Abstract
A posterior instability of the shoulder is often found in the shoulder joint having slackness in the joint capsule and/or any defect of the postero -inferior margin of the glenoid. On the contrary, reports of posterior dislocation are very rare.
The purpose of this study was to clarify, through our clinical experiences of unstable shoulder, the causes of posterior instability of the shoulder. This is often observed in two groups, those of either “loose shoulder” or “posterior dislocation”. Since 1978, we have treated, with glenoid osteotomy including postero-inferior repair of the glenoid, 39 loose shoulders having the tendency of posterior instability and 14 shoulders with posterior dislocation. There was no significant difference in age or sex in the two groups. The results have been good in 80% of the cases.
Our findings were that obvious retrotilt and shortening of the transverse diameter on the glenoid are found in posterior dislocation. Hypo- or dysplasia of the postero-inferior margin of the glenoid can be one of the causes of posterior instability in loose shoulder.
