INFLUENCE OF ROTATOR CUFF TEARING ON GLENOHUMERAL STABILITY

This study hypothesizes that full-thickness tearing of the rotator cuf f can lead to joint instability and that the degree of instability dep ends on the size and location of the tear. Twelve cadaveric shoulder s pecimens were divided into two groups: group 1 had a circular tear cen tered at the critical area, and group 2 had a circular tear centered a t the rotator interval. Each group was tested at 2.5 cm and 5 cm tear sizes. Unloaded, and with the arm in 90 degrees Flexion and full inter nal rotation, the humeral head shifted posteriorly. With loading, a la rge and more anteriorly located defect had the most influence on stabi lity. The fear size had the greatest effect on stability in the inferi or direction For group I and on the anterior direction for group 2. Th e tear location had the most significant effect on stability in the in ferior and anterior directions For the smaller tear and on the anterio r direction for a larger tear.