Background. Theoretically, improved material properties of new alumina matrix composite (AMC) material, Delta ceramics, are expected to decrease concerns associated with pure alumina ceramics and allow manufacturing thinner liners and consequent larger heads. However, limited short-term clinical results are available and mid-term results of these effects are unclear. Questions/Purposes. (1) Does AMC material decrease the rate of ceramic fracture and noise, concerns of previous-generation ceramics, following change of material properties? (2) Does the possible use of larger heads consequent to manufacturing thinner liners decrease dislocation rate and affect inguinal pain? (3) Do any other complications associated with the use of AMC ceramics occur?. Materials and Methods. One-hundred cementless primary total hip arthroplasties (THAs) using AMC ceramic bearings were performed consecutively by single surgeon. The mean follow-up period was 5.4 years (range, 5.0 to 5.7) and average age at the time of arthroplasty was 54.7 years. Prostheses with identical design and Biolox® Delta ceramics were used in all patients. Clinical evaluation included the occurrence of inguinal pain and noise which was classified into squeaking, clicking, grinding and popping. Ceramic fracture, dislocation and any other complications associated with the use of AMC ceramics were also investigated. Result. No ceramic fracture occurred and noise was reported in three patients (3.2%); three subjective clicking, but no squeaking. Single event of perioperative dislocation due to incompliance occurred in one hip (1.1%) and inguinal pain was reported in two hips (2.1 %); neither evidence of iliopsoas tendinitis on ultrasonography, nor association with ceramic head size (p>0.05). Liner dissociation following initial square seating was shown immediately after surgery in one hip (1.1%) and underwent revision THA. Conclusion. Improved material properties combined with the possible use of larger-diameter head make AMC ceramics a promising alternative bearing option with reduced risk of ceramic fracture, squeaking and dislocation. In spite of these encouraging results, however, meticulous technical precautions such as square seating and proper impaction in particular, should be taken during whole process of liner insertion

In total hip arthroplasty (THA), aseptic loosening induced by polyethylene (PE) wear debris is the most important cause that limits the longevity of implants. Abrasive wear generated through the mechanism such that micrometer-roughened regions and small asperities on the metallic femoral heads surface locally plow through the PE cup surface. Abrasive wear results in the PE material being removed from the track traced by the asperity during the motion of the metallic femoral heads surface. For the purpose of reducing wear, alumina ceramics was introduced in Europe and Japan in 1970s. The clinical results of ceramic-on-PE bearings regarding the wear resistance have been superior to that of the metal-on-PE bearings. Compared with Co–Cr–Mo alloys, alumina ceramics is advantageous for precision machining because of its higher hardness, enable to form spherical and smooth surface. The fracture resistance of the alumina ceramics itself is related to grain size; the grain size reduction leads to the improvement of its resistance. In this study, we evaluated the roundness and the roughness of retrieved two distinct alumina ceramics having different grain size, and Co–Cr–Mo alloy heads. Fourteen retrieved alumina ceramic femoral heads; ten heads with a diameter of 28 mm made of small grain size alumina (SG-alumina; mean grain size is 3.4 μm) with clinical use for 16–28 years and four heads with a diameter of 26 mm made of extra-small grain size alumina (XSG-alumina; mean grain size is 1.3 μm) with clinical use for 14–19 years, were examined. Six retrieved Co–Cr–Mo alloy femoral heads with a diameter of from 22 to 32 mm with average clinical use for 12–28 years were examined. SG-alumina and XSG-alumina heads showed significantly lower roundness compared with Co–Cr–Mo alloy heads, due to higher precision machining [Fig. 1]. The surface roughness for the contact area of the heads increased in order of XSG-alumina, SG-alumina and Co–Cr–Mo alloy. The surface roughness of the non-contact area for all kinds of heads was lower than that for the contact area [Fig. 2]. Surface profiles of the SG-alumina and XSG-alumina showed the reentrant surface while Co–Cr–Mo alloy heads showed the protrusion surface. The roundness and roughness of the Co–Cr–Mo alloy or ceramic surface and the presence or absence of hard third-body particles correlate to the amount of abrasive PE wear. When the third-body was entrapped during the clinical use, a reentrant surface might be formed on the ceramic while protrusion surface formed on the Co–Cr–Mo alloy. The differences in clinical results may be due in part to the influence of third-body particles. The ceramic becomes more resistant than Co–Cr–Mo alloy against the scratching by the entrapped abrasive contaminants because of its harder surface. From the good clinical results of more than 20 years using SG-alumina, the greater long term clinical results using XSG-alumina will be expected

