Deformable titanium for acetabular revision surgery: a proof of concept.

Custom-made triflange acetabular implants are increasingly used in complex revision surgery where supporting bone stock is diminished. In most cases these triflange cups induce stress-shielding. A new concept for the triflange is introduced that uses deformable porous titanium to redirect forces from the acetabular rim to the bone stock behind the implant and thereby reduces further stress-shielding. This concept is tested for deformability and primary stability.Three different designs of highly porous titanium cylinders were tested under compression to determine their mechanical properties. The most promising design was used to design five acetabular implants either by incorporating a deformable layer at the back of the implant or by adding a separate generic deformable mesh behind the implant. All implants were inserted into sawbones with acetabular defects followed by a cyclic compression test of 1800N for 1000 cycles.The design with a cell size of 4 mm and 0.2 mm strut thickness performed the best and was applied for the design of the acetabular implants. An immediate primary fixation was realized in all three implants with an incorporated deformable layer. One of the two implants with a separate deformable mesh needed fixation with screws. Cyclic tests revealed an average additional implant subsidence of 0.25 mm that occurred in the first 1000 cycles with minimal further subsidence thereafter.It is possible to realize primary implant fixation and stability in simulated large acetabular revision surgery using a deformable titanium layer behind the cup. Additional research is needed for further implementation of such implants in the clinic.

Toward Antibacterial Coatings for Personalized Implants.

The complex reconstructive surgeries for which patient-specific orthopedic, maxillofacial, or dental implants are used often necessitate wounds that are open for a considerable amount of time. Unsurprisingly, this allows bacteria to establish implant-associated infection, despite the scrupulous sterilization efforts made during surgery. Here, we developed a prophylactic bactericidal coating via electrophoretic deposition technology for two 3D-printed porous titanium implant designs. The surface characteristics, antibiotic release behavior, antibacterial properties, and impact on osteoblast cell proliferation of the optimized coatings were investigated. The results unequivocally confirmed the biofunctionality of the implants in vitro. This study reveals a new avenue for future antibacterial patient-specific implants.

Treating infections with ionizing radiation: a historical perspective and emerging techniques.

BACKGROUND: Widespread use and misuse of antibiotics have led to a dramatic increase in the emergence of antibiotic resistant bacteria, while the discovery and development of new antibiotics is declining. This has made certain implant-associated infections such as periprosthetic joint infections, where a biofilm is formed, very difficult to treat. Alternative treatment modalities are needed to treat these types of infections in the future. One candidate that has been used extensively in the past, is the use of ionizing radiation. This review aims to provide a historical overview and future perspective of radiation therapy in infectious diseases with a focus on orthopedic infections. METHODS: A systematic search strategy was designed to select studies that used radiation as treatment for bacterial or fungal infections. A total of 216 potentially relevant full-text publications were independently reviewed, of which 182 focused on external radiation and 34 on internal radiation. Due to the large number of studies, several topics were chosen. The main advantages, disadvantages, limitations, and implications of radiation treatment for infections were discussed. RESULTS: In the pre-antibiotic era, high mortality rates were seen in different infections such as pneumonia, gas gangrene and otitis media. In some cases, external radiation therapy decreased the mortality significantly but long-term follow-up of the patients was often not performed so long term radiation effects, as well as potential increased risk of malignancies could not be investigated. Internal radiation using alpha and beta emitting radionuclides show great promise in treating fungal and bacterial infections when combined with selective targeting through antibodies, thus minimizing possible collateral damage to healthy tissue. CONCLUSION: The novel prospects of radiation treatment strategies against planktonic and biofilm-related microbial infections seem feasible and are worth investigating further. However, potential risks involving radiation treatment must be considered in each individual patient.

Bactericidal coating to prevent early and delayed implant-related infections.

