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PubMed · 6882161

Uncemented acetabular replacement.

P A Ring
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Abstract

An uncemented Polyethylene acetabular component has been developed using a cup of conical outer configuration locked in position with the Freeman osseous peg. This cup is available in four sizes and is normally used with an uncemented femoral component. During the last 3 years 875 implants of this sort have been inserted and the results in these patients who are between 1 and 3 years post-operatively have been compared with the results in 236 replacements of a similar configuration but secured with bone cement in the usual way. The two groups have been demonstrated to be comparable in pre-operative diagnosis, age and sex. The results using the uncemented articulation are broadly the same as those using the cemented joint during the period of study but the acetabular component in 30% of the cemented joints showed a zone of demarcation between cement and bone whereas only one of the uncemented acetabular components showed similar radiological changes. The examination of the radiographs of the uncemented group suggests that the pelvic bone responds favourably to the stresses which are imposed upon it provided that the centre of the joint movement is relocated in the anatomical position, under these circumstances bone will usually build up to support the cup in a dysplastic acetabulum and in the floor of a central protrusion.

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AcetabulumAdultAgedBone CementsFemaleHip ProsthesisHumansMaleMethodsMiddle AgedRadiographyJournal Article

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P A Ring. 1983. Uncemented acetabular replacement.. https://doi.org/10.1007/bf00379935

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PubMed1999

Effect of molecular weight, calcium stearate, and sterilization methods on the wear of ultra high molecular weight polyethylene acetabular cups in a hip joint simulator.

Orthopaedic surgeons must currently choose from several types of ultra high molecular weight polyethylene acetabular cups that differ in their material properties and in the methods used for their sterilization. Information on the wear resistance of these different cups may help in the selection process. This study included two separate tests for wear run on a hip simulator to investigate the effect of molecular weight, calcium stearate, and sterilization methods on the wear resistance of ultra high molecular weight polyethylene acetabular cups. Test 1 revealed nearly identical wear rates for acetabular cups with molecular weights in two distinct ranges, as well as for cups with molecular weights in the same range but with or without calcium stearate added. In Test 2, cups that were sterilized in air with gamma irradiation exhibited lower rates of wear than those sterilized with ethylene oxide, presumably due to the crosslinking induced by the irradiation. In addition, cups that were irradiated while packed in a partial vacuum to minimize oxygen absorbed in the surface layer initially showed lower rates of wear than those irradiated in air, with the wear rates becoming similar as wear penetrated the more oxidized surface layer and the more crosslinked subsurface region. Because these tests were run a few months after the irradiation, the potential effects of long-term oxidation of any residual free radicals in the irradiated materials could not be taken into account. After artificial aging to accelerate oxidative degradation of the materials, the wear rates could be markedly different. Analyses performed after wear indicated that the irradiated (i.e., crosslinked) cups exhibited a smaller proportion of, as well as shorter, fibrils in the wear debris and an increased crystallinity and melting temperature and that gamma irradiation in the low-oxygen environment reduced the level of oxidation and increased the level of crosslinking in the surface region of the cups.

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PubMed1999

[The value of CT in classification and decision making in acetabulum fractures. A systematic analysis].

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