Effects of clinically relevant alumina ceramic wear particles on TNF-alpha production by human peripheral blood mononuclear phagocytes

The recent introduction of microseparation of the components of ceramic-on-ceramic hip prostheses during hip simulations has produced clinically relevant wear rates, wear patterns and wear particles. This provided an opportunity to determine the response of primary human peripheral blood mononuclear cells to clinically relevant alumina ceramic wear particles in vitro. Alumina ceramic wear particles were generated in a hip joint simulator under microseparation conditions. The particles showed a bi-modal size distribution with nanometer sized (5-20nm) and larger particles (0.2->10 micrometer). The particles were cultured with human peripheral blood mononuclear cells obtained from six different donors at particle volume to cell number ratios of 1, 10, 100 and 500 micrometer(3). After 24h incubation the viability of the cells and the levels of TNF-alpha were determined. The response to the microseparation wear particles was compared to that of commercially available alumina powder with a uniform morphology and mean size of 0.5 micrometer. All six Donors PBMNC produced significantly elevated levels of TNF-alpha when stimulated with 100 micrometer(3) of the alumina powder per cell. Volumetric concentrations of 10 and 1.0 micrometer(3) per cell failed to stimulate a significant response by the cells from any of the six donors. Three of the six Donors PBMNC secreted significantly elevated levels of TNF-alpha when stimulated with 100 micrometer(3) of the microseparation wear particles, whereas the other three failed to respond to the wear debris at this concentration. All of the Donors PBMNC produced significantly elevated levels of TNF-alpha when stimulated with 500 micrometer(3) of the microseparation wear particles per cell. Thus, a greater volume of the microseparation wear particles was required to activate the PBMNC than the alumina powder. This was probably due to the microseparation wear particles having fewer particles in the critical size range (0.1-1 micrometer) for macrophage activation compared to the alumina powder. It can be concluded that alumina ceramic wear particles generated under microseparation conditions are capable of inducing osteolytic cytokine production by human mononuclear phagocytes. However, the volumetric concentration of the particles needed to generate this response is extremely high and given the low wear rates (<4mm(3) per million cycles) of ceramic-on-ceramic bearings, even under severe microseparation conditions, it is unlikely that this concentration threshold will be achieved in vivo.     

Wear of HIPed and non-HIPed alumina-alumina hip joints under standard and severe simulator testing conditions.

Wear and the biological response to wear debris of artificial joints remain major concerns in total hip arthroplasty (THA). The long-term effects of UHMWPE wear debris are well documented and these have led to interest in alternate bearing materials for THA. Alumina ceramic-ceramic hip joints have been successfully used for more than 30 years with low wear and little incidence of osteolysis. The most common wear pattern observed on retrieved components is an elliptical wear 'stripe' on the heads and a corresponding worn area on the cup with an approximated wear rate of 1-5 mm3 pa. More severe wear has also occasionally occurred, usually in association with an abnormal clinical history. Modern alumina-alumina THAs use an improved HIPed (hot isostatically pressed) alumina ceramic-bearing material which may be more resistant to severe wear. Previous in vitro simulator studies have not replicated in vivo wear rates or mechanisms. The aim of this study was to compare previous generation non-HIPed alumina and modern HIPed alumina in a hip joint simulator under 'normal' and 'harsh' testing conditions. HIPed alumina was found to have a lower wear rate than non-HIPed alumina, although the difference was not statistically significant at the 95% confidence level. Testing in Gelofusine and water lubricants did not elevate the wear rates of either material. Elevated swing phase load testing also had no significant effect on the wear rates of either material. Testing in the absence of any lubricant produced very severe wear of the non-HIPed material in one specimen only.     

