A novel magnesium phosphate cement paste enables effective augmentation of pedicle screws in osteoporotic bone

Routine augmentation of pedicle screws in standard clinical practice is performed using polymethylmethacrylate (PMMA) cement. However, owing to its high compressive strength and high Young's modulus, this material acts more as a stiffener in the spine than as a suitable replacement for compressed cancellous bone. Adjacent fractures caused by this represent a common clinical problem. A new experimental magnesium phosphate cement seems more suitable for this purpose, as it shows promising biomechanical properties and has been proven to be injectable via long cannulated systems. However, the application of this material has not yet been explored or quantified.

Fenestrated pedicle screws were inserted into polyurethane bone blocks of different densities and augmented with experimental magnesium phosphate cement. This was followed by biomechanical testing in a realistic loading scenario. In addition, the injection force required for augmentation was quantified depending on the syringe type.

Cement augmentation was possible in all bone blocks used and consistently had a positive effect on the biomechanical stability of fenestrated pedicle screws. The size of this effect varied depending on the density of the bone blocks used. No cutoff value could be identified at which augmentation should be performed.

The novel experimental ready-to-use formulation of magnesium phosphate cement reliably enabled cement augmentation of fenestrated pedicle screws and consistently resulted in improved biomechanical stability. These findings suggest that a biocompatible and degradable bone cement with suitable biomechanical properties may represent a future alternative for spinal augmentation.