Titanium alloys are one of the most used for orthopaedic implants and the fabrication of them by 3D printing technology is a raising technology, which could effectively resolve existing challenges. Surface modification of Ti surfaces is often necessary to improve biocorrosion resistance, especially in inflammatory conditions. Such modification can be made by coatings based on hydrogels, like alginate (Alg) - a naturally occurring anionic polymer. The properties of the hydrogel can be further enhanced with calcium phosphates like octacalcium phosphate (OCP) as a precursor of biologically formed hydroxyapatite. Formed Alg-OCP matrices have a high potential in wound healing, delivery of bioactive agents etc. but their effect on 3D printed Ti alloys performance was not well known. In this work, Alg-OCP coated 3D printed samples were studied with electrochemical measurements and revealed significant variations of corrosion resistance vs. composition of the coating. The potentiodynamic polarization test showed that the Alg-OCP-coated samples had lower corrosion current density than simple Alg-coated samples. Electrochemical impedance spectroscopy indicated that OCP incorporated hydrogels had also a high value of the Bode modulus and phase angle. Hence Alg-OCP hydrogels could be highly beneficial in protecting 3D printed Ti alloys especially when the host conditions for the implant placement are inflammatory. AcThis work was supported by the European Union Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Actions GA860462 (PREMUROSA). The authors also acknowledge the access to the infrastructure and expertise of the BBCE – Baltic Biomaterials Centre of Excellence (European Union Horizon 2020 programme under GA857287)

Summary. Corrosion and fretting damage at the head-neck interface of artificial hip joints is more severe with larger head sizes. This is a concern, as the release of metal particles and ions can cause adverse tissue reactions, similar to those observed high wear metal-on-metal articulations. Introduction. In the last few years corrosion was increasingly observed at head-neck interfaces of artificial hip joints, especially in joints with larger heads. There has always been evidence of some corrosion at modular junctions of artificial joints, but except for few designs, it was not seen as a real problem. It is important to better understand the factors contributing to corrosion at modular interfaces, so that necessary improvements can be made to minimise or completely avoid corrosion, in order to avoid possible adverse tissue reactions. Methods. Over 100 retrieved stems and heads of 28, 32, 36, 40 and larger heads with metal-on-polyethylene (MoP) and metal-on-metal (MoM) articulations were scored for corrosion and fretting damage, in order to get a better picture of the magnitude of the problem. For some of the head sizes it was possible to assess the fretting and corrosion damage separately from implants from two different manufacturers. The tapers of the stem and head were subdivided into eight regions each, and scored for the severity of fretting and corrosion damage, as well as of the affected area within each sub-section. The scoring was undertaken by three persons with a fair intraclass correlation. The fretting and corrosion scores were also assessed based on the location of the center of the head with respect to the center of the taper. The distance between these two centers influences the toggling motion between the head and neck, as the main load is about 30 degrees out of axis during walking and other activities of daily living. Results. It was found that head-neck interfaces of two manufacturers of 36mm heads had significantly more corrosion than 28mm heads. There is a significant relationship between head and neck fretting damage, and between corrosion and fretting damage. There is also more corrosion damage in 32, 40 and larger heads, but these groups were from different manufacturers, so that it was not possible to perform statistical tests. More corrosion was observed when the centre of the head was at a larger distance from the centre of the head, leading to an increased toggling moment due to the out-of-axis loading. Discussion. It is of some concern that more corrosion is being observed with larger heads. Corrosion generally gets worse over time, which could negatively impact on the long-term behavior of these hip joints. Furthermore, it is possible that the metal particle and ion release due to corrosion and fretting could have adverse soft tissue reactions, similar to those observed at some MoM articulations. The fact that there are significant differences in the observed corrosion and fretting damage between the head-neck interfaces of two companies, indicates that even subtle changes in the geometry and the machined taper surface are important. A better understanding of these factors is required to make sure that the corrosion and fretting damage is minimised, or even better eliminated for all heads of artificial joints

