Knee Extensor Rate of Torque Development After Anterior Cruciate Ligament Reconstruction With Hamstring Tendon Autografts in Young Female Athletes

Background: For the measurement of functional deficits after anterior cruciate ligament reconstruction (ACLR) with bone-patellar-tendon bone (BTB) grafts, the knee extensor rate of torque development (RTD) is known as a relevant outcome. However, it remains unclear if the RTD is also a relevant outcome after ACLR with semitendinosus and gracilis tendon (STG) autografts. The purpose of the present study was to compare the limb symmetry index (LSI) of the RTD of the quadriceps with that of the peak torque after ACLR using STG autografts and to investigate the relationship between the self-reported functional outcome and the LSI of the torque parameters. Methods: Eighteen young female athletes after ACLR with STG grafts (age: 16.8 ± 1.3 years; time after surgery: 8.6 ± 0.8 months). The participants had undergone three maximal voluntary isometric quadriceps tests using an isokinetic dynamometer. Using the torque-time curves, the peak torque, RTD 100 (0 to 100 ms) and RTD 200 (100 to 200 ms) were determined. The International Knee Documentation Committee subjective knee evaluation form (IKDC-SKF) was used to assess self-reported knee function. Comparisons of the LSI of the peak torque and RTD were performed by analysis of variance (ANOVA) with Bonferroni’s correction as a post-hoc test. The Pearson correlation coefficient was used to examine the associations of the IKDC-SKF score with the LSI of the RTD and peak torque. Results: The LSI of the peak torque and RTD 200 was significantly lower than that of the RTD 100 (peak torque vs RTD 100 P = 0.017; RTD 200 vs RTD 100 P = 0.015). The LSI of the peak torque was positively correlated with the IKDC-SKF score ( R = 0.621; P = 0.006). Conclusions: The peak torque and RTD 200 were more sensitive for detecting inter-limb differences in quadriceps function than RTD 100 . The IKDC-SKF score was correlated with the LSI of the quadriceps peak torque but not with that of the RTD. The peak torque of the quadriceps was considered an appropriate screening for functional recovery after ACLR with STG grafts.