An exercise and patient education intervention to reduce pain and physical limitations in adults with acetabular dysplasia: study protocol for a process evaluation integrated within a randomised controlled trial (the MovetheHip trial)

Background
The Movethehip trial investigates the effectiveness of an exercise and patient education intervention for adults with acetabular dysplasia. The intervention involves eight tailored one-to-one sessions with trained providers who employ supportive feedback tools. The present protocol reports a planned process evaluation, which aims to determine how the intervention functions by examining the implementation of the intervention (process, dose and reach), its acceptability, mechanisms of change and the influence of contextual factors.

Methods
Two hundred trial participants aged 18–50 years will be recruited from a University Hospital in Denmark and randomised to the intervention or control group. Approximately ten providers will deliver the intervention. The process evaluation adopts a concurrent mixed-methods design. The implementation will be assessed using self-report questionnaires (at baseline and 6-month follow-up), training records and semi-structured focus group interviews with intervention providers (n=10) and healthcare managers (n=4–6). The mechanisms of change will be explored through semi-structured one-to-one interviews (at baseline and 6-month follow-up) with 15–20 purposefully sampled participants and by measuring changes in health outcomes (self-reported pain, physical functioning and quality of life completed at baseline and at 3- and 6-month follow-up). Additionally, change will be measured through an explorative examination of associations between dose and change in health outcomes, applying simple linear regression models. The acceptability of the intervention and the influence of contextual factors will be explored through one-to-one participant interviews and focus group interviews with 4–6 healthcare managers. The interviews will focus on expectations, experiences, events, personal understandings and interaction with interpersonal and organisational aspects. Interview data will be analysed using theoretical thematic analyses, and findings will be merged with quantitative data and reported jointly on a theme-by-theme basis.

Discussion
The process evaluation conducted as part of the MovetheHip trial will illuminate how the intervention functions, and if the intervention is proven effective, the fndings of the evaluation will contribute to pinpoint how the intervention may be optimised to facilitate future up-scaling and implementation.

Trial registration The MovetheHip protocol was approved by the Committee on Health Research Ethics in the Central Denmark Region. ClinicalTrials, NCT04795843. Registered on 20 March 2021.