R.K. Wilcox (UK)
Spine, finite element, vertebroplasty, fracture
The use of vertebroplasty in the treatment of osteoporotic compression fractures is rapidly increasing, however recent evidence suggests the procedure may increase the risk of adjacent vertebral fracture in the medium to long term. The aim of this study was to use a finite element approach to model the effects of vertebroplasty on the adjacent vertebral body. The effect of cement stiffness was also investigated. A finite element model of an osteoporotic human lumbar functional spinal unit was used in this study. The vertebroplasty procedure was simulated with two different stiffness cements following an initial load to failure. The model was then reloaded over a number of cycles. The model was also loaded to failure and reloaded without augmentation. Following initial load to failure and augmentation, the treated models were initially stiffer than the model that had not been treated. Following four additional reloading cycles, the stiffness of the augmented segments dropped below that of the untreated segment. The cement stiffness caused little difference in the final segment stiffness. Vertebroplasty causes a shift in the load transfer through the spinal unit. In the case of highly osteoporotic bone, even a reduction in cement modulus cannot prevent eventual failure of the adjacent vertebra.
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