Establishing minimum clinically important difference for patient-reported outcome measures in patients undergoing lateral lumbar interbody fusion

Background: The minimum clinically important difference (MCID) has not been established in lateral lumbar interbody fusion (LLIF). Our study aims to establish MCID for patient-reported outcome measures (PROMs) of physical function and pain for LLIF through anchor-based and distribution-based approaches.

Methods: Patients undergoing LLIF with preoperative and 6-month postoperative Oswestry Disability Index (ODI) scores were identified. PROMs of Patient-Reported Outcome Measurement Information System Physical Function (PROMIS-PF), 12-Item Short Form Physical Component Score (SF-12 PCS), Veterans RAND 12-Item Short Form Physical Component Score (VR-12 PCS), visual analog scale (VAS) back, and VAS leg were collected at preoperative and 6-month postoperative time points. Anchor-based MCID calculations were average change, minimal detectable change, change difference, receiver operating characteristic curve, and cross-sectional analysis using ODI as the anchor. Distribution-based calculations were standard error of measurement, reliable change index, effect size, and 0.5 ∗ ΔSD.

Results: Fifty patients were included. Anchor-based approaches MCID ranges were PROMIS-PF 1.1-9.6, SF-12 PCS 6.4-16.5, VR-12 PCS 5.9-12.9, VAS Back 1.4-4.6, and VAS Leg 1.3-4.3. The area under curve for receiver operating characteristics (ROC) analysis ranged from 0.63 to 0.71. Distribution-based MCID ranges were PROMIS-PF 1.4-4.5, SF-12 PCS 1.9-12.7, VR-12 PCS 2.0-6.6, VAS Back 0.4-1.4, and VAS Leg 0.5-2.0.

Conclusion: MCID thresholds varied widely depending on the calculation method. The closest to (0,1) ROC approach was the most clinically appropriate MCID calculation. The corresponding MCID values for LLIF were PROMIS-PF at 7.8, SF-12 PCS at 6.4, VR-12 PCS at 9.3, VAS Back at 4.6, and VAS Leg at 4.3.