RESUMO
BACKGROUND: The effects of different autograft types for anterior cruciate ligament reconstruction (ACL-R) on muscle function are sparsely investigated in randomized controlled trials. Our aim was to investigate the effects of quadriceps tendon autograft (QTB) vs. semitendinosus-gracilis autograft (StG) on thigh muscle strength and functional capacity, and a patient-reported outcome 1 year after ACL-R, and to compare the results to healthy controls. METHODS: ACL-R patients (n = 100) and matched controls (CON, n = 50) were recruited, with patients being randomly assigned to QTB (n = 50) or StG (n = 50) ACL-R. One year after ACL-R, bilateral knee extensor (KE) and flexor (KF) muscle strength (isometric, dynamic, explosive, limb symmetry index [LSI], hamstring:quadriceps ratio [HQ ratio]) were assessed by isokinetic dynamometry, along with functional capacity (single leg hop distance [SHD]) and a patient-reported outcome (International Knee Documentation Committee [IKDC] score). RESULTS: KE muscle strength of the operated leg was lower (9-11%) in QTB vs. StG as was KE LSI, while KF muscle strength was lower (12-17%) in StG vs. QTB as was KF LSI. HQ ratios were lower in StG vs. QTB. Compared with the controls, KE and KF muscle strength were lower in StG (10-22%), while KE muscle strength only was lower in QTB (16-25%). Muscle strength in the StG, QTB, and CON groups was identical in the non-operated leg. While SHD and IKDC did not differ between StG and QTB, SHD in both StG and QTB was lower than CON. The IKDC scores improved significantly 1 year following ACL-R for both graft types. CONCLUSION: One year after ACL-R, muscle strength is affected by autograft type, with StG leading to impairments of KE and KF muscle strength, while QTB results in more pronounced impairments of KE only. Functional capacity and patient-reported outcome were unaffected by autograft type, with the former showing impairment compared to healthy controls. CLINICAL TRIALS REGISTRATION NUMBER: NCT02173483.