Argyria following the use of silver-coated megaprostheses: no association between the development of local argyria and elevated silver levels

Characteristics and Epidemiology of Megaprostheses Infections: A Systematic Review

BACKGROUND

Megaprostheses were first employed in oncological orthopedic surgery, but more recently, additional applications have arisen. These implants are not without any risks and device failure is quite frequent. The most feared complication is undoubtedly the implants' infection; however, the exact incidence is still unknown. This systematic review aims to estimate in the current literature the overall incidence of megaprosthesis infections and to investigate possible risk/protective factors.

METHODS

We conducted a systematic search for studies published from July 1971 to December 2023 using specific keywords. To be included, studies needed to report either the megaprosthesis anatomical site, and/or whether the megaprosthesis was coated, and/or the surgical indication as oncological or non-oncological reasons.

RESULTS

The initial literature search resulted in 1281 studies. We evaluated 10,456 patients and the overall infection rate was 12%. In cancer patients, the infection rate was 22%, while in non-oncological patients, this was 16% (trauma 12%, mechanical failure 17%, prosthetic joint infections 26%). The overall infection rates comparing coated and uncoated implants were 10% and 12.5%, respectively.

CONCLUSIONS

The number of megaprosthesis implants is increasing considerably. In traumatological patients, the infection rate is lower compared to all the other subgroups, while the infection rate remains higher in the cancer patient group. As these devices become more common, focused studies exploring epidemiological data, clinical outcomes, and long-term complications are needed to address the uncertainties in prevention and management.

Are silver-coated megaprostheses superior to uncoated megaprostheses in managing chronic end-stage periprosthetic hip and knee infection?

INTRODUCTION

Outcomes for silver coated megaprostheses (SC-MP) used in cases of end-stage periprosthetic joint infection (PJI) have not been clearly defined. Although attractive, concerns over implant longevity and the risk of infection relapse exist among the scientific community. Therefore, we sought to investigate the effect of silver coating in lower-extremity MPs used in such difficult-to-treat scenarios. The study's primary hypothesis was that the periprosthetic infection control rate would be higher in patients with silver-coated implants.

MATERIALS AND METHODS

Non-interventional retrospective study with a historical comparison group. We identified all consecutive end-stage hip and knee PJI cases at our center managed with exchange arthroplasty using a silver-coated megaprosthesis from January 2016 to March 2021, these cases were compared with a historical cohort of end-stage PJI cases managed with uncoated megaprostheses. The main outcome studied was infection control rate. Secondarily, we analyzed the short-to-medium-term survivorship of this type of silver-coated implant.

RESULTS

Fifty-nine megaprostheses used in cases of end-stage PJI were included in this study. We identified 30 cases of chronic hip or knee PJI in which a silver-coated modular megaprosthesis was implanted. Our non-coated megaprosthesis (NC-MP) historical group included 29 patients. Both groups had similar demographic characteristics. We found no statistically significant differences in infection control rate (80% vs. 82.8%, p = 0.47) or implant survivorship (90% vs. 89.65%, p = 1) after a mean follow-up for SC-MP of 46.43 months, and 48 months for the non-coated MP group. In relapsed cases, there were no differences in infection eradication after DAIR (66% SC-MP vs. 60% NC-MP success rate, p = 1). During the follow-up we observed one case of skin argyria without further repercussion.

CONCLUSION

We were unable to confirm our initial hypothesis that use of silver-coated implants in end-stage PJI scenarios may be associated with better outcomes in terms of infection control or implant survivorship.

A Counterion-Free Strategy for Chronic Metabolic Acidosis Based on an Orally Administered Gut-Restricted Inorganic Adsorbent

Chronic metabolic acidosis, arising as a complication of chronic kidney disease (CKD), not only reduces patients' quality of life but also aggravates renal impairment. The only available therapeutic modality, involving intravenous infusion of NaHCO3 , engenders undesirable sodium retention, thereby increasing hemodynamic load and seriously exacerbating the primary disease. This deleterious cascade extends to the development of cardiovascular diseases. Herein, an orally administered, gut-restricted inorganic adsorbent that can effectively alleviate chronic metabolic acidosis without causing any electrolytic derangement or superfluous cardiovascular strain is developed. The genesis of ABC-350 entails the engineering of bismuth subcarbonate via annealing, thereby yielding a partially β-Bi2 O3 -doped (BiO)2 CO3 biphasic crystalline structure framework enriched with atomic vacancies. ABC-350 can selectively remove chloride ions and protons from the gastrointestinal tract, mimicking the physiological response to gastric acid removal and resulting in increased serum bicarbonate. Owing to its gut-restricted nature, ABC-350 exhibits commendable biosafety, averting undue systemic exposure. In two rat models of metabolic acidosis, ABC-350 emerges not only as a potent mitigator of acidosis but also effects discernible amelioration concerning proximal tubular morphology, interstitial fibrosis, and the incendiary cascades incited by metabolic acidosis. ABC-350, as the translationally relevant material, provides a promising strategy for the treatment of metabolic acidosis.

Therapy of a Chronically Infected Total Femur Prothesis in a 40-year-old Patient

We report a case of a patient who was treated in 1999 at the age of 19 years with a proximal femur replacement due to Ewing sarcoma. After several infection-associated exchange procedures, the patient presented with a fistula and chronic infection of a total femur prosthesis in August 2019 at the age of 40 years. Interdisciplinary treatment with a 3-stage exchange procedure and implantation of a silver-coated total femur prosthesis was successfully performed and hip disarticulation could be avoided. After a follow-up of 2 years, the patient showed uneventful wound healing and full weight bearing without crutches.

Stabilization of Tibial Fractures at Risk of Complications With the Bactiguard Intramedullary Nail: Early to Medium Results With a Novel Metal-Coated Device

OBJECTIVES

The purpose of this study was to investigate the safety and early clinical results from the use of a novel, noble metal-coated titanium tibial nail for the definite stabilization of tibial shaft fractures at risk of developing complications.

