Differentiation of hamstring short latency versus medium latency responses after tibia translation

Abstract

After injuries to the anterior cruciate ligament (ACL) a functional instability is frequently observed which has been attributed to a disturbed sensorimotor function. In light of the clinical importance of ACL injuries and the resulting functional instability, it is of enormous clinical interest to elucidate the role of sensorimotor pathways that involve the ACL. In animals and humans a direct reflex pathway between the ACL and the hamstrings has been shown. The onset latencies of responses reported after ventral tibia translation were around 40-50 ms (range 17.9-65) and were regarded as medium latency responses (MLR). However, ventral tibia translation should also induce a stretch of the hamstring muscles and evoke a short latency response (SLR). Before any muscle response after ventral tibia translation can be ascribed to anatomical structures, it is crucial to analyze the obtained muscle responses carefully. The aim of the present study was the development of an algorithm to differentiate SLR and MLR responses after ventral tibia translation. In ten healthy subjects reflex responses of the hamstrings after anterior tibia translation and after tendon taps on the biceps femoris tendon were evaluated. To investigate the influence of skin afferents, control experiments were performed after lidocain injection of the dorsal calf. The mean onset latency of the tendon jerk reflex was 21.9 +/- 3.1 ms (range 17.3 - 28.7 ms). Both SLR responses (mean onset latency: 20.3 +/- 3.5 ms; range 15.4 - 25.8) and MLR responses (mean onset latency: 38.9 +/- 4.2 ms; range 32.9 - 46.7) were obtained in all subjects. Skin afferents from the calf do not play a major role. The development of an evaluation algorithm is presented that allows a safe differentiation between these partly superimposed SLR and MLR components. It is demonstrated that by measuring the first part of the SLR from the onset to the first peak the end of the SLR can be predicted and that the onset latency of the MLR component can be assessed reliably. Possible reasons are discussed why previous studies only reported responses at MLR latencies. The fact that both SLR and MLR components can be observed after anterior tibia translation underlines the necessity to differentiate the responses before they can be ascribed to any anatomical structures. As a basis for future work the algorithm presented may become a useful tool to differentiate which afferent pathways play a role in initiating hamstring activity.

An Extensive Evaluation of Different Knee Stability Assessment Measures: A Systematic Review

“…For example, the sensitivity and specificity of the Genucom knee analysis system have been reported to be low, at 60% and 65%, respectively [42].On the other hand, the KT-1000 sensitivity at maximum manual force is 93%, and it has a specificity of approximately 93% [16]. Despite the existing studies on the use of the hamstring-stretch reflex [26,[73][74][75], the literature lacks evidence on whether the reflex latency can be a valid objective clinical knee stability measure.…”

“…The reflex has been investigated intra-operatively by direct traction under arthroscopic visualization and in a research setting by instrumenting a laboratory-based rig [11]; thus, its clinical usefulness is doubtful. Three studies by Schoene et al [11], Friemert et al [26] and Melnyk et al [73] revealed that the ACL-hamstring reflex measurement could be elicited, specifically for injured ACLs. Previous work by Friemert et al [26] has shown that a prolonged reflex was present in patients with a ruptured ACL.…”

“…Three studies by Schoene et al [11], Friemert et al [26] and Melnyk et al [73] revealed that the ACL-hamstring reflex measurement could be elicited, specifically for injured ACLs. Previous work by Friemert et al [26] has shown that a prolonged reflex was present in patients with a ruptured ACL. The longer reflexes corresponded with patients who had instability symptoms even though mechanical testing with the KT-1000 showed no difference.…”

Intra-articular anesthesia and knee muscle response

“…Stimulation of receptors within the ACL and joint capsule has been shown to produce reflexive contractions in the hamstring muscles (Tsuda et al, 2001, Fujita et al, 2000, Friemert et al, 2005, Di Fabio et al, 1992, Dhaher et al, 2003. Tsuda et al (2001) verified the presence of the ACL-hamstring reflex loop by applying electrical stimulation to the ACL before and after a local anesthetic injection in the joint.…”

“…Capsular, muscular, and ligamentous receptors are responsible for initiating automatic neuromuscular responses that protect the knee (Dhaher et al, 2003, Di Fabio et al, 1992, Friemert et al, 2005, Wojtys and Huston, 1994. The interaction of the receptors and the mechanisms of the response are unclear.…”