Object: The purpose of the study was to investigate the segmental effects of prophylactic vertebroplasty under increasingly demanding loading conditions and to assess the effect of altered cement properties on the construct biomechanics.
Methods: Twelve human cadaveric 3-vertebral functional spinal units (T12-L2) were prepared such that the intact L-1 vertebra was prophylactically augmented with cements of differing elastic moduli (100, 50, 25, and 12.5% modulus of the base cement). These specimens were subjected to quasistatic subfailure compression pre- and postaugmentation to 50% of the predicted failure strength and then cyclic loading in a fatigue rig (115,000 cycles) to characterize the high-stress, short-cycle fatigue properties of the construct. Loading was increased incrementally in proportion to body weight to a maximum of 3.5 x body weight. Quantitative computed tomography assessment was conducted pre- and postaugmentation and following cyclic testing to assess vertebral condition, cement placement, and fracture classification.
Results: Adjacent and periaugmentation fractures were induced in the prophylactically augmented segments. However, it appeared that these fractures mainly occurred when the specimens were subjected to loads beyond those that may commonly occur during most normal physiological activities.
Conclusions: Lowering the elastic modulus of the cement appeared to have no significant effect on the frequency or severity of the induced fracture within the vertebral segment.