A Computational Framework for Age‐at‐Death Estimation from the Skeleton: Surface and Outline Analysis of 3D Laser Scans of the Adult Pubic Symphysis

Abstract

In forensic anthropology, age-at-death estimation typically requires the macroscopic assessment of the skeletal indicator and its association with a phase or score. High subjectivity and error are the recognized disadvantages of this approach, creating a need for alternative tools that enable the objective and mathematically robust assessment of true chronological age. We describe, here, three fully computational, quantitative shape analysis methods and a combinatory approach that make use of three-dimensional laser scans of the pubic symphysis. We report a novel age-related shape measure, focusing on the changes observed in the ventral margin curvature, and refine two former methods, whose measures capture the flatness of the symphyseal surface. We show how we can decrease age-estimation error and improve prior results by combining these outline and surface measures in two multivariate regression models. The presented models produce objective age-estimates that are comparable to current practices with root-mean-square-errors between 13.7 and 16.5 years.

Testing Reliability of the Computational Age‐At‐Death Estimation Methods between Five Observers Using Three‐Dimensional Image Data of the Pubic Symphysis,

“…The test data used here represent replicate scans of the 12 Suchey–Brooks' (SB) age estimation male casts, taken by the same make of portable, desktop laser scanner, the NextEngine 3D Scanner HD, as in the original papers. Specifically, it is identical in all specifications to the machine used in Slice and Algee‐Hewitt but represents an earlier generation model to that used for the newer scans in Stoyanova et al . For this study, the upper and lower stages of each of the six phases were scanned three times by a single observer ( n = 36).…”

“…The raw SB scans were edited using the scanner's accompanying software, ScanStudio 2.0.2 , such that the symphyseal face is extracted from the surrounding bones. From these isolated faces, x , y , and z coordinates were retrieved and analyzed via the SAH Score method , the TPS/BE method , and the VC method to compute shape measures. More detailed, step‐by‐step procedures on how the shape measures are calculated can be found in Slice and Algee‐Hewitt and Stoyanova et al .…”

“…From these isolated faces, x , y , and z coordinates were retrieved and analyzed via the SAH Score method , the TPS/BE method , and the VC method to compute shape measures. More detailed, step‐by‐step procedures on how the shape measures are calculated can be found in Slice and Algee‐Hewitt and Stoyanova et al . Lastly, these measures were subjected to five sets of regression models to obtain final age estimates for each replicate scan per observer: three simple linear regression model using BE values, VC values, or SAH scores , independently, and two multiple regression models that combine BE values and VC values or the SAH scores and VC values.…”

“…The method development studies by Slice and Algee‐Hewitt and Stoyanova et al have demonstrated how the three sets of shape‐based measures yield accurate and reliable age estimates that are comparable (sometimes even better performing) to those of conventional aging methods, namely the Suchey–Brooks system. Moreover, their ongoing validation studies, based on a large‐scale, mixed sex, and multi‐ethnic sample, continue to show promising, albeit preliminary, results: for example, the shape methods are invariant to issues of asymmetry in the pubic symphysis and can be successfully applied to males and females of various geographic origins and ancestral histories .…”

“…This extension work, which builds upon the method development and validation studies of Slice and Algee‐Hewitt and Stoyanova et al , is necessary to determine the effect of inter‐/intraobserver and experience‐related error on performance—specifically, the potential to produce the most accurate, reliable, and precise age estimates when implementing the fully computational methods as proposed in the original papers.…”