DESIGN

This is a retrospective case series with prospectively collected data.

SETTING

Level I Trauma Centre in the United Kingdom.

PATIENTS AND INTERVENTION

Thirty-one patients who were managed with the Bactiguard-coated Natural Nail and achieved a minimum of a 12-month follow-up.

MAIN OUTCOME MEASUREMENTS

The main outcomes of this study were the incidence of adverse events (related to implant safety), complications (particularly infection), and reinterventions.

RESULTS

Thirty-one patients with a mean age of 41.6 years were included in this study. Active heavy smokers or intravenous drug users were 25.8% and 9.7% of them were diabetic. Five fractures were open while 13 had concomitant soft-tissue involvement (Tscherne grade 1 or 2). Twenty-seven patients healed with no further intervention in a mean time of 3.3 months. Three patients developed nonunion and required further intervention. The overall union rate was 96.7%. One patient developed deep infection after union (infection incidence 3.2%). Six patients (6/31; [19.3%]) required reinterventions [2 for the treatment of nonunion, 3 for removal of screws soft-tissue irritation, and 1 for the management of infection).

CONCLUSIONS

The management of tibial shaft fractures with a noble metal-coated titanium tibial nail demonstrates encouraging outcomes. Further studies are desirable to gather more evidence in the performance of this innovative implant.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Potential side effects of antibacterial coatings in orthopaedic implants: A systematic review of clinical studies

Objective: The systematic review aimed to determine the potential side effects of antibacterial coatings in orthopaedic implants. Methods: Publications were searched in the databases of Embase, PubMed, Web of Science and Cochrane Library using predetermined keywords up to 31 October 2022. Clinical studies reporting side effects of the surface or coating materials were included. Results: A total of 23 studies (20 cohort studies and three case reports) reporting the concerns about the side effects of antibacterial coatings were identified. Three types of coating materials, silver, iodine and gentamicin were included. All of studies raised the concerns regarding safety of antibacterial coatings, and the occurrence of adverse events was observed in seven studies. The main side effect of silver coatings was the development of argyria. For iodine coatings, only one anaphylactic case was reported as an adverse event. No systemic or other general side effects were reported for gentamicin. Conclusion: Clinical studies on the side effects of antibacterial coatings were limited. Based on the available outcomes, the most reported side effects of antibacterial coatings in clinical use were argyria with silver coatings. However, researchers should always pay attention to the potential side effects of antibacterial materials, such as systematic or local toxicity and allergy.

Silver-coated versus uncoated locking plates in subjects with fractures of the distal tibia: a randomized, subject and observer-blinded, multi-center non-inferiority study

BACKGROUND

Antimicrobial coatings of implants are of interest to reduce infection rate in orthopedic surgery. Demonstration of clinical effectiveness of such coated implants to obtain market approval is challenging. The objective of this article is to define a design for a randomized controlled trial to evaluate the clinical performance of a silver-coating for locking plates for fracture treatment.

METHODS

The study design has to respect different criteria, such as feasibility, focus on overall complications, such as functional impairment, fracture healing, and particularly on infection rates. Distal tibia fractures were chosen due to the high prevalence of infections in this type of injuries, which warrants a particular benefit of antimicrobial prophylaxis and thus might allow to see a statistical trend in favor of the coated product. The study design was defined as a randomized, controlled, subject and observer-blinded, multi-center study in subjects with fractures of the distal tibia with a total of 226 patients. A number of 113 patients are planned for each of the two treatment arms with treatment of the fracture with a silver-coated device (first arm) or with an uncoated device (second arm). Inclusion criteria are closed fractures of the distal tibia according to the Tscherne-Oestern classification or open fractures of the distal tibia according to the Gustilo-Anderson classification in subjects older than 18 years. Primary outcome parameter is the Anticipated Adverse Device Effects (AADE) including all typical complications of this type of injury, such as functional impairment of the affected limb, non-union, and infections based on a non-inferiority study design. Also, silver-typical complications, such as argyria, are included. Secondary parameters are infection rates and fracture healing. Follow-up of patients includes five visits with clinical and X-ray evaluations with a follow-up time of 12 months.

DISCUSSION

Demonstration of clinical effectiveness of antimicrobial coatings of fracture fixation devices remains a challenge. Definition of a prospective randomized pre-market trial design and recruitment of clinical sites for such a study is possible. A confirmative proof of the expected clinical benefit in terms of reduction of device-related infections will be addressed with a prospective post-market clinical follow-up study in a second step due to the large sample size required.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05260463. Registered on 02 March 2022.

Systemic Metal Ion Concentrations in Patients With Hip and Knee Megaprostheses: A Prospective Cohort Study

Background

Local tissue and serum metal ions have been shown to be elevated in some metal-on-metal and metal-on-polyethylene joint replacements. Local elevations have been linked to adverse local tissue reactions in some patients, and systemic elevation has been less commonly implicated cardiac and neurologic issues. Using a prospective study design, we aimed to identify the changes in serum metal ion levels after hip or knee megaprosthesis reconstruction. Furthermore, we will evaluate the occurrence of adverse effects and complications, possibly linked to metal ion elevation.

Methods

Fourteen consecutive patients receiving a Modular Universal Tumor Revision System megaprosthesis were enrolled. Blood samples were collected preoperatively and postoperatively to determine the serum ion concentrations of aluminum, chromium, cobalt, and silver. To evaluate the safety of the megaprostheses and the subsequently possible related (elevated) serum metal ion concentrations, all adverse effects and complications were registered until last outpatient clinic visit at the time of this study.

