Adjacent vertebral body fracture is described as a risk after vertebroplasty and kyphoplasty. It may be true that this phenomenon is caused precisely because of the frequently used polymethylmethacrylate cement (PMMA), which shows a higher level of stiffness than bone material and may ultimately lead to shifting stress levels within the entire spine. The goal of the present study was to evaluate and compare the pressure distribution in the endplate of human vertebrae after kyphoplasty with PMMA and aluminum-free glass-polyalkenoate cement (gpc). For the present study, 8 fresh frozen human cadaveric vertebral bodies from the thoracolumbar junction were used. All vertebrae were augmented transpedicularly on one side with gpc and on the other side with PMMA. A loading of 600 N, 800 N and 1000 N was applied. In the data processing an individual region of interest (roi) was generated for each vertebra. The following parameters were determined for each roi: maximum force [N], maximum pressure [kPa], mean pressure [kPa], roi area [cm2]. We found significantly higher mean pressure values in the areas of the vertebrae augmented with PMMA, compared to the ones after augmentation with gpc (p = 0.012) when applying 1000 N. In the groups with lower forces there were no statistical relevant differences. The pressure distribution shows an advantage for gpc. A material, which does not create load concentration onto the cranial and caudal vertebral surface, could have major advantages concerning the risk of adjacent vertebral fractures. Thus the results of the 1000 N loading protocol suggest gpc being a possible alternative to ordinary PMMA cement, regarding its influence on stiffness in kyphoplasty. These and other general aspects like incorporation should be addressed and elaborated more detailed in further studies.
Keywords: Adjacent vertebral body fracture; Aluminum-free glass-polyalkenoate cement; Kyphoplasty; PMMA; Stiffness; Vertebral osteoporotic fractures.
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