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Precision orthotics: optimising ankle foot orthoses to improve gait in patients with neuromuscular diseases; protocol of the PROOF-AFO study, a prospective intervention study
  1. Niels F J Waterval1,
  2. Frans Nollet1,
  3. Jaap Harlaar2,
  4. Merel-Anne Brehm1
  1. 1Department of Rehabilitation, Academic Medical Center, University of Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
  2. 2Department of Rehabilitation Medicine, VU University Medical Center, Amsterdam Movement Sciences, The Netherlands
  1. Correspondence to Niels F J Waterval; n.f.waterval{at}


Introduction In patients with neuromuscular disorders and subsequent calf muscle weakness, metabolic walking energy cost (EC) is nearly always increased, which may restrict walking activity in daily life. To reduce walking EC, a spring-like ankle-foot-orthosis (AFO) can be prescribed. However, the reduction in EC that can be obtained from these AFOs is stiffness dependent, and it is unknown which AFO stiffness would optimally support calf muscle weakness. The PROOF-AFO study aims to determine the effectiveness of stiffness-optimised AFOs on reducing walking EC, and improving gait biomechanics and walking speed in patients with calf muscle weakness, compared to standard, non-optimised AFOs. A second aim is to build a model to predict optimal AFO stiffness.

Methods and analysis A prospective intervention study will be conducted. In total, 37 patients with calf muscle weakness who already use an AFO will be recruited. At study entry, participants will receive a new custom-made spring-like AFO of which the stiffness can be varied. For each patient, walking EC (primary outcome), gait biomechanics and walking speed (secondary outcomes) will be assessed for five stiffness configurations and the patient's own (standard) AFO. On the basis of walking EC and gait biomechanics outcomes, the optimal AFO stiffness will be determined. After wearing this optimal AFO for 3 months, walking EC, gait biomechanics and walking speed will be assessed again and compared to the standard AFO.

Ethics and dissemination The Medical Ethics Committee of the Academic Medical Centre in Amsterdam has approved the study protocol. The study is registered at the Dutch trial register (NTR 5170). The PROOF-AFO study is the first to compare stiffness-optimised AFOs with usual care AFOs in patients with calf muscle weakness. The results will also provide insight into factors that influence optimal AFO stiffness in these patients. The results are necessary for improving orthotic treatment and will be disseminated through international peer-reviewed journals and scientific conferences.

  • Ankle-foot-orthosis
  • Gait
  • Walking energy cost
  • Neuromuscular disorders

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  • Contributors M-AB, FN and JH conceived this study. M-AB, FN, JH and NFJW contributed to the conception of the study design and participated in logistical planning of the study. NFJW is responsible for data acquisition and drafted the manuscript. M-AB, FN and JH critically appraised the draft versions of this manuscript and approved the final version.

  • Funding This study was supported by the Prinses Beatrix Spierfonds, grant number [W.0R 14-21]. OIM Noppe Orthopedie is thanked for manufacturing the intervention AFOs and Otto Bock for providing the Carbon Ankle Seven leaf springs.

  • Competing interests None declared.

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

  • Data sharing statement Data sets and statistical codes will be available on request.

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