Summary. The M2a-38. tm. metal on metal total hip arthroplasty showed a high incidence of pseudotumors and an unexpected high revision rate in our thoroughly screened cross sectional cohort. Introduction. After the revival of the metal on metal (MoM) bearing in total hip arthroplasty (THA) at the beginning of this century, there are now serious questions about this type of bearing. The advantage of large head MoM bearing is the increase in range of motion and stability. In our institution the choice was made for 38 mm heads. During the last few years concerns have been raised about the relationship of MoM bearing and elevated serum cobalt and chromium ion levels, their local and systemic toxicological effects and the incidence of local tumorous masses (pseudotumors). Are these findings applicable for all MoM bearings or are there also product specific issues. We present the outcome of a cementless MoM THA using a 38mm head in a unique consecutive series of 377 THA who were performed in our institution. Patients and Methods. All 351 patients (377 THA) with a cementless MoM THA (M2a-38. tm. , Biomet Inc, Warsaw, IN, USA, and Taperloc® stem, Biomet UK, Bridgend) between 2008 and 2011 were evaluated. All patients were analyzed by a physical exam, serum levels of cobalt and chromium and an interview to determine if there were any complaints. An MRI of the hip was made if patients reported pain during physical activity, allergies to metals, serum cobalt or chromium ion levels ≥ 5 ppb or if the inclination of the acetabular component was more than 50 degrees. Nine patients deceased, three were lost to follow up and four already underwent a revision before the screening. We analyzed 361 hips with an average follow up of 30 (range 2–58) months. The average preoperative age was 63 years (41–88). Results. 219 patients with 235 THA (65%) reported no complaints. Median cobalt level in patients with complaints was 6.6 (0.2–173) ppb and in the group without complaints 3.7 (0.2–27.3) ppb. Median chromium level in patients with complaints was 5.0 (0.1–134) ppb and in the group without complaints 3.7 (0.2–27) ppb. On the 226 performed MRI scans, 56 pseudotumors were diagnosed and described using the Anderson classification (9 C1, 41 C2 and 5 C3). 71 hips had been revised after a mean follow of 30 months (range 0.2–50 months). Reasons for revision were because of pain, raised metal ions and a pseudotumor in 28; pain and raised metal ion levels in 15; aseptic loosening of the acetabular or femoral component in 11; raised metal ions and a pseudotumor in 7; combination of luxations, luxation feelings and fractures in 5; infections in 3 and for other reasons in 2. Conclusion. The short-term results of the THA with a 38mm head metal on metal articulation are higher compared with other MoM bearings. They show a revision rate of 7% and 10% in the Australian and England register. In other peer reviewed literature we find a revision rate between 0–13% after five years. We also observed a high incidence of elevated serum levels of metal ions, pseudotumors and an unexpected high early revision rate

The objective of this study was to investigate how a new customizable light-curable osteosynthesis method (AdFix) compared to traditional metal hardware when loaded in torsion in an ovine phalanx model. Twenty-one ovine proximal phalanges were given a 3mm transverse osteotomy and four 1.5mm cortex screws were inserted bicortically on either side of the gap. The light-curable polymer composite was then applied using the method developed by Hutchinson [1] to create osteosyntheses in two groups, having either a narrow (6mm, N=9) or a wide (10mm, N=9) fixation patch. A final group (N=3) was fixated with conventional metal plates. The constructs were loaded in torsion at a rate of 6°/second until failure or 45° of rotation was reached. Torque and angular displacement were measured, torsional stiffness was calculated as the slope of the Torque-Displacement curve, and maximum torque was queried for each specimen. The torsional stiffnesses of the narrow, wide, and metal plate constructs were 39.1 ± 6.2, 54.4 ± 6.3, and 16.2 ± 3.0 Nmm/° respectively. All groups were statistically different from each other (p<0.001). The maximum torques of the narrow, wide, and metal plate constructs were 424 ± 72, 600 ± 120, and 579 ± 20 Nmm respectively. The narrow constructs were statistically different from the other two (p<0.05), while the wide and metal constructs were not statistically different from each other (p=0.76). This work demonstrated that the torsional performance of the novel solution is comparable to metal fixators. As a measure of the functional range, the torsional stiffness in the AdhFix exceeded that of the metal plate. Furthermore, the wide patches were able to sustain a similar maximum toque as the metal plates. These results suggest AdhFix to be a viable, customizable alternative to metal implants for fracture fixation in the hand

