A novel method to determine suture anchor loading after rotator cuff repair--a study of two double-row techniques.

Background: The addition of a lateral suture anchor fixation row to rotator cuff repairs has been shown to improve initial cuff reattachment strength and footprint area. This study evaluated the mechanical function of this lateral row by measuring suture tensions at the individual anchor sites.

Materials And Methods: Eight cadaveric shoulders underwent simulated rotator cuff repairs, using either double row or suture-bridge repair techniques. Suture tensions at each anchor were measured for several static, simulated shoulder positions relevant to postoperative patient management by specially designed instrumented anchors.

Results: Significantly greater suture tensions were measured at the medial anchor sites than at the lateral sites for the double-row (p < 0.001), as well as the suture-bridge constructs (p < 0.016). In the double-row technique, the lateral row sustained 21% (range, 6 to 31) of the total anchor load; whereas, in the suture-bridge technique, the lateral row sustained 33% (range, 8 to 42). Shoulder abduction from 45 degrees to 60 degrees had little effect on anchor tensions; 20 degrees internal and external rotation significantly (p = 0.032) increased loads on the anterior and posterior anchors.

Conclusions: Forces are transmitted through the entire body of the tendon at its humeral fixation, loading the lateral anchors, as well as the medial row, for the two fixation techniques studied. These findings explain the higher laboratory-obtained fixation strengths of double-row techniques. The magnitude and distribution of anchor suture tensions could have important implications for postoperative positioning and activity.