Oxide ceramics, such as alumina and zirconia have been used extensively in arthroplasty bearings to address bearing wear and mitigate its delayed, undesirable consequences. In contrast to oxide ceramics that are well-known to orthopaedic surgeons, silicon nitride (Si. 3. N. 4. ) is a non-oxide ceramic that has been investigated extensively in very demanding industrial applications, such as precision bearings, cutting tools, turbo-machinery, and electronics. For the past four years, Si. 3. N. 4. has also been used as a biomaterial in the human body; specifically in spinal fusion surgery. As a implantable biomaterial, Si. 3. N. 4. has unique properties, such as high strength and fracture toughness, inherent chemical and phase stability, low wear, proven biocompatibility, excellent radiographic imaging, antibacterial advantages, and superior osteointegration. This property combination has proven beneficial and desirable in orthopaedic implants made for spinal fusion, spinal disc reconstruction, hip and knee arthroplasty, and other total joints (Fig. 1). The physical properties, shapes, sizes and surface features of Si. 3. N. 4. can be engineered for each application – ranging from dense, finely polished articulation components, to highly porous scaffolds that promote osteointegration. Both porous and polished surfaces can be incorporated in the same implant, opening a number of opportunities for arthroplasty implant design. Crack propagation modes for in situ toughened Si. 3. N. 4. differ favorably from those of conventional ceramics, rendering Si. 3. N. 4. extremely resistant to catastrophic failure in vivo (Fig. 2). Most significantly, our recent work has shown that Si. 3. N. 4. is resistant to bacterial biofilm formation, colonization and growth, when compared to medical-grade PEEK and titanium. These anti-infective characteristics are particularly valuable for in vivo implantation. We will present the unique properties and characteristics of Si. 3. N. 4. , and compare these to other ceramic and non-ceramic biomaterials. Si. 3. N. 4. was once used only in industrial applications, but early data show that this novel biomaterial is positively impacting orthopaedic care and will continue to do so into the future

INTRODUCTION. Wear, aseptic loosening, dislocation, corrosion and prosthetic joint infection (PJI) are major factors leading to revision of THA. The effect of using ceramic components to address these issues was investigated to determine their behaviour and potential benefit. METHODS. a) Wear determination in off-normal conditions. A series of CoC articulations (32mm) was evaluated using a hip simulator (ISO 14242) up to 4 million cycles in presence of fine alumina particles (48mg/ml). Wear was measured gravimetrically. b) Friction moment determination. Friction moments were measured in a hip simulator with 25% newborn calf serum as lubricant. CoC, CoPE, MoPE, MoXLPE and CoXLPE with articulating diameters ranging between 28 and 40mm were used. The cup was inclined to a constant angle of 33° and rotated ±20° sinusoidally around a horizontal axis at 1Hz. Peak friction moments were measured around the cup rotation axis during a constant joint force period of 1700N between 200 and 210 seconds. c) Infections. Four databases were analysed and additionally data from registers and literature were reviewed to determine the risk of revision for prosthetic joint infection (PJI) dependence on the bearing. Only data for cementless THA were used. Several studies also included analysis of several confounding factors like age at surgery, BMI, pathology, etc. using Cox multivariate analysis. RESULTS. a) Wear determination in off-normal conditions. Loading the test medium with alumina particles didn't produces detectable wear. Opaque areas appeared only after 3 million load cycles, but the wear-rate remained within the gravimetric measurement detection limit (about 0.1–0.2mg) indicating the still extremely low wear-rate of the tested couplings. b) Friction moment determination. The highest moments were measured for metal heads; the lowest for CoC bearings. 40mm CoC bearing showed a similar friction moment like 28mm bearings when coupled with a XLPE liner. c) Infections. The rate of revisions for PJI for 500'749 patients from various studies was in the range of 0.2 to 1.1%. Age at surgery and BMI did not influence septic loosening, while the bearing did; sometimes significant. The trend was identical for all seven sources and ceramic components resulted in a lower incidence of revisions for up to 60%. CONCLUSION. The wear of CoC articulations is extremely low even in a heavily contaminated environment with fine hard particles. Such high scratch resistance makes CoC the preferable revision solution in THA. Friction moments with CoC are the lowest, even with large diameter bearings. The low friction moments of ceramics lower the stresses at the modular and also bone interface and can affect the outcome of THA. Revisions due to infection seem to be also dependent on the bearing couple with a positive influence of ceramic components. Although due to the complex reasons for infections only a trend, CoP and CoC has been identified to mitigate the risk of PJI

Introduction. Silicon nitride (Si3N4) is a ceramic material presently implanted during spine surgery. It has a fortunate combination of material properties such as high strength and fracture toughness, inherent phase stability, scratch resistance, low wear, biocompatibility, hydrophilic behavior, easier radiographic imaging and resistance to bacterial biofilm formation, all of which make it an attractive choice for orthopaedic applications beyond spine surgery. Unlike oxide ceramics, (e.g., alumina or Al2O3) the surface chemistry and topography of Si3N4 can be precisely engineered to address in vivo demands. Si3N4 can be manufactured to have an ultra-smooth, or highly fibrous, or porous morphology. Its chemistry can be varied from that of a silica-like surface composed of silanol moieties to one which is predominately comprised of silicon-amine functional groups. Methods. In the present study, a Si3N4 bioceramic formulation was exposed to thermal, chemical, and mechanical treatments in order to induce changes in surface composition and features. The treatments included grinding and polishing, etching in hydrofluoric acid solution, and heating in nitrogen or air. Resulting surfaces were characterized using a variety of microscopy techniques to assess morphology. Surface chemical and phase composition were determined using x-ray photoelectron and Raman spectroscopy, respectively. Streaming potential measurements evaluated surface charging, and sessile water drop techniques assessed wetting behavior. Results. Induced changes to surface morphology and wetting behavior are shown in Figure 1. A wide variety of wetting behavior was observed, ranging from moderate hydrophilicity (θ ∼60°) in the case of untreated surfaces to extreme hydrophilicity (θ <10°) in the case of surfaces subjected to heat treatments in different atmospheres. Figure 2 shows the zeta potential as a function of solution pH for the surfaces shown in Figure 1. All samples exhibit strong negative surface charging at homeostatic pH (−40 mV or more), and the oxidized sample exhibits extremely strong charging (−75 mV). Conclusions. Our data show that Si3N4 is a facile biomaterial whose material properties can be engineered and optimized for specific applications. This work provides a basis for future in vitro and in vivo studies which will examine the effects of these treatments on important orthopaedic properties such as friction, wear, protein adsorption, bacteriostasis and osseointegration