陶瓷对陶瓷人工髋关节的磨擦界面特征

背景：陶瓷对陶瓷人工髋关节假体在临床上已有一定的应用,在表面磨擦、磨损和润滑方面占有优势,具有很大的研发潜力。 目的：评价陶瓷对陶瓷人工髋关节表面磨擦、磨损和润滑特性。 方法：将金属对超高分子量聚乙烯、金属对金属以及陶瓷对陶瓷人工髋关节假体的磨损界面研究进行分析,了解氧化铝陶瓷材料的结构特点、制备工艺以及磨损参数,并分析陶瓷对陶瓷人工髋关节置换治疗的效果,与其它假体材料进行对比。 结果与结论：①金属对超高分子量聚乙烯人工髋关节抗磨损性能差,使磨损颗粒进入关节和周围组织,造成骨溶解和松动。②金属对金属人工髋关节的磨损性能较金属对超高分子量聚乙烯假体有很大改善,骨溶解的发生率非常少,但由于磨损颗粒可散布于体内各脏器和体液中,使用时要注意避免发生过敏反应和毒性。③体外试验和体内试验证明陶瓷对陶瓷人工髋关节具有良好的摩擦、磨损、润滑性能,临床治疗长期随访结果显示陶瓷对陶瓷人工髋关节假体置换后无磨损颗粒,不会发生骨溶解。对于年龄较小,并且对髋关节活动度有较高要求的患者,陶瓷对陶瓷人工髋关节是治疗的首选。随着陶瓷对陶瓷人工髋关节假体设计和材料学的发展,通过改进假体的机械学特性,提高摩擦界面的耐磨性能和润滑机制,陶瓷对陶瓷人工髋关节假体的远期临床疗效将更加满意。     

Comparison of the cytotoxicity of clinically relevant cobalt-chromium and alumina ceramic wear particles in vitro

Concern over polyethylene wear particle induced aseptic loosening of metal-on-polyethylene hip prostheses has led to renewed interest in alternative materials such as metal-on-metal and alumina ceramic-on-alumina ceramic for total hip replacement. This study compared the effects of clinically relevant cobalt-chromium and alumina ceramic wear particles on the viability of U937 histiocytes and L929 fibroblasts in vitro.Clinically relevant cobalt-chromium wear particles were generated using a flat pin-on-plate tribometer. The mean size of the clinically relevant metal particles was 29.5+/-6.3 nm (range 5-200 nm). Clinically relevant alumina ceramic particles were generated in the Leeds MkII anatomical hip simulator from a Mittelmieier prosthesis using micro-separation motion. This produced particles with a bimodal size distribution. The majority (98%) of the clinically relevant alumina ceramic wear debris was 5-20 nm in size. The cytotoxicity of the clinically relevant wear particles was compared to commercially available cobalt-chromium (9.87 microm+/-5.67) and alumina ceramic (0.503+/-0.19 microm) particles. The effects of the particles on the cells over a 5 day period at different particle volume (microm(3)) to cell number ratios were tested and viability determined using ATP-Lite(TM).Clinically relevant cobalt-chromium particles 50 and 5 microm(3) per cell reduced the viability of U937 cells by 97% and 42% and reduced the viability of L929 cells by 95% and 73%, respectively. At 50 microm(3) per cell, the clinically relevant ceramic particles reduced U937 cell viability by 18%. None of the other concentrations of the clinically relevant particles were toxic. The commercial cobalt-chromium and alumina particles did not affect the viability of either the U937 histiocytes or the L929 fibroblasts.Thus at equivalent particle volumes the clinically relevant cobalt-chromium particles were more toxic then the alumina ceramic particles. This study has emphasised the fact that the nature, size and volume of particles are important in assessing biological effects of wear debris on cells in vitro.     

Isolation and characterization of UHMWPE wear particles down to ten nanometers in size from in vitro hip and knee joint simulators

There is currently considerable interest in the wear debris and osteolytic potential of different types of bearings used in total joint replacements. The biological activity of the wear debris is dependent on the size and volume of the particles produced. Wear volume also plays an important role in the functional biological activity of a joint replacement. In vitro studies have shown that crosslinking of ultra high molecular weight polyethylene (UHMWPE) acetabular cups and tibial trays produces a reduction in wear volume, and crosslinking has now been introduced clinically for both types of prostheses. Previous studies have identified both micron and submicron-sized polyethylene wear particles. The aim of this study was to characterize the wear and wear particles generated from moderately crosslinked GUR 1,020 GVF UHMWPE acetabular cups and tibial trays in hip and knee joint wear simulators down to 10 nanometers in size. The wear rates of the two prosthesis types were very similar at 25.6 +/- 5.3 mm(3) per million cycles for the hip prostheses and 22.75 +/- 5.95 mm(3) per million cycles for the knee prostheses. Nanometer-sized wear particles were isolated and characterized from both hip and knee simulator lubricants for the first time. Significantly higher numbers (p < 0.05) of particles in the nanometer (<0.1 microm) size range were produced by the hip prostheses compared to the knee prostheses. The knee prostheses produced larger particles, with the mode of particle size in the 0.1-1.0 microm size range, compared to <0.1 microm size range for the hip prostheses. In addition, the knee prostheses produced a greater volumetric concentration of wear particles in the 1.0-10 microm size range, and consequently lower specific biological activity and functional biological activity indices. These results indicated that the knee prostheses had a lower osteolytic potential compared to the hip prostheses.     