The occurrence of an implant-associated infection (IAI) with the formation of a persisting bacterial biofilm remains a major risk following orthopedic biomaterial implantation. Yet, progress in the fabrication of tunable and durable implant coatings with sufficient bactericidal activity to prevent IAI has been limited. Here, an electrospun composite coating was optimized for the combinatorial and sustained delivery of antibiotics. Antibiotics-laden poly(ε-caprolactone) (PCL) and poly`1q`(lactic-co glycolic acid) (PLGA) nanofibers were electrospun onto lattice structured titanium (Ti) implants. In order to achieve tunable and independent delivery of vancomycin (Van) and rifampicin (Rif), we investigated the influence of the specific drug-polymer interaction and the nanofiber coating composition on the drug release profile and durability of the polymer-Ti interface. We found that a bi-layered nanofiber structure, produced by electrospinning of an inner layer of [PCL/Van] and an outer layer of [PLGA/Rif], yielded the optimal combinatorial drug release profile. This resulted in markedly enhanced bactericidal activity against planktonic and adherent Staphylococcus aureus for 6 weeks as compared to single drug delivery. Moreover, after 6 weeks, synergistic bacterial killing was observed as a result of sustained Van and Rif release. The application of a nanofiber-filled lattice structure successfully prevented the delamination of the multi-layer coating after press-fit cadaveric bone implantation. This new lattice design, in conjunction with the multi-layer nanofiber structure, can be applied to develop tunable and durable coatings for various metallic implantable devices. This is particularly appealing to tune the release of multiple antimicrobial agents over a period of weeks to prevent early and delayed onset IAI.

Radioimmunotherapy of methicillin-resistant Staphylococcus aureus in planktonic state and biofilms.

BACKGROUND: Implant associated infections such as periprosthetic joint infections are difficult to treat as the bacteria form a biofilm on the prosthetic material. This biofilm complicates surgical and antibiotic treatment. With rising antibiotic resistance, alternative treatment options are needed to treat these infections in the future. The aim of this article is to provide proof-of-principle data required for further development of radioimmunotherapy for non-invasive treatment of implant associated infections. METHODS: Planktonic cells and biofilms of Methicillin-resistant staphylococcus aureus are grown and treated with radioimmunotherapy. The monoclonal antibodies used, target wall teichoic acids that are cell and biofilm specific. Three different radionuclides in different doses were used. Viability and metabolic activity of the bacterial cells and biofilms were measured by CFU dilution and XTT reduction. RESULTS: Alpha-RIT with Bismuth-213 showed significant and dose dependent killing in both planktonic MRSA and biofilm. When planktonic bacteria were treated with 370 kBq of 213Bi-RIT 99% of the bacteria were killed. Complete killing of the bacteria in the biofilm was seen at 185 kBq. Beta-RIT with Lutetium-177 and Actinium-225 showed little to no significant killing. CONCLUSION: Our results demonstrate the ability of specific antibodies loaded with an alpha-emitter Bismuth-213 to selectively kill staphylococcus aureus cells in vitro in both planktonic and biofilm state. RIT could therefore be a potentially alternative treatment modality against planktonic and biofilm-related microbial infections.

Prophylaxis of implant-related infections by local release of vancomycin from a hydrogel in rabbits.

Local prophylaxis with antibiotic-loaded bone cement is a successful method to prevent post-operative infections in patients receiving orthopaedic implants. No comparable method is available for uncemented implants. Therefore, a hydrogel consisting of hyaluronic and polylactic acids was evaluated in a rabbit model for delivery of antimicrobial agents to prevent post-operative infections. In a pilot study, the suitability of the in vivo model was assessed by testing the hydrogel as carrier material for antimicrobial agents.In the main study, the antimicrobial-agent-loaded hydrogel was evaluated for infection prophylaxis. Rabbits received a titanium rod intramedullary in the tibia after contamination with Staphylococcus aureus. The rods were coated with unloaded hydrogel (Gel), hydrogel loaded with 2 % (Van2) or 5 % vancomycin (Van5), bioactive glass (BAG) or N-acetyl-L-cysteine (NAC). To analyse the infection severity after 28 d, histopathological, bacteriological, micro-computed tomographic and haematological analyses were performed. In the pilot study, the Van5 group had less infection (0/6 infected) as compared to the Gel group (5/5, p = 0.000) and the in vivo model was deemed suitable. In the main study, in the Van2 and Van5 groups, the number of infected animals was lower [1/6 (p = 0.006) and 2/6 (p = 0.044) infected, respectively]. In contrast, BAG and NAC groups showed no infection reduction (5/6 both groups, p = 0.997). The hydrogel can be used as a local carrier of vancomycin for prophylaxis of implant-related infections.The present study showed promising results for local delivery of antibacterial agents by hydrogel to prevent implant-related infections.

