Introduction. Gram-negative prosthetic joint infections (GN-PJI) present unique challenges in management due to their distinct pathogenesis of biofilm formation on implant surfaces. The purpose of this study is to establish a clinically representative GN-PJI model that can reliably recapitulate biofilm formation on titanium implant surface in vivo. We hypothesized that biofilm formation on an implant surface will affect its ability to osseointegrate. Methods. The model was developed using 3D-printed titanium hip implants, to replace the femoral head of male Sprague-Dawley rats. GN-PJI was induced using two bioluminescent Pseudomonas aeruginosa strains: a reference strain (PA14-lux) and a mutant biofilm-defective strain (ΔflgK-lux). Infection was monitored in real-time using the in vivo imaging system (IVIS) and Magnetic Resonance Imaging (MRI). Bacterial loads on implant surface and in periprosthetic tissues were quantified utilizing viable-colony-count. Field-emission scanning-electron-microscopy of the explanted implants was used to visualize the biofilm formation at the bone-implant-interface. The implant stability, as an outcome, was directly assessed by quantifying the osseointegration in vitro using microCT scan, and indirectly assessed by identifying the gait pattern changes using DigiGait. TM. system in vivo. Results. Localized infection was established within the hip joint and was followed by IVIS in real-time. There was a quantitative and qualitative difference in the bacterial load and biofilm formation between PA14-lux and ΔflgK-lux. This difference in the ability to persist in the model between the two strains was reflected in the gait pattern and implant osseointegration. Conclusions. We developed a novel uncemented hip hemiarthroplasty, GN-PJI rat model. To date, the proposed in vivo biofilm-based model is the most clinically representative for GN-PJI since animals can bear weight on the implant and poor osseointegration correlates with biofilm formation. In addition, localized PJI was detected by various modalities. Clinical Relevance. The proposed in vivo GN-PJI model will allow for more reliable testing of novel biofilm-targeting therapeutics

Gram-negative prosthetic joint infections (GN-PJI) present unique challenges in management due to their distinct pathogenesis of biofilm formation on implant surfaces. To date, there are no animal models that can fully recapitulate how a biofilm is challenged in vivo in the setting of GN-PJI. The purpose of this study is to establish a clinically representative GN-PJI in vivo model that can reliably depict biofilm formation on titanium implant surface. We hypothesized that the biofilm formation on the implant surface would affect the ability of the implant to be osseointegrated. The model was developed using a 3D-printed, medical-grade titanium (Ti-6Al-4V), monoblock, cementless hemiarthroplasty hip implant. This implant was used to replace the femoral head of a Sprague-Dawley rat using a posterior surgical approach. To induce PJI, two bioluminescent Pseudomonas aeruginosa (PA) strains were utilized: a reference strain (PA14-lux) and a mutant strain that is defective in biofilm formation (DflgK-lux). PJI development and biofilm formation was quantitatively assessed in vivo using the in vivo imaging system (IVIS), and in vitro using the viable colony count of the bacterial load on implant surface. Magnetic Resonance Imaging (MRI) was acquired to assess the involvement of periprosthetic tissue in vivo, and the field emission scanning electron microscopy (FE-SEM) of the explanted implants was used to visualize the biofilm formation at the bone-implant interface. The implant stability, as an outcome, was directly assessed by quantifying the osseointegration using microCT scans of the extracted femurs with retained implants in vitro, and indirectly assessed by identifying the gait pattern changes using DigiGaitTM system in vivo. A localized prosthetic infection was reliably established within the hip joint and was followed by IVIS in real-time. There was a quantitative and qualitative difference in the bacterial load and biofilm formation between PA14 and DflgK. This difference in the ability to persist in the model between the two strains was reflected on the gait pattern and implant osseointegration. We developed a novel uncemented hip hemiarthroplasty GN-PJI rat model. This model is clinically representative since animals can bear weight on the implant. PJI was detected by various modalities. In addition, biofilm formation correlated with implant function and stability. In conclusion, the proposed in vivo GN-PJI model will allow for more reliable testing of novel biofilm-targeting therapetics

