Minimal Clinically Important Difference (MCID) for the Short Musculoskeletal Function Assessment (SMFA) in Severe Lower Extremity Trauma: Pooled Data from 7 Multicenter, Prospective Clinical Trials

Anthony R Carlini; Julie Agel; Michael J Bosse; Katherine P Frey; Elena D Staguhn; Heather A Vallier; William Obremskey; Marc F Swiontkowski; Lisa K Cannada; Paul Tornetta 3rd; Ellen J MacKenzie; Robert V O'Toole; Lisa Reider; Lauren E Allen; Susan C Collins; Renan C Castillo; METRC (Major Extremity Trauma Research Consortium)

doi:10.2106/JBJS.23.01201

Minimal Clinically Important Difference (MCID) for the Short Musculoskeletal Function Assessment (SMFA) in Severe Lower Extremity Trauma: Pooled Data from 7 Multicenter, Prospective Clinical Trials

J Bone Joint Surg Am. 2024 Jul 2. doi: 10.2106/JBJS.23.01201. Online ahead of print.

Authors

Anthony R Carlini¹, Julie Agel², Michael J Bosse³, Katherine P Frey¹, Elena D Staguhn¹, Heather A Vallier⁴, William Obremskey⁵, Marc F Swiontkowski⁶, Lisa K Cannada⁷, Paul Tornetta 3rd⁸, Ellen J MacKenzie¹, Robert V O'Toole⁹, Lisa Reider¹, Lauren E Allen¹, Susan C Collins¹, Renan C Castillo¹; METRC (Major Extremity Trauma Research Consortium)

Affiliations

¹ Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
² Department of Orthopaedics and Sports Medicine, University of Washington Harborview Medical Center, Seattle, Washington.
³ Department of Orthopaedic Surgery, Atrium Health Musculoskeletal Institute, Carolinas Medical Center, Charlotte, North Carolina.
⁴ Department of Orthopaedics, Case Western Reserve University, Cleveland, Ohio.
⁵ Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, Tennessee.
⁶ Department of Orthopedic Surgery, University of Minnesota Medical School, Minneapolis, Minnesota.
⁷ Department of Orthopaedics, Novant Health, University of North Carolina at Charlotte School of Medicine, Charlotte, North Carolina.
⁸ Department of Orthopaedic Surgery, Boston Medical Center, Boston, Massachusetts.
⁹ Department of Orthopaedics, R Adams Cowley Shock Trauma Center, University of Maryland School of Medicine, Baltimore, Maryland.

PMID: 38954643
DOI: 10.2106/JBJS.23.01201

Abstract

Background: The Short Musculoskeletal Function Assessment (SMFA) is a well validated, widely used patient-reported outcome (PRO) measure for orthopaedic patients. Despite its widespread use and acceptance, this measure does not have an agreed upon minimal clinically important difference (MCID). The purpose of the present study was to create distributional MCIDs with use of a large cohort of research participants with severe lower extremity fractures.

Methods: Three distributional approaches were used to calculate MCIDs for the Dysfunction and Bother Indices of the SMFA as well as all its domains: (1) half of the standard deviation (one-half SD), (2) twice the standard error of measurement (2SEM), and (3) minimal detectable change (MDC). In addition to evaluating by patient characteristics and the timing of assessment, we reviewed these calculations across several injury groups likely to affect functional outcomes.

Results: A total of 4,298 SMFA assessments were collected from 3,185 patients who had undergone surgical treatment of traumatic injuries of the lower extremity at 60 Level-I trauma centers across 7 multicenter, prospective clinical studies. Depending on the statistical approach used, the MCID associated with the overall sample ranged from 7.7 to 10.7 for the SMFA Dysfunction Index and from 11.0 to 16.8 for the SMFA Bother Index. For the Dysfunction Index, the variability across the scores was small (<5%) within the sex and age subgroups but was modest (12% to 18%) across subgroups related to assessment timing.

Conclusions: A defensible MCID can be found between 7 and 11 points for the Dysfunction Index and between 11 and 17 points for the Bother Index. The precise choice of MCID may depend on the preferred statistical approach and the population under study. While differences exist between MCID values based on the calculation method, values were consistent across the categories of the various subgroups presented.

Level of evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.