The Friction And Wear Behaviors Of CoCrMo,PEEK,and HXLPE Against Cartilage Under The Different Motions

Articular cartilage is the load-bearing of synovial joints,which mainly plays the role of transfer load,increasing the joint contact area,reducing contact pressure and buffer shock.However,arthritis,mechanical trauma,and congenital or acquired joint diseases all result in the loss of articular cartilage tissue.The inherent avascularity and nervelessness of articular cartilage results in difficulty of self-repair.Most studies on the friction and wear behavior of articular cartilage focused on reciprocal linear motion,cross-shear motion has been proven to exist with the physiological motion of the hip and knee joint,but few studies on the friction and wears behavior of articular cartilage under cross-shear motion are known.Therefore,in this paper,we characterize the mechanical properties of bovine knee cartilage and combine three commonly used biomedical materials: cobalt-chromium-molybdenum(CoCrMo),polyetheretherketone(PEEK),and high cross-linked polyethylene(HXLPE)against articular cartilage.To investigate the effects of load,roughness,and mode of motion on the frictional and wear behaviors of articular cartilage.Aims to explore the frictional and wear behaviors and mechanisms of articular cartilage,providing a more theoretical basis and clinical guidance for cartilage repair treatment and the development of high-performance bionic cartilage materials.(1)The compression deformation of the articular cartilage increased when the load increased from 0.5 MPa to 5 MPa,and the indentation depth of the articular cartilage was about 1.1 mm under a static load of 4 MPa,and the indentation depth reached the maximum,and the load-bearing of the cartilage tissue changed to a complete solid-phase.The modulus elasticity of articular cartilage tended to decrease when the diameter of the indenter was increased from 1 mm to 3 mm,while the modulus elasticity of articular cartilage increased when the loading rate was increased from 1 μm/s to 20 μm/s.Articular cartilage under cyclic loading produces a ratchet strain effect,and an increase in the amplitude of cyclic loading increased the rate of compressive deformation and indentation depth of articular cartilage at the same cyclic loading frequency.The results of permanent deformation and recovery time of articular cartilage after compression deformation showed that the recovery time of articular cartilage under 1 MPa load of 3 h(or less)produced no permanent deformation,and the recovery time under 2 MPa and 3 MPa static load of 3 h and 6 h(or less)produced permanent deformation with permanent deformation of 0.25% and 0.38%,respectively.There was no significant effect of different materials on the permanent deformation of articular cartilage.(2)The coefficient of friction of the PEEK pairs was maintained at a minimum under the condition of clinical surface roughness,and the coefficient of friction of all three sets of friction pairs decreased with increasing load.Under the smooth condition of materials,the coefficient of friction of pairs were affected by the hydrophilic property of materials,the better the hydrophilic property of materials,the lower the coefficient of friction,and the coefficient of friction appeared to rise slowly.Under the rough condition of materials,the surface roughness of the material was the mainly influencing factor,and the coefficient of friction was quickly stabilized in a short period of time.PEEK has better frictional properties and more suitable for clinical applications in cartilage repair and hemiarthroplasty treatment.(3)The articular cartilage wear increased with increasing loads and surface roughness of the materials.Under the clinical requirement,the cartilage wear of the CoCrMo pair was the lowest,followed by the PEEK pair and the HXLPE pair was the highest in both cross-shear motion and reciprocal linear motion.The cartilage wear of all three pairs increased significantly with increasing load.Under the same roughness level conditions,the flexible material has less friction on the articular cartilage and the rigid material has more cartilage wear,which shows the least cartilage damage for HXLPE pair,followed by PEEK pair and the largest for CoCrMo pair.(4)There is no significant effect of both reciprocal linear motion and cross-shear motion on the coefficient of friction,while the amount of cartilage wear and the increment of surface roughness after wear are slightly lower under cross-shear motion than that of reciprocal linear motion.Under the low roughness conditions,the cartilage wear was concentrated in the superficial to middle layer of cartilage,the cartilage damage in reciprocal linear motion was mostly plough,and the cartilage damage under cross shear motion was mainly creeping accumulation of cartilage tissue.Under the high roughness conditions,the cartilage wear was concentrated in the middle to deep layer of cartilage,and the cartilage surface would be polished after wear,among which the polishing phenomenon was especially significant in CoCrMo pair.The cartilage damage in the reciprocal linear motion was more constantly extruded to both sides which formed a ridge injury damage and was mostly perpendicular to the direction of motion and parallel arrangement,the cartilage damage under cross-shear motion was mainly the ridge which from the center to the cartilage edge,and the ridge area was comparatively small.