The Torque Velocity Relationship And Second ACL Injury Risk

PURPOSE: Anterior cruciate ligament (ACL) injury results in an elevated risk of reinjury despite surgical reconstruction (ACLR). According to the torque-velocity relationship, muscle contraction velocity and torque production should be inversely related. The purpose of this study was to determine if the torque-velocity relationship could predict reinjury in ACLR patients. METHODS: Primary unilateral ACLR patients (N = 579[50% female]) who were on average 23.5 ± 10.3 years of age, 1.73 ± 0.10 m tall, weighed 75.8 ± 17.8 kg, and were evaluated 6.9 ± 2.0 months post-ACLR) participated in this study. Patients completed isokinetic knee extension at 90°/s and 180°/s, bilaterally. The difference in maximum peak torque (normalized to body mass, Nm/kg) at each velocity was used to calculate the torque-velocity relationship. Any subsequent ipsilateral or contralateral ACL tear was classified as a reinjury. ACL reinjury outcomes were determined following surgery via follow-up phone calls and medical record reviews at least two years post-surgery. Binomial logistic regression models including the quadriceps torque-velocity relationship and age as predictors were performed to model ACL reinjury risk. Model predictive value was determined via area under the curve (AUC) with α = 0.05. RESULTS: Approximately 14.0% (81/579) of patients suffered an ACL reinjury. Male and female patients had similar (p = 0.97) reinjury rates 14.0% and 13.9%, respectively. Reinjury rates were also similar by graft type (p = 0.82). A one Nm/kg increase in the quadriceps torque-velocity relationship was associated with over 2.5x greater odds of sustaining an ACL reinjury (Odds Ratio: 3.51 [95% CI:1.03-12.00], p = 0.05). A one-year increase in age was associated with a 6% decrease in reinjury risk in both models (Odds Ratio: 0.94 [95% CI: 0.91-0.98], p < 0.01). CONCLUSION: The quadriceps torque-velocity relationship was predictive of subsequent ACL injury following ACLR. Similar to previous findings, stronger and younger patients were more likely to experience reinjury. Increased strength may have influenced return to sport decision making and led to increased exposure to risk. Clinicians should consider the interaction of additional modifiable risk factors with the torque-velocity relationship to enhance models of reinjury prediction. Supported by: The first author of this project received funding from the Virginia Athletic Trainers' Association, the Raven Society, and the UVA School of Education and Human Development.