Biomechanical analysis of the effect of varying suture pitch in tendon graft fixation

The purpose of this study was to biomechanically assess the effect of varyi ng suture pitch on the holding power of the Krackow suture technique for te ndon graft fixation. Seven pairs of rabbit Achilles tendons were sutured wi th single No. 5 Ti-Cron suture using the Krackow technique. One tendon from each pair was sutured using a 0.5-cm suture pitch (half-pitch group) while the contralateral tendon from each pair was sutured with a 1.0-cm suture p itch (one-pitch group). The tendons were loaded to failure using a servohyd raulic materials test system at a loading rate of 0.5 mm/sec. There were no statistically significant differences noted in suture slippage at failure (1.58 cm for half pitch versus 1.45 cm for one pitch) or maximal force to f ailure (158.5 N for half pitch versus 168.2 N one pitch) between the two tr eatment groups. However, the construct with the 1-cm suture pitch was signi ficantly stiffer than the construct with the 0.5-cm suture pitch, with stif fness values of 106.2 N/cm and 91.4 N/cm, respectively. The most common mec hanism of failure was slippage of the suture at the first suture throw and tearing of the first knot through the most distal portion of the tendon. Fo ur constructs failed by suture rupture, two from each experimental group.