Arthroscopic visualization of the subscapularis tendon

Purpose: This study was conducted to define what portion of the subscapular is, tendon is visualized during standard diagnostic glenohumeral arthroscop y and to determine the distance between the inferior aspect of the visible portion of the subscapularis tendon and the axillary nerve. Type of Study: Anatomic (cadaveric) analysis. Methods: Six fresh-frozen human cadaveric sh oulders were placed in a simulated lateral decubitus position with longitud inal traction and 45 degrees of shoulder abduction. Glenohumeral arthroscop y was performed on each specimen using a standard posterior portal for visu alization. The 4 corners of the visible portion of the subscapularis were t agged with arthroscopic sutures. The shoulders were subsequently dissected. The surface area defined by the 4 suture tags and the surface area of the entire subscapularis tendon were calculated for each specimen. The dimensio ns of these areas and the distance between the inferior aspect of the visib le portion of the subscapularis tendon and the axillary nerve were measured with calipers. Results: The arthroscopically tagged portion of the subscap ularis tendon represented only a small percentage (26%+/- 11%) of the entir e tendon. The majority of the subscapularis tendon is veiled by the middle and inferior glenohumeral ligaments. There was a significant distance betwe en the inferior aspect of the visible portion of the subscapularis tendon a nd the axillary nerve (32.8 +/-6.0 mm). The mean height of the visible port ion of the tendon represented 44% of the mean overall height of the subscap ularis. Conclusions: These data suggest that arthroscopic visualization of the subscapularis is incomplete. Lesions involving the concealed portion of the subscapularis tendon may not be detected arthroscopically. The wide ma rgin of safety between the inferior aspect of the visible portion of the su bscapularis tendon and the axillary nerve is relevant to the placement of a nteroinferior (trans-subscapularis) arthroscopy portals as well as to perfo rming arthroscopic anterior capsular releases.