Correlation between external rotation of the glenohumeral joint and deformity after brachial plexus birth palsy.

The purpose of this study was to determine whether physical examination findings correlate with glenohumeral joint dysplasia after brachial plexus birth palsy. Thirty-three children with residual palsy underwent magnetic resonance imaging evaluation of both shoulders. Glenoscapular angles and humeral head measurements were calculated. Physical examination findings were recorded about the shoulder. Glenohumeral external rotation was measured during firm stabilization of the scapulothoracic joint. In the uninvolved shoulders, glenoscapular version averaged -8 degrees (range -16 degrees to -2 degrees) and percentage of humeral head anterior to the middle of the glenoid fossa (PHHA) averaged 45% (range 34-54%). In the involved shoulders, glenoscapular version averaged -24 degrees (range -64 degrees to -7 degrees) and PHHA averaged 28% (range 0-51%). Both version and subluxation were significantly different (P < 0.001) between uninvolved and involved shoulders. There was a significant correlation between version and subluxation (r = 0.91, P < 0.001). Humeral head size was significantly less (P < 0.001) on the involved shoulder. Progressive loss of external rotation beyond neutral correlated with increased angles of retroversion and increased posterior subluxation of the humeral head and should be regarded as in indicator of shoulder malformation.