This study aimed to analyze the effect of two different techniques of cement application: cement on bone surface (CoB) versus cement on bone surface and implant surface (CoBaI) on the short-term effect of radiolucent lines (RLL) in primary fully cemented total knee arthroplasties (TKA) with patella resurfacing. 379 fully cemented TKAs (318 patients) were included in this monocentric study. Preoperative and postoperative at week 4 and 12 month after surgery all patients had a clinical and radiological examination and were administered the Oxford Knee Score (OKS). Cement was applied in two different ways among the two study groups: cement on bone surface (CoB group) or cement on bone surface and implant surface (CoBaI group). The evaluation of the presence of RLL or osteolysis was done as previously described using the updated Knee Society Radiographic Evaluation System. The mean OKS and range of motion improved significantly in both groups at the 4-week and 12-month follow-up, with no significant difference between the groups (CoB vs. CoBaI). RLL were present in 4.7% in the whole study population and were significantly higher in the CoBaI group (10.5%) at the 4-week follow-up. At the 12-month follow-up RLL were seen in 29.8% of the TKAs in the CoBaI group, whereas the incidence was lower in the CoB group (24.0% (n.s.)). There were two revisions in each group. None of these due to aseptic loosening. Our study indicated that the application of bone cement on bone surface only might be more beneficial than onto the bone surface and onto the implant surface as well in respect to the short-term presence of RLL in fully cemented primary TKA. The long-term results will be of interest, especially in respect to aseptic loosening and might guide future directions of bone cement applications in TKA

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

Periprosthetic joint infections (PJIs) and osteosynthesis-associated infections (OSIs) present significant challenges in trauma and orthopaedic surgery, substantially impacting patient morbidity, mortality, and economic burden. This concern is heightened in patients with pre-existing comorbidities, such as diabetes mellitus, which are not always modifiable at presentation. A novel intraoperative strategy to prevent these infections is the use of Defensive Antibacterial Coating (DAC), a bio-absorbable antibiotic-containing hydrogel applied to implant surfaces at implantation, acting as a physical barrier to prevent infection. The purpose of this study is to assess the use of a commercially available hydrogel (DAC), highlighting its characteristics that make it suitable for managing PJIs and OSIs in orthopaedics and traumatology. Twenty-five patients who underwent complex orthopaedic procedures with intraoperative application of DAC between March 2022 and April 2023 at a single hospital site were included. Post-operative assessment encompassed clinical, laboratory, and radiographic examinations. In this study, 25 patients were included, with a mean age of 70 ± 14.77 years and an average ASA grade of 2.46 ± 0.78. The cohort presented an average Charleston Comorbidity score of 5.45 ± 2.24. The procedures included 8 periprosthetic fractures, 8 foot and ankle surgeries, 5 upper limb surgeries, and 4 elective hip and knee surgeries. Follow-up assessments at 6 weeks and 6 months revealed no evidence of PJI or OSI in any patients, nor were any treatments for PJI or OSI required during the interim period. DAC demonstrated efficacy in preventing infections in high-risk patients undergoing complex orthopaedic procedures. Our findings warrant further investigation into the use of DAC in complex hosts with randomized control trials

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

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

Aim. Fungal periprosthetic joint infections are difficult to treat and often associated with a limited outcome for patients. Candida species account for approximately 90% of all fungal infections. In vivo biofilm models play major role to study biofilm development, morphology, and regulatory molecules for bacteria. However, in vivo modeling of biofilm-associated fungi models are very rare. Furthermore, due to ethical restrictions, mammalian models are replaced with other alternative models in basic research. Recently, we have developed insect infection model G. mellonella larvae to study implant associated biofilm infections with bacteria. This model organism was not used for fungi biofilm infection yet. Thus, we aimed to establish G. mellonella as in vivo model to study fungal implant infections using Candida albicans as model organism and to test anti-fungal medication. Method. Titanium and Stainless steel K-wires were cut into small pieces with size of 4mm. For the infection process, implants were pre-incubated in specified fungal growth culture Candida albicans at 1×10. 7. CFU/ml for 30 min at 150 rpm shaking conditions. Later, these implants were washed with 10ml PBS and implanted in the larvae as mentioned. To analyze the susceptibility of the implant-associated fungal infections towards anti fungal compounds, the larvae were treated with amphotericin B, fluconazole and voriconazole after 24h of implantation. The effect of anti-fungal compounds was measured in terms of survival observation for 5 days and fungal load in larvae on 2. nd. day. To reveal the fungal biofilm formation on implant, the implants were removed on day 3 and processed for SEM analysis. Results. Pre-incubated K-wire caused the Candida infection and observed the death of the larvae. The treatment with antifungal compounds recovered the larvae from the implant-infection, except in case of Voriconazole. However, the recovery with treatment of anti fungal compounds was not effective as the larvae with planktonic infection, which highlights typical biofilm phenotype. Further, the treatment with anti-fungal compounds with Amphotericin B and Fluconazole reduced the fungal load in larvae tissue. The SEM analysis revealed the formation fungal biofilm with hyphae and spores associated with larvae tissue on implant surface. Conclusions. The results from survival analysis, antifungal treatment and SEM analysis are very promising to use of G. mellonella as in vivo model to study fungal infections on implanted materials. Our study highlights the use of G. mellonella larvae as alternative in vivo model to study implant-associated fungal infections that reduces the use of the higher mammals

