Abrasive Wear

Oxidized Zirconium

Adhesive Wear

Another aspect of wear in TJA is adhesion. Friction increases when the metal/poly interface is "dry" or not well-coated with lubricant. This action is similar to motor oil keeping pistons from "sticking" in a car engine. This is referred to as lubricity - in TJA, it is the ability of the synovial fluid to coat the metal/poly interface. The following test looks at how much friction is generated between two surfaces. Surfaces that attract more lubricating fluid and remain smooth tend to result in less friction. Ultimately, this means a lower potential for adhesive wear. The material exhibits less friction against polyethylene and cartilage as compared to cobalt chrome. This indicates that less adhesive wear of polyethylene and cartilage would be expected for OXINIUM material than for cobalt chrome.

Friction Study

Friction against UHMWPE



To measure friction or lubricity against polyethylene, OXINIUM and cobalt chrome cylinders were made. Each cylinder reciprocated under a load against a flat polyethylene disk in deionized water.

The OXINIUM material exhibited a significantly lower co-efficient of friction against polyethylene than cobalt chrome.

Friction Against Cartilage



To measure friction or lubricity against cartilage, flat disks of OXINIUM material and cobalt chrome were used. A calf cartilage pin was then rotated against each disk in solution of bovine serum. Again, the OXINIUM material exhibited a significantly lower coefficient of friction against cartilage than cobalt chrome.