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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 H offmann 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.
Lepley et al. (Wed,) studied this question.