Results

Compared to the preoperative median serum concentrations, the postoperative median serum concentrations of chromium, silver, and cobalt increased 11-fold, 62-fold, and 64-fold, respectively. The median serum concentration of aluminum increased with 16%. Elevations were primarily noted in patients with knee prostheses. Eight patients had no adverse effects or complications during the period between preoperative and postoperative blood sampling. One adverse effect directly related to the serum metal ion concentrations, namely argyria, was observed.

Conclusions

This study documents significantly elevated concentrations of the metal ions, but only one adverse effect directly related to the metal ion concentrations was observed. Future studies are needed to further assess the impact of elevated metal ion levels after megaprostheses, specifically knee implants, which are metal-on-metal.

A concise review on implications of silver nanoparticles in bone tissue engineering

Skeletal disorders represent a variety of degenerative diseases that affect bone and cartilage homeostasis. The regenerative capacity of bone is affected in osteoporosis, osteoarthritis, rheumatoid arthritis, bone fractures, congenital defects, and bone cancers. There is no viable, non-invasive treatment option and bone regeneration requires surgical intervention with the implantation of bone grafts. Incorporating nanoparticles in bone grafts have improved fracture healing by providing fine structures for bone tissue engineering. It is currently a revolutionary finding in the field of regenerative medicine. Silver nanoparticles (AgNPs) have garnered particular attention due to their well-known anti-microbial and potential osteoinductive properties. In addition, AgNPs have been demonstrated to regulate the proliferation and differentiation of mesenchymal stem cells (MSCs) involved in bone regeneration. Furthermore, AgNPs have shown toxicity towards cancer cells derived from bone. In the last decade, there have been multiple studies focusing on the effect of nanoparticles on the proliferation and/or differentiation of MSCs and bone cancer cells; however, the specific studies with AgNPs are limited. Although the reported investigations show promising in vitro and in vivo potential of AgNPs for application in bone regeneration, more studies are required to ensure their implications in bone tissue engineering. This review aims to highlight the current advances related to the production of AgNPs and their effect on MSCs and bone cancer cells, which will potentiate their possible implications in orthopedics. Moreover, this review article evaluates the future of AgNPs in bone tissue engineering.

Long-term changes in serum silver concentrations after extremity reconstruction with silver-coated megaprostheses

Silver-coated megaprostheses are considered to reduce infection rate following reconstruction of bone defects in tumour surgery or revision arthroplasty. However, little is known about systemic silver exposure and possible side effects. The aim of this study was to analyse serum silver concentrations in patients with silver-coated megaprostheses over a prolonged time period. Between 2004 and 2016, 46 patients (52.2% female, mean age at surgery 47.1 ± 24.2 years) received silver-coated megaprostheses for septic (n = 26) or oncological (n = 17; main implant since 2013) indications, or aseptic loosening (n = 3). Blood was drawn from all patients within the first few days following surgery (without silver ion levels) and thereafter every 6 months at the outpatient department (with silver ion levels). Inductively coupled plasma mass spectrometry was used to determine silver ion levels. Median follow-up was 47.3 months (IQR: 16.1–78.9). Overall, 29 revision surgeries became necessary in 20 patients, equivalent to a cumulative complication rate of 63.0%. Revisions were most commonly for periprosthetic joint infections (PJIs, n = 12) and instability/soft tissue problems (n = 10). Revision-free implant survival was 81.4%, 42.3% and 35.2% at one, 5 and 10 years. Incidence of local argyria was 8.7% (n = 4). Silver ion levels at two or more consecutive time points during follow-up were available for 26 patients. An increment of silver levels within the first months (“run-in”) was observed, followed by an unspecific undulating course. Median initial and latest follow-up (median, 49.5 months) serum silver ion levels were 16.0 ppb (IQR: 9.1–29.1) and 7.4 ppb (IQR: 2.7–14.1), respectively. According to the multivariate mixed linear random-effects model, development of PJI was associated with significantly higher silver ion levels over time (p = 0.002), irrespective of time from surgery (p = 0.274). In the current series, a cumulative complication rate of 63.0% was observed for patients receiving silver-coated megaprostheses for septic of oncological indications. An overall unspecific course of silver ion concentration was present. Development of PJI was significantly associated with increased silver ion levels over time. Yet, no systemic complication associated to high silver levels occurred. It can be concluded that silver-coated implants constitute a safe solution for megaprosthetic reconstruction, but monitoring of silver concentrations is recommended.

Total femur replacement with 18 years of follow-up: A case report

BACKGROUND

Osteosarcoma is one of the most common primary malignant bone tumors and is more common in adolescents. The femur is the most common site of osteosarcoma, and many patients require total femur replacement. We reviewed the relevant literature and case findings, summarized and analyzed this case in combination with relevant literature, and in doing so improved the understanding of the technology.

CASE SUMMARY

The case we report was a 15-year-old patient who was admitted to the hospital 15 days after the discovery of a right thigh mass. The diagnosis was osteosarcoma of the right femoral shaft. After completion of neoadjuvant chemotherapy and preoperative preparation, total right femoral resection + artificial total femoral replacement was performed. Then, chemotherapy was continued after surgery. The patient recovered well after treatment, and the function of the affected limb was good. No recurrence, metastasis, prosthesis loosening, dislocation, fracture or other complications were found during 18 years of follow-up. At present, the patient can still work and lives normally. The results of the medium- and long-term follow-up were satisfactory.

CONCLUSION

Artificial total femur replacement is a feasible limb salvage operation for patients with femoral malignant tumors, and the results of medium- and long-term follow-up are satisfactory.

Treatment of an infected nonunion with additional fresh fracture of the femur with a silver-coated intramedullary nail: A case report

Infected non-unions of the femur can be difficult to treat with a high risk of reinfection and persisting nonunion. Here we demonstrate a case of a 66-year-old female with a chronic infected nonunion of the left femur. The patient fell during temporary external fixation of the infected nonunion and sustained an additional proximal femur shaft fracture. The case was successfully managed with a low-amount silver coating of a long proximal femur nail and an additional augmentation locking plate along with local and systemic antibiotics. After a follow-up of 26 months, both the fracture and also the infected nonunion healed completely without recurrence of infection and without any signs of adverse events in response to the silver coating. In conclusion, silver coated fracture fixation devices can be helpful in difficult to treat infection cases without adverse events.

