Metals represent the main components of orthopaedic implants. Being in contact with biological fluids, the metallic alloys used for the fabrication of artificial joints undergo corrosion or degradation, therefore they release ions and molecules. Although these do not have antigenic properties, they bind to protein carriers and may act as haptens eliciting a delayed-type hypersensitivity reaction (DTH). Biomaterial-related hypersensitivity is considered as an immunotoxic effect, although little is known about its clinical incidence and its impact on implant failure. The main question about the sensitivity against metals used in the joint prosthesis concern the cause-effect relation with the implant failure. In metal-exposed workers, the diagnosis of DTH is made in vivo by patch testing. For the occupational exposure standard patch-testing protocols are available, but some concerns exist about their applicability to study the hypersensitivity to metal implants. In this case-control study, a panel of representative haptens was used to assess the incidence of positive patch testing in patients undergoing ‘total hip replacement’ (THR) and ‘total knee replacement’ (TKR). The main goal of this study was to evaluate the validity of this relatively simple and safe procedure in the diagnosis of the hypersensitivity reactions to the implant components. A consecutive series of 286 individuals was enrolled in the study. Five groups of patients were evaluated: Group A included 75 patients (20 M; 55 F; median age 59) candidates to primary THR or TKR; Group B included 98 patients with loosening of THR (27 M; 71 F; median age 67; median follow up: 102 months); Group C included 53 patients with stable THR (13 M; 40 F; median age 68; median follow up: 60 months); Group D included 40 patients with failed TKR (14 M; 26 F; median age 68; median follow up: 24 months); Group E included 20 patients with stable TKR (4 M; 16 F; median age 70; median follow up: 16 months). Osteoarthritis was the most frequent disease that led to joint replacement (59%), followed by hip dysplasia (19%), and trauma (13%). Patients with rheumatoid arthritis were excluded from the study, as well as patients who assumed cortico-steroids or other immunosuppressive drugs. Fifty-eight patients (21%) had an additional implant at another site. Hypersensitivity to metals was tested by using the most relevant components of Cobalt-Chromium based alloys (CoCrMo), Ti-based alloys (TiAlV), and bone cements. A drop of each hapten was smeared on the Haye’s chamber test, which was applied to the dorsum of the patient. After 48–72 hours, skin reactions were evaluated and graded as 0 (no reaction), 1 (erythema), 2 (edema), 3 (vesicles), or 4 (bulla). All patients with a medical history of metal DTH showed positive skin reaction. The incidence of positive patch testing to at least one hapten, as well as the frequency of DTH to metal, resulted significantly higher in patients with TKR, while the incidence of positive skin testing to bone cements was similar in all groups. Group B patients with CoCrMo-THR showed a low frequency of nickel-DTH in comparison to Group A (9% and 22%, respectively). In patients with TiAlV-THR the immune status seemed to be unaffected, and these individuals showed a high incidence of vanadium-DTH (Group A: 8%; Group B: 21%; Group C: 19%; p= 0.04). A high incidence of vanadium hypersensitivity was found also in patients with TKR (Group D: 33%; Group E: 20%). The median duration of the implant resulted significantly lower in patients who had a positive patch testing to metals (71 vs 106 months; p= 0.008). Our results demonstrated the reliability of the panel used for skin testing, which was able to identify a systemic hypersensitivity status. A remarkable finding concerned the prevalence of DTH related to the metal composition of the implant. A significant low frequency of metal DTH, namely nickel, was found in patients with CoCrMo-failed implant. Because nickel is the most common metal sensitizer and its amount in both CoCrMo and TiAlV alloys is very low, we may consider the incidence of nickel DTH as informative for the immune status of the examined group. In the TiAlV group the immune status seems to be unaffected; on the contrary, theese patients showed a high prevalence of vanadium skin reaction. These results confirm the conclusion of previous studies, where the immunocompromised status of patients who had a CoCrMo had been shown and related to the high serum level of chromium and cobalt. Although the cause-effect relation between DTH and implant failure cannot be established, the hypersensitivity should be considered when deciding what type of prosthesis to use. Either if the sensitization precedes or follows the loosening, it participates in the network of events that are responsible for prosthetic loosening, because contributes to mantain the inflammatory process

