High-resolution three-dimensional-pQCT images can be an adequate basis for in-vivo μFE analysis of bone

Micro-finite element (microFE) models based on high-resolution images have enabled the calculation of elastic properties of trabecular bone in vitro. Recently, techniques have been developed to image trabecular bone structure in vivo, albeit at a lesser resolution. The present work studies the usefulness of such in-vivo images for microFE analyses, by comparing their microFE results to those of models based on high-resolution micro-CT (microCT) images. Fifteen specimens obtained from human femoral heads were imaged first with a 3D-pQCT scanner at 165 microns resolution and a second time with a microCT scanner at 56 microns resolution. A third set of images with a resolution of 165 microns was created by downscaling the microCT measurements. The microFE models were created directly from these images. Orthotropic elastic properties and the average tissue von Mises stress of the specimens were calculated from six FE-analyses per specimen. The results of the 165 microns models were compared to those of the 56 microns model, which was taken as the reference model. The results calculated from the pQCT-based models, correlated excellent with those calculated from the reference model for both moduli (R2 > 0.95) and for the average tissue von Mises stress (R2 > 0.83). Results calculated from the downscaled micro-CT models correlated even better with those of the reference models (R2 > 0.99 for the moduli and R2 > 0.96 for the average von Mises stress). In the case of the 3D-pQCT based models, however, the slopes of the regression lines were less than one and had to be corrected. The prediction of the Poisson's ratios was less accurate (R2 > 0.45 and R2 > 0.67) for the models based on 3D-pQCT and downscaled microCT images respectively). The fact that the results from the downscaled and original microCT images were nearly identical indicates that the need for a correction in the case of the 3D-pQCT measurements was not due to the voxel size of the images but due to a higher noise level and a lower contrast in these images, in combination with the application of a filtering procedure at 165 micron images. In summary: the results of microFE models based on in-vivo images of the 3D-pQCT can closely resemble those obtained from microFE models based on higher resolution microCT system.

[1]  R Huiskes,et al.  The role of an effective isotropic tissue modulus in the elastic properties of cancellous bone. , 1999, Journal of biomechanics.

[2]  P. Rüegsegger,et al.  Ridge number density: a new parameter for in vivo bone structure analysis. , 1997, Bone.

[3]  S. Goldstein,et al.  The direct examination of three‐dimensional bone architecture in vitro by computed tomography , 1989, Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research.

[4]  R. Huiskes,et al.  Fabric and elastic principal directions of cancellous bone are closely related. , 1997, Journal of biomechanics.

[5]  R. Huiskes,et al.  Direct mechanics assessment of elastic symmetries and properties of trabecular bone architecture. , 1996, Journal of biomechanics.

[6]  D P Fyhrie,et al.  Human vertebral body apparent and hard tissue stiffness. , 1998, Journal of biomechanics.

[7]  P. Rüegsegger,et al.  The ability of 3-D structural indices to reflect mechanical aspects of trabecular bone , 1999 .

[8]  R. Huiskes,et al.  A new method to determine trabecular bone elastic properties and loading using micromechanical finite-element models. , 1995, Journal of biomechanics.

[9]  T M Keaveny,et al.  Three-dimensional imaging of trabecular bone using the computer numerically controlled milling technique. , 1997, Bone.

[10]  S. Majumdar,et al.  Impact of spatial resolution on the prediction of trabecular architecture parameters. , 1998, Bone.

[11]  P Rüegsegger,et al.  Non-invasive bone biopsy: a new method to analyse and display the three-dimensional structure of trabecular bone. , 1994, Physics in medicine and biology.

[12]  U. Bonse,et al.  3D computed X-ray tomography of human cancellous bone at 8 microns spatial and 10(-4) energy resolution. , 1994, Bone and mineral.

[13]  P. Rüegsegger,et al.  Calibration of trabecular bone structure measurements of in vivo three-dimensional peripheral quantitative computed tomography with 28-microm-resolution microcomputed tomography. , 1999, Bone.

[14]  F Melsen,et al.  A direct method for fast three‐dimensional serial reconstruction , 1990, Journal of microscopy.

[15]  Andres Laib,et al.  Bone density and microstructure : new methods to determine bone quality and fracture risk , 2001 .

[16]  P. Rüegsegger,et al.  The ability of three-dimensional structural indices to reflect mechanical aspects of trabecular bone. , 1999, Bone.

[17]  S. H. Kan,et al.  Epidemiology of vertebral fractures in women. , 1989, American journal of epidemiology.

[18]  J. Kinney,et al.  Numerical errors and uncertainties in finite-element modeling of trabecular bone. , 1998, Journal of biomechanics.

[19]  G. Blake,et al.  Screening for osteopenia and osteoporosis , 1997 .

[20]  P Rüegsegger,et al.  Comparison of structure extraction methods for in vivo trabecular bone measurements. , 1999, Computerized medical imaging and graphics : the official journal of the Computerized Medical Imaging Society.

[21]  C. Slemenda,et al.  Pathogenesis of osteoporosis. , 1995, Bone.

[22]  P Rüegsegger,et al.  Assessment of cancellous bone mechanical properties from micro-FE models based on micro-CT, pQCT and MR images. , 1998, Technology and health care : official journal of the European Society for Engineering and Medicine.

[23]  A. Parfitt Implications of architecture for the pathogenesis and prevention of vertebral fracture. , 1992, Bone.

[24]  P. Rüegsegger,et al.  Finite element analysis of trabecular bone structure: a comparison of image-based meshing techniques. , 1998, Journal of biomechanics.

[25]  G. Blake,et al.  Screening for Osteopenia and Osteoporosis: Do the Accepted Normal Ranges Lead to Overdiagnosis? , 1997, Osteoporosis International.

[26]  N. Kikuchi,et al.  A homogenization sampling procedure for calculating trabecular bone effective stiffness and tissue level stress. , 1994, Journal of biomechanics.

[27]  R. Huiskes,et al.  The Anisotropic Hooke's Law for Cancellous Bone and Wood , 1998, Journal Of Elasticity.

[28]  H. Song,et al.  Cancellous bone volume and structure in the forearm: noninvasive assessment with MR microimaging and image processing. , 1998, Radiology.

[29]  R. Huiskes,et al.  Determination of trabecular bone tissue elastic properties by comparison of experimental and finite element results , 1997 .

[30]  S. Goldstein,et al.  Finite‐element modeling of trabecular bone: Comparison with mechanical testing and determination of tissue modulus , 1998, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.