The accuracy of diagnostic Imaging techniques in patients with a suspected Fracture-related Infection (IFI) trial: study protocol for a prospective multicenter cohort study.

INTRODUCTION: The optimal diagnostic imaging strategy for fracture-related infection (FRI) remains to be established. In this prospective study, the three commonly used advanced imaging techniques for diagnosing FRI will be compared. Primary endpoints are (1) determining the overall diagnostic performances of white blood cell (WBC) scintigraphy, fluorodeoxyglucose positron emission tomography (FDG-PET) and magnetic resonance imaging (MRI) in patients with suspected FRI and (2) establishing the most accurate imaging strategy for diagnosing FRI. METHODS AND ANALYSIS: This study is a non-randomised, partially blinded, prospective cohort study involving two level 1 trauma centres in The Netherlands. All adult patients who require advanced medical imaging for suspected FRI are eligible for inclusion. Patients will undergo all three investigational imaging procedures (WBC scintigraphy, FDG-PET and MRI) within a time frame of 14 days after inclusion. The reference standard will be the result of at least five intraoperative sampled microbiology cultures, or, in case of no surgery, the clinical presence or absence of infection at 1 year follow-up. Initially, the results of all three imaging modalities will be available to the treating team as per local protocol. At a later time point, all scans will be centrally reassessed by nuclear medicine physicians and radiologists who are blinded for the identity of the patients and their clinical outcome. The discriminative ability of the imaging modalities will be quantified by several measures of diagnostic accuracy. ETHICS AND DISSEMINATION: Approval of the study by the Institutional Review Board has been obtained prior to the start of this study. The results of this trial will be disseminated by publication of peer-reviewed manuscripts, presentation in abstract form at scientific meetings and data sharing with other investigators through academically established means. TRIAL REGISTRATION NUMBER: The IFI trial is registered in the Netherlands Trial Register (NTR7490).

The role of bacterial stimuli in inflammation-driven bone formation.

Immune cells and their soluble factors regulate skeletal cells during normal bone regeneration and pathological bone formation. Bacterial infections can trigger immune responses that activate pro-osteogenic pathways, but these are usually overshadowed by osteolysis and concerns of systemic inflammation. The aim of this study was to determine whether the transient local inflammatory reaction to non-viable bacterial immune agonists could lead to favourable new bone formation. In a series of rabbit studies, as proof-of-concept, how tibial intramedullary injection of viable or killed bacterial species affected bone remodelling and new bone formation was determined. Application of killed bacteria led to considerable new bone formation after 4 weeks, without the prolonged systemic inflammation and exaggerated bone lysis seen with active infection. The osteo-immunomodulatory effects of various species of killed bacteria and the dose response relationship were subsequently screened in ectopically-implanted ceramic scaffolds. Histomorphometry after 8 weeks showed that a relatively low dose of killed bacteria enhanced ectopic bone induction. Moreover, lipoteichoic acid - the bacterial cell-wall derived toll-like-receptor (TLR)-2 activator - was identified as an osteo-stimulatory factor. Collectively, the data indicated that bacterial stimuli could be harnessed to stimulate osteogenesis, which occurs through a synergy with osteoinductive signals. This finding holds promise for the use of non-viable bacteria, bacterial antigens, or their simplified analogues as immuno-modulatory bone regenerating tools in bone biomaterials.

Data on a rat infection model to assess porous titanium implant coatings.

A model is needed to study the effectiveness of different anti-bacterial coatings on complex metal implants in a bone environment. This article shares data on the design of porous titanium implants for intramedullary implantation in the proximal rat tibia. The implant length, diameter and porosity were optimized after testing on cadaveric specimens. This article shares data on which parameters are critical to establish a chronic implant infection in Sprague Dawley rats when using the new implant design. To this end, different strains of Staphylococcus aureus and inoculation doses were investigated.

Antibacterial and immunogenic behavior of silver coatings on additively manufactured porous titanium.

