Biomechanics of Subscapularis Repair

Buraimoh MA, Okoroha KR, Oravec DJ, Peltz CD, Yeni YN, Muh SJ.  A biomechanical comparison of subscapularis repair techniques in total shoulder arthroplasty: lesser tuberosity osteotomy versus subscapularis peel.  JSES Open Access. 2018 Feb 1;2(1):8-12

Abstract

Background: The subscapularis peel (SP) and the lesser tuberosity osteotomy (LTO) are 2 common exposure techniques for total shoulder arthroplasty. Although some biomechanical studies have suggested a higher resistance to failure with the LTO, clinical studies have demonstrated no difference in repair failure or tendon healing. We hypothesized that there would be no difference in biomechanically tested repair strength between our SP technique and the previously tested LTO technique.

Methods: Eleven cadaver shoulders were separated into 2 groups: 6 SPs and 5 LTOs. After initial loading for 3000 cycles, the specimens were incrementally loaded to 450 ± 50 N or catastrophic failure. Repair gapping was measured after cyclical loading, and fatigue life was analyzed after incremental loading.

Results: There was no significant difference in mean repair gapping between the SP (2.40 ± 0.36 mm; mean ± standard deviation) and the LTO groups (3.10 ± 2.93 mm; P = .57). There was also no difference in the mean number of cycles to failure (6894 ± 956 vs. 6018 ± 1179; P = .14) and mean load to failure (400 ± 79 N vs. 340 ± 91 N; P = .21) between the SP and LTO techniques. However, there was more variability in bead gapping in the LTO group (P < .01).

Conclusion: No significant differences were found in repair gapping, fatigue failure, and load to failure in comparing the SP and LTO repairs. However, the SP repair demonstrated significantly less variability in repair gapping. These findings suggest that initial fixation biomechanical properties between the 2 constructs are similar in vitro.