Introduction. In recent years, there has been a growing interest in bioresorbable metals. Orthopaedic components made from these materials do not require removal by secondary surgery, and offer superior load bearing capability compared to the existing biodegradable polymers. Research on bioresorbable metals have largely focused on alloys based on a subset of the Mg-Zn-Ca ternary system [1, 2], which are pre-existing elements inside the human body. Cytocompatibility assessments of these alloys have reported no signs of inflammation or adverse cellular reactions [2-4]. Rather than designing for longevity, bioresorbable metals rely on their tendency to corrode in a controlled manner. Hence, controlling their corrosion rates is of utmost importance. In the present work, we have explored the effect of compositional variation on the properties of the Mg-Zn-Ca amorphous metals. Subsequent characterisations are performed to assess their suitability as a bioresorbable material. Materials and Methods. A mixture of pure elements and master alloys, namely magnesium, zinc, calcium, and Mg-Ca master alloy, were melted in an induction furnace, followed by injection casting to produce the amorphous metallic samples. Pure magnesium (crystalline) was also used in the subsequent characterisation tests for comparison. The thermophysical properties of the as-cast amorphous metals were characterized using x-ray diffraction (XRD) and differential scanning calorimetry (DSC). The biocorrosion performance was assessed by a combination of immersion, potentiodynamic polarisation (PDP) and hydrogen evolution studies. These tests were conducted in cell media, with a sodium bicarbonate buffer, at 37°C and pH 7.4 in a humidified CO. 2. atmosphere. Results and Discussion. A range of amorphous metal compositions, from Mg-rich to Ca-rich, were successfully produced. XRD confirmed that the alloys were amorphous. Subsequent characterisation tests revealed that minor alterations in composition were not detrimental to thermophysical properties; however, the critical casting size and corrosion rates were much more sensitive to alloy chemistry. In comparison, the Mg-rich alloys have superior corrosion resistance, whereas the Ca-rich alloys have improved thermophysical properties, thereby allowing them to undertake more complex thermoplastic forming processes. Conclusion. We have successfully produced amorphous metals with a range of corrosion resistance and thermophysical properties. The combination of biocompatible elements, superior corrosion resistance and reduced hydrogen evolution, make these amorphous metals more suitable for use as bioresorbable orthopaedic components than their crystalline counterparts. Acknowledgements. The authors would like to thank the Australian Research Council (ARC) for partial funding of this work via the ARC Centre of Excellence for Design in Light Metals (CE0561574)

Prosthetic joint infections represent complications connected to the implantation of biomedical devices. Bacterial biofilm is one of the main issues causing infections from contaminated orthopaedic prostheses. Biofilm is a structured community of microbial cells that are firmly attached to a surface and have unique metabolic and physiological attributes that induce improved resistance to environmental stresses including toxic compounds like antimicrobial molecules (e.g. antibiotics). Therefore, there is increasing need to develop methods/treatments exerting antibacterial activities not only against planktonic (suspended) cells but also against adherent cells of pathogenic microorganisms forming biofilms. In this context, metal-based coatings with antibacterial activities have been widely investigated and used in the clinical practice. However, traditional coatings exhibit some drawbacks related to the insufficient adhesion to the substrate, scarce uniformity and scarce control over the toxic metal release reducing the biofilm formation prevention efficacy. Additionally, standardized and systematic approaches to test antibacterial activity of newly developed coatings are still missing, while standard microbiological tests (e.g. soft-agar assays) are typically used that are limited in terms of simultaneous conditions that can be tested, potentially leading to scarce reproducibility and reliability of the results.

In this work, we combined the Calgary Biofilm Device (CBD) as a device for high-throughput screening, together with a novel plasma-assisted technique named Ionized Jet Deposition (IJD), to generate and test new generation of nanostructured silver- and zinc-based films as coatings for biomedical devices with antibacterial and antibiofilm properties. During the experiments we tested both planktonic and biofilm growth of four bacterial strains, two gram-positive and two gram-negative bacterial strains, i.e. Staphylococcus aureus ATCC 6538P, Enterococcus faecalis DP1122 and Escherichia coli ATCC 8739 and Pseudomonas aeruginosa PAO1, respectively. The use of CBD that had the only wells covered with the metal coatings while the biofilm supports (pegs) were not sheltered allowed to selectively define the toxic effect of the metal release (from the coating) against biofilm development in addition to the toxic activity exerted by contact killing mechanism (on biofilms formed on the coating). The results indicated that the antibacterial and antibiofilm effects of the metal coatings was at least partly gram staining dependent. Indeed, Gram negative bacterial strains showed high sensitivity toward silver in both planktonic growth and biofilm formation, whereas zinc coatings provided a significant inhibitory activity against Gram positive bacterial strains. Furthermore, the coatings showed the maximal activity against biofilms directly forming on them, although, Zn coating showed a strong effect against biofilms of gram-positive bacteria also formed on uncoated pegs.

We conclude that the metal-based coatings newly developed and screened in this work are efficient against bacterial growth and adherence opening possible future applications for orthopedic protheses manufacturing.

Both total joint arthroplasty (TJA) and Alzheimer's Disease (AD) are prevalent in elderly populations. It is the goal of this study to determine if the presence of implant metals originating from TJA correlates with the onset with higher implant metal content in the brain and AD pathology.

Tissue samples from four brain regions of 701 (229 with TJA) participants from an ongoing longitudinal cohort study (Rush Memory and Aging Project) was analyzed including the inferior-temporal-cortex (ITC), which is associated with early onset of AD. Implant metal (Co, Cr, Mo, Ti, Al) content was determined by ICP-MS. Comparisons were conducted between the no-TJA-group and a TJA group. Due to the higher likelihood of Co release the TJA group was further differentiated in a THA (N=146) and a TKA/TSA (N=83) group. Diffuse and neuritic amyloid plaques and phosphorylated tau were assessed and summarized as standard measures of AD pathology. We used separate linear regression models adjusted for age, sex, education, and APOɛ4-status for the associations of all metals (log-transformed) with global AD pathology, amyloid plaques, and phosphorylated tau.

