Humeral Capitellum Osteochondritis Dissecans

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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United States data

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.[11]

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.[12] 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.

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.

The exact etiology of osteochondritis dissecans is unclear.[1, 4, 5, 13, 14, 15] 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.[16, 17]

The typical presentation is that of a young adolescent reporting elbow pain.[3, 18, 19, 20] The pain is usually characterized as dull and poorly localized. The patient reports aggravation with use (particularly throwing) and good relief with rest. Pain can also result from other activities, such as wrestling, football, tennis, basketball, golf, shot-putting, and gymnastics. In extreme cases, the elbow flexion contracture may be 15° or more, related to the possible presence of a loose body, overuse, or pain related to the osteochondritis dissecans lesion. Presence of a loose body may also result in catching and locking sensation at the elbow.

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Ischemic

Repetitive valgus loading may injure the limited vascular supply to the distal humerus, thus leading to avascularity in the region.

Activities such as pitching are often associated with repetitive overuse that leads to valgus compressive forces being generated across the radiocapitellar joint and, thus, induce changes in the distal humerus that cause osteochondritis dissecans.

A similar mechanism is noted in gymnasts. Gymnasts bear their entire body weight on their arms and expose the elbows to repetitive compressive forces.

Trauma

This is usually the result of repetitive microtrauma, as described above or, less frequently, the result of single traumatic insult.

Genetic predisposition

Osteochondritis dissecans is often seen in several generations of the same family.

Osteochondritis dissecans frequently occurs within multiple joints in a given patient.

Early findings

Early findings include the following:

• Local tenderness over the lateral aspect of the elbow, most typically in the dominant arm

• Swelling

• Intermittent limitations with range of motion (ROM) that are worse with activity

Late findings

Late findings include the following:

• Joint effusion

• More progressive limitation of elbow movement (loss of extension, usually 5-10°)

• Crepitus with motion

• Muscle atrophy

• Catching and locking of the elbow (usually observed with separation of osseous/cartilaginous fragments)

Anteroposterior (with elbow at 45° of flexion) magnetic resonance imaging (MRI)/lateral radiography

Plain radiography should be the primary imaging study obtained in all cases of humeral capitellum osteochondritis dissecans. Initially, radiographs appear without abnormalities. Early in the course of progression of humeral capitellum osteochondritis dissecans, changes are confined to the humeral capitellum. Changes may include patchy rarefaction consisting of a sclerotic rim of subchondral bone adjacent to the articular surface, irregular ossification, and/or a bony defect adjacent to the articular surface. Lateral radiographs may show flattening of the capitellum.

With the further passage of time, the radiographic appearance is based on whether separation of osteochondral fragments occurs. Without separation, the central sclerotic fragment becomes less distinctive, the rarefaction area ossifies, and the lesion slowly heals. However, with separation, loose bodies may be visualized within the joint. Note that only 30% of loose bodies are usually observed on plain radiography.

In the late stages of humeral capitellum osteochondritis dissecans, one is likely to see radial head enlargement, premature distal humeral physeal arrest, and degenerative changes leading to incongruity between the articulation of the radial head and the humeral capitellum.

Computed tomography (CT) scanning

CT scanning helps to determine changes in bony anatomy. Specifically, an island of subchondral bone demarcated by a rarefied zone should be observed.

MRI

MRI, specifically T1-weighted images showing low-signal changes at the surface of the capitellum, can be useful for early detection of humeral capitellum osteochondritis dissecans. MRI also assists in determining the size and extent of the lesion and the vascular supply to the area. On T2-weighted images, unstable lesions (those with loose fragments) are noted to have pockets of high signal (fluid) surrounding the displaced fragments.

Contrast arthrography

Contrast arthrography provides additional information about the size and extent of the lesion. It can help in assessing loose fragments and in assessing any other articular abnormalities.

Ultrasonography

Ultrasonography shows localized capitellar bony flattening, which is useful in early detection.[21] Nondisplaced fragments appear as double high–echogenic areas in the capitellar subchondral bone. Displaced free bone is detected as highly echogenic fragments overlying intact subchondral bone.

Arthroscopy

Arthroscopy can be used as a diagnostic tool, although its lack of sensitivity for early lesions predisposes to a high rate of false-negative results.

Rehabilitation program

Occupational therapy

In patients with intact humeral capitellum osteochondritis dissecans lesions that are a cause of significant pain, the primary focus should be limitation of activity, rest, application of ice, and adequate pain control.[22] Consider placing the patient in a sling for pain relief only. If pain persists, occupational therapy for splinting/casting may be indicated; however, prolonged splinting or casting is not usually necessary and may increase the risk of a flexion contracture. The use of modalities such as ice may also be beneficial for pain relief.

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Surgical intervention

Surgical intervention is indicated in cases of progressive joint contracture, failed conservative treatment, partially attached or completely detached fragments, or locking and catching of the joint with extension and/or flexion.

Arthroscopy for excision of the loose body and abrasion chondroplasty is preferred, with conversion to an open procedure if necessary. Surgical fixation of the loose body may be attempted.

Radial head excision is recommended in older patients who have a radial head deformity, radiocapitellar degenerative changes, or limitation of forearm rotation. Anterior capsule release may help to relieve flexion contractures.

