Isokinetic quadriceps symmetry helps in the decision to return to running after anterior cruciate ligament reconstruction

BackgroundAfter anterior cruciate ligament reconstruction (ACLR), the decision to allow a return to running is empirical, and the post-operative delay is the most-used criterion. The Quadriceps isokinetic-strength Limb Symmetry Index (Quadriceps LSI), with a cutoff of 60%, could be a useful criterion.ObjectiveTo determine the association between a Quadriceps LSI ≥ 60% and return to running after ACLR.MethodsOver a 10-year period, we retrospectively included 470 patients who underwent ACLR. Four months after ACLR, participants performed an isokinetic test; quadriceps concentric peak torque was used to calculate the Quadriceps LSI at 60?/s. With a Quadriceps LSI ≥ 60%, a return to running was suggested. At 6 months after ACLR, participants were clinically evaluated for a return to sport and post-operative middle-term complications. A multivariable predictive model was built to assess the efficiency diagnosis of this cutoff in order to consider cofounding factors. Quadriceps LSI cutoff ≥ 60% was assessed with sensitivity, specificity and the area under the receiver operating characteristic curve (AUC).ResultsAccording to our decision-making process with the 60% Quadriceps LSI cutoff at 60?/s, 285 patients were authorized to return to running at 4 months after ACLR and 185 were not, but 21% (n = 59) and 24% (n = 45), respectively, were not compliant with the recommendation. No iterative autograft rupture or meniscus pathology occurred at 6 months of follow-up. On multivariable logistic regression analysis, a return to running by using the 60% Quadriceps LSI cutoff was associated with undergoing the hamstring strand procedure (odds ratio 2.60, 95% confidence interval CI] 1.75–3.84; P < 0.0001) and the absence of knee complications (1.18, 1.07–1.29; P = 0.001) at 4 months. The sensitivity and specificity of the 60% Quadriceps LSI cutoff were 83% and 70%, respectively. The AUC was 0.840 (95% CI 0.803–0.877).ConclusionsUsing the 60% cutoff of the isokinetic Quadriceps LSI at 4 months after ACLR could help in the decision to allow a return to running.