Abstract
INTRODUCTION: This study aimed to rank definitions for measuring poor response one year after TKA, after assessing the face validity and feasibility of existing or newly proposed definitions. MATERIALS AND METHODS: An international, three-round, online modified Delphi study was conducted with sixty-nine panelists from twenty-three countries. Definitions were derived from a literature review or were newly proposed by an expert group. Panelists rated the face validity and feasibility of definitions, and could propose additional new definitions in round 1. Panelists reconsidered their rating of existing definitions, and rated newly suggested definitions (round 2). Definitions with a median score for face validity < 6.5 were removed from the list, and panelists distributed 100 points among the remaining definitions for ranking (round 3). RESULTS: Fifty-one panelists completed all three rounds (response rate 74%), and the prioritized list of definitions in round 3 comprised seventeen definitions. The single-item definition of (dis)satisfaction with the outcome of TKA obtained the highest scores for face validity and feasibility (7.5, and 8.5 respectively), and the definition "No improvement in pain OR daily knee functioning compared to pre-operative status" was the highest prioritized. In general, definitions reflecting change from the perception of patients were higher ranked than definitions requiring both preoperative and postoperative assessment of validated questionnaires. CONCLUSIONS: This study identified seventeen potential definitions of poor response to TKA, offering valuable options for integration into quality assessment investigations. Remarkably, all identified definitions were patient-centered and none were clinician-centered. Single-item questions, capturing change from the patient's viewpoint, appear to be the most practicable format to assess response.