Optimizing biomechanical performance of the 4-strand cruciate flexor tendon repair

The purpose of this study was to determine whether increasing the size of the locking loop increased the repair strength of the cruciate 4-strand suture technique and to quantify the biomechanical properties that various peripheral suture techniques provide in the cruciate 4-strand suture technique.

Fifty-six deep flexor tendons harvested from adult sheep hind limbs were divided randomly into 7 groups of 8. Four groups were repaired using the cruciate core technique without a peripheral suture. The locking loops were set using 10%, 25%, 33%, or 50% of the tendon width and loaded to failure using a distraction rate of 20 mm/min. The 3 groups of tendons then were repaired by using the established optimal locking loop size. These 3 groups were combined with a simple running, cross-stitch, or the interlocking horizontal mattress (IHM) peripheral suture. Repairs were tested to failure and the load at a 2-mm gap, load at failure, and stiffness were determined for all samples.

Repairs with locking loops of 25% had the greatest biomechanical properties with load to 2-mm gap formation, load to failure, and stiffness of 10 N, 46.3 N, and 3.9 N/mm, respectively. Those with 33%, 50%, and 10% locking loops followed. Repairs with 10% locking loops failed owing to the suture cut out of the tendon. All other groups failed because of suture breakage. By using the cruciate core technique with a 25% locking loop the IHM/cruciate combination was markedly better than both the cross-stitch/cruciate and simple running/cruciate combinations.

The ideal-sized bite of the locking loops for the cruciate repair is 25% of the tendon's width. Peripheral sutures are vital to the biomechanical properties of the repair. The IHM peripheral suture technique provided the greatest improvement in biomechanical properties.