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Sacrum and Coccyx Shape Changes During Pregnancy and After Delivery
Liam C Martin1, Megan R Routzong1, Pamela A Moalli2,3
1Translational Biomechanics Laboratory, Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Benedum Hall, Office 406, 3700 O'Hara Street, Pittsburgh, PA, 15260, USA.
Annals of Biomedical Engineering
|October 12, 2023
Summary
Pregnancy significantly straightens the sacrum and coccyx (tailbone) to aid childbirth. While these bones return towards their original curve postpartum, the change is not fully reversed, indicating lasting skeletal adaptation.
Area of Science:
- Anatomy
- Biomechanics
- Obstetrics
Background:
- The skeletal changes in the female pelvis during pregnancy and childbirth are crucial for accommodating fetal passage.
- While pelvic bone remodeling is known, specific quantitative data on the sacrum and coccyx during pregnancy is limited.
Purpose of the Study:
- To quantitatively assess the remodeling of the sacrum and coccyx during pregnancy and postpartum.
- To compare the shape, length, and curvature of the sacrum and coccyx in nulliparous, pregnant, and parous women.
Main Methods:
- Retrospective collection and segmentation of 90 pelvic MRI scans.
- Midsagittal measurements of sacrum and coccyx length, angles, and curvature using 2D and 3D imaging.
- Statistical shape analysis and MANCOVA to compare dimensional and shape variations.
Main Results:
- Pregnant women exhibited significantly straighter coccyges and sacrum-coccyx complexes compared to nulliparous and parous women.
- Both 2D and 3D analyses confirmed that pregnancy leads to a straighter sacrum and coccyx.
- Postpartum, the sacrum and coccyx showed a tendency to revert to a more curved shape, but not completely.
Conclusions:
- Pregnancy induces significant straightening of the sacrum and coccyx, likely an adaptation for delivery.
- The observed changes in sacrum and coccyx shape demonstrate a degree of skeletal plasticity in response to reproductive demands.
- Postpartum recovery of sacrum and coccyx curvature is incomplete, suggesting potential long-term structural alterations.
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