The effects of bite line deviation on lateral cervical radiographs when upper cervical joint dysfunction exists: a pilot study.

PURPOSE: To demonstrate the impact of inconsistent bite line positioning during pre and post lateral cervical radiographic examinations and to suggest certain additional imaging studies if the bite line cannot be consistently maintained.

METHODS

Radiographic measurements of relative flexion and extension in the atlantal-occipital (AO) and atlantal-axial (AA) joints were taken from neutral lateral cervical and cervical flexion and extension radiographs of 20 subjects.

RESULTS

The average relative AO flexion was -0.9 degrees and 12.0 degrees of extension, while the average relative AA flexion and extension values were 8.5 degrees and 2.8 degrees, respectively. In addition, 12 (60%) of the 20 subjects exhibited paradoxical motion at the AO joint during cervical flexion. Of these 12 subjects, 10 also displayed excessive relative AO extension (beyond 7.5 degrees ).

CONCLUSIONS

If a bite line deviation exists in pre and post lateral cervical radiographic examinations, dynamic cervical flexion and extension radiographs should be taken to calculate the maximum tolerances in the upper cervical spinal joints. If these tolerances are exceeded, the measurement of the cervical lordosis from the back of the second cervical vertebra and seventh cervical vertebra may be altered, thus incorporating the possibility of a 20.3% measurement error on the post lateral cervical radiograph.