Deformities of the shoulder in infants younger than 12 months with an obstetric lesion of the brachial plexus

We performed a prospective study using MRI in 16 consecutive infants with a mean age of 5.2 months (2.7 to 8.7) who had shown inadequate recovery from an obstetric lesion of the brachial plexus in the first three months of li fe, in order to identify early secondary deformities of the shoulder. Shoul ders were analysed according to a standardised MRI protocol. Measurements w ere made of the appearance of the glenoid, glenoid version and the position of the humeral head, The appearance of the glenoid on the affected side was normal in only seven shoulders. In the remainder it was convex in seven and bioconcave in three . The degree of subluxation of the humeral head was significantly greater ( p = 0.01) in the affected shoulders than in normal shoulders (157 degrees v 170 degrees). The presence of an abnormal appearance of the glenoid, retro version of the glenoid and subluxation of the humeral head increased with a ge, There was a statistical difference (p = 0.05) between infants younger t han five months and those who were older.