Megaprosthesis anti-bacterial coatings: A comprehensive translational review

Periprosthetic joint infections (PJI) are catastrophic complications for patients with implanted megaprostheses and pose significant challenges in the management of orthopaedic oncology patients. Despite various preventative strategies, with the increasing rate of implanted orthopaedic prostheses, the number of PJIs may be increasing. PJIs are associated with a high rate of amputation. Therefore, novel strategies to combat bacterial colonization and biofilm formation are required. A promising strategy is the utilization of anti-bacterial coatings on megaprosthetic implants. In this translational review, a brief overview of the mechanism of bacterial colonization of implants and biofilm formation will be provided, followed by a discussion and classification of major anti-bacterial coatings currently in use and development. In addition, current in vitro outcomes, clinical significance, economic importance, evolutionary perspectives, and future directions of anti-bacterial coatings will also be discussed. Megaprosthetic anti-bacterial coating strategies will help reduce infection rates following the implantation of megaprostheses and would positively impact sarcoma care. STATEMENT OF SIGNIFICANCE: This review highlights the clinical challenges and a multitude of potential solutions to combating peri-prosthetic join infections in megaprotheses using anti-bacterial coatings. Reducing infection rates following the implantation of megaprostheses would have a major impact on sarcoma care and major trauma surgeries that require reconstruction of large skeletal defects.

Antibiotics- and Heavy Metals-Based Titanium Alloy Surface Modifications for Local Prosthetic Joint Infections

Prosthetic joint infection (PJI) is the second most common cause of arthroplasty failure. Though infrequent, it is one of the most devastating complications since it is associated with great personal cost for the patient and a high economic burden for health systems. Due to the high number of patients that will eventually receive a prosthesis, PJI incidence is increasing exponentially. As these infections are provoked by microorganisms, mainly bacteria, and as such can develop a biofilm, which is in turn resistant to both antibiotics and the immune system, prevention is the ideal approach. However, conventional preventative strategies seem to have reached their limit. Novel prevention strategies fall within two broad categories: (1) antibiotic- and (2) heavy metal-based surface modifications of titanium alloy prostheses. This review examines research on the most relevant titanium alloy surface modifications that use antibiotics to locally prevent primary PJI.

Distribution, metabolism, excretion, and toxicity of implanted silver: a review

Some implantable medical devices contain silver. We aimed to assess at what amount implanted silver becomes toxic. Silver was elevated in bodily fluids and tissues surrounding silver-containing implants. Silver released from implants also distributes to blood and other tissues; there is evidence to suggest silver can pass the blood-brain-barrier. Silver can be deposited as nano-sized particles in various tissues. Such particles, in addition to silver, often contain other elements too, e.g., selenium and sulfur. Silver released from implants seems to stay in the body for long periods (years). Reported excretion pathways following implantation are urinary and fecal ones. Reported toxicological effects were virtually all local reactions surrounding the implants. Argyria is a blue-gray discoloration of the skin due to deposited silver granules. Localized argyria has been described after the implantation of acupuncture needles and silver-coated prostheses, although the presence of silver was tested only for and shown in the former. Other toxicological effects include local tissue reactivity and examples of neurotoxic and vascular effects. We did not include genotoxicity studies in the present publication as we recently evaluated silver to be genotoxic. Carcinogenicity studies were absent. We conclude that local toxicity of implanted silver can be foreseen in some situations.

In vitro testing of silver-containing spacer in periprosthetic infection management

Deep infection is a serious complication in endoprosthetic surgery. In correlation to the patient local or systemic compromising factors conservative and surgical proceedings has to be evaluated. Systemic antibiotic therapy is the gold standard in infection management. Implanted silver-coated or silver-containing medical devices have been proven to their antimicrobial effectiveness since the 1990s by several investigators. The outcomes showed that long time implantation could cause damaging of the surrounding tissues, especially of adjacent nerves. The aim of our study was to evaluate the release of silver (I) ions from bone cement mixed with either nanosilver particles (AgNPs), different concentrations of silver sulfate (Ag2SO4) or from pure metallic silver strips. Therefore, we choose two methods: the first, called “static model”, was chosen to evaluate the maximal accumulative concentration of silver (I) ions, with the second, called “dynamic model”, we simulated a continuous reduction of the ions. In an additional test design, the different materials were evaluated for their antimicrobial activity using an agar gel diffusion assay. The outcome showed that neither the addition of 1% (w/w) nanosilver nor 0.1% silver sulfate (w/w) to polymethylmethacrylat bone cement has the ability to release silver (I) ions in a bactericidal/antifungal concentration. However, the results also showed that the addition of 0.5% (w/w) and 1% (w/w) silver sulfate (Ag2SO4) to bone cement is an effective amount of silver for use as a temporary spacer.

Exogenous pigmentation by silver nitrate: Dermatological and toxicological aspects, case report

La pigmentación exógena por nitrato de plata es una enfermedad poco frecuente, cuyas manifestaciones clínicas pueden aparecer años después del contacto, lo que en ocasiones dificulta su diagnóstico. Se caracteriza por la presencia de máculas o placas azul-grisáceas en la piel o las mucosas de la zona de contacto que, en ocasiones, son muy similares a las lesiones melanocíticas y al melanoma, sus principales diagnósticos diferenciales.

Se reporta el caso de un paciente de Medellín, Colombia, con antecedentes familiares de melanoma y presencia de estas lesiones en todo el cuerpo.