Over the last decades, biodegradable metals emerged as promising materials for various biomedical implant applications, aiming to reduce the use of permanent metallic implants and, therefore, to avoid additional surgeries for implant removal. However, among the important issue to be solved is their fast corrosion - too high to match the healing rate of the bone tissue. The most effective way to improve this characteristic is to coat biodegradable metals with substituted calcium phosphates. Tricalcium phosphate (β-TCP) is a resorbable bioceramic widely used as synthetic bone graft. In order to modulate and enhance its biological performance, the substitution of Ca2+ by various metal ions, such as strontium (Sr2+), magnesium (Mg2+), iron (Fe2+) etc., can be carried out. Among them, copper (Cu2+), manganese (Mn2+), zinc (Zn2+) etc. could add antimicrobial properties against implant-related infections. Double substitutions of TCP containing couples of Cu2+/Sr2+ or Mn2+/Sr2+ ions are considered to be the most perspective based on the results of our study. We established that single phase Ca3−2x(MˊMˊˊ)x(PO4)2 solid solutions are formed only at x ≤ 0.286, where Mˊ and Mˊˊ—divalent metal ions, such as Zn2+, Mg2+, Cu2+, Mn2+, and that in case of double substitutions, the incorporation of Sr2+ ions allows one to extend the limit of solid solution due to the enlargement of the unit cell structure. We also reported that antimicrobial properties depend on the substitution ion occupation of Ca2+ crystal sites in the β-TCP structure. The combination of two different ions in the Ca5 position, on one side, and in the Ca1, Ca2, Ca3, and Ca4 positions, on another side, significantly boosts antimicrobial properties. In the present work, zinc-lithium (Zn-Li) biodegradable alloys were coated with double substituted Mn2+/Sr2+ β-TCP and double substituted Cu2+/ Sr2+ β-TCP, with the scope to promote osteoinductive effect (due to the Sr2+ presence) and to impart antimicrobial properties (thanks to Cu2+ or Mn2+ ions). The Pulsed Laser Deposition (PLD) method was applied as the coating's preparation technique. It was shown that films deposited using PLD present good adhesion strength and hardness and are characterized by a nanostructured background with random microparticles on the surface. For coatings characterization, Fourier Transform Infrared Spectroscopy, X-ray Diffraction, and Scanning Electron Microscopy coupled with Energy Dispersive X-ray and X-ray Photoelectron Spectroscopy were applied. The microbiology tests on the prepared coated Zn-Li alloys were performed with the Gram-positive (Staphylococcus aureus, Enterococcus faecalis) and Gram-negative (Salmonella typhimurium, Escherichia coli) bacteria strains and Candida albicans fungus. The antimicrobial activity tests showed that Mn2+/Sr2+ β-TCP -coated and Cu2+/Sr2+ β-TCP coated Zn-Li alloys were able to inhibit the growth of all five microorganisms. The prepared coatings are promising in improving the degradation behavior and biological properties of Zn-Li alloys, and further studies are necessary before a possible clinical translation

This study reports the mid-term results of a large bearing hybrid metal on metal total hip replacement (MOMHTHR) in 199 hips (185 patients) with mean follow up of 62 months. Clinical, radiological outcome, metal ion levels and retrieval analysis were performed. Seventeen patients (8.6%) had undergone revision, and a further fourteen are awaiting surgery (defined in combination as failures). Twenty one (68%) failures were females. All revisions and ten (71%) of those awaiting revision were symptomatic. Twenty four failures (86%) showed progressive radiological changes. Fourteen revision cases showed evidence of adverse reactions to metal debris (ARMD). The failure cohort had significantly higher whole blood cobalt ion levels (p=0.001), but no significant difference in cup size (p=0.77), inclination (p=0.38) or cup version (p=0.12) in comparison to the non revised cohort. Female gender was associated with an increased risk of failure (chi squared p=0.04). Multifactorial analysis demonstrated isolated raised Co levels in the absence of either symptoms or XR changes was not predictive of failure (p=0.675). However both the presence of pain (p<0.001) and XR changes (p<0.001) in isolation were both significant predictors of failure. Wear analysis (n=5) demonstrated increased wear at the trunnion/head interface (mean out of roundness measurements of 34.5 microns +/−13.3 (+/−2SD, normal range 8-10 microns) with normal levels of wear at the articulating surfaces. There was evidence of corrosion at the proximal and distal stem surfaces. The cumulative survival rate, with revision for any reason was 92.4% (95%CI: 87.4-95.4) at 5 years. Including those awaiting surgery, the revision rate would be 15.1% with cumulative survival at 5 years of 89.6% (95% CI: 83.9-93.4). This MOMHTHR series has demonstrated unacceptable high failure rates with evidence of high wear at the head/trunnion interface and passive corrosion to the stem surface. This raises concern with the use of large heads on conventional 12/14 tapers. Female gender was an independent risk factor of failure. Metal ion levels remain a useful aspect of the investigation work up but in isolation are not predictive of failure

