This article provides an overview of how thermal spray technology has adapted to meet the needs of the orthopaedic industry. It includes the challenges facing the development of artificial joints, substrate material selection criteria, thermal spray solutions, and clinical outcomes of thermal spray coatings. The article focuses on plasma thermal spray, which is the technique most often used to make porous titanium and hydroxyapatite (HA) coatings, such as thermal spray titanium, thermal spray HA, solution-precipitated HA, thermal spray chromium oxide, and thermal spray chromium carbide cermet coatings.

This article provides an overview of the fundamentals of tribology. It describes the advantages, disadvantages, and applications of the pin-on-disk method, which is the most commonly used configuration for testing biomaterials and for the reproducible measurement of friction and wear. The article illustrates a practical tribocorrosion setup that allows a user to perform wear tests in corrosive environments under well-defined electrochemical conditions and at controlled temperature. It explains the effect of changes in electrical contact resistance on tribological mode. The article discusses various in vivo environmental conditions in tribological tests. Some typical examples of biomaterials testing are also provided.

Metallography plays a significant role in the quality control of metals and alloys used in the manufacture of implantable surgical devices. This article provides information and data on metallographic techniques along with images showing the microstructure of biomedical orthopedic alloys, including stainless steels, cobalt-base alloys, titanium and titanium alloys, porous coatings, and emerging materials.

Porous coatings are used in the field of joint replacement, particularly in cementless total hip/knee arthroplasty. This article reviews the offerings and biomaterial properties in orthopedic surgery for the contemporary class of highly porous metals. It describes the traditional porous metals/coatings having an open-cell structure, high porosity, and a microstructure resembling that of the cancellous bone. The traditional porous metal/coating includes fiber-metal mesh, cobalt-chromium (CoCr) beads, cancellous-structured titanium, and plasma spray. The article discusses other porous metals/coatings that have been developed due to the limitations of traditional porous metals for numerous open-cell-structured metals, such as titanium-base foams and trabecular metals.

Biomaterials are the man-made metallic, ceramic, and polymeric materials used for intracorporeal applications in the human body. This article primarily focuses on metallic materials. It provides information on basic metallurgy, biocompatibility, chemistry, and the orthopedic and dental applications of metallic biomaterials. A table compares the mechanical properties of some common implant materials with those of bone. The article also provides information on coatings, ceramics, polymers, composites, cements, and adhesives, especially where they interact with metallic materials.

Superalloys are nickel, iron-nickel, and cobalt-base alloys generally used for high-temperature applications. Superalloys are used in aircraft, industrial, marine gas turbines, nuclear reactors, spacecraft structures, petrochemical production, orthopedic and dental prostheses, and environmental protection applications. This article discusses the material characteristics, phases, structures, and systems of superalloys. It describes the processing of superalloys, including primary and secondary melting, deformation processing (conversion), powder processing, investment casting, and joining methods. The article also describes the properties, microstructure, and thermal exposure of superalloys. It further discusses the effects of environmental factors on superalloys, including oxidation and hot corrosion. Protective coatings are also discussed. The article provides information on the mechanical properties and chemical composition of nickel, iron, and cobalt-base superalloys in both the cast and wrought forms.

This article outlines the selection criteria for choosing an implant material for biomedical devices in orthopedic, dental, soft-tissue, and cardiovascular applications. It details the development of various implants, such as metallic, ceramic, and polymeric implants. The article discusses specific problems associated with implant manufacturing processes and the consequent compromises in the properties of functionally graded implants. It describes the manufacturing of the functionally-graded hip implant by using the LENS process. The article reviews four different types of tissue responses to the biomaterial. It discusses the testing methods of implant failure, such as in vitro and in vivo assessment of tissue compatibility.

Physically, tantalum is a dark, blue-gray, lusterless metal that exists in two crystalline forms: an alpha-phase with a body-centered cubic structure, and a brittle beta-phase with a tetragonal orientation. This article tabulates the physical and material properties of tantalum. It discusses the use of tantalum in medical electronics and the advantage of tantalum over stainless steel. The article describes the manufacturing and medical applications of tantalum foam.

This article tabulates materials that are known to have been used in orthopaedic and/or cardiovascular medical devices. The materials are grouped as metals, ceramics and glasses, and synthetic polymers in order. These tables were compiled from the Medical Materials Database which is a product of ASM International and Granta Design available by license online and as an in-house version. The material usage was gleaned from over 24,000 U.S. Food and Drug Administration (USFDA), Center for Devices and Radiological Health, Premarket notifications (510k), and USFDA Premarket Approvals, and other device records that are a part of this database. The database includes other material categories as well. The usage of materials in predicate devices is an efficient tool in the material selection process aiming for regulatory approval.

