Interobserver Reliability of the Modified Radiographic Union Score for Tibial and Femoral Fractures

OBJECTIVES:To evaluate the reliability of the modified Radiographic Union Score for Tibial fractures (mRUST) as a reliable tool for monitoring lower limb fractures (Femur, Tibia) treated with various modalities (Nail, Plate).METHODS:Design: Retrospective analysis.Setting:Single center academic hospital in Germany.Patient Selection Criteria:Adult patients (≥18 years) with extra-articular long bone fractures of the lower extremities treated surgically between January 2005 and April 2022, requiring radiographs in two perpendicular planes and at least one follow-up visit, were included. Exclusion criteria were critical clinical conditions, inability to consent, joint articulation fractures, inadequate documentation, or insufficient imaging quality.Outcome Measures and Comparisons:Six international investigators (five orthopedic surgeons, one radiologist) independently assessed fracture line and callus growth per cortex (mRUST) at individualized follow-up timepoints based on clinical practice. To evaluate inter-rater reliability, intraclass correlation coefficients (ICC) were calculated for the overall dataset, and for subsets of rated images, that were defined based on anatomical location (femur/tibia), treatment type (plate/nail fixation), and treatment combinations across locations.RESULTS:A total of 166 patients (63 femur fractures, 103 tibia fractures; 32.5% female, mean age 43.4 (18-84)) with 1,136 follow-up timepoints were analyzed. Overall inter-rater reliability for mRUST was good (ICC 0.77), consistent across fixation methods (nail/plate fixation, 0.79) and anatomical locations (tibia, 0.78; femur, 0.81). Cortex-specific reliability varied, with highest agreement for the medial cortex (0.70-0.74) and lowest for the posterior cortex (0.65-0.74).CONCLUSIONS:The mRUST (radiographic score) demonstrated reliability for monitoring fracture healing in the femur and tibia, irrespective of fixation method, supporting its use as a generalizable tool across lower limb fractures.