Double-stranded hamstring tendons for anterior cruciate ligament reconstruction

Bone-patellar tendon-bone autograft is the most commonly used tissue for ACL reconstruction; however, the harvesting of patellar tendon as a free graft can lead to significant morbidity. Alternate grafts may lower morbidity, yet the most commonly used alternate grafts including the double-stranded semi-tendinosus or gracilis have not been studied biomechanically. This study investigated the morphometric and biomechanical properties of double-stranded semi-tendinosus and gracilis tendons separately along with the patellar and quadriceps tendons obtained bilaterally from six fresh, 77-year-old cadaveric specimens. The quadriceps tendon was the thickest and therefore had the largest cross-sectional area, whereas double-stranded semitendinosus had the highest mean peak load to failure (1029+/-158.4 N), 11.5% and 10.3% stronger than patellar tendon and quadriceps tendons, respectively. Midsubstance rupture occurred in the hamstring tendons, whereas the patellar and quadriceps tendons failed at the bone-tendon junctions. Semitendinosus tendons with higher cross-sectional area had higher peak loads to failure. This linear relationship between cross-sectional area and the peak load to rupture also was observed in the other tendon groups (except gracilis). These results indicate that despite a lower cross-sectional area of the double-stranded semitendinosus, this tendon demonstrated a comparable mean peak load to rupture and stress compared with patellar and quadriceps tendons. It also was demonstrated that combined double-stranded semitendinosus and gracilis tendons produce a stronger graft with initial strength twice that of the patellar tendon, but requires further testing.