Wear analysis of retrieved ceramic-on-ceramic articulations in total hip arthroplasty: Femoral head makes contact with the rim of the socket outside of the bearing surface

We investigated articular bearing surfaces retrieved from three patients with ceramic-on-ceramic total hip arthroplasties using high-quality alumina. The duration of implantation was 3.5, 3.0, and 2.5 years, respectively. Dislocation of the hip joint after implantation did not occur in any patients. The retrieved prostheses were examined by stereomicroscopy and scanning electron microscopy (SEM). In the main load-bearing area, no wear marks were seen in any sockets. However, in all three cases, stripe scars were observed at the rim of the alumina inlay under stereomicroscopy, despite the lack of indentation in the socket and the stem, which suggests impingement. Such scars were not observed on the load-bearing surface. Under SEM, the scars showed excessive wear, including material excavation, that has not been observed in conventional hip simulator experiments. These findings are similar to those of experiments in which a simulator was programmed to distract the femoral head from the socket. The present results suggest that the femoral head can separate from the socket without neck-socket impingement in vivo.     

Mixed oxides prosthetic ceramic ball heads. Part 1: effect of the ZrO2 fraction on the wear of ceramic on polythylene joints.

Although mixed oxides ceramics have been indicated in the literature as a promising compromise between strength and wear, to the authors' knowledge no reports are available on the influence of the percentage of zirconia in ceramic femoral heads when sliding against polyethylene cups. Two types of mixed oxides ceramic ball heads (alumina plus, respectively, 60 and 80% of zirconia) were compared to pure zirconia and pure alumina heads in terms of wear behaviour against UHMWPE in a hip joint simulator. Polyethylene cups and ceramic femoral heads were fixed on a simulator apparatus with a sinusoidal movement and load in presence of bovine calf serum. The experimental results did not show significant difference between the two experimental ceramic materials or in comparison with pure materials. Considering that all specimens, regardless of the material, had the same level of surface roughness, this roughness factor seems to have a more relevant role than the mix of oxides used to manufacture the ceramic head. Wear tests are conducted on materials used in prosthetic hip implants in order to obtain quality control and to acquire further knowledge of the tribological processes that involve joint prostheses, therefore reducing the risk of implant failure of innovative prostheses.     

Isolation and morphological characterisation of UHMWPE wear debris generated in vitro

Wear tests are generally carried out on materials used in prosthetic hip implants, in order to obtain a better understanding of the tribological processes involved and improve the quality control of joint prostheses, directed towards reducing the risk of implant failure of innovative prostheses. Ceramic femoral heads of mixed alumina-zirconia oxides as well as zirconia and alumina single oxide heads were tested against UHMWPE acetabular cups in a hip joint simulator. Polyethylene cups and ceramic femoral heads were mounted in a simulator apparatus moving according to a sinusoidal function, under load and in the presence of bovine calf serum as lubricant. Wear particles were isolated from the bovine calf serum collected during the wear tests. An easy to follow method was used to separate the wear particles from the lubricant. Chemical digestive methods were used to separate the wear particles from the lubricant and the isolated particles were studied using scanning electron microscopy. The morphologies of the polyethylene debris showed considerable differences, both in size and shape of the particles, as a function of the coupled head material.     

An in vitro investigation of diamond-like carbon as a femoral head coating

Wear of polyethylene acetabular components of hip implants is a significant clinical problem. In prosthetic hip surgery, polyethylene wear is identified as a factor that limits the life of the implant; it is known that the production of debris can cause adverse tissue reactions that may lead to extensive bone loss around the implant, and consequently loosening of the fixation. A new class of so-called Diamond-Like Carbon coatings, applied to titanium femoral heads was compared to ceramic and metallic heads in terms of wear behavior against UHMWPE using a hip joint simulator with a bovine calf serum lubricant. A thin film of Diamond-Like Carbon was deposited directly onto titanium (Ti6Al4V) head using chemical vapor deposition. The wear of polyethylene coupled with Diamond-Like Carbon coated femoral heads was comparable to that obtained with the polyethylene coupled with commercial alumina femoral heads.     

