Predicting the Behavior of Humeral Shaft Fractures: An Independent Validation Study of the Radiographic Union Score for HUmeral Fractures and Value of Assessing Fracture Mobility.

Abstract

To externally validate the Radiographic Union Score for HUmeral fractures (RUSHU) and to quantify the predictive relationship of fracture motion on physical examination to nonunion. Retrospective cohort study. Single institutional center (University teaching hospital). Ninety-two consecutive patients undergoing nonoperative treatment of a diaphyseal humeral shaft fracture were identified over a 4-year period. The average age of the population was 62 years and 42% of the cohort was men. Clinical examination for fracture stability was routinely performed on patients by the treating physicians. Radiographic assessment of fracture callus (RUSHU score) at 6 weeks was retrospectively determined. Patients were followed up until union. Stability was graded as motion at the fracture site or the humerus moving as a single functional unit. Fractures with a RUSHU score ≤7 were 14 times more likely to proceed to nonunion at 6 months (78% sensitivity, 80% specificity). The time to union was 49 weeks for a RUSHU score of ≤7 versus 16 weeks for a RUSHU score of ≥8. The number of operations needed to avoid one nonunion was 1.7. Fractures mobile at 6 weeks were 6.5 times more likely to proceed to nonunion at 6 months (77% specificity, 67% sensitivity). Mobile fractures had a longer time to union (41 weeks) than nonmobile fractures (17 weeks). The RUSHU score and clinical assessment of fracture mobility are effective and valid tools in identifying patients at risk of developing nonunion of humeral shaft fractures and can enhance early decision making in fracture management. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.