Aim. Diagnostics of orthopedic implant infection remains challenging and often shows false negative or inadequate results. Several methods have been described to improve diagnostic methods but most of them are expensive (PCR) or not accessible for all hospitals (sonication). Aim of this study was to evaluate the results of incubation of orthopedic explants compared to biopsies and punction fluid using conventional microbiological methods. Method. In this prospective study, we included patients who received septic or aseptic orthopedic implant removal in a single University hospital between July and December 2018. A part of the explant as well as minimum 2 tissue biopsies or additional punction fluid were put in a bouillon and incubated for 11 days. Patient´s records with co-morbidities, use of antibiotics and demographic data were evaluated. The results were analyzed. The study was approved by the ethical committee. Results. 94 patients were included in this study (43 females, 51 males, mean age 54 years). We detected statistically significant more pathogens in the bouillon with explants compared to biopsies (p=0,0059). We found the same results with pedicle screws (n=11, p=0,039) and endoprosthesis (n=56, p=0,019). Patients after osteosynthesis (p=27) showed same results but statistically not significant (p=0,050). Use of antibiotics did not have influence on the diagnostic result as well as co-morbidities. In 38 patients (40,4%), additional bacteria could be detected in explant´s bouillon. Most common pathogens were Staph. aureus, E. faecalis, Staph. epidermidis and Micrococcus luteus, mixed infections could be found in 9%. Conclusions. In this study we could show that incubation of orthopedic implants has advantages in diagnostics of pathogens in infected endoprosthesis, osteosynthesis and spondylodesis. This method is simple compared to PCR or sonication and as cheap as incubation of tissue samples but in 40% of the cases, additional pathogens can be detected. We recommend to incubate removed screws, hip endoprosthetic heads or inlays in bouillon to optimize diagnostics and to detect all pathogens

Introduction: In recent years the implementation of sonication in the diagnosis of orthopaedic implant infections has improved the detection of subclinical infections. With the use of sonication of removed orthopaedic material we can detect the presence of biofilm. The method has already shown encouraging results, especially in cases of preoperative antibiotic therapy. Aim: The aim of the study was to detect infections of orthopaedic material using both sonication and standard diagnostic methods, and to compare the obtained results of both methods. For the purpose of the study we sonicated all explanted material at revision surgery and cultured the obtained samples. During revision surgery soft tissue biopsies were collected and analyzed using standard microbiologic methods. The results were compared, analyzed and additional therapy was applied, if an infection of the material was proven. During the period from September 2009 to the end of March 2014 we studied 249 cases (198 patients) of revision surgery (166 cases of revision hip arthroplasty, 53 cases of revision knee arthroplasty, 13 cases of revision foot surgery, 17 cases of revision spine surgery). Of studied cases infection was proven in 20 (8,0%) cases by soft tissue biopsies only, 90 cases (36,1%) were diagnosed both by soft tissue biopsies and sonication, 45 cases (18,1%) were diagnosed only by sonication of explanted prosthetic material and in 94 cases (37,8%) all results were negative. The statistical analysis has shown statistically significant (p<0,05) improvement of infection detection using sonication. According to our experience the implementation of sonication has shown an improvement in the diagnosis of orthopaedic implant infections. Despite certain limitations, sonication should be considered in doubtful cases of revision surgery. The use of sonication should be emphasized in cases of preoperative antibiotic treatment

Background and aim. Implant-associated osteomyelitis is one of the most feared complications following orthopedic surgery. Although the risk is low it is crucial to achieve adequate antibiotic concentrations proximate to the implant for a sufficient amount of time to protect the implant surface and ensure tissue integration. The aim of this study was to assess steady-state piperacillin concentrations in the proximity of an orthopedic implant inserted in cancellous bone. Method. Six female pigs received an intravenous bolus infusion of 4 g/0.5 g piperacillin/tazobactam over 30 min every 6 h. Steady state was assumed achieved in the third dosing interval (12–18 h). Microdialysis catheters were placed in a cannulated screw in the proximal tibial cancellous bone, in cancellous bone next to the screw, and in cancellous bone on the contralateral tibia. Dialysates were collected from time 12 to 18 h and plasma samples were collected as reference. Results. Time above the minimal inhibitory concentration (fT>MIC) was evaluated for MIC of 8 (low target) and 16 μg/mL (high target). For the low piperacillin target (8 μg/mL), comparable mean fT>MIC across all the investigated compartments (mean range: 54–74%) was found. For the high target (16 μg/mL), fT>MIC was shorter inside the cannulated screw (mean: 16%) than in the cancellous bone next to the screw and plasma (mean range: 49–54%), and similar between the two cancellous bone compartments. Conclusions. To reach more aggressive piperacillin fT>MIC targets in relation to the implant, alternative dosing regimens such as continuous infusion may be considered