Wear properties of alumina/zirconia composite ceramics for joint prostheses measured with an end-face apparatus

While only alumina is applied to all-ceramic joint prostheses at present, a stronger ceramic is required to prevent fracture and chipping due to impingement and stress concentration. Zirconia could be a potential substitute for alumina because it has high strength and fracture toughness. However, the wear of zirconia/zirconia combination is too high for clinical use. Although some investigations on composite ceramics revealed that mixing of different ceramics was able to improve the mechanical properties of ceramics, there are few reports about wear properties of composite ceramics for joint prosthesis. Since acetabular cup and femoral head of artificial hip joint are finished precisely, they indicate high geometric conformity. Therefore, wear test under flat contact was carried out with an end-face wear testing apparatus for four kinds of ceramics: alumina monolith, zirconia monolith, alumina-based composite ceramic, and zirconia based composite ceramic. Mean contact pressure was 10 MPa and sliding velocity was 40 mm/s. The wear test continued for 72 hours and total sliding distance was 10 km. After the test, the wear factor was calculated. Worn surfaces were observed with a scanning electron micrograph (SEM). The results of this wear test show that the wear factors of the both composite ceramics are similarly low and their mechanical properties are much better than those of the alumina monolith and the zirconia monolith. According to these results, it is predicted that joint prostheses of the composite ceramics are safer against break down and have longer lifetime compared with alumina/alumina joint prostheses.     

Low wear rate of UHMWPE against zirconia ceramic (Y-PSZ) in comparison to alumina ceramic and SUS 316L alloy

Partially stabilized zirconia ceramic is being recognized among ceramics for its high strength and toughness. With this ceramic, is possible to manufacture a 22-mm-size femoral head for low friction arthroplasty of the hip joint in association with an ultra-high-molecular-weight polyethylene socket. Wear-resistant properties of zirconia ceramic were screened on two principally different wear devices. Sterile calf bovine serum, physiological saline, and distilled water were chosen as the lubricant fluid media. Depending on the lubricant medium, the wear factor of polyethylene against zirconia ceramic counterfaces was 40 to 60% less than that against alumina ceramic counterfaces, and 5 to 10 times lower than with the SUS316L metal counterfaces. Polyethylene wear against metal was more susceptible in saline in which it had 2 to 3 times higher wear rate than with serum. On the other hand, different fluid media had little effect on polyethylene wear against ceramic counterfaces. In each set of tests, the wear factor obtained on an unidirectional wear device showed 10 to 15 times higher values, in comparison to the wear factor estimated on a reciprocating wear device.     

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.     

多孔钽棒改善股骨颈骨折术后股骨头缺血性坏死患者的髋关节功能：随机对照临床试验方案

BACKGROUND:After femoral neck fracture, avascular necrosis of the femoral head occurs because of insufficient blood supply to the femoral head, resulting in increased difficulty in treatment, and greatly influencing the recovery of hip joint function. Core decompression and bone grafting is a common treatment method of avascular necrosis of the femoral head. A porous tantalum rod is a bone trabecula-like metal implant that is used to support weight-bearing area of necrotic bone, prevent further collapse of the necrotic area, and thereby exhibits favorable effects in the early treatment of avascular necrosis of the femoral head. Few randomized controlled studies are reported on porous tantalum rod implantation for treatment of avascular necrosis of the femoral head after femoral neck fracture surgery. OBJECTIVE: To investigate whether porous tantalum rod implantation can improve the hip joint function of patients with avascular necrosis of the femoral head subjected to femoral neck fracture surgery. METHODS: This is a prospective, single-center, randomized, controlled, open trial, which will be performed in the Department of Orthopedic Trauma, Qinghai University Affiliated Hospital, China. A total of 100 patients with avascular necrosis of the femoral head subjected to femoral neck fracture surgery will be randomly assigned to undergo core decompression and porous tantalum rod implantation (experimental group, n=50) or only core decompression (control group, n=50). All patients will be followed up for 1 year. Primary outcome measure is the percentage of patients whose hip joint function is graded as excellent as per Harris scores 12 months after surgery in total patient number in each group, which will be used to evaluate the recovery of hip joint function. Secondary outcome measures include (1) the percentage of patients with excellent hip joint function 1 and 6 months after surgery in total patient number in each group; (2) Visual Analogue Scale spine score prior to and 1, 6 and 12 months after surgery, which will be used to evaluate the severity of pain; (3) the percentage of patients presenting with femoral head collapse, prosthesis loosening and peri-prosthesis infection 6 and 12 months after surgery, which will be used to evaluate the biocompatibility of biomaterial with host; and (4) incidence of complications 6 and 12 months after surgery, which will be used to evaluate the safety of porous tantalum rod implantation. This study protocol has been approved by the Medical Ethics Committee of Qinghai University Affiliated Hospital of China (approval number: QHY1016B) and will be performed in accordance with the guidelines of the Declaration of Helsinki, formulated by the World Medical Association. Signed informed consent regarding trial procedure and treatment will be obtained from each patient.  DISCUSSION: This study is powered to validate the biocompatibility and therapeutic effects of porous tantalum rods in the treatment of avascular necrosis of the femoral head after femoral neck fracture surgery, which hopes to provide a novel persuasive surgical treatment method for this disease.     