Adhered bacteria on titanium surfaces are able to decrease its corrosion potential and impedance values at the lowest frequencies. This result points to the detrimental influence of the biofilm on the passive film formed on the surfaces, independently on the surface finishes. Titanium is one of the most used metallic biomaterials for biological and implant applications. The spontaneous formation of a protective passive film around 2–5 nm thick, make titanium unique as a biomaterial for implants. Its composition has been described by a three-layer model: TiO2/Ti2O3/TiO and its stability is ultimately responsible for the success of osseointegrated titanium implants. The cases of breakdown of the protective passive film are associated with highly acidic environments induced by bacterial biofilms and/or inflammatory processes that lead to localized corrosion of titanium and, in extreme cases, implant failure. Bearing in mind that the surface design of a titanium implant is a key element involved in the healing mechanisms at the bone-implant interface, the surface modifications have sought to enhance the biomechanical anchorage of the implant and promote osseointegration at the cell-biomolecular level. However, little attention has been paid to the effects of these surface modifications in the microbiologically induced corrosion (MIC). The aim of this work is to evaluate the potential for MIC of titanium in the short term under viable bacterial cells of Streptococcus mutansas a representative microorganism of oral biofilm considered to be a highly cariogenic pathogen. Discs of 64 mm. 2. surface area of commercially pure titanium, grade 4, were supplied by Biotechnology Institute (BTI, Vitoria, Spain). Four surface treatments were studied: two acid etchings (low roughness, opN and high roughness, opV). In addition, acid etched plus anodic oxidation (opNT). For comparative purposes, two surface finishes have been included: high roughness – corresponding with sandblasting-large grit plus acid (SLA); and, as-machined titanium (mach). The oral strain used for assessing the biofilm formation on the corrosion behavior of Ti surfaces was Streptococus mutansATCC 25175, obtained from the Spanish Type Culture Collection (CECT). The study of MIC from Streptococcus mutanson surfaces of Ti was carried out in an electrochemical cell specifically designed and patented by some of the present authors [1]. A three set up configuration of the electrochemical cell was used in the experiments. The measurement of the corrosion potential and electrochemical impedance was performed at different periods of incubation of bacteria: 2, 7, 15, 21 and 28 days. Out Slight but continuous decrease in the corrosion potential and impedance values at the lowest frequencies indicate the deleterious influence of the biofilm on the passive film formed on the surfaces, independently on the surface finishes. This research suggests that the most appropriate surface modification for the dental implant portion at the bone level would be the acid etched of high roughness (opV) surface

Objectives. Mechanical wear and corrosion at the head-stem junction of total hip arthroplasties (THAs) (trunnionosis) have been implicated in their early revision, most commonly in metal-on-metal (MOM) hips. We can isolate the role of the head-stem junction as the predominant source of metal release by investigating non-MOM hips; this can help to identify clinically significant volumes of material loss and corrosion from these surfaces. Methods. In this study we examined a series of 94 retrieved metal-on-polyethylene (MOP) hips for evidence of corrosion and material loss at the taper junction using a well published visual grading method and an established roundness-measuring machine protocol. Hips were retrieved from 74 male and 20 female patients with a median age of 57 years (30 to 76) and a median time to revision of 215 months (2 to 324). The reasons for revision were loosening of both the acetabular component and the stem (n = 29), loosening of the acetabular component (n = 58) and infection (n = 7). No adverse tissue reactions were reported by the revision surgeons. Results. Evidence of corrosion was observed in 55% of hips. The median Goldberg taper corrosion score was 2 (1 to 4) and the annual rate of material loss at the taper was 0.084 mm. 3. /year (0 to 0.239). The median trunnion corrosion score was 1 (1 to 3). Conclusions. We have reported a level of trunnionosis for MOP hips with large-diameter heads that were revised for reasons other than trunnionosis, and therefore may be clinically insignificant. Cite this article: H. S. Hothi, D. Kendoff, C. Lausmann, J. Henckel, T. Gehrke, J. Skinner, A. Hart. Clinically insignificant trunnionosis in large-diameter metal-on-polyethylene total hip arthroplasty. Bone Joint Res 2017;6:52–56. DOI: 10.1302/2046-3758.61.BJR-2016-0150.R2

