Definitions and Epidemiology
Although epiphysiolysis of the proximal humerus occurs primarily in young baseball players, it has also been reported in cricket (fast bowlers), volleyball, swimming, gymnastics, and racquet sports.1,2 The proximal humeral physis accounts for 80% of the longitudinal growth of the humerus. In sports involving overhead throwing, the physis is subjected to significant amount of stress, leading to microtrauma, throwing-related pain, and characteristic changes seen on the radiographs. This is classically described as the “little leaguer's shoulder,” because of its original description in little league pitchers.
It is unclear whether the underlying changes represent inflammation caused by overuse or stress fracture through the physis. The mechanism is believed to be repetitive, high intensity, rotational stress to the physis during throwing, and other overhead activities.
The head of the humerus develops from two ossification centers that fuse into one at 7 years of age. The proximal physis of the humerus closes between 19 and 22 years of age; most close by 17 years of age. This injury pattern is most common during rapid growth, and occurs most often in adolescent boys, between the ages 11 and 16 years, with a peak at 14 years. In baseball pitchers, throwing a curve ball and higher pitch counts have been shown to be associated with a higher rate of stress injury to the proximal humeral physis. Most throwers demonstrate excessive external rotation at shoulder, whereas the internal rotation is relatively restricted, accompanied by acquired contracture of the posterior capsule, a maladaptation referred to as the glenohumeral internal rotation deficit.
The athlete typically presents with a gradual onset of shoulder or proximal arm pain associated with throwing. The average duration of symptoms ranges from 7 to 8 months. Often, the symptoms are mild lasting for several weeks to months, and there is pressure to continue to play, thus, there is a delay in seeking medical help. Tenderness over the lateral aspect of the proximal humerus is the most common finding on examination, and may be present in almost 70% of athletes.2–4 A few athletes may have weakness of external rotators of shoulder. Usually, the active and passive range of motions of shoulder is normal, until later in the course, when a relative decrease of internal rotation develops.
The radiographic findings are characteristic and seen in almost all athletes at the time of presentation. Radiographs with shoulder in external and internal rotation, as well as AP and lateral views should be obtained. Comparison views of the opposite shoulder should also be obtained. The classic finding is a widening of the proximal physis, which may or may not be associated with fragmentation, calcification, sclerosis, and demineralization (Figure 21-1).