The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Investigation into human sacral fusion with regard to skeletal age


1Department of Anthropology, University of Tennessee, 2Department of Anatomy, Lincoln Memorial University DeBusk College of Osteopathic Medicine, 3Department of Anthropology, Michigan State University

Saturday All day, Plaza Level Add to calendar

This presentation evaluates age-at-fusion of sacral segments in late 19th and early 20th century Americans. Langley-Shirley and Jantz (2010) demonstrated shifts in the timing of epiphyseal union of the medial clavicle in modern Americans as a result of secular changes in skeletal maturation. These changes should manifest in other maturation indicators. This project is the first portion of a two-part study investigating secular change in the fusion timing of sacral segments.

The sample consists of 177 European American and African American individuals aged 4-35 years from the Hamann-Todd Collection. Sacral segments were scored as (1) unfused (no bony bridging), (2) fusing (bony bridging between sacral bodies) or (3) fused (obliteration of epiphyseal line). Transition analysis using a cumulative probit model was conducted with Nphases2 (Konigsberg 2003). This method calculates a maximum likelihood estimate of the age-at-transition from one phase to the next (Boldson et al. 2002).

Results indicate that fusion between the first and second sacral segments (S1-S2) occurs significantly later than between S2-S3, S3-S4, and S4-S5. The transition from unfused to fusing in S1-S2 occurs at age 15 in females and 17 in males; the transition from fusing to fused occurs at 21 in females and 22 in males. The transition from unfused to fusing in the remaining sacral segments occurs around puberty in both sexes (9-12 years); the transition from fusing to fused occurs 3-5 years later. This presentation will compare these results to previous studies and discuss the utility of sacral segments as an age indicator in young individuals.

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