Age is Associated with Level of First-Time Anterior Cervical Discectomy and Fusion: An Ordinal Analysis of Factors Influencing Timing of Cervical Degeneration

Introduction: Symptomatic cervical spondylosis is often treated with anterior cervical decompression and fusion (ACDF). However, few patient-specific factors can predict which cervical level will degenerate and require intervention. Therefore, we present a novel retrospective analysis of pre-procedural factors associated with level of first-time single-level

Methods: We performed a single-institution retrospective analysis of patients who underwent single-level ACDF without prior history of spine surgery. Mann Whitney U-tests and Spearman rank-order correlation were performed for inferential analyses of associations between variables of interest and ACDF level. Adjusted odds-ratios were calculated by proportional-odds logistic regression, with age, sex, body mass index (BMI), current tobacco use, history of neck trauma, preoperative radicular symptoms, and preoperative myelopathic symptoms as covariates.

Results: 141 patients met inclusion criteria, and age demonstrated a significant negative correlation with ACDF level, such that younger patients tended to have ACDF performed at inferior subaxial levels (p=0.0006, rho statistic = -0.31, moderately strong relationship). Patients with pre-operative radicular symptoms and myelopathic symptoms were more likely to have ACDF performed at inferior (p=0.0001) and superior (p < 0.0001) levels, respectively. Patient sex, BMI, current tobacco use, and history of neck trauma were not predictive of ACDF level. When adjusting for the above variables in a proportional-odds ordinal logistic regression model, a one year increase in age conferred a 4% increase in the odds of requiring an ACDF at a given superior level compared to the adjacent inferior level

Conclusion : Age is correlated with level of first-time single level ACDF. This may suggest that individual subaxial levels have unique biomechanical properties that influence rate of degeneration, and additional biomechanical analyses are warranted to investigate this phenomenon.