With greater numbers of primary knee replacements now performed in younger patients there is a demand for improved performance. Surface roughness of the femoral component has been proposed as a causative mechanism for premature prosthesis failure. Nineteen retrieved total knee replacements were analysed using a non-contacting profilometer to measure the femoral component surface roughness. The Hood technique was used to analyse the wear and surface damage of the matching ultra-high molecular weight polyethylene (UHMWPE) tibial components. All femoral components were shown to be up to 11× rougher after their time in vivo while 95 % showed a change in skewness, further indicating wear. This increase in roughness occurred relatively soon after implantation (within 1 year) and remained unchanged thereafter. Mostly, this roughness was more apparent on the lateral condyle than the medial. This increased femoral surface roughness likely led to damage of the UHMWPE tibial component and increased Hood scores.

This paper gives a theoretical analysis of the distribution of potential and current density on the surface of a coplanar galvanic cell in which the polarization parameters for cathode and anode are unequal. The potential at any point can be represented as a Fourier series, in which the coefficients themselves are infinite series. It is shown that these Fourier coefficients can only be approximated by numerical methods. The potential distribution across the electrode at the electrode/electrolyte interface is shown to be dependent on both the anodic and cathodic polarization parameters and cannot be deduced from the potential distribution occurring when the anodic and cathodic polarization parameters are equal. As the cathodic polarization parameter is increased relative to that of the anode the potential shifts toward the open‐circuit anodic voltage and both the potential and current distribution become more uniform. A parameter is suggested which characterizes the “microscopic” or “macroscopic” behavior of the cell. When the ratio between polarization parameters is large the behavior of the cell tends toward either anodic or cathodic control rather than the “mixed” control.

Shoulder joint replacement generally utilizes ultra-high molecular weight polyethylene (UHMWPE) as a bearing surface. Long term survival of such implants is recognized to be limited by wear of the UHMWPE. Commercially available JRI 42mm diameter VAIOS Total shoulders were wear tested in diluted bovine serum for five million cycles in a unique Shoulder Wear Simulator. Five Total shoulders were subject to rotational and translational motion, and loading, to replicate the 'Mug to Mouth' activity of daily living. A sixth Total shoulder was subject to loading only in a control station. Wear was measured gravimetrically and surface roughness was measured with a non-contacting profilometer. Mean wear rate of the UHMWPE components was 21.5 ± 5.4 mm 3 /million cycles. The humeral heads roughened, from 19 ± 3 nm Sa to 43 ± 13 nm Sa over the five million cycles of the test, whilst the UHMWPE glenoid components became smoother, from 959 ± 230 nm Sa to 77 ± 17 nm Sa. This is the first reported wear test of multiple samples of a commercially available Total shoulder in a dedicated shoulder simulator.

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AbstractsThe densities of states and Fermi energies were accurately calculated from E ( k ) data obtained by the self-consistent-band Augmented Plane Wave (APW) method, using a quadratic energy expansion. The reliability of the Monte Carlo integration was investigated. It was sufficiently good to determine the anisotropy of the Fermi surface of lithium, sodium, and potassium.