Fascial bundles of the infraspinatus fascia: anatomy, function, and clinical considerations

The infraspinatus fascia is a tough sheet of connective tissue that covers the infraspinatus fossa of the scapula and the muscle within. Muscle fibers originate from the fossa and fascia and then travel laterally to insert on the greater tubercle of the humerus. Frequently the infraspinatus fascia is quickly removed to appreciate the underlying muscle, but the fascia is an interesting and complex structure in its own right. Despite having a characteristic set of fascial bundles, no contemporary anatomy texts or atlases describe the fascia in detail. The infraspinatus fascia was dissected in detail in 11 shoulders, to characterize the fascial bundles and connections that contribute to it. Thereafter, 70 shoulders were dissected to tabulate the variability of the fascial bundles and connections. Six characteristic features of the infraspinatus fascia were noted: a medial band, an inferior-lateral band, and superior-lateral band of fascia, insertion of the posterior deltoid into the infraspinatus fascia, a transverse connection from the posterior deltoid muscle to the infraspinatus fascia, and a retinacular sheet deep to the deltoid and superficial to the infraspinatus and teres minor muscles. Although other structures of the shoulder are more frequently injured, the infraspinatus fascia is involved in compartment syndromes and the fascial bundles of this structure are certain to impact the biomechanical function of the muscles of the posterior shoulder.