Implant-associated infections (IAI) are often recurrent, expensive to treat, and associated with high rates of morbidity, if not mortality. We biofunctionalized the surface of additively manufactured volume-porous titanium implants using electrophoretic deposition (EPD) as a way to eliminate the peri-operative bacterial load and prevent IAI. Chitosan-based (Ch) coatings were incorporated with different concentrations of silver (Ag) nanoparticles or vancomycin. A full-scale in vitro and in vivo study was then performed to evaluate the antibacterial, immunogenic, and osteogenic activity of the developed implants. In vitro, Ch + vancomycin or Ch + Ag coatings completely eliminated, or reduced the number of planktonic and adherent Staphylococcus aureus by up to 4 orders of magnitude, respectively. In an in vivo tibia intramedullary implant model, Ch + Ag coatings caused no adverse immune or bone response under aseptic conditions. Following Staphylococcus aureus inoculation, Ch + vancomycin coatings reduced the implant infection rate as compared to chitosan-only coatings. Ch + Ag implants did not demonstrate antibacterial effects in vivo and even aggravated infection-mediated bone remodeling including increased osteoclast formation and inflammation-induced new bone formation. As an explanation for the poor antibacterial activity of Ch + Ag implants, it was found that antibacterial Ag concentrations were cytotoxic for neutrophils, and that non-toxic Ag concentrations diminished their phagocytic activity. This study shows the potential of EPD coating to biofunctionalize porous titanium implants with different antibacterial agents. Using this method, Ag-based coatings seem inferior to antibiotic coatings, as their adverse effects on the normal immune response could cancel the direct antibacterial effects of Ag nanoparticles. STATEMENT OF SIGNIFICANCE: Implant-associated infections (IAI) are a clinical, societal, and economical burden. Surface biofunctionalization approaches can render complex metal implants with strong local antibacterial action. The antibacterial effects of inorganic materials such as silver nanoparticles (Ag NPs) are often highlighted under very confined conditions in vitro. As a novelty, this study also reports the antibacterial, immunogenic, and osteogenic activity of Ag NP-coated additively-manufactured titanium in vivo. Importantly, it was found that the developed coatings could impair the normal function of neutrophils, the most important phagocytic cells protecting us from IAI. Not surprisingly, the Ag NP-based coatings were outperformed by an antibiotic-based coating. This emphasizes the importance of also targeting implant immune-modulatory functions in future coating strategies against IAI.

Simultaneous Delivery of Multiple Antibacterial Agents from Additively Manufactured Porous Biomaterials to Fully Eradicate Planktonic and Adherent Staphylococcus aureus.

Implant-associated infections are notoriously difficult to treat and may even result in amputation and death. The first few days after surgery are the most critical time to prevent those infections, preferably through full eradication of the micro-organisms entering the body perioperatively. That is particularly important for patients with a compromised immune system such as orthopedic oncology patients, as they are at higher risk for infection and complications. Full eradication of bacteria is, especially in a biofilm, extremely challenging due to the toxicity barrier that prevents delivery of high doses of antibacterial agents. This study aimed to use the potential synergistic effects of multiple antibacterial agents to prevent the use of toxic levels of these agents and achieve full eradication of planktonic and adherent bacteria. Silver ions and vancomycin were therefore simultaneously delivered from additively manufactured highly porous titanium implants with an extremely high surface area incorporating a bactericidal coating made from chitosan and gelatin applied by electrophoretic deposition (EPD). The presence of the chitosan/gelatin (Ch+Gel) coating, Ag, and vancomycin (Vanco) was confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The release of vancomycin and silver ions continued for at least 21 days as measured by inductively coupled plasma (ICP) and UV-spectroscopy. Antibacterial behavior against Staphylococcus aureus, both planktonic and in biofilm, was evaluated for up to 21 days. The Ch+Gel coating showed some bactericidal behavior on its own, while the loaded hydrogels (Ch+Gel+Ag and Ch+Gel+Vanco) achieved full eradication of both planktonic and adherent bacteria without causing significant levels of toxicity. Combining silver and vancomycin improved the release profiles of both agents and revealed a synergistic behavior that further increased the bactericidal effects.

Antibacterial Behavior of Additively Manufactured Porous Titanium with Nanotubular Surfaces Releasing Silver Ions.

