[Separate measurement of radial trabecular and cortical bone mineral density by peripheral quantitative computed...

Degenerative joint disease and osteoporosis, both of which tend to increase with advance in age, were thought to be essentially different mainly because of the artifactually high lumbar spine bone mineral density (BMD) in the former unlike osteoporosis characterized by persistent decrease of BMD. To clarify the relationship between these two diseases, three-dimensional BMD of the trabecular and cortical bone was measured separately in an area of the radius relatively free of degenerative changes by peripheral computed tomography (pQCT). In addition to radiological assessment of spondylosis deformans, quantification of vertebral deformity was attempted by calculation of standard deviation, coefficient of variation, difference between maximum and minimum density divided by the mean of L1-L4. With advance in age and progress of spondylosis deformans, the standard deviation, coefficient of variation difference between the maximum and minimum density and this difference divided by the mean of L1-L4 increased, but radial trabecular bone density, cortcal density and relative cortical volume decreased, suggesting parallel advance of degenerative joint disease and osteoporosis. Sodium etidronate, an antiresorber commonly used in the treatment of osteoporosis, increased mean lumbar spine BMD and markedly decreased the standard deviation, coefficient of variation, difference between the maximum and minimum density and this difference divided by the mean of L1 and L2 but maintained maximum BMD constant, decreasing vertebral deformity due to spondylosis deformans. It is conceivable that calcium release from bone on increased resorption leads to osteoporosis, and calcium entrance into cartilage, causing its hardening, disappearance and degeneration, direct contact between bones, osteoarthritis and subsequent deformity in a single sequence of events.