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.