Quantifying the effects of age, gender, degeneration, and adjacent level degeneration on cervical spine range of motion using multivariate analyses

Study Design. Retrospective review and multivariate analysis. Objective. Assess cervical spine segmental range of motion (ROM) with flexion/extension (F/E) radiographs and determine the relation to clinical variables. Summary of Background Data. Previous studies investigated the roles of age and degeneration on cervical ROM with univariate analyses. Multivariate analyses are required to account for multiple factors that may affect ROM and quantify their relative effects. Methods. Radiographs of 195 patients were analyzed, including 133 females and 62 males with ages ranging from 15 to 93 years. Segmental ROM and Kellgren score (KS) of degeneration were assessed for C2-C7. Patient's age and gender were documented. Multivariate analyses were performed for each level. Independent variables evaluated were: (1) KS at the level of interest, (2) KS at the level above, (3) KS at the level below, (4) age, and (5) gender. Significance was defined as P < 0.05. Results. Interobserver reliabilities for assessing KS (intraclass correlation coefficient 0.81) and segmental ROM (intraclass correlation coefficient 0.72) were good to excellent. Age had a significant negative association with ROM at C2-C3, C3-C4, C4-C5, and C5-C6. KS at the level of interest had a significant negative association with ROM at C2-C3, C3-C4, C4-C5, C5-C6, and C6-C7. KS at the inferior segment had a significant positive association with ROM at C2-C3, C3-C4, and C4-C5. Gender had a significant association with ROM only at C2-C3. Conclusion. Age was associated with declining ROM independent of degeneration, amounting to a 5 decrease in subaxial cervical ROM every 10 years. Degeneration was also associated with ROM. For every point increase in KS at a given level, there was an associated 1.2 decrease in ROM at that level, and a 0.8 increase in ROM at the level above. These results provide a framework with which to counsel patients about cervical ROM and a benchmark from which procedure specific changes can be compared.