A Novel Ankle-supinating Device

Abstract

Lateral ankle sprains (LAS) are common injuries and while many are resolved with treatment, others develop Ankle Instability (AI). It follows that considerable attention has been directed towards understanding the underlying causes of this pathology, however little is known to date concerning the neuromuscular mechanisms behind the development of AI, possibly due to a dearth of analyses of individuals with AI in dynamic conditions. PURPOSE: To perform a pilot kinematic and EMG analysis of the landing phase of a drop jump onto a device which simulates the mechanism of a LAS in persons with AI (AI group), persons who‘ve suffered a LAS, but did not develop AI (NO group), and uninjured controls (CO group). METHODS: Six subjects with bilaterally equivalent ankle status were divided equally into the 3 groups. A pneumatic rotary actuator powered the rotation of a landing plate via a linkage system, aiming to safely mimic a LAS event. The protocol included subjects dropping off a take-off platform (test leg first) and landing with both feet simultaneously onto the device and surrounding landing platform; followed by an immediate jump "as high and fast as possible“. Subjects were familiarized with the protocol, then 10 experimental trials were performed with 3 supinating and 7 non-supinating trials in a random order, unknown to the subject. Markers were placed according to a modified Helen Hayes marker set and EMG was performed on the Tibialis Anterior (TA) and Peroneus Longus (PL). Due to the pilot nature and low power, only descriptive statistics were calculated. RESULTS: Kinematics indicated that the platform created a perturbation causing increased ankle plantar flexion (∼8°), adduction (∼9°), and inversion (∼13°). The EMG data suggests NO subjects demonstrate an increased activation of the PL prior to landing and in response to a perturbation, relative to the other groups. CONCLUSION: The device adequately simulates the mechanism of a LAS in a safe, controlled environment, even in individuals with AI. The preliminary EMG data suggests the work evaluating subjects who have a previous history of at least one LAS and don‘t experienced recurrent symptoms may help elucidate some compensatory mechanisms or more appropriate neuromuscular control strategies following a LAS, so more appropriate treatment paradigms can be developed.