Background of Study. Identification of the exact make and model of an orthopaedic implant prior to a revision surgery can be challenging depending upon the surgeon's experience and available knowledge base about the available implants. The current identification procedure is manual and time consuming as the surgeon may have to do a comprehensive search within an online database of radiographs of an implant to make a visual match. There is further time lapse in contacting that particular implant manufacturer to confirm the make and model of the implant and then order the whole inventory for the revision surgery. This leads to delay in treatment thus requiring extra hospital bed occupancy. Materials and Methods. We have analysed image recognition techniques currently in use for image recognition to understand the underlying technologies based on an interface commonly known as Application Programming interface (API). These API's specifies how the software components of the proposed application interact with each other. The objective of this study is to leverage one or a combination of API's to design a fully functional application in the initial phase and that can help recognize the implant accurately from a large database of radiographs and then develop a specialized and advanced API/Technology in the implant identification application. Results. Our study takes into account the existent technologies such as Facebook, Pictoria, Imagga, Google images. We found that there is an API currently available that can be directly applied to build an implant recognition system. However, commonly known Facebook's image tagging algorithms to store unique information with each image is the starting point to help build an intelligent system that in combination with image processing and development of a custom implant recognition API. Conclusion. There is an urgent need to have a robust and accurate system for identification of orthopaedic implants. Revision surgeries may need to be carried out by hospitals without access to index surgery operating notes. Patients may approach the most convenient not necessarily the same surgeon for a revision surgery. The dependency upon surgeon's experience, hospitals facilities and archiving of records can be avoided with the use of a single application that allows multiple manufacturers to contribute to a database of catalogue of their products

Many orthopaedic procedures require implants to be trialled before definitive implantation. Where this is required, the trials are provided in a set with the instrumentation. The most common scenario this is seen in during elective joint replacements. In Scotland (2007) the Scottish Executive (. http://www.sehd.scot.nhs.uk/cmo/CMO(2006)13.pdf. ) recommended and implemented individually packed orthopaedic implants for all orthopaedic sets. The premise for this was to reduce the risk of CJD contamination and fatigue of implants due to constant reprocessing from corrosion. During many trauma procedures determining the correct length of plate or size of implant can be challenging. Trials of trauma implants is no longer common place. Many implants are stored in closed and sealed boxes, preventing the surgeon looking at the implant prior to opening and contaminating the device. As a result many implants are incorrectly opened and either need reprocessed or destroyed due to infection control policy, thus implicating a cost to the NHS. With even the simplest implants costing several hundreds of pounds, this cost is a very significant waste in resources that could be deployed else where. My project was to develop a method to produce in department accurate, cheap and disposable trials for implants often used in trauma, where the original manufacturer do not offer the option of a trial off the shelf. The process had to not involve contaminating or destroying the original implant in the production of a trial. Several implants which are commonly used within Glasgow Royal Infirmary and do not have trials were identified. These implants were then CT scanned within their sealed and sterile packaging without contamination. Digital 3D surface renders of the models were created using free open source software (OsiriX, MeshLab, NetFabb). These models were then processed in to a suitable format for 3D printing using laser sintering via a cloud 3D printing bureau (. Shapeways.com. ). The implants were produced in polyamide PA220 material or in 316L stainless steel. These materials could be serialized using gamma irradiation or ethylene oxide gas. The steel models were suitable for autoclaving in the local CSSU. The implants produced were accurate facsimiles of the original implant with dimensions within 0.7mm. The implants were cost effective, an example being a rim mesh was reproduced in polyamide PA220 plastic for £3.50 and in 316L stainless steel for £15. The models were produced within 10 days of scanning. The stainless steel trials were durable and suitable for reprocessing and resterilisation. The production of durable, low cost and functional implant trials all completed in department was successful. The cost of production of each implant is so low that it would be offset if just one incorrect implant was opened during a single procedure. With some of the implants tested, the trials would have paid for themselves 100 times. This is a simple and cost saving technique that would help reduce department funding and aid patient care

Background

Recent advances in materials and manufacturing processes for arthroplasty have allowed fabrication of intricate implant surfaces to facilitate bony attachment. However, refinement and evaluation of these new design strategies is hindered by the cost and complications of animal studies, particularly during early iterations in development process. To address this problem, we have constructed and validated an ex-vivo bone bioreactor culture system to enable empirical testing of candidate structures and materials. In this study, we investigated mineralization of a titanium wire mesh scaffold under both static and dynamic culturing using our ex vivo bioreactor system.

Aim. Following clean (class I, not contaminated) surgical procedures, the rate of surgical site infection (SSI) should be less than approximately 2%. However, an infection rate of 12.2% has been reported following removal of orthopedic implants used for treatment of fractures below the knee. The objective of this trial was to evaluate the effect of a single dose of preoperative antibiotic prophylaxis on the incidence of SSIs following removal of orthopedic implants used for treatment of fractures below the knee. Method. This multicenter, double-blind, randomized clinical trial included 500 patients from 19 hospitals with a follow-up of 6 months. Eligible were patients aged 18 to 75 years with previous surgical treatment for fractures below the knee who were undergoing removal of orthopedic implants. Exclusion criteria were an active infection or fistula, antibiotic treatment, reimplantation of osteosynthesis material in the same session, allergy for cephalosporins, known kidney disease, immunosuppressant use, or pregnancy. The intervention was a single preoperative intravenous dose of 1000 mg of cefazolin (cefazolin group, n = 228) or sodium chloride (0.9%; saline group, n = 242). Primary outcome was SSI within 30 days as measured by the criteria from the US Centers for Disease Control and Prevention. Secondary outcome measures were functional outcome, health-related quality of life, and patient satisfaction. Results. Among 477 randomized patients (mean age, 44 years [SD, 15]; women, 274 [57%]; median time from orthopedic implant placement, 11 months [interquartile range, 7–16]), 470 patients completed the study. Sixty-six patients developed an SSI (14.0%): 30 patients (13.2%) in the cefazolin group vs 36 in the saline group (14.9%) (absolute risk difference, −1.7 [95% CI, −8.0 to 4.6], P = .60). Conclusions. In patients undergoing surgery for removal of orthopedic implants used for treatment of fractures below the knee, a single preoperative dose of intravenous cefazolin compared with placebo did not reduce the risk of surgical site infection within 30 days following implant removal

