Assessment of posterior odontoid tilt: Think scoliosis.

Objective: The odontoid process is an important anatomical structure providing a balance of mobility and stability at the craniocervical junction, with structural and biomechanical associations, and morphology that can be quantified with various measurements. The odontoid tilt angle is a measurement that must be accurately performed and can guide further investigations.

Materials and methods: Retrospective analysis of 100 cervical spinal magnetic resonance imaging was performed on patients investigated for neck pain, with a known history of scoliosis, and compared with 50 control patients. Posterior odontoid tilt and Cobb angles were measured by a musculoskeletal radiology fellow and a fellowship-trained musculoskeletal radiologist with more than 10 years of experience, with descriptive statistics then performed on the measurements.

Results: One hundred and thirty-two patients met the inclusion criteria, across both the scoliosis and control groups. 9 (18%) patients from the control group demonstrated posterior odontoid tilt, compared with 35 (43%) of patients in the scoliosis group. A range of scoliosis curve morphologies were demonstrated: 62 thoracolumbar, 10 thoracic, 9 lumbar, and 1 cervicothoracic, with average Cobb angles of 24.3°, 26.9°, 23.4, and 54°, respectively. There was good interobserver agreement for both measurements and a statistically significant difference in the posterior odontoid tilt measurements between groups (99% confidence interval, P = 0.0064).

Conclusion: We recommend opportunistically assessing for the posterior odontoid tilt (Leaning odontoid tower of BRUMES (Botchu; Raja Rasul; Uldin; Morgan;Elias; Sonal, Shashank, Shirodkar). In cases with a posterior tilt angle >5°, we recommend whole spine imaging to assess for scoliosis in the thoracolumbar spine.