Recurrent anterior glenohumeral instability with onset after forty years of age: the role of the anterior mechanism

Recurrent instability in patients over forty years of age is felt to occur primarily as a result of an associated rotator cuff tear. This is often referred to as the "posterior mechanism." We reviewed our patients over the age of forty who underwent an anterior shoulder repair to identify the incidence of capsulolabral detachments and the role of an "anterior mechanism" in this patient population. A retrospective review of all patients from 1985 to 2000 was performed to identify patients who had surgery for recurrent instability that began after forty years of age. Of the 265 patients records reviewed, 11 patients were identified who fulfilled the inclusion criteria. Of the 11 patients identified, 9 patients underwent anterior capsulolabral reconstruction for recurrent instability; the remaining two patients underwent repair of large rotator cuff tears. All 9 patients had a capsulolabral detachment, 4 had a rotator interval defect, 2 had anterior and inferior capsular redundancy, 1 had a small rotator cuff tear and 1 had an anterior capsular avulsion from the humeral head. At minimum follow-up of 32 months none of the patients reported episodes of instability. The reported incidence of rotator cuff tears in patients over the age of forty following an initial traumatic anterior glenohumeral dislocation ranges from 35% to 100%. When recurrent instability occurs, it is postulated to occur via a "posterior mechanism" (i.e., secondary to a significant full-thickness rotator cuff tear). However, all of our patients had an anterior capsulolabral detachment as the "common lesion" associated with recurrent instability. Although small, this series emphasizes the role of the "anterior mechanism" in patients who develop recurrent instability after the age of forty. A high rate of success was achieved by addressing the pathoanatomic changes identified.