• Rochester RP
• Owens EF

• Grostic Technique
• X-Rays

Central to the theory and application of several chiropractic techniques is the assumed utility of x-ray analysis to measure with accuracy the position of the cervical vertebrae with respect to the skull. Yet, the validity of x-ray marking systems as a measure of the actual position of the vertebrae is still a matter of some debate. Early work has shown that upper cervical x-ray analysis needs to be accurate to within 1 degree to provide a useful pre-post measure of misalignment reduction.  Interexaminer reliability studies have shown that x-ray analysis is in most cases repeatable enough to meet this goal. Another source of error in x-ray analysis for misalignment is that introduced by repositioning of the patient for the post adjustment radiographs. Repositioning errors could occur in which the patient has been displaced with respect to the central ray, or rotated.

This article is a presentation of the methods used to take the nasium radiograph in the Grostic Procedure of upper cervical chiropractic care, along with an analysis of the errors that might be introduced by rotational malposition of the patient for the radiograph.

A method was developed and tested for assessing the amount of patient to film rotation present on a nasium film. This method was used to assess the amount of rotation found in 20 of a practitioner's patient x-rays. A mathematical analysis was performed to caleulate the amount of atlas plane line and altas laterality distortion that would be produced by patient to film rotation.   Computer generated simulations of nasium x-rays with known skull to central ray rotations were used to test the algorithm produced and measure the amount of distortion in the atlas plane line and altas laterality induced by rotation.

The average amount of patient to film rotation found in a practitioner's records was 0.56 degrees (STD = 0.55 degrees).  This amount of patient malpositioning was estimated to produce an average of 0.21 degrees artifact in the atlas plane line (STD 0.31degrees).  It was found that the distortion of the plane line depended on the amount of rotational malpositioning present and the tube tilt used to take the nasium film.  Based on the model, the error in the atlas plane line reached a significant value (0.5 degrees) only when the patient to film rotation exceeded 1.5 degrees and the s-line was above 15 degrees. Based on measurement in this study the atlas laterality did not change significantly at 1.75 degrees of image rotation and a tube angle of 25 degrees.  This amount of patient rotation is easily detectable by visual inspection of the nasium film and would probably necessitate retaking of the film in any event.

It was concluded that repositioning the patient for the post radiographic exam would not introduce significant error into the x-ray analysis, as long as proper procedure was followed to minimize rotation of the patient's skull with respect to the central ray.

Author Keywords: chiropractic, x-ray analysis, Grostic Procedure

This abstract is reproduced with the permission of the publisher.