Partial subscapularis release for total shoulder arthroplasty: a biomechanical comparison of two techniques

Glenohumeral joint exposure during total shoulder arthroplasty (TSA) is obtained by releasing the subscapularis (SSC) with either an osteotomy or a tenotomy. Recently, concerns regarding SSC dysfunction after TSA have been raised. In order to avoid this complication, alternative surgical approaches that release the inferior 50% or 10% of the tendon have been described. While a 10% release of the SSC would theoretically lower the likelihood of postoperative SSC dysfunction, releasing 50% would provide greater surgical exposure but possibly have a weaker SS attachment. Therefore, we sought to compare the SSC attachment strengths of these two techniques.

Each of eight matched pairs of cadaveric shoulders were tested. The inferior 10% of the SSC tendon was released on one side. On the contralateral side, the inferior 50% of the SSC was released and then repaired with a 5.5 mm suture anchor. The specimens were then mechanically tested to failure.

The load to failure for the 10% release specimens was 682 ± 153 N and 493 ± 212 N for the 50% release specimens (p = 0.036). Failures in both groups occurred mainly at the musculotendonous junction.

The SSC humeral attachment strength after releasing the inferior 10% was 30% greater than the 50% re- lease with repair. Thus, although releasing the inferior 50% of the SSC tendon may provide greater surgical exposure, maintaining the SSC with minimal release may be preferable in decreasing the rate of post TSA SSC dysfunction.