Part 2: CBCT EVALUATION OF ATLANTOAXIAL/ATLANTO-OCCIPITAL JOINTS FOR CERVICAL INSTABILITY RISK ASSESSMENT

Publication date: January 2019

Source: Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology, Volume 127, Issue 1

Author(s): A. MANCIA, S. ROZMAN, S.R. SINGER, M. MUPPARAPU

Background

The VAAI¹ index measures the vertical relationship of the atlas and axis. Based on prior studies, value less than 0.8 might present a predisposition towards cervical instability.

Objective

The objective of this study was to determine the potential risk for atlantoaxial/atlanto-occipital instability² in patients who underwent CBCT imaging of the head at a University-based Maxillofacial Radiology clinic.

Material and Methods

After an IRB approval, a preliminary study was performed on patients undergoing either pre-implant assessment of jaws or reported for evaluation of atypical facial pain and measurements were recorded. A total of 100 CBCT volumes of patients were identified for the selected craniocervical measurements. It is anticipated that these measurements would provide a risk estimate for cervical instability that could potentially result in spinal cord injury. All CBCT volumes were acquired using Carestream CS9300 machine (Carestream, Atlanta, GA)

Results

Based on the preliminary results, the average VAAI measurement was 0.7626, the average BAI was 4.970 mm; the average BDI was 5.043 mm and the average PR was 0.6961.

Discussion

Apart from VAAI, BDI and BAI, the Powers³ ratio was utilized in this study to see atlantoaxial dissociation of subjects (normal Powers ratio= 1:1) A ratio over 1 indicates an Atlanto-Occipital Dissociation (AOD). Basion-axial interval (BAI) is the horizontal distance between basion and the posterior cortex of the axis(normal=<12mm). Basion-dens interval (BDI) is the distance between the basion and the tip of the dens(normal=<8.5mm). Both BAI and BDI are used to diagnose atlanto-occipital dissociation injuries.

Conclusions

Based on the preliminary results of this CBCT study, it was clear that the VAAI, BAI, BDI and Powers ratios are all useful markers for early diagnosis of potential atlanto-occipital dissociation injuries. Since the cervical vertebrae are captured on CBCT taken for other purposes, it is an added advantage to be able to assess AOD using these volumes.

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