Biomechanics of percutaneous vertebral augmentation with bone graft: a finite element evaluation

Objective To investigate the biomechanical effects of percutaneous vertebral augmentation with bone graft (Optimesh) using three-dimensional finite element model of lumbar. Methods Three-dimensional, anatomically detailed finite element (FE) models of the L1-L2 functional spinal unit (FSU) were developed on the basis of cadaver computed tomography (CT) scans. As a result, the finite element model of the functional spinal unit L1-L2 was developed, consisting of 23 446 solid elements, 310cable elements and a total of 36 009 nodes. For simulating Optimesh, cancellous bone granules were placed into L2 vertebra. The changes in stress and strain on vertebral bodies were analyzed before and after the operation of cancellous bone granule augmentation under following loading conditions: compression,flexion and extension. Results Under compression, flexion and extension loading conditions evaluated in the current study, the maximum yon Mises stress and strain within the reinforcement material plug in the treated level due to the presence of morcelized cancellous bone were 0. 333, 0. 436, 0. 321 MPa and 0. 335%, 0. 438%, 0. 322% respectively, whereas the maximum yon Mises stress and strain within corresponding area in the osteoporotic, untreated model were 0. 174, 0.239, 0. 161 MPa and 0.512%,0. 709%, 0. 474% respectively. Compared to the untreated model, the maximum von Mises stress and and strain within the reinforcement area in the treated model were approximately double and two-thirds those in the osteoporotic model respectively. Conclusion Percutaneous vertebral augmentation with bone graft ( Optimesh(R) ) can improve the biomechanical strength of vertebral body, and can be used as a new method in the percutaneous vertebroplasty operation. Key words: Bone graft; Spine; Biomechanics