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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
  1. Filip Gertz Lysdal1,2,
  2. Thomas Bandholm3,4,
  3. Janne Schurmann Tolstrup5,
  4. Mikkel Bek Clausen6,7,
  5. Stephanie Mann4,
  6. Pelle Baggesgaard Petersen8,
  7. Thor Buch Grønlykke2,
  8. Uwe G Kersting1,9,
  9. Eamonn Delahunt10,11,
  10. Kristian Thorborg3,6
  1. 1 Department of Health Science and Technology, Sport Sciences, Aalborg University, Aalborg, Denmark
  2. 2 Spraino ApS, Copenhagen, Denmark
  3. 3 Department of Physical and Occupational Therapy, Physical Medicine and Rehabilitation Research—Copenhagen, Amager-Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark
  4. 4 Clinical Research Centre, Amager-Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark
  5. 5 National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark
  6. 6 Department of Orthopedic Surgery, Sports Orthopedic Research Center—Copenhagen, Amager-Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark
  7. 7 School of Physiotherapy, Department of Midwifery, Physiotherapy, Occupational Therapy and Psychomotor Therapy, Faculty of Health, University College Copenhagen, Copenhagen, Denmark
  8. 8 Section for Surgical Pathophysiology 7621, Rigshospitalet, University of Copenhagen, Rigshospitalet, Copenhagen, Denmark
  9. 9 Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Cologne, Germany
  10. 10 School of Public Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland
  11. 11 Institute for Sport and Health, University College Dublin, Dublin, Ireland
  1. Correspondence to Filip Gertz Lysdal, Department of Health Science and Technology, Sport Sciences, Aalborg University, Aalborg 9220, Denmark; fgly{at}


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.

  • sports
  • ankle
  • sprain
  • randomised controlled trial
  • injury prevention

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  • Twitter @FilipGertz, @TBandholm, @MikkelBek, @EamonnDelahunt, @KThorborg

  • Contributors TBG, FGL and UK conceived the study. KT, TB, ED, PBP and MBC designed the trial. TBG and UK were grant holders. SM managed the collection of data under the supervision of MBC. JST provided statistical and epidemiological expertise and conducted the statistical analyses. TB, KT and ED provided clinical scientific expertise throughout the study. KT supervised the study in its entirety. All authors contributed to refinement of the article and approved the final manuscript.

  • Funding The trial was funded by Copenhagen Center for Health Technology (CACHET), grant number RFH-15-00013 and Innovation Fund Denmark, grant number 7038-00087A. Spraino ApS provided the low-friction shoe patches, worth approx. €19 000.

  • 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.

  • Patient and public involvement Patients and/or the public were involved in the design, or conduct, or reporting, or dissemination plans of this research. Refer to the Methods section for further details.

  • Patient consent for publication Not required.

  • Ethics approval Ethics approval was obtained from The North Denmark Region Committee on Health Research Ethics on 5 July 2017.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available upon reasonable request.