progresses, more pronounced contour abnormalities, fragmentation and density changes (both lucency and sclerosis) become evident. If an osteochondral fragment becomes unstable and displaced, then donor site and intra-articular fragment may be seen.
CT has the advantage of sectional imaging through the joint and multiplanar reformats. Findings are similar to those seen on plain radiographs.
MRI is the modality of choice, with high sensitivity (92%) and specificity (90%) in the detection of separation of the osteochondral fragment. This is essential in determining management.
- variable signal overall with intermediate to low signal adjacent to fragment and variable fragment signal
- the high signal line demarcating fragment from bone usually indicates an unstable lesion however false positives can result from edema
- low signal loose bodies, outlined by high signal fluid
- donor defect filled with high signal fluid
- high signal subchondral cysts
- enhancement indicates the viability of the lesion
The four classic signs of instability described at MRI include :
- high signal intensity rim at the interface between the fragment and the adjacent bone on T2-weighted MR image
- fluid-filled cysts beneath the lesion
- high signal intensity line extending through the articular cartilage overlying the lesion
- focal osteochondral defect filled with joint fluid, indicating complete detachment of the fragment
- persistent pain with activity: ~ 2/3 following surgical management of knee and 40% following surgical management of elbow
- articular incongruity
- early degenerative joint disease
Treatment and prognosis
Spontaneous healing is usual unless there is an unstable fragment, and treatment revolves around rest and immobilization for up to a year .
When the fragment is unstable or displaced, without treatment patients are susceptible to premature secondary osteoarthritis. Numerous surgical approaches have been tried, including drilling, bone grafting, replacement of bone fragment and pinning .
When surgery is performed, the results in most cases are only "fair". ~50% (range 35-70%) of patients achieve a "good to excellent" clinical outcome but even in these cases, the majority develop osteoarthritis.
History and etymology
It was first described by the German surgeon Franz Konig in 1888.
- normal irregular distal femoral epiphyseal ossification
- avascular necrosis
- osteochondral impaction fracture
- stress/insufficiency fracture