Biomechanical analysis by chiropractic radiography: Part III. Lack of effect of projectional distortion on Gonstead vertebral endplate lines.

Projectional distortion is known to produce artifactual dysrelationships between images of osseous segments on X-ray films. According to Gonstead, lines constructed parallel to the adjacent vertebral endplates will converge if a lateral flexion malposition is present and will be parallel if no such subluxation exists. To test the accuracy of these lines, we mounted two vertebrae on supports so that the superior vertebra could be laterally flexed by a known amount upon the fixed inferior vertebra.

Biomechanical analysis by chiropractic radiography: Part II. Effects of X-ray projectional distortion on apparent vertebral rotation.

Projectional distortion in an X-ray image can produce artifacts that cause error in the measurement of vertebral rotation. By means of a stereotaxic positioning device, the effect of varying object-film distance, vertical and horizontal off-centering, rotation, and lateral flexion on the amount of distortion in the image of a third lumbar vertebra was determined. Mathematical analysis of the results revealed that projectional distortion due to vertical off-centering does not affect the apparent rotation of the vertebra measurably; that there is a linear relationship between apparent vertebral rotation and horizontal off-centering; for the object-film distances of 35.

Biomechanical analysis by chiropractic radiography: Part I. A simple method for determining X-ray projectional distortion.

Projectional distortion is known to produce artifactual disrelationships between the images of osseous segments on X-ray film. Apparatus and methods were developed to measure the effect of projectional distortion on a human third lumbar vertebra. The procedures for mathematical analysis of such distortion are outlined, and the results of studies to determine the accuracy of the procedure are presented.