Metal on metal press-fit acetabular cups are the worst performing acetabular cup type with severe failure consequences compared to cups made from more inert materials such as polyethylene or ceramic. The cause of failure of these cup types is widely acknowledged to be multi-factorial, therefore creating a complex scenario for analysis through clinical studies. A factorial analysis has been carried out using an experimentally validated finite element analysis to investigate the relative influence of four input factors associated with acetabular cup implantation on output parameters indicating potential failure of the implantation. These input factors were: cup material stiffness; cup inclination; cup version; cup seating; and level of press-fit. The output parameter failure indicators were: wear; tensile strains in the underlying bone; bone remodelling; and cup-bone micromotions. The factorial analysis concluded that the most significant influence was that of cup inclination on wear, and the second most significant was the influence of the level of press-fit on bone remodelling at the acetabular rim. Significant influence was also observed between version angle and wear, and cup-seating and micro-motion. The results demonstrated the clear multi-factorial nature of implant failure and highlighted the importance of correct implant positioning and fit

The poor outcome of large head metal on metal total hip replacements (LHMOMTHR) in the absence of abnormal articulating surface wear has focussed attention on the trunnion / taper interface. The RedLux ultra-precision 3D form profiler provides a novel indirect optical method to detect small changes in form and surface finish of the head taper as well as quantitative assessment of wear volume. This study aimed to assess and compare qualitatively tapers from small and large diameter MOMTHR's. Tapers from 3 retrieval groups were analysed. Group 1: 28mm CoCr heads from MOMTHRs (n=5); Group 2: Large diameter CoCr heads from LHMOMTHRs (n=5); Gp 3 (control): 28mm heads from metal on polyethylene (MOP) THRs; n=3). Clinical data on the retrievals was collated. RedLux profiling of tapers produced a taper angle and 3D surface maps. The taper angles were compared to those obtained using CMM measurements. There was no difference between groups in mean 12/14 taper angles or bearing surface volumetric and linear wear. Only LHMOMs showed transfer of pattern from stem trunnion to head taper, with clear demarcation of contact and damaged areas.3D surface mapping demonstrated wear patterns compatible with motion or deformations between taper and trunnion in the LHMOM group. These appearances were not seen in tapers from small diameter MOM and MOP THRs. Differences in appearance of the taper surface between poorly functioning LHMOMTHRs and well functioning MOP or MOM small diameter devices highlight an area of concern and potential contributor to the mode of early failure

Reports of improved functional outcome of Metal on Metal Hip Resurfacing Arthroplasty (mHRA) to Total Hip Replacement needs to be balanced with concerns of metal ion release. By removing cobalt-chrome, cHRA reduces these risks. To the author's knowledge, there is no data available on functional outcomes of cHRA, therefore the aim of the study was to compare the function between cHRA patients and mHRA patients. 24 patients received a unilateral cHRA (H1, Embody) and was compared to 24 age and gender matched patients with a unilateral mHRA (BHR, Smith and Nephew). All patients completed the Oxford Hip Score (OHS)[T2] and underwent gait analysis on an instrumented treadmill before and at a mean of 74wks (+/− 10) for mHRA and 53wks (+/− 2) for cHRA post op. Walking trials started at 4km/h and increased in 0.5km/h increments until a top walking speed (TWS) was achieved. Vertical ground reaction forces (GRF) were recorded along with the symmetry index (SI). Spatiotemporal measures of gait were also recorded. Vertical GRF were captured for the entire normalised stance phase using statistical parametric mapping (SPM; CI = 95%). The gain in OHS was similar: H1 (25-46), BHR(27-47). TWS increased by 19% with H1 (6.02 – 8.0km/hr), and 20% with BHR (6.02 – 7.37km/hr). SPM of the entire gait cycle illustrated the restoration of symmetry in both groups with no difference in GRF across the stance phase between groups at 5km/hr pre-op and post-op. At faster speeds (6.5km/hr), H1 patients had a mid-support GRF slightly closer to normal compared to BHR. Both groups increased step length similar from pre to post op (H1:0.76 – 0.85cm, BHR:0.77-0.86cm). In this study, subjective and objective functional outcome measures suggest that short term functional outcomes of ceramic resurfacing is not inferior to metal resurfacing

