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J Nevelos

Publications and source records attributed to J Nevelos.

4 recordsLinked to original sources
PubMed2006

'Severe' wear challenge to 'as-cast' and 'double heat-treated' large-diameter metal-on-metal hip bearings.

The wear generation of double-heat-treated and as-cast large-diameter metal-on-metal (MOM) hip bearings was investigated using standard- and 'severe'-gait simulations. The test hypothesis was that double heat treatment would change MOM hip wear compared with the as-cast condition. Two groups of high-carbon MOM bearings of 40 mm diameter were manufactured and subjected to either hot isostatic pressing (HIP) and solution annealing (SA) or no heat treatment (as cast). The results showed no statistical difference between the two groups under both running-in and steady state conditions. Even under the most 'severe'-gait simulation published to date, the mean volumetric wear rates were 2.9 and 3.9 mm3 per 10(6) cycles for the HIP-SA and as-cast bearings respectively, showing a ten-fold increase in wear compared with walking. These differences were not statistically different; therefore our hypothesis was negated. Changes in alloy microstructure do not appear to influence the wear behaviour of high-carbon cast MOM articulations with similar chemical compositions. This is in sharp contrast with the published significance of bearing diameter and radial clearance on the wear of MOM hip bearings.

Biocompatible Materials↗
PubMed2004

Surface engineering of prosthetic knee components.

Conventional total and uni-compartmental knee replacement designs usually incorporate metal femoral and tibial components with an ultra high molecular weight polyethylene (UHMWPE) bearing surface. The tibial components can be modular or monobloc and are of the fixed bearing type in the majority of cases. Mobile bearings are also in common use with a modular meniscal insert with either rotation only or a combination of rotation and translation. Wear of the UHMWPE components remains of primary concern in these prosthetic devices. Catastrophic wear and delamination has been largely addressed by improvements in UHMWPE quality and manufacturing methods, however, abrasive and adhesive wear of the UHMWPE components remains a concern for long-term survivorship of total knee replacement. This review very briefly covers published long-term survivorship of primary knee arthroplasties, primary wear mechanisms present in knee replacements and the potential for wear reduction by surface engineering of the metal wear counterfaces. There are several methods and materials available, which offer the potential for significantly reduced wear.

Biomedical Engineering↗
PubMed2000

Wear of alumina-on-alumina total hip arthroplasties at a mean 11-year followup.

The surface topography of 11 alumina-on-alumina hip arthroplasties retrieved for aseptic loosening at a mean 11-year followup was investigated. Macroscopic wear was assessed using a coordinate measuring machine. Microscopic wear features were evaluated by Talysurf analysis. Scanning electron microscopy was used to look at the alumina microstructure. Components were classified into three groups: (1) low wear with no sign of wear and average arithmetic roughness values below 0.05 microm; (2) stripe wear with a visible oblong worn area on the femoral heads and penetration rates below 10 microm/year; and (3) severe wear with a visible loss of material on both components, showing total roughness values as much as 4 microm and maximum penetrations higher than 150 microm. Alumina quality assessed by grain size measurements and porosity percentages improved progressively from 1977 to 1988. This resulted in a correlated decrease of the microscopic wear magnitude. However, on a macroscopic scale, factors responsible for either a load increase (weight, young age, and male gender) or impairment in the load distribution over the component surfaces (large grain size, nonoptimal initial cup inclination, and cup migration and/or tilting) increased the penetration rates.

Adolescent↗