Quadriceps neural alterations in anterior cruciate ligament reconstructed patients: A 6‐month longitudinal investigation

Abstract

The purpose of this investigation was to evaluate differences in quadriceps corticospinal excitability, spinal-reflexive excitability, strength, and voluntary activation before, 2 weeks post and 6 months post-anterior cruciate ligament reconstruction (ACLr). This longitudinal, case-control investigation examined 20 patients scheduled for ACLr (11 females, 9 males; age: 20.9 ± 4.4 years; height:172.4 ± 7.5 cm; weight:76.2 ± 11.8 kg) and 20 healthy controls (11 females, 9 males; age:21.7 ± 3.7 years; height: 173.7 ± 9.9 cm; weight: 76.1 ± 19.7 kg). Maximal voluntary isometric contractions (MVIC), central activation ratio (CAR), normalized Hoffmann spinal reflexes, active motor threshold (AMT), and normalized motor-evoked potential (MEP) amplitudes at 120% of AMT were measured in the quadriceps muscle at the specific time points. ACLr patients demonstrated bilateral reductions in spinal-reflexive excitability compared with controls before surgery (P = 0.02) and 2 weeks post-surgery (P ≤ 0.001). ACLr patients demonstrated higher AMT at 6 months post-surgery (P ≤ 0.001) in both limbs. No MEP differences were detected. Quadriceps MVIC and CAR were lower in both limbs of the ACLr group before surgery and 6 months post-surgery (P ≤ 0.05) compared with controls. Diminished excitability of spinal-reflexive and corticospinal pathways are present at different times following ACLr and occur in combination with clinical deficits in quadriceps strength and activation. Early rehabilitation strategies targeting spinal-reflexive excitability may help improve postoperative outcomes, while later-stage rehabilitation may benefit from therapeutic techniques aimed at improving corticospinal excitability.

Longitudinal changes in knee gait mechanics between 2 and 8 years after anterior cruciate ligament reconstruction

“…Interestingly, the kinetic changes over time in the contralateral limb tended to mimic the pattern of the ACLR limb, with no differences observed in changes over time between the reconstructed and contralateral limbs. The symmetric adaptation over time suggests, consistent with previous work reporting bilateral neuromuscular alterations after ACL injury 28–31 , that the ACLR patients adapted their gait symmetrically.…”

Visual-Motor Control of Drop Landing After Anterior Cruciate Ligament Reconstruction

“…[11][12][13][14] Rectifying the biomechanical profile via standard neuromuscular training is a vital component of the rehabilitation process, but it may be possible to further improve neuromuscular function and decrease the reinjury risk by examining sensory and neural variables that contribute to postinjury disability. 15,16 For example, researchers [17][18][19][20][21] have demonstrated unresolved neurologic alterations after injury, reconstruction, and rehabilitation that may limit function and delay the return to sport participation. By targeting neurologic factors during neuromuscular rehabilitation progressions, clinicians may be able to improve the transfer of sensorimotor adaptations from the clinic to activity and ultimately improve patient outcomes.…”

Unilateral Quadriceps Strengthening With Disinhibitory Cryotherapy and Quadriceps Symmetry After Anterior Cruciate Ligament Reconstruction

“…These observations highlight an interesting and potentially challenging disconnect between a common clinical criterion, limb symmetry, used to measure improvement from rehabilitation after ACLR and the actual functional status of the individual. Whereas the potential limitations of symmetry as a measure have been described, our findings further the understanding that comparing unilateral knee-extension strength and quadriceps activation with preinjury levels, 38 population-based norms, 39 or patient-centered cutoff scores 15,40 may add value to the LSI. Restoring limb symmetry for knee-extension strength and quadriceps activation, coupled with a return to normal involved-limb quadriceps function, may promote an optimal outcome for individuals after ACLR.…”