Finite element analysis and the clinical consideration for the methodology of PMMA injection in vertebroplasty

Vertebroplasty is one of the most effective medical treatments for the collapse of the vertebral body. A general approach used for vertebroplasty is the polymethyl-methacrylate (PMMA) injection method, which involves injection at both sides of the vertebrate and allowing it to discharge via an end hole at the apical end of the injection needle. However, some patients that have received vertebroplasty through the method with some problems such as PMMA leakage and thermal emission; thus, there is a need to develop a new injection method. Accordingly, in this study we developed a method to inject PMMA into the upper end of the central vertebral body using an improved injector with a side-hole and discussed the clinical consideration. Prior to conducting a clinical study to test the improved instrument, the newly developed method was tested by performing finite element analysis at different PMMA injection: the single PMMA injection and both-sided injection. In this analysis, a single injection at the center of vertebral body was shown to yield a displacement of 0.15 mm, while the displacement for an injection at both sides was 0.24 mm. The combined results of this study suggest that the best place for injection was at the center (top-front) of the vertebral body. In addition, a clinical study on vertebroplasty using the existing end-hole injector and the newly developed side-hole injector was performed 6 months after operation. In these studies, a single PMMA injection was conducted on the upper part of the central vertebral body and the compressed and transformed vertebral body prior to treatment was restored after treatment. In addition, there was relatively little leakage of PMMA to peripheral regions. Therefore, it is expected that a PMMA injection on a single side in an accurate region using the improved injector will aid to reduce existing complications and sequelae.