Vertebroplasty versus kyphoplasty:: Biomechanical behavior under repetitive loading conditions

Study Design. Ex vivo biomechanical study using osteoporotic cadaveric fractured vertebral bodies. Objective. To investigate the behavior of fractured osteoporotic vertebral bodies treated with either vertebroplasty or kyphoplasty under repetitive loading conditions. Summary of Background Data. Vertebroplasty and kyphoplasty are newer alternatives for the treatment of osteoporotic vertebral fractures. Loading conditions that can lead to fractures treated with these methods will likely be encountered subsequently; as such, it is important to understand differences in the biomechanical behavior of the resultant constructs. Methods. There were 7 pairs of osteoporotic T8 and T10 vertebral bodies cyclically loaded to produce a vertebral compression fracture. Of each pair, one was assigned to the kyphoplasty group and the other to the vertebroplasty group. After treatment, specimens were cyclically loaded to 100,000 cycles, between 20% and 70% of the predicted failure load. Results. Height was restored with kyphoplasty, but the vertebral bodies showed significant height loss during cyclic loading. Vertebroplasty specimens had higher compression stiffness and smaller height reduction. Conclusions. Under repetitive loading conditions, fractured vertebral bodies treated with kyphoplasty were initially taller, but because of a progressive loss of height during loading, the resulting constructs were shorter after 100,000 cycles than those treated with vertebroplasty.