Biomechanical characteristics of subscapularis-sparing approach for anatomic total shoulder arthroplasty

Abstract

Background: A technique for retaining the superior 50% of the subscapularis insertion for anatomic total shoulder arthroplasty has been described. This cadaveric study biomechanically evaluates this subscapularis-sparing approach and compares it with a complete subscapularis release and repair technique to determine whether there is a higher load to failure.

Materials and methods: Twelve matched pairs of human cadaveric arms were distributed into 3 test groups. Group 1 consisted of specimens with and without a 100% subscapularis release. Group 2 consisted of specimens with and without an inferior 50% subscapularis release. Group 3 consisted of specimens with either an inferior 50% or 100% release of the subscapularis footprint and repair. All tendon repairs were performed using bone tunnels and sutures. Specimens were biomechanically tested using non-destructive cyclic and tensile failure-inducing loads.

Results: In matched pairs, the following comparative results were obtained: native intact subscapularis specimens exhibited a load to failure of 1341.20 ± 380.10 N compared with 380.10 ± 138.79 N in the 100% release specimens (P = .029), native intact subscapularis specimens exhibited a load to failure of 1209.74 ± 342.18 N compared with 744.33 ± 211.77 N in the 50% release specimens (P = .057), and 50% release and repair specimens exhibited a load to failure of 704.62 ± 165.53 N compared with 305.52 ± 91.39 N in the 100% release and repair group (P = .029).

Conclusion: Preservation of the superior 50% of the subscapularis demonstrates a higher load to failure compared with complete subscapularis release and repair using bone tunnels.

Keywords: Shoulder arthroplasty; anatomic total shoulder arthroplasty; load to failure; rotator cuff–sparing approach; subscapularis tenotomy; subscapularis-sparing approach; tendon strength.