Experiments on the tensile strength of the anterior capsular structures of the shoulder in man.

It has been demonstrated arthrographically that two types of acute dislocation of the shoulder occur in man (Reeves 1966). One is capsular rupture and the other is intracapsular dislocation. The age distribution is different in the two groups of patients: capsular rupture is predominantly an injury of the elderly, whereas intracapsular dislocation, in which the glenoid labrum or capsule is avulsed in continuity with the periosteum, is an injury of the young (Fig. I ). This observation suggested that there might be some alteration with age in the relative strength of the various components of the anterior retaining structures, which were called the anterior capsular mechanisms by Townley (1950). To investigate this matter, the tensile strengths of the subscapularis tendon and of the antero-inferior part of the capsule have been tested under a slowly increasing load and under a rapidly applied load. The strength of the glenoid labral attachment has also been tested by slow application of a shearing force to the labrum immediately above its attachment.