Comparison of mechanical stability in double-row rotator cuff repairs between a knotless transtendon construct versus the addition of medial knots.

Abstract

Our purpose was to investigate the importance of medial-row knot tying to mechanical stability in a double-row rotator cuff repair by comparing a knotless construct with transtendon anchor passage versus a similar construct implementing medial knots. A standard defect was created in the infraspinatus tendons of 14 bovine humeri. All defects were repaired with 2 medial and 2 lateral anchors (SutureCross System; KFx Medical, Carlsbad, CA). The medial anchors were either placed by transtendon passage in a knotless construct or placed directly into bone with needle passage of suture to create bursal-sided knots medially. Constructs were subjected to a cyclic loading protocol and then loaded to failure. The medially knotted constructs had a statistically higher stiffness at both the initial and final cycles (P < .001 and P < .001, respectively) and a lower displacement during cyclic loading (P < .02). There were strong trends toward decreased gauge displacement (P = .12) and decreased cycles to 3 mm of displacement (P = .07) in the medially knotted group. Maximal yield strength was greater in the medially knotted group (350 +/- 270 N v 650 +/- 530 N), although this was not found to be statistically significant (P = .5). Our data suggest that creation of medial knots increases construct stiffness and stability in arthroscopic double-row cuff repair. This is likely because of increased load transfer to the lateral anchor and suture-tendon interface in the knotless construct. Medial knots create increased mechanical stability that theoretically may improve rotator cuff healing. This mechanical advantage must be weighed against surgical efficiency, with consideration given to factors such as tissue quality.