Greater eccentric hamstrings to concentric quadriceps strength ratio at 6 months after anterior cruciate ligament reconstruction is associated with reduced odds of revision within 2 years

Purpose To investigate the association between eccentric hamstrings‐to‐concentric quadriceps strength ratio (mixed hamstrings to quadriceps [HQ]‐strength ratio) at 6 months postoperatively and revision anterior cruciate ligament reconstruction (ACL‐R) within 2 years of primary surgery. The secondary purpose was to investigate the association between the mixed HQ‐strength ratio and single‐leg hop for distance limb symmetry index (LSI). Methods Data were collected from a local registry at Capio Artro Clinic, Stockholm, Sweden. Patients aged ≥15 years, without concomitant ligament injuries and meniscal resection or repair who underwent primary ACL‐R with hamstring tendon autografts between 2005 and 2021 were included. Isokinetic eccentric hamstrings and concentric quadriceps strength were assessed using a Biodex dynamometer 6 months postoperatively. Associations between mixed HQ‐strength ratio on the ACL‐R leg and revision ACL‐R were analysed using multivariable logistic regression analysis, presented with odds ratios (ORs), 95% confidence intervals (CIs) and area under the receiver operating characteristics curve (AUC). Associations between mixed HQ‐strength ratio and single‐leg hop for distance LSI were analysed with linear regression. Results Of the 3458 patients included, 49.5% were female and the mean age was 28.8 ± 10.4 years. Patients who underwent revision ACL‐R within 2 years had lower mixed HQ‐strength ratio on the ACL‐R leg 6 months postoperatively. After adjustment for age at primary ACL‐R and preinjury Tegner level, each 10‐unit increase in the mixed HQ‐strength ratio on the ACL‐R leg was associated with lower odds of revision ACL‐R (OR = 0.81, 95% CI [0.71;0.93], p = 0.003). However, the discriminatory ability was poor (AUC = 0.64). A greater mixed HQ‐strength ratio was associated with poorer single‐leg hop for distance LSI, adjusted for age at primary ACL‐R and preinjury Tegner level ( β = −1.30, 95% CI [−1.51;−1.09], p < 0.001). Conclusion The mixed HQ‐strength ratio may complement the evaluation of muscle strength recovery after ACL‐R. However, its poor discriminatory ability limits its use to identify patients who will undergo revision ACL‐R. Level of Evidence Level III.