The THA group had higher cobalt content across all brain regions (p=0.003) and within the ITC (p=0.051) compared to the no-TJA group, whereas the TKA/TSA group did not. Across all tissue samples, Co was associated with higher amyloid load (β=0.35, p=0.027), phosphorylated tau (β=0.47, p=0.011), and global AD pathology (β=0.19, 0.0004) in the ITC. The presence of TJA itself was not associated with AD pathology.

We showed that only Co content was higher within the ITC in persons with THA. We found among all tested metals that Co was consistently associated with AD pathology. Although we found an association of cobalt with AD pathology, the cross-sectional nature of this study does not allow the determination of cause and effect.

Prosthetic joint infections represent complications connected to the implantation of biomedical devices, they have high incidence, interfere with osseointegration, and lead to a high societal burden. The microbial biofilm, which is a complex structure of microbial cells firmly attached to a surface, is one of the main issues causing infections. Biofilm- forming bacteria are acquiring more and more resistances to common clinical treatments due to the abuse of antibiotics administration. Therefore, there is increasing need to develop alternative methods exerting antibacterial activities against multidrug-resistant biofilm-forming bacteria. In this context, metal-based coatings with antimicrobial activities have been investigated and are currently used in the clinical practice. However, traditional coatings exhibit some drawbacks related to the insufficient adhesion to the substrate, scarce uniformity and scarce control over the toxic metal release reducing their efficacy. Here, we propose the use of antimicrobial silver-based nanostructured thin films to discourage bacterial infections. Coatings are obtained by Ionized Jet Deposition, a plasma-assisted technique that permits to manufacture films of submicrometric thickness having a nanostructured surface texture, allow tuning silver release, and avoid delamination. To mitigate interference with osseointegration, here silver composites with bone apatite and hydroxyapatite were explored. The antibacterial efficacy of silver films was tested in vitro against gram- positive and gram-negative species to determine the optimal coatings characteristics by assessing reduction of bacterial viability, adhesion to substrate, and biofilm formation. Efficacy was tested in an in vivo rabbit model, using a multidrug-resistant strain of Staphylococcus aureus showing significant reduction of the bacterial load on the silver prosthesis both when coated with the metal only (>99% reduction) and when in combination with bone apatite (>86% reduction). These studies indicate that IJD films are highly tunable and can be a promising route to overcome the main challenges in orthopedic prostheses.

Prosthetic joint infections represent complications connected to the implantation of biomedical devices, they have high incidence, interfere with osseointegration, and lead to a high societal burden. The microbial biofilm, which is a complex structure of microbial cells firmly attached to a surface, is one of the main issues causing infections. Biofilm- forming bacteria are acquiring more and more resistances to common clinical treatments due to the abuse of antibiotics administration. Therefore, there is increasing need to develop alternative methods exerting antibacterial activities against multidrug-resistant biofilm-forming bacteria. In this context, metal-based coatings with antimicrobial activities have been investigated and are currently used in the clinical practice. However, traditional coatings exhibit some drawbacks related to the insufficient adhesion to the substrate, scarce uniformity and scarce control over the toxic metal release reducing their efficacy. Here, we propose the use of antimicrobial silver-based nanostructured thin films to discourage bacterial infections. Coatings are obtained by Ionized Jet Deposition, a plasma-assisted technique that permits to manufacture films of submicrometric thickness having a nanostructured surface texture, allow tuning silver release, and avoid delamination. To mitigate interference with osseointegration, here silver composites with bone apatite and hydroxyapatite were explored. The antibacterial efficacy of silver films was tested in vitro against gram- positive and gram-negative species to determine the optimal coatings characteristics by assessing reduction of bacterial viability, adhesion to substrate, and biofilm formation. Efficacy was tested in an in vivo rabbit model, using a multidrug-resistant strain of Staphylococcus aureus showing significant reduction of the bacterial load on the silver prosthesis both when coated with the metal only (>99% reduction) and when in combination with bone apatite (>86% reduction). These studies indicate that IJD films are highly tunable and can be a promising route to overcome the main challenges in orthopedic prostheses.

Aims

Metal allergy in knee arthroplasty patients is a controversial topic. We aimed to conduct a scoping review to clarify the management of metal allergy in primary and revision total knee arthroplasty (TKA).

Over the last 50 years, biomaterials, prostheses and implants saved and prolonged the life of millions of humans around the globe. The main clinical complications for current biomaterials and artificial organs still reside in an interfacial mismatch between the synthetic surface and the natural living tissue surrounding it. Today, nanotechnology, nanomaterials and surface modifications provides a new insight to the current problem of biomaterial complications, and even allows us to envisage strategies for the organ shortage. Advanced tools and new paths towards the development of functional solutions for cardiovascular clinical applications are now available. In this talk, the potential of nanostructured metallic degradable metals to provide innovative solutions at medium term for the cardiovascular field will be depicted. Focus will be on Fe-based biodegradable metals with exceptional resistance, ductility and elasticity, for pushing innovative vascular applications. The intrinsic goal of this talk is to present an extremely personal look at how biodegradable metals can impact materials, surfaces and interfaces, and how the resulting unique properties allowed biomedical functional applications to progress, from their introduction, to the promising future that biodegradable metals may or may not hold for improving the quality of the life of millions worldwide.

