A Pilot Three Arm Randomised Controlled Trial and Qualitative Study of Extracorporeal Shockwave Therapy for Diabetic Foot Ulcer Healing (<scp>SOLEFUL</scp>): A Study Protocol

The development of effective interventions for diabetes-related foot ulcers (DFU) healing is vital. This protocol outlines a pilot trial and qualitative study investigating ESWT in DFU healing. A pilot three arm placebo controlled double-blinded randomised controlled trial. Participants with a DFU will be randomised to high dose (500 shocks/cm²), low dose (100 shocks/cm²) or sham ESWT, in addition to standard care. The primary outcome will be deliverability of a definitive trial. Secondary outcomes are ulcer healing, quality-of-life and healthcare resource use at 6 months. The target sample size is 90 participants. The study is registered on clinicaltrials.gov, reference: NCT05380544 and has ethical approval (REC reference: 22/WA/0089). The qualitative interview study will recruit participants who complete, drop-out and decline to participate in the pilot trial, and healthcare professionals who deliver DFU care. Maximum variable sampling will be used to recruit participants. Data will be analysed with an inductive exploratory approach using reflexive thematic analysis. The pilot trial will ensure methods used will address the research question in the definitive trial. The qualitative study will explore how patients and clinicians interact with the trial to understand the pilot trial findings.