Arai et al developed an arthroscopic-assisted drilling method for humeral capitellum osteochondritis dissecans lesions.[23] The method involves drilling through the radius in a distal-to-proximal direction with the use of a single 1.8-mm Kirschner (K)-wire that is "inserted from the shaft of the radius approximately 3 cm distal to the humeroradial joint into the joint" as well as with the guidance of arthroscopy.

The forearms were supinated with the tip of the K-wire at the lateral side of the lesion. Drilling was performed at 30º elbow flexion, which was to 60º to 90º to 120º while maintaining supination, to drill in 4 sites (1 site for each angle of flexion) of the lateral side of the lesion. Then, the forearm was moved from supination to pronation so that the tip of the K-wire was placed in the medial side of the lesion in the humeral capitellum, and as with the lateral side, drilling was performed in 4 sites. The investigators noted that the procedure allows the entire lesion to be drilled, is minimally invasive, and may allow the athlete to return to sports earlier.[23]

Nobuta et al evaluated the efficacy of fragment fixation in 28 cases of humeral capitellum osteochondritis dissecans. The investigators noted that post surgery, 25 patients reported no pain and 3 reported decreased pain. The average arc of flexion improved 16º compared with the pre-operative arc, and "radiographic findings showed complete healing of the lesion in 11 patients, partial healing in 12, unchanged in 3, and loose body formation in 2."[24]

The ratio of complete or partial healing of the lesion appeared to be related to the preoperative radiographic findings of the lesion's thickness. In 16 patients in whom the thickness of the lesion was less than 9 mm on preoperative radiograph, there was 100% complete or partial healing, whereas it was 58% in 12 patients in whom the lesion thickness was 9 mm or more. Thus, Nobuta et al observed that fragment fixation is effective when humeral capitellum osteochondritis dissecans lesions are less than 9 mm thick, and "fixation by flexible wire or thread and revascularization by drilling for the fragment" are likely insufficient for large lesions with a thickness of 9 mm or more.[24]

Takahara et al evaluated the outcomes and determined the most useful classification the treatment of choice for humeral capitellum osteochondritis dissecans lesions.[13, 14] The investigators classified the lesions as stable or unstable. The findings at the initial presentation appeared to be useful in determining whether conservative (elbow rest) or surgical treatment would provide a better outcome for certain lesions.

Takahara et al concluded that at the time of the initial presentation stable humeral capitellum osteochondritis dissecans lesions that healed completely with elbow rest had: (1) an open capitellar growth plate, (2) localized flattening or radiolucency of the subchondral bone, and (3) good elbow motion. However, unstable lesions, for which surgery provided significantly better results, had 1 of the following: (1) a capitellum with a closed growth plate, (2) fragmentation, or (3) restriction of elbow motion of ≥ 20º. Furthermore, for "large unstable lesions, fragment fixation or reconstruction of the articular surface" led to better results than simple excision.[13, 14]

Rehabilitation program

Occupational therapy

Begin with passive ROM exercises, followed by active ROM exercises to prevent contractures. As the patient gets stronger and can tolerate more activity, proceed with progressive resistive exercises. Electrical stimulation may also facilitate recovery, although this has not been proven in clinical trials.

Medical issues/complications

Restrict activity for 6-8 weeks after symptom resolution.

Rehabilitation program

Occupational therapy

Continue with ROM and strengthening exercises for the elbow. Take measures to protect the elbow from further injury. Advise patients of the importance of a shoulder program as well as a wrist/finger program. These programs should also focus on ROM and strengthening exercises.

Medical issues/complications

Return to activity is gradual. Full activity may be resumed at 6 months with complete symptom resolution. Follow-up radiography to assess healing is recommended before a return to full activity. Immediate cessation of activities and reevaluation is warranted if symptoms recur.

In general, once a patient with humeral capitellum osteochondritis dissecans is healed, his or her activity level should be gradually advanced. If symptoms recur, then activity modifications and/or limitations must be made. With intact lesions, return to competitive sports is likely, although the prognosis for pitchers and gymnasts is more guarded. In lesions in which completely detached osteochondral fragments are identified, studies have shown tremendous variability in a patient's ability to return to competitive athletics.

If the patient reports a locking and catching sensation, the physician must evaluate with MRI or CT arthrography for partially attached or completely detached fragments, even if the initial workup (ie, plain radiography) suggested an intact lesion.

Patients can be left with decreased ROM at the elbow, particularly loss of full extension. Patients also report pain with effort, especially with heavy lifting. Many report mild weakness. Long-term sequelae also include traumatic arthritis, increased diameter of the radial head, and early physeal closure of the radial head.

The best method of prevention of humeral capitellum osteochondritis dissecans is to avoid the repetitive compressive forces that are associated with athletics and heavy labor. Maintaining guidelines such as limiting a pitcher's innings and mandatory rest between pitching appearances is extremely important for injury prevention. Following recommendations for maintenance therapy is also important upon return to activity.

Prognosis is largely dependent on the patient's age and the size and extent of the lesion. Individuals diagnosed at a younger age tend to have more favorable outcomes.[25] Lesions with large fragments that require surgery and those discovered in late adolescence are more prone to the development of traumatic arthritis. In cases in which the diagnosis is made early, the elbow can usually be returned to a functional level.

Advising parents and children about the potential pitfalls of overuse is important. They must be taught to use good judgment and to take appropriate precautions, such as limiting the pitch count of Little League pitchers (see the 2004 USA Baseball Medical & Safety Advisory Committee recommendations for youth pitch counts).

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