Effect of suture knots on tensile strength of repaired canine flexor tendons

59 dog cadaver flexor digitorum profundus tendons were repaired with one or two knots inside or outside the tendon, using two, four and six suture strands. The ultimate tensile strength and gap strengths were compared. Locating the knots outside rather than within the tendon repair site showed significantly higher ultimate tensile strength for two, four, and six strand sutures. The strength was greater in one knot than in two knot sutures; the value of the six-strand suture using the one knot outside technique was the greatest. Similarly, increased gap strength was also obtained from the one-knot-outside technique. We concluded that the knots should be located away from the tendon repair site and there should be as few as possible.