Humeral Insertion of the Supraspinatus and Infraspinatus. New AnatomicalFindings Regarding the Footprint of the Rotator Cuff

Background It is generally believed that the supraspinatus is themost commonly involved tendon in rotator cuff tears. Clinically, however,atrophy of the infraspinatus muscle is frequently observed in patients witheven small to medium-size rotator cuff tears. This fact cannot be fullyexplained by our current understanding of the anatomical insertions of thesupraspinatus and infraspinatus. The purpose of this study was toreinvestigate the humeral insertions of these tendons. Methods The study included 113 shoulders from sixty-four cadavers.The humeral insertion areas of the supraspinatus and infraspinatus wereinvestigated in ninety-seven specimens. In sixteen specimens, all muscularportions of the supraspinatus and infraspinatus were removed, leaving thetendinous portions intact, in order to define the specific characteristics ofthe tendinous portion of the muscles. Another twenty-six shoulders were usedto obtain precise measurements of the footprints of the supraspinatus andinfraspinatus. Results The supraspinatus had a long tendinous portion in theanterior half of the muscle, which always inserted into the anteriormost areaof the highest impression on the greater tuberosity and which inserted intothe superiormost area of the lesser tuberosity in 21% of the specimens. Thefootprint of the supraspinatus was triangular in shape, with an averagemaximum medial-to-lateral length of 6.9 mm and an average maximumanteroposterior width of 12.6 mm. The infraspinatus had a long tendinousportion in the superior half of the muscle, which curved anteriorly andextended to the anterolateral area of the highest impression of the greatertuberosity. The footprint of the infraspinatus was trapezoidal in shape, withan average maximum medial-to-lateral length of 10.2 mm and an average maximumanteroposterior width of 32.7 mm. Conclusions The footprint of the supraspinatus on the greatertuberosity is much smaller than previously believed, and this area of thegreater tuberosity is actually occupied by a substantial amount of theinfraspinatus. Level of Evidence The present study suggests that rotator cufftears that were previously thought to involve only the supraspinatus tendonmay in fact have had a substantial infraspinatus component as well. Original Abstract Citation “Humeral Insertion of the Supraspinatus and Infraspinatus. New Anatomical Findings Regarding the Footprint of the Rotator Cuff” (2008;90:962-9).