Roentgenographic measurement of atlas laterality and rotation: a retrospective pre- and post-manipulation study.

Case records (523) were chosen at random from the files of J.F. Grostic, D.C. (deceased) for retrospective determination of the effects of chiropractic adjustments on atlas positioning relative to the occiput and axis. For each patient the recorded degrees of (1) atlas rotation and (2) laterality, both before and soon after spinal manipulative therapy, were extracted from the x-ray reports. Frequency histograms were made of pre- and post-adjustment degrees of laterality and rotation and the relative change of values analyzed statistically. Before manipulation, nine patients had zero atlas rotation and none were zero with respect to laterality. The mean deviation from zero degrees of "misalignment," was 2.75 and 2.63 respectively for rotation and laterality. After manipulation the corresponding values were 1.43 and 140, which is a statistically significant change. The numbers of patients who had zero rotations and laterality after adjustment were 156 and 151 respectively. In 63 patients the post-adjustment values were zero for both parameters. Under the circumstances presented in this retrospective study, these data tend to show that spinal manipulative therapy altered the position of atlas in the postulated direction.