The biological reaction in metallosis and pseudotumor generation after metal on metal total hip arthroplasty or corroding metal implants remains unsettled. Clinically, still lethal cases appear with massive bone loss and metal ions are suspected to be responsible for this inflammatory reaction, solid metal wear particles instead are usually not observed in the common literature. The aim of this study was to compare the biological reactions of metal ions and metal wear particles in a murine in vivo model. Metal ions (CoCr), metal particles (CoCr), polyethylene particles (UHMWPE) and phosphate buffered saline (PBS) were injected into the left knee joint of female BALB/c mice. 7 days after injection, the microcirculation was observed using intravital fluorescence microscopy, followed by euthanasia of the animals. After the assessment of the knee diameter, the knees underwent histological evaluations of the synovial layer. Throughout all recorded data, CoCr particles caused higher inflammatory reactions compared to metal ions and UHMWPE particles. The mice treated with the solid particles showed enlarged knee diameters, more intensive leukocyte–endothelial cell interactions and an elevated functional capillary density. Pseudotumor-like tissue formations in the synovial layer of the mice were only seen after the exposition to solid CoCr particles. Even if the focus of several national guidelines concerning metallosis and pseudotumor generation is on metal ions, the present data reveal that solid CoCr particles have the strongest inflammatory activity compared with metal ions and UHMWPE particles in vivo

Hip resurfacing arthroplasty (HRA) became a popular procedure in the early 90s because of the improved wear characteristic, preserving nature of the procedure and the optimal stability and range of motion. Concerns raised since 2004 when metal ions were seen in blood and urine of patients with a MoM implant. Design of the prosthesis, acetabular component malpositioning, contact-patch-to-rim distance (CPR) and a reduced joint size all seem to play a role in elevated metal ion concentrations. Little is known about the influence of physical activity (PA) on metal ion concentrations. Implant wear is thought to be a function of use and thus of patient activity levels. Wear of polyethylene acetabular bearings was positively correlated with patient's activity in previous studies. It is hypothesized that daily habitual physical activity of patients with a unilateral resurfacing prosthesis, measured by an activity monitor, is associated with habitual physical activity. A prospective, explorative study was conducted. Only patients with a unilateral hip resurfacing prosthesis and a follow-up of 10 ± 1 years were included. Metal ion concentrations were determined using ICP-MS. Habitual physical activity of subjects was measured in daily living using an acceleration-based activity monitor. Outcome consisted of quantitative and qualitative activity parameters. In total, 16 patients were included. 12 males (75%) and 4 females (25%) with a median age at surgery of 55.5 ± 9.7 years [43.0 – 67.9] and median follow-up of 9.9 ± 1.0 years [9.1 – 10.9]. The median cobalt and chromium ion concentrations were 25 ± 13 and 38 ± 28 nmol/L. A significant relationship, when adjusting for age at surgery, BMI, cup size and cup inclination, between sit-stand transfers (p = .034) and high intensity peaks (p = .001) with cobalt ion concentrations were found (linear regression analysis). This study showed that a high number of sit-stand transfers and a high number of high intensity peaks is significantly correlated with high metal ion concentrations, but results should be interpreted with care. For patients it seems save to engage in activities with low intensity peaks like walking or cycling without triggering critical wear or metal ions being able to achieve important general health benefits and quality of life, although the quality (high intensity peaks) of physical activity and behaviour of patients (sit-stand-transfers) seem to influence metal ion concentrations