Introduction. Looking for optimal solutions to wear risks evident in total hip arthroplasty (THA), silicon nitride ceramic bearings (Si. 3. N. 4. ) are noted for demanding high-temperature applications such as diesel engines and aerospace bearings. As high-strength ceramic for orthopedic applications, Si. 3. N. 4. offers improved fracture toughness and fracture strength over contemporary aluminas (Al. 2. O. 3. ). Our pilot studies of Si. 3. N. 4. in 28mm diameter THA showed promising results at ISTA meeting of 2007. 1. In this simulator study, we compared the wear resistance of 40mm to 28mm diameter Si. 3. N. 4. bearings. The 28mm and 40mm bearings (Fig. 1) were fabricated from Si. 3. N. 4. powder (Amedica Inc, Salt Lake City, UT). 1. Wear tests run were run at 3kN peak load in an orbital hip simulator (SWM, Monrovia, CA) and. The lubricant was standard bovine serum (Hyclone: diluted to 17 mg/ml protein concentration). Wear was measured by gravimetric method and wear-rates calculated by linear regression. SEM and interferometic microscopic was performed at 3.5-million cycles (3.5Mc) to 12Mc. The simulator was run to 3.5Mc duration with no consistent weight-loss trends. The bearings could show either small positive or negative weight fluctuations in an unpredictable manner (Fig. 2). Surface analysis showed protein layers up to 3μm thick, furrowed due to abrasion by small particles (Fig. 3). The low ceramic wear was camouflaged by protein contaminants alternatively forming and shedding. From 3.5 to 12.8Mc duration we experimented with various detergents and wash-procedures, all to no avail. Protein coatings were also more prevalent on 44 mm heads, likely due to frictional heating by the larger diameter effect. Selected heads were washed with a mild acid solution - the cumulative effect appeared to be removal of some protein layers, but not in a predictable manner. The Si. 3. N. 4. ceramic is used in demanding industrial applications and it is therefore unfortunate that we are yet not able to quantify the actual wear performance of Si. 3. N. 4. / Si. 3. N. 4. bearings (COC). The contaminating protein layers combined with low-wearing silicon nitride obscured the actual wear data. This has also been a problem in prior studies with alumina and zirconia bearings. Considerable challenges still stand in the way of the optimal biomaterials choices that will result in reduced risk of failure while providing extended lifetimes. Thus important issues remain unsolved and call for innovative solutions. Searching for a more effective ‘wear-measurement’ remedy, we noted that abrasive slurries of bone cement (PMMA) used in contemporary simulator studies were effective in promoting adverse wear in polyethylene bearings. These investigations also revealed that PMMA debris did not damage CoCr heads. 2,3. , alumina heads. 4,5. or diffusion-hardened zirconia heads (ZrDH). 6. We can therefore speculate at this ISTA meeting of 2014 that future ceramic wear tests should incorporate PMMA slurries. Here a new hypothesis can be formulated, that PMMA particulates will provide a continual and beneficial removal of contaminating proteins from the ceramic surfaces (see Fig. 3) and thereby aid definition of low-wearing COC bearings such as Si. 3. N. 4. . The application of non-oxide ceramics such as silicon nitride presented here may become a viable alternative for THA designs of next decade

