An enhanced computational method for age-at-death estimation based on the pubic symphysis using 3D laser scans and thin plate splines

• NCJ Number: 310970
• Journal: American Journal of Biological Anthropology Volume: 158 Issue: 3 Dated: November 2015 Pages: 431-440
• Author(s): Detelina K. Stoyanova; Bridget F. B. Algee-Hewitt; Dennis E. Slice
• Date Published: July 2015
• Grant Number(s): 2015-DN-BX-K010
• Agencies: NIJ-Sponsored
• Publication Type: Research (Applied/Empirical)
• Award: MODELING SURFACE MORPHOLOGY OF THE PUBIC SYMPHYSIS: Quantitative Methods and Computational Tools for the Objective Estimation of Age-at-Death for Modern Populations

Abstract

Objectives:
The pubic symphysis is frequently used to estimate age-at-death from the adult skeleton. Assessment methods require the visual comparison of the bone morphology against age-informative characteristics that represent a series of phases. Age-at-death is then estimated from the age-range previously associated with the chosen phase. While easily executed, the "morphoscopic" process of feature-scoring and bone-to-phase-matching is known to be subjective. Studies of method and practitioner error demonstrate a need for alternative tools to quantify age-progressive change in the pubic symphysis. This article proposes a more objective, quantitative method that analyzes three-dimensional (3D) surface scans of the pubic symphysis using a thin plate spline algorithm (TPS).

Materials and Methods:
This algorithm models the bending of a flat plane to approximately match the surface of the bone and minimizes the bending energy required for this transformation. Known age-at-death and bending energy were used to construct a linear model to predict age from observed bending energy. This approach is tested with scans from 44 documented white male skeletons and 12 casts.

Results:
The results of the surface analysis show a significant association (regression p-value = 0.0002 and coefficient of determination = 0.2270) between the minimum bending energy and age-at-death, with a root mean square error of ≈19 years.

Discussion:
This TPS method yields estimates comparable to established methods but offers a fully integrated, objective and quantitative framework of analysis and has potential for use in archaeological and forensic casework. 

(Publisher abstract provided.)