Changes in hip geometry from medieval to modern times

The age and sex adjusted rates of hip fracture are increasing in many countries. Femoral neck geometry, especially femoral neck axis length (FNAL) has increased over the last 40 years and may partially explain this association. Here we extend these observations to femurs dating from the 10th-16th Centuries. Sixty two adult female femora from the medieval archaeological site of Wharram Percy, England were scanned using pencil beam DXA. FNAL and the femoral neck width (FNW) were evaluated. These measurements were compared with age and sex matched femoral scans from randomly selected volunteers in Southampton, England collected in the 1990's using the same densitometer. The use of pencil beam, as opposed to fan beam DXA, ensured that there were no magnification errors in comparing the two sets of results. Identical scan modes and settings were used to acquire both sets of femoral scans. Rigorous theoretical modelling, showed that there may be errors in the results, if femurs from the different eras were not positioned identically. To account for this, a positioning rig for the medieval femora was constructed. This allowed each femur to be positioned with the correct amount of rotation and abduction, ensuring that the femoral neck was parallel to the surface of the scanner. The scans were analysed by one operator (A-C). Measurement of the FNAL and the FNW were assessed using the DXA software, and the ratio FNAL/FNW was calculated. These results were then adjusted for the difference in height between the two groups. FNAL and the FNAL/FNW ratio were found to be significantly greater in modern femurs (p<0.001) compared with medieval femurs after adjustment for height. No significant change in FNW was found.These findings indicate that the proximal femur has undergone a change in shape, as opposed to an overall increase in size. An increase in the FNAL/FNW ratio of modern women, suggests that the femoral neck is now narrower for a given length and this may offer a partial explanation for the increase in fracture incidence in this group