There are indications that clinical studies investigating the surgical treatment of acetabular fractures assess different outcomes. This heterogeneity reduces the comparability of study results and, thus, limits the knowledge generated from research. Core outcome sets (COS) contain a minimum set of outcomes that should be measured in studies investigating a specific disease or injury. A COS for surgically treated acetabular fractures does not yet exist. Therefore, the aim of this study is to identify the reported outcomes in studies investigating the surgical treatment of acetabular fractures. Studies including skeletally mature individuals (≥ 16 years) with isolated acetabular fractures treated surgically were included. Studies with polytrauma patients, pathological fractures, additional pelvic fractures, exclusively non-surgical treatment, or juvenile individuals were excluded. Three databases and two clinical trial registries were searched on 15 November 2022. The identified outcomes were grouped and subsequently categorized according to the Core Outcome Measures in Effectiveness Trials Guidelines. A total of 193 studies were included, which reported a cumulative total of 2581 outcomes. After grouping, 266 unique outcomes were identified. No outcome was examined in all studies. Pain, ability to walk independently, range of motion, quality of reduction, and heterotopic ossification were the most reported unique outcomes and assessed in at least 60

BACKGROUND:Clinical trials investigating acetabular fractures are heterogeneous in their investigated outcomes and their corresponding measurements. Standardization may facilitate comparability and pooling of research results, which would lead to an increase in knowledge about the optimal treatment of acetabular fractures, resulting in long-term evidence-based treatment decisions and improvements in patient care. The aim of this systematic review is to identify the reported outcomes and their measurements from studies on treatments for acetabular fractures to develop a core outcome set which contains the most relevant outcome measures to be included in future studies. METHODS:Studies published in English and German including patients aged 16 years and older, with a surgically treated acetabular fracture, will be included. Studies with nonsurgical treatment, pathologic fractures, polytraumatized patients, and patients younger than 16 years of age will be excluded because other outcomes may be of interest in these cases. Any prospective and retrospective study will be included. Systematic reviews will be excluded, but their included studies will be screened for eligibility. The literature will be searched on MEDLINE, CENTRAL, Web of Science, ClinicalTrials.gov, and WHO ICTRP. Risk of selective reporting of outcomes will be assessed using the Outcome Reporting Bias in Trials classification system. Heterogeneously defined outcomes that measure the same outcome will be grouped and subsequently categorized into outcome domains using the taxonomy of the Core Outcome Measures in Effectiveness Trials Initiative. DISCUSSION:It is expected that a high number of studies will be included, and many outcomes will be identified using different definitions and measurement instruments. A limitation of this systematic review is that only previously investigated outcomes will be detected, thus disregarding potentially relevant outcomes. SYSTEMATIC REVIEW REGISTRATION:PROSPERO CRD42022357644.