RELIABILITY OF MULTIPLE RADIOLOGICAL UNION SCORING TOOLS IN HUMERAL DIAPHYSEAL FRACTURES: A PILOT STUDY

The primary aim of this study is to establish reliability of five different radiographic assessment tools currently used to evaluate union in humeral shaft fractures. The study will be the first to evaluate interobserver reliability of the radiographic union scale (RUST), modified RUST (mRUST), radiographic union score for HUmeral fractures (RUSHU), radiographic humerus union measurement (RHUM), and the modified radiographic union score (mRUS) in humeral diaphyseal fractures treated with both non-operative and operative management. This study aimed to establish which of the above radiographic union scoring methods has the highest reliability, to further inform future studies evaluating time to union for humeral diaphyseal fractures treated with both non-operative and operative treatment. A total of three orthopedic surgeons reviewed and scored radiographs from 17 patients with humeral diaphyseal fractures treated by non-operative management or open reduction and internal fixation using plate and screw constructs through an anterior or posterior approach. Radiographs were evaluated using the RUST, mRUST, RUSHU, RHUM, and mRUS at the 2- and 4-week follow-up, then at the 4-, 6-, and 12-month follow-up. After a minimum of a 4-week washout period, observers re-scored the radiographic assessment of fracture healing. Interobserver reliability of RUST, mRUST, RUSHU, RHUM and mRUS were determined using intraclass correlation coefficient (ICC). A total of 57 radiographs were reviewed from 17 patients, across the five follow-up timepoints. 52.9% were treated operatively, with either single or dual plate fixation. 47.1% were treated non-operatively, with splint or functional bracing. The intraclass correlation coefficient was computed to assess the agreement between raters in rating RUST, mRUST, mRUS, RUSHU and RHUM for each radiograph. RUST demonstrated poor absolute agreement between the raters, using the two-way random effect models and “single rater” unit, with an ICC of 0.46 (p=0.0001). In contrast, mRUST, mRUS, RUSHU and RHUM demonstrated moderate interrater agreement, with ICC of 0.65, 0.69, 0,54, and 0.61. The mRUS and mRUST scores demonstrated the highest performing agreement, which will help inform the use of the most reliable radiographic assessment tool for identification of fracture healing in the setting of humeral diaphyseal fractures treated non-operatively and operatively with a plate and screw technique. This study supports continued research with a larger cohort of patients and the evaluation of intra-rater reliability. This study will help inform the assessment of fracture healing in humeral shaft fractures treated both operatively and non-operatively. This will be used to inform determination of patients at risk of non-union in the clinical setting, as well as inform impact on functional outcomes in future research endeavours.