The resistance of a four- and eight-strand suture technique to gap formation during tensile testing: an experimental study of repaired canine flexor tendons after 10 days of in vivo healing.

There is a high incidence of gap formation at the repair site following tendon repair. Our goal was to determine the resistance of a 4- and an 8-strand suture technique to gap formation during tensile testing. We hypothesized that the 8-strand repair would sustain higher force levels at the onset of 1- and 3-mm gaps than the 4- strand repair. Twenty-two canine flexor tendons were transected, repaired, and tested to failure after 10 days of in vivo healing. Tests were recorded using a 60-Hz video system that allowed frame-by-frame playback for assessment of gap formation. The 8-strand repairs sustained 80% higher force at a gap of 1 mm than the 4-strand repairs (average force, 70 vs 39 N), but the force sustained at a gap of 3 mm did not differ between groups (35 N for both groups). For both repair types, a 1-mm gap typically occurred near the point of ultimate (maximum) force while a 3-mm gap occurred after the ultimate force. We conclude that the 8-strand repair is significantly more resistant to initial gapping during ex vivo tensile testing than the 4-strand repair but that the two repairs are equally susceptible to rupture if a gap of 3 mm or greater forms.