Introduction. The National Joint Registry has recently identified failure of large head metal on metal hip replacements. This failure is associated with the high torque at the interface of standard modular taper junction leading to fretting and corrosion. A number of manufacturers produce mini spigots, which in theory, provide a greater range of motion as the neck head junction is reduced. However, the relative torque to interface ratio at this junction is also increased. In this study we investigated hypothesis that the use of small spigots (minispigots) will increase wear and corrosion on modular tapers. Methods. Wear and corrosion of spigots were compared in-vitro when loaded with a force representative of the resultant force passing through the hip. The heads (female tapers) were made of cobalt-chrome-molybdenum (CoCrMo) and the stems (male tapers) of titanium alloy (Ti). Commercially available tapers and heads were used. The surface parameters & profiles were measured before & after testing. Electrochemical static and dynamic corrosion (pitting) tests were performed on minispigots under loaded and non-loaded conditions. Results. Post-testing the surface parameters Ra, Ry & Rz on the head taper associated with the minispigots had become greater compared with standard spigots. In all instances the profile of the titanium male tapers was unchanged. SEM showed the corroded region of the head was similar to the profile on the Ti male taper, with evidence of pitting in the cobalt chrome. In the CoCrMo/ Ti combinations, wear and corrosion were increased in minispigots compared with standard spigots. On minispigots the rough surface finishes were affected more severely than those with a smoother surface. Static corrosion tests showed evidence of fretting in the rough but not the smooth minispigots. Pitting scans showed a greater hysteresis with the rough surface finishes on the minispogot indicating potentially greater corrosion in the former. Conclusion. The relative size of the taper in comparison to the head combined with the surface finish was crucial. As the relative torque to interface ratio at this junction increased corrosion of the cobalt chrome head increases and is further enhanced if the surface finish on the tapers is rough

Material loss at the head-stem taper junction may contribute to the high early failure rates of stemmed large head metal-on-metal (LH-MOM) hip replacements. We sought to quantify both wear and corrosion and by doing so determine the main mechanism of material loss at the taper. This was a retrospective study of 78 patients having undergone revision of a LH-MOM hip replacement. All relevant clinical data was recorded. Corrosion was assessed using light microscopy and scanning electron microscopy, and graded according to a well-published classification system. We then measured the volumetric wear of the bearing and taper surfaces. Evidence of at least mild taper corrosion was seen in 90% cases, with 46% severely corroded. SEM confirmed the presence of corrosion debris, pits and fretting damage. However, volumetric wear of the taper surfaces was significantly lower than that of the bearing surfaces (p = 0.015). Our study supports corrosion as the predominant mechanism of material loss at the taper junction of LH-MOM hip replacements. Although the volume of material loss is low, the ionic products may be more biologically active compared to the particulate debris arising from the bearing surfaces

Summary Statement. Fretting and corrosion has been identified as a clinical problem in modular metal-on-metal THA, but remains poorly understood in modern THA devices with polyethylene bearings. This study investigates taper damage and if this damage is associated with polyethylene wear. Introduction. Degradation of modular head-neck tapers was raised as a concern in the 1990s (Gilbert 1993). The incidence of fretting and corrosion among modern, metal-on-polyethylene and ceramic-on-polyethylene THA systems with 36+ mm femoral heads remains poorly understood. Additionally, it is unknown whether metal debris from modular tapers could increase wear rates of highly crosslinked PE (HXLPE) liners. The purpose of this study was to characterise the severity of fretting and corrosion at head-neck modular interfaces in retrieved conventional and HXLPE THA systems and its effect on penetration rates. Patients & Methods. 386 CoCr alloy heads from 5 manufacturers were analyzed along with 166 stems (38 with ceramic femoral heads). Metal and ceramic components were cleaned and examined at the head taper and stem taper by two investigators. Scores ranging from 1 (mild) to 4 (severe) were assigned in accordance with the semi-quantitative method adapted from a previously published technique. Linear penetration of liners was measured using a calibrated digital micrometer (accuracy: 0.001 mm). Devices implanted less than 1 year were excluded from this analysis because in the short-term, creep dominates penetration of the head into the liner. Results. The majority of the components were revised for instability, infection, and loosening. Mild to severe taper damage (score ≥2) was found in 77% of head tapers and 52% of stem tapers. The extent of damage was correlated to implantation time at the head taper (p=0.0004) and at the stem taper (p=0.0004). Damage scores were statistically elevated on CoCr heads than the matched stems (mean score difference=0.5; p<0.0001) and the two metrics were positively correlated with each other (ρ=0.41). No difference was observed between stem taper damage and head material (CoCr, ceramic) (p=0.56), nor was a correlation found between taper damage and head size (p=0.85). The penetration rate across different formulations of HXLPE was not found to be significantly different (p=0.07), and therefore grouped together for further analysis. Within this cohort, penetration rate was not found to be associated with head size (p=0.08) though a negative correlation with implantation time was noted (ρ=−0.35). When analyzed along with taper damage scores, a correlation was not observed between head taper damage scores and HXLPE penetration rates (p=0.51). Discussion. The results of this study do not support the hypothesis that 36+ mm ceramic or CoCr femoral heads articulating on HXLPE liners are associated with increased risk of corrosion among HXLPE liners when compared with smaller diameter heads. A limitation of this study is the semi-quantitative scoring technique, heterogeneity of the retrieval collection and short implantation time of the larger diameter heads. Because corrosion may increase over time in vivo, longer-term follow-up, coupled with quantitative taper wear measurement, will better assess the natural progression of taper degradation in modern THA bearings