Since 2010, there has been a sharp decline in the use of metal-on-metal joint replacement devices due to adverse responses associated with the release of metal wear particles and ions in patients. Surface engineered coatings offer an innovative solution to this problem by covering metal implant surfaces with biocompatible and wear resistant materials. The present study tests the hypothesis whether surface engineered coatings can reduce the overall biological impact of a device by investigating recently introduced silicon nitride coatings for joint replacements. Biological responses of peripheral blood mononuclear cells (PBMNCs) to Si3N4 model particles, SiNx coating wear particles and CoCr wear particles were evaluated by testing cytotoxicity, inflammatory cytokine release, oxidative stress and genotoxicity.

Clinically relevant wear particles were generated from SiNx-on-SiNx and CoCr-on-CoCr bearing combinations using a multidirectional pin-on-plate tribometer. All particles were heat treated at 180°C for 4 h to destroy endotoxin contamination. Whole peripheral blood was collected from healthy donors (ethics approval BIOSCI 10–108, University of Leeds). The PBMNCs were isolated using Lymphoprep (Stemcell) and incubated with particles at various volumetric concentrations (0.5 to 100 µm3 particles/cell) for 24 h in 5% (v/v) CO2 at 37°C. After incubation, cell viability was measured using the ATPlite assay (Perkin Elmer); TNF-alpha release was measured by ELISA (Invitrogen); oxidative stress was measured using H2DCFDA (Abcam); and DNA damage was measured by comet assay (Tevigen). The results were expressed as mean ± 95% confidence limits and the data was analysed using one-way ANOVA and Tukey-Kramer post-hoc analysis.

No evidence of cytotoxicity, oxidative stress, TNF-alpha release, or DNA damage was observed for the silicon nitride particles at any of the doses. However, CoCr wear particles caused cytotoxicity, oxidative stress, TNF-alpha release and DNA damage in PBMNCs at high doses (50 µm3 particles per cell). This study has demonstrated the in-vitro biocompatibility of SiNx coatings with primary human monocytic cells. Therefore, surface engineered coatings have potential to significantly reduce the biological impact of metal components in future orthopaedic devices.

Major bone loss involving the acetabulum can be seen during revision THA due to component loosening, migration or osteolysis and can also occur as a sequela of infected THA. Uncemented highly porous ingrowth acetabular components can be used for the reconstruction of the vast majority of revision cases, especially where small to mid-sized segmental or cavitary defects are present which do not compromise stable mechanical support by the host bone for the cup after bone preparation is complete. A mechanically stable and near motionless interface between the host bone and the implant is required over the initial weeks post-surgery for bone ingrowth to occur, regardless of the type of porous surface employed. As bone deficiency increases, the challenge of achieving rigid cup fixation also increases, especially if the quality of the remaining host bone is compromised. A stepwise approach to enhanced fixation of the highly porous revision acetabular component is possible as follows:

Maximise Screw Fixation. Use of a limited number of screws in the dome only (as routinely occurs with a cluster hole design) is inadequate, except for primary arthroplasty cases or very routine revision cases with little or no bone loss and good bone quality. Otherwise an array of screws across the acetabular dome and continuing around the posterior column to base of the ischium is strongly recommended. This can help prevent early rocking of the cup into a more vertical position due to pivoting on dome screws used alone, via cup separation inferiorly in zone 3. A minimum of 3 or 4 screws in a wide array are suggested and use of 6 or more screws is not uncommon if bone quality is poor or defects are large.

Cement the Acetabular Liner into the Shell. This creates a locking screw effect, which fixes the screw heads in position and prevents any screws from pivoting or backing out.

Acetabular Augments (vs Structural Allograft). When critical segmental defects are present which by their location or size preclude stable support of the cup used alone, either a structural allograft or highly porous metal augment can provide critical focal support and enhance fixation. Highly porous metal augments were initially developed as a prosthetic allograft substitute in order to avoid the occasional graft resorption and loss of fixation sometimes seen with acetabular allograft use.

Cup-Cage Construct. If one or more of the above strategies are used and fixation is deemed inadequate, it is possible to add a ½ or full acetabular cage “over the top” of the acetabular component before cementing a polyethylene liner in place. The full cup cage construct can be used for maximal fixation in cases of pelvic dissociation, alone or in combination with the distraction method as described by Paprosky. Use of a ½ cage is technically simpler and requires less exposure than a full cage, but still greatly enhances rigidity of fixation when transverse screws into the ilium are combined with standard screws in the cup including vertically into the dome.

