Suture anchor loading after rotator cuff repair: effects of an additional lateral row.

ABSTRACT

HYPOTHESIS: Our initial hypothesis was that the medial row of double-row rotator cuff repair techniques would bear most of the load on the repaired cuff. MATERIALS AND METHODS: Six cadaver shoulders underwent simulated rotator cuff repairs using sequential single row, double-row, and suture-bridge repair techniques. Suture tensions at each anchor were measured for several static, simulated shoulder positions by specially designed, instrumented anchors. RESULTS: Significantly greater suture tensions were measured in the anchors in a single row repair construct than either the double row repair or suture bridge repair construct (P < .001). In the double-row and suture bridge techniques, there was no apparent difference in the loads born by the medial and lateral row anchors. Shoulder abduction from 45 degrees to 60 degrees had little effect on anchor tensions; 45 degrees internal and external rotation significantly (P = .032) increased loads on the anterior and posterior anchors by at least 125%. DISCUSSION: Forces are transmitted through the entire portion of the tendon at its humeral fixation, loading the lateral anchors as well as the medial row for the techniques studied. This "load sharing" can explain the higher fixation strengths of double row techniques seen experimentally. CONCLUSION: The magnitude and distribution of anchor suture tensions could have important implications for lateral row fixation devices and post-operative positioning and activity. LEVEL OF EVIDENCE Basic Science.