Magyar László szerk.: Orvostörténeti közlemények 133-140. (Budapest, 1991-1992)

KISEBB KÖZLEMÉNYEK — STUDIES AND LECTURES - Raptis, George: Paleopathological Investigation of Osteoporosis with Dual Energy X-ray Absorptiometry

DISCUSSION Osteopenia in ancient populations has been assessed in the past either by morphological examination [6,7, 13, 18, 23, 33, 36, 37, 52, 53] or by radiological and, more recently, absorptiometric techniques

—with the older methods of single and dual photon scans

—[8, 24, 32, 34, 39, 51], producing sometimes but not always acceptable results. Nevertheless, a definitive method to become a widely accepted standard is still lacking. Determination of osteoporotic status of an ancient population irrespective of principle of determination involves addressing quite many methodological questions. Careful statistical and epidemiological evaluation of any results originating from such studies has to be employed in order to compensate for a host of confounding factors. First of all, the study of ancient bony remains, conveniently situated in a cemetery, is intrinsically of crosssectional nature. In effect, any investigation based on such material is deprived of the longitudinal component of bone mass change in each individual person [41] This fact poses a very serious epidemiological limitation which cannot be fully overcome. In addition, a sample taken from an ancient cemetery is almost certain to be biased in respect to cause of death, age at death, gender, and socioeconomic status of the burried persons. All of the above factors contribute in forming a sample whose reference population is not necessarily that conceived by the conventional historical and archeological concepts of the specific period. On the other hand, a re-evaluation of established facts regarding an historical period will almost certainly occur if thorough paleopathological analysis is applied to any cemetery population of that period. Secondly, keeping in mind the above limitation, we should be very cautious when combining data from different archeological sites of similar time-periods. Not only must the samples be homogenous in the historical and cultural aspect, but also in their stratification with regard to gender, age, and of course skeletal site. The ethnic composition has also to be controlled for. By accounting for these sources of potential bias we can draw sounder conclusions concerning individual parameters (age, sex, race) and safely combine the results of carefully planned and completed studies of approximately the same archeological dating. The necessity of carrying out a dietary evaluation of the individuals under study is more than obvious. Thirdly, duration of burial and conditions of soil (apart from customary rituals as burning of the dead body) may have a common but unfortunately variable effect on post mortem reduction of bone mineral content [9, 11, 28], This principle has been applied without particular success to the dating of bony remains [8, 19]. The reported failure to provide reproducible results is explained by the diverse variation introduced. On the contrary, this process does not substantially interfere with the measurement of osteopenia as all specimens of a certain site are subject to the same degree of demineralization [9[. Within sample comparisons are therefore permissible, while it has yet to be determined if this is possible when conditions are nearly identical. Another way of avoiding this pitfall is to use an index of relative bone mineral content by relating changes of bone density to other measures of the post-mortem bone age [18]. Unless the effect of geographical site and duration of burial is quantitated no ethnic, demographical or ecological comparisons can be unconditionally valid. Last but not least crucial, a reliable method giving reproducible results has to be at hand when studing an ancient skeletal population for minimizing operator-induced error [31]. The latter is of paramount importance since an international standard is indispensable if results of any scientific value are desirable. As this study was undertaken in order to validate the latest development in bone absorptiometry in paleopathological investigation the following statements summarize the results. A good reproducibility was determined by the applied experimental protocol, while operator-induced variation was reduced to a minimum owing to computer standardization. The absorptiometric data correlated satisfactorily with the determined calcium content. Concluding, this preliminary investigation indicates that dual energy X-ray absorptiometry offers a reliable method of measuring the bone mineral content of the specific parts of ancient bones examined.