Testing the discrepancy between physical and virtual linear measurements

Virtual calculations of bone morphology are increasingly becoming the golden standard in anthropological sciences, gradually replacing the performance of direct physical measurements. Nevertheless, the potential discrepancy between the two approaches is rarely addressed. Here, we address this question focusing on the second thoracic vertebrae of 24 well-preserved individuals from the skeletal collection of the Forensic Anthropology Unit of Medical School at the National and Kapodistrian University of Athens, Greece. Following traditional osteometric methods, a series of measurements were taken on the vertebral body, both directly (using a digital caliper) as well as on high-resolution 3D surface models. The arithmetic results of the two measuring techniques were then compared through a number of statistical analyses evaluating inter-method precision (Bland-Altman plots, TEM, %TEM and Wilcoxon test). Moreover, the values obtained from each approach were used to develop discriminant function equations for sex determination to evaluate if both approaches provide the same assessment. Both intraobserver and interobserver tests were performed. Although most statistical analyses showed a significant difference between the two measuring techniques, the discriminant function equations for sex determination provided the same assessment. Overall, the results of this experiment support the use of virtual linear measurements, also suggesting that a refinement of digital measuring protocols could improve their level of agreement with traditional direct osteometry.