Sacral preauricular extensions, notches, and corresponding iliac changes: New terms and the proposal of a recording system

Specific changes at the ventrosuperior margin (apex) of the ala ossis sacri—an extension or a notch and respective corresponding structures at the iliac auricular facet—were noted in female skeletons. We suggest terming them sacral preauricular extension (SPE) and sacral preauricular notch (SPN) and propose a recording system. We analysed pelvic remains from Bronze Age female and male individuals for comparison from three different sites in Austria in the course of the ongoing European Research Council‐funded project The Value of Mothers to Society. In total, 52 sacral remains from the right side and 34 from the left of female individuals, as well as 30 sacral remains from the right and 24 from the left side of male individuals, were recorded. Commonly addressed pelvic features and the newly described changes were systematically analysed. The sacral preauricular extension occurred uni‐ and, in some cases, bilaterally in females of all ages, always at the level of the terminal line, the sacral preauricular notch only unilaterally. Corresponding structures at the ilium occurred in 66.7% and 80% of the affected individuals (right/left side, respectively). In total, a sacral preauricular extension was found on the right side in 13.5% and on the left side in 14.7% of the Bronze Age females, and 9.6% was affected by a notch. The observed changes were not found in males. We argue that the observed changes stand in a causal relationship with pregnancy and birth events. The hormonally induced ligament laxening during pregnancies causes an increased movement in the sacroiliac joint. Postural changes encouraged by weight gain can cause balance shifts that may lead to the observed bony extensions at the sacroiliac apex. The sacral preauricular notch may be related to birthing events at an early age. We present a nomenclature, a detailed description of the morphological modifications, and propose a recording system.