Intra-individual variation in lumbar bone mineral density as a measure of spondylotic deformity in the elderly.

In an attempt at quantitative assessment of spondylotic deformity, the intra-individual variation in L(1)-L(4) bone mineral density (BMD) was calculated, as the standard deviation (SD) and coefficient of variation (CV), obtained by dividing the SD by mean L(1)-L(4) BMD, in 463 subjects. The subjects ranged in age from their second to tenth decades. Dual-energy X-ray absorptiometry (DXA), using the Lunar DPX-L, was employed to assess the BMD. The SD of lumbar (L)BMD increased with advancing age in males, but not in females, whereas the CV of LBMD increased with age in both males and females, along with the radiographically assessed degree of severity of spondylosis deformans. Both the intra-individual SD and CV of L(1)-L(4) BMD showed a highly significant correlation with the radiological degree of severity of spondylosis deformans, and SD, but not CV, showed a strong dependence on the mean L(1)-L(4) BMD on a multiple regression test. Multiple regression test revealed no significant correlation between on body height, weight, fracture, and intra-individual variation in L(1)-L(4) projected area, reflecting compression fracture, one hand and SD or CV of L(1)-L(4) BMD on the other. Intra-individual variation in lumbar bone mineral density, expressed as a coefficient of variation, is suggested as an index of spondylotic deformity.