To meet the needs of clinical medicine, bone tissue engineering is developing dynamically. Scaffolds for bone healing might be used as solid, preformed scaffolding materials, or through the injection of a solidifiable precursor into the defective tissue. There are miscellaneous biomaterials used to stimulate bone repair including ceramics, metals, naturally derived polymers, synthetic polymers, and other biocompatible substances. Combining ceramics and metals or polymers holds promise for future cures as the materials complement each other. Further research must explain the limitations of the size of the defects of each scaffold, and additionally, check the possibility of regeneration after implantation and resistance to disease. Before tissue engineering, a lot of bone defects were treated with autogenous bone grafts. Biodegradable polymers are widely applied as porous scaffolds in bone tissue engineering. The most valuable features of biodegradable polyurethanes are good biocompatibility, bioactivity, bioconductivity, and injectability. They may also be used as temporary extracellular matrix (ECM) in bone tissue healing and regeneration. Herein, the current state concerning polyurethanes in bone tissue engineering are discussed and introduced, as well as future trends.

Biocompatibility, bioactivity, bioconductivity and injectability are the most valuable features of biodegradable polyurethanes for orthopaedic applications. Injectable biomaterials may be used in bone tissue engineering for minimally invasive therapies and other medical applications. Polyurethane composites have been synthesized with concentration of btricalcium phosphate in the range of 0-30 wt%. Incorporation of b-tricalcium phosphate leads to an increased glass temperature of soft segments while a decrease of glass temperature was observed for hard segments. Moreover, addition of b-tricalcium phosphate caused an increase in the thermal stability of polyurethane matrix. Porosity has ranged between 27 and 53%. The mechanical and thermal properties of the polyurethane/b-tricalcium phosphate composite samples have been investigated. In vitro degradation tests have been carried out in water, Ringer's solution and phosphate buffered saline. After 2 weeks incubation in simulated body fluid, scanning electron microscopy observations showed the presence of an inorganic phase deposition which might indicate good bioactivity of the composites. The relationships between their properties and bone regeneration quality were discussed as the composites demonstrate vast potential to be used as injectable scaffolds for bone repair.