2009 Knee Society Presidential Guest Lecture: Polyethylene Wear in Total Knees

Abstract

Knee arthroplasties in young and active patients place a substantial increase in the lifetime tribological demand and potential for wear-induced osteolysis. Polyethylene materials have advanced in recent years, reducing the potential for oxidative degradation and delamination failure. It is timely to consider tribological design variables and their potential to reduce surface wear and the long-term risk of osteolysis. The influence of reduced cross shear in rotating platform mobile-bearing knee designs and reduced surface wear area in low conforming fixed-bearing knees has been investigated. A reduction in cross shear substantially reduced wear in both multidirectional pin-on-plate studies and in rotating platform mobile-bearing designs in knee simulator studies. A reduction in bearing surface contact area substantially reduced surface wear in multidirectional pin-on-plate simulations and in low conforming fixed-bearing knee designs in knee simulator studies. This offers potential for a paradigm shift in knee design predicated by enhanced mechanical properties of new polymer materials. We describe two distinct low-wearing tribological design solutions: (1) a rotating platform design solution with reduced cross shear provides reduced wear with conformity and intrinsic stability; and (2) a low conformity fixed bearing with reduced surface area, provides reduced wear, but has less intrinsic stability and requires good soft tissue function.

Computational modelling of polyethylene wear and creep in total hip joint replacements: Effect of the bearing clearance and diameter

“…In more recent studies, the increase of the PE wear for larger heads has been mainly attributed to the increase in contact area, in which wear has been found to be directly proportional to contact area. 2,9 Another parameter, the bearing clearance, which is defined as the difference in diameter or radius between the acetabular cup and femoral head bearing surfaces, may also have an influence on bearing wear, since the clearance can significantly affect contact area and hence wear. This has also been demonstrated in a laboratory simulator study.…”

Wear of knee prostheses

“…16,17,22 Wear is reduced by reduced cross-shear, increased cross-linking, and a reduced surface area. This new scientific relationship has been used to create three different and distinctive low-wear solutions in the knee, ie, the rotating platform mobile-bearing knee, the fixed-bearing moderately cross-linked polyethylene knee, and the low-conforming partial knee.…”

“…In considering improved design solutions for polyethylene in the knee, we have modified Archards law 15 and introduced a new wear equation for polyethylene: 16,17 wear volume = C × (sliding distance) × (contact area) f(cross-shear) × f(counter face roughness) × f(level of cross-linking) In particular, we have shown the wear rate is dependent on and reduces with reduced contact area, reduced crossshear, reduced surface roughness, and increased crosslinking. The primary relationship shows that the surface wear volume increases as the area of polyethylene being worn increases.…”

“…The primary relationship shows that the surface wear volume increases as the area of polyethylene being worn increases. [16][17][18][19][20] The wear rate of polyethylene increases with an increase in cross-shear. 21,22 At low cross-shear, associated with unidirectional motion, the wear rate is low; however, as cross-shear ratio increases to between 0.05 and 0.1 the wear rate reaches its maximum value.…”

Does Texturing of UHMWPE Increase Strength and Toughness?: A Pilot Study

“…This work was performed at Public Research Centre Henri Tudor, Esch-sur-Alzette, Luxembourg, and Institut Jean Lamour, Nancy, France. [5,10]. The debris produced in the periprosthetic tissue stimulates osteolysis [9] that causes loosening of the implant and eventually leads to its failure [4,9,19].…”