The “comma sign”: an anatomical investigation (dissection of the rotator interval in 14 cadaveric shoulders)

Purpose The aim of the present study was to describe the precise anatomy of the so-called “Comma Sign” which has been observed during arthroscopy in retracted subscapularis (SSC) tears. Methods Fourteen fresh cadaveric shoulders were prepared to obtain an articular view comparable to arthroscopic posterior portal view. A step-by-step dissection was carried out to verify the presence of any anatomic structure inserting directly on the lateral margin of the SSC tendon. A sequential detachment of the superior gleno-humeral ligament (SGHL), the coraco-humeral ligament (CHL), and the SSC tendon from their bony humeral insertions was performed. Under intra-articular and extra-articular view, the SSC and its connections with the supraspinatus (SS), the SGHL and the CHL were evaluated. Results The detachment of the CHL and the SGHL from the humerus did not reveal any structure directly inserted on the superior-lateral margin of the SSC tendon. However, when the SSC tendon was excised from the lesser tuberosity and pulled medially, a bundle of fibers, which inserted directly onto its superior-lateral edge, was constantly observed. Conclusions We constantly found an effective link between the superior-lateral corner of the SSC tendon and a bundle of fibers coming from SS and CHL. It became visible only after medial traction of the detached SSC. This structure yields the “Comma Sign” in subscapularis tendon tears.