Metal implant

Breakage of an implanted joint is rare. Breakage occurs when the bone flexes and the metal implant does not flex as much, thereby exceeding its mechanical fatigue point causing the implant to break or crack. A revision joint replacement operation is necessary if breakage occurs. 

The SSMS point-to-plane surface technique has been shown to be particularly useful in the survey analysis of epitaxial films, heavy metal implant contamination, diflRision furnace contamination, and deposited metal layers. 

Metallic devices have been used to repair and replace parts of the human body for centuries. Archaeological evidence clearly indicates that surgical procedures were performed in several ancient civilisations. The use of surgical metal implants in humans was first recorded in 1562 when a gold prosthesis was used to close a defect in a cleft palate. ... 

Ideally, a metallic implant should be completely inert in the body. However, that is rarely the case. The body environment is extremely hostile to all foreign materials and therefore, the effect of the environment on... 

Reaction of the host tissue to metallic implants is affected by many factors including shape and size of the implant, movement between the implant and tissue, extent of corrosion attack, general degradation of the implant, and the biological activity of the resulting by-products of corrosion or degradation. 

Galante, J. and Rostoker, W., Corrosion Related Failures in Metallic Implants and Experimental Study , Clinical Orthopaedics and Related Research, 86, 237-244 (1972)... 

Other coating processes involving fluoridated apatite have been investigated to improve the long-term adhesion and promote osteointegration of cementless titanium-based metal implants pulsed laser deposition, electron beam deposition and ion beam sputter deposition techniques, and sol-gel methods, for example. They lead to fluor-containing calcium phosphates (apatites in most cases) with different compositions and crystallinity states. 

Metallic biomaterials (metals such as Ti or its alloys and others) are used for the manufacture of orthopaedic implants due to their excellent biocompatibility with respect to electrical and thermal conductivity and their mechanical properties, e.g., for hard tissue replacement such as total hip and knee joints, for fracture healing aids such as bone plates and screws or dental implants. For example, Co-Cr-Mo alloys are employed for metal-on-metal hip bearings in total joint replacements. Problems with implants occur because of ion release in patients with metal implants. To control this ion release, the ultratrace determination of Co, Cr and Mo in the blood (or serum) and urine of patients with Co-Cr-Mo alloy hip implants is carried out routinely in the author s laboratory. The trace metal determination of Co, Cr and Mo in complex matrices such as urine and blood by ICP-MS is not trivial due to the low concentrations expected in the sub-ngmF1 range, the possible danger of contamination during sample collection, sample preparation and the... 

In the field of bioceramics, paragraph 11.6, coatings of synthetic bone are applied to metal implants in order to ensure a better attachment to the body s bone. 

There are countless applications possible. Nowadays, it is possible to replace human parts with synthetic materials virtually anywhere in the body. Table 11.6.1 lists a number of examples of plastic and metal implants. Ceramic implants are not mentioned here because they will be discussed elaborately in this chapter. 

Metals and metal alloys are not without their disadvantages as hiomaterials, however. Although they tend to he quite stable in a biological system, they are not completely inert. They do react to some extent, meaning the metal implant can deteriorate over time. A number of methods have been devised to reduce this problem. For example, metal implants are sometimes attached to existing bone with a ceramic material, which acts as a buffer between the metal and the living material in hone. 

LahannJ, Klee D, Pluester W, Hoecker H, Bioactive immobilization of r-hirudin on CVD-coated metallic implant devices. Biomaterials 2001 22(8) 817-826. 

Hyperthermia and thermoablation have been accomplished using capacitive or inductive coupling of rf fields (10-100 MHz), microwaves (> 300 MHz), ultrasound, lasers or external heat [171-177]. Macroscopic metal implants of Cu and other high-conductivity metals have been used to induce eddy-current heating. The absorbed power per mass is called the specific absorption rate (SAR), which can be expressed as... 

The distribution of uranium metal implanted in muscle has been investigated in rats (Pellmar et al. 

Carbon fibers, which are relatively inert under physiological conditions, are selected particularly to enhance the mechanical properties of various biomedical materials, such as their incorporation in bone cement [127]. Metal implants for total hip joint replacements do not match the mechanical properties of human bone, and epoxy-graphite implants may have better properties [128]. 

Complications from the use of metal implants and prostheses can arise because of biochemical and histological reactions to some of the materials used (SEDA-22, 250). These include titanium, stainless steel (10-14% nickel, 17-20% chromium), and cobalt chrome alloys (27-30% chromium, 57-68% cobalt, and up to 2.5% nickel). AU of these metals can produce sensitization or ehcit toxic reactions when they are solubilized and come into contact with tissues it can be difficult or even impossible to differentiate between hypersensitivity and toxic reactions. 

Attempts continue to predict metal sensitivity in the individual patient so that the choice of material can be made accordingly. In vitro tests for metal allergies have been developed on the basis of lymphokine (MIF) release from sensitized T lymphocytes exposed to metal-protein complexes (11). About 6% of patients without a previous metal implant had positive reactions to nickel, chromium, or cobalt. However, it is still not clear whether such a positive reaction is a reliable predictor of clinical problems. In practice few patients have either local or systemic reactions when symptoms occur and other causes are ruled out, the implant should be removed. Some workers recommend removal of an implant whenever there is both a positive MIF test and a positive skin test, even in the current absence of a serious reaction. Allergic dermatitis will clear up as soon as the metal has begun to be cleared from the tissue. The type of metal and the amount released into the tissue will affect the time taken for the disappearance of toxic dermatological phenomena. 

Nickel plays a major role in sensitization of patients. Even the small amount present in cobalt chrome alloys often suffices to elicit allergic reactions. Reactions to cobalt are more generally toxic in nature (3). An increased rate of allergy to cobalt and nickel has been found in those patients bearing metallic implants who have developed bone infection in the surroundings of osteosynthesis material. 

Kanerva L, Forstrom L. Allergic nickel and chromate hand dermatitis induced by orthopaedic metal implant. Contact Dermatitis 2001 44(2) 103-4. 

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