Effect of spinal degenerative changes on volumetric bone mineral density of the central skeleton as measured by quantitative computed tomography

Purpose: To evaluate the impact of degenerative changes due to osteoarthritis ( OA) at the spine on volumetric bone mineral density ( BMD) as measured by volumetric quantitative computed tomography ( vQCT). Material and Methods: Eighty- four elderly women ( mean age 73 +/- 6 years), comprising 33 with vertebral fractures assessed by radiographs and 51 without vertebral fractures, were studied. Trabecular, cortical, and integral BMD were examined at the spine and hip using a helical CT scanner and were compared to dual X- ray absorptiometry ( DXA) measurements at the same sites. OA changes visible on the radiographs were categorized into two grades according to severity. Differences in BMD measures obtained in the two groups of patients defined by OA grade using the described radiologic methods were compared using analysis of variance. Standardized difference ( effect sizes) was also compared between radiologic methods. Results: Spinal trabecular BMD did not differ significantly between OA grade 0 and OA grade 1. Spinal cortical and integral BMD measures showed statistically significant differences, as did the lumbar spine DXA BMD measurement ( 13%, P = 0.02). The QCT measurements at the hip were also higher in OA 1 subjects. Femoral trabecular BMD was 13 - 15% higher in OA grade 1 subjects than in OA grade 0 subjects. The cortical BMD measures in the CT_ TOT_ FEM and CT_ TROCH ROI's were also higher in the OA 1 subjects. The integral QCT BMD measures in the hip showed difference between grades OA 1 and 0. The DXA measurements in the neck and trochanter ROI's showed smaller differences ( 9 and 11%, respectively). There were no statistically significant differences in bone size. Conclusion: There is no evidence supporting that trabecular BMD measurements by QCT are influenced by OA. Instead, degenerative changes have an effect on both cortical and integral QCT, and on DXA at the lumbar spine and the hip. For subjects with established OA, assessment of BMD by volumetric QCT may be suggested.