Wear testing of materials and surfaces for total knee replacement

Abstract

A simple wear test was investigated for evaluating the wear and damage of material pairs when used in total knee replacement. The test consisted of an axially loaded metallic femoral indentor and a reciprocating ultrahigh molecular weight polyethylene (UHMWPE) flat disk that represented the tibial component. A number of variables were studied including the effect of conformity by varying the radii of the femoral surface, distilled water or serum as a lubricant, different femoral materials, and different types of UHMWPE. In general, the different morphologies of the surface wear of the UHMWPE were similar to those seen on retrieved total knee replacements. Increased conformity with a cylindrical indentor gave a reduced wear rate initially, compared with that of the lower conformity spherical indentor. However, the wear rates were similar subsequent to this initial wearing in phase. Transfer films of UHMWPE were observed on the cobalt-chrome indentors for both serum and distilled water lubrication, although this film was more extensive for distilled water. The lowest wear rate was observed when oxidized zirconium was used on the femoral side, which was attributed to greater wettability, surface hardness, and immunity to oxidative wear. Tests using cobalt-chrome femoral cylinders and different grades of UHMWPE showed different wear rates. Of these PEs, GUR 415 showed less wear than both RCH 1000 and UHMWPE containing numerous fusion defects. For the latter, wear was attributed to a fatigue mechanism, although in most cases it was associated with surface phenomena rather than subsurface cracking. However, in some specimens of UHMWPE subsurface crack propagations occurred with defects. The test method is discussed in relation to its applicability to the evaluation and comparison of bearing materials and surfaces, with particular application to total knee replacements.

Molecular Deformation Mechanisms in UHMWPE During Tribological Loading in Artificial Joints

“…This is typical of polymers like polyethylene with a smooth molecular profile and the lack of side groups and kinks in the chain [4,5]. The formation of the transfer layer depends on the environment and is more severe when tested in water, compared with serum, but it has even been found on retrieved implants [6]. In the depth the mechanisms fatigue mechanisms occur.…”

Wear and toughness of crosslinked polyethylene for total knee replacements: A study using a simulator and small‐punch testing

“…[18][19][20] Cyclic anterioposterior translation of the contact point between the femoral and tibial components may result in structural failure (severe surface and subsurface cracking), leading to delamination. 21,22 It has been shown using the standard uniaxial tension test that mechanical properties of UHMWPE such as ductility and toughness decrease with increased radiation doses. 23,24 Therefore, concerns exist about the application of crosslinked UHMWPE to the tibial insert because crosslinking may result in significant deterioration in mechanical properties, such as ductility, toughness, and fatigue resistance, causing delamination wear or breakage of the tibial insert.…”

Patients’ perspective on controversial issues in total knee arthroplasty

“…While total hip arthroplasty has a long history of ceramic prosthesis, TKA has not been considered good for the application of ceramic components due to the concern over their mechanical properties [12,13,19,26]. Recently a great deal of attention has been paid to the ceramic femoral component which is claimed to be advantageous over traditional cobalt-chrome component in longevity [12,13,19,27]. Our findings indicate that the claimed advantage of better longevity would be very appealing to patients as well.…”