Deficit in Quadriceps Voluntary Activation After Anterior Cruciate Ligament Reconstruction: Roles of the "Learned Non-use" Paradigm and the Interhemispheric Inhibition

Summary

Anterior cruciate ligament (ACL) tear is mainly caused by sport injuries. 40% of injuries are attributed to noncontact mechanisms involving pivoting. Regaining quadriceps strength is a primary focus of patients pursuing a rehabilitation program after ACL reconstruction (ACLR). Unfortunately, despite rehabilitation programs aimed at reversing this muscle weakness, quadriceps strength deficits may persist for years. Moreover, this deficit leads to increased risk of sustaining another knee injury, and increased risk for developing posttraumatic osteoarthritis. At present, neither the optimal rehabilitative program nor the clinical and instrumental parameters to take into account at the time of return to activity have reached a consensus among clinicians.

The investigators hypothesize that:

* a persistent deficit in voluntary activation, that is an inability to achieve complete activation of a muscle, is present after ACLR.
* this deficit in voluntary activation is associated with a phenomenon of "learned/acquired non-use" both in balance and during gait. This phenomenon will be demonstrated by investigating asymmetries in the recruitment of the injured lower limb in balance tests and during gait.
* the "learned/acquired non-use" paradigm is associated to asymmetries in the hemispheric cortical activity. This phenomenon will be investigated through transcranial magnetic stimulation.

The primary endpoint is the demonstration that the quadriceps muscle weakness after ACLR may represent a case of "learned non-use". This behaviour looks automatic and unconscious, so that the adjective "acquired" seems preferable to "learned". It consists of the under recruitment of the impaired side, once healed, as a form of unconscious protection, which is adopted when the contralateral side may carry out the function.

The secondary outcome is the investigation of the correlation among the deficits in voluntary activation, in balance tests, during gait, and in the neurophysiologic trials, with the clinical conditions of the patients.

It is expected that the injured lower limb show a deficit in the activation of the quadriceps muscle with respect to the contralateral one and with respect to normative data. The impaired limb will present lower recruitment in balance tests and a deficit in power production during gait.

The contralesional hemisphere will demonstrate higher interhemispheric inhibition, lower short-interval intracortical inhibition (SICI) and higher short-interval intracortical facilitation (SICF) with respect to the ipsilesional hemisphere.

The evidence for an asymmetry between the two lower limbs would support the hypothesis that the "acquired non-use" paradigm has a role in the deficits following ACL lesions and that it is unspecific across asymmetric impairments, and independent of the underlying disease.

Results from the present study will allow:

* the identification of clinical and instrumental criteria to guide the return-to-sport decision following ACLR.
* the estimate of the sample size for future experimental protocols and new rehabilitative programs.

Conditions

• Anterior Cruciate Ligament Injuries

Interventions

DIAGNOSTIC_TEST

Pathologic group

Voluntary Activation level will be determined with the interpolate twitch technique (ITT), both during isometric contractions (knee at 40° flexion) and during isokinetic contraction at angular velocity equal to 100°/s. Vastus Medialis and Soleous H-reflex will be measured. Cortical excitability and interhemispheric connectivity will be measured through transcranial magnetic stimulation (TMS). Tests of balance in standing will be performed using the EquiTest platform. Individuals will be requested to perform three different tasks: Sensory Organization test, Adaptation Test upward/downward, Motor Control test backward/forward. Surface electromyography from lower limbs will be recorded. Through TMS driven by neuronavigation, the cortical representation of the Quadriceps muscle will be studied. Gait analysis will be performed on a treadmill mounted on force sensors. Participants will walk at increasing velocities from 0.4 m/s to 1.6 m/s. Speed will be increased of 0.2 m/s every 30 s.

Sponsors & Collaborators

• ASST Gaetano Pini-CTO

  collaborator OTHER

• Istituto Auxologico Italiano

  lead OTHER

Principal Investigators

• Luigi Tesio, MD, Full professor · Istituto Auxologico Italiano

Eligibility

Min Age

18 Years

Max Age

35 Years

Sex

MALE

Healthy Volunteers

No

Timeline & Regulatory

Start

2021-07-14

Primary Completion

2024-12-31

Completion

2024-12-31

Countries

• Italy

Study Locations