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Byline: M. Hudelmaier (1,2), V. Kuhn (1,2), E. M. Lochmuller (3), H. Well (1,2), M. Priemel (4), T. M. Link (5), F. Eckstein (1,2) Keywords: Cortical bone; Dual X-ray absorptiometry; Mechanical competence; Peripheral quantitative CT; Quantitative ultrasound; Trabecular bone Abstract: The diagnosis of osteoporosis is generally based on the assessment of bone mineral content with dual X-ray absorptiometry (DXA) but does not account for the spatial distribution and inherent material properties of the tissue. Peripheral quantitative computed tomography (pQCT) permits one to measure the compartment-specific density and geometry-based parameters of cortical bone. Quantitative ultrasound (QUS) parameters are associated with material properties of cortical bone. The purpose of this study was to test the hypothesis that pQCT and cortical QUS provide additional information to DXA in predicting structural strength of the distal radius. The intact right arm and the isolated left radius were harvested from 70 formalin-fixed cadavers (age 79+-11 years). The bone mineral content (BMC) was assessed with DXA at the radial metaphysis and shaft. pQCT was also used at the metaphysis and the shaft, while QUS was employed only at the shaft. The failure loads of the radius were assessed by use of a 3-point bending test (isolated radius) and a complex fall simulation (intact arm). The BMC (DXA) displayed a correlation of r=0.96 with the failure moments in 3-point bending (P&lt 0.001). The correlation between failure load and geometry-based parameters (pQCT) ranged from r=0.85 to r=0.96 and was r=0.64 for the speed of sound (QUS) (P &lt 0.001). Cortical thickness (pQCT) improved the prediction marginally (r=0.964) in combination with DXA. For the fall simulation, the correlation coefficients were r=0.76 for BMC (DXA) of the shaft, r=0.83 for metaphyseal bone content (pQCT), r=0.55 for QUS, and ranged from r=0.59 to r=0.74 for geometry-based parameters at the shaft (pQCT). pQCT and QUS parameters provided no significant improvement versus DXA alone. Measurement of bone mass by DXA or pQCT thus appears to be sufficient as a surrogate of mechanical strength and fracture risk of the distal radius. Author Affiliation: (1) Musculoskeletal Research Group, Institute of Anatomy, LMU Munchen, Pettenkoferstrasse 11, 80336, Munich, Germany (2) Institute of Anatomy, Paracelsus Private Medical University, Salzburg, Austria (3) 1st Gynaecology Hospital, LMU Munchen, Munich, Germany (4) Department of Trauma Surgery, Hamburg University School of Medicine, Hamburg, Germany (5) Department of Radiology, Technische Universitat Munchen, Munich, Germany Article History: Registration Date: 10/11/2003 Received Date: 23/06/2003 Accepted Date: 06/09/2003 Online Date: 22/01/2004 Article note: M. Hudelmaier and V. Kuhn contributed equally to this study

Byline: T. M. Link (1), T. M. Link (3), T. M. Link (4), O. Saborowski (1), K. Kisters (2), M. Kempkes (2), M. Kosch (2), D. Newitt (3), Y. Lu (3), S. Waldt (1), S. Waldt (4), S. Majumdar (3) Keywords: Key words:Bones, absorptiometry -- Bones, MRI -- Calcaneus -- Kidney, transplantation -- MRI, high-resolution -- Osteoporosis Abstract: The purpose of this study was to use high-resolution magnetic resonance (HR-MR) imaging to analyze the trabecular bone structure of the calcaneus in patients before and after renal transplantation and to compare this technique with bone mineral density (BMD) in predicting therapy-induced bone loss and osteoporotic fracture status. HR-MR imaging (voxel size: 0.195x0.195x1 mm) was performed at 1.5 T with an axial and sagittal orientation in 48 patients after transplantation, 12 patients before renal transplantation and 20 healthy controls. Structure measures analogous to standard histomorphometry and fractal dimension were determined in these images. BMD measurements of the lumbar spine and the proximal femur were obtained in the healthy female controls and the patients. Vertebral and peripheral fracture status were determined in all patients. The structural measures app.BV/TV, Tb.Sp, Tb.Th and Tb.N showed significant differences between controls and patients (p&lt 0.05) while fractal dimension showed no significant differences. Neither the structural measures nor BMD showed significant differences between patients before and after transplantation. Correlations between time after transplantation versus structural measures and BMD were not significant. Differences between fracture and nonfracture patients were significant for the structural measures app.BV/TV, Tb.Sp and Tb.N (axial images) as well as for app.Tb.Th (sagittal images) and spine BMD (p&lt 0.05) but not for hip BMD. Using odds ratios the strongest discriminators between patients with and without fractures were app. BV/TV, app.Tb.Sp (axial images) and app.Tb.Th (sagittal images), even after adjustment for age and BMD. Using receiver operating characteristic analysis the highest diagnostic performance was found for a combination of BMD and structural measures. In conclusion, our results indicate that structural measures obtained from HR-MR images may be used to characterize fracture incidence in kidney transplant patients the best results, however, are obtained using a combination of BMD and structural measures. Author Affiliation: (1) Department of Clinical Radiology, DE (2) Department of Internal Medicine D/Nephrology, University of Muenster, Muenster, Germany, DE (3) Department of Radiology, University of California, San Francisco, California, USA , US (4) Department of Radiology, Technische Universitaet, Munich, Germany, DE Article note: Received: 25 October 2000 / Accepted: 1 August 2001