The influence of the acromial coverage index in rotator cuff tears.

Several intrinsic and extrinsic factors have been advocated in the pathogenesis of rotator cuff tears, but it is still unclear whether the origin of the tear is related to tendon degeneration itself or induced by several morphologic changes. The purpose of this study is to determine the relationship between the acromial coverage of the humeral head and the presence of a cuff tear. We evaluated 148 shoulders, including 45 that underwent surgical rotator cuff repair (group I), 26 with documented rotator cuff tears treated conservatively (group II), and 77 with no cuff pathology as a control group (group III). The mean acromial coverage index was 0.68 in group I, 0.72 in group II, and 0.59 in group III, giving a highly significant difference (P < .0001) between the control group and both cuff tear groups. Patients with a cuff tear have a significantly higher acromial coverage index than the control group.