Clinical and Forensic Aspects of the Different Subtypes of Argyria

Argyria encompasses the different cosmetic alterations that can develop if enough silver particles deposit in a specific tissue, typically in the skin, ranging from localized dark-blue macules to a generalized slate-gray/bluish tinge following systemic absorption. This work aims to fully review the state of the art regarding pathophysiology, diagnosis, treatment, and relevant clinical and forensic features of argyria. Argyria has been diagnosed in a wide range of ages, both sexes and varied ethnicities, with no known individual predisposing factors. Ultraviolet radiation with subsequence increases of melanin production aggravates the discoloration due to a reduction in the silver deposits. Physical examination and silver exposure in the anamnesis can be highly suggestive of the diagnosis, but a histopathological analysis with Energy-Dispersive X-ray Spectroscopy is required to unequivocally determine the discoloration etiology. Safe and effective treatment has only been accomplished with laser techniques, though only a few cases have been reported and with limited follow-up time. In conclusion, argyria typically has an occupational or iatrogenic etiology. It should be suspected when a patient presents with typical skin or eye lesions. A seemingly viable treatment modality, with laser technology, is finally within the horizon.

The role of silver coating for arthroplasty components

Periprosthetic joint infection (PJI) is one of the most dreaded complications after arthroplasty surgery; thus numerous approaches have been undertaken to equip metal surfaces with antibacterial properties. Due to its antimicrobial effects, silver is a promising coating for metallic surfaces, and several types of silver-coated arthroplasty implants are in clinical use today. However, silver can also exert toxic effects on eukaryotic cells both in the immediate vicinity of the coated implants and systemically. In most clinically-used implants, silver coatings are applied on bulk components that are not in direct contact with bone, such as in partial or total long bone arthroplasties used in tumour or complex revision surgery. These implants differ considerably in the coating method, total silver content, and silver release rates. Safety issues, such as the occurrence of argyria, have been a cause for concern, and the efficacy of silver coatings in terms of preventing PJI is also controversial. The application of silver coatings is uncommon on parts of implants intended for cementless fixation in host bone, but this option might be highly desirable since the modification of implant surfaces in order to improve osteoconductivity can also increase bacterial adhesion. Therefore, an optimal silver content that inhibits bacterial colonization while maintaining osteoconductivity is crucial if silver were to be applied as a coating on parts intended for bone contact. This review summarizes the different methods used to apply silver coatings to arthroplasty components, with a focus on the amount and duration of silver release from the different coatings; the available experience with silver-coated implants that are in clinical use today; and future strategies to balance the effects of silver on bacteria and eukaryotic cells, and to develop silver-coated titanium components suitable for bone ingrowth. Cite this article: Bone Joint J 2021;103-B(3):423-429.

Silver-coated megaprosthesis in prevention and treatment of peri-prosthetic infections: a systematic review and meta-analysis about efficacy and toxicity in primary and revision surgery

AIM

Prosthetic joint infection (PJI) is a common complication following orthopedic megaprosthetic implantations (EPR), estimated up to 50%. Silver coatings were introduced in order to reduce the incidence of PJI, by using the antibacterial activity of silver. Three different silver coatings are available: MUTARS^® (Implantcast), Agluna^® (Accentus Medical), PorAg^® (Waldemar Link). The aim of this review is to provide an overview on efficacy and safety of silver-coated EPR both in primary and revision surgery, comparing infection rate according to the type of implant.

METHODS

Through an electronic systematic search, we reviewed the articles concerning silver-coated EPRs. Infection rate, silver-related complications, local and blood concentrations of the silver were evaluated. Meta-analyses were performed to compare results from each study included.

RESULTS

Nineteen studies were included. The overall infection rate in patients with silver-coated implants was 17.6% (133/755). Overall infection rate in primary silver-coated EPR was been 9.2% (44/445), compared to 11.2% (57/507) of non-silver-coated implants. The overall infection rate after revisions was 13.7% (25/183) in patients with silver-coated EPR and 29.2% (47/161) when uncoated EPR were used, revealing a strength statistically significative utility of silver coatings in preventing infections in this group (p: 0.019). Generally, the use of MUTARS^® EPR had produced an almost constant decrease in the incidence of primary PJI but there are few data on the effectiveness in revisions. The results from the use of Agluna^® in both primary and revisions implants are inconstant. Conversely, PorAg^® had proven to be effective both in PJI prevention but, especially, when used in PJI revision settings. Local argyria was reported in 8 out of 357 patients (2.2%), while no systemic complications were described. Local and blood concentrations of silver were always reported very far to the threshold of toxicity, with the lowest concentration found using PorAg^®.

CONCLUSIONS

Silver-coated EPRs are safe and effective in reduction in PJI and re-infection rate, in particular when used in higher risk patients and after two-stage revisions to fight PJI.

Efficacy of antimicrobial coated orthopaedic implants on the prevention of periprosthetic infections: a systematic review and meta-analysis

Introduction: Implant-associated infections are a major problem in orthopaedic surgery. Local delivery systems of antimicrobial agents on the implant surface have attracted great interest recently. The purpose of this study was to identify antimicrobial coatings currently used in clinical practice, examining their safety and effectiveness in reducing post-operative infection rates.

Materials and Methods: A systematic review was conducted in four databases (Medline, Embase, Cochrane, Cinahl) according to the Preferred Reporting Items for Systematic reviews and Meta-analysis (PRISMA) guidelines up to December 2019, using the key words “orthopaedic implant coated”, “coated implant infection”, “silver coating ” and “antibiotic coating”.

