Abstract
The anterior cruciate ligament (ACL) plays an important role in anterior knee stability by preventing anterior translation of the tibia on the femur. Rapid translation of the tibia with respect to the femur produces an ACL-hamstring stretch reflex which may provide an object measure of neuromuscular function following ACL injury or reconstruction. The aim of this study was to determine if the ACL-hamstring stretch reflex could be reliably and consistently obtained using the KT-2000 arthrometer. A KT-2000 arthrometer was used to translate the tibia on the femur while recording the electromyography over the biceps femoris muscle in 20 participants, all with intact ACLs. In addition, a sub-group comprising 4 patients undergoing a knee arthroscopy for meniscal pathology, were tested before and after anaesthetic and with direct traction on the ACL during arthroscopy. The remaining 16 participants underwent testing to elicit the reflex using the KT-2000 only. A total number of 182 trials were performed from which 70 trials elicited stretch reflex (38.5 %). The mean onset latency of the hamstring stretch reflexes was 58.9 ± 17.9 ms. The average pull force was 195 ± 47 N, stretch velocity 48 ± 35 mm/s and rate of force 19.7 ± 6.4 N/s. Based on these results, we concluded that the response rate of the anterior cruciate ligament-hamstring reflex is too low for it to be reliably used in a clinical setting, and thus would have limited value in assessing the return of neuromuscular function following ACL injuries.
Highlights
The anterior cruciate ligament (ACL) plays an important role in anterior knee stability by preventing anterior translation of the tibia on the femur
Based on these results, we concluded that the response rate of the anterior cruciate ligament-hamstring reflex is too low for it to be reliably used in a clinical setting, and would have limited value in assessing the return of neuromuscular function following ACL injuries
There was no difference in the percentage of reflexes elicited with the KT-2000 before anaesthesia (30 %) and after anaesthesia (29 %), or with direct traction on the ACL (42 %) (Fig. 4)
Summary
The anterior cruciate ligament (ACL) plays an important role in anterior knee stability by preventing anterior translation of the tibia on the femur. Schoene et al (2009) noted that both the mechanical and functional (sensorimotor) components of the knee play a role in the subjective feeling of instability following ACL reconstruction. They defined functional instability as a feeling of instability due to muscular dysfunction, which is caused by impaired neuromuscular function. Various authors have noted that deficits in proprioception, balance, strength and neuromuscular control may persist for months following an injury or surgery (Lam et al 2009; Torg et al 1976; Tsuda et al 2001) Assessment of these factors may be crticial for the return to play decision. As a result there is a need for clinic-based objective measures of neuromuscular function to aid the return to play decision
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