Neck Disability Index as a Prognostic Factor for Outcomes Following Cervical Disc Replacement

Abstract

Study Design: Retrospective review Objective: We aim to elucidate the potential relationship between neck disability index (NDI) and outcomes following cervical disk replacement (CDR). Summary of Background Data: The use of preoperative disability scores as predictors of outcomes following spine surgery has previously been studied, yet no literature has been published regarding its use in CDR. Methods: A retrospective database of a single orthopedic spine surgeon was searched for single-level CDR patients with preoperative NDI scores, excluding those with trauma, infection, or malignancy. Patients were separated into 2 cohorts by NDI score: Mild-Moderately Disabled (MD) (NDI<50) and Severely Disabled (NDI≥50). Patient-reported outcome measures were collected and compared within and between groups up to 1 year postoperatively and included Patient-reported Outcome Measurement Information System Physical Function, 12-Item Short Form (SF-12) Physical Component Score and Mental Component Score, visual analog scale (VAS) neck and arm pain, and NDI. MCID achievement rates were compared between the groups. Results: All PROM scores significantly improved for both cohorts at one or more postoperative time points compared with preoperative baseline (P≤0.049, all), with the exception of SF-12 Mental Component Score, which only significantly improved in the MD cohort at 2 postoperative points (P≤0.007, both). Between groups, the MD cohort reported significantly superior scores at one or more time points for all studied patient-reported outcome measures (P≤0.047, all). MCID achievement rate did not significantly vary for any outcome at any time between cohorts. Conclusion: Regardless of preoperative disability, both groups reported improvement in physical function, pain, and disability scores following CDR. While not finding significance, patients with severe disability preoperatively consistently demonstrated higher minimal clinically important difference achievement in NDI. These data do not promote the use of NDI as a prognostic factor for outcomes following CDR. Further study with larger patient populations may be useful to clarify this potential relationship.