Acromial enthesopathy and rotator cuff tear. A radiologic and histologic postmortem investigation of the coracoacromial arch.

Changes of the coracoacromial ligament (CAL) at its insertion into the undersurface of the acromion were studied radiologically and histologically in 76 autopsy specimens. Two changes were noted: (1) a downward, bony projection of the acromion, an anatomic variant limited to the area covered by the CAL, which might reduce the height of the subacromial compartment, and (2) a thickened layer of fibrocartilage, constituting a potential cause for narrowing of the subacromial space. The former might act as a predisposing factor for the impingement syndrome, whereas the latter could develop in response to pressure from constituents of the subacromial compartment. The acromial spur was a result of enchondral bone formation. A possible correlation between these changes and rotator cuff tears was investigated. The incidence and severity of cuff tears increased with age. However, there was no correlation between aging and degenerative changes of the undersurface of the acromion, except possibly in very advanced cases. Rotator cuff tears are unlikely to be initiated by impingement; rather, they develop as an intrinsic degenerative tendinopathy.