Results: Seven articles involving 1307 patients (561 with coated implants and 746 controls who were not) comparing the incidence of periprosthetic infections after the application of internal fracture fixation, total arthroplasties and endoprostheses were evaluated. Three different coating technologies were identified: gentamicin coating for tibia nail and total arthroplasties; silver technology and povidone-iodine coating for tumour endoprostheses and titanium implants. Meta-analysis demonstrated that patients who were treated with antimicrobial coated implants presented lower infection rates compared to controls over the seven studies (Q = 6.1232, I2 = 0.00, 95% CI: 1.717 to 4.986, OR: 2.926, Z= 3.949, p<0.001). Subgroup statistical analysis revealed that each coating technique was effective in the prevention of periprosthetic infections (Q = 9.2606, I2 = 78.40%, 95% CI: 1.401 to 4.070, OR: 2.388, Z= 3.200, p<0.001).

Conclusion: All technologies were reported to have good biocompatibility and were effective in the reduction of post-operative peri-prosthetic infection rates.

Silver-coated (PorAg®) endoprosthesis can be protective against reinfection in the treatment of tumor prostheses infection

INTRODUCTION

We aim to evaluate the use of silver (PorAg^®) coated compared to uncoated prosthesis in two-stage revision for prosthetic joint infection (PJI) of distal femur and proximal tibia megaprosthesis in oncological patients.

MATERIALS AND METHODS

In total, 68 patients were retrospectively evaluated. Median age was 30 years (range 14-83). In total, 29 patients were re-implanted with PorAg^® prosthesis and 39 with uncoated prosthesis (Megasystem C^®, Waldemar Link GmbH & Co. KG, Hamburg, Germany). All patients had PJI confirmed according to Musculoskeletal Infection Society (MSIS) criteria. In 10 cases, no microorganism was identified at the time of first-stage revision, but all had a sinus communicating with the prosthesis. Successful eradication of the infection was defined by the absence of clinical/serologic evidence of infection at 6 months after the second stage or at latest follow-up. Infection was again defined according to the MSIS criteria.

RESULTS

At 3-year follow-up, estimated reinfection rate in the silver group was slightly lower than in uncoated EPR (10.3% vs. 17.5%, p = 0.104). Among reinfected patients, only one out of three patients (33%) in the silver group required an amputation compared to 80% in the nonsilver group (p = 0.047).

CONCLUSIONS

Our results show the efficacy of PorAg^® coating in the two-stage revision of knee EPR. PorAg^®-coated EPR may have possible advantages over this traditional strategy, in particular when applied to patients with a higher risk of reinfection.

Antimicrobial silver-coating for locking plates shows uneventful osteotomy healing and good biocompatibility results of an experimental study in rabbits

Infections after internal fixation of fractures remain a challenge. Silver is known for its antimicrobial activity, including activity against multi-resistant strains. The aim of the current study was to analyze the biocompatibility and potential influence on the osteotomy healing process of a silver-coating technology for locking plates compared to silver-free locking plates in an established rabbit model. The implants used in this study were 7-hole titanium locking plates, and plasma electrolytic oxidation (PEO) silver-coated equivalents. A total of 24 rabbits were used in this study (12 coated, 12 non-coated). An osteotomy of the midshaft of the humerus was created and the humerus stabilized with the 7-hole locking plates with a total of 6 screws. Radiographs were taken on day 0, week 2, 4, 6, 8, and 10 for continuous radiographical evaluation. All animals were euthanized after 10 weeks and further assessment was performed using X-rays, micro-CT, non-destructive four-point bending biomechanical testing and semi-quantitative histopathological evaluation. Furthermore, silver concentration was measured in the blood, kidney, liver, spleen, brain, feces and soft tissue around the plate. Radiographs showed normal undisturbed and completed healing of the osteotomy in all animals without any differences between the two groups over the entire observation period. Micro-CT analysis revealed overall tissue volume as well as tissue density to be comparable between the two groups. Mechanical testing showed comparable stiffness with an average stiffness relative to contralateral bones of 75.7 ± 16.1% in the silver-free control group compared to 69.7 ± 18.5% (p-value: 0.46). Semi-quantitative histopathological evaluation showed no remarkable difference in the analysis of the osteotomy gap healing or in the surrounding soft tissue area. There were detectable silver concentrations in the soft tissue around the plate after 10 weeks. Silver in the blood was only found in 3 animals within the first two weeks and all animals were free of silver afterwards. There were no detectable silver concentrations in the brain, liver, spleen, axillary lymph nodes and kidney. This study shows undisturbed osteotomy healing of the presented antimicrobial silver surface coating and a good biocompatibility in this rabbit model.

Evidence-Based Recommendations for Local Antimicrobial Strategies and Dead Space Management in Fracture-Related Infection

Fracture-related infection (FRI) remains a challenging complication that imposes a heavy burden on orthopaedic trauma patients. The surgical management eradicates the local infectious focus and if necessary facilitates bone healing. Treatment success is associated with debridement of all dead and poorly vascularized tissue. However, debridement is often associated with the formation of a dead space, which provides an ideal environment for bacteria and is a potential site for recurrent infection. Dead space management is therefore of critical importance. For this reason, the use of locally delivered antimicrobials has gained attention not only for local antimicrobial activity but also for dead space management. Local antimicrobial therapy has been widely studied in periprosthetic joint infection, without addressing the specific problems of FRI. Furthermore, the literature presents a wide array of methods and guidelines with respect to the use of local antimicrobials. The present review describes the scientific evidence related to dead space management with a focus on the currently available local antimicrobial strategies in the management of FRI. LEVEL OF EVIDENCE:: Therapeutic Level V. See Instructions for Authors for a complete description of levels of evidence.

