Can we use the ipsilateral Hamstrings for ACL Reconstruction in case of medial collateral ligament insufficiency?

AIMS AND OBJECTIVES: Semitendinosus and gracilis muscles (hamstring muscles) are frequently harvested autologous tendon grafts of the knee e.g. for cruciate ligament reconstruction. This study investigated the joint-stabilizing effects of these muscles in case of insufficiency of the medial collateral ligament (MCL). Hypotheses: First, both the semitendinosus and the gracilis muscles can actively stabilize the joint against valgus stress in the medial collateral unstable knee. Second, this stabilizing influence of these muscles decreases with increasing flexion angle METERIALS AND METHODS: Kinematics were examined in ten fresh-frozen human cadaveric knees using a robotic/UFS testing system and an optical tracking system. The knee kinematics under 5 Nm and 10 Nm valgus stress were determined in the a) MCL intact and b) MCL deficient knee in different flexion angles, respectively using the following simulated muscle loads: 1) 0 N (Idle), 2) 200 N semitendinosus load (ST) and 3) 280 N combined semitendinosus and gracilis load (STGT). RESULTS: Cutting the MCL increased valgus angle under all tested conditions and angles in contrast to the MCL intact knee by 4.3-8.1 degrees for 5 Nm, 6.5-11.9 degrees for 10 Nm valgus torque; P<.01; RM-ANOVA). Applied 200 N simulated ST load reduced the valgus angle significantly in 0°, 10°, 20° and 30° of flexion under 5 Nm and 10 Nm (P< .05) valgus stress. In 0°, 10° and 20° these values were close to the MCL intact joint under the respective torque (both P >.05). The combined 280 N simulated STGT load reduced significantly valgus angle in 0°, 10° and 20° of flexion under 5 Nm and 10 Nm of valgus stress (P< .05) to values near the intact joint (5 Nm: 0°, 10°; 10 Nm: 0°, 10°, 20° - P >.05). In 60° and 90° of flexion ST and STGT loads could not decrease resulting valgus angle of the MCL deficient knee (without hamstring load; P>.05 or valgus increase P<.05). CONCLUSION: In this human cadaveric study semitendinosus and gracilis muscles can successfully stabilize against valgus stress in the MCL insufficient knee in near-to-extension flexion angles. In the valgus-unstable knee, hamstring muscles should be preserved in (multi-) ligament surgery, but also in joint arthroplasty and osteosynthesis if possible.