Humeral Capitellum Osteochondritis Dissecans

Background

In 1889, Francis Konig described osteochondritis dissecans as a subchondral inflammatory process of the knee resulting in a loose fragment of cartilage from the femoral condyle. Although no inflammatory cells have been identified on histologic sections of excised fragments, the term osteochondritis dissecans has persisted and since been broadened to describe a similar process occurring in many other joints, including the knee, hip, ankle, elbow, and metatarsophalangeal joints.[1, 2, 3, 4, 5, 6]

Humeral capitellum osteochondritis dissecans occurs after the capitellum has ossified and is the result of "injury" to the subchondral bone. The initial histologic appearance is consistent with avascular necrosis. The avascular necrosis of subchondral bone leads to loss of support for adjacent cartilaginous structures. The natural history of some osteochondritis dissecans lesions is the separation of these structures from the capitellum, leading to the development of an osteochondral fragment of articular cartilage on the underlying bone at the superficial surface of the diarthrodial joint.[7, 8, 9, 10]

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NextEpidemiologyFrequencyUnited States

Humeral capitellum osteochondritis dissecans comprises 6% of all osteochondritis dissecans cases.

In the United States, humeral capitellum osteochondritis dissecans most commonly occurs in the second decade of life and is rare in individuals younger than 10 years or older than 50 years. Humeral capitellum osteochondritis dissecans is primarily observed in children aged 10-15 years.

Approximately 85% of osteochondritis dissecans cases involve males, with a large proportion of these being Little League pitchers. Humeral capitellum osteochondritis dissecans is believed to affect 4.1 of every 1000 males. Among male relatives of affected males, the prevalence rate is 14.6%. Osteochondritis dissecans also occurs in females, most notably gymnasts. Finally, it also commonly occurs in persons who participate in racquet sports and in weight lifting.

Humeral capitellum osteochondritis dissecans usually occurs in the dominant arm. In up to 20% of cases, it occurs bilaterally.

PreviousNextFunctional Anatomy

While the trochlea of the distal humerus articulates with the sigmoid fossa of the proximal ulna, the capitellum of the distal humerus articulates with the head of the radius. These articulations, in conjunction with the radioulnar articulation, compose the elbow joint. The articulation of the radial head and humeral capitellum provides mobility for a wide range of supination and pronation, as well as flexion and extension. This area is thus particularly susceptible to the rotary, compressive, axial, and angular forces associated with activities such as throwing.

The radiocapitellar articulation is supported laterally by the radiocollateral, the accessory collateral, the lateral ulnar collateral, and the annular ligaments. These ligaments function to stabilize the elbow throughout the motions of pronation, supination, flexion, and extension.

PreviousNextSport-Specific Biomechanics

The exact etiology of osteochondritis dissecans is unclear.[1, 4, 5, 11, 12, 13] In overhead throwing, articular forces at the radiocapitellar articulation are significant. Progressive pronation, compression, and rotation occur on the anteromedial radial head and the inferior and medial aspects of the capitellum as the elbow is extended.

These forces are believed to lead to fibrillation on the articular surface and subchondral osseous changes, with the possible production of osteocartilaginous fragments and the development of humeral capitellum osteochondritis dissecans. The valgus orientation of the elbow contributes to these compressive loads. Excessive axial loading to the elbow is also believed to be the primary cause of injury in gymnasts and weight lifters.[14, 15]

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