Materials evolution of bone plates for internal fixation of bone fractures: A review

Bone plates play a vital role in bone fracture healing by providing the necessary mechanical fixation for fracture fragments through modulating biomechanical microenvironment adjacent to the fracture site. Good treatment effect has been achieved for fixation of bone fracture with conventional bone plates, which are made of stainless steel or titanium alloy. However, several limitations still exist with traditional bone plates including loosening and stress shielding due to significant difference in modulus between metal material and bone tissue that impairs optimal fracture healing. Additionally, due to demographic changes and non-physiological loading, the population suffering from refractory fractures, such as osteoporosis fractures and comminuted fractures, is increasing, which imposes a big challenge to traditional bone plates developed for normal bone fracture repair. Therefore, optimal fracture treatment with adequate fixation implants in terms of materials and design relevant to special conditions is desirable. In this review, the complex physiological process of bone healing is introduced, followed by reviewing the development of implant design and biomaterials for bone plates. Finally, we discuss recent development of hybrid bone plates that contains bioactive elements or factors for fracture healing enhancement as a promising direction. This includes biodegradable Mg-based alloy used for designing bone screw-plates that has been proven to be beneficial for fracture healing, an innovative development that attracts more and more attention. This paper also indicates that the tantalum bone plates with porous structure are also emerging as a new fracture internal fixation implants. The reduction of the stress shielding is verified to be useful to accelerate bone fracture healing. Potential application of biodegradable metals may also avoid a second operation for implant removal. Further developments in biometals and their design for orthopedic bone plates are expected to improve the treatment of bone fracture, especially the refractory fractures. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.