Reduced bone mineral density (BMD) has been reported following allogeneic stem cell transplantation (alloSCT) but the effects of autologous SCT (autoSCT) are less well characterized. We performed a ...prospective study of BMD changes and its determinants in 44 SCT recipients (38 auto and six allo; 30 peripheral blood SCT and 14 bone marrow transplantation). Serial measurements of BMD at the lumbar spine and femoral neck were performed at baseline and at 3, 6, 12 and 24 months, and spinal radiographs were performed at baseline and 12 months. Mean baseline BMD values at the femoral neck and spine were within normal limits. At 3 months, there was a significant decline of BMD at the femoral neck (P = 0·011) and a non‐significant trend towards reduction at the spine. BMD loss persisted for up to 2 years at the femoral neck (P = 0·005), but values returned to baseline at the spine. Reflecting the rapid initial decline in BMD, bone‐specific alkaline phosphatase (a serum marker of bone formation) showed a significant initial decline at 1 month but had recovered to pretransplant levels by 3 months. No new fractures were detected at 1 year post transplant. Sex, diagnosis, use of total body irradiation, stem cell source and type of graft (auto versus allo) did not significantly predict BMD change over the first 12 months. In conclusion, significant and persistent bone loss at the femoral neck was demonstrated in this group of patients following stem cell transplantation. The implications of these findings for future fracture risk require further study.
Bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA) is widely used in the management of patients with osteoporosis. Factors, which are specific to machine or to operator, ...can influence the accuracy and precision of BMD estimations. We studied the effect of leg rotation by 10 degrees either internally or externally from the standard position in a group of 50 women (average age 54.9, SD = 11.1 yr) who were free of bone active diseases or medications. External rotation of leg by 10 degrees from the customary position increased the average BMD by 0.005, 0.003, and 0.036 g/cm2 in the femoral neck, trochanter, and Ward's area (p = 0.119, 0.309, and <0.001), respectively. Internal rotation of leg by 10 degrees from the customary position decreased the average BMD by 0.009, 0.005, and 0.006 g/cm2 in the femoral neck, trochanter, and Ward's area (p = <0.001, 0.008, and <0.001), respectively. The number of subjects qualified for the diagnosis of osteoporosis based on the T-scores (equal to or below -2.5) of the femoral neck and trochanter did not change significantly in three different positions (18% in the customary position and after the external rotation and 14% after the internal rotation). A significant change in the femoral neck BMD (defined as 2.77 x precision error) was seen in 12% of subjects after the internal rotation and 8% after the external rotation. Our data emphasize the need for proper positioning of the hip during DXA scanning. Malrotation of the hip can be an important confounding factor when interpreting serial BMD values.
It is recommended that the hip joints be flexed to 90 degrees during dual-energy X-ray absorptiometry scanning of the lumbar spine in the anteroposterior projection; however, some patients are unable ...to maintain this position because of the presence of degenerative changes in lower limb joints. This study examines the effect of a lesser degree of hip flexion on the lumbar spine bone mineral density (BMD) measurement and its interpretation. Fifty women were scanned on the Norland Eclipse XR, initially in the standard position with the hips flexed to 90 degrees and then in the adjusted position after allowing for some degree of hip extension to keep them comfortable (hip flexion of 60 degrees -70 degrees ). Higher bone mineral content (BMC), surface area, and BMD values were seen in the standard position compared to the adjusted position, but none of the differences was statistically significant. There were strong correlations for BMC,surface area, and BMD measured in the two positions. In the standard position, 26 women were found to have osteoporosis and 18 had osteopenia. In the adjusted position, osteoporosis was noted in 27 women, and 18 had osteopenia. Four women showed a reduction, whereas 12 women showed an increase in BMD in excess of the least significant change at the 95% confidence level, defined as 2.77 times the precision error (0.008 g/cm(2) x 2.77 = 0.120 g/cm(2)). Our study demonstrates that a lesser degree of hip flexion in women who find it difficult to maintain the recommended 90 degrees hip flexion during the lumbar spine BMD measurement would not affect the patient classification based on T-scores recommended by the World Health Organization; however, variation in hip flexion can be a major confounding factor when interpreting a change in BMD over time.
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