Does the Spraino low-friction shoe patch prevent lateral ankle sprain injury in indoor sports? A pilot randomised controlled trial with 510 participants with previous ankle injuries

Abstract

Background: Lateral ankle sprains are common in indoor sports. High shoe-surface friction is considered a risk factor for non-contact lateral ankle sprains. Spraino is a novel low-friction patch that can be attached to the outside of sports shoes to minimise friction at the lateral edge, which could mitigate the risk of such injury. We aimed to determine preliminary effectiveness (incidence rate and severity) and safety (harms) of Spraino to prevent lateral ankle sprains among indoor sport athletes.

Methods: In this exploratory, parallel-group, two-arm pilot randomised controlled trial, 510 subelite indoor sport athletes with a previous lateral ankle sprain were randomly allocated (1:1) to Spraino or 'do-as-usual'. Allocation was concealed and the trial was outcome assessor blinded. Match and training exposure, number of injuries and associated time loss were captured weekly via text messages. Information on harms, fear-of-injury and ankle pain was also documented.

Results: 480 participants completed the trial. They reported a total of 151 lateral ankle sprains, of which 96 were categorised as non-contact, and 50 as severe. All outcomes favoured Spraino with incidence rate ratios of 0.87 (95% CI 0.62 to 1.23) for all lateral ankle sprains; 0.64 (95% CI 0.42 to 0.98) for non-contact lateral ankle sprains; and 0.47 (95% CI 0.25 to 0.88) for severe lateral ankle sprains. Time loss per injury was also lower in the Spraino group (1.8 vs 2.8 weeks, p=0.014). Six participants reported minor harms because of Spraino.

Conclusion: Compared with usual care, athletes allocated to Spraino had a lower risk of lateral ankle sprains and less time loss, with only few reported minor harms.

Trial registration number: NCT03311490.

Keywords: ankle; injury prevention; randomised controlled trial; sports; sprain.

Conflict of interest statement

Competing interests: TBG is the founder of Spraino ApS. FGL is a paid employee in Spraino ApS. Spraino ApS was responsible for provision of Spraino. The conflict was accommodated by restricting Spraino ApS and authors FGL and TBG from having any deciding role in the design of the study, in the execution, analyses, interpretation of data, or decision to submit results. Statistical analyses were performed externally by JS who was blinded to group allocation. KT had full authority of the trial administration. The three senior clinical researchers (KT, TB and ED) had full authority in terms of submission for publication. Copenhagen Center for Health Technology (CACHET) and Innovation Fund Denmark had no scientific role in the trial. KT is an Associate Editor of the British Journal of Sports Medicine. ED is a Senior Associate Editor of the British Journal of Sports Medicine in the area of foot and ankle injuries.

© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

Figures

Figure 1

Indoor sports shoe with Spraino low-friction patches attached on the outside.

Figure 2

Preventive mechanism of Spraino: in case of a bad landing, Spraino minimises the otherwise high shoe–surface friction at the lateral edge of the shoe. This minimises the horizontal ground reaction forces (GRFs), thereby bringing the GRF vector closer towards the joint centre which serves to prevent excessive ankle inversion and internal rotation.

Figure 3

Consolidated Standards of Reporting Trials flow diagram.