Inter-Rater Reliability of The Modified Radiographic Union Score for Diaphyseal Tibial (mRUST) Fractures with Bone Defects
OBJECTIVES: To evaluate inter-rater reliability of the modified Radiographic Union Score for Tibial (mRUST) fractures among patients with open, diaphyseal tibia fractures with a bone defect treated with intramedullary nails (IMNs), plates, or definitive external fixation (ex-fix). DESIGN: Retrospective cohort study. SETTING: 15 level one civilian trauma centers; 2 military treatment facilities. PATIENTS/PARTICIPANTS: Patients ≥18-years-old with open, diaphyseal tibia fractures with a bone defect ≥1 centimeter surgically treated between 2007 and 2012. INTERVENTION: Three of six orthopaedic traumatologists reviewed and applied mRUST scoring criteria to radiographs from the last clinical visit within 13 months of injury. MAIN OUTCOME MEASUREMENTS: Inter-rater reliability was assessed using Krippendorff's Alpha (KA) statistic; Intraclass correlation coefficient (ICC) is presented for comparison to previous publications. RESULTS: 213 patients met inclusion criteria including 115 IMNs, 24 plates, 29 ex-fixes, and 45 cases that no longer had instrumentation at evaluation. All reviewers agreed on the pattern of scoreable cortices for 90.4% of IMNs, 88.9% of those without instrumentation, 44.8% of rings, and 20.8% of plates. Thirty-one (15%) cases, primarily plates and ex-fixes, did not contribute to KA and ICC estimates because <2 raters scored all cortices. The overall KA for the 85% that could be analyzed was 0.64 (ICC 0.71). For IMNs, plates, ex-fixes, and no instrumentation, KA (ICC) was 0.65 (0.75), 0.88 (0.90), 0.47 (0.62), and 0.48 (0.57), respectively. CONCLUSIONS: In tibia fractures with bone defects, the mRUST appears similarly reliable to prior work in patients treated with IMN but is less reliable in those with plates or ex-fixes, or after removal of instrumentation. LEVEL OF EVIDENCE: Diagnostic, Level I