gms | German Medical Science

Objectives: In the elderly, dens fractures are the most common cervical spine fracture. Older patients are at greater risk of falling than younger patients, since older people suffer from reduced visual activity, decreased reaction time, and blunted reflexes. With age the incidence of osteoarthritis (OA) of the cervical spine increases, possibly restricting motion at any particular cervical spine joint, which may adversely affect the movement and distribution of force across the segment of the spine after a trauma, increasing the likelihood of fracture. In this study, we propose that degeneration of the cervical spine may increase dens fracture risk.

Methods: We performed a retrospective cohort study of adult trauma patients age 55 and older, admitted to our level one trauma center. Of the 1,794 patients who met the inclusion criteria, CT scans were obtained for all 51 patients presenting with a dens fracture and for a random sample of 741 without a dens fracture who served as a control group. OA of the cervical spine, both disk spaces and facet joints, was quantified. For our analysis, we divided the population into two groups comparing patients with and without dens fracture. Differences between groups were assessed using Chi-Square analysis. To rule out confounding effects of age and gender between the groups we performed a sub-group analysis.

Results and Conclusion: Of the 51 patients with a dens fracture, 39 (68.4%) sustained a dens fracture due to a ground level fall, 10 (17.5%) due to a motor vehicle accident, 2 (3.5%) due to falls from greater than standing height, and 6 patients (10.5%) due to other reasons. We found that patients with OA of the atlanto-dens interval (7.8%) were two times more likely to sustain a dens fracture (p<0.05) than patients without OA (3.9%). Interestingly, for the facet joints from C2 to C6 we did find a significant increase (p<0.001 - p=0.024) in the dens fracture risk between patients with and without OA. For the C5/C6 facet joints, we found the lowest increase in the relative dens fracture risk of 1.8 (4.8% patients without OA vs. 8.8% with OA), and for the C3/C4 facet joints we determined the highest increase in the relative dens fracture risk of 4.5 (2.4% without OA vs. 10.8% with OA).

This study demonstrates that in patients 55 and older, OA of the facet joints between C2 and C6 and in the atlanto-dens interval is associated with a significant increase in dens fracture prevalence. OA of the atlanto-dens interval leads to a reduction in the atlantoaxial rotation, which can be further limited by severe degeneration of the facet joints below. As a consequence, a relative low-energy trauma can induce a forced atlantoaxial rotation, resulting in a dens fracture. Better understanding of the relation between the dens fracture and OA of the cervical spine may lead to more effective prevention or treatment of these fractures.