Biomechanical comparison of 3 ankle braces with and without free rotation in the sagittal plane.
Alfuth M, Klein D, Koch R, Rosenbaum D. J of Athl Training. 2014; 49(5): 608-616.
Take Home Message: In both passive and dynamic conditions, hinged and unhinged ankle braces increased ankle stability compared with no brace. There was no clinical relevant differences between braces.
Lateral ankle sprains are commonly sustained during physical activity. Ankle braces are recommended to reduce the risk of an ankle sprain; however, there are various ankle brace designs. A better understanding of how well different ankle brace designs limit ankle range of motion would help clinicians recommend ankle brace models that would best to reduce the risk of a lateral ankle sprain. Therefore, Alfuth and colleagues completed a within-subject crossover study to assess the ability of 3 different ankle braces to limit ankle range of motion during dynamic and passive motion. The authors recruited 17 healthy participants. All participants were physically active and had no history of ankle injuries in the past 6 months. The authors tested the participants while wearing each of the 3 commercially available ankle braces as well as the control condition for both the dynamic and passive testing protocol. The order of the ankle braces and control condition was randomized. One brace had a semi-rigid shell with foam-filled air cells and crossing straps (AirCast AirGo). The second brace was hinged with polypropylene shells and crossing straps (DARCO Body Armor Embrace). The third brace was a neoprene sock with a flexible hinged outer cast, which could be tightened with a hook-and-loop strap (McDavid Ankle X). During the dynamic testing protocol participants stood on a hinged platform. The tester then induced an unexpected 30⁰ foot inversion. Inversion movement was measured with an in-shoe goniometer for all conditions. During passive testing, participants were secured into an apparatus which passively moved the ankle in 3 movement planes (6 directions) at a defined torque (12Nm for dorsiflexion, 9Nm for 5 other movements). Overall, the 3 brace models reduced ankle inversion compared with the control condition during dynamic and passive testing. During passive testing, all of the braces limited plantar flexion (~4 to 17 degrees) and dorsiflexion (~2 to 4 degrees) compared with no brace. Passive testing revealed the hinged brace without a neoprene sleeve (Embrace) allowed more ankle motion than either hinged brace. While the hinged brace with a neoprene sleeve (Ankle X) restricted ankle inversion the most during the dynamic test it also permitted more plantar flexion (~10 degrees) than the brace without a hinge (AirGo). While all 3 braces allowed different amounts of ankle inversion, the authors acknowledged that the difference between hinged and non-hinged models was not clinically relevant.
Overall, the current study suggests that ankle braces significantly reduce ankle dynamic and passive ankle inversion range of motion. Further, the data suggests that this remains true regardless of whether or not the ankle brace is a hinged or un-hinged model. The results of the current study should be of interest to clinicians who recommend ankle braces to physically active individuals. While this information is useful, clinicians should be aware that other ankle brace models that were not tested in this study may respond differently. Participants also had no ankle injury at the time of testing. It is conceivable that injured athletes’ ankles would respond differently due to proprioceptive deficits as a result of the injury. Furthermore, participants were not in a fatigued state when tested. This may alter the results as muscle fatigue may lead to a delayed response in compensating for ankle inversion. Despite these limitations, this study indicates that clinicians could recommend hinged or unhinged ankle braces for physically active individuals who hope to reduce their risk of an ankle sprain.
Questions for Discussion: Do you recommend ankle braces to your athletes with chronic ankle instability? If so, do you tend to recommend specific models or ankle braces with specific features?
Written by: Kyle Harris
Reviewed by: Jeffrey Driban