Additive manufacturing (3D printing) has enabled fabrication of geometrically complex and fully interconnected porous biomaterials with huge surface areas that could be used for biofunctionalization to achieve multifunctional biomaterials. Covering the huge surface area of such porous titanium with nanotubes has been already shown to result in improved bone regeneration performance and implant fixation. In this study, we loaded TiO2 nanotubes with silver antimicrobial agents to equip them with an additional biofunctionality, i.e., antimicrobial behavior. An optimized anodizing protocol was used to create nanotubes on the entire surface area of direct metal printed porous titanium scaffolds. The nanotubes were then loaded by soaking them in three different concentrations (i.e., 0.02, 0.1, and 0.5 M) of AgNO3 solution. The antimicrobial behavior and cell viability of the developed biomaterials were assessed. As far as the early time points (i.e., up to 1 day) are concerned, the biomaterials were found to be extremely effective in preventing biofilm formation and decreasing the number of planktonic bacteria particularly for the middle and high concentrations of silver ions. Interestingly, nanotubes not loaded with antimicrobial agents also showed significantly smaller numbers of adherent bacteria at day 1, which may be attributed to the bactericidal effect of high aspect ratio nanotopographies. The specimens with the highest concentrations of antimicrobial agents adversely affected cell viability at day 1, but this effect is expected to decrease or disappear in the following days as the rate of release of silver ions was observed to markedly decrease within the next few days. The antimicrobial effects of the biomaterials, particularly the ones with the middle and high concentrations of antimicrobial agents, continued until 2 weeks. The potency of the developed biomaterials in decreasing the number of planktonic bacteria and hindering the formation of biofilms make them promising candidates for combating peri-operative implant-associated infections.

Joint surgery in von Willebrand disease: a multicentre cross-sectional study.

BACKGROUND: Joint bleeds are reported by 23% of von Willebrand disease (VWD) patients and associated with orthopaedic surgery. Limited data are available on joint surgery in VWD. AIM: To assess the prevalence, indications, management and complications of joint surgery in VWD patients. METHODS: 804 VWD patients with historically lowest von Willebrand factor (VWF) activity ≤30 U dL-1 completed a questionnaire on joint bleeds, joint damage and orthopaedic surgery. We retrieved additional medical file data of patients who underwent surgery on large joints (shoulder, elbow, hip, knee or ankle). RESULTS: 116 out of 804 patients (14%) reported large joint surgery. Compared to VWD patients without previous orthopaedic surgery, these 116 patients reported more frequently a history of joint bleeds and joint damage (41% vs. 20%, P < 0.001 and 61% vs. 20%, P < 0.001). Medical file data on 126 large joint surgeries in 79 VWD patients revealed that this surgery was associated with joint damage due to prior joint bleeds in 24% of the procedures. Preoperative clotting factor correction (CFC) to prevent bleeding was administered in most cases (81%). Documentation on postoperative bleeding was found in 23 surgeries (18%). CONCLUSIONS: Large joint surgery is reported by 14% of VWD patients, related to joint bleeds in 24% and seems associated with bleeding complications frequently despite perioperative CFC.

Selection of an optimal antiseptic solution for intraoperative irrigation: an in vitro study.

BACKGROUND: With increasing bacterial antibiotic resistance and an increased infection risk due to more complicated surgical procedures and patient populations, prevention of surgical infection is of paramount importance. Intraoperative irrigation with an antiseptic solution could provide an effective way to reduce postoperative infection rates. Although numerous studies have been conducted on the bactericidal or cytotoxic characteristics of antiseptics, the combination of these characteristics for intraoperative application has not been addressed. METHODS: Bacteria (Staphylococcus aureus and S. epidermidis) and human cells were exposed to polyhexanide, hydrogen peroxide, octenidine dihydrochloride, povidone-iodine, and chlorhexidine digluconate at various dilutions for two minutes. Bactericidal properties were calculated by means of the quantitative suspension method. The cytotoxic effect on human fibroblasts and mesenchymal stromal cells was determined by a WST-1 metabolic activity assay. RESULTS: All of the antiseptics except for polyhexanide were bactericidal and cytotoxic at the commercially available concentrations. When diluted, only povidone-iodine was bactericidal at a concentration at which some cell viability remained. The other antiseptics tested showed no cellular survival at the minimal bactericidal concentration. CONCLUSIONS: Povidone-iodine diluted to a concentration of 1.3 g/L could be the optimal antiseptic for intraoperative irrigation. This should be established by future clinical studies.

Tobramycin-containing bone cement and systemic cefazolin in a one-stage revision. Treatment of infection in a rabbit model.

