Morphological characteristics of prosthetic wear particles generated in Al2O3-ultrahigh molecular weight polyethylene during running-in period
- VernacularTitle:超高分子量聚乙烯/Al2O3人工关节副磨合期磨损颗粒的形态特征
- Author:
Chuanhui HUANG
;
Genxi YANG
- Publication Type:Journal Article
- From:
Chinese Journal of Tissue Engineering Research
2008;12(4):765-769
- CountryChina
- Language:Chinese
-
Abstract:
BACKGROUND: Wear particles factually serve as a medium carrying extensive information on the wear process involved in hip implants. Moreover, it has been demonstrated that wear particles contribute to the failure of Charnley total hip replacement.OBJECTIVE: To investigate the morphological characteristics of wear particles generated by couples of ultrahigh molecular weight polyethylene (UHMWPE) cups and Al2O3 femoral heads, mounted in a simulator in the presence of distilled water and explore the wear mechanism of UHMWPE cup.DESIGN: Wear tests were performed on a ball-in-socket hip simulator.SETTING: Department of Mechanical Engineering, Xuzhou Institute of Technology.MATERIALS: The molecular weight of UHMWPE selected as cup was 3 000 000. Its density was 0.935 g/cm3, hardness 30 HB, fracture strength 35 MPa, and water absorption < 0.01%. The experimental femoral head was made of alumina and zirconia (Al2O3: 87%, ZrO2: 13%). Its density was 4 g/cm3, hardness 90 HRA, tensile strength > 450 MPa, and tenacity 7 MPaM1/2.METHODS: The experiment was performed in the laboratory of tribology, China University of Mining and Technology from December 2003 to July 2005. Hip simulator was used to assess the tribological performance of Al2O3-UHMWPE at room temperature, 100 r/min, 784 N load for 1.5×106 cycles. Distilled water was used as the lubricant. Wear of UHMWPE acetabulum was measured every 3×105 cycles by taking out the acetabulum from simulator, cleaning in distilled water for 3 minutes in an ultrasonic bath, putting in an oven for 40 minutes at 80 ℃, and cooling off in a desiccator. A BT211D electronic balance (reciprocal sensibility, 0.01 mg) was used to measure the weight loss of UHMWPE acetabula according to the reference sample method to calculate the wear. A sample (20 mL) of distilled water lubricant used in test was obtained when the simulator was stopped for gravimetric analysis. Morphology of wear particles in samples and surface of worn UHMWPE acetabula were observed by using scanning electron microscope (SEM). The components of wear particles were determined by X-ray. Detailed measurements of the wear particles distribution were conducted by LS100(R) Laser Particle Size Analyzer (including LS SVM Plus).MAIN OUTCOME MEASURES: Morphology and size distribution of wear particles; Wear mechanism and wear rate of UHMWPE acetabula.RESULTS: The wear particles showed a wide range of particle sizes, varying from 0.3 to 180 μm, most of which ranged from 5 to 20 μm. More than 99% of wear particles were UHMWPE particles, which were classified into five groups in terms of their morphological characteristics: spherical particle, tearing particle, lamellar particle, fatigued flaking and rod-shaped particle. Lamellar or cube was the predominant form of Al2O3 ceramic particles with flat surface structure and upright edges. The worn surfaces of UHMWPE cup showed evidence of multidirectional scratching, adhesive and micro-contact fatigue wear, and plastic deformation.CONCLUSION: ①The dominant wear mechanisms acting in the UHMWPE cup are abrasive wear, adhesive wear, microcosmic fatigue wear and flaking associated with plastic deformation. ②The size of particles accumulating mostly is tiny among the particle groups.
