Osteochondritis Dissecans of the Capitellum

Osteochondritis dissecans of the capitellum is one of the most important causes of lateral elbow pain in the adolescent athlete. It is distinct from Panner disease (younger age, entire capitulum, self-limiting). The key clinical decision is determining whether the lesion is stable (treated with rest) or unstable (requiring surgery). MRI is the gold standard for this distinction. Delayed diagnosis in unstable lesions risks loose body formation, progressive arthritis, and career-ending elbow dysfunction in young athletes.

Any adolescent overhead athlete or gymnast with lateral elbow pain and loss of extension needs AP and lateral elbow radiographs, and if suspicious, an MRI to assess the capitellum. Do not dismiss lateral elbow pain in a young thrower as "growing pains" or "muscle strain." Early-stage OCD is reversible with rest; late-stage OCD may end an athletic career.

Q: A 12-year-old baseball pitcher has lateral elbow pain. Radiographs show a radiolucent lesion in the capitellum. What is the next most appropriate investigation? A: MRI of the elbow. MRI is the gold standard for staging capitellar OCD. It determines whether the lesion is stable (intact cartilage, no fluid behind fragment) or unstable (disrupted cartilage, fluid behind fragment), which directly guides management.

Q: A 7-year-old presents with lateral elbow pain. Radiographs show flattening and fragmentation of the entire capitulum. No loose bodies are seen. What is the diagnosis? A: Panner disease. Age under 10, involvement of the entire capitulum, and absence of loose bodies are characteristic. Panner disease is an osteochondrosis (analogous to Perthes disease of the hip) and is self-limiting with rest. No surgery is indicated.

Q: What is the most important conservative measure for stable capitellar OCD? A: Complete cessation of the offending activity (throwing, gymnastics, weight-bearing). Partial rest (reducing but not stopping activity) often fails. A minimum of 3 months of complete activity restriction is required, with repeat MRI to assess healing before gradual return.

Q: What MRI finding indicates that a capitellar OCD lesion is unstable and likely requires surgery? A: Fluid signal (high T2 intensity) between the fragment and the underlying bone, indicating disruption of the articular cartilage and fragment mobility. This is the most reliable MRI sign of instability. Other signs include displaced fragments and loose bodies.

Q: Why is the capitellum vulnerable to OCD in young athletes? A: The capitellum has limited end-arterial blood supply and is almost entirely covered by articular cartilage, restricting vessel access. In skeletally immature athletes, the ossification centre is still developing. Repetitive compressive loading at the radiocapitellar joint (valgus stress in throwing, axial loading in gymnastics) causes microtrauma and ischaemia in the vulnerable subchondral bone.

Q: What is the typical timeline for return to sport after surgical fixation of an unstable capitellar OCD lesion? A: 6-9 months after confirmation of fragment union on imaging. Rehabilitation involves 6 weeks of protected motion, followed by progressive strengthening and gradual return to throwing or gymnastics over months. Return to the same competitive level is not guaranteed.