Muscle imbalance at the shoulder may lead to internal rotation contracture of the shoulder and to posterior dislocation of the head of the humerus (Figure 261.1). Posterior dislocation of the head of the humerus requires articuloplasty and release of the muscle contracture that led to it. Lengthening of the subscapularis muscle tendon usually achieves shoulder muscle balance without causing an unstable shoulder. Flexion contracture of the elbow, and supination or pronation deformities of the forearm may also occur and require surgical management.

A	B

Figure 261.1.— Posterior subluxation of the humerus. [A] Special “Y” scapular view. [B] MRI showing posterior incongruency between the articular faces.

The possibility of surgical reconstruction of the plexus or neurolysis of the neuroma should be considered in patients who do not recover. The neuroma results from scarring and aberrant axonal growth at the site of injury (Figure 261.2).

Figure 261.2.— Neuroma of the brachial plexus.