Long-term wear of ceramic matrix composite materials for hip prostheses under severe swing phase microseparation

The purpose of this study was to evaluate the long-term wear performance of alumina matrix composite (AMC) heads against alumina matrix composite inserts and alumina matrix composite heads against alumina (Al) inserts with the use of a hip-joint simulator incorporating severe swing phase joint microseparation. The wear of AMC on Al produced an average wear rate of 0.61 mm3/million cycles over the 5-million-cycle test duration. The wear of AMC on AMC produced an average wear rate of 0.16 mm3/million cycles over the 5-million-cycle test duration. Both the AMC on alumina and AMC on AMC produced significantly lower wear than previously tested HIPed alumina, where an average wear rate of 1.84 mm3/million cycles was reported over 5 million cycles. The wear mechanisms and wear debris of AMC on AMC and AMC on Al were similar to those observed in previous alumina retrieval studies with stripe wear caused by intragranular fracture and wear debris consisting of predominantly uniform 10-20-nm-sized particles and a few irregular particles up to 3 microm in size.     

Microseparation and stripe wear in alumina-on-alumina hip implants

The combination of materials that still has highest wear resistance for total hip replacement is ceramic-on-ceramic. However, brittleness is a major concern for ceramics: in vivo and in vitro studies on ceramic hip prostheses correlate microseparation with hip noise, ceramic wear, or ceramic liner damage. Ceramic microseparation can lead to edge load, ceramic head wear, and squeaking. The aim of this in vitro study was to investigate whether different angles of inclination influence the wear pattern of alumina-on-alumina hip joints with micro-separation during the swing phase. We also evaluated the wear rate obtained from this in vitro investigation with retrieval specimens obtained at 13 years' mean follow-up. The study was performed using a 12-station hip joint wear simulator (Shore Western, Monrovia, CA, USA) under bovine calf serum used as lubricant. Wear was evaluated by the gravimetric method and the test length was set at two million cycles. After two million cycles, a volumetric loss of 0.11 ±0.03 mm3 and 0.12 ±0.06 mm3 was observed, respectively, for 23° and 63° angles of inclination. In particular, the results obtained in this work revealed an increase of about 12-fold compared to previous results without microseparation conditions. No significant differences were observed between the two different inclinations on the wear patterns of the acetabular cups with a level of significance of a = 0.5. The location and general shape of the stripes wear were similar for the retrieved and simulator balls.     

Metal-on-metal bearing wear with different swing phase loads

There is currently much discussion about the most clinically relevant testing methods for evaluating total hip replacements. This study examined the effect of different swing phase loads, including microseparation, on the wear, friction, and wear particles of metal-on-metal (MOM) hip replacements. MOM hip replacements were tested for 5 million cycles with the use of a hip simulator; prostheses were tested with a low (100-N) and ISO (280-N) swing phase load, and under microseparation conditions. Increasing the swing phase load from 100 to 280 N in the same hip simulator increased the wear of the MOM hip replacements by over tenfold. Introducing microseparation into the gait cycle increased wear further, and stripe wear was observed on the femoral heads, accompanied by corresponding rim damage on the acetabular cups. No significant difference in wear particle size was observed between wear particles produced by low load and microseparation hip simulator conditions. Introducing microseparation into the hip simulator gait cycle increased the wear of MOM prostheses. Joint laxity and separation may lead to increased wear rates of MOM prostheses in vivo. Additionally elevated positive swing phase loads may also increase wear. Variable swing phase load conditions in vivo may contribute to variations in clinical wear rates.     

