Effect of shoulder abduction angle on biomechanical properties of the repaired rotator cuff tendons with 3 types of double-row technique.

Background: After rotator cuff repair, the shoulder is immobilized in various abduction positions. However, there is no consensus on the proper abduction angle. Purpose: To assess the effect of shoulder abduction angle on the biomechanical properties of the repaired rotator cuff tendons among 3 types of double-row techniques. Study Design: Controlled laboratory study. Methods: Thirty-two fresh-frozen porcine shoulders were used. A simulated rotator cuff tear was repaired by 1 of 3 double-row techniques: conventional double-row repair, transosseous-equivalent repair, and a combination of conventional double-row and bridging sutures (compression double-row repair). Each specimen underwent cyclic testing followed by tensile testing to failure at a simulated shoulder abduction angle of 0 degrees or 40 degrees on a material testing machine. Gap formation and failure loads were measured. Results: Gap formation in conventional double-row repair at 0 degrees (1.2 +/- 0.5 mm) was significantly greater than that at 40 degrees (0.5 +/- 0.3 mm, P = .01). The yield and ultimate failure loads for conventional double-row repair at 40 degrees were significantly larger than those at 0 degrees (P < .01), whereas those for transosseous-equivalent repair (P < .01) and compression double-row repair (P < .0001) at 0 degrees were significantly larger than those at 40 degrees. The failure load for compression double-row repair was the greatest among the 3 double-row techniques at both 0 degrees and 40 degrees of abduction. Conclusion: Bridging sutures have a greater effect on the biomechanical properties of the repaired rotator cuff tendon at a low abduction angle, and the conventional double-row technique has a greater effect at a high abduction angle. Clinical Relevance: Proper abduction position after rotator cuff repair differs between conventional double-row repair and transosseous-equivalent repair. The authors recommend the use of the combined technique of conventional double-row and bridging sutures to obtain better biomechanical properties at both low and high abduction angles.