title: An experimental model of tibial counterface polyethylene wear in mobile bearing knees: the influence of design and kinematics.
abstract: Current designs of mobile bearing knees have different kinematics at the tibial counterface articulation; unidirectional represented by linear tracks and rotating platform designs, and multidirectional represented by reduced constraint designs with motion of the tibial surface in A-P and M-L directions simultaneously. One fifth scale experimental models of the tibial counterface articulation have been developed with mean contact stresses of 0.6 MPa. The unidirectional model had a linear reciprocating motion with a 10 mm stroke, the multidirectional model had a reciprocating motion with a 10 mm stroke and simultaneous rotation of +/- 7.5 degrees. Six specimens of GUR415 polyethylene were tested for each model, sliding on polished cobalt chrome counterfaces with Ra < 0.01 micron in 25% bovine serum lubricant. The mean +/- STERR wear rates were: unidirectional 0.045 +/- 0.015 mm3/million cycles and multidirectional 0.44 +/- 0.15 mm3/million cycles. Applying the scaling factor of 5, the predicted wear rates in actual knee prostheses were: unidirectional 0.23 mm3/million cycles and multidirectional 2.2 mm3/million cycles. The order of magnitude increase in wear rate was statistically significant (p = 0.05).
authors.affiliation: Medical and Biological Engineering Group, School of Mechanical Engineering, University of Leeds, UK.
authors.forename: V C
authors.initials: VC
authors.lastname: Jones
authors.forename: D C
authors.initials: DC
authors.lastname: Barton
authors.forename: D P
authors.initials: DP
authors.lastname: Fitzpatrick
authors.forename: D D
authors.initials: DD
authors.lastname: Auger
authors.forename: M H
authors.initials: MH
authors.lastname: Stone
authors.forename: J
authors.initials: J
authors.lastname: Fisher
mesh_terms: D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D002858:Chromium Alloys; D003198:Computer Simulation; D019544:Equipment Failure Analysis; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D016014:Linear Models; D008422:Materials Testing; D008954:Models, Biological; D011095:Polyethylenes; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D013314:Stress, Mechanical; D013499:Surface Properties; D013977:Tibia / Q000503:physiopathology; D016474:Weight-Bearing
chemical_list: D002858:Chromium Alloys; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene