Improving agreement in assessing subtrochanteric fracture healing among orthopedic surgeons using the Radiographic Union Score for Hip (RUSH)

Background: Prompt identification of fracture healing is crucial for medical decision-making and clinical research. This study aims to assess the effectiveness of the Radiographic Union Score for Hip (RUSH) in subtrochanteric fractures and determine the optimal scoring threshold for fracture healing.

Methods: We obtained 94 sets of X-ray films from the postoperative follow-up of 35 patients who underwent intramedullary nail fixation for subtrochanteric fractures. Six orthopedic trauma surgeons evaluated the imaging data and determined fracture healing based on subjective judgment. They then scored the X-ray images using the RUSH form. After four weeks, the same observers re-evaluated 47 randomly selected sets of radiographs. Subsequently, the observers and study designer conducted a consensus meeting where they agreed on whether the fractures had healed. We used Fleiss kappa to evaluate agreement among observers based on subjective impressions, and the intraclass correlation coefficient assessed RUSH score consistency. Regression analysis examined the relationship between scores and fracture healing consensus using a receiver operator characteristic (ROC) curve.

Results: Based on overall impressions, the agreement level among orthopedic trauma surgeons for determining the healing status of subtrochanteric fractures was moderate (Kappa = 0.564, 95% CI: 0.511-0.616). However, utilizing the RUSH scoring system can improve the consistency to a substantial level of agreement (ICC = 0.748, 95% CI: 0.663-0.817). Regarding intraobserver reliability, there were significant differences among orthopedic trauma surgeons in judging fracture healing based on overall impressions. However, using the RUSH scoring form, the attending group achieved better intraobserver consistency than the resident group. Regression analysis and ROC curve analysis revealed a strong correlation between the RUSH total score, cortical bone score, cancellous bone score, and consensus on fracture healing. The AUC values are 0.769 (95% CI: 0.670-0.868), 0.779 (95% CI: 0.681-0.876), and 0.771 (95% CI: 0.674-0.867), respectively.

Conclusions: Our study highlights the effectiveness of the RUSH scoring system in enhancing interobserver agreement and intraobserver consistency when evaluating subtrochanteric fracture healing in orthopedic trauma surgeons. We propose setting 21 points as the threshold for the simplified RUSH scoring system to determine fracture healing. This system includes only eight items related to cortical bone, with a total score of 24 points.