Biodegradable thermoplastic polyurethane composites as potential plating systems in pediatric facial fractures

Due to the rapid growth of facial bone in the pediatric age group, the use of metallic plates would require a second surgical intervention to remove it. The alternative is biodegradable plating systems which are safe but not without complications, including learning curve, decreased stability, cost, and infection. The addition of hydroxyapatite to the synthesized thermoplastic polyurethane (TPU) may affect its structural and morphological properties. Hydroxyapatite is the inorganic part of the bone that is used as reinforcement in many applications. Plate systems comprising composites including hydroxyapatite (u-HA) particles have been developed for clinical use due to their osteoconductive capacity. The effects of hydroxyapatite addition on thermoplastic 'polyurethane's degradation, thermal, structural, and morphological characteristics were examined. This work aims to find an alternative material that can replace the commercial system used nowadays in bone fixation (made either from l-lactide or d-lactide) and overcome its disadvantages such as late degradation tissue response and foreign body reaction. The H12MDI based thermoplastic polyurethane was prepared using 12% HS 50:50 BD-Poly D, L-lactide -co-glycolide, then the composites were prepared by the addition of 3 and 15% of hydroxyapatite, respectively. The properties of the polymer and its composites have been characterized by Fourier transform spectroscopy (FTIR), carbon nuclear magnetic resonance (C13 NMR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and In vitro degradation analysis. It was found that the TPU is semi-crystalline and porous. The melting point and the decomposition temperature of the composites increased with the addition of HA compared to the pure TPU. with incubation in the buffer for 45 and 90 days. The melting point was found to be increased for the polymer as well as for the composites. SEM analysis showed that the polymer is porous, and the filler fills these pores in the composites, increasing its melting point and making the surface smoother. X-ray test showed that the crystallinity of the polymer raised with the addition of the filler. Regarding the degradation, the TPU showed a better degradation rate than the composites as it lost around 30%of its mass after two months only, while the composites lost about 10%. It was confirmed that the synthesized TPU-HA composite could be a promising candidate for bone repair systems