Hip joint prostheses

In isostatic hot-pressing ( HIP ), sintering or a post-sintering operation is carried out under a high gas pressure (typically 30-100 MPa). This method, like most other sintering methods, was first developed for metals and is used routinely for high-performance turbine blades and hip-joint prostheses. 

After implantation, the surface of the prosthesis is the first component to come into contact with the surrounding biological milieu. Therefore, surface characteristics play an important role in controlling the course of subsequent biological reactions. Antifouling materials are materials that can resist protein adsorption or microbial adhesion [205,206]. Hence, they have potential applications as surface coatings on implantable devices such as heart valves and hip joint prostheses to minimize biofihn formation and subsequent device-associated infections. 

PE-UHMW has been used in fabrication of acetabular cup for hip joint prostheses. 

BS ISO 14242-1 (2002), Implants for surgery. Wear of total hip joint prostheses. Loading and displacement parameters for wear-testing machines and corresponding environmental conditions for test, London, British Standards Institute. 

BS ISO 14242-1 2002 Implants for surgery Wear of total hip-joint prostheses. British Standards Institution. 

Joint sockets for hip joint prostheses, artificial knee prostheses, finger joint implants, sewing material, tendon and ligament replacement, catheter hoses, surgical membranes... 

As regards clinical work, in vitro studies have proved to be very valuable for example, the study of materials and cements for dental work and hip-joint prostheses. One may predict that in vivo studies will emerge. Indeed, having the subject nearly outside the magnet has considerable advantages. For human patients, the question of the safety aspects of the large gradients will need to be addressed. 

Unsworth A. The effects of lubrication in hip joint prostheses. Phys Med Biol... 

Hip joint prostheses Vascular grafts (blood vessel)... 

Bone cement is used to attach joint prostheses to hip and knee joints. The material mainly consists of PMMA powder and the monomer liquid methyl methacrylate. In addition another substance is added to prevent premature polymerisation, e.g. under the influence of light. 

When polytetrafluoroethylene (PTFE) was Introduced in the early 1960 s the life of total replacement hip joints was limited to about three years by the poor wear characteristics of the polymer. When ultra-high molecular weight polyethylene (UHMWPE) replaced PTFE, the rate of penetration of the metallic component into the polymeric component was reduced to such an extent that loosening emerged as a major aspect of prosthetic life. There is, nevertheless, a need to pursue studies of the wear of prosthetic materials to facilitate the development of satisfactory materials which can be used with confidence in long-life prostheses. 

FIGtJRE 45.12 Radiographic appearance (montage) of a modular endoprosthetic replacement. Entire femur, hip joint, and knee joint of the bone tumor patient were replaced with prostheses for a limb salvage. 

FIGURE 19.3 Polymeric prostheses for othopedic applications, (a) Major components of an artificial hip joint, (b) Two examples of artificial cervical disks with polymeric components, (i) ProDisc-C disk with an insert fabricated from UHMWPE. (ii) Bryan disk with a nucleus fabricated from polyurethane. Panel (a) Adapted from Mattel et al. [166] with pmnission from Elsevia-, copyright (2011). Panel (b) Adapted from Link et al. [104] with permission from Elsevier, copyright (2004). 

Firkins P.J., J.L. Tipper, M.R. Saadatzadeh, et al. 2001. Quantitative analysis of wear and wear debris from metal-on-metal hip prostheses tested in a physiological hip joint simulator. Biomed Mater Eng 11 143-157. 

Hip Disarticulation Amputation Prostheses. The Canadian hip disarticulation prosthesis, introduced in the United States in 1954, is still used almost univers ly today. It consists of a foot, a shank, a prosthetic knee, a thigh, a hip joint/bumper/control strap, and a socket (Fig. 33.16). The hip disarticulation socket is essentially a bucket, providing a seat for the ischial tuberosity, medial-lateral stability, suspension, and support for weight bearing. 

Weightman, B., Simon, S., Paul, L.I., Rose, R. and Radin, E.L. (1972) Lubrication mechanisms of hip joint replacement prostheses. Journal of Lubrication Technology (Trans. American Society of Mechanical Engineers) 94, 131. 

This combination of materials has had a profound effect upon the development of surgery for the treatment of Joint disease and prostheses are readily available, not just for the hip joint but also for the knee, ankle, shoulder and other joints. It is the good biological acceptability of UHMWPE coupled with its mechanical properties that has led to this widespread acceptance. In particular, the tribological characteristics appear to be the most satisfactory for use in a metal-polymer combination. Prosthesis designs utilising alumina ceramic also incorporate an acetabular component of UHMWPE in consequence of the low rate of wear observed. 

A useful collection of symposium papers under the general title Corrosion and Degradation of Implant Materials has been published by the American Society for Testing and Materials. " In this, two separate studies of retrieved orthopaedic implants are presentedtogether with an account by Dumbleton " of the literature on the use, primarily in Scandinavia, of polyoxymethylene (Delrin) for compK>nents of total hip and total knee joint prostheses. 

Biomedical Coatings for hip joints, heart valves and other prostheses. DLC is biocompatible and blood compatible. ... 

Polymers are widely used as implant materials because they have physical properties that are similar to those of natural tissues. Examples are long-term and shortterm implants such as blood vessels, heart valves, membranes, mesh prostheses, corneas, tracheal prostheses, dental materials, parts of the nose and ear, knee and hip joints, and others. The synthetic polymers used include polyethylene (PE), particularly ultrahigh molecular weight PE (UHMWPE), poly(ethylene terephthal-ate) (PET), poly(tetrafluoroethylene) (PTFE), polyurethane (PU), and poly(methyl methacrylate) (PMMA). The necessary sterilization before implantation can be performed by y-irradiation, heat (steam), or chemical treatment (ethylene oxide), which should not cause any structural degradation of the polymers. Current challenges in research include the development of biomimetic materials that match both the mechanical and biological properties of their natural counterparts. 

Polyethylene has been used in surgery since the 1950s. Experience shows that polyethylene cannot be used to replace soft tissue, but is a good substitute material for bone tissue (hip joint, pelvic bone). However, the first applications of PE-LD as bone tissue substitute resulted in high material wear. Subsequent developments in polymer synthesis led to a polyethylene with a higher molecular mass (PE-UHMW ultrahigh-molecular polyethylene (M, / = 4 10 g/mol)), that allowed wide application for pelvic prostheses. Table 5.129. 

Blarney J, Rajan S, Unsworth A, Dawber R. Soft layered prostheses for arthritic hip joints a study of materials degradation. J Biomed Eng 1991 13 180-4. 

Tipper J. L., Firkins P. J., Besong A. A., Barbour P. S. M., Nevelos J. et al. (2001), Characterisation of wear debris from UNMWPE on zirconia ceramic, metal-on-metal and alumina ceramic-on-ceramic hip prostheses generated in a physiological anatomical hip joint simulator , Wear,2 di, 120-8. (doi 10.1016/S0043-1648(01)00653-6)... 

Frictional characteristic of the UHMWPE-on-TZP sliding pair of current joint prostheses was also examined in this test for comparison. The TZP used in this test was the same material used in current ceramic joint prostheses and received hot isostatic pressing (HIP) treatment to reduce internal defects and improve the mechanical strength. The surface roughness of the HTOZ and TZP disk specimens measured by the stylus profilometer was 0.01pm (Ra). 

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