Anatomy and dimensions of rotator cuff insertions.

The purpose of this study was to devise and implement an accurate and reproducible method of measuring the area and dimensions of the rotator cuff tendon insertions and their distance from the articular surface. Twenty fresh-frozen cadaveric upper-extremity specimens were divided into 2 groups of 10. In group 1 the specimens were dissected, leaving only the most distal rotator cuff tendons attached to the humerus. The periphery of the insertion onto the greater tuberosity was marked at 3-mm intervals. The specimens were then mounted onto a custom jig, and the insertion was mapped by a 3-space digitizer. In group 2 the specimens were prepared by removing all tissues except the rotator cuff muscles and tendons and the joint capsule. The interval between the muscles of the rotator cuff was identified and marked. The rotator cuff muscles and tendons were then removed, leaving only the most distal tendons attached to the tuberosities. The periphery of the individual cuff insertions was then marked as in group 1 and mapped in the same fashion. The articular margin also was marked at similar intervals and mapped with the same technique. The area of insertion of the 3 tendons on the greater tuberosity averaged 6.24 cm(2) (SD, 2.04 cm(2)) in group 1. The mean minimum transverse dimension across the cuff insertion occurred in the mid portion of the supraspinatus, with a mean distance of 14.7 mm (SD, 3.22 mm). In group 2 the mean area of insertion of the supraspinatus was 1.55 cm(2) (range, 0.68-2.64 cm(2); SD, 0.66 cm(2)) and the mean area of insertion for the infraspinatus was 1.76 cm(2) (range, 1.23-2.53 cm(2); SD, 0.40 cm(2)). The distance from the articular margin to the most medial rotator cuff fibers was less than 1 mm along the anterior-most 2.1 cm of the cuff insertion onto the greater tuberosity. No correlation could be made between humeral head dimension and the dimensions of the rotator cuff insertions. The mean minimum medial-to-lateral distance across the rotator cuff insertion was sizeable, at 14.7 mm. This represents the minimum possible distance, as the mathematical calculation to determine the dimensions used a perpendicular measurement. The rotator cuff inserts very closely to the articular margin along the anterior 2.1 cm of the greater tuberosity. These anatomic measurements may be useful in evaluating and reattaching the rotator cuff to the humerus.