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

Increased failure rates due to metallic wear particle-associated adverse local tissue reactions (ALTR) is a significant clinical problem in resurfacing and total hip arthroplasty. Histological analysis and particle characterization are important elements for understanding the biological mechanisms of the reaction and different histological subtypes may have unique needs for longitudinal clinical follow-up and complication rates after revision arthroplasty.

Consecutive patients (N=285 cases) presenting with ALTR from three major hip implant classes, metal-on-metal resurfacing and total hip arthroplasty (THA) and non-metal-on-metal THA with dual modular neck were identified from our prospective Osteolysis Tissue Database and Repository and 53 cases were selected for wear particle nano-analysis.

Conventional histology: Tissue samples taken from multiple regions around the hip with extensive sampling performed at macroscopic examination were examined by light microscopy.

Particle analysis: Tissue samples selected after frozen section evaluation for cellularity and particle content were examined by scanning electron microscopy (SEM), backscatter scanning electron microscopy (BSEM), BSEM-energy-dispersive X-ray spectroscopy (EDS) element mapping examination, transmission electron microscopy (TEM), TEM-EDS element mapping, and X-ray diffraction spectrometry (XRD) examination.

ALTR encompasses three main histological patterns: 1) macrophage predominant, 2) mixed lymphocytic and macrophagic, and 3) predominant sarcoid-like granulomas. Duration of implantation and composition of periprosthetic cellular infiltrates was significantly different among the three implant types examined. Distinct differences in the size, shape, and element composition of the metallic particulate material were detected in each implant class, with correlation of the severity of the adverse reaction with element complexity of the particles.

ALTR encompasses a diverse range of histological patterns, which are reflective of both the implant configuration independent of manufacturer and clinical features such as duration of implantation. Distinct differences in the metallic particulate material can contribute to explain the histological features of the ALTR and variability of performance of the implants.

ALTR exhibits different histological patterns and is dependent on the characteristics of the wear particulate material of each implant class and host immunological reaction.

Reducing wear of endoprosthetic implants is still an important goal in order to increase the life time of the implant. Endoprosthesis failure can be caused by many different mechanisms, such as abrasive wear, corrosion, fretting or foreign body reactions due to wear accumulation. Especially, modular junctions exhibit high wear rates and corrosion due to micromotions at the connection of the individual components. The wear generation of cobalt-chromium-molybdenum alloys (CoCrMo) is strongly influenced by the microstructure. Therefore, the aim of this work is to investigate the subsurface phase transformation by deep rolling manufacturing processes in combination with a “sub-zero” cooling strategy. We analyzed the influence on the phase structure and the mechanical properties of wrought CoCr28Mo6 alloy (ISO 5832-12) by a deep rolling manufacturing process at various temperatures (+25°C,-10°C,-35°C) and different normal forces (700N and 1400N). Surface (S. a. ,S. z. ) and subsurface characteristics (residual stress) as well as biological behavior were investigated for a potential implant application. We showed that the microstructure of CoCr28Mo6 wrought alloy changes depending on applied force and temperature. The face centered cubic (fcc) phase could be transformed to a harder hexagonal-close-packed (hcp) phase structure in the subsurface. The surface could be smoothed (up to S. a. = 0.387 µm±0.185 µm) and hardened (≥ 700 HV 0.1) at the same time. The residual stress was increased by more than 600% (n=3). As a readout for metabolic activity of MonoMac (MM6) and osteosarcoma (SaOS-2) cells a WST assay (n=3) was used. The cells showed no significant negative effect of the sub-zero manufacturing process. We showed that deep rolling in combination with an innovative cooling strategy for the manufacturing process has a great potential to improve the mechanical properties of CoCr28Mo6 wrought alloy, by subsurface hardening and phase transformation for implant applications

