Mineral Analysis of the Fourth Lumbar Vertebra in Health and Renal Failure*

In a previous study of osteosclerosis in chronic renal failure (1), it was noted that this type of bone disease is characteristically seen when renal failure has been present for several years. We wished to confirm that the duration of renal dis-ease is related to the changes in the skeleton and that the radiological appearance is due to an increase in mineral content of the bone and to see whether the calcium and phosphorus are present in the same proportions as are found in healthy individuals. Earlier papers dealing with bone analysis have used weight as the reference standard, but because change in the quantity of normal bone will give unaltered values, volume is i a more meaningful reference (2, 3). As any Range in the mineral content of the skeleton is spread over such a large mass, sam-pling an area where small changes might be de-tected early was necessary. Cancellous trabecu-lar bone is metabolically much more active in the adult than is cortical bone, and the sites of most rapid turnover after cessation of growth are the vertebrae, sternum, and ribs (4-6). For this reason and because osteosclerosis is first visible radiologically in the lumbar spine (1, 7), the fourth lumbar vertebra was chosen for analysis. No previous data are available for comparison with the present series for bone analyses in re-nal disease. However, in a comparable study of the calcium content from a 1-cm slab of the fourth lumbar vertebra in routine autopsies, Caldwell and Collins (3) found values of 1.85 and 1.72 moles per L of calcium in males and females, respec-tively, when cases with osteoporosis were ex-cluded. These values are close to our normal mean of 1.93 moles per L for the whole vertebra, which probably included more compact bone. The vertebral body was removed at the junction of * Submitted for publication October 14, 1963; accepted