The Otto Aufranc Award - Wear and lubrication of metal-on-metal hip implants

The implication of polyethylene wear particles as the dominant cause of per iprosthetic osteolysis has created a resurgence of interest in metal-on-met al implants for total hip arthroplasty because of their potential for impro ved wear performance. Twenty-two cobalt chromium molybdenum metal-on-metal implants were custom-manufactured and tested in a hip simulator. Accelerate d wear occurred within the first million cycles followed by a marked decrea se in wear rate to low steady-state values. The volumetric wear at 3 millio n cycles was very small, ranging from 0.15 to 2.56 mm(3) for all implants t ested. Larger head-cup clearance and increased surface roughness were assoc iated with increased near. Independent effects on wear of material processi ng (wrought, cast) and carbon content were not identified. Implant wear dec reased with increasing lambda ratio, a parameter used to relate lubricant f ilm thickness to surface roughness, suggesting some degree of fluid film lu brication during testing. This study provided important insight into the de sign and engineering parameters that affect the wear behavior of metal-on-m etal hip implants and indicated that high quality manufacturing can reprodu cibly lead to very low wear.