Aim. Prosthetic joint infections pose a major clinical challenge. Developing novel material surface technologies for orthopedic implants that prevent bacterial adhesion and biofilm formation is essential. Antimicrobial coatings applicable to articulating implant surfaces are limited, due to the articulation mechanics inducing wear, coating degradation, and toxic particle release. Noble metals are known for their antimicrobial activity and high mechanical strength and could be a viable coating alternative for orthopaedic implants [1]. In this study, the potential of thin platinum-based metal alloy coatings was developed, characterized, and tested on cytotoxicity and antibacterial properties. Method. Three platinum-based metal alloy coatings were sputter-coated on medical-grade polished titanium discs. The coatings were characterized using optical topography and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Ion release was measured using inductively coupled plasma optical emission spectrometry (ICP-OES). Cytotoxicity was tested according to ISO10993-5 using mouse fibroblasts (cell lines L929 and 3T3). Antibacterial surface activity, bacterial adhesion, bacterial proliferation, and biofilm formation were tested with gram-positive Staphylococcus aureus ATCC 25923 and gram-negative Escherichia coli ATCC 25922. Colony forming unit (CFU) counts, live-dead fluorescence staining, and SEM-EDS images were used to assess antibacterial activity. Results. Three different platinum-based metal alloys consisting of platinum-iridium, platinum-copper, and platinum-zirconium. The coatings were found 80 nm thick, smooth (roughness average < 60 nm), and non-toxic. The platinum-copper coating showed a CFU reduction larger than one logarithm in adherent bacteria compared to uncoated titanium. The other coatings showed a smaller reduction. This data was confirmed by SEM and live-dead fluorescence images, and accordingly, ICP-OES measurements showed low levels of metal ion release from the coatings. Conclusions. The platinum-copper coating showed low anti-adhesion properties, even with extremely low metal ions released. These platinum-based metal alloy coatings cannot be classified as antimicrobial yet. Further optimization of the coating composition to induce a higher ion release based on the galvanic principle is required and copper looks most promising as the antimicrobial compound of choice. Acknowledgments. This publication is supported by the DARTBAC project (with project number NWA.1292.19.354) of the research program NWA-ORC which is (partly) financed by the Dutch Research Council (NWO); and the AMBITION project (with project number NSP20–1-302), co-funded by the PPP Allowance made available by Health-Holland, Top Sector Life Sciences & Health to ReumaNederland

OSSTEC is a pre-spin-out venture at Imperial College London seeking industry feedback on our orthopaedic implants which maintain bone quality in the long term. Existing orthopaedic implants provide successful treatment for knee osteoarthritis, however, they cause loss of bone quality over time, leading to more dangerous and expensive revision surgeries and high implant failure rates in young patients. OSSTEC tibial implants stimulate healthy bone growth allowing simple primary revision surgery which will provide value for all stakeholders. This could allow existing orthopaedics manufacturers to capture high growth in existing and emerging markets while offering hospitals and surgeons a safer revision treatment for patients and a 35% annual saving on lifetime costs. For patients, our implant technology could mean additional years of quality life by revising patients to a primary TKA before full revision surgery. Our implants use patent-filed additive manufacturing technology to restore a healthy mechanical environment in the proximal tibia; stimulating long term bone growth. Proven benefits of this technology include increased bone formation and osseointegration, shown in an animal model, and restoration of native load transfer, shown in a human cadaveric model. This technology could help capture the large annual growth (24%) currently seen in the cementless knee reconstruction market, worth $1.2B. Furthermore, analysis suggests an additional market of currently untreated younger patients exists, worth £0.8B and growing by 18% annually. Making revision surgery and therefore treatment of younger patients easier would enable access to this market. We aim to offer improved patient treatment via B2B sales of implants to existing orthopaedic manufacturer partners, who would then provide them with instrumentation to hospitals and surgeons. Existing implant materials provide good options for patient treatments, however OSSTEC's porous titanium structures offer unique competitive advantages; combining options for modular design, cementless fixation, initial bone fixation and crucially long term bone maintenance. Speaking to surgeons across global markets shows that many surgeons are keen to pursue bone preserving surgeries and the use of porous implants. Furthermore, there is a growing demand to treat young patients (with 25% growth in patients younger than 65 over the past 10 years) and to use cementless knee treatments, where patient volume has doubled in the past 4 years and is following trends in hip treatments. Our team includes engineers and consultant surgeons who have experience developing multiple orthopaedic implants which have treated over 200,000 patients. To date we have raised £175,000 for the research and development of these implants and we hope to gain insight from industry professionals before further development towards our aim to begin trials for regulatory approval in 2026. OSSTEC implants provide a way to stimulate bone growth after surgery to reduce revision risk. We hope this could allow orthopaedic manufactures to explore high growth markets while meaning surgeons can treat younger patients in a cost effective way and add quality years to patients' lives

