STEPFORWARD: Next steps for a randomised controlled trial of the clinical and cost-effectiveness of a hydraulic self-aligning ankle-foot for patients with a below-knee amputation categorised as having "limited community mobility"

Name: Natalie Vanicek

E-mail: n.vanicek@hull.ac.uk

Occupation: Professor

Affiliation: University of Hull, UK

Other authors: Cleveland Barnett, Martin Twiste, Chantel Ostler on behalf of the STEPFORWARD group

 

ABSTRACT

BACKGROUND

In the UK, most amputations are below-the-knee (BKA) in adults aged over 50 years because of problems related to vascular disease and/or diabetes. These patients are often categorised as having “limited community mobility” or as “K2 users”. They are usually prescribed a prosthetic ankle-foot that is not very flexible and does not self-align to sloped surfaces. Self-aligning (hydraulic) ankle-feet are available, but seldom prescribed to K2 users on the NHS due to additional costs. The largest group of patients with a BKA (K2 users) could benefit from advances in prosthetic technology, but insufficient evidence to justify the extra cost means clinicians do not routinely prescribe them.

IMPORTANCE

Our patient public involvement members said that a less flexible prosthetic ankle-foot foot makes walking more difficult, uncomfortable and more exhausting and may stop them from using their prosthesis, leading to a less active, less healthy and less independent lifestyle.

FEASIBILITY STUDY

In 2018-20, we conducted an NIHR-funded randomised controlled feasibility study (STEPFORWARD)(1). We randomised 55 patients: half kept their existing ankle-foot and half received a self-aligning ankle-foot (Avalon-K2, Blatchford). 93% of participants completed the study and 89-95% of our outcome measures were completed. Three outcomes showed a signal of efficacy: 2-minute walk test, health-related quality-of-life (QOL) and step count. Patient and clinician interviews informed the outcome measures for a full-scale trial and confirmed the study procedures were acceptable to them.

NEXT STEPS

We intend to deliver a multi-centre RCT to assess the clinical and cost-effectiveness of a self-aligning ankle-foot for K2 patients with a BKA. This pragmatic, parallel group trial will assess the impact of a self-aligning ankle foot on walking ability (primary outcome); physical function, balance and QOL (secondary outcomes); and cost-effectiveness of this ankle-foot for K2 patients. We plan to recruit 358 K2 patients with a BKA and who use a non-self-aligning ankle-foot across 15 prosthetics sites. They will be randomised 1:1 to the intervention or control group, so half will receive a self-aligning ankle-foot (Avalon-K2, Blatchford or Odyssey-K2, Steeper) and half will keep their existing ankle-foot. We will follow patients every three months for one year. We intend to have 15 participating prosthetics sites, who will recruit 1-2 patients every month for up to 23 months. Each site will recruit on average 24 patients.

EQUIPOISE

There is insufficient evidence that a self-aligning ankle-foot would benefit and be cost-effective for K2 patients. We have worked with patient public involvement members throughout STEPFORWARD. They are hugely supportive of this large-scale study and would be willing to be randomised in this trial. Clinicians have confirmed their willingness to randomise patients. Any site that routinely prescribes self-aligning ankle-feet to this patient group will not be involved.

WHERE WE ARE

A robust, large-scale, fully powered clinical trial to compare the clinical and cost-effectiveness of more functional ankle-feet for K2 patients is long overdue(2). STEPFORWARD would be the first trial to do so and guide clinical decision-making. We have applied to the NIHR Health Technology Assessment (HTA) fund for a 4-year study starting October 2023.

1. Vanicek N, Coleman E, Watson J, Bell K, McDaid C, Barnett C, et al. STEPFORWARD study: a randomised controlled feasibility trial of a self-aligning prosthetic ankle-foot for older patients with vascular-related amputations. BMJ open. 2021;11(3):13.

2. Hofstad CJ, van der Linde H, van Limbeek J, Postema K. Prescription of prosthetic ankle-foot mechanisms after lower limb amputation. Cochrane Database of Systematic Reviews. 2004(1).