Abstract. Objectives. Total hip replacement (THR) is one of the most successful and cost-effective interventions in orthopaedic surgery. Dislocation is a debilitating complication of THR and managing an unstable THR constitutes a significant clinical challenge. Stability in THR is multifactorial and is influenced by surgical, patient and implant related factors. It is established that larger diameter femoral heads have a wider impingement-free range of movement and an increase in jump distance, both of which are relevant in reducing the risk of dislocation. However, they can generate higher frictional torque which has led to concerns related to increased wear and loosening. Furthermore, the potential for taper corrosion or trunnionosis is also a potential concern with larger femoral heads, particularly those made from cobalt-chrome. These concerns have meant there is hesitancy among surgeons to use larger sized heads. This study presents the comparison of clinical outcomes for different head sizes (28mm, 32mm and 36mm) in primary THR for 10,104 hips in a single centre. Methods. A retrospective study of all consecutive patients who underwent primary THR at our institution between 1st April 2003 and 31st Dec 2019 was undertaken. Institutional approval for this study was obtained. Demographic and surgical data were collected. The primary outcome measures were all-cause revision, revision for dislocation, and all-cause revision excluding dislocation. Continuous descriptive statistics used means, median values, ranges, and 95% confidence intervals where appropriate. Kaplan-Meier survival curves were used to estimate time to revision. Cox proportional hazard regression analysis was used to compare revision rates between the femoral head size groups. Adjustments were made for age at surgery, gender, primary diagnosis, ASA score, articulation type, and fixation method. Results. 10,104 primary THRs were included; median age 68.6 years with 61.5% females. A posterior approach was performed in 71.6%. There were 3,295 hips with 28 mm heads (32.6%), 4,858 (48.1%) with 32 mm heads and 1,951 (19.3%) with 36 mm heads. Overall rate of revision was 1.7% with the lowest rate recorded for the 36mm group (2.7% vs. 1.3% vs. 1.1%). Cox regression analysis showed a decreased risk of all-cause revision for 32mm & 36mm head sizes as compared to 28mm; this was statistically significant for the 32mm group (p = 0.01). Risk of revision for dislocation was significantly reduced in both 32mm (p = 0.03) and 36mm (p = 0.03) head sizes. Analysis of all cause revision excluding dislocation showed no significant differences between head sizes. Conclusion. There was a significantly reduced risk of revision for all causes, but particularly revision for dislocation with larger head sizes (36mm & 32mm vs. 28mm). Concerns regarding increased risk of early revision for aseptic loosening, polyethylene wear or taper corrosion with larger heads appear to be unfounded in this cohort of 10,104 patients with a mean of 6.0-year follow-up. 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

Objectives. Taper junctions between modular hip arthroplasty femoral heads and stems fail by wear or corrosion which can be caused by relative motion at their interface. Increasing the assembly force can reduce relative motion and corrosion but may also damage surrounding tissues. The purpose of this study was to determine the effects of increasing the impaction energy and the stiffness of the impactor tool on the stability of the taper junction and on the forces transmitted through the patient’s surrounding tissues. Methods. A commercially available impaction tool was modified to assemble components in the laboratory using impactor tips with varying stiffness at different applied energy levels. Springs were mounted below the modular components to represent the patient. The pull-off force of the head from the stem was measured to assess stability, and the displacement of the springs was measured to assess the force transmitted to the patient’s tissues. Results. The pull-off force of the head increased as the stiffness of the impactor tip increased but without increasing the force transmitted through the springs (patient). Increasing the impaction energy increased the pull-off force but also increased the force transmitted through the springs. Conclusions. To limit wear and corrosion, manufacturers should maximize the stiffness of the impactor tool but without damaging the surface of the head. This strategy will maximize the stability of the head on the stem for a given applied energy, without influencing the force transmitted through the patient’s tissues. Current impactor designs already appear to approach this limit. Increasing the applied energy (which is dependent on the mass of the hammer and square of the contact speed) increases the stability of the modular connection but proportionally increases the force transmitted through the patient’s tissues, as well as to the surface of the head, and should be restricted to safe levels. Cite this article: A. Krull, M. M. Morlock, N. E. Bishop. Maximizing the fixation strength of modular components by impaction without tissue damage. Bone Joint Res 2018;7:196–204. DOI: 10.1302/2046-3758.72.BJR-2017-0078.R2