Physical vapor deposition (PVD) coatings are harder than any metal and are used in applications that cannot tolerate even microscopic wear losses. This article describes the three most common PVD processes: thermal evaporation, sputtering, and ion plating. It also discusses ion implantation in the context of research and development applications.

This article focuses on the directed-energy deposition (DED) additive manufacturing (AM) technique of biomedical alloys. First, it provides an overview of the DED process. This is followed by a section describing the design and development of the multiphysics computational modeling of the layer-by-layer fusion-based DED process. A brief overview of the primary governing equations, boundary conditions, and numerical methods prescribed for modeling laser-based metal AM is then presented. Next, the article discusses fundamental concepts related to laser surface melting and laser-assisted bioceramic coatings/composites on implant surfaces, with particular examples related to biomedical magnesium and titanium alloys. It then provides a review of the processes involved in DED of biomedical stainless steels, Co-Cr-Mo alloys, and biomedical titanium alloys. Further, the article covers novel applications of DED for titanium-base biomedical implants. It concludes with a section on the forecast of DED in biomedical applications.

Total joint replacement in orthopedic surgery can be achieved by excision, interposition, and replacement arthroplasty. This article details the most common materials used in total replacement synovial joints: metals, ceramics, and ultrahigh molecular weight polyethylene (UHMWPE). The principal physical properties and tribological characteristics of these materials are summarized. The article discusses pin-on-disk experiments and pin-on-plate experiments for determining friction and wear characteristics. It explains the use of various types of joint simulators, such as hip joint simulators and knee joint simulators, to evaluate the performance of engineering tribological components in machine simulators. The article concludes with a section on the in vivo assessment of total joint replacement performance.

Implant debris is known to cause local inflammation, local osteolysis, and, in some cases, local and systemic hypersensitivity. The debris can be stainless steel, cobalt alloy, and titanium alloy, and soluble debris obtained due to wear from all orthopedic implants. This article addresses the biologic aspects of implant debris, both locally and systemically. It describes debris-induced local effects, particle-induced proinflammatory responses, and debris-induced systemic effects. The article concludes with a discussion on the four systemic effects of implant debris, namely, neuropathic effects, hypersensitivity effects, carcinogenicity, and general toxicity.

This article discusses the physical metallurgy of cast cobalt alloys with an emphasis on the crystallography, compositions, phases and microstructure, and properties. Cobalt alloys are cast by several different foundry methods. The article describes the argon-oxygen decarburization and continuous casting process. It provides information on castability and quality of the casted alloys. The article details the postcasting treatment, including heat treatment, hot isostatic pressing, and coatings. It summarizes the applications of cast cobalt alloys.

Titanium and its alloys have been used extensively in a wide variety of implant applications, such as artificial heart pumps, pacemaker cases, heart valve parts, and load-bearing bone or hip joint replacements or bone splints. This article discusses the properties of titanium and its alloys and presents a list of titanium-base biomaterials. Titanium components are produced in wrought, cast, and powder metallurgy (PM) form. The article describes forging, casting, and heat treating of titanium alloys for producing titanium components. Typical mechanical properties of titanium biomedical implant alloys are listed in a tabular form. The article presents an overview of the surface-modification methods for titanium and its alloys implants. It concludes with a section on biocompatibility and in vivo corrosion of titanium alloys.

This article provides a summary of the biocompatibility or biological response of metals, ceramics, and polymers used in medical implants, along with their clinical issues. The polymers include ultrahigh-molecular-weight polyethylene, nonresorbable polymer, and resorbable polymers.

This article reviews the concepts considered important for an understanding of the processes used for preparing cobalt-chromium alloy implants, the microstructures resulting from this processing, and the resulting material properties. The review includes solidification of alloys, diffusionless (martensitic) phase transformation as occurs with face-centered cubic to hexagonal close-packed transformation in cobalt-chromium alloys, and stacking faults and twins and their role in this transformation. It also discusses the strengthening mechanisms that are responsible for the mechanical properties of cast and wrought cobalt alloys. The article contains tables that list the commonly used cobalt alloys and their biomedical applications and chemical compositions. It discusses the mechanical and corrosion properties of cobalt alloys, and provides a description of the microstructure of cobalt alloys.