Systemic metal ion monitoring (Co;Cr) has proven to be a useful screening tool for implant performance to detect failure at an early stage in metal-on-metal hip arthroplasty. Several clinical studies have reported elevated metal ion levels after total knee arthroplasty (TKA), with fairly high levels associated with rotating hinge knees (RHK) and megaprostheses. 1. In a knee simulator study, Kretzer. 2. , demonstrated volumetric wear and corrosion of metallic surfaces. However, prospective in vivo data are scarce, resulting in a lack of knowledge of how levels evolve over time. The goal of this study was to measure serum Co and Cr levels in several types TKA patients prospectively, evaluate the evolution in time and investigate whether elevated levels could be used as an indicator for implant failure. The study was conducted at Ghent University hospital. 130 patients undergoing knee arthroplasty were included in the study, 35 patients were lost due to logistic problems. 95 patients with 124 knee prostheses had received either a TKA (primary or revision) (69 in 55 patients), a unicompartimental knee arthroplasty (7 UKA), a RHK (revision −7 in 6 patients) or a megaprosthesis (malignant bone tumours − 28 in 27 patients). The TKA, UKA and RHK groups were followed prospectively, with serum Co and Cr ions measured preoperatively, at 3,6 and 12 months postoperatively. In patients with a megaprosthesis, metal ions were measured at follow-up (cross-sectional study design). In primary knees, we did not observe an increase in serum metal ion levels at 3, 6 or 12 months. Two patients with a hip arthroplasty had elevated preTKA Co and Cr levels. There was no difference between unilateral and bilateral knee prostheses. In the revision group, elevated pre-revision levels were found in 2 failures for implant loosening. In both cases, ion levels decreased postoperatively. In revisions with a standard TKA, there was no significant increase in metal ions compared to primary knee arthroplasty. RHK were associated with a significant increase in Co levels even at short-term (3–12 months). The megaprosthesis group had the highest metal ion levels and showed a significant increase in Co and Cr with time in patients followed prospectively. With the current data, we could not demonstrate a correlation between metal ion levels, size of the implant or length of time in situ. In primary knee arthroplasty with a standard TKA or UKA, metal ion levels were not elevated till one year postoperatively. This suggests a different mechanism of metal ion release in comparison to metal-on-metal hip arthroplasties. In two cases of revision for implant loosening, pre-revision levels were elevated, possibly associated with component wear, and decreased after revision. With RHK, slightly elevated ion levels were found prospectively. Megaprostheses had significantly elevated Co and Cr levels, due to corrosion of large metallic surfaces and/or wear of components which were not perfectly aligned during difficult reconstruction after tumour resection. Further research is needed to assess the clinical relevance of metal ion levels in knee arthroplasty

Objectives. Modular dual-mobility (MDM) constructs are used to reduce dislocation rates after total hip replacement (THR). They combine the advantages of dual mobility with the option of supplementary acetabular screw fixation in complex revision surgery. However, there are concerns about adverse reaction to metal debris (ARMD) as a result of fretting corrosion between the metal liner and shell. Methods: The aim of this systematic review was to find and review all relevant studies to establish the outcomes and risks associated with MDM hip replacement. All articles on MDM THRs in the Medline, EMBASE, CINAHL, Cochrane Library, and Prospero databases were searched. A total of 14 articles were included. A random intercept logistic regression model was used for meta-analysis, giving estimated average values. Results: There were 6 cases of ARMD out of 1312 total. Estimated median incidence of ARMD from meta-analysis was 0.3% (95% CI 0.1 – 1.4%). Mean postoperative serum Cobalt was 0.81 μg/L (95% CI 0.33 – 1.29 μg/L), and Chromium was 0.77 μg/L (95% 0.35 – 1.19 μg/L), from 279 cases in 7 studies. Estimated median incidence of a serum cobalt or chromium ion measurement ≥1 μg/L was 7.9% (95% CI 3.5 – 16.8%), and ≥7 μg/L was 1.8% (95% CI 0.7 – 4.2%). Conclusions: ARMD is a rare but significant complication following total hip replacement using a MDM construct. Its incidence appears higher than that reported in non-metal-on-metal (MoM) hip replacements but lower than that of MoM hip replacements. MDM hip replacements are associated with raised serum metal ion levels postoperatively, but there was no correlation with worse clinical hip function within studies. Studies were poor quality and at high risk of confounding. Pending further work, MDM constructs should be used with caution, reserved for select cases at particularly high risk of dislocation

Introduction:. When having to remove broken or embedded metal implants using high speed burrs, the consequence is often a significant amount of metal debris which becomes embedded in the soft tissues. This may then act as a source for a foreign body inflammatory reaction or as a third body wear in the situation of joint arthroplasty. We describe a simple, cheap and effective method of reducing this debris using only a sterile water-based lubricating gel. Materials & Methods:. Several experimental surgical models consisting of porcine muscle over a polyethylene tube with a large fragment titanium locking plate and screw secured to it were constructed. In 8 separate models a screw head locked within the plate was subjected to 90 seconds of high speed burring to create debris. On 4 models no water-based lubricating gel was utilized and on the remaining 4 the surrounding soft tissues were coated in the water-based lubricating gel (AQUAGEL, Halliburton – 42g £1.98). All models were then irrigated with NaCl 500mls using a 20mlsl syringe under manual pressure. Images were then captured after irrigation. The amount of debris was quantified by processing with ImageJ (a public domain, Java-based image processing program developed at the National Institutes of Health and is a computer automated program for counting particles.) The results were then statistically analysed using a student t test (IBM Corp. Released 2011. IBM SPSS Statistics for Windows, Version 20.0. Armonk, NY: IBM Corp.). Results:. the images from the models with water-based gel were shown to have a statistically significant difference in particle number and area within the soft tissues (p=0.001). Conclusion:. We have shown that using a safe, cheap and easily available water-based lubricating gel reduces the amount of embedded debris when burring metal implants using a high-speed burr

