Part 1: 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

In dental radiography, the vertical atlantoaxial index (VAAI)¹ measures the vertical relationship of the atlas and the axis. Based on prior studies, value less than 0.8 might present a predisposition toward cervical instability. The Powers ratio (PR) is the ratio between the distance of 2 lines: (B–P): from basion to posterior arch of C1 (O–A): from opisthion to the anterior arch of atlas. The normal ratio is 1:1, if the ratio exceeds 1, it indicates atlanto-occipital instability. The basion–axial interval (BAI) is the horizontal distance between basion and posterior dens.⁴ The basion–dens interval (BDI) is the distance between the basion and the tip of the dens.⁴

Objective

The objective of this study was to determine the potential risk for atlantoaxial/atlanto-occipital instability² in patients who underwent cone beam computed tomography (CBCT) imaging of the head. The research was conducted at the Oral and Maxillofacial Radiology clinic of the University of Pennsylvania School of Dental Medicine (Philadelphia, PA).

Materials and Methods

After institutional review board approval, a preliminary study was performed on patients undergoing either preimplantation assessment of jaws or evaluation of atypical facial pain, and measurements were recorded. A total of 50 CBCT volumes were identified for the selected craniocervical cephalometric measurements. Analysis of the CBCT volumes and cephalometry were performed to record various craniocervical measurements and determine the potential risk of atlantoaxial atlanto-occipital instability. The measurements were done by using the midsagittal-view CBCT images. These measurements included BAI, BDI, VAAI, and PR. It was 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 by using the 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 PR³ was utilized in this study to find out the atlantoaxial dissociation (normal PR = 1:1). A ratio over 1 indicates atlanto-occipital dissociation (AOD. BAI is the horizontal distance between basion and the posterior cortex of the axis (normal ≤12 mm). BDI is the distance between the basion and the tip of the dens (normal ≤8.5 mm). Both BAI and BDI are used to diagnose AOD injuries.

https://ift.tt/2GrZpWa