These techniques used in combination with highly porous tantalum implants have allowed durable fixation for the full range of reconstructive challenges and bone defects encountered. Newer 3-D printed titanium highly porous materials have recently been introduced by multiple manufacturers as a potential alternative that may be more cost effective, but these implants and materials will require clinical validation over the years ahead.

Highly porous metal surfaces have transformed acetabular revision surgery by providing (1) enhanced friction which potentially provides greater primary fixation, (2) enhanced bone ingrowth potential, (3) enhanced screw fixation options. These characteristics have led many surgeons to use these devices routinely in acetabular revision and have led to an expansion of the indications for porous uncemented hemispherical cups in acetabular revision. Mid-term results suggest that the historical indications for hemispherical cups in revision surgery can be moderately expanded with some implants with these characteristics. In a recent study of 3448 revision total hip arthroplasties, we found porous tantalum cups had a statistically lower revision rate than other materials/designs. Highly porous metals also have provided the options of metal augments to fill selected bone defects—which can both enhance cup fixation and manage bone loss simultaneously. A number of different highly porous metals are now available, and how each will perform is not yet known.

Highly porous metal shells may be used in combination with highly porous metal augments to make up for segmental bone deficiency. Examples will be shown. Finally, highly porous metal shells may be used as a “cup-cage” combination to provide extra initial cup mechanical stability in extreme cases. Examples will be shown.

Replacement of damaged or diseased tissues with permanent metal implants based on stainless steel, cobalt chrome and titanium alloys has been at the forefront of classical biomaterials research and the orthopaedic medical device industry for decades. Biodegradable polymers have also reached the market but often have limited capacity in load bearing orthopaedic applications due to their low stiffness and poor mechanical properties. The development of biodegradable metals based on magnesium (Mg) could be heralded as a major breakthrough in the field of orthopaedic surgery. Degradable implants eliminate the time and cost associated with a secondary surgery to remove hardware, and reduces the period the implant is exposed to instability, fibrous encapsulation, stress shielding and inflammation. The metabolism of Mg and its excretion via the kidneys is a natural physiological process that is well understood, however, controlling the rapid degradation of Mg biomaterials in vivo is a major challenge yet to be resolved for the safe and effective use of Mg in orthopaedic implants.

In this study, we describe a novel manufacturing method for fabricating Mg/Mg alloy implants, as well as the development of an in vitro method for screening Mg/Mg alloy degradation rate by considering both their electrochemical corrosion behaviour and biological characteristics.

A range of Mg alloys with varying amounts of calcium (0.8–28%) and zinc (3–10%) were cast and then machined into Ø4mm and 15mm discs for biocompatibility (HETCAM) and parallel in vitro testing. Alloys were placed in various simulated body fluid (SBF) solutions in vitro (7–28 days) to determine effect of alloy composition on degradation rate. These potentiostatic and potentiodynamic tests were designed to simulate, to varying degrees, the in vivo environment, with the crucial factors (e.g. temperature, pH, serum proteins, CO2 level) controlled to ensure consistency across the test methods. The mechanisms of corrosion on the Mg/Mg alloy microstructure and the effect of protein adsorption all played key roles in dictating the corrosion of alloys in vitro. Specifically the inclusion of physiological levels of serum proteins decreased the corrosion rate up to 600% over more standard SBF solutions described in literature.

This work provides an improved understanding of the effects of corrosion variables on Mg alloys, while making major steps towards deciding the most appropriate screening tests for new alloys for their use as a biomedical material prior to moving to in vivo animal studies.

Wear debris from metal on metal (M/M) hip resurfacing and metal on polyethylene (M/P) total hip replacements have different biocompatibilities. M/P wear particles have a foreign body effect¹. M/M wear particles cause hypersensitivity², DNA damage^3,4 and white blood cell suppression⁵.

M/P wear debris contains nickel and M/M wear debris contains cobalt. Nickel and cobalt are both heavy metals, required as trace elements for some bacteria but potentially toxic to bacteria in high concentrations.

Cobalt kills Helicobacter Pylori at concentrations as low as 30 ppb⁶, substantially lower than the concentration in prosthetic joints. Nickel/cobalt permease membrane transporters are found in a wide range of microorganisms⁷ including Staphylococcus Aureus and Coagulase Negative Staphylococci, which commonly infect prosthetic joints.

The purpose was to investigate the effects of nanoparticulate wear debris and their heavy metal constituents on bacterial growth.

Samples of Coagulase Negative Staphylococci (CNS), Staphylococcus Aureus and MRSA were cultivated to compare their growth in M/M wear debris, M/P wear debris, nickel, cobalt and control culture mediums over 48 hours. Nickel was toxic to CNS (p=0.006) and MRSA (p=0.048). Cobalt also retarded the growth of all three bacteria. M/M wear debris increased the growth of CNS 183 times at 48 hours (p=0.044), Staphylococcus Aureus and MRSA. M/P wear increased the growth of Staphylococcus Aureus 120 times at 48 hours (p=0.021), CNS and MRSA.