A retrospective study of antibacterial iodine-coated implants for postoperative infection

Postoperative infection is one of the most serious complications in orthopedic surgery. We have developed and use iodine-coated implants to prevent and treat postoperative infection in compromised hosts. This study evaluated outcomes using iodine-coated implants for postoperative infections.We treated 72 postoperative infected patients using iodine-coated implants. Of these, 38 were males and 34 were females, with a mean age of 59.3 years. The mean follow-up period was 5.6 years. The patients included 23 with an infection following total knee arthroplasty, 20 following total hip arthroplasty, 11 following osteosynthesis, 11 following spine surgery, 6 following tumor excision, and 1 following osteotomy. Of these, 37 underwent single-stage surgery and 35 underwent staged revision surgery. We performed staged surgery in any case with active infection. The survival of iodine-coated implants was determined using Kaplan-Meier analysis. White blood cell (WBC) and C-reactive protein (CRP) levels were measured pre- and postoperatively. To evaluate the systemic effects of iodine, serum thyroid hormone levels were examined.Five patients underwent re-revision surgery. In 3 patients, periprosthetic infection recurred at an average of 18 months after surgery. The reinfection rate was 4.2%. These patients recovered following reimplantation of iodine-coated prostheses. No patients required amputation. The survival rate of iodine-coated implants was 91%. There were no signs of infection at the latest follow-up. The median WBC level was nearly in the normal range, and CRP levels returned to normal within 4 weeks after surgery. No abnormalities of thyroid gland function were detected.Iodine-coated titanium implants can be very effective in the treatment of postoperative infections. An iodine coating can be safely applied to infected regions.

Safety assessment of microsilver-loaded poly(methyl methacrylate) (PMMA) cement spacers in patients with prosthetic hip infections: Results of a prospective cohort study

Objectives

Preclinical data showed poly(methyl methacrylate) (PMMA) loaded with microsilver to be effective against a variety of bacteria. The purpose of this study was to assess patient safety of PMMA spacers with microsilver in prosthetic hip infections in a prospective cohort study.

Methods

A total of 12 patients with prosthetic hip infections were included for a three-stage revision procedure. All patients received either a gentamicin-PMMA spacer (80 g to 160 g PMMA depending on hip joint dimension) with additional loading of 1% (w/w) of microsilver (0.8 g to 1.6 g per spacer) at surgery 1 followed by a gentamicin-PMMA spacer without microsilver at surgery 2 or vice versa. Implantation of the revision prosthesis was carried out at surgery 3.

Results

In total, 11 of the 12 patients completed the study. No argyria or considerable differences in laboratory parameters were detected. Silver blood concentrations were below or around the detection limit of 1 ppb in ten of the 11 patients. A maximum of 5.6 ppb at 48 hours after implantation of the silver spacer, which is below the recommended maximum level of 10 ppb, was found in one patient. No silver was detected in the urine. Drainage fluids showed concentrations between 16.1 ppb and 23.3 ppb at 12 hours after implantation of the silver spacers, and between 16.8 ppb to 25.1 ppb at 48 hours after implantation. Pathohistological assessment of the periprosthetic membrane did not reveal any differences between the two groups.

Conclusion

Microsilver-loaded gentamicin-PMMA spacers showed good biocompatibility and the broad antimicrobial activity warrants further clinical research to assess its effectivity in reducing infection rates in prosthetic joint infection.Cite this article: V. Alt, M. Rupp, K. Lemberger, T. Bechert, T. Konradt, P. Steinrücke, R. Schnettler, S. Söder, R. Ascherl. Safety assessment of microsilver-loaded poly(methyl methacrylate) (PMMA) cement spacers in patients with prosthetic hip infections: Results of a prospective cohort study. Bone Joint Res 2019;8:387-396. DOI: 10.1302/2046-3758.88.BJR-2018-0270.R1.

Is surface modification effective to prevent periprosthetic joint infection? A systematic review of preclinical and clinical studies

BACKGROUND

With increasing recognition of the importance of biofilm formation in the pathogenesis of periprosthetic joint infection (PJI), a push towards finding solutions to prevent PJI via surface modification of prostheses is occurring. Unlike the promising in vitro antimicrobial effects of these surface modifications, the preclinical and clinical prophylactic effects vary and are debated. Therefore, we performed this systematic review to answer: (1) what kinds of methods of surface modification are used in preclinical and clinical studies to prevent PJI, (2) whether these modifications are effective to prevent PJI.

METHODS

Electronic searches were performed using PubMed, Embase and the Cochrane library databases up to and including December 2017 with predetermined criteria: (1) in vivo studies with (2) surface modification for prophylactic effects against infection. Both animal studies and clinical trials were included. Data were extracted and presented systematically.

RESULTS

Overall, 21 studies were included. Among these, fourteen were carried out in animal models and seven were clinical studies. In the animal studies, six used antibiotics and six silver modifications, while copper and Cationic Steroidal Antimicrobial-13 were each used for one study. In the seven clinical studies targeting patients with high infection risk, five of them focused on silver-coated prostheses and the remaining two studied iodine-coated implants. In all of the animal studies, when compared with the control group, the surface modified groups had a lower infection risk (RR ranging from 0 to 0.71). Clinical studies using silver-coated prostheses also demonstrated a lower infection risk (RR ranging from 0.24 to 0.70), while iodine-coated implants showed a 0% and 5% incidence of PJI in the two case series included.

DISCUSSION

The results from the publications included in this review indicate that surface modification, especially antibiotic and silver modifications, are helpful preventing PJI in both preclinical animal models and in clinical trials.

LEVEL OF EVIDENCE

III, systematic review of level III retrospective comparative studies and level IV case series and animal experiments.

Treatment of a Recurrent Periprosthetic Joint Infection with an Intramedullary Knee Arthrodesis System with Low-Amount Metallic Silver Coating

We present a case of a recurrent periprosthetic knee infection treated with an intramedullary arthrodesis system coated with low amounts of metallic silver. After a follow-up of 26 months, the patient remained infection free and no silver-related complications were detected. Silver serum concentrations remained below the detection limit of 2 ppb.

[Silver coating on tumour prostheses]

BACKGROUND

Modular endoprostheses, so-called "tumour or megaprostheses" are mainly used for limb salvage surgery after resection of malignant soft tissue or a bone tumour. Sometimes, this type of prosthesis is also used for revision surgeries after failed primary joint arthroplasty. Despite continuously improving techniques and quality management systems, periprosthetic infection is one of the most serious complications.

