Measurement of the anteroposterior translation of the humeral head using MRI.

Anteroposterior translation of the humeral head within the glenohumeral joint was investigated using MRI. Ten normal shoulders, 11 recurrent anterior dislocations, 10 stabilised shoulders after the Putti-Platt operation and one shoulder with multidirectional instability, were scanned. The arm was positioned in internal and external rotation and in an overhead position. Gradient echo volume acquisition scans were carried out, and 22 were suitable for evaluation. Consistent results were obtained in the normal shoulders. The unstable and unstable shoulders showed higher variance, but there was no significant anterior translation in external rotation in any group. The range of external rotation was significantly reduced in the unstable and stabilised shoulders. A trend towards posterior translation was found in internal rotation with a mean of 1 (+/- 0.44) in normal, 0.89 (+/- 1.67) in unstable and 1.6 (+/- 1.4) in stabilised shoulders.