Background. Metal-on-metal hip implants can produce adverse tissue reactions to wear debris. Increased metal ion concentrations in the blood are measured as a proxy to wear and the complications it can trigger. Many studies have examined various factors influencing the metal ion concentrations. This is the first study to investigate the effect of physical activity level, as objectively measured in daily life, on blood ion levels, expecting higher concentrations for higher patient activity. Methods. Thirty-three patients (13F/20M, 55.8 ± 6.2 years at surgery) with a unilateral resurfacing hip prosthesis were included. At last follow-up (6.8 ± 1.5 years) cobalt and chromium concentrations in the blood were determined by inductively coupled plasma mass spectrometry. Physical activity was measured during 4 successive days using a 3D-acceleration-based activity monitor. Data was analysed using validated algorithms, producing quantitative and qualitative parameters. Acetabular cup position was measured radiographically. Correlations were tested with Pearson's r'. Results. Wide ranges in cobalt (10-833nmol/l) and chromium (16-592nmol/l) concentrations were measured. No correlations were found between metal ion concentrations and patient characteristics. The mean time of walking per day of was 5475 ± 2730 seconds (≈ 91 minutes) per day, with 6953 ± 3104 steps made during the day. The cadence, the number of steps per minute, was 99.5 ± 7.4. The subjects performed 41 ± 13 sit-stand transfers per day. The number of peak intensity declines when peaks where more intense. No correlations were found between quantitative or qualitative parameters and metal ion concentrations. Conclusions. Higher metal ion concentrations were not correlated with higher activity levels contrary to original expectations. Based on the results the orthopaedic surgeons is able to reassure his or her patients that physical activity in daily living is presumably safe en does not influence metal ion concentrations. Level of Evidence. 2b. Approval. the ethics committee of the Atrium MC, Heerlen approved this study

Abstract. Objectives. Modular dual-mobility (MDM) constructs are used to reduce dislocation rates after total hip replacement (THR). They combine the advantages of dual mobility with the option of supplementary acetabular screw fixation in complex revision surgery. However, there are concerns about adverse reaction to metal debris (ARMD) as a result of fretting corrosion between the metal liner and shell. Methods. The aim of this systematic review was to find and review all relevant studies to establish the outcomes and risks associated with MDM hip replacement. All articles on MDM THRs in the Medline, EMBASE, CINAHL, Cochrane Library, and Prospero databases were searched. A total of 14 articles were included. A random intercept logistic regression model was used for meta-analysis, giving estimated mean values. Results. There were 6 cases of ARMD out of 1312 total. Estimated median incidence of ARMD from meta-analysis was 0.3% (95% CI 0.1 – 1.4%). Mean postoperative serum Cobalt was 0.81 μg/L (95% CI 0.33 – 1.29 μg/L), and Chromium was 0.77 μg/L (95% 0.35 – 1.19 μg/L), from 279 cases in 7 studies. Estimated median incidence of a serum cobalt or chromium ion measurement ≥1 μg/L was 7.9% (95% CI 3.5 – 16.8%), and ≥7 μg/L was 1.8% (95% CI 0.7 – 4.2%). Conclusions. ARMD is a rare but significant complication following total hip replacement using a MDM construct. Its incidence appears higher than that reported in non-metal-on-metal (MoM) hip replacements but lower than that of MoM hip replacements. MDM hip replacements are associated with raised serum metal ion levels postoperatively, but there was no correlation with worse clinical hip function within studies. Studies were poor quality and at high risk of confounding. Pending further work, MDM constructs should be used with caution, reserved for select cases at particularly high risk of dislocation. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Total knee arthroplasty is a well-established treatment for degenerative joint disease, on the other hand metal ion release of cobalt or chromium and particle formation can trigger intolerance reactions. Biotribological examinations can help to assess the metal ion release in different settings. The purpose of this study was the evaluation of inter-laboratory differences in the metal ion concentration analysis. Samples were generated in a 3+1 station knee wear simulator (EndoLab GmbH, Thansau, Germany) with a medium size Columbus Knee System with or without AS multilayer coating. The wear simulation was performed under highly demanding activity (HDA) profile and samples were taken after 0.5, 5.0, 5.5. and 8.0 million cycles. The samples were blinded and sent to three different laboratories and the content of chromium, cobalt, molybdenum, nickel, and zirconium was assessed by inductively coupled plasma mass spectrometry (ICP-MS). The AS multilayer coating clearly reduced the release of chromium, cobalt and molybdenum. Mean levels were: Chromium 9329.78µg/l ± 985.44 vs 503.75µg/l ± 54.19, cobalt 10419.00µg/l ± 15.517.53 vs 2.60µg/l ± 1.35, molybdenum 2496.33µg/l ± 102.62 vs 2.46µg/l ± 2.31. Interestingly we found especially for nickel and zirconium big inter-laboratory differences in the metal assessment. There were up to 10-fold higher values in comparison of one laboratory to another. The data demonstrate that results of metal ion assessment should be evaluated by interlaboratory comparison and should be critically interpreted

