Bilateral Asymmetry in the Human Pelvis

Area of Science:

• Human anatomy
• Skeletal biology
• Anthropology

Background:

• Asymmetry in the human axial skeleton, unlike the limb skeleton, is understudied.
• Pelvic morphology is influenced by locomotion, obstetrics, and biomechanical loading.
• The impact of these factors on pelvic asymmetry remains unclear.

Purpose of the Study:

• To investigate levels and patterns of pelvic asymmetry.
• To examine directional asymmetry (DA) and absolute asymmetry (AA) in pelvic canal, non-canal pelvis, and femur dimensions.
• To compare asymmetry between sexes and geographic populations.

Main Methods:

• Analysis of 14 bilaterally paired dimensions in female (n=111) and male (n=126) skeletons from nine global samples.
• Calculation of percentage directional asymmetry (%DA) and absolute asymmetry (%AA).
• Statistical comparison of asymmetry measures across sexes, populations, and variables.

Main Results:

• Directional asymmetries were consistently low and lacked patterning across variables.
• %AA was highest in the pelvic canal, especially posterior aspects.
• Few sex or population differences were observed; %AA correlated with coefficients of variation.

Conclusions:

• While directional pelvic asymmetry is low, absolute asymmetry is notable in the pelvic canal.
• High standard deviations in canal variables indicate common, though not directionally consistent, asymmetry.
• Biomechanical loading likely influences pelvic asymmetry, but it probably does not impede obstetric function.