title: Long-term results for Kinemax and Kinematic knee bearings on a six-station knee wear simulator.
abstract: A long-term wear test was performed on Kinemax and Kinematic (Howmedica Inc.) knee bearings on the Durham six-station knee wear simulator. The bearings were subjected to flexion/extension of 65-0 degrees, anterior-posterior translation of between 4.5 and 8.5 mm and a maximum axial load of 3 kN. Passive abduction/adduction and internal/external rotation were also permitted, however, two of the stations had a linkage system which produced +/- 5 degrees active internal/external rotation. The bearings were tested at 37 degrees C in a 30 per cent bovine serum solution and the test was run to 5.6 x 10(6) cycles. The bearings from stations 2 and 3, and stations 4 and 5 were swapped during the test to investigate the effects of interstation variability. The average wear rate and standard error was 3.00 +/- 0.98 mg/10(6) cycles (range 1.33-4.72 mg/10(6) cycles) for the Kinemax bearings and 3.78 +/- 1.04 mg/10(6) cycles (range 1.87-4.89 mg/10(6) cycles) for the Kinematic bearings. There were no significant differences in wear rates between the different bearing designs, the addition of active internal/external rotation or a change of stations. However, the wear tracks were different for the two types of bearings and with active internal/external rotation. The wear rates and factors were generally lower than previously published in vitro wear results; however, this may have been due to a difference in the axial loads and lubricants used. The appearance of the wear tracks with active internal/external rotation was comparable with those seen on explanted knee bearings.
authors: Centre for Biomedical Engineering, School of Engineering, University of Durham, UK.
authors: H E
authors: HE
authors: Ash
authors: I C
authors: IC
authors: Burgess
authors: A
authors: A
authors: Unsworth
mesh_terms: D015982:Bias; D019544:Equipment Failure Analysis / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D007720:Knee Prosthesis / Q000592:standards*; D008153:Lubrication; D008422:Materials Testing / Q000295:instrumentation* / Q000379:methods*; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D012399:Rotation; D016474:Weight-Bearing