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ABSTRACT
Clinical practices in spinal surgery have shown that pedicle screw fixation augmented by polymethyl methacrylate (PMMA) bone cement has improved outcomes for osteoporotic patients, Here, a biodegradable calcium phosphate-based nanocomposite (CPN) exhibiting better anti-pullout ability but similar fluidity and dispersing ability compared to clinically-used polymethyl methacrylate (PMMA) was developed. The present study showed that the axial pullout strength of cement-augmented pedicle screws was increased as the liquid/solid ratio (L/S) of CPN decreased. Mechanical evaluation using ASTM-standard Sawbones showed that the axial pullout force of CPN could reach ∼720 N at the L/S ratio of 0.4 mL/g, while PMMA cannot be injected through the screw. In vitro evaluation in decalcified sheep vertebral models showed that the axial pullout forces of CPN and PMMA were similar, both reaching ∼800 N. The excellent anti-pullout property of CPN clearly suggests its potential for replacing PMMA in the application of cannulated pedicle-screw fixation, worth further study and development for clinical uses.