Wear resistance of artificial hip joints with poly(2-methacryloyloxyethyl phosphorylcholine) grafted polyethylene: Comparisons with the effect of polyethylene cross-linking and ceramic femoral heads

Aseptic loosening of artificial hip joints induced by wear particles from the polyethylene (PE) liner remains the ruinous problem limiting their longevity. We reported here that grafting with a polymer, poly(2-methacryloyloxyethyl phosphorylcholine (MPC)) (PMPC), on the PE liner surface dramatically decreased the wear production under a hip joint simulator condition. We examined that the effect of properties of both PE by cross-linking and femoral head by changing the materials on wearing properties of PE. The PMPC grafting on the liners increased hydrophilicity and decreased friction torque, regardless of the cross-linking of the PE liner or the difference in the femoral head materials. During the hip joint simulator experiments (5 × 10⁶ cycles of loading), cross-linking caused a decrease of wear amount and a reduction of the particle size, while the femoral head materials did not affect it. The PMPC grafting abrogated the wear production, confirmed by almost no wear of the liner surface, independently of the liner cross-linking or the femoral head material. We concluded that the PMPC grafting on the PE liner surpasses the liner cross-linking or the change of femoral head materials for extending longevity of artificial hip joints.     

The effect of surface topography of retrieved femoral heads on the wear of UHMWPE sockets

The study was undertaken to investigate the association, if any, between the surface roughness of 35 explanted femoral heads and the clinical wear factors of the corresponding polyethylene sockets. The wear of the socket was measured using a shadowgraph technique. The surface topography was investigated using a Rodenstock RM 600 non-contacting profilometer, and six parameters were used to characterise the roughness. Further, qualitative inspections of the femoral surface were undertaken using both a Joel JSM-IC-848 scanning electron microscope and a Zeiss Axiotech microscope with a differential interference contrast facility. Two parameters were found to correlate with the clinical wear factor, namely the skewness of the amplitude distribution function, Sk, and the arithmetic mean roughness, R_a. Simple parameters describing the peak heights of the asperities were found not to have a significant association with the clinical wear factor. The exponent in the power relationship between the arithmetic mean roughness and k_clinical was found to be equal to 0.5 (SE: 0.2). This value is significantly smaller than that found in laboratory experiments and may be due to the non-uniform nature of the roughening of the femoral head, three-body wear and the effect of other clinical factors on the wear process. Further, extremely strong correlations were detected between the differing roughness parameters, which would suggest that any attempt to deduce which one is the most important in affecting the wear of the polymeric counterface is fraught with difficulty. However, further investigation of those parameters, such as the reduced peak height or the material filled profile peak area, which may better describe the effect of the counterface on the wear of the UHMWPE surface would appear to be prudent.     

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.     

髋关节表面置换术治疗Crowe Ⅰ、Ⅱ型髋关节发育不良

目的 研究Crowe Ⅰ型和Ⅱ型髋关节发育不良(DDH)患者行髋关节表面置换术(HRA)的临床结果。方法 前瞻性将2005年3月—2006年12月80例Crowe Ⅰ 型和Ⅱ型DDH患者随机分入HRA组和全髋关节置换术(THR)组。HRA组中3例改行THR、3例失随访,THR组中2例失随访,故34例37髋接受HRA,38例39髋接受THR。在术后6周、3个月、1年,以后每年1次进行随访,接受放射学及临床评价。结果 HRA组和THR组分别平均随访59.4个月(52～70个月)及60.6个月(50～72个月),2组都未出现假体失败。2组间术后Harris评分差异无统计学意义(P=0.073),但HRA组的屈髋活动度显著优于THR组(P＜0.01)。两组间髋臼假体的平均外展角差异无统计学意义(P=0.982)。HRA组的髋臼假体直径大于THR组(49.5 mm vs 46.1 mm,P=0.001)。结论 Crowe Ⅰ型和Ⅱ型DDH行HRA的临床结果与THR相近,但HRA术后屈髋活动度更佳,HRA在使用较大股骨假体的同时,髋臼会有额外骨量丢失。     

Total surface hip arthroplasty in dogs using a fiber metal composite as a fixation method

