Medical Student University of Illinois College of Medicine Chicago, Illinois, United States
Introduction: Long-term minimum clinically important difference (MCID) values for patients undergoing only anterior cervical discectomy and fusion (ACDF) have not been established in the literature.
Methods: Patients undergoing primary ACDF with preoperative and 2-year postoperative NDI scores were retrospectively included. Patients with missing preoperative or 2-year NDI scores or with diagnosis of acute fracture/neoplasm/infection were excluded. Patient-reported outcome measures (PROMs) of PROMIS-PF, SF-12 PCS, VR-12 PCS, SF-12 MCS, VAS neck, VAS leg, and NDI were collected at preoperative and 2-year postoperative periods. Demographic and perioperative characteristics were collected. MCID values were calculated using anchor-based methods, with NDI as the anchor, and distribution-based methods. Responders were classified as patients who decreased by one disability classification in the NDI. Anchor-based methods were average change, minimum detectable change (MDC), change difference, and receiver operating characteristic (ROC) curve. Distribution-based methods were standard error of measurement (SEM), receiver change index (RCI), effect size, and 0.5*ΔSD.
Results: Forty patients were included. All patients reported 2-year postoperative improvement, except for SF-12 MCS. Anchor-based methods calculated ranges of 4.1-10.9 for PROMIS-PF, 7.5-15.1 for SF-12 PCS, 6.7-11.2 for VR-12 PCS, 1.5-9.1 for SF-12 MCS, 2.2-4.2 for VAS neck, and 2.4-4.0 for VAS arm. The AUC ranged from 0.64 (PROMIS-PF) to 0.78 (VAS neck). Distribution-based methods calculated ranges of 1.5-4.5 for PROMIS-PF, 1.7-11.5 for SF-12 PCS, 1.9-6.0 for VR-12 PCS, 2.8-18.5 for SF-12 MCS, 0.4-1.3 for VAS neck, and 0.5-1.5 for VAS arm.
Conclusion : MCID values greatly depending on calculation method. The change difference method was the most appropriate MCID calculation in patients undergoing ACDF. This method accounted for clinical improvement in patients and most closely followed previous MCID values. The resulting MCID values were PROMIS-PF at 4.1, SF-12 PCS at 9.5, VR-12 PCS at 8.4, SF-12 MCS at 9.1, VAS neck at 2.8, and VAS arm at 2.7.
