I haven’t been around to do a post on a particular pathology for a while but as I was looking through the International Journal of Paleopathology I came across an article looking at osteomalacia. During my pathology course at Uni we touched on this and therefore thought it would be a good article to focus on.
Osteomalacia is a softening of the bones due to a vitamin D deficiency. This is commonly known as rickets in children. It is often identified in juveniles by the characteristic bowing of the long bones. As vitamin D is used for enhancing the intake of calcium and phosphorus it is vital for solid and strong bone growth. A reduced level in these minerals delay and prevent the mineralization of newly formed organic bone matrix resulting in bowing and a weakening of the bones.
Although osteomalacia can be fairly straight forward to identify in children it is much harder in adults. As the long bones have fully developed in adulthood no bowing occurs but a period of vitamin D deficiency can cause a weakening of the bones producing pseudo fractures. These differ from fractures caused by accident and injury as small linear or stress fractures are produced at weakened sites. In Fig. 2 a microscopic view of osteomalacia is presented with arrows highlighting areas where mineralisation has not occurred.
There are two ways in which vitamin D is obtained. The first has been briefly mentioned and occurs by being exposed to UV radiation. The second is by consuming particular food including oily fish and eggs. In modern life these things are easy to come by and therefore the prevalence of osteomalacia is low. However, in the post-medieval period, which the study sample is from, people worked in dark conditions will little exposure to the sun and oily fish or eggs were hard to come by as it was expensive. This resulted in a higher rate of vitamin D deficiency and Osteomalacia during this time.
This article by Ives & Brickley (2014) investigated the skeletal manifestations of Osteomalacia in a large sample dating to the post-medieval period. This includes examining 1181 individuals from 6 post-medieval urban sites plus a collection of 142 burials from a previous study (Brickley et al. 2007) from Birmingham. This gave a total sample of 1323 individuals to examine for the presence of osteomalacia.
When examining the skeletons the spinious process of the scapula appeared to be a common site for pseudo fractures. In total there were 9 cases of this type of fracture, of which 6 also had pseudo fractures in the ribs. Other sites of these fractures also included the pelvic girdle and vertebrae (see fig. 3 for all off the locations of pseudo fractures from this study). Microscopic analysis of some individuals also showed a weakening of the bone and were comparable to the study by Brickley et al. (2007). This method of detection was also used on individuals who did not have any pseudo fractures of the scapula spinious process, but in the femoral head and ribs to confirm the diagnosis of osteomalacia.
From the sample 19 out 1323 individuals were identified as having osteomalacia giving a prevalence rate of 1.43%. When this result is compared to what is known about rickets in children of this period this rate is very low. The authors of this paper provide a few explanations for this. A conservative approach was taken with the study assigning osteomalacia only to those individuals with strong indications of the condition. They also suggest that some adults may have suffered from vitamin D deficiency for a short period and therefore had fully recovered which meant the traits of the condition were not viable on the skeleton. Finally the authors state that between pseudo fractures can be difficult to differentiate from those produced from injury and as they were taking a conservative approach the individual would not have been included.
From this study it appears that you osteomalacia can be accurately identified using characteristic patterns of fractures. It was found that at least 11 individuals from the sample had died before acquiring adequate levels of vitamin D, however in some cases a skeleton may have been so fragile from the deficiency which would complicate an accurate diagnosis. The findings from the study also suggest that individuals who lived in the post-medieval period may have gone through multiple episodes of vitamin D deficiency though these may not have been severe enough to cause a collapse in the bone.
The identification of multiple sites of the skeleton where pseudo-fractures formed provides new information about osteomalacia, and the microscopic analysis confirms this. Although these fractures may not always be present they may be used an indication for the condition and easily appilcable to future study samples.
M. Brickley, S. Mays, R. Ives (2007).l “An investigation of skeletal indicators of vitamin D deficiency in adults: effective markers for interpreting past living conditions and pollution levels in Eighteenth and Nineteenth Century Birmingham, England.” Am. J. Phys. Anthropol., 132: 67–79
Ives, R. and M. Brickley (2014). “New findings in the identification of adult vitamin D deficiency osteomalacia: Results from a large-scale study.” International Journal of Paleopathology 7(0): 45-56.