Anatomy of the dens and its implications for fracture treatment: an anatomical and radiological study
The most common injuries to the upper cervical spine are fractures of the dens axis. Therefore, the purpose of our study was to answer three questions, namely (1) whether the size of the dens is adequate at all levels to accommodate two screws, (2) what the angle of the posterior tilt of the dens is in a healthy individual and (3) compare the measured variables between the sexes.
The cohort comprised 50 males and 50 females CT examination of the craniocervical junction. We measured the five diameters of the dens and posterior dens angulation angle (PDAA) and screw insertion angle (SIA). The same dimensions were measured in a control group, consisting of 40 non-pathological second cervical vertebrae specimens.
On CT scans, the mean PDAA was 162.7 degrees in males and 160.26 degrees in females; the mean SIA was 62.0 degrees in males and 60.2 degrees in females. On specimens, the mean PDAA was 169.47 degrees in males and 166.95 degrees in females; the mean SIA was 65.42 degrees in males and 64.47 degrees in females. All obtained values were higher in males; regardless of their measuring on either CT scans or specimens, differences between males and females were statistically significant (p < 0.05) in a, c, d and e values.
The values of our measurements correlate with the dimensions identified previously in other studies. Based on our clinical experience and measurements, we presume that two 3.5-mm screws can be inserted into the dens of all adult patients, except for those with pronounced anatomical anomalies. Posterior dens angulation angle is slightly larger than we expected. The dens is significantly larger in males almost in all measurement.
KeywordsC2 anatomy C2 fracture Dens fracture Posterior dens angulation angle Screw insertion angle
This research was supported by Ministry of Health, Czech Republic—conceptual development of research organization, Motol University Hospital, Prague, Czech Republic 00064203—Jan Štulík. Petr Fojtík is grateful to Charles University for support in program of Specific University Research.
Compliance with ethical standards
Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
- 1.Stloukal M (1999) Anthropology: a handbook for the study of the skeleton. National Museum, PragueGoogle Scholar
- 11.Štulík J, Magerl F, Šebesta P, Kryl J, Vyskočil T, Klézl Z, Nesnídal P, Barna M (2012) Cervical spine trauma. Galén Publishing House, PragueGoogle Scholar
- 14.Gehweiler D, Wähnert D, Meier N, Spruit M, Raschke MJ, Richards RG, Noser H, Kamer L (2017) Computational anatomy of the dens axis evaluated by quantitative computed tomography: implications for anterior screw fixation. J Orthop Res 35:2154–2163. https://doi.org/10.1002/jor.23512 CrossRefPubMedGoogle Scholar