Introduction. Oxide-based alumina (Al2O3) is used to manufacture femoral heads for total hip arthroplasty (THA). Silicon nitride (Si3N4) is a non-oxide ceramic used to make spinal implants. Ceramic materials are believed to be bioinert, (i.e., stable under hydrothermal conditions). Indeed, clinical data have shown 15–20 year longevity of Al2O3 bearings in THA. In this work, we examined the surfaces of Al2O3 and Si3N4 after exposure to physiologic conditions to see if these ceramics are truly inert. Materials and Methods. Four self-mated Ø28 mm diameter Al2O3 femoral heads (n=2 each of BIOLOX®forte, CeramTec, Plochingen, Germany; and BIOCERAM®, Kyocera Co., Kyoto, Japan), were retrieved during revision THA, between 7.7–10.7 years post-implantation. To simulate in vivo material aging, comparable, new Al2O3 and Si3N4 femoral heads (AMEDICA Corporation, Salt Lake City, UT, USA) were exposed to autoclave conditions (100°C-121°C; 300 hrs; n=3 heads, per material). Advanced Raman and cathodoluminescence spectroscopy, and electron microscopy were used to examine surface characteristics of each specimen, and quantify oxygen ion vacancy formation and composition. Results. The naturally hydroxylated free surfaces of retrieved Al2O3 demonstrated lattice dissociation. Dehydroxylation of Al2O3 produced hydroxyls and proton radicals, which in turn promoted the formation of surface vacancies for preserving electrical charge neutrality. During frictional sliding of Al2O3, the continuous formation, subsequent adsorption, and frictional removal of hydroxylated sites repeatedly created and annihilated a population of different oxygen-vacancy sites. Moreover, protein by-products and in vivo released ions sub-valent with respect to Al3+ (e.g., Ca2+, Mg2+, and Na+) were found to preferentially link to oxygen-vacancy sites, inducing irreversible stoichiometric alterations of the Al2O3 surface. Oxygen vacancy formation was seen in all samples, (i.e., all retrievals and all in vitro hydrothermally exposed samples). Cation substitution and spinel formation were only observed in retrievals because these cations are not available during in vitro testing, (i.e., Ca2+, Mg2+ and Na+ come from the synovial fluid). In contrast, Si3N4 surfaces showed no evidence of direct hydrogen bond formation, and therefore no dissociative interaction with water molecules, when subjected to accelerated aging conditions (Fig. 1). Discussion. Because of its molecular polarity, water can dissolve ionic substances, since the ionic compound interacts with either side of the water dipole. This phenomenon leads to dissociation of the ionic molecule by dehydroxylation. Our results show that Si3N4 surfaces are stable in hydrothermal environments. In contrast, Al2O3 surfaces demonstrate surface changes under in vivo and in vitro conditions because of modifications of the lattice structure (e.g., vacancy generation and formation of a soft MgAl2O4 spinel phase), which alters local mechanical properties and tribological wear resistance. Cations, such as Na+ are released from dilution of sodium hyaluronate; a phenomenon that occurs in patients with rheumatoid arthritis. Conclusion. These data suggest that surface dehydroxylation may lead to the long-term in vivo degradation of Al2O3 bearings in THA. Covalently-bonded bioceramics, such as Si3N4 are impervious to such degradation. Si3N4 may be truly bioinert in vivo, ensuring multi-decade durability and superior performance of orthopaedic bearings

One cementless cup which had porous outer surface with Apatite-Wollastonite glass ceramic (AWGC) coating, was revised 13 years after primary THA because of massive osteolysis expanded to medial iliac wall along the screws. While many retrieved studies of hydroxyapatite-coated cup have been reported, there has been no report on the retrieved cup with AWGC coating. The purpose of this study was to describe this rare case in detail, confirm the bone ingrowth to the porous cup, and discuss on the effectiveness of porous surface with AWGC coating. Case. The patient was a 64 old woman and complained of chronic mild pain around her left groin region. X-ray examination revealed that osteolysis had been expanding around the screws and extended proximally. The revision surgery was performed for the massive osteolysis through Hardinge antero-lateral approach. The retrieved implants included a cementless cup made of titanium alloy (QPOC cup, Japan Medical Materirals Inc.(JMM) Osaka, Japan), the outer surface of which was plasma-sprayed with titanium for porous formation and coated with AWGC in the deep layer. It was found that the polyethylene liner was destructed partially in the supero-lateral portion, but the cup was well fixed to the bone. The bone-attached area was found to be dispersed over the porous surface of the hemispherical cup. Histological examination revealed that matured bony tissue intruded into the porous surface of the cup, and contacted to bone directly, which was also demonstrated in the back-scattered electron image. It was also demonstrated that there were residual silicon (Si) rich regions on the porous surface by the SEM-EDX analysis, which indicated that constituents of AWGC still remained on the surface. On the other hand, the results of elementary analyses in the Si rich regions varied among the sections, which probably indicated that the extent of degradation and absorption of AWGC varied among the sections. AWGC was one of the bioactive ceramics and reported to have an ability to bond to bone earlier than hydroxyapatite (HA). In the present case, though massive osteolysis occurred with aggressive wear, it did not expand on the porous surface, and rather progressed along the smooth surface of the screws. Considering that there are many clinical studies reporting poor clinical results of HA-coated smooth cups, bioactive ceramic coating may function well and bring superior clinical results when combined with porous coated substrate. In our study, though the cause of massive polyethylene wear and intrapelvic giant osteolysis could not be revealed, the porous cup with AW-GC bottom coating was well fixed and gained bone-ingrowth at the porous surface under osteolytic conditions, which may demonstrate the long-term durability of this surface treatment

There is limited evidence in the literature suggesting that ceramic-on-ceramic (CoC) THA is associated with lower risk of revision for prosthetic joint infection (PJI) than other bearing combinations especially metal-on-polyethylene (MoP) and metal-on-metal (MoM). Pitto and Sedel reported hazard ratios of 1.3 – 2.1 for other bearing surfaces vs. CoC. Of interest, the PJI rate was not significantly lower in the first 6 months, when most infections occur, but only became significant in the long term. While factors such as patient age, fixation, mode, O.R. type, use of body exhaust suits, and surgeon volume were considered in the multivariate analysis, BMI, medical comorbidities, and ASA class were not. This is a major weakness that casts doubt on the conclusion, since those three factors are MAJOR risk factors for PJI AND all three factors are more likely to be unevenly distributed, much more likely present in groups other than CoC. The data was also limited by the fact that it was drawn from a retrospective review of National Registry data, The New Zealand Joint Registry. While similar findings have recently been reported from the Australian Joint Registry, the danger in attributing differences in outcomes to implants alone is possibly the single greatest danger in interpreting registry results. While device design can impact implant survival, other factors such as surgical technique, surgeon, hospital, and especially patient factors have a far greater likelihood of explaining differences in observed results. A recent report from the same New Zealand joint registry reported that obesity, ASA class, surgical approach, and trainee operations all were associated with higher PJI and all would be more likely in non-CoC THAs. Accuracy of diagnosis is also a major concern. Revision for trunnionosis is more common in non-CoC THA and is frequently misdiagnosed as PJI.

