Calculation of Minimally Clinically Important Difference in VAS, SF-36, and LSA Scores for Hallux Rigidus Correction Via MTP Fusion

Abstract

Category: Bunion; Midfoot/Forefoot; Other Introduction/Purpose: Hallux rigidus is a mobility limiting disease commonly seen in elderly patient populations. Correction via metatarsophalangeal (MTP) fusion has been shown to be a safe and effective means of treatment in these populations relative to younger cohorts. An increasingly important measure of surgical efficacy is the establishment of patient-reported outcomes for achieving meaningful change through a procedure. Calculation of a minimally clinically important difference (MCID) has been established to illuminate these thresholds. The objective of this study was to calculate MCID thresholds for visual analogue pain (VAS), Short Form 26 Health survey (SF-36), and LifeSpace Mobility Assessment (LSA) following first MTP fusion. Methods: A prospective study of all patients undergoing MTP fusion between August 1, 2015 and July 1, 2018 by a single surgeon was conducted following IRB approval. A total of 143 patients were included in the study. Demographics and surgical data were collected from review of the electronic medical record. Patient reported VAS, SF-36, and LSA scores were collected at routine 6- month and 12-month follow-up clinic appointments, as well as preoperatively. This study utilized a distribution-based approach for calculation of MCID for each of the patient reported outcomes. The MCID was defined as 0.5 times the standard deviation of the pre-operative score, 95% bootstrap confidence intervals were creating using the bias corrected and accelerated method. Results: The average age of patients undergoing first MTP fusion was 63.4 years (SD 10.6). Patient demographics were recorded, 25.9% of patients were current or former smokers, 60.8% had clinically managed hypertension, 9.8% had diabetes, and 31.5% carried a diagnosis of osteoarthritis. The average patient had 1.9 (SD 1.1) toes operated on during the procedure, including their MTP fusion. Mean tourniquet time was 65.6 (SD 24.8) minutes and mean operative time was 89.9 (SD 31.4) minutes. Mean (SD): VAS, 4.7 (2.8); LSA, 86.4 (35.1); SF-36 physical component score, 63.00 (19.9); SF-36 component score, 77.4 (19.8). MCID: VAS, 1.4 (95% CI 1.3 to 1.5); LSA, 17.6 (95% CI 14.4 to 21.4); SF-36 physical component score, 9.9 (95% CI 9.1 to 11.0); SF-36 mental component score, 9.8 (95% CI 8.7 to 11.4). Conclusion: This study identifies the MCID for VAS, SF-36, and LSA following first MTP fusion. The MCID of VAS reveals minimal improvements in pain (>1.5) are clinically significant. Both SF-36 physical and mental component scores reveal narrow 10- point differences have clinically significant changes. In contrast, LSA appears to have a relatively wide MCID value for patients undergoing first MTP fusion, highlighting the need for a large increase in mobility for significant improvement.