Biometrics of vertebral elements: methodological approach to compare ancient and current samples

The recent improvements of biometrical analysis techniques, based on digital technology, increasingly affect natural science studies. The use of imaging analysis delivers more accurate metric measurements with reduced dependency on operator errors and increased accuracy when compared to the use of traditional manual equipment. In anthropological studies modern digital techniques combined with classical manual osteometrical investigations as well as the application of information technology, lead now to a more consistent approach to osteometric surveys. While technological innovation opens new interesting perspectives, e.g. the possibility to compare different images from various sources, on the other hand it raises questions about the significance of the new results in relation to data previously collected with old detection techniques. In Anthropology several studies have been conducted on vertebral column osteometry. Taking into account results from existing studies on ancient Egyptian bones, we deemed it interesting to check the consistency of traditional and digital measurements. A positive result would mean that we have at our disposal several alternative methods, to be applied depending on the environment. We analyzed measurements of the third lumbar vertebra on an ancient Egyptian sample (83 subjects), from the “Marro Collection” belonging to the Anthropology Museum of the University of Turin. Body and neural channel diameters (transverse and antero-posterior) were measured with the traditional method, using the calibre, and with digital imaging analysis. The acquired digital images were processed with a graphics software –ImageJ- providing linear and surface detection thus significantly reducing the margin of error. A comparison between the measurements obtained with the two methods showed a statistically significant difference between manual and digital detection: the manual approach generally tends to underestimate the measured values, if compared to digital image analysis. It is therefore possible that, in osteometric vertebral studies, measurements taken with mixed techniques are incorrect. Moreover, the application of the new digital techniques to the study of the above ancient sample, proved to be of easy implementation both for the equipment involved -easy to find and use- and for the short operating time required. In addition to the reduction of error margins, it will also be possible to compare skeletal ancient samples with modern ones, whose data are already digitally available.