Clamping suture knot during tying process may not impact biomechanical properties

Bisson LJ. Knee Surg Sports Traumatol Arthrosc. 2011. doi: 10.1007/s00167-011-1667-x

Temporarily clamping a suture knot during the tying process to keep it from slipping in a tendon-to-tendon or tendon-to-bone knee repair does not impact its biomechanical properties, according to this study from researchers in New York.

The research team tied seven variouis types and sizes of braided nylon or polyblend sutures around an isolated 35 mm glass cylinder with no clamp, a serrated clamp or a smooth needle holder holding a surgeon’s knot after the initial throw. These knots were then secured with four alternating half-hitches with reversed posts. The team then loaded the created loops onto custom hooks in an axial loading frame and load-tested the sutures until failure. Factors measured included elongation, ultimate tensile load, stiffness and mechanism of failure.

“Six of seven suture loops tied with either clamp showed statistically significant, but clinically minimal (<1 mm) increased elongation following cycling,” the authors wrote. Clamp use was found to have no impact on suture loop stiffness in four of the suture types and sizes, though decreased stiffness was noted in three.

Untying was more likely in those suture loops tied with a serrated clamp than it was in those without a clamp, but there was no reported difference in mechanism of failure from those sutures that had been tied with a smooth clamp.

“Surgeons wishing to temporarily clamp a knot to keep it from slipping during the tying process may do this without concern for weakening the suture,” the authors wrote.