The subscapularis footprint: an anatomic description of its insertion site

The purpose of this study was to describe the anatomic footprint of the subscapularis tendon.

We examined 19 cadaveric shoulder specimens in this study. Dissection was carried out to the level of the subscapularis through a deltopectoral approach. The subscapularis tendon was identified, and the dissection was continued, elevating the tendon, subperiosteally, from its insertion site at the lesser tuberosity. The dimensions of the footprint were measured superior to inferior, as well as medial to lateral, by a single observer.

The insertion of the subscapularis tendon on the lesser tuberosity was trapezoidal in shape. The mean length of the subscapularis tendon footprint was 2.5 cm (range, 1.5 to 3.0 cm). The superior portion of the footprint was the widest part of the subscapularis insertion. The mean width at the most superior aspect of the insertion site was 1.8 cm (range, 1.5 to 2.6 cm). The most inferior aspect of the footprint was much narrower, with a mean width of 0.3 cm (range, 0.1 to 0.7 cm).

The subscapularis insertion footprint has a broad and wide superior attachment that narrows distally to form a trapezoidal shape. We found the mean length of the footprint to be 2.5 cm. The mean superior width of the footprint was 1.8 cm, which was maintained for the upper 60% of the tendon insertion, at which point the footprint began to rapidly narrow to a minimum width of 0.3 cm at its most inferior aspect. The upper 60% of the footprint provided by far the major surface area for tendon insertion, consistent with prior findings of superior load transmission at the superior aspect of the footprint.

This broad attachment site superiorly is likely important in load transmission. Knowledge of the shape of the footprint of the subscapularis, with a broad superior attachment, makes it easier for the surgeon to perform an accurate anatomic surgical reconstruction of the torn subscapularis.