Research On Isolation Method Of Mixed Debris And Wear Mechanism Of Artificial Joint Materials

With the increasing aging of population in China,the incidence of various kinds of osteoarthrosis is increasing.The demand for artificial joint replacement is increasing.Aseptic loosening caused by wear debris is one of the main reasons for artificial joint failure,which is related to the size,quantity and shape of wear particles.Therefore,it is particularly important to study the isolation and analysis of artificial joint wear debris.The methods of isolating wear debris of artificial joint were concerning wear debris of a single material.It is easy to be separated and isolated due to the large density difference between the debris and solvent.The methods of isolating in precious researches was not unified,and the recovery rate of wear debris was unclear.The wear debris produced by wear of artificial joint are mixture of two or more materials.In order to study the characteristics of different artificial joint wear debris,it is necessary to propose a reliable method of separating and isolating mixed artificial joint wear debris,which can realize the separation of artificial joint mixed wear debris.The method can obtain high recovery rate and high quality debris image,which provides the basis for the research on the mechanism of debris generation and wear mechanism of artificial joint.In this paper,alkali degradation,acid degradation and enzyme degradation were used to degrade calf serum protein.The degree of protein degradation was quantified by protein degradation rate in calf serum solution and the optimal protein degradation scheme was proposed.The method of separating and isolating mixed debris by multiple centrifugation and isolation was proposed,which can separate and isolate artificial joint mixed debris effectively and improve the recovery rate of artificial joint debris.The wear debris produced in artificial knee joint decomposing motion and knee joint simulating wear in vitro were separated and isolated.The feasibility of the optimized protein degradation scheme and the isolating method of artificial joint debris with different density ratio was verified.The formation mechanism of wear debris and wear mechanism of artificial knee joint materials and artificial knee joint were revealed.The main conclusions are as follows:(1)Protein degradation rate used as a quantitative index of protein degradation was proposed.The degradation rate and mechanism of calf serum solution protein degradation by alkali,acid and enzyme were explored.The results showed that the protein degradation rate reached to 95.89%with the the method of strong alkali,which was easy to operate and could obtain high-quality debris morphology.But the process needed a long time.The method of protein degradation with strong acid was simple and needed a short time.However,the highest degradation rate by stronge acid was only 71.87%.There was much exhausted liquid produced in the process,which can be used to isolated polymer debris.The protein degradation rate reached 94.98%with protease degradation method,No protein precipitation and less exhausted was produced in the process.But the solution was easy to be polluted by external impurities in the process due to the complicated operation procedure.This method is widely used in isolating wear debris of ceramic,cobalt chromium alloy,titanium alloy.(2)The method of the separation and isolation of artificial joint debris with different density ratio by multiple centrifugation was proposed.The results showed that the the debris on the wall of the centrifugal tube can be washed off with deionized water,and the debris entered the solution again for further centrifugation and isolation,which increased the recovery rate of wear debris.This method can effectively separate the mixed debris of artificial joint with different density ratio in suspension.Compared with the first recovery rate,the recovery rate of CoCrMo,UHMWPE,PEEK and ZrO₂ increased by 6.7%,15.1%-23.44%,9.95%and 10.91%,respectively.The method can effectively improve the recovery rate of artificial joint debris,especially UHMWPE debris.(3)The wear characteristics of PEEK-XLPE and CoCrMo-XLPE in swing wear test were studied.The results showed that the wear loss of XLPE in PEEK group is45.8%lower than that in CoCrMo group.The results showed that the wear of XLPE in PEEK group was mainly abrasive wear with plastic deformation and fatigue wear on the worn surface.The main wear mechanism of PEEK was abrasive wear.And fatigue wear caused the materials to peel off,which led to pits in some area.XLPE debris was mainly block.PEEK debris was small in quantity and size,and all debris surface was smooth.The wear debris was mainly block,with a small amount of round and oval wear debris.There were more svere plastic deformation and fatigue wear on XLPE worn surface in CoCrMo group than that in PEEK group.There were discontinuous furrows on the worn surface of CoCrMo and a few pits caused by corrosion.The amount of big block XLPE debris in CoCrMo group was more than that of PEEK group.The amount of XLPE debris in CoCrMo group was significantly more than that in PEEK group.Some strip debris with smooth surface was produced.The amount and size of CoCrMo debris are less than PEEK,and the surface of the debris presents multi-layered texture.(4)The wear characteristics of PEEK-XLPE and CoCrMo-XLPE in sliding wear test were studied.The results showed that the wear loss of XLPE in PEEK group was50%of that in CoCrMo group.There were furrows,fine grain due to platic deformation and massive spalling caused by fatigue on the worn surface in PEEK group.The worn surface of PEEK was mainly furrows and scratches besides some adhesion.The XLPE debris in PEEK group was block,strip and curly flake.The number of PEEK debris was small.And the surface of PEEK debris was smooth.In addition to block,bar debris,there are some flake debris with smooth surface.The worn surface of XLPE in CoCrMo group showed furrow of different width and a small amount of spalling.The worn surface of CoCrMo was mainly composed of furrows with different width and some area was corroded.The amount of large block debris of XLPE in CoCrMo group was more than that of PEEK group.The size and quantity of CoCrMo wear debris are small.They were mainly block.The surface of debris was smooth and their edges was neat.The debris with honeycomb structure and holes on the surface were produced by corrosion wear.(5)The wear characteristics of 5 million cycles of PEEK-XLPE and CoCrMo-XLPE artificial knee joint were studied.The results showed that the wear of tibial liner in PEEK group was lower than that in CoCrMo group,while the wear of femoral condyle in PEEK group was higher than that in CoCrMo group.The wear of tibial liner in PEEK group and CoCrMo group was mainly abrasive wear.With the increase of the number of cycles,the fatigue wear increased.The amount of large block XLPE debris in CoCrMo group was more than that in PEEK group,and a large number of small strip and needle debris were produced.The wear of PEEK femoral condyle is mainly abrasive and fatigue wear.The amount of PEEK debris is small,and the main size is 90nm-20?m.The debris with neat edges was mainly block.The wear debris of CoCrMo was less than that of PEEK.The size of wear debris is less than 10?m and mainly block.The surface of wear debris is mostly lamellar texture.The surface of wear debris produced by corrosion wear was honeycomb.