The pathology and epidemiology of spontaneous diseases and disorders of the spine in the rhesus macaques of Cayo Santiago

grantor: University of TorontoThis dissertation is a cross-sectional research project on degenerative spinal disease, bone mineral density (BMD) and metabolic bone disease in a large skeletal population of rhesus monkeys (CPRC Museum collection), derived from the free-ranging colony of Cayo Santiago, Puerto Rico, a colony of historical and contemporary interest to Anthropology. The effects of demographic variables (age, sex, parity, natal group affiliation) on BMD and spontaneous osteopenia, osteoporosis, vertebral osteophytosis (VO), degenerative disc disease (DDD), vertebral osteoarthritis (VOA) and diffuse idiopathic skeletal hyperostosis (DISH) were studied. The combined frequency of osteopenia and osteoporosis is 12.4% (N = 298). BMD of the last lumbar vertebra was measured using DEXA. Females exhibit an initial increase in BMD with age, with peak bone density occurring around 9.5 years, and remaining constant until 17.2 years, after which there is a steady decline in BMD. Males acquire BMD at a faster rate, and attain a higher peak BMD at an earlier age than do females, at around 7 years, after which BMD remains relatively constant. The BMD values of the monkeys with vertebral wedge fractures are generally higher than those of unfractured osteopenic/osteoporotic individuals, thus supporting the view that BMD alone is not a good predictor of fracture risk. In females, there is a significant increase in BMD of the spine with increasing parity, after controlling for age, up to a parity of about 7 offspring. Vertebrae with VO/DDD have abnormally elevated BMD compared to age/sex- matched controls, even when osteophytes are excluded from the analysis, thus indicating that the trabecular bone was altered by the disease, both quantitatively and qualitatively. VO/DDD and VOA are present in relatively high frequencies, and there is no significant difference between the sexes in frequency or pattern of joint distribution. Thirty-six percent (N = 204) exhibit some degree of VO/DDD, and over 40% (N = 218) exhibit VOA. VO/DDD and VOA increase in severity with advancing age in both sexes. Degenerative changes in vertebral bodies begin around age 8 to 10 years, and all monkeys over 15 years exhibit some degree of VO/DDD or VOA. VO/DDD has a predilection for the thoracic region, and reflects the normal curvatures of the macaque spine. In contrast, VOA is generally distributed throughout the spine. An inverse pattern of VO/DDD and VOA is observed in some joints. These data have implications for our understanding of the human counterparts of these vertebral conditions.Ph.D