Excessive retroversion of the glenoid cavity. A cause of non-traumatic posterior instability of the shoulder.

Seventeen shoulders in ten adolescents were evaluated for non-traumatic posterior instability. Each patient had significant disability in throwing a ball, swimming, arm-blocking in football, and bench-pressing weights. Each patient had excessive retroversion of the glenoid. Five shoulders had a posterior opening-wedge osteotomy of the scapular neck to correct the excessive retroversion of the glenoid cavity. Acromial bone was used as graft material in the first four shoulders. Three shoulders lost some correction but only one required revision, which was done using cortical iliac bone as a graft and screw fixation. This technique was used primarily in the fifth shoulder. Excessive retroversion of the glenoid cavity is a developmental deformity and is considered the primary etiology of posterior instability of the shoulder. The posterior opening-wedge osteotomy of the scapular neck corrects the defect and the instability.