Which general functional outcome measure does a better job of capturing change in clinical status in pelvic and acetabular fracture patients? An analysis of responsiveness over the first year of recovery

To compare the responsiveness of the Short Form-36 (SF-36) physical component score (PCS) to the Short Musculoskeletal Function Assessment (SMFA) dysfunction index (DI) in pelvic and acetabular fracture patients over multiple time points in the first year of recovery. Prospective cohort study. Level 1 trauma center. Four hundred seventy-three patients with surgically treated pelvic and acetabular fractures (Orthopaedic Trauma Association B or C-type pelvic ring disruption or acetabular fracture) were enrolled into the center's prospective orthopaedic trauma database between January 2005 and February 2015. Functional outcome data were collected at baseline, 6 months, and 12 months. Evaluation was performed using the SF-36 Survey and Short Musculoskeletal Function Assessment. Responsiveness was assessed by calculating the standard response mean (SRM), the minimal clinically important difference (MCID), and floor and ceiling effects. Three hundred five patients had complete data for both outcome scores. SF-36 PCS and SMFA DI scores showed strong correlation for all time intervals (r = -0.55 at baseline, r = -0.78 at 6 months, and r = -0.85 at 12 months). The SRM of the SF-36 PCS was greater in magnitude than the SRM of SMFA DI at all time points; this was statistically significant between baseline and 6 months (