Objectives. Third-body wear is believed to be one trigger for adverse results with metal-on-metal (MOM) bearings. Impingement and subluxation may release metal particles from MOM replacements. We therefore challenged MOM bearings with relevant debris types of cobalt–chrome alloy (CoCr), titanium alloy (Ti6Al4V) and polymethylmethacrylate bone cement (PMMA). Methods. Cement flakes (PMMA), CoCr and Ti6Al4V particles (size range 5 µm to 400 µm) were run in a MOM wear simulation. Debris allotments (5 mg) were inserted at ten intervals during the five million cycle (5 Mc) test. . Results. In a clean test phase (0 Mc to 0.8 Mc), lubricants retained their yellow colour. Addition of metal particles at 0.8 Mc turned lubricants black within the first hour of the test and remained so for the duration, while PMMA particles did not change the colour of the lubricant. Rates of wear with PMMA, CoCr and Ti6Al4V debris averaged 0.3 mm. 3. /Mc, 4.1Â mm. 3. /Mc and 6.4 mm. 3. /Mc, respectively. . Conclusions. Metal particles turned simulator lubricants black with rates of wear of MOM bearings an order of magnitude higher than with control PMMA particles. This appeared to model the findings of black, periarticular joint tissues and high CoCr wear in failed MOM replacements. The amount of wear debris produced during a 500 000-cycle interval of gait was 30 to 50 times greater than the weight of triggering particle allotment, indicating that MOM bearings were extremely sensitive to third-body wear. Cite this article: Bone Joint Res 2015;4:29–37

Metal and their alloys have been widely used as implantable materials and prostheses in orthopaedic surgery. However, concerns exist as the metal nanoparticles released from wear of the prostheses cause clinical complications and in some cases result in catastrophic host tissue responses. The mechanism of nanotoxicity and cellular responses to wear metal nanoparticles are largely unknown. The aim of this study was to characterise macrophage phagocytosed cobalt/chromium metal nanoparticles both in vitro and in vivo, and investigate the consequent cytotoxicity. Two types of macrophage cell lines, murine RAW246.7 and human THP-1s were used for in vitro study, and tissues retrieved from pseudotumour patients caused by metal-on-metal hip resurfacing (MoMHR) were used for ex vivo observation. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) in combination with backscatter, energy-disperse X-ray spectrometer (EDS), focused ion beam (FIB) were employed to characterise phagocytosed metal nanoparticles. Alamar blue assay, cell viability assays in addition to confocal microscopy in combination with imaging analysis were employed to study the cytotoxiticy in vitro. The results showed that macrophages phagocytosed cobalt and chromium nanoparticles in vitro and the phagocytosed metal particles were confirmed by backscatter SEM+EDS and FIB+EDS. these particles were toxic to macrophages at a dose dependent manner. The analysis of retrieved tissue from revision of MoMHR showed that cobalt/chromium metal nanoparticles were observed exclusively in living macrophages and fragments of dead macrophages, but they were not seen within either live or dead fibroblasts. Dead fibroblasts were associated with dead and disintegrated macrophages and were not directly in contact with metal particles; chromium but not cobalt was the predominant component remaining in tissue. We conclude that as an important type of innate immune cells and phagocytes, macrophages play a key role in metal nanoparticles related cytotoxicity. Metal nanoparticles are taken up mainly by macrophages. They corrode in an acidic environment of the phagosomes. Cobalt that is more soluble than chromium may release inside macrophages to cause death of individual nanoparticle-overloaded macrophages. It is then released into the local environment and results in death of fibroblasts and is subsequently leached from the tissue