Aim. In the current study we aim to characterize the use of cationic host defense peptides (HDPs) as alternative antibacterial agents to include into novel antibacterial coatings for orthopedic implants. Staphyloccous aureus represent one the most challenging cause of infections to treat by traditional antibacterial therapies. Thanks to their lack of microbial resistance described so far, HDPs represent an attractive therapeutic alternative to antibiotics. Furthermore, HDPs have been showed to control infections via a dual function: direct antimicrobial activity and regulation of immune response. However, HDPs functions characterization and comparison is controversial, as changing test conditions or cell type used might yield different effects from the same peptide. Therefore, before moving towards the development of HDP-based coatings, we need to characterize and compare the immunomodulatory and antibacterial functions under the same conditions in vitro of 3 well-known cathelicidins: human LL-37, chicken CATH-2, and bovine-derived IDR-1018. Method. S. aureus, strain SH1000, was incubated with different concentrations of each HDP and bacterial growth was monitored overnight. Primary human monocytes were isolated from buffy coats using Ficoll-Paque density and CD14 microbeads, and differentiated for 7 days to macrophages. After 24h incubation in presence of LPS and HDPs, macrophages cytokines production was measured by ELISA. Macrophages cultured for 24h in presence of HDPs were infected with serum-opsonized S. aureus. 30 min and 24h after infection, bacterial phagocytosis and intracellular killing by macrophages were measured by flow cytometry and colony forming units (CFU) count respectively. Results. All HDPs efficiently inhibit macrophages LPS-mediated activation, as observed by a reduced production of TNF-α and IL-10. Despite a comparable anti-inflammatory action, only CATH-2 shows direct antibacterial properties at concentrations 10-times lower than those needed to stimulate immune cells. Although stimulation with HDPs fails to improve macrophages ability to kill intracellular S. aureus, IDR-1018 decreases the proportion of cells phagocytosing bacteria. Conclusions. In addition to a strong anti-inflammatory effect provided by all HDPs tested, CATH-2 has direct antibacterial effects while IDR-1018 reduces the proportion of macrophages infected by S. aureus. Use of these HDPs in combination with each other or with other conventional antibacterial agents could lead the way to the design of novel antibacterial coatings for orthopedic implants

Introduction. Orthopedic implants are subject to wear and release ultra-high molecular weight polyethylene (UHMWPE) debris. Analysis of UHMWPE wear particles is critical in determining the safety and effectiveness of novel orthopedic implants. Complete digestion of periprosthetic tissue and wear fluid is necessary to ensure accurate morphological and quantitative particle analysis. Acid digestion methods are more effective than enzymatic and base digestion approaches [Baxter+ 2009]. However, optimal digestion times, quantity, and type of acid are unclear for particle isolation. In addition, imaging and analysis techniques are critical to ensure accurate reporting of particle characteristics. Here, we 1) compared the efficacy of three acid-based digestion methods in isolating particles from a) bovine serum and b) animal/human tissue, and 2) analyzed the effects of imaging location on particle quantity/morphology results. Methods. 1a) UHMWPE (GUR 150) particles were generated by Mode I knee wear testing for 1 million cycles in bovine serum. Serum was digested in one of four solutions: 12.2M HCl, 15.8M HNO. 3. , a 1:1 volume ratio of HNO. 3. :HCl (aqua regia), or filtered H. 2. O (control). The serum:solution volume ratio was 1:5 [Niedzwiecki+ 2001, ISO 17853:2011]. Digestion occurred for 60min on a stir plate at 60°C. Each digest was combined with MeOH at a 1:5 digest:MeOH volume ratio and filtered using a 100 nm polycarbonate membrane. The particle-containing membranes were imaged (12 images/membrane) using scanning electron microscopy (SEM) to determine particle characteristics, including quantity, equivalent circular diameter (ECD) and aspect ratio (AR). 1b) Based on 1a, HNO. 3. was used to digest porcine and human tissue at concentrations of 1:40, 1:60, or 1:80 tissue:HNO. 3. volume ratios for either 1, 12, or 24 hours, followed by SEM analysis. 2) Particle characteristics were compared at nine locations (20 images/location) across a particle-containing membrane to determine the effects of imaging location. Results. 1a) HNO. 3. and aqua regia methods successfully digested the bovine serum, whereas the HCl and H. 2. O methods were unsuccessful (Fig.1A). Comparing HNO. 3. and aqua regia groups, particle characteristics and ECD frequency distribution were nearly identical (Fig.1B). 1b) Nitric acid did not fully digest porcine or human tissues. 2) Similar particle characteristics were observed in all nine locations analyzed across the polycarbonate membrane. The particle quantity, ECD, and AR for a representative center vs. intermediate location were 808 vs. 780 particles, 0.33±0.28 vs. 0.35±0.29 µm, and 1.57±0.56 vs. 1.51±0.4, respectively (Fig.2). Conclusions. Nitric acid and aqua regia are capable of digesting bovine serum using low quantities of acid for short duration, allowing precise analysis of UHMWPE particle debris from orthopedic implants. However, further optimization of digestion techniques for animal/human tissue is warranted. In addition, an accurate representation of particle distribution can be achieved without analyzing hundreds of images, because membrane location does not strongly influence particle results. Finally, ASTM F1877-16 – Standard Practice for Characterization of Particles – could benefit from adding software-based automated particle characterization as an optional method. An automated approach that uses k-means clustering image segmentation to identify particles and computer vision tools to extract relevant morphological features is under development and validation

