Ultrasound velocity and dual-energy X-ray absorptiometry in normal and pagetic bone

Bone affected by Paget's disease is known to be dense but more prone to fra ctures. It is proposed that dual-energy X-ray absorptiometry (DXA) and quan titative ultrasound (QUS) assess different aspects of the skeletal status. In this study, we used Paget's disease of the tibia as a model to explore t his. Ten patients with Paget's disease affecting a single tibia were invest igated with the normal side acting as the control within each individual. T ibial speed of sound (SOS) was: measured at the midpoint of the affected an d control tibiae using a Soundscan 2000 (Myriad Ultrasound System, Rehovot, Israel) device. Bone mineral density (BMD) of the tibia was measured at a level corresponding to the site of the tibial ultrasound using a QDR-2000(Hologic, Inc., Waltham, MA), The mean bone area and estimated volume in th e pagetic tibia was greater than that in the normal tibia (bone area: 25.10 +/- 8.00 vs, 20.23 +/- 5.43 cm(2), p = 0.017; estimated bone volume: 68.79 +/- 41.99 vs. 43.62 +/- 22.56 cm(3), p = 0.02), reflecting the bone expans ion characteristic of Paget's disease. The bone mineral content (BMC) was m ore markedly increased in the pagetic tibia (27.38 +/- 12.98 vs. 14.39 +/- 6.14 g, p = 0.003) and, consequently, areal bone mineral density (BMD) was also markedly increased in the pagetic bone (1.09 +/- 0.38 vs, 0.77 +/- 0.4 4 g/cm(2), p = 0.018), There was no significant difference in the estimated volumetric BMD between the pagetic and the normal tibia (0.48 +/- 0.24 vs. 0.47 +/- 0.51 g/cm(3), p = 0.96). Tn contrast, the mean tibial SOS in the leg affected by Paget's disease was significantly lower than in the unaffec ted leg (3228 +/- 234 vs. 3840 +/- 164 m/sec, p < 0.001). When expressed as at score using the normal limb as reference, areal BMD was 0.72 SD higher in the affected limb, whereas tibial SOS was 3.72 SD lower. We conclude tha t tibial SOS detects important changes in bone quality in Pager's disease o f bone, which are unrelated to calcium content. (C) 2000 by Elsevier Scienc e Inc. All rights reserved.