Dual Role of Neck Disability Index in the Assessment of Quality of Life in Cervical Spine Patients.

Introduction: The Neck Disability Index (NDI) is a well-established measure for patients with cervical myelopathy, radiculopathy, or myeloradiculopathy. Few studies have examined the relationship between NDI and mental health outcomes after anterior cervical diskectomy and fusion (ACDF). Our study sets out to determine the possible correlations between NDI and mental health outcome measures after ACDF.

Methods: A prospectively maintained surgical registry was retrospectively reviewed for elective ACDF procedures from December 2013 to December 2019. Demographic and perioperative characteristics were collected. Primary outcomes of interest were NDI, 12-Item Short Form Mental Component Summary (SF-12 MCS), and Patient Health Questionnaire-9 (PHQ-9). Outcomes were collected preoperatively and postoperatively (6 weeks, 12 weeks, 6 months, 1 year, and 2 years). Postoperative improvement for all outcomes was evaluated using a paired Student t-test. Correlations between NDI and mental health outcomes were evaluated using the Pearson correlation coefficient. Strength of association was determined using the following criteria: weak (0.1 ≤ |r| < 0.3), moderate (0.3 ≤ |r| < 0.5), and strong (|r| ≥ 0.5).

Results: A total of 225 patients were included in this study. Most of the patients underwent a single-level procedure and had a spinal pathology of herniated nucleus pulposus. NDI demonstrated significant improvements through 2 years compared with preoperative values (all P < 0.001). Similarly, SF-12 MCS and PHQ-9 significantly improved through 1-year postoperatively (all P ≤ 0.010) but was not maintained at 2 years (P = 0.835; P = 0.128). NDI demonstrated a significant but moderate correlation with SF-12 MCS at the preoperative time point, but a strong correlation was observed at all postoperative time points (all P ≤ 0.001). A significant and strong correlation between NDI and PHQ-9 was demonstrated at all time points (all P ≤ 0.002).

Discussion: NDI demonstrated notable and strong correlations with mental health outcome measures at all postoperative time points. NDI is an effective measure to assess neck disability but may also help capture changes to mental health symptoms after ACDF.