Factors affecting quadriceps strength recovery after anterior cruciate ligament reconstruction with hamstring autografts in athletes

Patients typically return to sports activities 6-12 months after anterior cruciate ligament (ACL) reconstruction, and quadriceps strength has been used as one of the criteria to return to sports activities. The purpose of this study is to identify the factors that affect quadriceps strength recovery after ACL reconstruction with a hamstring tendon autograft 6 months after surgery. Isokinetic quadriceps strength at 60A degrees/s was measured preoperatively and 6 months after surgery in 193 athletes who underwent ACL reconstruction with a hamstring tendon autograft. The quadriceps strength index was calculated by normalizing the peak torque of the involved leg with the uninvolved leg. The subjects were divided into two groups according to the quadriceps strength index 6 months after surgery: at least 85 % (n = 84) or less than 85 % (n = 109). Multivariate logistic regression analysis and a receiver operating curve analysis were performed. The preoperative quadriceps strength index [odds ratio (OR) 1.02; 95 % confidence interval (CI) 1.01-1.03], age (OR 0.92; 95 % CI 0.86-0.98), sex (OR 2.45; 95 % CI 1.19-5.18), and knee pain (OR 0.17; 95 % CI 0.04-0.52) were independently associated with quadriceps strength recovery. The cut-off value of the preoperative quadriceps strength index was 70.2 % to obtain at least 85 % quadriceps strength index 6 months after surgery. To achieve sufficient quadriceps strength recovery at the timing of return to sports activities following ACL reconstruction using a hamstring tendon autograft, preoperative quadriceps strength, age, sex, and knee pain should be considered. III.