Numerous non-registry studies and reviews have compared PJI in CoC vs. other bearing and none have concluded than the incidence of PJI differed significantly.

Ceramic bearings are currently the most widely used alternative to metal-on-polyethylene bearings in total hip arthroplasty (THA). A workgroup at International Consensus Meeting (ICM) analyzed the potential link between the type of bearing surface and the subsequent periprosthetic joint infection (PJI), and found a higher incidence of PJI when using a metal-on-metal (MoM) bearing surface. A potential reason is that the failure of a MoM bearing surface can result in adverse local tissue reactions (ALTR), which might provide a favorable environment for bacterial proliferation.

In the last few years, several observational studies including national registries, showed that metal-on-polyethylene (MoP) bearing surfaces are associated with a higher rate of infection following total hip arthroplasty (THA) compared to ceramic bearings, in particular with the use of ceramic-on-ceramic bearing (CoC) surfaces.

After adjusting for selection bias and various confounding factors, patients treated with ceramic bearings experienced reduced risk of infection and MoP bearing surface is an independent risk factor correlating with higher incidence of PJI. The meta-analysis by Lee et al. comparing MoM with CoC cementless THA confirmed that the MoM is associated with a significantly higher revision rate than CoC group for any reason as well as for PJI. Furthermore, initial in-vitro studies have shown lower bacterial biofilm formation on ceramic bearing surfaces. Summarizing the current literature, ceramic bearings are associated with a lower risk of infection following THA.

Periprosthetic joint infection (PJI) is a devastating complication of total hip arthroplasty (THA). According to registry-based studies, some bearing couples are associated with an increased risk of PJI. The recent International Consensus on Periprosthetic Joint Infection stated that metal-on-metal (MOM) bearing surface appeared to be associated with a higher incidence of PJI. Based on emerging reports, the incidence of PJI appears to be different among different bearing surfaces. We conducted a multi-institutional study attempting to study this exact issue. The purpose of the study was to determine whether there was any difference in the incidence of PJI in two commonly used bearing couples (metal- on-polyethylene versus ceramic-on-polyethylene).

Based on a retrospective multi-institutional query all patients who received primary THA with MOP or COP bearing surfaces performed during 2005–2009 in two high-volume arthroplasty centers were identified. Demographic factors, comorbidities, length of hospital stay, complications and other relevant information were extracted. PJI was defined based on the MSIS (International Consensus) criteria. Multivariate analysis was performed to determine whether bearing coupling was independently correlated with PJI.

In our data, 25/2,921 (0.9%) patients with MOP and 11/2,643 (0.4%) patients with COP developed PJI. This difference was statistically significant (p=0.01). After the multivariate analysis, controlling for potential confounders (age, body mass index and length of hospital stay, Charlson comorbidity index), MOP bearing surface was found to be an independent factor correlating with higher incidence of PJI (odds ratio: 2.6, 95% confidence interval: 1.02–6.54, p=0.04).

The finding of this study, and others from centers in Europe, suggest that the bearing surface may have an influence on the incidence of PJI. Although, we had originally thought that ceramic bearing surfaces may be used in younger and healthier patients, the multivariate analyses that controlled for all these variables confirms that use of metal femoral head is an independent risk factor for development of PJI. The finding of this study is compelling and begs for future basic science mechanistic investigations.

There is limited evidence in the literature suggesting that ceramic-on-ceramic (CoC) THA is associated with lower risk of revision for prosthetic joint infection (PJI) than other bearing combinations especially metal-on-poly (MoP) and metal-on-metal (MoM). Pitto and Sedel reported hazard ratios of 1.3 – 2.1 for other bearing surfaces versus CoC. Of interest, the PJI rate was not significantly lower in the first 6 months, when most infections occur, but only became significant in the long term. While factors such as patient age, fixation, mode, OR type, use of body exhaust suits, and surgeon volume were considered in the multivariate analysis, BMI, medical comorbidities, and ASA class were not. This is a major weakness that casts doubt on the conclusion, since those three factors are MAJOR risk factors for PJI AND all three factors are more likely to be unevenly distributed, and much more likely present in groups other than CoC. The data was also limited by the fact that it was drawn from a retrospective review of National Registry data, The New Zealand Joint Registry. While similar findings have recently been reported from the Australian Joint Registry, the danger in attributing differences in outcomes to implants alone is possibly the single greatest danger in interpreting registry results. While device design can impact implant survival, other factors such as surgical technique, surgeon, hospital, and especially patient factors have a far greater likelihood of explaining differences in observed results. A recent report from the same New Zealand joint registry reported that obesity, ASA class, surgical approach, and trainee operations all were associated with higher PJI and all would be more likely in non-CoC THAs. Accuracy of diagnosis is also a major concern. Revision for trunnionosis is more common in non-CoC THA and is frequently misdiagnosed as PJI.

Numerous non-registry studies and reviews have compared PJI in CoC vs. other bearings and none have concluded than the incidence of PJI differed significantly.

