Joint replacement prostheses

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. 

Applications corrugated pipe, drums, fiber, filters. Implants, Industrial tanks, modifier for resins and rubbers, total joint replacement prostheses ... 

Although crosslinking of UHMWPE has been shown to improve performance in hip-simulator wear tests, mechanical tests condncted on crosslinked material have shown deterioration in several mechanical properties including Young s modnlns, yield stress, ultimate tensile stress, and strain to break. These resnlts appear contradictory, since it is generally believed that the toughness of a polymer correlates with its wear performance. A better understanding of the relationship between the mechanical properties and wear performance of UHMWPE is required for the development of new wear-resistant polymeric components for use in total joint replacement prostheses. 

Wang A, Stark C, Dumbleton JH. Mechanistic and morphological origins of ultra-high molecular weight polyethylene wear debris in total joint replacement prostheses [see comments]. Proc Inst Mech Eng [H] 1996 210(3) 141-55. 

Ainsworth R, Fading G, Bardos D. An improved bearing material for joint replacement prostheses carbon fiber-reinforced UHMW polyethylene. Trans 3rd Soc Biomater 1977 3 119. 

Swanson, S.A.V., Freeman, M.A.R. and Heath, J.C. (1973) Laboratory tests on total joint replacement prosthesis. J. Bone Joint Surg., 55B, 759-773. 

The materials used in a total joint replacement ate designed to enable the joint to function normally. The artificial components ate generally composed of a metal piece that fits closely into bone tissue. The metals ate varied and include stainless steel or alloys of cobalt, chrome, and titanium. The plastic material used in implants is a polyethylene that is extremely durable and wear-resistant. Also, a bone cement, a methacrylate, is often used to anchor the artificial joint materials into the bone. Cementiess joint replacements have mote tecentiy been developed. In these replacements, the prosthesis and the bone ate made to fit together without the need for bone cement. The implants ate press-fit into the bone. 

The principal complication for total joint replacement is infection, which may occur just in the area of the incision or more seriously deep around the prosthesis. Infections in the wound area, which may even occur years after the procedure has been performed, are usually treated with antibiotics (qv). 

Nerves are rarely damaged during the total joint replacement surgery. However, nerve damage can occur if considerable joint deformity must be corrected in order to implant the prosthesis. With time these nerves sometimes return to normal function. 

The acrylic bone cements have been widely used to successful prosthesis in total joint replacements for the last few decades. While the surgical replacement is very successful, the bone cement is often found as a failed material after long-term use. 

Joint Replacement. Frequently the joints in the human body must be replaced because of disease or injury. Hundreds of designs have been used in attempts to replace the wide variety of joints with plastics, ceramics, and metals in many combinations. Most of these attempts have had only limited success, but many joints can now be replaced with a reasonably satisfactory prosthesis and thereby restore much of the normal joint function. Essentially all of the most successful replacement joints use a polymeric material. 

Total joint replacements are permanent implants, unhke those used to treat fractures, and the extensive bone and cartilage removed during implantation makes this procedure irreversible. Therefore, when faced with prosthesis failure and the impossibility to reimplant, the patient will face severe shortening of the extremity, instability or total rigidity of the joint, dif culty in ambulation, and often will be confined to a wheel chair. 

The prosthesis for total knee joint replacement consists of femoral, tibial, and patellar components. Compared to the hip joint, the knee joint has a more complicated geometry and movement biomechanics, and it is not intrinsically stable. In a normal knee, the center of movement is controlled by the geometry of the ligaments. As the knee moves, the ligaments rotate on their bony attachments and the center of movement also moves. The eccentric movement of the knee helps distribute the load throughout the entire joint surface [Burstein and Wright, 1993]. 

Finger joint replacements are divided into three types (1) hinge, (2) polycentric, and (c) space-fiUer. The most widely used are the space-filler type. These are made of high performance silicone rubber (polydimethylsiloxane) and are stabilized with a passive fixation method. This method depends on the development of a thin, fibrous membrane between implant and bone, which allows pistoning of the prosthesis. This fixation can provide only minimal rigidity of the joint [Swanson, 1973). Implant wear and cold flow associated with erosive cystic changes of adjacent bone have been reported with silicone implants [Carteret al., 1986 MaistrelU, 1994]. 

R. Huiskes, Some fundamental aspects of human joint replacement. Analyses of stresses and heat conduction in bone-prosthesis structures, Acta Orthop. Scand. Suppl. 185 (1980) 1-208. 

Evans, E.M., Freeman, M.A.R., Miller, A.J. et al. (1974) Metal Sensitivity as a Cause of Bone Necrosis and Loosening of the Prosthesis in Total Joint Replacement, J. Bone and Joint Surg., 56B (4), 626-642 One of the original articles pointing to a possible problem. Skin test used. 

In the medical praxis, UHMWPE have been used successfully as one half of the bearing couple (against metallic alloys or ceramics) in total hip and total knee joint replacements crosslinked under irradiation [82]. Even y-irradiated UHMWPE at doses higher than 100 kGy presents the incipient ffacmre development [83], the alkyl macroradicals are involved in crosslinking and in a smaller proportion they promote oxidation [84, 85]. The prosthesis manufactures by the irradiation of UHMWPE have long durability, because the application of radiation treatment induces an increased crystallinity and promotes sterilization in the whole volume of material. 

An advanced approach to this use of 3D information is the construction from the patient s data of a customised prosthesis (Ray et al. 1993). This allows a replacement prosthesis to be adapted perfectly to the patient s own anatomy and has been developed for replacement of the temporomandibular joint in particular (Worrall and Christensen 2006). 

J. and R. Judet First biomechanically designed femoral head replacement prosthesis. First plastics (PMMA) used in joint replacements... 

Bone absorption around screw or screw loosening for total joint replacement has been studied as one of failure factor. Stress concentration around the fixed screw seems to be an index to evaluate a possibility of failure after the TMJ prosthesis replacement. Therefore, the distribution of the fixed screws in the model C was evidenced more suitable for decreasing the stress concentration around screw holes. In addition, the distribution of the fixed screws at the model A could be better to prevent screw fracture due to less magnitude in peak stress concentration. Analyzing the different types of positions in the screw insertion showed that the magnitudes of peak stress in three condylar prostheses were not significant difference, but the regions of the peak stress were trivial dissimilar in the three FE models. 

Since PMMA has mechanical properties that are similar to bone, its use in joint replacement devices may allow a more physiologic transfer of loads from the prosthesis to the remaining bone, which may in turn reduce stress-shielding and the resulting bone loss. PMMA stabilizes implants within the surrounding bone, reducing unwanted micromotions and can act as a load damper [5]. 

On the other hand, survivorship alone does not fully capture the clinical performance of UHMWPE in the knee. Surface damage and wear of the UHMWPE insert are also important metrics of clinical performance of knee arthroplasty. If a knee prosthesis survives the first 10 years of implantation, wear behavior of the insert plays an increasing role in the longevity of the joint replacement. In the following sections, we describe the survivorship of TKA, as well as the assessment of wear and surface damage in knee arthroplasty. 

Kudo H, Iwano K. Total elbow arthroplasty with a non-constrained surface-replacement prosthesis in patients who have rheumatoid arthritis. A long-term follow-up study. J Bone Joint Surg Am 1990 March 72(3) 355-62. 

---