Characterization of worn alumina hip replacement prostheses

Alumina hip replacement prostheses have been analyzed following in vitro simulated microseparation. The worn surfaces of the alumina acetabular cup and femoral head were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) which identified four different wear zones. Focused ion beam (FIB) cross-sectioning was used to section the worn surface and produce 3D reconstructions of the subsurface damage. This showed that the subsurface fracture was predominantly intergranular, with occasional intragranular fracture. Significantly, in all cases, fracture was restricted to the outer layer of grains. The wear mechanisms leading to the generation of the stripe wear region on the worn alumina hip prostheses are proposed and microseparation is believed to play a critical role.     

Surface micro-analyses of long-term worn retrieved "Osteal" alumina ceramic total hip replacement

We analyzed wear pattern of long-term retrieved alumina-alumina hip prostheses from Osteal, which were implanted for 15-19 years. A comparison was carried out with our previous study of 17-year Biolox alumina-on-alumina hip prostheses, (Shishido et al., J Biomed Mater Res B 2003;67:638-647) and all-alumina total hip replacement run under microseparation simulator tests. Of particular interest was the occurrence of stripe wear in these first generation alumina ceramic bearings. Two balls of Osteal revealed only one stripe wear as did the respective liners on their rim areas. In these latter balls, the stripes were shallower than those previously observed in Biolox implants. A microscopic analysis of the bearing surface was carried out using scanning electron microscopy and fluorescence microprobe spectroscopy. On average, the Osteal retrievals had one grade lower wear than Biolox retrievals. Fluorescence microprobe maps showed that Biolox ball surfaces had higher compressive stress than the Osteal likely due to severe impingement and microseparation promoted by the bulky implant design.     

Severe wear from retrieved alumina-on-alumina coupled implant: a case report.

This study details the in vivo wear behavior of an alumina acetabular cup and a femoral head on a retrieved non-cemented hip prosthesis. A commercial alumina ceramic-on-ceramic prosthesis was retrieved from a patient previously treated for bilateral hip arthrosis in "coxa profunda". Massive wear was found on the retrieved alumina ceramic head and acetabular cup. The total measured penetration depth was 1.9 mm while the total calculated weight loss for the acetabular cup was 6.06 g. The study underlines the head-cup instability caused by cup loosening as major cause of severe ceramic wear.     

Ceramic bearing surfaces in total artificial joints: resistance to third body wear damage from bone cement particles

Studies of explanted Charnley hip prostheses have shown damage or scratching of the polished stainless steel femoral heads. This surface damage is probably due to third body wear by bone cement particles. Damaged femoral heads will produce increased wear rates of ultra high molecular weight polyethylene (UHMWPE) acetabular cups. Sliding wear tests carried out in the laboratory have shown that alumina ceramic counterfaces are more resistant to third body damage from bone cement particles than stainless steel counterfaces. The use of the ceramic femoral heads in artificial hip joints will help to preserve the smooth surface finish on the femoral bearing surface, which is necessary to ensure low wear rates of the UHMWPE cup throughout the lifetime of the prosthesis.     

Friction of total hip replacements with different bearings and loading conditions

Metal-on-ultra-high molecular weight polyethylene (UHMWPE) total hip replacements have been the most popular and clinically successful implants to date. However, it is well documented that the wear debris from these prostheses contributes to osteolysis and ultimate failure of the prosthesis, hence alternative materials have been sought. A range of 28 mm diameter bearings were investigated using a hip friction simulator, including conventional material combinations such as metal-on-UHWMPE, ceramic-on-ceramic (CoC), and metal-on-metal (MoM), as well as novel ceramic-on-metal (CoM) pairings. Studies were performed under different swing-phase load and lubricant conditions. The friction factors were lowest in the ceramic bearings, with the CoC bearing having the lowest friction factor in all conditions. CoM bearings also had low friction factors compared with MoM, and the trends were similar to CoC bearings for all test conditions. Increasing swing phase load was shown to cause an increase in friction factor in all tests. Increased serum concentration resulted in increased friction factor in all material combinations, except MoM, where increased serum concentration produced a significant reduction in friction factor.     