Introduction:

Failure of the polyethylene glenoid component is the most common complication of Total Shoulder Arthroplasty (TSA) and accounts for a majority of the unsatisfactory results after this procedure. Nowadays, most of the shoulder prostheses consist of metal on polyethylene bearing components. Repetitive contact between the metal ball and the polyethylene socket produces progressive abrasion of the implant if the moving part is made of polyethylene. Its debris may then lead to an active osteolysis and implant loosening. Failure of the glenoid component is often manifested clinically by pain, loss of function, and the presence of a clunking noise and leads to revision surgery.

The use of ceramic balls aims at the reduction of this phenomenon. In many studies regarding knee and hip replacement it has been shown that the use of ceramic on polyethylene is more beneficial in terms of polyethylene wear and failure, when compared to metal on polyethylene. This is to our knowledge the first study to address in direct comparison wear in both TSA and RTSA.

Introduction

Failure of the polyethylene glenoid component is the most common complication of Total Shoulder Arthroplasty (TSA) and accounts for a majority of the unsatisfactory results after this procedure. Nowadays, most of the shoulder prostheses consist of metal on polyethylene bearing components. Repetitive contact between the metal ball and the polyethylene socket produces progressive abrasion of the implant if the moving part is made of polyethylene. Its debris may then lead to an active osteolysis and implant loosening. Failure of the glenoid component is often manifested clinically by pain, loss of function, and the presence of a clunking noise and leads to revision surgery.

The use of ceramic balls aims at the reduction of this phenomenon. In many studies regarding knee and hip replacement it has been shown that the use of ceramic on polyethylene (CoP) is more beneficial in terms of polyethylene wear and failure, when compared to metal on polyethylene (MoP).

Since a human shoulder is very different from a hip and a knee, it is not a self-centering, neither congruent joint. And its stability is provided by healthy muscles of the rotator cuff. We decided to compare CoP against MoP in semi- force controlled test setup. Where, for a given governing angular motion the translational motion was a function of contact (frictional) forces between the tested couple (humeral head and PE).

This is to our knowledge the first study to address in direct comparison wear in TSA in semi force controlled test setup.

The use of hard-on-hard bearings, including ceramics peaked in the mid 2000's and has seen rapid decline since that time. Ceramics are not new to the market place but have had a 40 year history outside the U.S. The basis for renewed enthusiasm for ceramics included improved manufacturing, improved taper tolerances, higher strength, and lower wear. In spite of the major improvements concerns have been expressed with new generation ceramics by the experts and thought leaders in the field. The major concerns included complications related to modularity, continued problems with fracture and consequences of fracture, limited surgical options, and squeaking and impingement. The conclusion of one review article was that “although ceramics show promise as a lower wear articulation, manufacturing and design modifications and improvements will continue in an attempt to address the substantial concerns that persist”. Modifications have indeed occurred. The question is rather all of these concerns have been addressed and the answer is no. One proposed solution was a hybrid material of Alumina and Zirconia (Delta Ceramic). The advantages included higher strength, lower wear, more options and possibly less squeaking. Unfortunately the modest material improvements did not begin to overcome the obstacles to adopting this technology. High on this list is the problem with cost with the current health care environment unwilling to pay for expensive new technology that does not have proven value. A 2nd major issue is new technology must account for variability in surgeon performance in maximising margin for error. The medical legal environment is unforgiving of failure of new unproven options. Most of the old issues with ceramics have not been completely resolved. Delta Ceramic in particular, has increased cost with no demonstrated benefit. A major problem is there is no known problem with metal or ceramic against cross-linked polyethylene bearing in terms of wear or osteolysis in the 10–15 year time frame. Among all the bearing articulations, metal-on-cross-linked performs the best. The persistent vexing problems with ceramics include impingement, liner breakage, and squeaking. Ceramic components do not tolerate component malposition which increases wear and squeaking. The problem is that a substantial percentage of hip replacements are put in outside of the ideal radiographic zone even at specialty centers. Breakage continues to be a problem especially with liners. There is also a need for complete rim exposure for concentric placement with impaction of liners which makes ceramics less compatible with small incision surgery. The problem of squeaking has not been solved by Delta Ceramic. Originally a case report appeared in the literature of squeaking with Delta Ceramic. Since that time a large scale study has showed that only 69% of Delta Ceramic hips were silent with up to 13% being associated with reproducible squeaking. While a new generation of ceramics are better than the earlier generation and have lowered the fracture risk and increased intraoperative options, the current generation ceramics still provide far fewer options than a standard metal-on-cross-linked total hip. The current generation metal-on-cross-linked total hips have 10–15 year results that cannot be improved upon in terms of wear and osteolysis. Other unsolved problems include breaking, chipping and squeaking. Ceramic-on-ceramic is less tolerant of suboptimal position which leads to impingement, edge loading, and an increased incidence of squeaking. Until all of these problems are successfully addressed, ceramic-on-ceramic cannot be advocated for widespread use

