OBJECTIVE: To compare two methods of obtaining the anteroposterior (AP) open mouth view.

DESIGN: Radiological evaluation of the occiput-C1/C1-C2 structures, as visualized on radiographs obtained using two different radiographic position set-ups.

SETTING: The Anglo-European College of Chiropractic Clinic.

PATIENTS: A total of 60 patients. Each method used on 30 patients. CRITERIA ASSESSED: Visualization of: (a) occiput-C1 joints, (b) atlantoaxial joints, (c) lateral masses C1 and (d) odontoid process.

RESULTS: The visualization of the occiput-C1 joints was increased almost 100% using method 2. The atlantoaxial joints were seen in 7% more cases using method 2 and the lateral masses were seen in 10% more cases. The only structure seen more consistently using method 1 was the odontoid process, which was seen in 7% more cases using that method.

CONCLUSION: This study shows that there is an easier and more consistent method of obtaining the AP open mouth view than that traditionally used in many institutions.

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