An ex vivo exothermal and mechanical evaluation of two-solution bone cements in vertebroplasty

Background context: Previous ex vivo studies showed that the properties of commercial cements modified for use in vertebroplasty are not optimal and are associated with several drawbacks, including high exothermic reaction, low cement viscosity and consequent extravasation, and unpredictable wait time after cement preparation. Additionally, strength and stiffness restoration are controversial varying with the cement type, volume injected, and technique used. Purpose: To investigate maximum polymerization temperatures and mechanical performance of novel two-solution bone cement (TSBC) modified by the addition of cross-linked poly(methyl methacrylate) nanospheres (η-TSBC) and microspheres (μ-TSBC) in a cadaver vertebroplasty model in comparison to a commercially available cement (KyphX). To study the viability of application of these novel cement formulations in the treatment of vertebral compression fractures. Study design/setting: Ex vivo biomechanical and exothermal evaluation of TSBCs using cadaveric vertebral bodies (VBs). Methods: Thirty-one cadaveric vertebrae (age, 74±2 years; T score, -1.5±0.5) were disarticulated. Thirteen vertebrae were assigned into three groups and instrumented with thermocouples positioned midbody along the intersection of the midsagittal and midcoronal axes, as well as along the intersection of the midsagittal axis and posterior VB wall. After equilibration at 37°C, 5 mL of cement was injected and temperatures were recorded for 1 hour. The groups were injected with η-TSBC, μ-TSBC, or KyphX. The remaining 18 vertebrae were biomechanically tested. After randomization into three groups, each specimen was fractured in compression and stabilized with 5 mL of each cement type. Each specimen was then retested in axial compression. Results: Temperatures in the central region of the vertebrae were significantly lower (p<.05) when injected with η-TSBC (44°C) in comparison to KyphX (75°C) and μ-TSBC (64°C). A significant difference was not detected between the pre- and postcementing strength (p>.05) of the three groups. There was no significant difference between the average values of stiffness among the cements (p>.05), however there was a significant difference between intact and treated stiffness (p<.05). Conclusions: The TSBC cements decreased the local temperature within the VB while providing similar mechanical strength when compared with vertebrae treated with KyphX.