Effect of surgical defect localization on ultimate load-bearing capacity of human femur: finite-element energy-based assessment

Abstract

Elastic properties and toughness of cortical bone tissue are non-uniformly distributed over its anatomical quadrants. This can have an effect on the bone’s load-bearing capacity after a surgical resection associated with a removal of tumor-like lesions followed by formation of a sectorial bone defect. The purpose of this work is to evaluate the ultimate load-bearing capacity of the femur with the post-resection defect, taking into account various types of distributions of elastic properties and toughness in different quadrants of a cross section of the bone. The elasticity modulus of the bone tissue in the longitudinal direction of the femur is determined based on a nanoindentation test of a human femoral bone specimen. Based on numerical simulations, it is established that the most dangerous – with regard to the occurrence of a pathological fracture – is the localization of the post-resection defect, when a remaining fragment of the bone tissue is located in the anterior quadrant. In this case, the value of the ultimate load is significantly lower compared to that for other variants of localization of the post-resection defect. A non-uniform distribution of fracture toughness in the cross-section of the femur has a greater effect on the magnitude of the ultimate load than non-uniformity of elastic properties. This should be taken into account when evaluating the ultimate load, since averaging the toughness over the bone’s cross-section can result in overestimations. Neglecting non-uniformity of toughness can lead to an incorrect assessment of the ultimate load and to wrong recommendations for postoperative rehabilitation of a patient.