108 – RADIOGRAPHIC UNION SCALE FOR TIBIAL (R.U.S.T.) FRACTURE HEALING ASSESSMENT: PRELIMINARY VALIDATION

Abstract

Purpose: We aimed to preliminarily validate a newly developed system, the radiographic union scale for tibial (RUST) fracture healing. We hypothesized that RUST would demonstrate better inter-rater reliability than assessment of the number of cortices bridged and correlate with functional outcomes at least as strongly as surgeon’s assessment of cortical bridging.

Method: Three blinded orthopaedic trauma surgeons independently assigned a RUST score and a number of cortices bridged by callus (zero to four) to each set of AP and lateral radiographs at each follow up period. RUST is scored from four (definitely not healed) to 12 (definitely healed) based on the presence or absence of callus and of a visible fracture line at the total of four cortices visible.

Results: For 549 sets of reviewed radiographs, inter-rater reliability for RUST scores were found to be substantially higher than for assessment of the number of cortices bridged (intra-class correlation coefficient=0.84; 95% CI, 0.80–0.87 versus kappa = 0.73; 95% CI, 0.64 – 0.81, respectively). Both methods of assessing radiographic healing were strongly correlated with weight-bearing status (r and ρ> 0.50), moderately correlated with patient-reported functional recovery and the SF-36 Physical Functioning component scores (r and ρ> 0.30), and minimally correlated with HUI Mark II scores, return to work, and the SF-36 Role Physical component and Physical Component Summary scores (r and ρ> 0.10). Neither assessment was correlated with patient-reported pain scores. All correlations were similar for RUST and the number of cortices bridged.

Conclusion: This study provides preliminary evidence that RUST can be used as a valid and reliable alternative assessment of tibial fracture healing.