Influence of freeze-drying and irradiation on mechanical properties of human cancellous bone : application to impaction bone grafting

The use of fresh-frozen cancellous allograft has been proven to be successful in restoring the bone stock and implant stability with the impaction bone grafting technique. However, processed bone allografts offered a better safety level compared to frozen non processed bones. Their effectiveness as a reliable grafting material for impaction was addressed. A series of mechanical testing using static and dynamic assays on cancellous bone were used to assess the mechanical influence of various parameters such as freeze-drying, irradiation at 25 kGy and the order of sequence. Mechanical influence of freeze-drying, irradiation and sequences of both has been assessed by in-between columns compression tests on cancellous bone. Compaction studies in femoral and acetabular models and implant stability in a hip simulator have been observed with the processed graft material compared to the fresh-frozen bone. Freeze-drying and irradiation have a negative synergetic effect that renders the bone brittle. Separately, irradiation and freeze-drying do not alter the mechanical parameters. Freeze-dried and irradiated bone brittleness makes compaction easier and impacted graft layer stiffness and density higher than those of fresh-frozen material. Large particles obtained with a rongeur or with large rasps bone mill are recommended for acetabular reconstruction while small morsels obtained with the thin rasp of the Noviomagus bone mill shall be used on the femoral side. Bone powder particles are less suitable as their shear strength is limited. Implant stability after compaction of freeze-dried irradiated bone graft is comparable to the stability of primary arthroplasty.Thèse de doctorat en sciences médicales (MED 3)--UCL, 201