Asymmetry of the occipital condyles: a computer-assisted analysis

To ascertain the incidence of asymmetry of the occipital condyles. The a priori hypothesis of symmetry (which is pervasive both in the determination of "subluxation" and in the means chosen for correction) was tested.

Data set design was used with a convenience sample. The condyles were chosen for convenience of visualization from plain film radiographs. The study was retrospectively designed, albeit with prospective implications for analytic investigation.

The research department of Cleveland Chiropractic College, Kansas City, MO.

One hundred fifty-one submentovertex radiographs were examined using a computer-assisted digitizer. The radiographs were randomly obtained from the patient files of two doctors of chiropractic who routinely use this type of radiograph in their patient analysis.

The study was a side-to-side comparison of the condyles, which were subject to neither intervention nor change.

Surface area of left and right condyles for 151 examined pairs.

Analysis with Pearson's correlation coefficient implied a lack of symmetry between condyles (r = .37; p < .0001). The scatterplot revealed values widely dispersed about the regression line, and the standard error of the estimate was 36.7.

The data suggest that the underlying premise of symmetry in chiropractic analysis needs to be reexamined.