A New Approach to Superior Capsular Reconstruction with Hamstring Allograft for Irreparable Posterosuperior Rotator Cuff Tears: A Dynamic Biomechanical Evaluation.

BACKGROUND Superior capsular reconstruction (SCR) treatment of massive, symptomatic, irreparable rotator cuff tears (RCT) has become a more recently utilized procedure. However, there is a lack of consensus surrounding optimal graft choice for the SCR technique and current dermal grafts have increased cost and are technically challenging due to a need for multiple implants. The purpose of this study was to biomechanically investigate a biological lower-cost alternative as a support for the superior capsule reconstruction concept; an isolated semitendinosus tendon allograft (STT) and a combination graft with the tendon of the long head of the biceps (LHBT) in an established massive posterosuperior RCT cadaver model. METHODS Ten fresh-frozen cadaveric shoulders (53.3 ± 12.4 years: range: 26 - 65) were tested on an established dynamic shoulder simulator using dynamic muscle loading. Cumulative deltoid forces, maximum abduction angle, and superior humeral head translation were compared across four testing conditions: (1) intact state, (2) massively retracted (Patte III), irreparable posterosuperior RCT, (3) SCR repair using a STT allograft, (4) SCR repair using a combined STT-LHBT repair. RESULTS Intact shoulders required a mean deltoid force of 154.2 ± 20.41N to achieve maximum glenohumeral abduction (55.3 ± 2.3°). Compared to native shoulders, maximum abduction angle decreased following a massively retracted posterosuperior RCT by 52% (28.3 ± 8.4°; p 0.05). The STT-LHBT repair significantly improved range of motion compared to the tear state (P = .04). CONCLUSIONS In a dynamic shoulder simulator model, both the SST and the SST-LHBT repair techniques improved glenohumeral joint kinematics in an amount similar to previously reported "traditional" SCR techniques for treatment of an irreparable posterosuperior RCT.