Aim. Orthopedic implant related surgical site infection (SSI) is a severe complication which represents an important challenge concerning to its treatment. Therefore, gram-negative orthopedic infections have recently become a global concern. Method. Retrospective study through searching of the SCIH (infection control service) database, concerning to the year 2016 and 2017. Cases selected were those of implant placement clean surgeries (osteosynthesis or prosthetic placement) which evolved with SSI and Gram-negative bacterial growth in bone tissue or periprosthetic cultures. Results. During 2016 and 2017, 6150 clean surgeries with orthopedic implant placement were performed; 140 fulfilled SSI criteria (83 cases of open fracture reduction, 44 of hip arthroplasty, 13 of knee arthroplasty). Main agent of infections was Staphylococcus aureus (32,47%) mostly of them methicillin-sensitive (69,20%). However, Gram-negative bacteria were responsible for 64,95% of infections. (Klebsiella pneumoniae 12.8%; Acinetobacter baumannii and Enterobacter ssp 11.96%; Pseudomonas aeruginosa 9.40%) Among them, 100% Enterobacter ssp. were sensitive to carbapenems and 75% to ciprofloxacin. Klebsiella pneumoniae showed sensitivity to carbapenems in 85.7%, Pseudomonas aeruginosa showed sensitivity in 85.7% to carbapenems and 100% to ciprofloxacin. Acinetobacter baumannii showed the least favorable profile amongst Gram-negatives since only 12.5% of strains were sensitive to carbapenems, 28.6% to Ampicilin-sulbactam, 22.2% to ciprofloxacin, while showing 100% sensitivity to polymyxins. 14 patients in whom Acinetobacter baumannii was isolated were predominantly elderly (median 70 years), most of them have underlying/chronic diseases (71.42%) such as diabetes, arterial hypertension, alcoholism, smoking and heart failure. None presented sepsis related to this infection, but four of them died as result of hospitalization related complications (28,60% mortality rate). Among these deaths, 3 were related to total hip arthroplasty, and one to knee arthroplasty. One patient died as result of external causes. Among the survivors, five showed remission/cure. The follow up was lost in 4 patients. Conclusions. SSI caused by carbepenem-resistant Acinetobacter baumannii represents considerable impact on morbi-mortality in patients who undergo surgery with placement of orthopedic implants

The evolution of orthopedic implants has witnessed a great evolution and allowed insights into the various metals and alloys compatible with the human body. However, some recent reports have raised concerns regarding hypersensitivity to several metals used in orthopedic implants. These cases are mostly documented in the field of arthroplasty. Metal ion release following hip or knee arthroplasty is a known phenomenon and associated immune reactions to these metal ions have been implicated in the causation of these hypersensitivity reactions. These reactions frequently lead to poor outcome following these implant surgeries. We here present two rare cases of metal induced hypersensitivity reactions following orthopedic surgeries. We have also reviewed the literature in this context to look into the various causes of metal reactions, types of implant involved in hypersensitivity, methods of testing and management options in these cases

