Influence of Axial Rotation on Chiropractic Pelvic Radiographic Analysis

Objective

The aim of the study is to explore associations between axial (y-axis) rotation of the pelvis and pelvic radiographic measurements.

Study design

Descriptive film statistics of an incrementally rotated pelvis and linear regression analysis were performed.

Methods

A phantom pelvic model was incrementally imaged (1° increments) at 40-in source-to-image distance through 10° of axial rotation. Chiropractic line drawing analysis was performed. The chiropractic examiner was blinded to the degree of rotation during the film analysis. Regression analysis was performed between axial rotation and pubic symphysis deviation, sacral width, and innominate and femur head heights. Each measurement corresponds to a chiropractic listing within the Gonstead system.

Results

Regression analysis revealed a strong association between the degree of axial rotation and each response variable: pubic symphysis deviation, sacral width, innominate height, and femur head height. The strongest relationship existed between y-axis rotation and pubic symphysis deviation.

Conclusions

Chiropractic pelvic listings are strongly influenced by positioning of the subject. A few degrees of axial rotation may create apparent misalignments of several millimeters.