Metal-on-metal (MOM) hip arthroplasty, including resurfacing, has become the subject of recent research and debate. There is the perceived benefit of improved wear rates of bearing surfaces leading to superior durability and performance of these types of implant. An associated feature of MOM bearing surfaces is the generation of metal ions. These can have local and systemic cytotoxic effects. An immunoloigical response has been suggested, however, metal wear debris may cause direct damage to cellular DNA. Studies have shown that release of these ions is related to bearing diameter and component alignment. However, little is known about the relationship between metal ion levels and implant survivorship. The MHRA has published guidelines on the follow-up of patients with MOM implants including measurement of serum ion levels and cross sectional imaging. Between February 2001 and November 2009, 135 patients (164 hips) had MOM resurfacing arthroplasty at our institution. We report a retrospective analysis of the data generated by review of these patients. Of the 135 patients, 91 were identified for clinical review. Each patient had serum metal ion levels measured, plain AP radiographs of the pelvis examined and, in the presence of raised metal ions, a Metal Artefact Reduction Sequence (MARS) MRI performed. 27 patients (35 hips) had raised metal ion levels (Cobalt and Chromium). Patients with raised metal ion levels had a mean acetabular cup inclination of 52.7 degrees compared with a mean inclination of 48.6 degrees in patients with normal ion levels (p<0.05). MARS MRI in the raised ion group revealed 9 patients with appearances suggestive of ALVAL. A number of these patients had hip revision surgery with the remainder awaiting potential revision. These findings reflect current evidence suggesting a relationship between sub-optimal component position and raised metal ion levels and an increased rate of ALVAL

The biological significance of cobalt-chromium wear particles from metal-on-metal hip replacements may be different to the effects of the constituent metal ions in solution. Bacteria may be able to discriminate between particulate and ionic forms of these metals because of a transmembrane nickel/cobalt-permease. It is not known whether wear particles are bacteriocidal. We compared the doubling time of coagulase negative staphylococcus, Staphylococcus aureus and methicillin resistant S. aureus when cultured in either wear particles from a metal-on-metal hip simulator, wear particles from a metal-on-polyethylene hip simulator, metal ions in solution or a control. Doubling time halved in metal-on-metal (p = 0.003) and metal-on-polyethylene (p = 0.131) particulate debris compared with the control. Bacterial nickel/cobalt-transporters allow metal ions but not wear particles to cross bacterial membranes. This may be useful for testing the biological characteristics of different wear debris. This experiment also shows that metal-on-metal hip wear debris is not bacteriocidal

Different 3D printing techniques for orthopaedic ceramic implants fabrication were compared. Stereolithography of calcium-phosphate slurries makes possible to achieve pre-determined pore size (50 mkm and more) and porosity of 70–80%. For the first time ceramic implants based on double calcium alkali metal phosphates (rhenanites) with given architecture serving good osteoconductivity as well as high resorptivity and strength (up to 10 MPa) were obtained. Development of biomaterials based on calcium phosphates for orthopaedics is an important area of modern materials science. Chemical, physical and mechanical compatibility of this materials is a primary goal for this field. An ideal implant should gradually dissolve and be replaced by the new bone tissue in the patience body. Bone is a multilevel organic/inorganic composite and the main inorganic compound is hydroxyapatite (HA, Ca. 10. (PO. 4. ). 6. (OH). 2. ). Due to this, biomaterials based on HA are widely used, along with biomaterials based on tricalcium phosphate (TCP, Ca. 3. (PO. 4. ). 2. ); however, low solubility of HA (lowest soluble phosphate) as well as TCP does not meet all of the requirements that biomaterials should have. In this work decreasing of the crystal lattice energy approach was used as a strategy of improving the solubility. Modifying the chemical composition by replacing Ca. 2+. cation in the TCP structure by a singly charged alkali metal cation leads to structural changes from TCP to CaMPO. 4. (M=Na, K) – rhenanite. This work focuses on using double calcium alkali metal phosphates Ca. (3 – x). М. 2x. (PO. 4. ). 2. (x = 0–1, М = Na, K) as bioresorbable osteoconductive ceramic implant. Additive manufacturing techniques are the most competitive technology which has been applied in the medical field for the direct or indirect construction of scaffolds and hard or soft tissues. Different techniques were used to prepare ceramics with given structure based on double calcium alkali metals phosphates to improve its osteoconductive properties. High resolution stereolithography (SLA) of ceramic photocurable resins has a great potential in fabrication of high quality complex shaped ceramics. For the first time ceramic implants based on double calcium alkali metal phosphates (rhenanites) with pre-determined pore size (50 mkm and more) and porosity of 70–80% were obtained. Given architecture of scaffold is serving a good osteoconductivity as well as a high resorptivity and strength (up to 10 MPa). High resolution SLA can be easily used for fabrication of a small size implants (3mm in diameter/height or less) for in vivo experiments, and it can be freely used to fit any shade in osteoconductive properties of ceramic materials designed for bone grafting. Russian Science Foundation supported this study under Grant No. 14-19-00752. The authors acknowledge partial support from Lomonosov Moscow State University Program of Development