M/M and M/P nanoparticulate wear debris accelerate the rate of growth of common organisms that infect prosthetic hip joints, the clinical significance of which is uncertain. In isolation, the heavy metals contained within wear debris retard bacterial growth, particularly nickel.

Nanoparticulate wear debris does not possess the toxic effects of its constituent metals on bacteria. This reinforces the safety of wear debris but also shows the potential for anti-bacterial effects to be harnessed.

Metallic implants are used frequently in the operative repair of joints and fractures in orthopaedic surgery. Orthopaedic implant infection is chronic and biofilm based. Present treatment focuses on removing the infective substratum and implant surgically as well as prolonged anti-microbial therapy. Biofilms are up to 500 times more resistant than planktonic strains of bacterial flora to antibiotics. Silver coatings on polymers and nylon (catheters, heart valve cuffs, burn dressings) have shown inhibition of this biofilm formation in its adhesion stage. Our aim was to deposit effective, minute, antibacterial layers of silver on orthopaedic stainless steel and titanium K-wires and to investigate the effect of these coatings when exposed to Staphylococcus Aureus biofilms in an in vitro and in vivo environment.

Combining magnetron sputtering with a neutral atom beam (Saddle Field) plasma source at 10⁻⁴ mbar in argon gas at temperatures of 60°C, a silver coating of 99.9% purity was deposited onto stainless steel and titanium orthopaedic K-wires. Coating thickness measurements were obtained using glancing angle x-ray diffraction of glass slides coated adjacent to wires. Magnetron parameters were modified to produce varying thickness of silver. Adhesiveness was examined using Rockwell punch tests. Silver leaching experiments were carried out in phosphate buffered saline at 37°C for 48 hours and using inductive coupled plasma spectrometry to assess leached silver ions. Surface microscopy visualised physical changes in the coatings.

Biofilm adhesion was determined by exposing wires to Staphylococcus Aureus ATCC 29213 – NCTC 12973 for 15 minutes to allow biofilm initiation and adhesion. Wires were then culturing for 24 hours at 37°C in RPMI. Subsequently, wires were sonicated at 50Hz in ringer’s solution and gently vortexed to dislodge biofilm. Sonicate was plated out by log dilution method on Columbia blood agar plates. Bacterial colonies were then counted and changes expressed in log factors.

K-wires were coated with 1 to 50 nm of silver by running the magnetron sputtering at low currents. These coatings showed excellent adhesive properties within the 48 hours exposed with only 3.7% of silver leaching in buffered saline. The silver coated stainless steel wires showed a log 2.31 fold reduction in biofilm formation as compared to control wires (p< .001), Student t-test), the silver coated titanium wires showed a log reduction of 2.06, (p< .001, Student t-test). Animal studies demonstrated enormous difficulty in reproducing biofilm formation and showed a 0.49 log fold reduction in the titanium group when exposed to Staph Aureus (p< .01, Student t-test), the other groups showed no statistically significant reduction.

We have perfected a method of depositing tiny layers of anti-bacterial silver onto stainless steel and titanium, which is anti-infective in vitro but not in vivo. Further studies involving other metal coatings such as platinum and copper are warranted.

Patients and methods: We obtained postoperative blood concentrations of Co, Cr, Mo, Ti, Al, Ni and Nb in 75 patients undergoing primary THA at our institution between January 1998 and December 2000. All patients were treated with the same prosthetic device (VARI-ALLTM, Zimmer, Winterthur, Switzerland) using three types of articulations: metal-on-metal (METASULTM), ceramic-on-ceramic (CERASULTM) and metal-on-cross linked polyethylene (DURASULTM). 25 patients out of each articulation-group were evaluated by blood analysis 24–38 months after surgery. The patients were submitted to strict criteria of inclusion.

Results: The Al-, Ti-, Ni- and Nb-blood levels were all below their detection limit. The median Co blood concentration in the ceramic group was 0.19 ng/ml, 0.69 ng/ml in the metal group and 0.19 ng/ml in the cross-linked PE group. The difference between the metal and ceramic group and between the metal and polyethylene group is statistically significant (p=0.001 in both comparisons). The median blood concentration of Cr was 0.19 ng/ml in the ceramic and in the cross-linked PE group, and 0.47 ng/ml in the metal group, the difference being statistically significant (p=0.003 and p=0.0002). Regarding the median blood concentrations of Mo, we found no statistically significant differences comparing the three articulations (p> 0.05). Comparing the three articulation-groups there were no significant differences in the categories age, follow up time and preoperative blood level of creatinine.

Conclusion: Although the blood concentrations of Co and Cr were significantly higher in patients with a metal-on-metal THA they were far from reaching toxic levels. Comparing our results using direct-conical metallic cup inserts with those of total hip devices with metallic sandwich-inlays blood concentrations of Co and Cr appear to be similarly elevated (Lhotka et al, J Orthop Res 2003).