A total hip surface replacement was performed on 13 adult mongrel dogs using a porous fiber metal composite for fixation to bone. Titanium fiber composite rings were molded onto cylindrical acetabular prostheses, and cobalt-chrome fiber inserts were sintered onto the cast cobalt-chrome femoral components. The animals were allowed unrestricted walking. Four dogs were sacrificed between 3 and 5 weeks, five at 7 weeks, one with a femoral neck fracture at 12 weeks, and three at 26 weeks. Bone ingrowth was accomplished in 20 of the 26 prosthetic components. This included 12 femoral components and eight acetabular. The main reason for failure appeared to be inadequate primary fixation, secondary to either poor design or technical difficulties experienced during the surgical procedure.     

髋关节表面置换术治疗Crowe Ⅰ、Ⅱ型髋关节发育不良

目的研究CroweI型和Ⅱ型髋关节发育不良（DDH）患者行髋关节表面置换术（HRA）的临床结果。方法前瞻性将2005年3月—2006年12月80例CroweI型和Ⅱ型DDH患者随机分入HRA组和全髋关节置换术（THR）组。HRA组中3例改行THR、3例失随访,THR组中2例失随访,故34例37髋接受HRA,38例39髋接受THR。在术后6周、3个月、1年,以后每年1次进行随访,接受放射学及临床评价。结果HRA组和THR组分别平均随访59．4个月（52～70个月）及60．6个月（50—72个月）,2组都未出现假体失败。2组间术后Harris评分差异无统计学意义（P：0．073）,但HRA组的屈髋活动度显著优于THR组（P〈0．01）。两组间髋臼假体的平均外展角差异无统计学意义（P=0．982）。HRA组的髋臼假体直径大于THR组（49．5ramvs46．1mm,P=0．001）。结论CroweI型和Ⅱ型DDH行HRA的临床结果与THR相近,但HRA术后屈髋活动度更佳,HRA在使用较大股骨假体的同时,髋臼会有额外骨量丢失。     

Phase transformation, roughness, and microhardness of artificially aged yttria- and magnesia-stabilized zirconia femoral heads

Yttria-stabilized zirconia ceramic (Y-TZP) has been used in total hip arthroplasty for many years but is susceptible to low-temperature aging. Medical-grade magnesia-stabilized zirconia (Mg-PSZ) is less commonly used; however, it has been shown to resist phase transformation. The purpose of this study was to directly compare the effects of artificial aging on phase transformation, surface roughness, and Vickers microhardness on Y-TZP and Mg-PSZ femoral heads. Y-TZP and Mg-PSZ heads were artificially aged in an autoclave in stages up to a total of 49 h. The surface roughness of Y-TZP significantly increased with each stage of artificial aging. Y-TZP heads aged for 49 h had a significantly higher monoclinic phase concentration and roughness, and a significantly lower microhardness, than nonaged Y-TZP heads. Artificial aging also caused the surface of Y-TZP to exhibit a lumpy "orange peel"-like appearance with a significantly higher mean peak height, suggesting that artificial aging causes individual grains to be pushed out of the surface. In contrast, artificial aging did not significantly affect the properties of Mg-PSZ heads. These findings suggest that Mg-PSZ is a satisfactory material for orthopaedic implant use, while Y-TZP, in the form tested, is not adequately stable for use as a bearing surface.     

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.     

动力化髋关节外固定器研制及其临床试用

目的 研制动力化髋关节外固定器,并辅助带血管蒂的髂骨瓣移植治疗股骨头坏死,评价其治疗效果.方法 根据髋关节的解剖学和运动学特点,设计动力化髋关节外固定器;对4例中年股骨头坏死患者,采用动力化髋关节外固定器辅助带血管蒂的髂骨瓣移植治疗.术前、术后进行Harris评分和常规的X线检查,并进行对比.结果 经12～30个月的随访,Harris评分由术前的平均56分提高到术后平均81分,良3例,可1例.X线检查,移植的髂骨瓣愈合良好,关节间隙平均4mm.结论 通过本组病例观察,动力化髋关节外固定器可维持髋关节的间隙,带血管蒂的髂骨瓣可恢复股骨头的血运,两者技术的结合使用较好地解决在股骨头修复期早期功能锻炼的问题.     

