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Highly cross-linked ultra-high molecular weight polyethylene (UHMWPE) decreases wear at the hip by more than 50% compared with conventional UHMWPE. However, melted highly cross-linked polyethylene may be susceptible to fatigue cracking, and annealed highly cross-linked polyethylene may be susceptible to in vivo oxidation. The second-generation highly cross-linked UHMWPE (X3 HXPE) uses a sequential irradiation and annealing process. It preserves mechanical strength properties and has the highest survivorship in functional fatigue testing. The free radical content is low, and its performance under accelerated aging is the same as virgin UHMWPE. Hip simulator studies with 32-mm acetabular components demonstrated 97% wear reduction compared with conventional UHMWPE, and 62% compared with a clinically successful first-generation annealed highly cross-linked polyethylene. The crystallinity, density, and tensile strength of the X3 HXPE material was unchanged by oxidative challenge. X3 HXPE material articulating on cobalt-chromium alloy yields a volumetric wear rate very similar to that of metal-on-metal articulations, but eliminates the concerns of metal ion release. Wear particles generated from the X3 HXPE were the same size as those produced from conventional UHMWPE. Preliminary results suggest X3 HXPE can be used for cups larger than 36 mm.

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Background Ceramic bearings were introduced to reduce wear and increase long-term survivorship of total hip arthroplasty. In a previous study comparing ceramic with metal-on-polyethylene at 5 to 8 years, we found higher survivorship and no osteolysis for the ceramic bearings. Questions/Purposes We asked whether ceramic bearings have equal or superior survivorship compared with that for metal-on-polyethylene at longer followup; we also determined survivorship of the implant systems, the presence or absence of radiographic osteolysis, and incidence of device squeaking.Methods Five surgeons at five sites have followed 189 patients (216 hips) for a minimum of 10 years and average of 10.3 years (range, 10-12.4 years) comparing alumina ceramic bearings (144 hips) with cobalt chromeon-polyethylene bearings (72 hips). We determined KaplanMeier survivorship of the bearing surface and implant systems and collected radiographic and clinical data. Results We observed no difference between the control metal-on-polyethylene and the alumina-bearing couple cohorts with regard to bearing-related failures (98.9% versus 99.1%). Revisions for any reason occurred in 10

Therapeutic study, Level III (retrospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.