Title. Longitudinal Intravital Imaging to Quantify the “Race for the Surface” Between Host Immune Cell and Bacteria for Orthopaedic Implants with S. aureus Colonization in a Murine Model. Aim. To assess S. aureus vs. host cell colonization of contaminated implants vis intravital multiphoton laser scanning microscopy (IV-MLSM) in a murine model. Method. All animal experiments were approved by IACUC. A flat stainless steel or titanium L-shaped pin was contaminated with 10. 5. CFU of a red fluorescent protein (RFP) expressing strain of USA300LAC, and surgically implanted through the femur of global GFP-transgenic mice. IV-MLSM was performed at 2, 4, and 6 hours post-op. Parallel cross-sectional CFU studies were performed to quantify the bacteria load on the implant at 2,4,6,12,18 and 24 hours. Results. 1) We developed a high-fidelity reproducible IV-MLSM system to quantify S. aureus and host cell colonization of a bone implant in the mouse femur. Proper placement of all implants were confirmed with in vivo X-rays, and ex vivo photos. We empirically derive the ROI during each imaging session by aggregating the imaged volume which ranges from (636.4um × 636.4um × 151um) = 0.625 +/- 0.014 mm. 3. of bone marrow in a global GFP-transgenic mouse. 2) IV-MLSM imaging acquisition of the “race for the surface”.In vitro MPLSM images of implants partially coated with USA300LAC (RFP-MRSA) were verified by SEM image. Results from IV-MLSM of RFP-MRSA and GFP. +. host cell colonization of the contaminated implants illustrated the mutually exclusive surface coating at 3hrs, which to our knowledge is the first demonstration of “the race for the surface” between bacteria and host cells via intravital microscopy. 3) Quantifying the “race for the surface” with CFU verification of S. aureus on the implant. 3D volumetric rendering of the GFP. +. voxels and RFP+ voxels within the ROI were generated in Imaris. The voxel numbers suggeste that the fight for the surface concludes ∼3hrs post-infection, and then transitions to an aggressive MRSA proliferation phase. The results of WT control demonstrate a significant increase in CFU by 12hrs post-op for both stainless steel (P<0.01) and titanium (P<0.01). Conclusions. We developed IV-MLSM to quantify the “Race for the Surface” between host cells and contaminating S. aureus in a murine femur implant model. This race is remarkably fast, as the implant surface is completely covered with 3hrs, peak bacterial growth on the implant occurs between 2 and 12 hours and is complete by 12hrs

Background. Artificial total knee designs have revolutionized over time, yet 20% of the population still report dissatisfaction. The standard implants fail to replicate native knee kinematic functionality due to mismatch of condylar surfaces and non-anatomically placed implantation. (Daggett et al 2016; Saigo et al 2017). It is essential that the implant surface matches the native knee to prevent Instability and soft tissue impingement. Our goal is to use computational modeling to determine the ideal shapes and orientations of anatomically-shaped components and test the accuracy of fit of component surfaces. Methods. One hundred MRI scans of knees with early osteoarthritis were obtained from the NIH Osteoarthritis Initiative, converted into 3D meshes, and aligned via an anatomic coordinate system algorithm. Geomagic Design X software was used to determine the average anterior-posterior (AP) length. Each knee was then scaled in three dimensions to match the average AP length. Geomagic's least-squares algorithm was used to create an average surface model. This method was validated by generating a statistical shaped model using principal component analysis (PCA) to compare to the least square's method. The averaged knee surface was used to design component system sizing schemes of 1, 3, 5, and 7 (fig 1). A further fifty arthritic knees were modeled to test the accuracy of fit for all component sizing schemes. Standard deviation maps were created using Geomagic to analyze the error of fit of the implant surface compared to the native femur surface. Results. The average shape model derived from Principal Component Analysis had a discrepancy of 0.01mm and a standard deviation of 0.05mm when compared to Geomagic least squares. The bearing surfaces showed a very close fit within both models with minimal errors at the sides of the epicondylar line (fig 2). The surface components were lined up posteriorly and distally on the 50 femurs. Statistical Analysis of the mesh deviation maps between the femoral condylar surface and the components showed a decrease in deviation with a larger number of sizes reducing from 1.5 mm for a 1-size system to 0.88 mm for a 7-size system (table 1). The femoral components of a 5 or 7-size system showed the best fit less than 1mm. The main mismatch was on the superior patella flange, with maximum projection or undercut of 2 millimeters. Discussion and Conclusion. The study showed an approach to total knee design and technique for a more accurate reproduction of a normal knee. A 5 to 7 size system was sufficient, but with two widths for each size to avoid overhang. Components based on the average anatomic shapes were an accurate fit on the bearing surfaces, but surgery to 1-millimeter accuracy was needed. The results showed that an accurate match of the femoral bearing surfaces could be achieved to better than 1 millimeter if the component geometry was based on that of the average femur. For any figures or tables, please contact the authors directly

