A medical device company asked us to assist them with conducting a study to evaluate the ability of a particular self-setting calcium phosphate cement to restore the structural integrity of vertebral compression fractures (VCF). We utilized a 2-functional spinal unit (2FSU) cadaver model and evaluated it under physiologically relevant loading. We used ten thoracolumbar 2 functional spinal unit (FSU) specimens to evaluate structural integrity under compressive loading during initial anterior VCF creation (in the central vertebral body), after fracture, and after kyphoplasty treatment. Bipedicular kyphoplasty treatment was performed in a 37ºC chamber to reduce the fracture and create a void, which was then filled with either a calcium phosphate cement or polymethylmethacrylate (Figure 1) and allowed to cure for at least 15 minutes. Using fluoroscopic imaging, several vertebral body morphological parameters and the wedge angle were measured on the central vertebral body for each condition at a 1,000-N compressive load. A repeated-measures linear model was used to determine if the differences in these parameters among the various experimental conditions were statistically significant (p < 05). Compared with the fractured condition, there was a significant improvement in the morphological parameters and in the wedge angle under a physiologically relevant 1,000-N compressive load once applied after kyphoplasty treatment. There was no statistically significant difference between treatment with calcium phosphate or polymethylmethacrylate. This study showed that the structural properties of calcium phosphate augmented vertebral bodies are similar to those of polymethylmethacrylate augmented vertebral bodies. In addition, the study indicated that, after at least 15 minutes of setting, a fractured 2 functional spinal unit specimen treated with kyphoplasty with either material could withstand physiologically relevant loading. This study is in press to be published in 2008 in
The Spine Journal.*
*Khanna AJ, Lee S, Villarraga M, Gimbel J, Steffey D, Schwardt J. Biomechanical evaluation of kyphoplasty with calcium phosphate cement in a 2-functional spinal unit vertebral compression fracture model. Spine, 2008, in press.