Knee joints

HDPE by itself is a safe plastic material on account of its chemical inertness and lack of toxicity. Consequently, film and containers made from HDPE are used on a large scale in food and dmg packaging. Moreover, HDPE has been used in prosthetic devices including hip and knee joint replacements (122). 

Another widely used surgical procedure is knee replacement. In this operation the natural components of the knee joint are replaced with an artificial femoral component made of metal that interfaces with a tibial plateau made of ultra-high molar mass poly(ethylene). Implantation of these joints is becoming more widespread, though the demand for them is not as great as for hip replacement. 

Data on the biocompatibility of gelatin microspheres is extremely limited. Drug-free microspheres elicited no untoward effects when injected intravenously into mice over a 12-week period (159). When albumin microspheres were injected repeatedly into the knee joints of rabbits, pronounced rapid joint swelling occurred after the second and subsequent injections. By comparison, no swelling occurred when gelatin microspheres were administered (160). 

Figure 1.1 A typical e.s.r. spectrum of knee-joint synovial fluid obtained from a patient with rheumatoid arthritis. The signals detectable have g values that correspond to the nitrosylhaemoglobin adduct (gi = 2.083, 02 = 2.040 and gs = 2.003).

Typical spectra obtained are shown in Fig. 1.2. Moreover, substantial radiolytically-mediated elevations in the concentration of serum formate, arising from the oxidation of carbohydrates present by OH radical, were also detectable. In addition to the above modifications, 7-radiolysis of inflammatory knee-joint synovial fluid generated an oligosaccharide species of low molecular mass derived from the radiolytic fragmentation of hyaluronate as outlined in the previous section dealing with oxidative damage to carbohydrates. The... 

Figure 1.7 Typical zero-order and corresponding second-derivative electronic absorption spectra of ethanol-reconstituted lipid/chloroform extracts of autoxidized model polyunsaturated fatty-acid compounds and inflammatory synovial fluid obtained after (1) reduction with NaBH4 and (2) dehydration with alcoholic H2S04- (a) Methyl linoleate subsequent to autoxidation in air at ambient temperature for a period of 72 h (—), or exposure to a Fenton reaction system containing EDTA (5.75 x 10 mol/dm ), H2O2 (1.14 X 10 mol/dm ) and Fe(ll) (5.75 x IO mol/dm ) as an aqueous suspension (—) (b) as (a) but with methyl linolenate (c) untreated rheumatoid knee-joint synovial fluid.

Gutteridge, J.M.C. (1987). Bleomycin-detectable iron in knee-joint synovial fluid from arthritic patients and its relationship to the extracellular activities of caeruloplasmin, transferrin and lactoferrin. Biochem. J. 245, 415-421. 

Evidence that oxidized lipids play a role in the pathogenesis of RA comes from studies demonstrating the presence of lipid products arising from radical attack in rheumatoid synovial fluid. This is consistent with oxidation reactions occurring locally in the joint. Lipid peroxidation products that react with thiobarbituric acid (TBARs) have been detected in rheumatoid knee-joint synovial fluid (Rowley et /., 1984). In addition, the... 

Fairburn, K., Grootveld, M., Ward, R.J., Abiuka, C., Kus, M., Williams, R.B., Winyard, P.G. and Blake, D.R. (1992). Tocopherol, lipids and lipoproteins in knee-joint synovial fluid and serum from patients with inflammatory joint disease. Clin. Sci. 83, 657-664. 

Zhang, Z., Winyard, P.G., Chidwick, K., Farrell, A., Pemberton, P., Carrell, KW. and Blake, D.R. (1990). Increased proteolytic cleavage of ai-antitrypsin (ai-proteinase inhibitor) in knee-joint synovial fluid from patients with rheumatoid arthritis. Biochim. Soc. Trans. 18, 898-899. 

The attack is usually monarticular, and the most common sites are the metatarsophalangeal and knee joints. 

CXCR2 CXCL8 or LPS in knee joint Rabbit JV-( 3- (aminosulfonyl) 4-chloro-2-... 

Abrasive wear of polymers has two components material can be removed by the rasping action of a countersurface or it can be sheared off viscoelastically by a countersurface to which it adheres. The precise balance of mechanisms depends on the characteristics of the counterface and the conditions under which the abrasion takes place. Many polymers exhibit excellent wear resistance, which in combination with their low coefficients of friction suit them for applications where lubrication is either impossible or undesirable. We use wear resistant polymers in such diverse applications as bushings in business machines, pump seals, and replacement hip and knee joints. 

Figure 8.3. Morphological features of a normal and rheumatoid joint (a) the essential features of a healthy synovial joint (e.g. a knee joint) (b) the pathological features of a joint of a patient with rheumatoid arthritis.

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