Ti-6Al-4V is the most common alloy used for orthopaedic implants. Its popularity is due to low density, superior corrosion resistance, good osseointegration and lower elastic modulus when compared to other commonly used alloys such as CoCrMo and stainless steel. In fact, the use of Ti64 has even further increased lately since recent controversy around adverse local tissue reactions and implant failure related to taper corrosion of CoCrMo alloy. However, implants made from Ti64 can fail in some cases due to fatigue fracture, sometimes related to oxide induced stress corrosion cracking or hydrogen embrittlement, or preferential corrosion of the beta phase. Studies performed with Ti-6Al-4V do often not consider that the alloy itself may have a range of characteristics that can vary and could significantly impact the implant properties. These variations are related to the material microstructure which depends not only on chemical composition, but also the manufacturing process and subsequent heat treatments. Different microstructures can occur in implants made form wrought alloys, cast alloys, and more recently, additive manufactured (AM) alloys. Implant alloy microstructure drives mechanical and electrochemical properties. Therefore, this study aims to analyse the microstructure of Ti-6Al-4V alloy of additive manufactured and conventional retrieved orthopaedic implants such as acetabular cups, tibial trays, femoral stem and modular neck by means of electron backscatter diffraction (EBSD). Microstructural features of interest include grains shape and size, phase content and distribution, preferred grain orientation (texture), alloying elements distribution (homogenization) and presence of impurities. Additionally, we demonstrate the direct impact of different microstructural features on hardness. We analysed 17 conventional devices from 6 different manufacturers, 3 additive manufactured devices from 2 different manufactures and 1 control alloy (bar stock). The preliminary results showed that even though all implants have the same chemical composition, their microstructural characteristics vary broadly. Ti64 microstructure of conventional alloys could be categorized in 3 groups: equiaxed grains alloys (Fine and Coarse), bimodal alloys and dendritic alloys. The additive manufactured implants were classified in an additional group on its own which consists of a needle-like microstructures - similar to Widmanstätten patterns, Fig. 1, with a network of β phase along α phase grains. Furthermore, AM alloys exhibited residual grain boundaries from the original β grains from the early stage of the solidification process, Fig. 2. These characteristics may have implication on the fatigue and corrosion behaviour. In addition, it we observed inhomogeneous alloying element distribution in some cases, Fig. 3, especially for the additive manufactured alloys, which also may have consequences on corrosion behaviour. Finally, the hardness testing revealed that the implants with large grain size, such as AM alloys, exhibit low hardness values, as expected, but also the amount of beta phase correlated positively with lower hardness. Grain aspect ratio and beta phase grain size correlated positively with higher hardness. In summary, we found that common Ti64 implants can exhibit a broad variety of different alloy microstructures and the advent of AM alloys introduces an entirely new category. It is imperative to determine the ideal microstructure for specific applications

Titanium (Ti) is well known in orthopedic implant materials such as total hip replacement arthroplasty. Osseointegration of orthopedic implants is defined as the formation of a direct interface between the implant and the bone without intervening soft tissue. Unmodified Ti is not sufficient to complete adhesion between Ti surface and host bone with subsequent implant loosening over time and ultimately implant failure. An effective approach to enhance the biological activity of orthopedic implants and improve post-implantation healing is to modify the implant surface. The aim of this study was to investigate the effect of functionalized titanium (Ti) with alendronate (Aln) and bone morphogenic protein-2 (BMP-2) for enhancement of osteoblast activity in vitro. Aln and/or BMP-2 were sequentially immobilized to the heparinized-Ti (Hep-Ti) surface. The compositions of pristine Ti and Hep-Ti with or without Aln and/or BMP-2 were characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). Osteoblast activities on all Ti substrates were investigated by cell proliferation assays, alkaline phosphate (ALP) activity, calcium deposition, gene expressions of osteocalcin and osteopontin. The modified Ti surface with heparin, Aln, BMP-2 and Aln/BMP-2 showed similar morphologies compared to that of pristine Ti on scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). Aln or BMP-2 from Aln/Hep-Ti, BMP-2/Hep-Ti or Aln/BMP-2/ Hep-Ti substrates exhibited sustained release profiles up to 4 weeks. No significant cytotoxic effects were observed for incubation periods for up to 48 h. the ALP activity of MG-63 cells cultured on Hep-Ti was not significantly different compared to those cultured on pristine Ti for 7, 14, and 21 days. Alkaline phosphatase(ALP) activities of osteoblasts cultured on Ti groups immobilized with Aln, BMP-2, or Aln/BMP-2 were significantly increased when compared to pristine Ti(p < 0.05). Calcium deposition was markedly increased in Aln/BMP-2/Hep-Ti compared to Aln/Hep-Ti or BMP-2/Hep-Ti, respectively (p < 0.05). mRNA expressions of osteocalcin(OCN) and osteopontin(OPN) of osteoblasts grown on Aln/Hep-Ti, BMP-2/Hep-Ti, and Aln/BMP-2/Hep-Ti were significantly higher than of those grown on pristine Ti (p < 0.05). Based on the results of the in vitro studies, we showed that co-delivery of alendronate and BMP-2 had an additive effect on osteoblast activity and mineralization when compared with pristine Ti as well as alendronate or BMP-2 alone. Functionalized Ti systems with alendronate and BMP-2 can give a good solution to solve the most common problems associated with orthopedic and dental implants. Furthermore, in vivo studies required to determine the optimal doses of alendronate and BMP-2 for clinical application

