Biomechanical effects of balloon kyphoplasty on treated and adjacent non-treated vertebral bodies: Pre and post operative evaluation

Balloon kyphoplasty (BKP) is one of the most reliable minimally invasive surgery (MIS) procedure to treat osteoporotic vertebral compression fractures (VCFs). However, untoward complications of high incidence of adjacent vertebral fractures after BKP and their risk factors are still equivocal. To further investigate the underlying cause of this phenomenon, non-linear finite element analysis (FEA) was fully utilized based on load sharing distribution, strain energy distribution and fracture risks evaluation. For this purpose, an image-based pre and postoperative three-dimensional (3D) finite element models of thoracic and lumbar spinal unit (T11-L3) for an osteoporotic patient were developed. After BKP, the load sharing distribution (between anterior and posterior column), strength and stiffness of the augmented vertebra has significantly improved. However, higher generation of interface stresses and deformation energy were found immediately at the adjacent vertebral bodies, which makes them susceptible to the risks of bone failures. Failure risks evaluation based on the incremented loads of 1kN to 10kN (50% risk of spinal injury) have shown very encouraging results. Apparently, the postoperative deformation onset loading (5kN) was fallen within the acceptable range that was higher than the standard normal daily living activities (1kN). It is believed that, the optimization of the material properties used in BKP procedure with the depth understanding on the historical and natural evolution of the osteoporosis could achieve optimal clinical outcomes in the future.