Establishing Minimum Clinically Important Difference Thresholds for Physical Function and Pain in Patients Undergoing Anterior Lumbar Interbody Fusion.

OBJECTIVE: To establish minimum clinically important difference (MCID) in anterior lumbar interbody fusion (ALIF) for the physical function PROMs Patient-Reported Outcomes Measurement Information System Physical Function (PROMIS-PF), 12-Item Short Form (SF-12) Physical Component Score (PCS), and Veterans RAND-12 (VR-12) PCS and pain PROMs Visual Analog Scale (VAS) Back and VAS Leg through anchor- and distribution-based calculations.

METHODS: Patients undergoing ALIF with preoperative and 6-month Oswestry Disability Index (ODI) were included. Using ODI as the anchor, anchor-based calculation methods were the average change, minimum detectable change (MDC), and receiver operating characteristic (ROC) curve methods. Distribution-based methods were the standard error of measurement (SEM), receiver change index (RCI), effect size, and 0.5ΔSD.

RESULTS: 51 patients were identified. Anchor-based methods ranged from 2.9-11.5 for PROMIS-PF, 8.2-13.6 for SF-12 PCS, 7.8-16.8 for VR-12 PCS, 0.5-3.9 for VAS Back, and 1.0-3.4 for VAS Leg. AUC ranged from 0.59 (VAS Back) to 0.78 (VR-12 PCS). Distribution-based methods ranged from 1.0-4.2 for PROMIS-PF, 1.8-12.2 for SF-12 PCS, 1.9-6.2 for VR-12 PCS, 0.4-1.6 for VAS Back, and 0.5-1.7 for VAS Leg.

CONCLUSION: The MCID values greatly relied on the calculation method. The minimum detectable change method was selected as the most appropriate MCID calculation method. The MCID values that may be utilized for ALIF patients are 7.3 for PROMIS-PF, 8.2 for SF-12 PCS, 7.8 for VR-12 PCS, 3.2 for VAS Back, and 2.2 for VAS Leg.