AM specifically allows for cost-efficient production of patient-specific Orthopaedic medical devices with unusual designs and properties. A porous design allows to adjust the stiffness of metallic implants to that of the host bone. Beyond traditional metals, like titanium alloys, this talk will review the present state-of-the-art of directly printed absorbable metal families. Physicochemical, mechanical and biological properties of standardized design prototypes from all currently available metal families will be compared and their clinical application potential discussed. The impact of in vitro test environments on comparative corrosion behavior, post manufacturing aspects, and the recent status quo in biocompatibility testing and present knowledge gaps will be addressed

Direct metal printed (DMP) porous iron implants possess promising mechanical and corrosion properties for various clinical application. Nevertheless, there is a requirement for better co-relation between in vitro and in vivo corrosion and biocompatibility behaviour of such biomaterials. Our present study evaluates absorption of porous iron implants under both static and dynamic conditions. Furthermore, this study characterizes their cytocompatibility using fibroblastic, osteogenic, endothelial and macrophagic cell types. In vitro degradation was performed statically and dynamically in a custom-built set-up placed under cell culture conditions (37 °C, 5% CO2 and 20% O2) for 28 days. The morphology and composition of the degradation products were analysed by scanning electron microscopy (SEM, JSM-IT100, JEOL). Iron implants before and after immersion were imaged by μCT (Quantum FX, Perkin Elmer, USA). Biocompatibility was also evaluated under static and dynamic in vitro culture conditions using L929, MG-63, HUVEC and RAW 264.7 cell lines. According to ISO 10993, cytocompatibility was evaluated directly using live/dead staining (Live and Dead Cell Assay kit, Abcam) in dual channel fluorescent optical imaging (FOI) and additionally quantified by flow cytometry. Furthermore, cytotoxicity was indirectly quantified using ISO conform extracts in proliferation assays. Strut size of DMP porous iron implants was 420 microns, with a porosity of 64% ± 0.2% as measured by micro-CT. After 28 days of physiological degradation in vitro, dynamically tested samples were covered with brownish degradation products. They revealed a 5.7- fold higher weight loss than statically tested samples, without significant changes in medium pH. Mechanical properties (E = 1600–1800 MPa) of these additively manufactured implants were still within the range of the values reported for trabecular bone, even after 28 days of biodegradation. Less than 25% cytotoxicity at 85% of the investigated time points was measured with L929 cells, while MG-63 and HUVEC cells showed 75% and 60% viability, respectively, after 24 h, with a decreasing trend with longer incubations. Cytotoxicity was analysed by two-way ANOVA and post-hoc Tukey's multiple comparisons test. Under dynamic culture conditions, live-dead staining and flow cytometric quantification showed a 2.8-fold and 5.7-fold increase in L929 and MG-63 cell survival rates, respectively, as compared to static conditions. Therefore, rationally designed and properly coated iron-based implants hold potential as a new generation of absorbable Orthopaedic implants

