Effect of suture knot location on tensile strength after flexor tendon repair

This study investigated the effect of increased suture material within the flexor tendon repair site on tensile strength in a canine model after in vivo healing. Four-strand modified Savage suture repairs with the knots located either inside or outside the repair site were performed in dogs. The tendons were placed on a passive-motion protocol after surgery and were biomechanically tested at 1, 3, and 6 weeks of in vivo healing. The knots-outside technique initially was 1.14 kg stronger on load-to-failure testing. After 6 weeks of healing, the knots-inside tendons had equal tensile strength (3.91 +/- 0.50 kg [inside] vs 4.16 +/- 0.66 kg [outside]). Relative tensile strength compared to initial strength showed an increase of 20% for the knots-outside technique and an increase of 67% for the knots-inside technique after 6 weeks. Suture material within the repair site did not have any deleterious effects on tensile strength and may stimulate tendon healing.