Bilateral neuromuscular control one year after anterior cruciate ligament reconstruction or conservative treatment

Background and research question: Neuromuscular alterations are present in patients after anterior cruciate ligament (ACL) rupture or reconstruction, even in the long run. ACL rupture seems to affect neuromuscular control of the involved, injured leg but also of the non-involved limb. Therefore, this study wants to address the current research gap by looking at differences in objectively measured neuromuscular control one year after ACL reconstruction (ACL-R) or conservative treatment (ACL-C) in both the injured and non-involved leg, compared to healthy controls with an intact ACL (ACL-I).
Methods: During this cross-sectional study, surface electromyography of vastus medialis (VM) and lateralis (VL), biceps femoris (BF) and semitendinosus (ST) was recorded bilaterally in ACL-R (N = 38), ACL-C (N = 26), and ACL-I (N = 38) participants during stair descent and artificially induced anterior tibia translation. Each step of stair descent was divided into pre-activity, weight-acceptance and push-off phase. Pre-activation, short, medium, and long latency responses were defined as phases for reflex activity. For each muscle of both legs and all phases, normalized root mean squares were calculated (α = 0.05).
Results: During stair descent, significant lower BF activity was present in the involved limb of ACL-R and ACL-C compared to the matched leg of ACL-I during push-off. Lower quadriceps activity was found in the involved compared to the non-involved side of ACL-R in all phases, and similar in BF of ACL-C during weight-acceptance. Comparing the non-involved leg of ACL-R to the matched leg of ACL-I, quadriceps activity was higher during all phases, hamstrings activation lower during pre-activity and BF activity lower during push-off. Comparing the non-involved leg of ACL-C to the matched leg of ACL-I, higher VL pre-activity and lower BF pre-activity, and higher quadriceps activity during push-off was found. Higher VM pre-activity of the non-involved leg was found in ACL-R compared to ACL-C. For reflex activity, the following muscles and phases differed significantly in the involved (matched) leg between groups: higher pre-activation of VM comparing ACL-R and ACL-C, lower pre-activation of VM between ACL-C and ACL-I, as well as lower BF pre-activation and ST activity during medium latency response for each patient group compared to ACL-I. Concerning long latency response, significant higher VM activity was found in the involved leg comparing ACL-R to ACL-C and to ACL-I.
Conclusion: One year after an ACL rupture, neuromuscular alterations are still present in both legs of ACL patients, regardless of treatment option. Current rehabilitation protocols may not be able to restore neuromuscular control in either leg. Future research should include standardized rehabilitation programs with cross-education and neuromuscular exercises to restore bilateral, normal function.