The coracoacromial ligament: anatomical and biomechanical properties with respect to age and rotator cuff disease

The coracoacromial ligament (CAL) plays an important role in the pathoetiology of the subacromial impingement syndrome especially in those patients who do not have bony abnormalities. A total of 40 shoulders were dissected to determine the anatomical and biomechanical properties of the CAL in shoulders with either intact rotator cuffs or rotator cuff disease, taken from cadavers of persons who were of various ages at death. The specimens from cadavers with rotator cuff degeneration had a shorter lateral and medial band of the CAL than those of the specimens taken from shoulders with intact rotator cuffs. The cross-sectional area of the lateral band was also enlarged in older specimens with rotator cuff degeneration. Analysis of the structural properties showed a higher load to failure and a higher stiffness in the younger than in older specimens. In material properties, there was a higher failure stress in specimens with normal rotator cuffs than in the specimens with rotator cuff disease but only in older specimens. The decreased material properties in older specimens with rotator cuff disease may be caused by the previously reported histological differences with tissue disorganization and a lack of parallel bundle orientation associated with rotator cuff disease.