Risk Factors Associated With Failure to Reach Minimal Clinically Important Difference in Patient-Reported Outcomes Following Anterior Cervical Discectomy and Fusion

Background The minimum clinically importance difference (MCID) represents a threshold for improvements in patient-reported outcomes (PROs) that patients deem important. No previous study has comprehensively examined risk factors for failure to achieve MCID after anterior cervical discectomy and fusion (ACDF) procedures for radiculopathic symptomatology. The purpose of this study is to determine risk factors for failure to reach MCID for Neck Disability Index (NDI), Visual Analog Scale (VAS) neck pain, and VAS arm pain in patients undergoing 1- or 2-level ACDF procedures.

Methods A surgical registry of patients who underwent primary, 1- or 2-level ACDF from 2014 to 2016 was reviewed. Rates of MCID achievement for NDI, VAS neck pain, and VAS arm pain at final follow-up were calculated based on published MCID values. Patients were then categorized into demographic and procedural categories. Bivariate regression was used to test for association of demographic and procedural characteristics with failure to reach MCID for each PRO. The final multivariate model including all demographic and procedural categories as controls was created using backward stepwise regression.

Results Eighty-three, 84, and 77 patients were included in the analysis for VAS neck, VAS arm, and NDI, respectively. Rates of MCID achievement for VAS neck, VAS arm, and NDI were 55.4%, 36.9%, and 76.6%, respectively. On bivariate analysis, patients with Charlson Comorbidity Index (CCI) ≥ 2 were less likely to achieve MCID for NDI than patients with CCI < 2 (P = .025). On multivariate analysis, CCI ≥ 2 (P = .025) was further associated with failure to reach MCID for NDI.

Conclusions The results of this study suggest that the majority of patients do not reach MCID for arm pain. Additionally, higher comorbidity burden as evidenced by higher CCI scores is a negative predictive factor for the achievement of MCID in neck disability following ACDF.

Level of Evidence 3