Introduction: Several recent studies have highlighted the influence of topographical features on the response of cells to biomaterial surfaces, both in terms of their adhesion, morphology and gene expression. Initial cell adhesion events are believed to be pivotal in dictating subsequent host response to implant materials and therefore understanding the mechansims that regulate these events is fundemental to the design and engineering of the next generation of biomaterials. In our studies we evaluated the adhesion associated events of osteoblasts on four orthopaedic metals, each produced to the same surface finnish. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to determine the nanometre scale topography and immunofluorescence microscopy and image analysis performed to evaluate cell morphology.

Methods: Vitallium, titanium grade 2 (Ti2), Ti6Al4V and TM2F discs were prepared by Stryker, machined and finished to 1 micron. SEM and AFM were then used to analyse surface topography. Rat primary osteoblasts were then seeded at low density onto the metal discs and allowed to adhere and spread for 24 hours. The cells where fixed and focal adhesions stained with an anti-vinculin Mab. The actin cytoskeleton was counterstained with TRITC phalloidin and nuclei stained with DAPI. Images where captured on both a standard epiflourescence microscope and a confocal microscope. Image analysis was performed using ScionImage^TM to determine cell area, major X/Y axis lengths and numbers of focal adhesions per cell.

Results: Gross observation of all samples revealed a perfectly smooth and flat surface. SEM and AFM analysis showed that at the nanometre scale each exhibited varying degrees of surface roughness. Vitallium was the smoothest with scratches a few nanometres deep running across the surface. In contrast Ti6Al4V, Ti2 and TM2F had increasing degrees of surface roughness, each with details that measured up to a few microns in height.

We measured 1: the area occupied by a cell and 2: the number of focal adhesions per cell. The largest values of osteoblastic cell area were seen with the smoother vitallium surface. In contrast, samples with more numerous and larger surface features resulted in the osteoblasts covering a smaller area and being confined by topographical elements (Ti2> TM2F> Ti6Al4V). In terms of adhesion, there were generally more focal adhesions per cell on rougher surfaces (Ti6Al4V> TM2F> Vitallium> Ti2).

Conclusions: The different nanometre scale features introduced through the manufacturing process of different orthopaedic implant materials influence the adhesion and cell morphology of osteoblast cells within the first 24 hours of contact. This may have consequences for later differentiation and function of these cells.

At present we conduct a clinical study on four bearing combinations in hip arthroplasty. Our main purpose is to assess changes in bone mineral density (BMD), function of the joint, and to monitor serum concentrations of prosthetic metals as well as plasma concentrations of a range of cytokines, chemokines, and related proteins during a ten-year follow-up. This is done in order to evaluate the potential role of these variables as predictors of dysfunction or loosening of the arthroplasty.

A total of 300 patients were randomly allocated to four bearing combinations. Four years after surgery the following number of patients were available for follow-up: Type A: Zirconia ceramic head, polyethylene cup insert in the Universal RingLoc metal backed shell (n=50); Type B: Cobalt-Chrome-Molybdenum head and cup insert in the Universal RingLoc metal backed shell (n=57); Type C: Zirconia ceramic head, polyethylene moulded on the Titanium shell of the Asian cup (n=55); Type D: Alumina head and cup insert in the Universal RingLoc metal backed shell (n=45). A BiMetric Titanium-Aluminium-Vanadium (Ti6Al4V) stem was used with all four combinations (n=207). All patients, but two with rheumatoid arthritis, had primary osteoarthritis or avascular necrosis of the femoral head. Five patients had astma and eight had diabetes.

At the time of surgery the groups were equal with regard to age, gender distribution, body height and weight, side of arthroplasty, and BMD in all seven Gruen zones. Harris Hip Score prior to arthroplasty was equally low in all groups (mean ± SD) (42 ± 17), and increased in all groups, with no significant differences between them (87 ± 10).

At follow-up there was a significant decrease in BMD in all Gruen zones ranging from −1.9 % in zone 4 in group C to −21.7% in zone 7 in group D. However, there were no significant differences between groups.

There were significantly higher blood concentrations of Chromium and Cobalt in group B patients compared to all other groups (p < 0.001).

Plasma concentrations of cytokines IL-1β, IL-6, IL-8, IL-10, TNF-α, TNF-R1, VEGF, OPG, GM-CSF, or TGF-β₁ did not differ significantly between groups. Instead, elevated levels of IL-1β, IL-10 and TNF-R1 were found in patients with asthma. IL-6, TNF-α and VEGF were elevated in patients with rheumatoid arthritis or asthma. IL-8 and TGF-β₁ were higher in patients with osteoarthritis, whereas GM-CSF was high in patients with asthma or diabetes.

CONCLUSION: The elevated serum concentrations of Chromium and Cobalt were seen in the group of patients using a bearing with these metals. It still remains to be elucidated, whether high serum concentrations of bearing surface metals signify a dysfunction of the prosthesis. Concentrations of plasma cytokines are mainly related to patient comorbidity when no sign of prosthetic loosening is present. Changes in BMD adjacent to the cemented femoral stem can not be attributed to any of the bearing materials used in this study.

A major concern in metal on metal bearings has been the elevated serum concentrations of cobalt and chromium. Recent papers have suggested that metal hypersensivity in a few cases could cause periprostetic lymphocyte accumulation leading prosthetic loosening.

