The changes in the number and distributions of vertebral fractures were studied from the long-term observations (average 7 years) of 21 spinal osteoporotic patients. Distribution of wedge fractures was biphasic with peak frequencies at the midthoracic and thoracolumbar spine. Biconcave fractures occurred predominantly in the lumbar spine. These patterns of distribution did not change during the period of observation. The rate of biconcave fracture increased, the rate of wedge fracture decreased, and that of collapse remained the constant in follow-up. The changes in the number of fractures were divided into three types; increasing, plateau, and unchanged type. With the advance of osteoporosis, the increasing type was considered to change into the plateau type, which is probably the terminal stage of spinal osteoporosis. The unchanged type, in contrast, was distinct from the other two types because of increased spinal bone mineral density and decreased urinary calcium, which suggests that spinal osteoporosis is heterogeneous with regard to calcium metabolism.
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