Summary

The goal of this investigation is to calculate procedure-specific minimum clinically important difference (MCID) values for common lower-extremity procedures to provide physicians a benchmark to evaluate patient-reported outcomes.

Abstract

Introduction

Electronically collected patient-reported outcomes (PROs) offer physicians a powerful tool to track individual patient improvement and evaluate treatment techniques. Calculating a Minimum Clinically Important Difference (MCID) for specific PROs such as PROMIS Physical Function or Pain Interference would allow physicians to quickly compare individual patient scores with a benchmark. Recent studies have calculated MCID values for the general patient population, but these MCID values may not be representative of the patient experience in unique injuries such as an Achilles rupture or fracture reduction that often result in a large change in physical function post-operatively.

Purpose

The goal of this investigation is to calculate procedure-specific MCID values for common lower-extremity procedures to provide physicians a benchmark to evaluate patient-reported outcomes.

Methods

Following IRB approval, the PROs of all patients who received lower extremity surgery at a single institution were evaluated. Current Procedural Terminology (CPT) codes from common procedures were used to create specific patient cohorts: ankle fractures, foot fractures, toe or bunion corrections, arthritis or reconstruction-related procedures, ankle ligament or peroneal tendon stabilization-related procedures, ankle arthroscopy, and Achilles rupture repairs. We specifically assessed PROMIS Physical Function (PF) Computer Adaptive Test (CAT) and PROMIS Pain Interference (PI) CAT scores. We calculated MCID scores using an anchor-based method applying the Single Assessment Numeric Evaluation for Foot and Ankle (FA SANE). Differences within groups were evaluated non-parametrically using a Wilcoxon Signed Rank Test.

Results

In total, 1,537 patients enrolled for a lower extremity surgery with both baseline and follow-up outcomes were included for analysis (average follow-up 224 days). While the general population had a change in PF of 4.9 following surgery (p < 0.0001), the average change between procedure categories varies widely: while patients receiving a toe or bunion correction only report an average improvement in PF from 42.5 to 44.1 (p = 0.07), Achilles rupture patients report improvement of over one standard deviation (PF 33.6 to 43.6, P < 0.0001). We found that the MCID for patients who received a toe or bunion correction is 1.0 and 2.7 for PROMIS PF and PI, respectively, while the MCID for patients who had an Achilles repair is 4.1 and 5.1, respectively. The MCID is also above 5 for PROMIS PF and PI for patients treated for foot or ankle fractures.

Conclusion

We found that changes in PROMIS physical function and pain interference are not uniform among lower extremity injuries following surgery. Sports or trauma-related injuries such as an Achilles rupture or ankle fracture often result in a lower baseline and higher change in PRO. Accordingly, it is important to gauge patient improvement against MCID values specific to the procedure category. By applying FA SANE as an anchor-based method comparing PROMIS PI and PF to perceived improvement by patients, we provide benchmark values for common lower-extremity injuries that may help physicians more accurately assess clinically meaningful improvement of individual patients.