Neural Excitability and Joint Laxity in Chronic Ankle Instability, Coper, and Control Groups
Bowker, S, Terada M, Thomas AC, Pietrosimone BG, Hiller CE, Gribble PA. J Athl Train. 2016 Apr 11 [Epub ahead of print]
Take Home Message: A group of individuals with chronic ankle instability have sensorimotor system deficits compared with a group of healthy controls and copers; however, the authors found no mechanical differences between any of the groups.
One of the most common sports injuries are ankle sprains. Unfortunately, many individuals that suffer an ankle sprain develop prolonged ankle dysfunction, which is known as chronic ankle instability. A better understanding of the differences between individuals that develop chronic ankle instability and those that do not (copers) could provide clinicians with better evidence-based decisions when evaluating and treating initial ankle sprains. Therefore, Bowker and colleagues conducted a case-control study of individuals with chronic ankle instability, copers that did not report chronic dysfunction following an initial ankle sprain, and a group of healthy controls to investigate the differences in ankle laxity and neural excitability. Ninety-three physically active volunteers participated in the study. Thirty-seven (18 male) volunteers had chronic ankle instability based upon recommendations from the International Ankle Consortium, 30 (13 male) volunteers were copers who were defined as individuals with a history of ankle sprains that were not accompanied with episodes of the ankle giving way, perceived instability, or loss of function. Additionally, 26 (9 male) were healthy controls. The authors assessed ankle laxity using an instrumented ankle arthrometer that measured the total displacement in the anterior-posterior (mm) directions and total rotation in the inversion-eversion (°) directions. To assess neural excitability, they measured spinal reflex excitability of the soleus muscle using the Hoffmann reflex to determine the maximum Hoffmann reflex to maximum muscle response (H:M ratio) ratio. The authors showed that participants with chronic ankle instability had less spinal excitability in the soleus muscle compared with the coper and healthy control groups. However, spinal reflex excitability was not different between the copers and healthy controls. There were no differences between any of the groups for either of the ankle laxity measures.
The data from this study support the idea that the differences between individuals with chronic ankle instability versus those that who cope after an ankle sprain may have more to do with changes in the sensorimotor system than ankle laxity. Other studies have reported neural excitability deficits in people with chronic ankle instability; but, this study highlights the potential need for appropriate interventions to address neural excitability deficits. Potentially, certain therapeutic interventions that affect nervous system excitability such as joint mobilizations and manipulations, muscle energy technique, cryotherapy, and transcutaneous electrical stimulation could be used for patients with chronic ankle instability. However, we don’t know if or how these common clinical interventions would impact the neural excitability changes of the soleus in patients with chronic ankle instability. It is also difficult for most clinicians to easily assess spinal reflex excitability and may force them to rely upon subjective clinical complaints. Additionally, we also need prospective studies because we do not know if the presence of these neural deficits can predict who will struggle with chronic ankle instability or those that will be able to cope effectively. Fortunately, many of the interventions that could help are low cost, low risk, and many of them are already commonplace in clinical settings. Therefore, it may be a good idea for clinicians to incorporate some of these techniques into rehabilitation protocols of patients with a history of recurrent ankle sprains or chronic ankle instability.
Questions for Discussion: Do you focus your rehabilitative efforts on both potential mechanical and neurological changes for ankle sprains? Have you used manual therapies with a non-mechanical model of efficacy? How do you implement neural training into your rehabilitation programs?
Written By: Adam Kelly, MS, ATC
Reviewed By: Jeffrey Driban