Assessment of Electromyographic Activity in the Quadriceps and Hamstrings of the Operated Limb Versus the Unaffected Limb in Patients Who Have Undergone ACL Surgery, With and Without Post-operative AMI - an Exploratory Study

Overview

Traumatic injuries to the knee joint, such as an anterior cruciate ligament tear, can compromise the ability of the muscle at the front of your thigh-known as the quadriceps-to contract voluntarily, despite the anatomical integrity of the nerve and muscle structures responsible for contraction. This phenomenon, commonly known as 'arthrogenic motor inhibition' (AMI), is a major limiting factor for recovery and rehabilitation following an anterior cruciate ligament tear, as well as a potential cause of functional disability if left undiagnosed and untreated. Indeed, motor inhibition that persists during the early months of rehabilitation could lead to under-activation of the quadriceps and over-activation of the hamstrings (the muscles at the back of your thigh). It is of interest to assess, during the rehabilitation phase, the contraction capacity of the various quadriceps and hamstring muscles in the operated limb compared with the unaffected limb in patients who have undergone anterior cruciate ligament surgery and who experience post-operative motor inhibition, and in patients who have undergone anterior cruciate ligament surgery but do not experience post-operative motor inhibition. This is why this study has been initiated.

An ACL tear and reconstruction can lead to a neurophysiological dysfunction commonly known as 'arthrogenic muscle inhibition' (AMI). This phenomenon impairs the ability to voluntarily activate the quadriceps, despite the anatomical integrity of the nerve and muscle structures responsible for contraction. AMI is responsible for the quadriceps deficits observed following an ACL rupture and thus appears to be a major limiting factor in the patient's rehabilitation and functional recovery. Consequently, its diagnosis and treatment are imperative. The diagnosis of AMI (post-rupture and post-operative) is based on a classification system that categorises AMI diagnoses according to the identification of a deficit in activation of the vastus medialis (VM) alone (grade 1) or in combination with an extension deficit due to a grade 2 hamstring contracture (grade 2) (Sonnery-Cottet et al, 2022). During the clinical examination, normal VM contraction (during relaxation) can be achieved without the recruitment of all motor units (minimal VM activation), and full knee extension (i.e. without reflex contraction of the hamstrings) can be restored without a return to adequate hamstring activation for the required task. Deficits in activation (inadequate activation) of the quadriceps and over-activation of the hamstrings (Hamstrings) during movements involving greater forces could be the consequences of an AMI still present in the early months of rehabilitation. This AMI could then disrupt the electromyographic (EMG) activation patterns of the quadriceps and hamstrings and contribute to long-term quadriceps deficits. In this context, it is of interest to assess, during the rehabilitation phase, the EMG activity of the different muscle heads of the quadriceps and hamstrings in the operated limb versus the healthy limb in patients who have undergone ACL surgery and experienced post-operative IMA, and in patients who have undergone ACL surgery without post-operative IMA. No studies have been published on this topic. This is why this research has been initiated.