The use of dense alumina-alumina ceramic combination in total hip replacement

The purpose of this article was to review the laboratory and clinical performances since 1970 of a total hip prosthesis using alumina-alumina combination. The chemical and physical properties of dense alumina ceramic were studied in relation to biocompatibility, mechanical strength, and surface properties. Through the examination of 35 retrieved implants, it was found that the long-term success of alumina-alumina total hip replacement depends on both the ceramic microstructure (small grain size with uniform distribution, minimum porosity, absence of inclusions) and implant geometry (sphericity deviation +/- 1 micron, radius tolerance between components 7-10 microns). Alumina component wear and fractures have disappeared with the use of high-performance materials and severe manufacturing quality control. Examination of human biopsies from well-fixed prostheses showed that alumina particles deposits increase with time with only a low-grade macrophagic reaction. When loosening occurred, an inflammatory reaction appeared; this reaction was less striking than with loose metal-polyethylene prostheses, however. The long-term behavior of cementless alumina cup fixation depends upon initial positioning and stability; survivorship analysis of the cemented ceramic cups showed an 88% survival probability after 8 years with a 1.6% average annual probability of revision. The percentage of surviving was 100% after 8 years in patients who were less than 50 years old. Aseptic loosenings occurring at the cup-cement interface were assumed to be related to stress protection secondary to the high rigidity of the ceramic leading to a weakening of the spongious bone supporting the cement mantle. Good bone stock quality as well as high-quality ceramic appear to be the prerequisites for durable fixation of alumina sockets.     

Mixed oxides prosthetic ceramic ball heads. Part 3: effect of the ZrO2 fraction on the wear of ceramic on ceramic hip joint prostheses. A long-term in vitro wear study

Using ceramic materials it is possible to obtain a number of beneficial mechanical properties such as considerable hardness, good chemical resistance, high tensile strength, and a good fracture toughness. The use of ceramic-on-ceramic as bearing surfaces for hip joint prostheses has been reported to produce a lower wear rate than other combinations (i.e. metal-on-polyethylene and ceramic-on-polyethylene) in total hip artroplasty. These advantages may increase the life expectancy of hip implants and improve the life of patients. Two new types of mixed-oxide ceramics (alumina and yttria-stabilised zirconia) femoral heads and acetabular cups containing different ratios of alumina and zirconia were compared with pure commercial alumina in terms of wear behaviour in a hip joint simulator. Hip joint wear simulator studies were carried out with a full-peak load of 2030 N and a frequency of 1 Hz in bovine calf serum. After 10 million cycles the measured weight loss of all specimens was very low. However, the experimental results did not show any significant difference between the new experimental mixed-oxide ceramics prototype and the commercial ceramic material couplings.     

陶瓷对陶瓷的全髋关节置换

背景：目前陶瓷制造工艺方面仍在不断改进,陶瓷对陶瓷摩擦界面的假体成为关节外科领域关注的焦点,并取得了良好的临床疗效,然而随着陶瓷对陶瓷摩擦界面假体的广泛应用,出现了假体碎裂和高调摩擦音等一系列问题。 目的：探讨陶瓷对陶瓷全髋关节置换的初期临床疗效。 方法：对常熟市第一人民医院2006年1月至2010年6月间小于55岁行陶瓷对陶瓷全髋关节置换的50例患者进行随访,其中男19例( 20髋),女31例(33髋),平均年龄45岁,随访时间平均20(12-42)个月。置换前后均采用Harris评分进行疗效评估,影像学随访包括髋臼假体外展角和前倾角,假体松动采用Kawamura及Engh标准,骨溶解采用Engh标准,异位骨化依据Brooker法评价。 结果与结论：置换前Harris评分为(48.10±26.33)分,置换后为(91.10±19.78)分。置换后随访无患者有关节异响的主诉,未见假体松动,未发生假体周围感染,无可观察到的磨损和骨溶解,无明显异位骨化。其中,1例因髋臼陶瓷内衬碎裂翻修。可见陶瓷对陶瓷全髋关节置换对于年轻的骨质量较好的患者短期疗效显著,长期疗效有待于进一步随访。     

