Differential effects of semi-rigid and soft orthoses on postural control between affected and unaffected leg in patients with functional ankle instability in compared with healthy subjects

Introduction: Postural control deficits after lateral ankle sprain have been shown in patients withfunctional ankle instability (FAI). Numerous researchers have shown different effects of orthosis onpostural control in FAI patients. It seems that the condition of chosen control group might explain thedifferent results obtained from those studies. To the authors' knowledge, no study has compared theeffect of orthosis on postural control against different control conditions.Materials and Methods: Twenty patients with functional instability of ankle and twenty werematched healthy subjects participated in the study. Postural control in single limb stance was assessedfor both affected and unaffected foot while using soft and semi-rigid orthosis. Standing without usingorthosis was considered as the baseline condition. Balance control was evaluated by force platform.Results: Our results showed that interaction between group and orthosis was significant for all ofthe parameters extracted from center of pressure (COP) data, meaning that orthosis has a differentialeffect on postural control between the two groups. Also, interaction between foot side and orthosiswas not significant for all of the COP parameters. In another words, orthosis has the same effect oninvolved and uninvolved foot side.Conclusion: Although orthosis improved postural stability in patients with FAI, it showed no suchan effect in healthy subjects. As the other finding, it was demonstrated that orthosis has no differentialeffect on postural control between involved and uninvolved foot side in both groups. Therefore, thepositive effects of orthosis on postural control in FAI patients may be revealed when healthy subjectsare involved as control group in research design.