A statistical shape model of the human female sacrum: An integrative analysis of form

Sacral shape has been investigated in the context of many disciplines, such as anthropology, forensics and in clinical contexts. The female population is of special interest, given the complex interaction between locomotor, thermoregulatory and obstetric demands on the pelvis. However, interpretation of results between current studies is limited by the use of a diverse range of parameters, often offering an oversimplified and fragmented view on sacral shape. We investigated sacral shape in a young adult female population between 18 and 40 years old, using a statistical shape model based on 109 3D CT datasets and principal component analysis. This study provides a comprehensive and visually intuitive view on sacral shape, describing general shape patterns and covariation between different regions of the sacrum. Two dominant shape components were sacral size and sagittal curvature. Both components were associated with specific shape variations in the load-bearing areas of the sacrum, indicating a relationship between shape and function. This study generates hypotheses on sacral shape and its relation to function that warrant further research.