Spondylolysis in prehistoric human remains from Guam and its possible etiology.

This study reports the findings of complete bilateral separation of the neural arch (spondylolysis) in 176 inhumations from the Hyatt Site, Tumon Bay, which is located on the west side of the island of Guam. Skeletons were excavated and analyzed by the Paul H. Rosendahl Inc. (PHRI) team in 1989-1990. The inhumations were associated with the pre-European Latte Period (circa 1,200-1,521 A.D.). This period was characterized by the use of large stone pillars, called latte sets, for the construction of houses. Of the 176 individuals, only 38 adult skeletons had complete spines, and 21% (8/38) of these had evidence of spondylolysis in their lumbar vertebrae, particularly in L-5. The age of the eight individuals range from 30 to 50 years. No children were found with spondylolysis. Of the males 29.4% (5/17) had spondylolysis, as did 14.3% (3/21) of the females. However, the difference between the sexes was not statistically significant. Though the sample is small, it is suggested that the high incidence of lumbar spondylolysis found in these ancient Chamorros was related to lower back traumatic events. The transport of latte stones, involving hyperextension and torque of the lower back, while dragging the stones, probably contributed to the development of microfractures in the spine and subsequent spondylolysis. If this hypothesis is correct, then both males and females appear to have been participants in an organized community labor force. It is predicted that similar frequencies of spondylolysis will be found at other Latte sites.