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

BACKGROUND

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.

MATERIALS AND METHODS

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.

RESULTS

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.

DISCUSSION

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.