Aim. The aim of this study was to establish an implant-associated osteomyelitis model in rats with the ability to quantify biofilm formation on implants for prospective evaluation of antibacterial effects on micro-structured implant surfaces. Method. Staphylococcus aureus (strain 36/07) suspension with infection concentrations of 106, 105, 104 and 10. 3. CFU/10µl, respectively was injected in the tibia of 32 rats (n=8 per group). Afterwards a titanium implant (0.8×0.8×12 mm) was inserted. 8 rats were implanted with a preincubated implant (107 CFU/ml, 12 h) and 8 rats served as a control (injection of 0.9% NaCl). During the follow up, clinical, radiographic and µ-CT examinations were conducted. On day 21 post op, all rats were sacrificed. Implant and tibia were explanted under sterile conditions. The implant was stained with green and red fluorescent nucleic acid dye (live/ dead) and analyzed by confocal microscopy. The amount of vivid and dead biomass as well as vivid bacteria on the implant surface was calculated with an image software*. Results. In all groups with artificial infection, local bacterial colonization could be detected without systemic infection. While clinical signs of infections (lameness, subcutaneous abscesses) decreased, the volume of bacterial colonization increased on the implant surface with decreasing initial infection CFU. Preincubated implants showed a similar bacterial colonialization of the surface as implants which were infected with 106 CFU as well as a similar bone disintegration due to ongoing osteomyelitis. Conclusions. Establishment of the implant-associated infection model in rats with subsequent quantification of the vivid bacterial volume via confocal microscopy was successful and is now applicable for the evaluation of micro-structured antibacterial implant surfaces. Pre incubation of implants with initiating biofilm formation was established as alternative onset of infection. This work was part of BIOFABRICATION for NIFE and funded by Volkswagen Foundation and MWK. * Imaris® ×64 6.2.1

Introduction. The accumulation of proteins and bacteria on implant surfaces is a critical concern in the biomedical field, especially with respect to the potential of biofilm formation on implant surfaces. Material surface wettability is often used as a predictor of potential colonization of specific bacterial strains. Surface roughness has also been shown to have a strong relationship with biofilm formation, as rougher surfaces tend to have a stronger affinity to harbor bacterial colonies. The modification of implant surfaces to impart a biofilm resistant layer can come at the expense of increasing surface roughness however, and it is therefore important to determine how the variables of wettability and roughness are affected by any new surface coating technologies. In the current work, a novel CoBlast (C) process that impregnates alumina (A) at 50 μm grit (5) or 90 μm grit (9) sizes, with the possible addition of polytetrafluoroethylene (P) onto titanium surfaces, combined with a plasma coating process called BioDep, that coats the surface with chitosan (X) with the possible addition of vancomycin (V), were evaluated for wettability and surface roughness to determine their potential as biofilm resistant treatments on implants. Materials and Methods. N=65 titanium alloy samples (n=5 for 13 sample modification types as described above and in the figure legends below) were analyzed for surface roughness and wettability. Following cleaning in ethanol, roughness testing (Ra, Rq, Rt and Rz, Wyko NT-2000 optical profilometer @ 28.7× magnification, FOV of 164×215 μm) at 5 different surface locations per specimen, and contact angle analysis was performed (2 μL water drops, KRUSS EasyDrop). Statistical differences between groups was determined using ANOVA. Results and Discussion. Figure 1a summarizes the roughness results, with significant roughening being observed with between surface blanks and all surface modification techniques, especially the CoBlasted 90 μm grit treatments. As expected, wettability (shown in Figure 1b) was significantly affected by PTFE modifications and also by the introduction chitosan and vancomycin. Conclusions. As can be seen from these results, changing the coating of a material can change the surface topography and the wettability of the surface, which can be beneficial for different applications. The results from this work show that the CoBlast and BioDep processes significantly affect both wettability and roughness, and that the benefits and potential drawbacks of each must be considered when assessing their potential for biofilm resistance. PTFE-coated samples would be best used when wanting to prevent a hydrophobic substance from binding to the material, while the alumina-coated or blank samples would be best used to prevent a hydrophilic substance from binding. In the future, nonpolar liquid wettability will be assessed to better mimic in-vivo conditions and to determine surface energy to be able to make better conclusions about the relationship between surface roughness and wettability. For any figures or tables, please contact the authors directly

