Development and preliminary validation of a Function IndeX for Trauma (FIX-IT)

BACKGROUND: Assessing fracture healing in clinical trials is subjective. The new Function IndeX for Trauma (FIX-IT) score provides a simple, standardized approach to assess weight-bearing and pain in patients with lower extremity fractures. We conducted an initial validation of the FIX-IT score. METHODS: We conducted a cross-sectional study involving 50 patients with lower extremity fractures across different stages of healing to evaluate the reliability and preliminary validity of the FIX-IT score. Patients were independently examined by 2 orthopedic surgeons, 1 orthopedic fellow, 2 orthopedic residents and 2 research coordinators. Patients also completed the Short Form-36 version 2 (SF-36v2) questionnaire, and convergent validity was tested with the SF-36v2. RESULTS: For interrater reliability, the intraclass correlation coefficients ranged from 0.637 to 0.915. The overall interrater reliability for the total FIX-IT score was 0.879 (95% confidence interval 0.828-0.921). The correlations between the FIX-IT score and the SF-36 ranged from 0.682 to 0.770 for the physical component summary score, from 0.681 to 0.758 for the physical function subscale, and from 0.677 to 0.786 for the role-physical subscale. CONCLUSION: The FIX-IT score had high interrater agreement across multiple examiners. Moreover, FIX-IT scores correlate with the physical scores of the SF-36. Although additional research is needed to fully validate FIX-IT, our results suggest the potential for FIX-IT to be a reliable adjunctive clinician measure to evaluate healing in lower extremity fractures. LEVEL OF EVIDENCE: Diagnostic Study Level I.