Gait Mechanics in Women of the ACL-SPORTS Randomized Control Trial: Interlimb Symmetry Improves Over Time Regardless of Treatment Group

Abstract

Women after anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) are more likely than men to exhibit asymmetric movement patterns, which are associated with post-traumatic osteoarthritis. We developed the ACL specialized post-operative return-to-sports (ACL-SPORTS) randomized control trial to test the effect of strength, agility, plyometric, and secondary prevention (SAPP) training with and without perturbation training (SAPP + PERT) on gait mechanics in women after ACLR. We hypothesized that movement symmetry would improve over time across both groups but more so among the SAPP + PERT group. Thirty-nine female athletes 3-9 months after primary ACLR were randomized to SAPP or SAPP + PERT training. Biomechanical testing during overground walking occurred before (Pre-training) and after (Post-training) training and one and 2 years post-operatively. Hip and knee kinematic and kinetic variables were compared using repeated measures analysis of variance with Bonferroni corrections for post hoc comparisons (α = 0.05). There was a time by limb interaction effect (p = 0.028) for peak knee flexion angle (PKFA), the primary outcome which powered the study, characterized by smaller PKFA in the involved compared to uninvolved limbs across treatment groups at Pre-training, Post-training, and 1 year, but not 2 years. Similar findings occurred across sagittal plane knee excursions and kinetics and hip extension excursion at midstance. There were no meaningful interactions involving group. Neither SAPP nor SAPP + PERT training improved walking mechanics, which persisted 1 but not 2 years after ACLR. Statement of clinical significance: Asymmetrical movement patterns persisted long after participants achieved symmetrical strength and functional performance, suggesting more time is needed to recover fully after ACLR. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1743-1753, 2019.

Keywords: ACL-SPORTS training; anterior cruciate ligament reconstruction (ACLR); gait mechanics; musculoskeletal modeling; women.

Figure 1.

The flow chart depicts the enrollment process and testing sessions.

Figure 2.. Peak Knee Flexion Angle

There were no interaction or main effects of group for peak knee flexion angle (PKFA), the primary study outcome. There was an interaction effect of time by limb for PKFA as well as a main effect of limb for PKFA. Clinically meaningful differences were present across both groups at both Pre-training and Post-training, but not at one or two years after ACLR (bar = exceeds MCID). (Note: due to rounding, the interlimb difference in the SAPP+PERT group is 3.1° at pre-training, which exceeds the MCID of 3.0°, whereas the interlimb difference at one year is only 2.9°.)

Figure 3.. Hip Extension Excursion During Weight Acceptance

There was a significant group by limb interaction effect of hip extension excursion during weight acceptance; however, no differences were clinically meaningful. (Brackets indicate the statistically significant difference between the Post-training and 2 year timepoint within the SAPP+PERT group, collapsed across limbs.)

Figure 4.. Hip Internal Extension Moment at PKFA

There was a significant time by group interaction effect (p = .022) for hip internal extension moment at peak knee flexion angle (PKFA), characterized by smaller values at 2 years compared to any earlier timepoints in the SAPP group only (bracket denotes difference).

Figure 5.. Hip Internal Abduction Moment at PKFA

While there were no interaction effects for hip internal abduction moment at peak knee flexion angle (PKFA), there were main effects of group and limb, characterized by larger values in the involved compared to uninvolved limb as well as in the SAPP+PERT versus SAPP group (indicated by large bracket), regardless of time.

Figure 6.. Knee Internal Extension Moment at PKFA

There was an interaction effect of time by limb for knee internal extension moment at peak knee flexion angle (PKFA), characterized by large early interlimb asymmetry that resolved across groups by two years after ACLR. Interlimb differences exceeded MCID values across both groups at Pre- and Post-training, but only in the SAPP+PERT group at one year (bar = exceeds MCID). There was also a main effect of group with higher knee extension moments across time and limb in the SAPP+PERT group compared to the SAPP group (indicated by the large bracket).

Figure 7.. Knee Flexion Excursion During Weight Acceptance

There was an interaction effect of time by limb for knee flexion excursion during weight acceptance, characterized by early interlimb asymmetry that resolved by one year after ACLR. Only the interlimb differences at Pre-training for the SAPP group and at Post-training for the SAPP+PERT group were clinically important (bar = exceeds MCID).

Figure 8.. Knee Extension Excursion During Midstance

There was an interaction effect of time by limb for knee extension excursion during midstance, characterized by early interlimb asymmetry that resolved across groups by two years after ACLR. Interlimb differences exceeded MCID values across both groups at Pre- and Post-training, but only in the SAPP+PERT group at one year (bar = exceeds MCID).

Figure 9.. Hip Extension Excursion During Midstance

There was an interaction effect of time by limb for hip extension excursion during midstance; clinically meaningful differences between limbs occurred across groups at both Pre-training and Post-training, but not at 1 or 2 years (bar = exceeds MCID).

Figure 10.. Peak Medial Compartment Contact Force

There was a time by limb interaction for peak medial compartment contact force. While the difference between limbs at Post-training was statistically significant (p = .026), the difference (− 0.27) did not exceed the meaningful inter-limb difference threshold of 0.4 body weight (BW) at Post-training or any other timepoint.