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

In order to evaluate the feasibility of zinc alloys as future biodegradable bone implant materials, the mechanical properties, corrosion resistance, hemocompatibility, cell activity, proliferation and adhesion, in vivo animal implantation experiments have been employed. The experimental results show that the alloying element magnesium, calcium and strontium can significantly improve the mechanical properties of pure zinc, and further deformation processes can further improve the mechanical properties of zinc alloys. Alloying elements can effectively control the corrosion rates of zinc alloys, which are between the rates of magnesium alloys and iron alloys. Zinc and zinc alloys exhibit excellent hemocompatibility and the hemolysis rate is far lower than 5%. After adding alloying elements Mg, Ca and Sr, MG63 and ECV304 cell proliferation rate and activity increased significantly, while for VSMC cell, the influence of alloying elements effect is not obvious. Zinc alloy intramedullary pins can effectively promote the new bone formation, and after 2 months implanted in mice femur, they still maintained a relatively complete structure, indicating that they are able to provide enough mechanical strength and thus more conducive to bone tissue repair and healing

Modular hip prostheses were introduced to optimize the intra-surgical adaptation of the implant design to the native anatomy und biomechanics of the hip. The downside of a modular implant design with an additional modular interface is the potential susceptibility to fretting, crevice corrosion and wear. For testing hip implants with proximal femoral modularity according to ISO & ASTM, sodium chloride solutions are frequently used to determine the fatigue strength and durability of the stem-neck connection. The present study illustrate that the expansion of standard requirements of biomechanical testing is necessary to simulate metal ion release as well as fretting and crevice corrosion by using alternative test fluids. To assess the primary stability of tibial plateaus in vitro, different approaches had been undergone: cement penetration depth analysis, static tension or compression loading until interface failure. However, these test conditions do not reflect the in vivo physiologic loading modes, where the tibial plateau is predominantly subjected to combined compression and shear forces. The objectives were to evaluate the impact of the tibial keel & stem length on the primary stability of a posterior-stabilised tibial plateau under dynamic compression-shear loading conditions in human tibiae

Summary. Metal Injection Molding could provide cost saving of about 20–50% for implantable medical device manufacturing and hence healthcare public spending. Corrosion behaviour and biocompatibility of the new manufactured alloy were studied and showed similar behaviour compared to the traditional one. Introduction. The growing trend for total joint arthroplasties could raise healthcare costs in the near future. Metal Injection Molding (MIM) is a near net shape manufacturing technology and allows the production of finite prosthesis components saving the machining step, and so resources, up to 20–50%. In order to apply such process to the production of actual devices, the bulk material have to show biocompatibility and corrosion behaviour similar to the traditional one. (ASTM F2083, ISO 21536) The aim of this work was to compare cast and forged CoCrMo alloy with the MIM one from the electrochemical point of view and cytocompatibility. Material and Methods. Metallographic observations by optical microscopy and SEM were taken to better understand the electrochemical behaviour. This evaluation was performed through potentiodynamic tests on MIM and forged (FOR) samples with polished and sandblasted surfaces (as the actual devices), in ASTM G5 cell with saline solution simulating the body environment, graphite counter electrodes and Ag/AgCl 0.15M NaCl reference electrode. Linear polarization, open circuit potential measurements and potentiostatic tests at +335 mV vs SCE were also performed during 10 days to have direct information on the corrosion resistance and ion release. Cell viability were also assessed through MTT test on polished MIM and cast (CAS) elutes, after 2 and 7 days contact periods, following ISO 10993 directions. Static ion release in H. 2. O at 2, 4 and 8 weeks were also performed. Results. MIM showed coarser grains, free of boundary carbide but with lots of circular porosities and stacking faults, in comparison with CAS structure, which presented many carbides and typical dendritic grain. Electrochemical tests exhibited analogue behaviour for the MIM and FOR CoCrMo alloys. The slightly lower passive current density and transpassive potential values obtained could be ascribed to a passive oxide layer on the MIM sample less protective than FOR CoCrMo one, as inferable from the OCP measurements, but these facts had no visible influence on polarization resistance and ion release. Such good corrosion behaviour was reflected also in static ion release results and MTT viability results, which were comparable, not only to CAS samples but also to the control medium. Conclusions. From such preliminary results MIM technology showed to have good possibility for the production of implantable medical devices with CoCrMo alloy. Corrosion resistance and biocompatibility seemed not to be affected by the different manufacturing technique. Further studies will be needed to asses also the equivalence of mechanical properties. From the metallographic observations the absence of second phases and the homogeneous microstructure suggests a better fatigue performance for this kind of alloy, even if some concerns arise from the widespread porosity observed

