Torque-velocity Relationship Differences During Isokinetic Extension Between Acl Reconstructed And Acl Revision Knees

PURPOSE: The torque-velocity relationship inherent to skeletal muscle may be an important indicator of normal muscle function. Current data indicates this relationship is altered in those recovering from primary ACL reconstruction (ACLR) compared to healthy controls, however we do not know if patients with revision ACLR have worse outcomes due to repeated injury and surgery. The purpose of this study was to characterize the torque-velocity relationship in the quadriceps and hamstrings of patients following ACLR and ACL revision surgery. METHODS: A total of 283 participants included 205 patients with primary unilateral ACLR (22.4 ± 8.7 yr, 98 M, 172.4 ± 10.0 cm, 75.5 ± 18.0 kg, 7.2 ± 0.8 months post-surgery) and 78 participants following ACL revision surgery (22.9 ± 8.7 yr, 34 M, 173.1 ± 9.5 cm, 76.1 ± 16.4 kg, 7.2 ± 0.9 months post-surgery). Participants completed 8 repetitions of isokinetic knee extension and flexion at 90°/s and 180°/s. Normalized peak torque (Nm/kg) was recorded for each movement bilaterally at each velocity. The torque-velocity relationship was operationally defined as the difference in normalized peak torque at 90°/s and 180°/s. A 2x2 (Limb-by-Group) ANOVA was used to compare the torque-velocity relationships. Post-hoc tests were performed as indicated. Alpha level was set at α ≤0.05. RESULTS: The torque-velocity relationships were similar across groups (p = 0.52), but not across limbs (p < 0.001, Table 1). The effect size across limbs were large for the quadriceps of the ACLR participants (d = 1.15) and medium for the Revision groups (d = 0.64). All other effect sizes ranged from 0.07-0.21. CONCLUSION: Participants following ACL revision exhibited significantly decreased torque-velocity relationships in the quadriceps of the surgical limbs compared to their non-injured limbs. This matches previous data from our laboratory in participants following primary ACLR and indicates similar muscular function following the additional surgical procedure. - Table 1. Torque Velocity Relationships by Limb and Group Primary ACLR Revision ACLR Surgical Limb Non-surgical Limb Surgical Limb Non-surgical Limb Quadriceps Torque Velocity Relationship (Nm/kg) 0.32 ± 0.19**, 2 0.55 ± 0.21**, 2 0.36 ± 0.30**, 2 0.54 ± 0.26**, 2 Hamstrings Torque Velocity Relationship (Nm/kg) 0.21 ± 0.14**, 1 0.24 ± 0.14**, 1 0.23 ± 0.17 0.22 ± 0.13 * Significantly different (p ≤ 0.05) than the corresponding limb (surgical or non-surgical) of the revision group** Significantly different (p ≤ 0.05) than the opposite limb within the same group (primary or revision)1 2 corresponding p-value 1 = 0.001, 2 < 0.001