To measure the lymphocyte activation and proliferation in vitro by re-exposure of the cells to cobalt, chromium, nickel and titanium. To correlate the lymphocyte assay data to the serum concentration of metals and plasma cytokines.

A prospective clinical study with the ASR (DePuy) and ReCap (Biomet) resurfacing hip implants. Blood samples were collected one and two years postoperatively, lymphocytes were isolated by density gradient centrifugation, cultured in a medium containing the patient’s serum and exposed to metal salts.

Cells were analyzed by flow cytometry, evaluating number, viability, size and CD69 activation.

A negative control and a positive control (phytohaemagglutinine) were included in the assay, and the responses to the metals were calculated in proportion to controls. 11 patients were assessed at one and two years follow up, 16 patients were assessed only at two years.

Serum chromium and cobalt were measured preoperatively, six months, one year and two years postoperatively by graphite furnace absorptiometry. Plasma cytokines were measured by multiplexed immunoassay.

In the assay the negative and positive controls gave the expected responses.

When exposed to metals no response was found in the lymphocytes in any patients.

There were no difference in response between one and two years.

The results seems to indicate that the metal hypersensitivity is a rare condition in metal on metal arthroplasty. The results indicate that the method can be used to monitor hypersensitivity to implant metals.

Background. Mechanisms underlying implant failure remain incompletely described, though the presence of macrophage-mediated inflammatory reactions is well documented. Hypoxia has a critical role in many diseases and is known to be interdependent with inflammation. Metals used for joint replacements have also been reported to provoke hypoxia-like conditions. In view of this, we aim to investigate hypoxia-associated factors in aseptic loosening and osteoarthritis with a focus on macrophages. Methods. Western blotting, calorimetric assay, haematoxylin-eosin staining, immunohistochemistry, double-immunofluorescence and transmission electron microscopy were performed on capsular tissue obtained from patients undergoing primary implantation of a total hip replacement for osteoarthritis and from patients undergoing revision surgery for aseptic loosening to investigate the presence of hypoxia-associated factors. Results. Tissues from patients with osteoarthritis and aseptic loosening showed the presence of inflammatory cells, many of which were macrophages as confirmed with CD68 immunostaining. In aseptic loosening, macrophages containing metal particles were present in clusters. This was observed both at the light and electron microscopic levels. Under the electron microscope, endothelial cells appeared to be hypertrophied and some showed signs of degeneration. The presence of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) and nitric oxide was demonstrated by western blotting and colorimetric assay. Macrophages were the predominant cell type to release HIF-1α, VEGF, inducible nitric oxide synthase (iNOS). This was confirmed by double-immunofluorescence showing co-localization of HIF-1α, VEGF, iNOS with the macrophage marker CD68. Endothelial cells were stained for endothelial nitric oxide synthase as assessed by immunohistochemistry. Conclusion. This study demonstrates the release of hypoxia-associated factors by macrophages. The presence of hypoxia-associated factors in both, osteoarthritis and aseptic loosening suggest that hypoxia may be a factor underlying both pathologic conditions. This study was supported by research grant (NMRC/CNIG/1147/2016) from National Medical Research Council (NMRC), Singapore

Introduction. Metals used for total knee arthroplasty (TKA) are well known for their good biocompatibility, but may be a source of a release of metal ions that can be a cause of local and systemic adverse effects, aseptic loosening, and hypersensitivity reactions. One of the major difficulties in performing TKA is the selection of implants for patients who are preoperatively diagnosed as subject to metal sensitivity. Alternative solutions in cases of hypersensitivity are implants without metal constituents or metallic implants treated with a non-sensitive surface process. The aim of this study was to evaluate clinical results in patients who had been preoperatively diagnosed with metal sensitivity and who subsequently were provided with the zirconia-ceramic LFA-III TKA, and with a minimum 5-year follow-up. Methods. Five patients (8 knees) with metal sensitivity underwent TKA using cemented zirconia-ceramic LFA-III implants. The LFA-III implant (KYOCERA Medical Co., Japan) is composed of a zirconia ceramic femoral component and a titanium-alloy tibial component with a polyethylene insert. All patients were female andthe average age at the time of surgery was 76.1 years. The average follow-up time was 7.2 years. Clinical and radiographic assessments were conducted with the Knee Society scoring system. Results. No patients except one who had palmoplantar pustulosis preoperatively presented systemic or local dermatitis after surgery. The mean preoperative range of motion of 97.6 degrees improved to a mean of 110.7 degrees at the time of the most recent follow-up. The mean postoperative knee and function scores were 77.1 and 66.9, respectively. Subtle periprosthetic radiolucencies were found in 2 knees after the surgery. Discussion. The zirconia-ceramic LFA-III TKA has performed well over a 5-year period in patients with metal hypersensitivity. Although this implant has a metal tibial component made of titanium, no systemic or local adverse events related to metal hypersensitivity were recorded. Ceramic implants can be an attractive alternative solution for patients suffering from hypersensitivity reactions to metals