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.

Abstract

Objective: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.Design:Prospective cohort study.Setting:Level 1 trauma center.Patients/Participants: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.Main outcome measurements: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.Results: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 (P < .001), but not between 6 and 12 months (P = .29). Similarly, the proportion of patients achieving MCID in SF-36 PCS was significantly greater than the proportion achieving MCID in SMFA DI between baseline and 6 months (84.6% vs 69.8%, P < .001), and between 6 and 12 months (48.5% vs 35.7%, P = .01). There were no ceiling or floor effects found for SF-36 PCS at any time intervals. However, 16.1% of patients achieved the highest level of functioning detectable by the SMFA DI at baseline, along with smaller ceiling effects at 6 months (1.3%) and 12 months (3.3%).Conclusions:SF-36 PCS is a more responsive measure of functional outcome than the SFMA DI over the first year of recovery in patients who sustain a pelvic ring disruption or acetabular fracture. This superiority was found in using the SRM, proportion of patients meeting MCID, and ceiling effects. Furthermore, the SF-36 PCS correlated with the more disease-specific SMFA DI.Level of evidence:Prognostic Level II.