BACKGROUND: There are many controversies about how to assess fracture risks of the proximal femoral metastases tumor in clinical practice.
OBJECTIVE: To establish the three-dimensional finite element model of different sizes of the osteolytic metastases tumor in proximal femur, and to analyze the stress changes in the local lesion during slow walk mode and to assess the fracture risks.
METHODS: Both lower extremities of the volunteers underwent thin CT scan to obtain data related to the femur. The image data were input into Mimics11.1 image processing software for image processing, then, the data were input into UG4.0 software to establish the bone lesion model of three parts of proximal femur. Then, loaded the femur when single foot landing during slow walking mode. Finally, the finite element software was used to analyze the femoral neck district, intertrochanteric area and change of stress levels in subtrochanteric zone.
RESULTS AND CONCLUSION: Defects of femoral neck level: when the intramedullary defect did not involved inner cortex in diameter to 90%, the local stress abruptly increased to 135.98 MPa, while intramedullary defects involved half of medial cortex to 70%, the local stress abruptly increased to 92.34 MPa. When the hemispheric lesions with destruction of the cortex up to 60%, the local stress became greater than the yield stress, and up to 101.19 Mpa. Intertrochanteric level: when the intramedullary defect did not involved inner cortex in diameter to 80%, the local stress jumped to 131.21 MPa, while intramedullary defects involved half of medial cortex to 80%, the local stress abruptly increased to 105.19 MPa. The hemispherical lesions with destruction of the cortex defect of 80%, the local stress was greater than the yield stress scale, and up to 92.21 MPa. While intramedullary defects involved half of medial cortex to 80%, the local stress jumped to 92.42 MPa. When hemispheric lesions with destruction of the cortex increased to 70%-80%, the local stress will increased to 89.97-105.19 Mpa, and greater than the yield stress. In proximal femur, the intramedullary lesions which do not penetrate the cortical bone have little effect on stress scales in the same place. For the lesions which destroy the unilateral cortical bone, the risks would occur on such conditions as: in femoral neck level, the destruction in diameter greater more than 60%; in intertrochanteric level, the destruction in diameter greater more than 70%; in subtrochanteric level, the destruction in diameter greater more than 70%.