Biomechanical finite element analysis of adjacent vertebral bodies following percutaneous kyphoplasty / 中国组织工程研究

ABSTRACT

BACKGROUND: The incidence of the adjacent vertebral fracture after kyphoplasty is about 2.4%-23.0%, and 2/3 of new fractures occurred in adjacent vertebrae in 6 months. There is controversy addressing the reason which is the development of osteoporosis or the result of bone cement augment at present.OBJECTIVE: To determine the correlations between percutaneous kyphoplasty on adjacent vertebral endoplates stresses pressure under physiologianl load and a new fracture of adjacent vertebral body in physiological load.METHODS: Computed tomography (CT) data of an old female osteoporotic patient was selected, and a three-dimensional finite element model of the osteoporetic thoracolumbar spine T_(12)-L_1-L_2 was created by using kinds of computer aided design software.The height of vertebral L_1 was compressed by 60% to simulated the compressed fracture, and the height of L_1 became the 90% of normal to simulate the replacement, two columns-like PAMA mass (4 mL) was placed in vertebral L_1 to simulate pemutaneous kyphoplasty. The stress on inferior endplate of L_(12) and superior endplate of L_2 was compared with three models. RESULTS AND CONCLUSION: Compared to the normal vertebral body, the maximum stress in the adiacent vertebral bodies endplates increased by 76% for L_1 compress fracture model and increased by 27% for kyphoplasty model, respectively. The stress on the posterior part of vertebral body after percutaneous kyphoplasty have an average increase of 13.2%, of which 4.5% increase in the pedicle, isthmus, and 6.15% increased in the key points 25.6%, but with the wedge-shaped fracture of L_1 vertebral body compared to the model, percutaneous kyphoplasty after pedicle, isthmus and the articular process had reduced stress. The results indicate that the stress on inferior endplate of L-(12) and superior endplate of L_1 increased after percutaneous kyphoplasty under all loading conditions. Increased stress may lead endplate fracture, and increase the risk of adjacent vertebral body fracture. Further researches are needed to support the conclusion.