In vivo tricalcium phosphate, bone morphogenetic protein and autologous bone marrow biomechanical enhancement in vertebral fractures in a porcine model.

PURPOSE: Minimally invasive techniques that introduce cement and bone substitutes inside the fractured vertebral body are a new treatment line with clinically proven efficacy. However, mechanical behaviours between different fillers throughout fracture evolution is yet to be clarified, as many substances are available for introduction into the vertebral body fracture.
METHODS: We comparatively studied biomechanical properties of tricalcium phosphate, tricalcium phosphate with bone morphogenetic protein (rhBMP-7) and autologous bone marrow aspirate with rhBMP-7 in vivo to determine what substance is optimal for repairing vertebral lesions in a porcine model. This biomechanical study was carried out with an Instron-type testing machine. Data registered were necessary strength to reach vertebral fracture [Newtons (N)], shortening (millimeters) of the vertebra, energy absorption until vertebral fracture (Joules) and vertebral unit stiffness.
RESULTS: For statistical study, we used the SPSS 16 package at a significance level of α = 0.05. In the presentation of the results, mean, standard deviation of mean, median and interquartile range (IQR) were analysed. Mean and standard deviation (SD) of strength in newtons (N) for the vertebral fracture are 756 N (SD = 253) in group 1, 1,500 N (SD = 1598) in group 2 and 1,230 N (SD = 1,598) in group 3. Stiffness after fracture was 229 N (SD = 123) in group 1, 277 N (SD = 135) in group 2 and 404 N (SD = 325) in group 3.
CONCLUSIONS: The association of tricalcium phosphate and BMP-7 generates major vertebral resistance to external energy, the cause of such fractures. In such fractures, minor shortening occurs as soon as the vertebral body is fractured. Autologous bone marrow and BMP-7 provides increased biomechanical behavior, and the vertebral body is thus significantly strengthened.