Effects of braiding on tensile properties of four-strand human hamstring tendon grafts.

BACKGROUND Anterior cruciate ligament reconstruction is commonly performed with autogenous hamstring tendon grafts. PURPOSE To ascertain the effects of braiding on ultimate tensile strength and stiffness of hamstring tendon graft. STUDY DESIGN Controlled laboratory study. METHODS Sixteen fresh-frozen semitendinosus and gracilis tendons were harvested from eight matched (right and left) human cadaveric specimens. Both sets of hamstring tendons from each matched pair were doubled, creating a four-strand graft. Grafts were then randomized so that one graft from each matched pair was braided and the other remained unbraided. The diameter of each graft construct was recorded. Grafts were tested to failure on a materials testing machine. RESULTS There were no significant differences in cross-sectional area before or after braiding. Fifteen of 16 tendons failed midsubstance; 1 failed at the lower clamp. Braiding reduced the initial tensile strength and stiffness of human hamstring tendon grafts in this study by 35.0% and 45.8%, respectively. CONCLUSIONS Braiding may place the collagen fibers in a suboptimal orientation for loading that results in a weaker graft. We do not recommend the use of braiding if the strongest, stiffest initial graft is desired.