Artificial replacement joints

Medicine has made major advances in the past 50 or so years partly by the use of devices to improve patient health. These devices include artificial hearts and pacemakers, machines for artificial kidney dialysis, replacement joints for hips, knees, and fingers, and intraocular lenses. These devices need to survive in sustained contact with blood or living tissue. 

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. 

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. 

That does not exhaust it. On the side of mechanics, the future of IT in everyday life potentially also includes biorobotics (recall that robotics is a current industry term that first appeared in the science fiction novels of Isaac Asimov), and hence more subtle forms of half robotics that mean enhancive replacements of ailing human parts. For many years patients have already been able to have artificial replacement materials, pins, joints, various prosthetics, pacemakers, and artificial hearts. They have also received transplantations and insertions made of natural materials. This trend will doubtless continue to chips and robotic components to restore lost and damaged physiological, neurological and biochemical functions. 

The application of polymeric materials in medicine is a fairly specialized area with a wide range of specific applications and requirements. Although the total volume of polymers used in this application may be small compared to the annual production of polyethylene, for example, the total amount of money spent annually on prosthetic and biomedical devices exceeds 16 billion in the United States alone. These applications include over a million dentures, nearly a half billion dental fillings, about six million contact lenses, over a million replacement joints (hip, knee, finger, etc.), about a half million plastic surgery operations (breast prosthesis, facial reconstruction, etc.), over 25,000 heart valves, and 60,000 pacemaker implantations. In addition, over AO,000 patients are on hemodialysis units (artificial kidney) on a regular basis, and over 90,000 coronary bypass operations (often using synthetic polymers) are performed each year (]J. 

Polydimethylsiloxane Artificial skin, joint replacement, vitreous replacement, artificial heart, breast implants, different t fpes of catheters and cannulae... 

Chamley s design of an artificial hip joint was the product of an evolutionary process between 1958 and 1960 (Charnley 1979). Five design iterations occurred. Chamley s initial "double cup" design in 1958 mimick the natural joint. The acetabulum was replaced with a thin shell of PTFE and femoral head surface was replaced with a PTFE ball, as shown in Figure 4.1, taken of the collection at the Charnley Museum at Wrightington. 

Examples of knee arthroplasty during the 1960s. (A) Walldius hinged knee replacement (B) the Shiers, Walldius, and Guepar hinged knee replacements, superimposed over the anatomy of the knee (reprinted with permission from Walker RS. 1977. Human joints and their artificial replacements. Springfield, IL CC Thomas Publisher) (C) Macintosh tibial plateau and (D) McKeever tibial plateau. 

Walker RS. 1977. Historical development of artificial joints. In Human joints and their artificial replacements. P.S. Walker, Ed. Springfield, IL Charles C. Thomas. 

The book aims to provide a complete coverage of the types of plastics which are now increasingly being used in engineering in applications as diverse as gears, aircraft body construction, micro-electronics and extreme high temperature applications, steel replacement and artificial hip joints. The book also intends to provide a complete review of the use of polymers in engineering. 

The Revision of Total Hip Replacement (RTHR) is a medical standard procedure with an increasing number of cases (e.g.> 22.500 cases in Germany in 2008) [1], Furthermore, the major part of the implanted Artificial Hip Joints (AHJ) is cemented and 5% to 12% of them are replaced after ten years [2, 3], To ensure the fixation of the new implant, the old Bone Cement (BC) has to be completely removed [4], Conventionally, this is manually done by using hammer and chisel. Besides lateral femur windowing may be used to resolve the restricted access to the operation field in the femur cavity. These procedures are highly invasive and complications (e.g. femur cracking, vessel traumata) appear [5]. 

In the private sector, there is a need for engineers in eompanies that research and manufacture medical products such as artificial heart valves, replacement joints and monitoring equipment. 

Problem area Examples Replacement of diseased or damaged part Artificial hip joint, kidney dialysis machine Assist in healing Sutures, bone plates, and screws Improve function Cardiac pacemaker, intraocular lens Correct functional abnormality Cardiac pacemaker Correct cosmetic problem Augmentation mammoplasty, chin augmentation Aid to diagnosis Probes and catheters Aid to treatment Catheters, drains ... 

Blood bags and intravenous solution bags, one-way articles, gloves, band aids Syringes, hoses, packaging material, needles, sewing material Bone cement, intraocular and hard contact lenses, tooth filler material, artificial teeth, joint replacement... 

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