Influence of health system and patient characteristics on expectations and outcome in total hip arthroplasty patients in the Dutch-German border region: protocol for a mixed-methods prospective observational comparative study (hip across).

Introduction: Total hip arthroplasty (THA) is the treatment of choice for end-stage osteoarthritis of the hip. Management of THA differs between countries, and it is hypothesised that this can influence patients' expectations and self-efficacy. Using Chen's intervening mechanism evaluation approach, this study aims to explore how structure of care influences expectations and self-efficacy of patients undergoing THA, and how expectations and self-efficacy in turn influence outcome in terms of perceived physical function and satisfaction.

Methods And Analysis: A mixed-methods study will be conducted in two German and two Dutch hospitals near the Dutch-German border. In the quantitative part, patients will complete questionnaires at three timepoints: preoperatively and at 3 and 6 months postoperatively. Data analysis will include multiple regression analysis and structural equation modelling. In the qualitative part, interviews will be held with patients (preoperatively and 3 months postoperatively) and healthcare providers. Analysis will be performed using structured qualitative content analysis.

Ethics And Dissemination: The study is approved by the Institutional Review Boards of both Carl von Ossietzky University Oldenburg (2021-167) and University Medical Center Groningen (METc 2021/562 and METc 2021/601). The results will be disseminated in the international scientific community via publications and conference presentations.

Trial Registration Number: The study is registered in the German Clinical Trials Registry (DRKS: DRKS00026744).