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.