1995 Achilles Research Award Winner:

The Effects of an Isolated Ankle Effusion on H-Reflex Amplitude, Viscoelasticity and Postural Control of the Ankle

A. Amendola, M.D. , J. Petrik, M.Sc., R. Rampersand, M.D.,
S. Mabey, M.Sc., K.C. Hayes, Ph.D.
University of Western Ontario
London, Ontario, Canada

The objective of this study was to elucidate the neuromuscular, mechanical and functional consequences of a simulated ankle joint effusion. Two groups (N1 = 16, N2 = 15) had laboratory induced unilateral ankle effusions (10 cc's of normal saline). Both legs were evaluated in an identical fashion pre- and post-effusion. In group 1, H-reflex and M-response amplitudes of the gastro-soleous muscle complex, were evaluated. These subjects also underwent measurement of the viscoelastic properties of the ankle in response to low frequency, passive sinusoidal displacement. The second group performed a series of balance tasks in which the excursion of the centre pressure provided indices of postural stability.

A significant increase in H-reflex and M-response (p < 0.05) was observed in the experimental leg of all subjects. There was also a significant increase in H-reflex amplitude (p < 0.01) in the control leg. The effused ankle demonstrated a significant increase in viscoelastic resistance (p < 0.05) to passive motion. Postural sway was decreased in the anterior to posterior plane (p < 0.05) in both the experimental and control legs. There was no difference in medial to lateral sway. The results of this study demonstrate an afferent neural feedback mechanism from the distended ankle joint capsule. The afferent feedback leads to facilitation of the gastro-soleus muscle complex, and a protective effect on postural sway in the antero-posterior direction.

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