Comparing the responsiveness of a generic and a musculoskeletal specific functional outcome measure in orthopaedic patients with operative fixation of pelvic ring, acetabulum, or tibia fractures: a comparison between single injury and multiply injured patients

OBJECTIVES: This study compares the responsiveness, or the ability to detect clinical change in a disease, between the generic Short Form-36 (SF-36) and musculoskeletal specific Short Musculoskeletal Functional Assessment (SMFA) patient-reported outcome measures (PROMs) in the orthopaedic trauma population. Stratified analysis was performed to compare whether responsiveness differs between patients with single or multiple orthopaedic injuries. DESIGN: Prospective case series. SETTING: Level 1 Trauma Center. PATIENTS: A total of 659 patients with orthopaedic trauma injuries to the pelvis, acetabulum, or tibia were included for analysis. There were 485 patients with a single isolated injury and 174 patients with multiple orthopaedic injuries. INTERVENTION: None. MAIN OUTCOME MEASUREMENTS: Responsiveness was calculated through the standard response mean (SRM), the proportion meeting a minimal clinically important difference, and floor and ceiling effects. RESULTS: Between baseline and 6 months the magnitude of the SRM for SF-36 was consistently greater than that of SMFA in patients with single (P < .01) and multiple injuries (P < .01). Between 6 and 12 months, there were no differences in SRM across all cohorts. The proportion of patients who achieved minimal clinically important difference was consistently higher when assessed with SF-36 compared with SMFA between baseline and 6 months (81.8% vs 68.1%, P < .0001) and between 6 and 12 months (63.3% vs 55.4%, P = .01). A ceiling effect was only observed at baseline for the SMFA with 16.6% of patients achieving the maximal level of functioning detectable. No floor effects were seen in either PROM. CONCLUSION: This study demonstrates that SF-36 has superior responsiveness versus SMFA in both polytrauma and isolated injury patients and supports the collection of SF-36 as the primary PROM in prospective orthopaedic trauma studies irrespective of whether the patient has an isolated injury or multiple injuries.