A Novel Engineering Spherical Bearing, with Potential Application for a Hip Implant

It is a research which could enter into contradiction with the current trend concerning the hip implants. It is known as sliding friction, which is characteristic of present artificial hip joints, is higher than in the case of rolling friction. The paper reports the studies of the functioning mode of a novel spherical bearing MoM (metal on metal) with rolling friction, with potential application for an artificial hip joint obtained by introducing a number of balls between the femoral head and the acetabular cup. After over 15 years of research upon the functional principle and constructive solution, a version that offered a coefficient of minimum friction in the hip joint came to light. This version was based on a constructive solution of motion with lower friction, “Omnitrack movement solutions”, which has been modified and rebuilt to be used as a joint of a total hip prosthesis—MOMJ. The joint was built entirely in stainless steel, SS316L medical grade. Tests have been carried out on the experimental laboratory devices that showed very low values of the coefficient of friction (μ = 0.0225). For validation, the prosthesis had to be put through tests for 500,000 cycles, in terms of physiological motion and dynamic loading, according to ISO 14242-3. Testing was conducted on a multiaxial dynamics machine, MTS Bionix, equipped with system for hip implant testing. The testing results of this total hip prosthesis with rolling friction have been successful in signing up for a friction moment of 0.525 kNmm which means a coefficient of friction μ = 0.0143, for a joint with femoral head diameter 28 mm.