Efficacy of a semirigid ankle brace in reducing mechanical ankle instability evaluated by 3D stress-MRI

Helge Eberbach,Thomas Lange,Spartak Ovsepyan,Albert Gollhofer,Dominic Gehring,Markus Wenning,Hagen Schmal

doi:10.1186/s13018-021-02750-6

Abstract

BackgroundNovel imaging technologies like 3D stress-MRI of the ankle allow a quantification of the mechanical instability contributing to chronic ankle instability. In the present study, we have tested the efficacy of a semirigid ankle brace on joint congruency in a plantarflexion/supination position with and without load.MethodsIn this controlled observational study of n = 25 patients suffering from mechanical ankle instability, a custom-built ankle arthrometer implementing a novel 3D-stress MRI technique was used to evaluate the stabilizing effect of an ankle brace. Three parameters of joint congruency (i.e., 3D cartilage contact area fibulotalar, tibiotalar horizontal and tibiotalar vertical) were measured. The loss of cartilage contact area from neutral position to a position combined of 40° of plantarflexion and 30° of supination without and with axial load of 200 N was calculated. A semirigid ankle brace was applied in plantarflexion/supination to evaluate its effect on joint congruence. Furthermore, the perceived stability of the brace during a hopping task was analyzed using visual analogue scale (VAS).ResultsThe application of a semirigid brace led to an increase in cartilage contact area (CCA) when the foot was placed in plantarflexion and supination. This effect was visible for all three compartments of the upper ankle joint (P < 0.001; η2 = 0.54). The effect of axial loading did not result in significant differences. The subjective stability provided by the brace (VAS 7.6/10) did not correlate to the magnitude of the improvement of the overall joint congruency.ConclusionsThe stabilizing effect of the semirigid ankle brace can be verified using 3D stress-MRI. Providing better joint congruency with an ankle brace may reduce peak loads at certain areas of the talus, which possibly cause osteochondral or degenerative lesions. However, the perceived stability provided by the brace does not seem to reflect into the mechanical effect of the brace.Trial registration The study protocol was prospectively registered at the German Clinical Trials Register (#DRKS00016356).

Highlights

Novel imaging technologies like 3D stress-MRI of the ankle allow a quantification of the mechanical instability contributing to chronic ankle instability
Due to this interaction leading to a combined neuromechanical effect, it is still subject to debate whether the amount of stabilization provided by ankle braces under load exceeds the effect of the active, neuromuscular stabilization [9, 10]
The average loss of contact area (CCA) was 10.6% less for CCAFT, 8.0% less for CCATTH and 18.7% for CCATTV compared to the no-brace condition

Summary

Introduction

Novel imaging technologies like 3D stress-MRI of the ankle allow a quantification of the mechanical instability contributing to chronic ankle instability. Chronic ankle instability (CAI) arises from the two etiologies of functional (FAI) and mechanical ankle instability (MAI), whose interaction is the subject of ongoing research. The effectiveness of external supports lies in the limitation of joint excursion which reduces maximum inversion angle and angular velocity [6, 7]. These effects are accompanied by functional adaptations, e.g., the preparatory muscle activation, which is increased when wearing an external support [6, 8]. Imaging studies have visualized the effect of ankle braces using different modalities like stress-roentgenology, arthrometric testing or, more recently, computed tomography [12,13,14]

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