陶瓷-陶瓷界面和陶瓷-聚乙烯界面在全髋关节置换中疗效和安全性的Meta分析

BACKGROUND: Greatly importance has been attached to ceramic-on-ceramic bearing surface due to its excellent wear resistance. But the risks of squeaking and ceramic fracture also go with it. Up till now, the choice  between ceramic-on-ceramic and ceramic-on-polyethylene bearing surfaces in primary total hip arthroplasty remains controversial.  OBJECTIVE: To compare the clinical outcomes and safety between ceramic-on-ceramic versus ceramic-on-polyethylene bearing surfaces in total hip arthroplasty based on meta analysis. METHODS: We electronically searched databases including PubMed/Medline, Embase, Web of Science, Cochrane Collaboration database, Chinese Biomedical Literature Database (CBMdisc) and China National Knowledge Internet for randomized controlled trials on the comparison between ceramic-on-ceramic versus ceramic-on-polyethylene bearing surfaces in total hip arthroplasty from inception to January 2015. References of the included studies were also retrieved. Investigators severely selected the studies, extracted data and assessed the quality according to the inclusion and exclusion criteria. Then, meta-analysis was performed using RevMan 5.2 software. RESULTS AND CONCLUSION: Nine randomized controlled trials were included, involving 1 231 hips with ceramic-on-ceramic prosthesis and 932 hips with ceramic-on-polyethylene prosthesis. Meta analysis showed that both bearing surfaces achieved satisfied function recovery. But ceramic-on-ceramic had significantly increased risks of squeaking and ceramic fracture, meanwhile ceramic-on-polyethylene showed significantly higher wear rate. There were no significant differences in intra- or post-operative dislocation, osteolysis and other complications and prosthesis failure with any reason between two bearing surfaces. These results suggest that during the short- to mid-term follow-up period, no sufficient evidence can tell that ceramic-on-ceramic was obviously super than ceramic-on-polyethylene. Long-term follow-up is required for further evaluation.      

Advanced nanocomposite materials for orthopaedic applications. I. A long-term in vitro wear study of zirconia-toughened alumina

The use of ceramic-on-ceramic (alumina- and zirconia-based) couplings in hip joint prostheses has been reported to produce lower wear rates than other combinations (i.e., metal-on-polyethylene and ceramic-on-polyethylene). The addition of zirconia into an alumina matrix (zirconia-toughened alumina, ZTA) has been reported to result in an enhancement of flexural strength, fracture toughness, and fatigue resistance. The development of new processing routes in nonaqueous media has allowed to obtain high-density ZTA nanocomposites with a very homogeneous microstructure and a significantly smaller and narrower particle-size distribution of zirconia than conventional powder mixing methods. The aim of the present study was to set up and validate a new ZTA nanocomposite by testing its biocompatibility and wear behavior in a hip-joint simulator in comparison with commercial alumina and experimental alumina specimens. The primary osteoblast proliferation onto ZTA nanocomposite samples was found to be not significantly different from that onto commercial alumina samples. After 7 million cycles, no significant differences were observed between the wear behaviors of the three sets of cups. In this light, it can be affirmed that ZTA nanocomposite materials can offer the option of improving the lifetime and reliability of ceramic joint prostheses.     

Combining ageing and wear to assess the durability of zirconia-based ceramic heads for total hip arthroplasty

The degradation of zirconia-based ceramic components for total hip arthroplasty (head and cup) has been the topic of many works. However, the correlation between what is measured in vivo and what is expected from in vitro simulations on hip simulators may be sometimes feeble, especially where zirconia component are concerned, mainly due to a lack of representativeness of in vitro experiments. The present study seeks to explore the combined effects of hydrothermal ageing and wear on zirconia components. It shows that hydrothermal ageing increases the roughness of zirconia components, which in turn might increase the wear rate of the polyethylene counterparts. Moreover, the friction during hip simulation increases the ageing rate of the zirconia components. This auto-accelerating degradation may explain some of the poor long-term in vivo results of zirconia hip prostheses reported in the literature. Finally, it is shown that zirconia-toughened alumina components may be free from this combined degradation.