3D bioactive composite scaffolds for bone tissue engineering.

Advanced bioceramics have played integral roles in treatment modalities for damaged or diseased human joints and osseous defects. This paper reviews the uses and properties of ceramics and ceramic coatings variously employed as articulation devices in hip, knee, shoulder, and other joints, either as self-mated surfaces, or against polyethylene (both conventional and highly cross-linked versions), or for osseous- fixation as arthrodesis devices, bone scaffolds, and substitutes in the spine or extremities. The modern uses of oxide and non-oxide materials in these applications will be discussed, followed by an assessment and comparison of their mechanical and physicochemical properties. Recent developments in new bioceramic materials and composites along with advanced processing and testing methods are presented. Advanced bioceramics and coatings are expected to have increasing use in orthopaedics because of their unique combination and range of properties including strength and toughness, hardness and wear resistance, biocompatibility, bacteriostasis, and osseointegration.

Ceramics and Ceramic Coatings in Orthopaedics

Background: Implant-related infections are caused by adhesion of bacteria to the surface of biomaterials. In this in vitro research, we evaluated the ability of Staphylococcus epidermidis (ATCC35984) to adhere to the surface of solid biomaterials at different levels of roughness below 30 nm Ra and investigated the minimum level of roughness required to promote bacterial adhesion on five kinds of biomaterials: oxidized zirconium-niobium alloy (Oxinium), cobalt-chromium-molybdenum alloy (Co-Cr-Mo), titanium alloy (Ti-6Al-4 V), commercially pure titanium (Cp-Ti) and stainless steel (SUS316L), samples of which were categorized into a fine group and a coarse group according to surface roughness. The test specimens were physically analyzed and the viable bacterial density of the adhered bacteria was quantitatively determined (n=20). Results: The amount of bacteria that adhered to the biomaterials in the coarse group was higher than those in the fine group. Oxinium, Ti-6Al-4 V and SUS316L in particular demonstrated statistically significant differences between the two groups (P<0.05). Of the materials, the Co-Cr-Mo specimens exhibited significantly lower amounts of adhered bacteria than the Ti-6Al-4 V, Cp-Ti and SUS316L specimens in the fine group. Similarly, the Co-Cr-Mo specimens in the coarse group exhibited significantly lower values than the other four materials. Conclusions: These results suggest that minimum level of roughness affecting initial bacterial adherence activity differs according to the type of biomaterial used, and that even a surface roughness of below 30 nm Ra in Oxinium, Ti-6Al-4 V and SUS316L can promote bacterial adhesion. Relative hydrophobic Co-Cr-Mo surfaces were less susceptible to bacterial adherence.

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Effect of surface roughness of biomaterials on Staphylococcus epidermidis adhesion.

Aseptic loosening of femoral components – A review of current and future trends in materials used

Microstructure, corrosion behavior and cytotoxicity of Zr-Nb alloys for biomedical application

More demanding performance expectations for total joint arthroplasty are driving the development of alternative bearing materials. Oxidized zirconium was developed as an alternative to cobalt-chromium alloy for knee and hip femoral components in order to reduce wear of the polyethylene counterface and to address the needs of metal-sensitive patients. Oxidation in high temperature air transforms the metallic Zr-2.5Nb alloy surface into a stable, durable, low-friction oxide ceramic without creating the risk for brittle fracture associated with monolithic ceramic components. This presentation reviews aspects of this technology with a historical perspective, including standards for the zirconium alloy, non-medical applications for oxidized zirconium, and previous orthopaedic applications for zirconium. Manufacturing processes for oxidized zirconium components are described, beginning with refining of the zirconium from beach sand, to producing the alloy ingot and bar, to fabricating the component shape, and finally to oxidizing the surface and burnishing it to a smooth finish. Conditions are described for producing the oxide with excellent integrity, which is nominally 5 µm thick and predominantly monoclinic phase. The metal and oxide microstructures are characterized and related to the mechanical properties of the components and durability of the oxide. Laboratory hip and knee simulator tests are reviewed, which indicate that oxidized zirconium components reduce wear of the polyethylene counterface by 40–90 % depending on test conditions. As evidenced by promising early clinical experience, oxidized zirconium components have characteristics that provide an alternative to conventional cobalt-chromium components with an interchangeable surgical technique, while providing the potential for superior performance.

R Graham

Papers

Creation of Oxidized Zirconium Orthopaedic Implants