Ziyad Khaleel MBChB, Presenter: Nothing to Disclose

David Besachio DO, Abstract Co-Author: Nothing to Disclose

Lubdha Mahavir Shah MD, Abstract Co-Author: Nothing to Disclose

Posterior odontoid process inclination has been associated with Chiari 1 malformation in the pediatric population. It has been proposed this finding needs to be addressed during surgical decompression of hindbrain herniation to improve outcome. To date, there is no literature to support the range of normal odontoid angles in adults. The purpose of this study is to estimate the normal adult measurements for odontoid retroflexion, retroversion, and pB-C2 line in order to establish a normative reference database and facilitate future research addressing surgical planning and treatments outcomes of Chiari 1 malformations in the adult population

We performed a retrospective analysis of non-contrasted cervical spine CT scans of 150 consecutive adult patients obtained for indications other than Chiari I malformation. Three neuroradiologists performed the following measurements: odontoid retroflexion, odontoid retroversion, odontoid length, pB-C2 line and clivus-canal angle. Patients who had osseous injury, mass lesion, extensive arthopathy or congenital anomaly of the craniocervical junction were excluded from the analysis

125 out of 150 (83%) patients met the inclusion criteria. Of those, 80 were male and 45 were female with mean age of 52 years (range of 18 - 89). Odontoid retroflexion angle ranged from 70 ̊ to 89 ̊ (mean 79.3 ̊ ±4.9), odontoid retroversion angle ranged from 57 ̊ to 87 ̊ (mean 71.9 ̊ ±5.3) and clivus-canal angle ranged from 140 to 194 ̊ (mean 164.4 ̊ ±10.2). The range and mean of odontoid process length were 17.7- 26.2mm and 21.7mm ±1.5, respectively. The mean of pB-C2 line was 6.5mm ±2.1 with a range of 0 - 11.2mm

Our study demonstrates that the odontoid process is anatomically different than the pediatric counterpart: more posteriorly inclined, increased lordosis, and increased length. Therefore, surgical planning and stratification of treatment outcomes for adult subjects with Chiari 1 malformations should not be based on pediatric odontoid angles measurements. Further research is required to ascertain the significance of odontoid angle measurements on the surgical management in adult patients with Chiari 1 malformations

Generate reference odontoid angles measurements in adults, outline the difference in odontoid angulation and length between adults and children

Khaleel, Z, Besachio, D, Shah, L, Estimation of Odontoid Process Posterior Inclination and Length in the Adult Population.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12037588.html