Comparison of hamstring and quadriceps strength after anatomical versus non-anatomical anterior cruciate ligament reconstruction: a retrospective cohort study

BACKGROUND: Strength recovery of injured knee is an important parameter for patients who want to return to sport after anterior cruciate ligament reconstruction (ACLR). Comparison of muscle strength between anatomical and non-anatomical ACLR has not been reported. PURPOSE: To evaluate the difference between anatomical and non-anatomical single-bundle ACLR in hamstring and quadriceps strength and clinical outcomes. METHODS: Patients received unilateral primary single-bundle hamstring ACLR between January 2017 to January 2018 were recruited in this study. Patients were divided into anatomical reconstruction group (AR group) and non-anatomical reconstruction group (NAR group) according to femoral tunnel aperture position. The hamstring and quadriceps isokinetic strength including peak extension torque, peak flexion torque and H/Q ratio were measured at an angular velocity of 180°/s and 60°/s using an isokinetic dynamometer. The isometric extension and flexion torques were also measured. Hamstring and quadriceps strength were measured preoperatively and at 3, 6, and 12 months after surgery. Knee stability including Lachman test, pivot-shift test, and KT-1000 measurement and subjective knee function including International Knee Documentation Committee (IKDC) and Lysholm scores were evaluated during the follow-up. RESULTS: Seventy-two patients with an average follow-up of 30.4 months (range, 24–35 months) were included in this study. Thirty-three were in AR group and 39 in NAR group. The peak knee flexion torque was significant higher in AR group at 180°/s and 60°/s (P < 0.05 for both velocity) at 6 months postoperatively and showed no difference between the two groups at 12 months postoperatively. The isometric knee extension torque was significant higher in AR group at 6 months postoperatively (P < 0.05) and showed no difference between the two groups at 12 months postoperatively. No significant differences between AR group and NAR group were found regarding knee stability and subjective knee function evaluations at follow-up. CONCLUSIONS: Compared with non-anatomical ACLR, anatomical ACLR showed a better recovery of hamstring and quadriceps strength at 6 months postoperatively. However, the discrepancy on hamstring and quadriceps strength between the two groups vanished at 1 year postoperatively.