Biomechanical Study of a Subscapularis Repair Technique for Total Shoulder Arthroplasty.

Abstract

Secure subscapularis repair is an essential element of total shoulder arthroplasty. Some surgeons prefer subscapularis peel because of ease of use, but some evidence suggests that lesser tuberosity osteotomy provides better fixation. The authors developed a novel, through-implant repair technique and performed a biomechanical study of its strength with cadaveric specimens. The authors obtained 20 matched pairs of cadaveric shoulders and inserted an uncemented short-stemmed humeral prosthesis that facilitates through-implant repair in all specimens. For each cadaver, the subscapularis was repaired with lesser tuberosity osteotomy and standard suture technique on 1 side, and the contralateral subscapularis was repaired with a novel through-implant suture repair and subscapularis peel technique. Displacement of the subscapularis footprint, ultimate load to failure, and stiffness of each repair were measured and compared between fixation groups. Mean±SD displacement of the lesser tuberosity osteotomy group was 0.75±0.94 mm at 10 cycles and 2.24±2.76 mm at 500 cycles. Mean±SD load to failure was 612±185 N, and mean±SD ultimate stiffness was 119±32 N/mm. No significant differences were noted between the lesser tuberosity osteotomy group and the subscapularis peel group in mean±SD displacement at 10 cycles (1.09±1.30 mm, P=.31), mean±SD displacement at 500 cycles (2.85±2.43 mm, P=.26), mean±SD load to failure (683±274 N, P=.31), or mean±SD ultimate stiffness (117±37 N/mm, P=.88). In a biomechanical testing model, through-implant subscapularis repair provided secure fixation relative to currently accepted subscapularis repair techniques in total shoulder replacement. [Orthopedics. 2016; 39(5):e937-e943.].