Strengths and Limitations
The major limitation of this study was its retrospective nature and cross-sectional design. Due to the retrospective nature of this study some of the subjects were imaged in different positions. Nonpregnant patients were imaged in the supine position while pregnant patients were imaged in a lateral decubitus position (standard for pregnant patients). However, this difference in scanning position would result in less posterior motion for pregnant women because the effect of gravity would be minimized in those patients. Thus, any measurements in orientation change of the coccyx due to pregnancy were likely an underestimation.
Despite this design, which is subject to inter-patient variations in shape confounding the findings, significant straightening of the coccyx and sacrum-coccyx was observed. This suggests that shape changes in the coccyx are a measurable and meaningful remodeling event that occurs in pregnant women. A longitudinal study design may be able to determine if some of the observed statistically insignificant trends in this study are significant or simply explained by patient variation in the sacrum-coccyx shape.