Periprosthetic joint infection (PJI) remains one of the most devastating complications that can occur following total joint arthroplasty. Failure rate of standard treatment for PJI is estimated to be around 40% at two years post revision surgery. A major clinical challenge contributing to treatment failure and antibiotics tolerance is the biofilm formation on implant surfaces. Lytic bacteriophages (phages) can target biofilm associated bacteria at localized sites of infection by penetrating and disrupting biofilm matrices; furthermore, phage replication within the biofilm leads to high local concentrations resulting in a powerful therapeutic effect. The aim of this study is to test if phage cocktail has better antimicrobial effect than vancomycin or a single agent phage against biofilm forming MRSA clinical strain Staphylococcus aureus (S. aureus). S. aureus BP043 was utilized in this study. This strain is a PJI clinical isolate, methicillin resistant (MRSA) and biofilm-former. Three lytic phages, namely, 44AHJD, Team1 and P68, known to infect S. aureus, were tested for their efficiency against S. aureus BP043. The ability of the phages to eliminate S. aureus BP043 planktonic or biofilm cultures was tested either as singular phages or as a cocktail of the three phages. Planktonic cells were adjusted to ∼ 1×109 CFU/mL in tryptic soy broth (TSB) and each phage was added alone or as a cocktail at ∼ 1×109 PFU/mL with moi of 1 (a multiplicity of infection). Bacterial growth was assessed by measuring optical densities at 24hr and was compared to the control of S. aureus BP043 with no phage. BP043 biofilms was grown for 24hr on plasma sprayed titanium (Ti-6Al-4V) alloy disc surfaces. Mature biofilms were then treated with one of the three phages or a cocktail of the 3 phages for 24hr at ∼ 1×109 PFU/mL in TSB. Then, biofilms were dislodged, and bacterial survival was assessed by plating on tryptic soy agar plates. Survival in treated biofilms was compared to control biofilm that was exposed only to TSB. Planktonic cells growth in the presence of phage 44AHJD was reduced significantly (p <0.0001) after 24hr compared to the control. The other two phages did not show a similar pattern when used alone. The reduction in growth was more pronounced when the three phages were combined together (p <0.0001, compared to the control, p=0.011 3, 44AHJD alone versus 3 phages). Exposing BP043 biofilm to the phage cocktail resulted in more than three logs (CFU/mL) reduction in bacterial load residing in the biofilm while no effect was detected when either vancomycin or each phage was used solely. We have demonstrated that the usage of lytic phage cocktail contributes to better clearance of planktonic cultures of the S. aureus MRSA isolate. More importantly, viable bacteria in the biofilms that were grown on plasma sprayed titanium discs were reduced by more than 37% when a phage cocktail was used compared to using a single phage or vancomycin. This work is aimed at gathering preclinical evidence for using phage as a new therapeutic avenue to treat PJI

Introduction. Pin-tract infections are a common problem in orthopaedic surgery, which limits the time an external fixator or Taylor spatial frame can be applied to a patient. The purpose of our study is to evaluate the ability of a novel implant surface coating — cationic steroid antibiotic (CSA)-44 — to delay or prevent the onset of these infections. This coating mimics endogenous antimicrobial peptides of the innate immune system and has been shown to effectively eradicate biofilms as well as prevent infection and stimulate healing of open, contaminated fractures. Methods. Surgeries were performed on 20 animals (outbred; Sprague-Dawley strain rats). Each animal received both CSA-coated and standard-of-care titanium pins, with pins randomized to the fifth or sixth vertebrae prior to surgeries. Animals were also randomized to either “Imaging” (imaging analysis) or “Infection” (microbiological analysis) cohorts. Surgeons were blinded to pin types and analyses cohorts. Digital images of pin sites were collected weekly over 12 weeks, and then graded by two orthopaedic surgery residents according to an established Likert scale. Graders were blinded to animal numbers, pin types, and timepoints (Figure 1). For the infection analysis cohort, four specimens per site were subjected to microbiological analysis from each site (i.e. pin, superficial skin swab, deep skin swab, sonicated bone). Each specimen was processed on three different microbiological plates (i.e. BAP, CAN, MAC) using standardized techniques. Imaging analysis was performed by dissecting vertebrae en bloc with pin retained, followed by fixation in 10% neutral buffered formalin for 72 hours. Following a graded ethanol series and storage in 70% ethanol, specimens were scanned with microcomputed tomography (µCT). Statistical analyses were performed to compare pin site appearance (chi-square testing) as well as total bacterial colony counts within each plate cohort and imaging data (Kruskal-Wallis testing); for all tests, significance was set at α=0.05. Results. Weekly digital images of each pin site were collected, graded, and then averaged (Figure 2). Statistical analysis showed no significant difference in pin appearance between the control and CSA pin cohorts at any timepoints. For the infection analysis cohort, bacterial colonies were counted on BAP, CAN, and MAC plates, followed by bacteria species identification (Figure3). Statistical analysis showed no significant difference in total bacterial colony counts between the control and CSA pin cohorts in any of the plate groups. For the imaging cohort, post-processing and subsequent data and statistical analyses are ongoing. Discussion. No significant differences were found between the control and CSA pin cohorts, with respect to pin appearance during the 12-week study or total bacterial colony counts on three plates, indicating that the control and CSA pins performed equivalently. Imaging analysis is ongoing. Although the environmentally-acquired infection model in an outbred rat strain was used to replicate the onset of pin tract infections in human populations, many animals showed Grade 1 or 2 pin site appearances at the 12-week endpoint. A follow-on study is underway using a direct bacterial seeding model. For any figures or tables, please contact the authors directly