Neck modularity has been proposed to improve THA accuracy, thanks to the close restoration of anatomy, however it has been associated with issues like early breakages or corrosion. Our Hospital has been using neck modularity since the 90s, so we analyzed retrospectively implants performed between January 2000 and December 2014. The minimum follow up was 1Y. The cohort was composed of 1,033 THAs or 951 patients (82 bilateral), of which 643 females and 390 males. Average patient age was 67.7Y. THA indications were primary Osteoarthritis (80.9%), Fracture (9.0%), Congenital Dysplasia or Congenital Luxation (4.2%), Osteonecrosis (3.2%), other causes (2,7%). The stems used were all cementless, 381 anatomically shaped (36.9%), 635 straight (61.5%), 17 short MIS (1.6%). All necks used were made of Titanium alloy. 419 implants (40.5%) were manufactured by Wright Medical, while 614 (59.5%) were produced by Adler Ortho. A total of 37 revisions has been reported, mainly due to periprosthetic fractures (32.4%), luxation (24.3%), implant mobilization (18.9%) and implant breakage (16.2%). We have recorded 3 modular neck breakages. 4 patients required re-revisions, because of luxations (3) and neck breakage (1). The overall survival rate was 96.4%. We did not observe any component corrosion, probably thanks to the exclusive use of Titanium necks. We had a neck breakages rate of 0.29% and a luxation rate of 0.87%, lower than normally reported in the literature. In conclusion, our experience suggests as neck modularity could be a safe and effective way to reconstruct the proximal femur in THA patients

Summary. The required torque leading to an abrasion of the passive layer in the stem-head interface positively correlates to the assembly force. In order to limit the risk of fretting and corrosion a strong hammer blow seems to be necessary. Introduction. Modular hip prostheses are commonly used in orthopaedic surgery and offer a taper connection between stem and ball head. Taper connections are exposed to high bending loads and bear the risk of fretting and corrosion, as observed in clinical applications. This is particularly a problem for large diameter metal bearings as the negative effects may be enhanced due to the higher moments within the taper connection. Currently, it is not known how much torque is required to initiate a removal of the passive layer, which might lead to corrosion over a longer period and limits the lifetime of prostheses. Therefore, the purpose of this study was to identify the amount of torque required to start an abrasion of the passive layer within the interface dependent on the assembly force and the axial load. Materials and Methods. Titanium hip stems (Furlong H-AC, JRI, UK) and cobalt-chromium heads (⊘ 28mm, size L, JRI, UK) were assembled using a drop rig with peak forces of 4.5 kN (F. P,1. , n = 4) or 6.0 kN (F. P,2. , n = 4). The prostheses were inverted and then mounted with the head rigidly fixed to the base of a materials testing machine using a non-conducting (nylon) jig while submerged in Ringer's solution. The stems were attached to the machine actuator via non-conductive plates. An axial load (F. A,1. = 1 kN, F. A,2. = 3 kN, n = 4 each) was applied to the stems along the taper axis. After a period of equilibration a torque, increasing from 0 up to 15Nm, was manually applied. The galvanic potential at the taper interface was continuously recorded using a titanium electrode. The torque required to cause a drop in the potential of 5% was identified. For statistical analyses non-parametric tests were performed (α = 0.05). Results. Four different phases of the potential could be clearly differentiated during testing: equilibrium, removal of the passive layer leading to a drop of the potential, repassivation and then a second equilibrium. Prostheses assembled with a force of 6 kN required a significantly higher torque to start a removal of the passive layer compared to those with 4.5 kN (7.2 ± 0.5 Nm vs. 3.9 ± 1.0 Nm for F. A,1. , p = 0.029). In contrast, no influence of the axial load on the fretting behaviour of the prostheses could be found (8.0 ± 1.6 Nm for F. P,2. , p = 0.486). Discussion. Changes in the galvanic potential were observed at low torque levels for a small head diameter. With increasing head diameter the tangential force leading to a removal of the passive layer in the stem-head interface decrease resulting in a higher risk for corrosion. Component assembly with a high force reduces the risk of fretting and corrosion in the taper interface; however, it is feasible that the determined torque levels can still be reached, particularly in situations of large weight and high activity of the patient or malpositioning of the prosthesis in the body