Alumina-alumina artificial hip joints. Part II: characterisation of the wear debris from in vitro hip joint simulations

Until recently it was not possible to reproduce clinically relevant wear rates and wear patterns in in vitro hip joint simulators for alumina ceramic-on-ceramic hip prostheses. The introduction of microseparation of the prosthesis components into in vitro wear simulations produced clinically relevant wear rates and wear patterns for the first time. The aim of this study was to characterise the wear particles generated from standard simulator testing and microseparation simulator testing of hot isostatically pressed (HIPed) and non-HIPed alumina ceramic-on-ceramic hip prostheses, and compare these particles to those generated in vivo. Standard simulation conditions produced wear rates of approximately 0.1 mm3 per million cycles for both material types. No change in surface roughness was detected and very few wear features were observed. In contrast, when microseparation was introduced into the wear simulation, wear rates of between 1.24 (HIPed) and 1.74 mm3 per million cycles (non-HIPed) were produced. Surface roughness increased and a wear stripe often observed clinically on retrieved femoral heads was also reproduced. Under standard simulation conditions only nanometre-sized wear particles (2-27.5 nm) were observed by TEM, and it was thought likely that these particles resulted from relief polishing of the alumina ceramic. However, when microseparation of the prosthesis components was introduced into the simulation, a bi-modal distribution of particle sizes was observed. The nanometre-sized particles produced by relief polishing were present (1-35nm). however, larger micrometre-sized particles were also observed by both transmission electron microscopy (TEM) (0.021 microm) and scanning electron microscopy (SEM) (0.05-->10 microm). These larger particles were thought to originate from the wear stripe and were produced by trans-granular fracture of the alumina ceramic. In Part I of this study, alumina ceramic wear particles were isolated from the periprosthetic tissues from around Mittelmeier ceramic-on-ceramic hip prostheses. Characterisation of the particles by TEM and SEM revealed a bi-modal size distribution. SEM analysis revealed particles in the 0.05-3.2 microm size range. and TEM revealed particles in the 5-90 nm size range, indicating that microseparation of the prosthesis components may be a common event in vivo. This study (Part II) has revealed that the introduction of microseparation of the prosthesis components during the swing phase of the wear simulation reproduced clinically relevant wear rates, wear patterns and wear particles in in vitro hip joint simulators.     

Crack growth resistance of alumina, zirconia and zirconia toughened alumina ceramics for joint prostheses.

Mono-phase bio-ceramics (alumina and zirconia) are widely used as femoral heads in total hip replacements (THR) as an alternative to metal devices. Unfortunately, the orthopaedic community reports significant in-vivo failures. Material scientists are already familiar with composites like alumina zirconia. Since both are biocompatible, this could prove to be a new approach to implants. This paper deals with a new generation of alumina-zirconia nano-composites having a high resistance to crack propagation, and as a consequence may offer the option to improve lifetime and reliability of ceramic joint prostheses. The reliability of the above mentioned three bio-ceramics (alumina, zirconia and zirconia toughened alumina) for THR components is analysed based on the study of their slow crack-growth behaviour. The influence of the processing conditions on the microstructure development, of the zirconia toughened alumina composites and the effect of these microstructures, on its mechanical properties, are discussed.     

股骨头髓芯减压为基础治疗早期股骨头坏死

背景：髓芯减压治疗早期股骨头坏死效果较好,而且髓芯减压方法简单易行,即使远期治疗效果不理想也不影响行人工全髋关节置换。 目的：探讨以股骨头髓芯减压为基础的3种方法治疗早期股骨头坏死的临床疗效。 方法：根据国际骨循环研究学会(Association Research Circulation Osseous,ARCO)股骨头坏死分期标准,纳入股骨头坏死患者46例(61髋),Ⅰ期21例(29髋),Ⅱ期25例(32髋)。其中15例(23髋)行单纯髓芯减压治疗,18例(25髋)行髓芯减压联合自体骨髓单个核细胞移植治疗,13例(13髋)行髓芯减压联合多孔钽棒置入治疗。 结果与结论：全部患者均获12个月随访,3组患者末次随访时髋关节Harris评分均高于术前(P < 0.01),末次随访时联合细胞移植组和联合多孔钽棒组Harris评分高于单纯髓芯减压组(P < 0.01),而联合细胞移植组和联合多孔钽棒组比较差异无显著性意义(P > 0.05)。髋关节X射线检查：单纯髓芯减压组2例(3髋)发展为塌陷、联合细胞移植组1例(1髋)发展为塌陷,联合多孔钽棒组2例(2髋)出现塌陷。结果可见以股骨头髓芯减压为基础的3种方法治疗早期股骨头坏死均有效,其中髓芯减压联合自体骨髓单个核细胞移植或多孔钽棒置入近期疗效优于单纯髓芯减压治疗。