INTRODUCTION. Experience with Metal on Metal (MoM) hip resurfacing devices has shown adequate cementation of the femoral head is critical for implant survival. Bone necrosis can be caused by the temperature change in the peri-prosthetic bone whilst the cement cures during implantation. This can lead to implant loosening, head/neck fracture and implant failure. During the implantation it is known that implants change shape potentially altering joint clearance and causing loosening. Given the history of Metal on Metal implant failure due adverse tissue reactions from Cobalt and Chromium particles we sought to test a novel Ceramic on Ceramic (CoC) bearing which may mitigate such problems. AIM. We set out to compare the behaviour of a novel ceramic femoral head component to a standard metal component in a hip resurfacing system after cemented implantation in a physiological warmed cadaveric model. Our first aim was to perform heat transfer analysis: To document time to, and extent of, maximum temperature change on the metal/ceramic surface and inside the resurfaced femoral head bone. Our second aim was to perform a dimensional analysis: To document any resulting deformation in the metal/ceramic femoral head bearing diameter during cementation. METHODS. Femurs were removed from four fresh frozen cadavers and placed into a vice. One surgeon with extensive experience in hip resurfacing surgery (JH) prepared all the femoral heads for implantation. Cadaveric warming was performed using a thermostatic silicone heating element to achieve near physiological conditions (28–32°C). The femur components were then implanted onto the femur head using Simplex P (Stryker) low viscosity bone cement. We used four ceramic (ReCerf™) and four metal implants (ADEPT®) of equal and varying size. (2 × (42mm, 46mm, 48mm, 50mm). Temperature change was measured using a thermometer probe placed into femur neck and head from the lateral side with position check using an image intensifier. Implant surface temperature was measured using a calibrated infrared thermometer at a standard 30cm distance. Head bearing surface diameter was measured using a micro-meter. Measurements were taken 2mins pre-implantation and sequentially at 1, 5, 10, 15, 20, 25 and 30 minutes after implantation. RESULTS. The bone temperature change for both metal and ceramic implants fell after implantation and then increased. The implant surface temperature increased and then stabilised for both implants. There was no significant difference in the bone or surface temperature change between metal and ceramic implants. The bearing surface diameter change was greater in the metal implants, although this was not significant. All implants returned to within one µm of initial surface diameter at 30 minutes. CONCLUSIONS. The femoral head component of a ceramic resurfacing has similar properties for surface temperature change following implantation to conventional MOM resurfacing. The periprosthetic bone is not at risk of significant heat necrosis during cementation (max temp 32°C). The deformation following implantation was similar for both metal and ceramic components. All implants returned to near initial diameter. The deformation and temperature changes following implantation of a ceramic resurfacing are similar to a metal implant

