Prophylactic vertebroplasty versus kyphoplasty in osteoporosis: A comprehensive biomechanical matched-pair study by in vitro compressive testing

Vertebroplasty and kyphoplasty are alternative augmentation techniques of osteoporotic vertebral compression fractures. However, shortly after augmentation, new vertebral compression fractures may occur, mostly in the adjacent vertebrae. To prevent this, prophylactic cement injection can be applied to the neighboring vertebral bodies. Although there are many evidence-based clinical studies on the potential hazards of vertebroplasty and kyphoplasty, there are only few studies comparing the prophylactic potential of the two treatments. In this matched-pair experimental biomechanical study, the two treatments were compared via destructive compressive testing of 76 non-fractured osteoporotic human lumbar vertebral bodies from 24 cadavers, augmented pair-wise with vertebroplasty or kyphoplasty. Strength, stiffness and deformability were analyzed in terms of donor age, CT-based bone density, vertebral morphometry, and cement-endplate contacts. These were investigated in a paired analysis and also in terms of the number of cement-endplate contacts. Vertebroplasty resulted in significantly, but only 19% larger stiffness, approximately equal failure load and smaller failure displacement compared to kyphoplasty. Cement-endplate contacts affect augmentation differently for the two techniques, namely, strength significantly increased with increasing number of contacts in vertebroplasty, but decreased in kyphoplasty. The reasons for these contrasting behavior included the fundamentally different augmentation method, the resulting different construction and location of cement clouds and the different form and location of failure. These results indicate that both prophylactic vertebroplasty and kyphoplasty of non-fractured adjacent vertebrae may be advantageous to avoid subsequent fractures after post-fracture vertebroplasty and kyphoplasty, respectively. However, cement bridging in vertebroplasty and central cement placement in kyphoplasty are advantageous in prevention.