The efficacy of tobramycin-containing bone cement with that of systemic cefazolin for treatment of infection in a one-stage revision model is compared. In addition, the value of detecting bacterial DNA after antibiotic treatment was investigated. An implant was inserted into the right tibia of rabbits after inoculation with Staphylococcus aureus. At 28 days, the implant was removed. Subsequently, either plain bone cement with or without systemic administration of cefazolin, or tobramycin-containing bone cement was injected into the medullary canal. The tibiae were cultured 14 days after revision (Day 42), and showed a significant decrease in bacterial counts for both antibiotic groups compared with the control group (p

Prevention of infection with tobramycin-containing bone cement or systemic cefazolin in an animal model.

We investigated in an animal model the efficacy of tobramycin-containing bone cement and systemic cefazolin for infection prophylaxis. In 18 female rabbits, the femoral cavity was inoculated with Staphylococcus aureus before injection of bone cement. The first group of six rabbits received tobramycin-containing Simplex-P bone cement. Two other groups of six rabbits received plain Simplex-P bone cement. Preoperatively, in one of the two latter groups cefazolin was administered intravenously. The other group served as untreated controls. The rabbits were monitored for clinical signs of infection. At 7 days' follow-up, the femora were harvested and cultures from the bone adjacent to the cement plug were quantified. Cultures from the rabbits which received antibiotic prophylaxis (either cefazolin systemically or tobramycin-containing bone cement) were all negative. In contrast, all rabbits in the untreated control group had positive cultures. These rabbits also had other signs of infection such as an elevated erythrocyte sedimentation rate and loss of body weight. Culture results were confirmed by the absence of bacterial DNA in the polymerase chain reaction hybridization assay. In conclusion, we found that both tobramycin-containing bone cement and systemic cefazolin are effective in preventing implant bed infection in rabbits up to 7 days after contamination with S. aureus.

Prophylaxis of implant-related staphylococcal infections using tobramycin-containing bone cement.

In a rabbit model, premixed tobramycin-containing bone cement was studied for its efficacy to prevent infections with two frequently encountered staphylococcal species in arthroplasty surgery. After intramedullary inoculation with staphylococci, either standard or premixed tobramycin-containing Simplex-P bone cement was injected in the right femur of 120 rabbits. Development of infection was examined by culture of femoral bone after 7 or 28 days. Loss of body weight and elevated erythrocyte sedimentation rate in the control rabbits inoculated with Staphylococcus aureus were seen in the first postoperative week, returning to normal in 28 days. Inoculation with Staphylococcus epidermidis resulted only in a low-grade infection. All rabbits receiving premixed tobramycin-containing bone cement were free of signs of infection, and all their cultures were negative. Culture yield from Staphylococcus aureus controls increased with time and inoculum dose. Staphylococcus epidermidis controls needed higher inoculum doses to establish an infection, while culture yield decreased in time. These differences in mode of prosthesis-related infection are explained by differences in virulence factors.

Effects of hydrosyapatite coating on Ti-6A1-4V implant-site infection in a rabbit tibial model.

To investigate the effect of implant type after direct contamination, a hydroxyapatite-coated or noncoated Ti-6A1-4V implant was inserted into both tibiae of 32 New Zealand White rabbits. Prior to implantation, the left tibia was contaminated with increasing concentrations of Staphylococcus aureus (10(2)-10(5) colony-forming units), ranging from very low (10(2)) to relatively high (10(5)). Four weeks after implantation, half of the tibial bone adjacent to the implant was harvested for bacteriological examination. Bacterial counts were quantified by plating serial dilutions. For the histological evaluation, sections of the implant with the remaining tibia were examined by semiquantitative scoring of infection parameters. The bacteriological data showed the inoculum dose and implant type to have a significant effect on the culture outcome: more bacteria were retrieved from the hydroxyapatite-coated implants than from the noncoated titanium implants. Histological evaluation showed an increased score for the infected left tibiae compared with their contralateral control. In addition, with increasing inoculum dosage, the difference between the two types of implant increased. We demonstrated that infections can occur with biocompatible, noncemented implants and that they are related to the dose of the original inoculum. Bacteria were more likely to grow onto or next to the hydroxyapatite implants than on titanium implants and resulted in a more severe histopathological characterization of infection.