Hip implants

Fig. 11. Three views of a hip implant for joint replacement (a) insertion of the implant into the femur (b) implant in place and (c) femur and implant...

The next advance in total hip arthroplasty came with the development of various porous surface treatments which allow bone tissue to grow into the metal porous coating on the femoral stem of the hip implant and on the acetabular component of the total joint replacement. These developments arose because of patients who were not able to tolerate cemented implants because of allergies to the cement, methylmethacrylate. More youthflil patients are better served by a press-fit implant as well. Figure 12 shows the difference between textured and beaded surface-treated orthopedic prostheses. 

Hydroxyapatite (HA) coating on the surface of the hip stem and the acetabular cup is the most recent advancement in artificial hip joint implant technology. This substance is a form of calcium phosphate, which is sprayed onto the hip implant. It is a material found in combination with calcium carbonate in bone tissue, and bones can easily adapt to it. When bone tissue does grow into HA, the tissue then fixes the hip joint implant permanently in position. These HA coatings are only used in press-fit, noncemented implants. 

Total hip implants of the nature described have hospital Hst prices ia the range of 5000— 8000. Fully custom-made implants cost approximately 10,000. The low end basic total hip implant is forged or cast stainless steel, cemented ia place, one size fits all, and costs 1000. 

Biomedical. Heart-valve parts are fabricated from pyrolytic carbon, which is compatible with living tissue. Such parts are produced by high temperature pyrolysis of gases such as methane. Other potential biomedical apphcations are dental implants and other prostheses where a seal between the implant and the living biological surface is essential. Plasma and arc-wire sprayed coatings are used on prosthetic devices, eg, hip implants, to achieve better bone/tissue attachments (see Prosthetic and BiOLffiDiCALdevices). 

Other clinical studies have been focused on the artificial tympanic membrane application, ventilation mbes, an adhesion Barrier, elastic bioactive coatings on load-bearing dental and hip implants, and also for wound healing purposes. ... 

ASTM specifications for, 24 862-864 dental applications, 8 311-314 defects in, 24 855 fatigue behavior of, 24 841, 845 hip implants, 3 734 mechanical properties of, 24 841, 843-844t... 

The artificial hip has been used to replace the human hip because the hip is easily worn out over a lifetime of mechanical stress resulting from normal activity. The first artificial hip implant was made by Thermistokles Gluck in 1891 in Berlin. This implant made use of a femoral head of ivory fixed with plaster of paris and glue (Gluck, 1890, 1891). The results were not good due to severe infection problems and adverse foreign body tissue reactions. To develop better hip replacement prosthesis, many materials and procedures were examined between 1925 and 1953. 

Siloxane-containing devices have also been used as contact lenses, tracheostomy vents, tracheal stents, antireflux cuffs, extracorporeal dialysis, ureteral stents, tibial cups, synovial fluids, toe joints, testes penile prosthesis, gluteal pads, hip implants, pacemakers, intra-aortic balloon pumps, heart valves, eustachian tubes, wrist joints, ear frames, finger joints, and in the construction of brain membranes. Almost all the siloxane polymers are based on various polydimethylsiloxanes. 

In normal motion, the load exerted on the hip joint is 2.5 times body weight, (a) Estimate the corresponding stress (in MPa) on an artificial hip implant with a cross-sectional area of 5.64 cm in an average-sized patient, and (b) calcnlate the corresponding strain if the implant is made of Ti-6A1-4V alloy. Clearly state yonr assnmptions and sonrces of data. 

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... 

The elements of groups 3 through 12 are all metals that do not form alkaline solutions with water. These metals tend to be harder than the alkali metals and less reactive with water hence they are used for structural purposes. Collectively they are known as the transition metals, a name that denotes their central position in the periodic table. The transition metals include some of the most familiar and important elements—iron, Fe copper, Cu nickel, Ni chromium, Cr silver, Ag and gold, Au. They also include many lesser-known elements that are nonetheless important in modern technology. Persons with hip implants appreciate the transition metals titanium (Ti), molybdenum (Mo), and manganese (Mn), because these noncorrosive metals are used in implant devices. 

The anamnesis of a hip implant starts with pain due to which the patient is limited in his or her movements. The causes are usually arthrosis, rheumatoid arthritis, a trauma or deviations in form like dysplasia. 

Occasionally, reactions to titanium can occur at a distance from a hip implant, probably because small particles of titanium become detached and enter the system. 

Xie, J. et al., Novel hydroxyapatite coating on new porous titanium and titanium-tlDPE composite for hip implant, Surf. Coat. Technol., 202, 2960. 2008. 

Metal Titanium alloys (Ti6A14V, Ti6A17Nb, Ti2, Ti4, Ti6A17Nb, Til3Nbl3Zr, Til2Mo6Zr) Shafts for hip implants, knee implants, coronary stents Bioinert Niinomi (2008) and Elias et al. (2008)... 

Ceramics Hydroxyapatite Bone cavity fillings, ear implants, vertebrae replacement, hip implant coatings, bone scaffolds Bioactive Cao and Hench (1996) and Lobel and Hench (1998)... 

The mechanical performance of femoral heads and acetabular cups made from alumina have been the subject of intense research and development effort as it is crucial for the longevity of the endoprosthetic hip implant. Hence, the failure probability of these ceramic construction parts has been investigated and expressed by the Weibull probability density function. As safe design of... 

Clarke, I.C., Manaka, M., Green, D.D., Kim, Y.H., Ries, M., Sedel, L., Sugano, N., Ben-Nissan, B., and Gustafson, A. (2003a) Current Status of Zirconia Total Hip Implants - Clinical and Laboratory Studies, American Academy of Orthopaedic Surgeons, New Orleans, LA, p. SE203. 

Bohler, M., Kanz, F., Schwarz, B., Steffan, I., Walter, A., Plenk, H. Jr., and Knahr, K. (2002) Adverse tissue reactions to wear particles from Co-alloy articulations, increased by alumina-blasting particle contamination from cemendess Ti-based total hip implants. A report of seven revisions with early failure. /. Bone Joint Surg. Br., 84-B, 128-136. 

Bergmann G. et al.. Frictional Heating of Total Hip Implants, Part 1 Measurements in Patients, Part 2 Finite Element Study, J. Biomechanics, 34, 421 and 429, 2001. 

H. Bougherara, R. Zdero, A. Dubov, S. Shah, S. Khurshid, E.H. Schemitsch, A preliminary biomechanical study of a novel carbon-fibre hip implant versus standard metallic hip implants, Med. Eng. Phys. 33 (2011) 121-128. 

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