Neuronal and neuromuscular changes after ACL reconstruction - a systematic review

Background: Knowledge of the neuromuscular consequences of an ACL injury is important because a deeper understanding of these consequences can influence the rehabilitation of patients after an ACL reconstruction. Therefore, the aim of this thesis was to conduct a systematic review about neuronal and neuromuscular changes after ACL-reconstruction.
Methods: We conducted a systematic literature search using selected search terms related to the neuronal and neuromuscular changes after ACL reconstruction. The search was in line with the PRISMA and PICOS recommendations.
Results: A total of 38 studies were eligible for analysis. ACLR-patients showed altered gamma loop function in the involved and not-involved leg, a decrease of quadriceps strength and quadriceps voluntary activation and a lower spinal reflex excitability shortly after reconstruction with a linear increase over time. There was no difference in corticospinal excitability between ACLR-patients and controls shortly after reconstruction; it did increase in ACLR-patients over time, though. Additionally, there was higher activation in the frontal lobe of ACLR-patients.
Conclusions: Quadriceps strength and voluntary activation are highly depending on different factors like spinal reflex and corticospinal excitability, even though an exact correlation needs to be further investigated. Furthermore, gamma loop function is firstly affected by the injury and then further induced by the ACL-reconstruction. Additionally, multiple studies reported an increased activity in the frontal lobe, which is responsible for higher neurocognitive attention and motor planning. Therefore, even if ACLR-patients are able to reproduce tasks similarly or equally compared to healthy controls, there can be reported several neuronal and neuromuscular changes.