Significant Muscle Strength Deficits Persist One Year After ACL Reconstruction with Hamstring Tendon Autografts

Background Hamstring tendon (HT) autografts are frequently used in anterior cruciate ligament (ACL) reconstruction, but their impact on muscle strength recovery and knee functionality remains a concern. Purpose This study aimed to evaluate the changes in muscle strength and recovery dynamics in patients undergoing anterior cruciate ligament (ACL) reconstruction using hamstring tendon autografts. The primary focus was on assessing quadriceps and hamstring strength, hamstring-to-quadriceps (H/Q) ratios, and Limb Symmetry Index (LSI) before and one year post-surgery. Additionally, the study examined clinical outcomes using the International Knee Documentation Committee (IKDC) and Lysholm Knee Scores. Study Design: Prospective cohort study; Level of evidence; 2. Methods Seventeen male patients (mean age 25.1 ± 7.1 years) who underwent ACL reconstruction with hamstring autografts were included. Isokinetic testing assessed muscle strength preoperatively and at 12 months postoperatively. Outcome measures included concentric and eccentric peak torque values for quadriceps and hamstrings, H/Q ratios, LSI, and functional outcomes measured by the International Knee Documentation Committee (IKDC) Score and the Lysholm Knee Score. Statistical analysis compared preoperative and postoperative data. Results Significant preoperative disparities were observed in concentric quadriceps strength between injured and uninjured sides, with persistent deficits postoperatively. Eccentric quadriceps strength showed stability, but hamstring strength significantly decreased post-surgery. Conventional and functional H/Q ratios worsened postoperatively, failing to meet normal benchmarks. LSI for both quadriceps and hamstrings remained below the 90% threshold postoperatively, indicating persistent strength deficits. Despite these muscle imbalances, significant improvements were observed in knee function, with increased IKDC and Lysholm scores. Conclusion One year after ACL reconstruction with hamstring tendon autografts, patients exhibit substantial deficits in quadriceps and hamstring strength, reflected in lowered H/Q ratios and LSI values. Despite these deficits, significant improvements in knee function and stability are observed. Extended and targeted rehabilitation focusing on concentric and eccentric muscle strengthening may be necessary for optimal recovery.