Joint hemiarthroplasty replaces one side of a synovial joint and is a viable alternative to total joint arthroplasty when one side of the joint remains healthy. Most hemiarthroplasty implants used in current clinical practice are made from stiff materials such as cobalt chrome or ceramic. The substitution of one side of a soft cartilage-on-cartilage articulation with a rigid implant often leads to damage of the opposing articular cartilage due to the resulting reductions in contact area and increases in cartilage stress. The improvement of post-operative hemiarthroplasty articular contact mechanics is of importance in advancing the performance and longevity of hemiarthroplasty. The purpose of the present study was to investigate the effect of hemiarthroplasty surface compliance on early in-vitro cartilage wear and joint contact mechanics. Cartilage wear tests were conducted using a six-station pin-on-plate apparatus. Pins were manufactured to have a hemispherical radius of curvature of 4.7 mm using either Bionate (DSM Biomedical) having varying compliances (80A [E=20MPa], 55D [E=35MPa], 75D [E=222MPa], n=6 for each), or ceramic (E=310GPa, n=5). Cartilage plugs were cored from fresh unfrozen bovine knee joints using a 20 mm hole saw and mounted in lubricant-containing chambers, with alpha calf serum diluted with phosphate buffer solution to a protein concentration of 17 g/L. The pins were loaded to 30N and given a stroke length of 10 mm for a total of 50,000 cycles at 1.2 Hz. Volumetric cartilage wear was assessed by comparing three-dimensional cartilage scans before and during wear testing. A two-way ANOVA was used for statistical analysis. To assess hemiarthroplasty joint contact mechanics, 3D finite element modelling (ABAQUS v6.12) was used to replicate the wear testing conditions. Cartilage was modeled using neo-Hookean hyper-elastic material properties. Contact area and peak contact stress were estimated. The more compliant Bionate 80A and 55D pins produced significantly less volumetric cartilage wear compared with the less compliant Bionate 75D and ceramic pins (p 0.05). In terms of joint contact mechanics, the more compliant materials (Bionate 80A and 55D) had significantly lower maximum contact stress levels compared to the less compliant Bionate 75D and ceramic pins (p < 0 .05). The results of this study show a relationship between hemiarthroplasty implant surface compliance and early in vitro cartilage wear, where the more compliant surfaces produced significantly lower amounts of cartilage wear. The results of the joint contact mechanics analysis showed that the more compliant hemiarthroplasty materials produced lower maximum cartilage contact stresses than the less compliant materials, likely related to the differences in wear observed. More compliant hemiarthroplasty surfaces may have the potential to improve post-operative cartilage contact mechanics by increasing the implant-cartilage contact area while reducing peak contact stress at the implant-cartilage interface, however, such materials must be resistant to surface fatigue and longer-term cartilage wear/damage must be assessed

Surface coatings have been introduced to total joint orthopaedics over the past decades to enhance osseointegration between metal implants and bone. However, complications such as aseptic loosening and infection persist. Inadequate osseointegration remains a complication associated with implants that rely on osseointegration for proper function. This is particularly challenging with implants having relatively flat and small surface areas that have high shear loading, such as noncemented uni and total condylar knee tibial trays. Faster osseointegration can enhance recovery as a result of improved load distribution and a more stable bone-implant interface. Traditionally noncemented porous bone ingrowth coatings on knee, hip and shoulder implants are typically texturised by thermal plasma spray coating, sintered metal bead coatings, or 3-D additive manufactured structures that provide porous surface features having the rough texture with pore sizes on the order of 150 to 300 micrometers. These surfaces are often further chemically enhanced with hydroxyapatite (HA) deposition. This provides macro-mechanical (millimeter scale) and micro-mechanical (micrometer scale) bone remodeling into the implant surface. However, at the nanoscale and cellular level, these surfaces appear relatively smooth. More recent studies are showing the importance of controlling the macro, micro, and the nano (nanometer scale) surface topographies to enhance cell interaction. In vitro and in vivo research shows surfaces with nanoscale features in the metal substrate result in enhanced osseointegration, greater bone-implant contact area and pullout force, and potentially bactericidal. One surface modification treatment technique of particular promise is nano-texturing via electrochemical anodization to bio-mimicking TiO2 nanotube arrays that are superimposed onto existing porous surface microstructures to further enhance the already known bone ingrowth properties of these porous structures by superimposing onto the existing microstructure arrays of nanotubes approximately 100 nanometers in outside diameter and 300–500 nanometers in height. In an ovine model, 3-D printed Direct Metal Laser Deposition (DMLS) additive manufactured porous Ti-6Al-4V implant with and without TiO2 nanotube array nano-texturing were compared to similar sized implants with commercially available sintered beads with HA coating and additive manufactured cobalt chrome implants. The average bond strength was significantly higher (42%) when the implants were nano-texturised and similarly stronger (53%) compared to HA coated sintered bead implants. Histology confirms over 420% more direct bonded growth of new bone from 0.5mm to 1.0mm deep into the porosity on the implants when the same implants are nano-texturised. Nano-texturing also changes the surface of the implant to repel methicillin-resistant staphylococcus aureus (MRSA) in an in vivo rabbit model limiting biofilm formation on the porous surface compared with non-treated porous surfaces. Since nano-texturizing only modifies the nano-morphology of the surface and does not add antibiotics or other materials to the implant, these animal studies shows great promise that nano-texturizing the TiO2 coating may not only enhance osseointegration, but also repels bacteria from porous implant surfaces. As such, we believe nano-texturing of porous implants will be the next advancement in surface coating technology