Biodegradable metals as orthopaedic implant materials receive substantial scientific and clinical interest. Marketed cardiovascular products confirm good biocompatibility of iron. Solid iron biodegrades slowly in vivo and has got supra-physiological mechanical properties as compared to bone and porous implants can be optimized for specific orthopaedic applications. We used Direct Metal Printing (DMP)3 to additively manufacture (AM) scaffolds of pure iron with fine-tuned bone-mimetic mechanical properties and improved degradation behavior to characterize their biocompatibility under static and dynamic 3D culture conditions using a spectrum of different cell types. Atomized iron powder was used to manufacture scaffolds with a repetitive diamond unit cell design on a ProX DMP 320 (Layerwise/3D Systems, Belgium). Mechanical characterization (Instron machine with a 10kN load cell, ISO 13314: 2011), degradation behavior under static and dynamic conditions (37ºC, 5% CO2 and 20% O2) for up of 28 days, with μCT as well as SEM/energy-dispersive X-ray spectroscopy (EDS) (SEM, JSM-IT100, JEOL) monitoring under in vivo-like conditions. Biocompatibility was comprehensively evaluated using a broader spectrum of human cells according to ISO 10993 guidelines, with topographically identical titanium (Ti-6Al-4V, Ti64) specimen as reference. Cytotoxicity was analyzed by two-way ANOVA and post-hoc Tukey's multiple comparisons test (α = 0.05). By μCT, as-built strut size (420 ± 4 μm) and porosity of 64% ± 0.2% were compared to design values (400 μm and 67%, respectively). After 28 days of biodegradation scaffolds showed a 3.1% weight reduction after cleaning, while pH-values of simulated body fluids (r-SBF) increased from 7.4 to 7.8. Mechanical properties of scaffolds (E = 1600–1800 MPa) were still within the range for trabecular bone, then. At all tested time points, close to 100% biocompatibility was shown with identically designed titanium (Ti64) controls (level 0 cytotoxicity). Iron scaffolds revealed a similar cytotoxicity with L929 cells throughout the study, but MG-63 or HUVEC cells revealed a reduced viability of 75% and 60%, respectively, already after 24h and a further decreased survival rate of 50% and 35% after 72h. Static and dynamic cultures revealed different and cell type-specific cytotoxicity profiles. Quantitative assays were confirmed by semi-quantitative cell staining in direct contact to iron and morphological differences were evident in comparison to Ti64 controls. This first report confirms that DMP allows accurate control of interconnectivity and topology of iron scaffold structures. While microstructure and chemical composition influence degradation behavior - so does topology and environmental in vitro conditions during degradation. While porous magnesium corrodes too fast to keep pace with bone remodeling rates, our porous and micro-structured design just holds tremendous potential to optimize the degradation speed of iron for application-specific orthopaedic implants. Surprisingly, the biological evaluation of pure iron scaffolds appears to largely depend on the culture model and cell type. Pure iron may not yet be an ideal surface for osteoblast- or endothelial-like cells in static cultures. We are currently studying appropriate coatings and in vivo-like dynamic culture systems to better predict in vivo biocompatibility

Introduction: The mechanobiology and response of bone formation to strain under physiological loading is well established, however investigation into exceedingly soft scaffolds relative to cancellous bone is limited. In this study we designed and 3D printed mechanically-optimised low-stiffness implants, targeting specific strain ranges inducing bone formation and assessed their biological performance in a pre-clinical in vivo load-bearing tibial tuberosity advancement (TTA) model. The TTA model provides an attractive pre-clinical framework to investigate implant osseointegration within an uneven loading environment due to the dominating patellar tendon force. A knee finite element model from ovine CT data was developed to determine physiological target strains from simulated TTA surgery. We 3D printed low-stiffness Ti wedge osteotomy implants with homogeneous stiffness of 0.8 GPa (Ti1), 0.6 GPa (Ti2) and a locally-optimised design with a 0.3 GPa cortex and soft 0.1 GPa core (Ti3), for implantation in a 12-week ovine tibial advancement osteotomy (9mm). We quantitatively assessed bone fusion, bone area, mineral apposition rate and bone formation rate. Optimised Ti3 implants exhibited evenly high strains throughout, despite uneven wedge osteotomy loading. We demonstrated that higher strains above 3.75%, led to greater bone formation. Histomorphometry showed uniform bone ingrowthin optimised Ti3 compared to homogeneous designs (Ti1 and Ti2), and greater bone-implant contact. The greatest bone formation scores were seen in Ti3, followed by Ti2 and Ti1. Results from our study indicate lower stiffness and higher strain ranges than normally achieved in Ti scaffolds stimulate early bone formation. By accounting for loading environments through rational design, implants can be optimised to improve uniform osseointegration. Design and 3D printing of exceedingly soft titanium orthopaedic implants enhance strain induced bone formation and have significant importance in future implant design for knee, hip arthroplasty and treatment of large load-bearing bone defects

Aim. Orthopedic implants play a tremendous role in fixing bone damages due to aging as well as fractures. However, these implants tend to get colonized by bacteria on the surface, leading to infections and subsequently prevention of healing and osteointegration. Recently, Roupie et al. showed that a nisin layer-by-layer based coating applied on biomaterials has both osteogenic and antibacterial properties. The Galleria mellonella larva is a well-known insect infection model that has been used to test the virulence of bacterial and fungal strains as well as for the high throughput screening of antimicrobial compounds against infections. Recently, we have developed an insect infection model with G. mellonella larvae to study implant-associated biofilm infections using Kirschner (K)-wires as implant material. Here, we would like to test the antibacterial capacity of nisin layer-by-layer based coatings on K-wires against Staphylococcus aureus in the G. mellonella larva implant infection model. Method. Prior to the implantation procedure, G. mellonella larvae are maintained at room temperature on wheat germ in an incubator. The larvae received bare titanium K-wires (uncoated), or either control-coated or nisin-coated K-wires. After one hour, the larvae were injected with 5×10. 5. S. aureus bacteria per larva (i.e., hematogenous implant infection model). Next, the larvae were incubated at 37. o. C in an incubator and the survival of the larvae was monitored for five days. Moreover, the number of bacteria on the implant surface and in the surrounding tissue was determined after 24h of incubation. Further, scanning electron microscopy (SEM) analyses were performed to study the effect of nisin on biofilm formation. Results. The larvae receiving the nisin-coated K-wires showed significantly higher survival rates compared to uncoated titanium K-wires, although not when compared to control-coated K-wires. A more than 1-log reduction in number of bacteria on the implant surface and in the surrounding tissue was observed in larvae receiving the nisin-coated K-wires, when compared to uncoated titanium K-wires SEM analysis showed reduced colonization of the bacteria nisin-coated K-wires compared to the controls. Conclusions. In conclusion, the antimicrobial nisin layer-by-layer based coating applied on titanium surfaces is able to prevent implant-related S. aureus biofilm infection in G. mellonella and is a promising antimicrobial strategy to prevent implant-related infections