Introduction. The longevity of highly cross-linked polyethylene (XLPE) bearings is primarily determined by its resistance to long-term oxidative degradation. Addition of vitamin E to XLPE is designed to extend in vivo life, although it has unintended consequences of inducing higher frictional torque and increased wear when articulating against metallic femoral heads. 1–3. Conversely, lower friction was observed when oxide ceramic heads were utilized. 3. Previous studies suggest that oxide ceramics may contribute to XLPE oxidation, whereas a non-oxide ceramic, silicon nitride (Si. 3. N. 4. ), might limit XLPE's degradation. 4. To corroborate this observation, an accelerated hydrothermal ageing experiment was conducted using static hydrothermal contact between XLPE and commercially-available ceramic femoral heads. Materials and Methods. Two sets of four types of ceramic femoral heads, consisting of three oxides (Al. 2. O. 3. BIOLOX. ®. forte, and ZTA BIOLOX. ®. delta, CeramTec, GmbH, Plochingen, Germany; and m-ZrO. 2. OXINIUM. TM. , Smith & Nephew, Memphis, TN, USA) and one non-oxide (MC. 2®. Si. 3. N. 4. , Amedica Corp., Salt Lake City, UT, USA) were cut into hemispherical sections. Six highly crosslinked polyethylene liners (X3. TM. Stryker Orthopedics, Inc., Mahwah, New Jersey, USA) were also sectioned, gamma irradiated (32 kGy), and mechanically clamped (25 kN) to the convex surfaces of the ceramic heads (Figure 1(a)). All surfaces were dipped in water and placed into an autoclave at 121°C under adiabatic conditions for 24 hr. The test was repeated three times using two couples for each material along with XLPE-on-XLPE controls. Each XLPE sample was characterized before and after ageing using Raman spectroscopy for variations in their crystalline phase and oxidation indices using the intensities of unpolarized vibrational bands at 1296, 1305, and 1418 cm. −1. Significance (p<0.05) was determined using Student's t-test with a sample size of n=18. Results. Results are provided in Figure 1(b) for changes in crystallinity. Detectable crystallinity values were significantly lower for XLPE/XLPE (5.47%) and XLPE/Si. 3. N. 4. (6.74%) pairs when compared with average increases of 9.37, 9.43, and 10.52% for XLPE/ZTA, XLPE/Al. 2. O. 3. , and XLPE/m-ZrO. 2. , respectively. Discussion. It is evident that crystallinity and oxidation changes occur in XLPE even under simple static hydrothermal test conditions. As expected, the XLPE control couple showed the lowest overall change because oxygen molecules could similarly diffuse and react with either of the identical counterparts. However, the oxide ceramics were not as effective as Si. 3. N. 4. in preventing dissolved oxygen from reaching the polyethylene surface. Conclusion. Coupling oxide ceramics to XLPE in a simple static hydrothermal test increased XLPE's crystallinity and oxidation, while the converse was apparent for Si. 3. N. 4. These experiments revealed differing roles for oxide and non-oxide ceramics in either promoting or preventing XLPE degradation, respectively. They offer a new paradigm of an “integrated joint space” where biomaterial surfaces affect each other's properties as well as their in vivo tribological behavior

INTRODUCTION. Unlike current acetabular cups, this novel ceramic cup has a Ti/HA coating which removes the requirement for assembly into a metal shell which avoiding potential chipping/misalignment and reducing wall thickness [Figure 1]. This study examines the resistance of novel thin-walled, direct to bone fixation ceramic cups to critical impact loads. METHODS. Samples of the smallest (Ø46mm) and largest (Ø70mm) diameter ReCerf. TM. acetabular cups and corresponding femoral head implants were implanted into Sawbones foam blocks considered representative of pelvic cancellous bone. Two different positional configurations were tested and were considered worst case and the extremes of surgical compromise; P1 simulates the cup fully supported by the acetabulum with a high inclination angle (70°) and a vertical impaction axis (worst case loading near the cup rim) and. P2 simulates the cup implanted with a lower inclination (55°) but with the superior section unsupported by acetabulum bone [Figure 2]. For each size, three acetabular cups were tested in each position. The impact fixture was positioned within a drop weight rig above a bed of sand and ≈22mm of pork belly representative of soft tissues damping effect and the implant components aligned to achieve the defined impact point on the cup [Figure 2]. Lateral falls were tested on all available samples applying impact energy of 140J [1] and 3m/s impact velocity [2]. After the lateral fall test, each sample was tested under impact conditions equivalent to a frontal car crash considering a peak impact force of 5.7kN occurring 40ms from initial contact (able to produce acetabular fracture)[3]. RESULTS. None of the testing simulating a lateral fall produced fracture or any other damage to the ceramic acetabular cup. In 7 of the 12 tests, the impact force was sufficient to fracture the foam block representing the periprosthetic bone. The cups showed a good stability within the blocks, with a maximum recorded cup spinning angle relative to the acetabulum of 4.5˚. Subsequent testing simulating a car crash resulted in the fracture of two samples out of 12, one of the largest and one of the smallest ReCerf. TM. cups. In both instances, failure occurred very close to the inner edge. Of the remaining 10 samples no cup fractures were observed. All foam acetabulum blocks were severely damaged and 5 blocks fractured. The maximum recorded cup spinning angle following the car crash impact was 5.8˚. SIGNIFICANCE. Extreme testing scenarios presented here are not a regulatory requirement for manufacturers and have not previously been considered for ceramic acetabular components. Fracture is a possible failure mode of ceramics but this testing has proven that modern ceramics can withstand lateral falls and the large majority can withstand subsequent loading equivalent to head on car-crash; loading under which pelvic bone fracture and significant injury is far more likely to occur than implant fracture

