title: Simulation of fretting wear at orthopaedic implant interfaces.
abstract: Osteolysis due to wear debris is a primary cause of failure of total joint replacements. Although debris produced by the joint articulating surfaces has been studied and simulated extensively, fretting wear debris, produced at nonarticulating surfaces, has not received adequate attention. We developed a three-station fretting wear simulator to reproduce in vivo motion and stresses at the interfaces of total joint replacements. The simulator is based on the beam bending theory and is capable of producing cyclic displacement from 3 to 1000 microns, under varying magnitudes of contact stresses. The simulator offers three potential advantages over previous studies: The ability to control the displacement by load, the ability to produce very small displacements, and dynamic normal loads as opposed to static. A pilot study was designed to test the functionality of the simulator, and verify that calculated displacements and loads produced the predicted differences between two commonly used porous ingrowth titanium alloy surfaces fretting against cortical bone. After 1.5 million cycles, the simulator functioned as designed, producing greater wear of bone against the rougher plasma-sprayed surface compared to the fiber-mesh surface, as predicted. A novel pin-on-disk apparatus for simulating fretting wear at orthopaedic implant interfaces due to micromotion is introduced. The test parameters measured with the fretting wear simulator were as predicted by design calculations, and were sufficient to measure differences in the height and weight of cortical bone pins rubbing against two porous ingrowth surfaces, plasma-sprayed titanium and titanium fiber mesh.
authors.affiliation: Biomechanics Laboratory, J. Vernon Luck, Sr, M.D. Orthopaedic Research Center, Los Angeles Orthopaedic Hospital/UCLA, The Dorr Arthritis Institute of Centinela Hospital, Inglewood, California, USA. ebramzad@usc.edu
authors.forename: Edward
authors.initials: E
authors.lastname: Ebramzadeh
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Billi
authors.forename: Sophia N
authors.initials: SN
authors.lastname: Sangiorgio
authors.forename: Sarah
authors.initials: S
authors.lastname: Mattes
authors.forename: Werner
authors.initials: W
authors.lastname: Schmoelz
authors.forename: Lawrence
authors.initials: L
authors.lastname: Dorr
mesh_terms: D002102:Cadaver; D004867:Equipment Design; D019544:Equipment Failure Analysis / Q000295:instrumentation* / Q000379:methods; D005269:Femur / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D017276:Friction; D006801:Humans; D066298:In Vitro Techniques; D007595:Joint Prosthesis; D008422:Materials Testing / Q000295:instrumentation* / Q000379:methods; D009068:Movement; D010812:Physical Stimulation / Q000295:instrumentation* / Q000379:methods; D010865:Pilot Projects; D011475:Prosthesis Failure; D013314:Stress, Mechanical; D013499:Surface Properties; D013977:Tibia / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D016474:Weight-Bearing