Aim. The use of medical devices has grown significantly over the last decades, and has become a major part of modern medicine and our daily life. Infection of implanted medical devices (biomaterials), like titanium orthopaedic implants, can have disastrous consequences, including removal of the device. For still not well understood reasons, the presence of a foreign body strongly increases susceptibility to infection. These so-called biomaterial-associated infections (BAI) are mainly caused by Staphylococcus aureus and Staphylococcus epidermidis. Formation of biofilms on the biomaterial surface is generally considered the main reason for these persistent infections, although bacteria may also enter the surrounding tissue and become internalized within host cells. To prevent biofilm formation using a non-antibiotic based strategy, we aimed to develop a novel permanently fixed antimicrobial coating for titanium devices based on stable immobilized quaternary ammonium compounds (QACs). Method. Medical grade titanium implants (10×4×1 mm) were dip-coated in a solution of 10% (w/v) hyperbranched polymer, subsequently in a solution of 30% (w/v) polyethyleneimine and 10 mM sodium iodide, using a dip-coater, followed by a washing step for 10 min in ethanol. The QAC-coating was characterized using water contact angle measurements, scanning electron microscopy, FTIR, AFM and XPS. The antimicrobial activity of the coating was evaluated against S. aureus strain JAR060131 and S. epidermidis strain ATCC 12228 using the JIS Z 2801:2000 surface microbicidal assay. Lastly, we assessed the in vivo antimicrobial activity in a mouse subcutaneous implant infection model with S. aureus administered locally on the QAC-coated implants prior to implantation to mimic contamination during surgery. Results. Detailed material characterization of the titanium samples showed the presence of a homogenous and stable coating layer at the titanium surface. Moreover, the coating successfully killed S. aureus and S. epidermidis in vitro. The QAC-coating strongly reduced S. aureus colonization of the implant surface as well as of the surrounding tissue, with no apparent macroscopic signs of toxicity or inflammation in the peri-implant tissue at 1 and 4 days after implantation. Conclusions. An antimicrobial coating with stable quaternary ammonium compounds on titanium has been developed which holds promise to prevent BAI. Non-antibiotic-based antimicrobial coatings have great significance in guiding the design of novel antimicrobial coatings in the present, post-antibiotic era

Aims. Delayed postoperative inoculation of orthopaedic implants with persistent wound drainage or bacterial seeding of a haematoma can result in periprosthetic joint infection (PJI). The aim of this in vivo study was to compare the efficacy of vancomycin powder with vancomycin-eluting calcium sulphate beads in preventing PJI due to delayed inoculation. Methods. A mouse model of PJI of the knee was used. Mice were randomized into groups with intervention at the time of surgery (postoperative day (POD) 0): a sterile control (SC; n = 6); infected control (IC; n = 15); systemic vancomycin (SV; n = 9); vancomycin powder (VP; n = 21); and vancomycin bead (VB; n = 19) groups. Delayed inoculation was introduced during an arthrotomy on POD 7 with 1 × 10. 5. colony-forming units (CFUs) of a bioluminescent strain of Staphylococcus aureus. The bacterial burden was monitored using bioluminescence in vivo. All mice were killed on POD 21. Implants and soft-tissue were harvested and sonicated for analysis of the CFUs. Results. The mean in vivo bioluminescence in the VB group was significantly lower on POD 8 and POD 10 compared with the other groups. There was a significant 1.3-log. 10. (95%) and 1.5-log. 10. (97%) reduction in mean soft-tissue CFUs in the VB group compared with the VP and IC groups (3.6 × 10. 3. vs 7.0 × 10. 4. ; p = 0.022; 3.6 × 10. 3. vs 1.0 × 10. 5. ; p = 0.007, respectively) at POD 21. There was a significant 1.6-log. 10. (98%) reduction in mean implant CFUs in the VB group compared with the IC group (1.3 × 10. 0. vs 4.7 × 10. 1. , respectively; p = 0.038). Combined soft-tissue and implant infection was prevented in 10 of 19 mice (53%) in the VB group as opposed to 5 of 21 (24%) in the VP group, 3 of 15 (20%) in the IC group, and 0% in the SV group. Conclusion. In our in vivo mouse model, antibiotic-releasing calcium sulphate beads appeared to outperform vancomycin powder alone in lowering the bacterial burden and preventing soft-tissue and implant infections. Cite this article: Bone Joint J 2024;106-B(6):632–638