Few studies have been reported focusing on developing implant surface nanofiber (NF) coating to prevent infection and enhance osseointegration by local drug release. In this study, coaxial doxycycline (Doxy)-doped polycaprolactone/polyvinyl alcohol (PCL/PVA) NFs were directly deposited on the titanium (Ti) implant surface during electrospinning. The bonding strength of Doxy-doped NF coating on Ti implants was confirmed by a stand single-pass scratch test. The improved implant osseointegration by PCL/PVA NF coatings in vivo was confirmed by scanning electron microscopy, histomorphometry and micro computed tomography at 2, 4 and 8 weeks after implantation. The bone contact surface (%) changes of NF coating group (80%) is significantly higher than that of no NF group (< 5%, p<0.05). Finally, we demonstrated that Doxy-doped NF coating effectively inhibited bacterial infection and enhanced osseointegration in an infected (Staphylococcus aureus) tibia implantation rat model. Doxy released from NF coating inhibited bacterial growth up to 8 weeks in vivo. The maximal push-in force of Doxy-NF coating (38 N) is much higher than that of NF coating group (6.5 N) 8 weeks after implantation (p<0.05), which was further confirmed by quantitative histological analysis and micro computed tomography. These findings indicate that coaxial PCL/PVA NF coating doped with Doxy and/or other drugs have great potential in enhancing implant osseointegration and preventing infection

Introduction. Implant-cement debonding at the knee has been reported previously [1]. The strength of the mechanical interlock of bone cement on to an implant surface can be associated with both bone cement and implant related factors. In addition to implant surface profile, sub-optimal mixing temperatures and waiting times prior to cement application may weaken the strength of the interlock. Aims. The study aimed to investigate the influence of bone cement related factors such as mixing temperature, viscosity, and the mixing and waiting times prior to application, in combination with implant surface roughness, on the tensile strength at the interface. Materials and Methods. Tensile tests were carried out on two types of hand-mixed cement, high (HV) and medium viscosity (MV), sandwiched between two cylindrical Cobalt-Chrome coupons with either smooth (60 grit) or rough (20 grit) surface finishes. 144 Specimens were prepared with a cement thickness layer of 2.5 mm in customised rigs (Figure 1). The samples were grouped and tested at two mixing temperatures (23 and 19 degrees), at different mixing times (HV-30s, MV-45s). Waiting times after mixing were varied between early (1.5 min), optimal (4.5 min) or late (8 min); for HV and 4 min, 7.5 min and 11 min for MV cements. All the samples were cured for 24 hours prior to testing. The peak force and stress was calculated for all specimens. Results and Conclusion. Surface Finish: Rough surfaced samples had significantly higher (p < 0.05) mean tensile forces and stress than smooth samples at both 19 and 23 degrees across HV and MV cement types. Cement Type: MV cements, when applied to rough samples with waiting times of 4 minutes at 23 degrees, and 11 minutes at 19 degrees, resulted in the highest peak tensile forces, followed by 7.5 minutes at 23 and 19 degrees respectively (Figure 2). Temperature at different application times for rough and smooth samples: for MV cement, rough samples prepared at 23 degrees, 4 minutes, and smooth samples at 19 degrees, 7.5 minutes were found to be significantly better (p < 0.05) than their counterparts. For HV cement, 23 degrees was found to be better (p < 0.05) for smooth samples at applications times of 4.5 and 8 minutes and 19 degrees for application times of 1.5 minutes. No significant difference was noted for rough samples for the same. Application times at different temperatures for rough and smooth samples: at both 19 and 23 degrees, there were no differences between application times within the rough sample groups for HV or MV. However, for smooth samples, HV cement, tensile forces were significantly higher (p < 0.05) at 23 degrees in the following order; 8 minutes > 4.5 minutes > 1.5. The results show that implant surface roughness and cement mixing time, temperature, viscosity and application times affect the strength of the interlock at the interface

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. Methods. Cancellous cylindrical bone cores were harvested from bovine metatarsals and divided into five groups under different conditions. After incubation for 4 & 7 weeks, the viability of each bone sample was evaluated using Live-Dead assay and microscopic anatomy of cells were determined using histology stain H&E. Matrix deposits on the scaffolds were examined with scanning electron microscopy (SEM) while its chemical composition was measured using energy-dispersive x–ray spectroscopy (EDX). Results. The viability of bone cores was maintained after seven weeks using our protocol and ex vivo system. From SEM images, we found more organic matrix deposition along with crystallite like structures on the metal samples pulled from the bioreactor indicating the initial stages of mineralization. EDX results further confirmed the presence of carbon and calcium phosphates in the matrix. Conclusion. A bone bioreactor can be used a tool alternate to in-vivo for bone ingrowth studies on new implant surfaces or coatings