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Keywords: bone quality, osteoporosis, dual energy x-ray absorptiometry, bone mineral density, finite element modelling.

Summary

Osteoporosis is a systemic skeletal disease whose manifestations lead to a state of enhanced bone fragility and hence susceptibility to fracture [1]. As actual imaging tools cannot access bone quality indicators in vivo, its diagnosis is mainly based on quantitative measurements, i.e., on bone mineral density (BMD), which do not fully explain fracture incidence.

In this study, a three-dimensional hierarchical model for bone remodelling was applied to the analysis of bone quality indicators, both at macro (bone density spatial distribution) and microscale (microarchitectures and orthotropy levels of trabecular bone). This analysis was preceded by the model validation through a quantitative and qualitative comparison with dual energy x-ray absorptiometry (DXA), the gold standard technique in osteoporosis diagnosis. The quantitative comparison results demonstrate the computational model predictive potential in bone density spatial distribution simulation, especially in the femoral neck region of interest. The correlation study between the model parameter k (related to metabolic cost of bone formation) and T-score (from the DXA examination) showed a strong correlation between them. These results represent the first step to patient-specific bone remodelling simulation, and to the long-term goal of its use in clinical practice as an auxiliary tool.

At the macroscale, the meaning of the bone mineral content (BMC) ratio between the trochanter and the femoral neck was analysed. Both computational and clinical results suggest that in a bone loss scenario, a biological bone remodelling system induces a localized bone loss, maintaining the femoral neck integrity. Hence this ratio may be a bone quality indicator related to absolute fracture risk.

At the microscale, bone quality was accessed through the analysis of microstructures and its orthotropy levels in different locations. The results show that the analysis of orthotropy levels may play an important role in the understanding and prevention of bone fragility fractures as it provides information on the relative strength of bone, in terms of load direction. On the other hand, the hierarchical model potential in the prediction of trabecular microarchitectures, may be suitable for bone scaffold design used for tissue regeneration.

Together, the results show that the adequate conjugation of diagnosis imaging tools with computational numerical simulation may lead to new developments in the understanding of bone strength. In this sense, the lack of imaging tools to access bone quality indicators in vivo, make bone quality investigation one of the most emergent areas in the biomechanics field. The development of models in lower physical scales may be the next step to the complete understanding of bone strength and fracture.

References

1: S.R. Cummings, L.J. Melton, "Epidemiology and outcomes of osteoporotic fractures", Lancet; 359, 1761-67, 2002. doi:10.1016/S0140-6736(02)08657-9

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 89 PROCEEDINGS OF THE SIXTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY Edited by: M. Papadrakakis and B.H.V. Topping Paper 56 A Dual Energy X-ray Absorptiometry Validation of a Bone Remodelling Model for the Assessment of Osteoporotic Bone Quality L. Santos¹^,³, P.G. Coelho², J.E. Fonseca³, H.C. Rodrigues¹ and P.R. Fernandes¹ ¹IDMEC-IST, Technical University of Lisbon, Portugal ²Department of Mechanical and Industrial Engineering, New University of Lisbon, Portugal ³Rheumatology Research Unit, IMM, Rheumatology and Bone Metabolic Diseases Department, Hospital de Santa Maria, University of Lisbon Medical School, Portugal doi:10.4203/ccp.89.56 purchase the full-text of this paper Full Bibliographic Reference for this paper L. Santos, P.G. Coelho, J.E. Fonseca, H.C. Rodrigues, P.R. Fernandes, "A Dual Energy X-ray Absorptiometry Validation of a Bone Remodelling Model for the Assessment of Osteoporotic Bone Quality", in M. Papadrakakis, B.H.V. Topping, (Editors), "Proceedings of the Sixth International Conference on Engineering Computational Technology", Civil-Comp Press, Stirlingshire, UK, Paper 56, 2008. doi:10.4203/ccp.89.56 Keywords: bone quality, osteoporosis, dual energy x-ray absorptiometry, bone mineral density, finite element modelling. Summary Osteoporosis is a systemic skeletal disease whose manifestations lead to a state of enhanced bone fragility and hence susceptibility to fracture [1]. As actual imaging tools cannot access bone quality indicators in vivo, its diagnosis is mainly based on quantitative measurements, i.e., on bone mineral density (BMD), which do not fully explain fracture incidence. In this study, a three-dimensional hierarchical model for bone remodelling was applied to the analysis of bone quality indicators, both at macro (bone density spatial distribution) and microscale (microarchitectures and orthotropy levels of trabecular bone). This analysis was preceded by the model validation through a quantitative and qualitative comparison with dual energy x-ray absorptiometry (DXA), the gold standard technique in osteoporosis diagnosis. The quantitative comparison results demonstrate the computational model predictive potential in bone density spatial distribution simulation, especially in the femoral neck region of interest. The correlation study between the model parameter k (related to metabolic cost of bone formation) and T-score (from the DXA examination) showed a strong correlation between them. These results represent the first step to patient-specific bone remodelling simulation, and to the long-term goal of its use in clinical practice as an auxiliary tool. At the macroscale, the meaning of the bone mineral content (BMC) ratio between the trochanter and the femoral neck was analysed. Both computational and clinical results suggest that in a bone loss scenario, a biological bone remodelling system induces a localized bone loss, maintaining the femoral neck integrity. Hence this ratio may be a bone quality indicator related to absolute fracture risk. At the microscale, bone quality was accessed through the analysis of microstructures and its orthotropy levels in different locations. The results show that the analysis of orthotropy levels may play an important role in the understanding and prevention of bone fragility fractures as it provides information on the relative strength of bone, in terms of load direction. On the other hand, the hierarchical model potential in the prediction of trabecular microarchitectures, may be suitable for bone scaffold design used for tissue regeneration. Together, the results show that the adequate conjugation of diagnosis imaging tools with computational numerical simulation may lead to new developments in the understanding of bone strength. In this sense, the lack of imaging tools to access bone quality indicators in vivo, make bone quality investigation one of the most emergent areas in the biomechanics field. The development of models in lower physical scales may be the next step to the complete understanding of bone strength and fracture. References 1 S.R. Cummings, L.J. Melton, "Epidemiology and outcomes of osteoporotic fractures", Lancet; 359, 1761-67, 2002. doi:10.1016/S0140-6736(02)08657-9 purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £95 +P&P)
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