Artificial hip

Artichokes Article of manufacture Artifact conservation Artificial colors Artificial flavorings Artificial hip Artificial intelligence... 

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. 

Semlitsch, M., and Willert, H. G., Properties of Implant alloys for Artificial Hip Joints , Medical and Biological Engineering and Computing, 18, 511-520 (1980)... 

Postmastectomy reconstruction Artificial hip. knee 18. Artificial finger, toe joints Tom ligaments Natural-action Seattle Foot Aorta... 

In a typical hip replacement operation, the top of the thigh bone is removed and a cavity is drilled along the direction of the long axis of the remaining bone. A metal prosthesis is placed in this cavity and secured in place with PMMA cement. In the pelvic girdle a plastic cup is fitted to act as the seat of the new, smaller hip joint. This cup is made of ultra-high molar mass poly (ethylene) and is also secured in place with PMMA cement. The components of an artificial hip joint are shown in Figure 10.1. 

The success of hip replacements has been greatly advanced by major development in the biomaterials for orthopedic devices. What aspects of chemistry must be considered in designing an effective artificial hip ... 

Successful applications of materials in medicine have been experienced in the area of joint replacements, particularly artificial hips. As a joint replacement, an artificial hip must provide structural support as well as smooth functioning. Furthermore, the biomaterial used for such an orthopedic application must be inert, have long-term mechanical and biostability, exhibit biocompatibility with nearby tissue, and have comparable mechanical strength to the attached bone to minimize stress. Modem artificial hips are complex devices to ensure these features. 

Figure 15.1.1 A schematic diagram of the two components of an artificial hip the stem or femoral component and the socket or acetabular component.

A Patient s Guide to Artificial Hip Replacement. Randale Sechrest, MD, Medical Multi-media Group. http //www.medicaImultimediagroup.com/pated/joints/hip/ hip replacement.html... 

A closely related challenge is the design of materials that interact with cells or living tissues to promote desired biological responses. Such responses might be cell attachment, cellular differentiation and organization into functional tissue, or promotion of in-growth of bone into an artificial prosthesis such as an artificial hip. 

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. 

These include attempts by surgeon M.N. Smith-Petersen in 1925, Robert and Jean Judet in 1938, and Dr. Edward J. Haboush in 1953. However, the first successful hip prosthesis was not developed until 1961 when Dr. Chamley made a hip prosthesis out of a high molecular weight polyethylene cup. Today, artificial hip joints are implanted in over 200,000 people each year in the USA (Ratner, 2004). 

This photo shows the components of an artificial hip joint. 

AMMONIUM HALIDE, 293 ANISOTROPY, 38 57 153 174 406 ANNULAR DIE, 311 ANTIOXIDANT, 385 ANTI-SLIP PROPERTIES, 208 ANTISTATIC PROPERTIES, 91 302 426 427 444 447 450 APPEARANCE, 124 186 241 293 AQUEOUS DISPERSION, 103 ARGON, 185 233 235 321 339 433 ARRHENIUS FACTOR, 243 ARTIFICIAL HIP, 52 ARTIFICIAL KNEE, 52 ARTIFICIAL SEAWEED, 455 ASPECT RATIO, 314 419 ATOMIC FORCE MICROSCOPY, 149... 

While chains having molecular weights of a few thousands only form brittle waxes, polyethylenes having molar masses of above hundred thousand show much better mechanical properties. They can be processed into films, pipes, and other performance products. When molar mass is further increased up to several millions, even higher impact strengths and abrasion resistances are achieved which enable these materials to be used in heavy-duty applications like skating floors and artificial hips. 

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. 

Enhancing the wear resistance of polymers (e.g., ultra-high-molecular-weight polyethylene-UHMWPE-used for in vivo implants, such as artificial hip joints). ... 

In the 1960s the first heart valve was replaced. At approximately the same time the Englishman Sir John Charnley developed a bone cement on the basis of PMMA. Nowadays an improved version of this cement is still used, e g. to secure an artificial hip joint to the upper leg. 

Because the shafts of artificial hips joints fractured quite often, much research was aimed at improving the solidity of the materials in the 1970s. Nowadays much better materials are available, notably titanium alloys. 

Many kinds of artificial hip joints are available commercially, but they all consist of the same parts, i.e. a metal stem or shaft, usually made of a titanium alloy and a ceramic head of aluminium or zirconium oxide. The production of the ceramic head starts with a powder and ends with the sintering process. The heat treatment will cause the head to shrink. After production, the head is thoroughly tested, e.g. on its spherical shape and surface roughness. 

The October 1996 issue of the Dutch magazine Natuur Techniek makes mention of a research of the University of Bristol, Great Britain into the effects of implanting artificial hip joints and knees into the body. This research showed that metal particles and pieces of plastic, cement and polymers are gradually released from the artificial joints. Such particles were found in the neighbourhood of joints and lymph nodes. However, they were also present in the bone marrow, the spleen and the liver. The more artificial limbs are exposed to loads, the more particles will be released. So far there are no indications of health hazards, but it is not possible to predict long term effects. 

Moro T, Takatori Y, Ishihara K, Nakamura K, Kawaguchi H. Frank Stinchfield Award grafting of biocompatible polymer for longevity of artificial hip joints. Clinical Orthopaedics and Related Research 2006, 453, 58-63. 

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