Metals for bone implants: safety, design, and efficacy

Abstract

Like most bone deficits, mandibular segmental defects may result from surgical reconstruction due to congenital deformity, tumor resection, other pathologies, senescence, trauma, or infection. The goals of mandibular reconstruction are to restore the mandible's function and normal appearance. Clinical methods to restore the mandible typically rely on bone replacement using some combination of bone tissue transfer and metal implants. This paper reviews the safety, design, and efficacy of metal implants in general and specifically for the repair of mandibular segmental defects. These problems include implant incorporation, implant failure mechanisms (e.g., stress concentration, stress shielding), corrosion and toxicity, infection, and muscle re-attachment. Finally, this paper presents the use of porous nickel-titanium (NiTi) implants for the repair of skeletal defects through the example of mandibular segmental defects. Resorbable magnesium, and porous and non-porous NiTi, immobilization hardware are also discussed. These materials provide new options which may better match the material properties, and if they can be 3D printed, better match the shape of surrounding host tissue. These advances might reduce engrafted bone and metal implant failure and restore musculoskeletal function for the long term. Patient-specific hardware and grafting strategies might prove to be useful tools in determining both the patient's appearance and functional outcome following reconstructive musculoskeletal surgery.

Innovative Options for Bone Metastasis Treatment: An Extensive Analysis on Biomaterials-Based Strategies for Orthopedic Surgeons

“…Generally, these metals show good biocompatibility because of the non-toxic nature of released ions and sufficient strength to support bone tissue ingrowth ( Heiden et al, 2015 ; Prasad et al, 2017 ). Among these biodegradable metals, Mg is particularly interesting; in fact, it shows high tensile strength, relatively low Young’s elastic modulus and relatively low density compared to other metals, and similar properties to that of cortical bone, potentially reducing stress shielding related risks, typical of titanium (Ti) and other high-strength metals ( Shayesteh Moghaddam et al, 2016 ; Prasad et al, 2017 ; Zhao et al, 2017 ; Minnath, 2018 ). Thanks to these mechanical properties, Mg is mostly used to build bone fixation devices (e.g., pins, screws, rods and plates) and more recently, load-bearing devices in combination with other metals such as SSt or Ti.…”

“…Thanks to these mechanical properties, Mg is mostly used to build bone fixation devices (e.g., pins, screws, rods and plates) and more recently, load-bearing devices in combination with other metals such as SSt or Ti. The degradation kinetics of Mg implants can be adjusted through the development of alloys with other non-toxic elements, like calcium (Ca) and zirconium (Zr), or by way of mechanical and chemical surface treatments ( Shayesteh Moghaddam et al, 2016 ; Prasad et al, 2017 ; Zhao et al, 2017 ; Minnath, 2018 ; Bordbar-Khiabani et al, 2019 ). The released Mg 2+ ions positively stimulate osteoblasts and other bone cells activities and proliferation, being beneficial for new bone tissue development and implant fate ( Zhao et al, 2017 ; Ghosh et al, 2018 ).…”

“…Although, poor clinical evidences of NiTi use in orthopedic clinics are currently available, an interesting feature of porous NiTi implants, that could be used to mimic trabecular bone, is their pump-like and capillary behavior that canalize fluids, cells and new growing vessels inside the material’s pores, guaranteeing a greater integration of the whole implant and a contemporary stimulated growth of new bone tissue. This characteristic make porous NiTi also bioactive, in respect of bulk NiTi or other Ti alloys ( Shayesteh Moghaddam et al, 2016 ; Gorgin Karaji et al, 2017 ). Moreover, porous NiTi could be a valid alternative to mitigate stress shielding caused by the excessive stiffness of other Ti alloys plates used in bone fixation applications.…”

Spectroscopic Methods Used in Implant Material Studies

“…Metal implants [24,25], especially titanium-based implants, have taken the major share of the implant market. Owing to the ease of manufacture and relatively low costs they are the number one choice for dental and orthopedic applications, with new advancements being constantly brought to light [25,26].…”

Recent Advances in PolyArylEtherKetones and Their In Vitro Evaluation for Hard Tissue Applications

“…PEEK suffers in this category, as it is a neutral hydrophobic inert polymer with no native motifs for cell binding and growth. (Toth 2012) This is in contrast to typical metal-based implants that have a native surface charge that allows for cell and protein deposition and growth (Shayesteh Moghaddam et al 2016;Gao et al 2017).…”