AN APPROACH OF THE EFFECT OF OSTEOPOROSIS ON CANCELLOUS BONE'S MECHANICAL QUALITY BY DIGITAL MODELIZATION.

Introduction Osteoporosis is a metabolic disease of the bone responsible for a loss of bone resistance and an increase in fracture risk. World Health Organization (WHO) estimations are about 6.3 millions of femoral neck fractures in the world by 2050. These estimations make osteoporosis a real problem in term of public health. Knowledge in biological tissues mechanical behaviour and its evolution with age are important for the design of diagnosis and therapeutic tools. From the mechanical aspect, bone resistance is dependent on bone density, bone architecture and bone tissue quality. If the importance of bone density and bone architecture has been well explored, the bone tissue quality still remains unstudied because of the lack of biomechanical tools suitable for testing bone at this microscopic dimension. Therefore the goal of this study is to estimate the osteoporotic cancellous bone tissue mechanical behaviour at its microscopic scale, using an approach coupling mechanical assays and digital reconstruction. Materials and methods The experimental study is based on cancellous bone tissue extracted from human femoral head. Forty 8mm diameters bone cylinders have been removed from femoral head explanted after a femoral neck fracture treated by arthroplasty. These cylinders have been submitted to a digitally controlled compressive trial. Before and after the trials, microscanner analyses with an 8 μm spatial resolution have been realized in order to determine the micro structural parameters. The cylinders have been rebuilt with the digital model-building in order to estimate the mechanical behaviour and the bone quality. Results The results will be presented from a macroscopic and microscopic point of view and will show the relationship between gender and age of the patients. At the macroscopic scale, we will look at that apparent young modulus heterogeneity and the cracking strength. At the microscopic scale, we will confirm that the cancellous bone tissue mechanical behaviour is close to the Haversian bone tissue mechanical behaviour. Finally, the parametric study will permit us to point out the main microstructural components influencing cancellous bone tissue quality. Conclusion This study allows a precise estimation of the osteoporotic cancellous bone tissue mechanical behaviour. It seems to be a great step in the understanding of this disease and it could probably lead to great improvements in the diagnosis, prognostic, medical and surgical approaches of osteoporosis.