Investigation of the lubrication properties and synergistic interaction of biocompatible liposome-polymer complexes applicable to artificial joints.

Achievement of efficient biolubrication is essential for the design of artificial joints with long lifetimes. This study examines the frictional behaviors and adsorption structures of liposomes and liposome complexes with biocompatible polymers to reveal the underlying lubrication mechanisms between biomimetic bearing surfaces of polyetheretherketone (PEEK) and silicon nitride (Si3N4). The liposomes with increasing carbon chain lengths exhibit the remarkable lubrication capabilities that correlate strongly with the structural integrity of small unilamellar vesicles adsorbed on the Si3N4 surfaces, while the bilayer structures weaken the stability of vesicles against rupture and cause the increase of friction. The synergistic interaction of liposomes and biocompatible negative-charged polymer leads to the formation of a boundary-lubricating layer with high-density liposome-polymer complex structures that can efficiently improve the lubrication properties of liposomes. Our findings might have implications for future biolubrication investigations on biocompatible liposome-polymer complexes applicable to artificial joints at the specified macroscale conditions.

Computational simulation analysis for torus radius of edge contact in hip prostheses.

Stripe wear occurs when the components of hip prostheses move a sufficient distance laterally to contact the edge of the acetabular cup, causing abnormally high contact stresses. In this research, edge loading contact of prosthetic hip is analyzed in the most commonly used material pairs. The contact dimensions and maximal contact pressure are investigated in mutative normal edge loading with 3 different inclination angles (15°, 20°, 25°) and in alterable edge torus radius with edge loading of 2500 N and inclination of 20°. A computational case was conducted for a 14 mm radius alumina ceramic bearing with a radial clearance of 0.1 mm using a normal edge loading ranged from 0 N to 3000 N. Additionally, the Hertzian theory successfully captures principal curvature trends of the edge torus on the influence of maximal contact pressure and obtains the appropriate edge radius range for lower maximal contact pressure. This work elucidates the methods of applying classical contact theory to design the edge radius of hip bearings to better resist severe edge loading contact stresses and reduce the stripe wear.

Contact mechanics and wear simulations of hip resurfacing devices using computational methods.

The development of computational and numerical methods provides the option to study the contact mechanics and wear of hip resurfacing devices. The importance of these techniques is justified by the extensive amount of testing and experimental work required to verify and improve current orthopaedic implant devices. As the demands for device longevity is increasing, it is as important as ever to study techniques for providing much needed orthopaedic hip implant solutions. Through the use of advanced computer aided design and the finite element method, contact analysis of hip resurfacing devices was carried out by developing both three-dimensional and two-dimensional axisymmetric models whilst considering the effects of loading conditions and material properties on the contact stresses. Following on from this, the three-dimensional model was used in combination with a unique programme to develop wear simulations and obtain cumulative wear for both the acetabular cup and femoral head simultaneously.