Biomechanical Comparison of Quadriceps and 6-Strand Hamstring Tendon Grafts in Anterior Cruciate Ligament Reconstruction

BACKGROUND: The quadriceps tendon is becoming a popular graft option for anterior cruciate ligament (ACL) reconstruction. Few studies have examined the biomechanics of the quadriceps tendon compared with more commonly used graft choices. Due to the risk associated with small-diameter hamstring tendon grafts, various modifications of hamstring tendon preparation techniques have been described—specifically, a tripled, 6-strand hamstring tendon construct. This is the first study to directly compare the biomechanical properties of quadriceps tendon and hamstring tendon grafts. PURPOSE/HYPOTHESIS: The purpose of this study was to quantify the biomechanical properties of the quadriceps tendon and 6-strand hamstring tendon grafts, specifically evaluating ultimate load to failure, load at 3 mm of displacement, and stiffness. These parameters characterize the time zero, in vitro, static tensile properties of these graft options. Our hypothesis was that for grafts of similar size, there would not be a significant difference in the biomechanical properties. STUDY DESIGN: Controlled laboratory study. METHODS: Quadriceps and hamstring tendon grafts were harvested from 6 human cadaveric knees (mean age, 61.17 ± 10.38 years). These matched grafts were prepared and biomechanically tested using an all-electric dynamic test load system. The mean diameter, stiffness, ultimate load to failure, and load to 3 mm of displacement were evaluated and analyzed. RESULTS: The mean diameters of the 6-strand hamstring and quadriceps tendons were 11.33 and 10.16 mm, respectively (P = .03). Despite these significantly different diameters, no differences were found in graft ultimate load to failure or load at 3 mm of displacement. The 6-strand hamstring tendon graft was significantly stiffer compared with the quadriceps tendon (1147.65 vs 808.65 N/mm; P = .04). CONCLUSION: The 6-strand hamstring tendon and quadriceps tendon graft had similar biomechanical properties with respect to ultimate load to failure and load at 3 mm of displacement in 6 matched cadaveric specimens. Both grafts were significantly stiffer than the native ACL, and the hamstring tendon construct was significantly stiffer than the quadriceps tendon. CLINICAL RELEVANCE: The quadriceps tendon graft is a reliable alternative to a 6-strand hamstring tendon graft for ACL reconstruction.