The leading cause for total hip arthroplasty (THA) revision remains aseptic loosening due to bearing wear. The younger and more active patients currently undergoing arthroplasty present unprecedented demands on THA-bearings. Ceramic-on-ceramic (CoC) bearings have consistently shown the lowest wear rates. The recent advances, especially in alumina CoC bearings, have solved many past problems and produced preferable results in vitro. Alumina ceramics are extremely hard, scratch resistant, biocompatible, offer a low coefficient of friction, superior lubrication and lower wear rates in comparison to other bearings in THA. The major disadvantage of ceramics used to be fracture. The new generation of alumina ceramics, has reduced the risk of ball fracture to 0.03–0.05%. The risk for liner fracture is even lower. Assuming an impingement-free component implantation, CoC bearings have major advantages over other bearing combinations. Due to the superior hardness, CoC bearings produce less third body wear and are virtually impervious to damage from instruments during the implantation process. A complication specific to CoC bearings is squeaking. Squeaking occurs if the friction in the joint articulation is sufficient to excite vibrations to audible magnitudes (due to loss of lubrication). The high range of reported squeaking (0.45% to 10.7%) highlights the importance of correct implant position. If a correct implant position can be guaranteed, then squeaking is rare and without clinical significance. The improved tribology and presumable resulting implant longevity make CoC the bearing of choice for young and active patients. Especially the alumina matrix (Biolox delta) offers increased burst strength and greater fracture toughness

While total hip arthroplasty (THA) has been shown successful at relieving pain and improving function in patients with coxarthrosis, wear and instability remain leading causes for revision surgery. Highly crosslinked polyethylene (HXPE) has significantly reduced wear and osteolysis but volumetric wear associated with the use of larger diameter ball heads may be an issue in the long-term. Finally, concerns with femoral taper corrosion have increased the utilization of ceramic ball heads in recent years. Ceramic on ceramic articulations are optimised for both minimizing implant wear and instability. It is biocompatible, wettable, and possesses the lowest in vitro and in vivo wear rates among all bearing couples. In fact, wear rates are lowest when the ceramic ball head size is maximised. Additionally, modern ceramic on ceramic THA designs have had an excellent clinical track record with low rates of loosening, failure, and no reports of osteolysis in even highly active, young patients. Concerns with ceramics center around issues related to fracture risk, squeaking, and cost. While the phenomenon of squeaking remains poorly understood, the reliability of ceramic implants have steadily improved with better materials, design, and manufacturing. The fracture risk for modern pure alumina implants and the newer alumina matrix composite ceramics are 1 in 5000 and 1 in 100,000, respectively. The advantages of ceramic on ceramic THAs will not be realised on every patient and therefore, should be selectively used. However, with expected increases in life expectancy and more young, active patients undergoing THA, ceramic on ceramic THA should be strongly considered in patients under age 60 years

Introduction. Are there really ‘conventional’ bearings, offering more security and less risk than the ‘alternative’ bearings that feature in the programme?. Alternative, when used as an adjective has 2 meanings:. offering or expressing a choice, as in several alternative plans. different from or functioning outside the usual or conventional:. eg alternative newspaper, alternative rock music, alternative medicine. This paper reviews the elements that make up the bearing couples available today in the developed world, and tests each bearing against these meanings. Materials. what are the alternatives?. The materials available today fall into the following broad families:. Metals. Stainless Steel and Cobalt-Chromium Alloy, are the dominant metals available. There is no variation in the Steel, but the characterisation of the Co-Cr does vary. Several manufacturers use different carbide content for the femoral and acetabular components, and different processes. One has been withdrawn from the market, and others may be at risk of this, although it is not the material itself that seems to be the main issue. Ceramics include alumina and zirconia ceramics. Alumina has been available unchanged for over 40 years, although delta ceramic (a zirconia toughened alumina) has only been available unchanged since 2001, making in available for 10 years. Polymers. a huge range of polyethylenes are now available, with different individual claims. All claim superior wear resistance, and oxidation resistance. More than 20 unique products are available in the EU, each with a proprietary formula giving individual characteristics. Coatings and surface treatments. these are now available today from many companies, who either ceramicise the surface of cobalt chrome or titanium with titanium nitride, or use oxinium (a proprietary product from a single company). Bearing couples. what are the alternatives Symmetric and Asymmetric bearings are currently offered. Symmetric bearings are available for Ceramic on Ceramic and Metal on Metal bearings only. Asymmetric bearings are available with metals, including metal on poly, and metal on peek. Ceramics can couple with metal or polymers. Bearing Sizes. Larger than 32mm should be considered ‘alternative’. The larger metal bearings have seen the start of crevice corrosion at the taper between titanium and Co-Cr, and even between different Co-Cr alloys. This new class of complication seems to be unique to metal femoral heads. Bearing-stem compatibility. Larger metal on metal head bearings have brought an entirely new world of complications. The choices of trunion are mainly twofold: the 12/14 tapers which differ significantly between products, and the V40 taper still used by one manufacturer. Neither was designed for use with a larger diameter head. Conclusions. The use of the word ‘alternative’ implies a ‘standard’ or conventional bearing. Ceramic bearings have changed least, have been immune from the metallosis and crevice corrosion seen with large ball Metal head whether bearing on metal or polyethylene. They also have reassuring long term results. In 2011 they should be considered the standard bearing for the young and active patient. The large diameter metal on highly cross-linked poly bearings should now be considered ‘alternative’