AIM OF THE STUDY

Review of the literature in the PubMed data base with the main focus on silver coatings in joint arthroplasty and their effect on infection rate, outcome and patients' safety.

RESULTS

The current literature shows that there is a beneficial role of silver coatings in megaprostheses in terms of revision rates for septic complications, especially following tumour resection with bad soft tissue coverage or in (multimorbid) high-risk patients, compared to uncoated implants.

DISCUSSION

Based on the results of previous publications examining blood or serum silver concentrations or silver levels in urine, silver coatings do not appear to have side effects, except for local argyria. Continuous monitoring of silver levels in blood or serum is still recommended, and additional long-term studies will be necessary to verify the effectiveness and safety of silver coatings.

The use of silver coating in hip megaprostheses: a systematic review

Retrospective studies of silver-coated hip implants have demonstrated promising results and safety profile, however, the potential benefits are so far unproven in prospective studies. Silver-coated implants may have a role in patients undergoing revision or primary surgery with a high risk of infection but as yet there are no human studies investigating silver in primary hip arthroplasty. Adequately powered robust prospective studies are needed in this area to determine if silver-coated implants would be efficacious and cost-effective. The purpose of this systematic review article is to review the current literature regarding the use of silver in hip arthroplasty. Our review showed that there is some encouraging evidence that silver coatings can reduce infection.

Silver-coated (Agluna®) tumour prostheses can be a protective factor against infection in high risk failure patients

INTRODUCTION

Endoprostheses in the treatment of extremity sarcomas are associated with late complications including periprosthetic infection. This study analysed the incidence of infection in patients undergoing endoprosthetic replacement (EPR) with a silver-coated prosthesis.

MATERIALS AND METHODS

The study comprised a retrospective single centre study of 394 consecutive patients treated with resection and EPR for primary extremity bone tumours.

RESULTS

89 patients at risk for infection were treated with a silver-coated (Agluna®) EPR (22.6%), compared to 305 patients treated with a non-silver EPR (77.4%). The incidence of periprosthetic infection, requiring revision as the primary endpoint was 34/394 (8.6%); 11 patients (12.4%) in the silver group and 23 patients (7.5%) in the non-silver group (p = 0.154). Overall implant survival was 90.9% and 95.3% at 1-year and 86.8% and 91.8% at 5-years in the silver-coated and non-silver coated group, respectively (p = 0.193). Infection was treated in the silver group by washout of the prosthesis in 2/11, debridement and implant retention (DAIR) in 1/11 and single-stage revision in 1/11, and in the non-silver group by washout in 1/23 or DAIR in 2/23. Two-stage revision was successful in 2/11in the silver group, and in 11/23 in the non-silver group. Amputation was required in 4/11 in the silver group and 9/23 in the non-silver group. One patient in the silver group died due to disease with an infected EPR.

CONCLUSIONS

Silver-coated prostheses in high risk patients show similar infection free survival as non-silver coated prosthesis in standard sites in primary bone tumours of the extremities.

[Advances in total femur replacement]

Objective

To summarize the advances of total femur replacement in recent years.

Methods

The literature related to total femur replacement was reviewed, and the indications, techniques, prosthesis design, complications, rehabilitation, and function were summarized.

Results

The indication of total femur replacement is a wide involvement of the femur, skip lesions and a huge bone defect in revision. Watson-Jone is the main incision in the proximal, and then the full length of the thigh to the patella. Vascular and nerve bundle, abduction muscles are well protected, and combined or costumed prosthesis are replaced. The prosthesis design progresses, showing a diversified prostheses. Complication is frequent and varied. Rehabilitation in early stage is physical therapy, weight training is evolutionary. The main function evaluation system is Musculoskeletal Tumor Society (MSTS) score.

Conclusion

Total femur replacement is effective in limb salvage. Large sample size and long-term follow-up study should be carried out to unify indications and functional exercise standards and reduce postoperative complications.

Coatings as the useful drug delivery system for the prevention of implant-related infections

Implant-related infections (IRIs) which led to a large amount of medical expenditure were caused by bacteria and fungi that involve the implants in the operation or in ward. Traditional treatments of IRIs were comprised of repeated radical debridement, replacement of internal fixators, and intravenous antibiotics. It needed a long time and numbers of surgeries to cure, which meant a catastrophe to patients. So how to prevent it was more important than to cure it. As an excellent local release system, coating is a good idea by its local drug infusion and barrier effect on resisting biofilms which were the main cause of IRIs. So in this review, materials used for coatings and evidences of prevention were elaborated.

Tibia Adamantinoma Resection and Reconstruction with a Custom-Made Total Tibia Endoprosthesis: A Case Report with 8-Year Follow-Up

This case study describes a total tibia resection and reconstruction with a custom-made endoprosthetic replacement (EPR) and a long-term, 8-year follow-up. The patient underwent a total tibia adamantinoma resection in 2009. Reconstruction was performed with a custom-made total tibia EPR, where both the knee joint and ankle joint were reconstructed. Two muscle flaps, latissimus dorsi free flap and a pedicled medial gastrocnemius flap, were used for soft tissue reconstruction. The patient returned to normal life as a kindergarten teacher, without complications for eight years. This case demonstrated the importance of successful multidisciplinary teamwork in close collaboration with industry. In our best knowledge, no over 2 years of follow-up of total tibia replacement reports have been published.

Silver-Coated Megaprosthesis of the Proximal Tibia in Patients With Sarcoma

BACKGROUND

Proximal tibia arthroplasty is associated with high rates of infection. This study is the largest one that has compared the infection rates with titanium vs silver-coated megaprostheses in patients treated for sarcomas.

METHODS

The infection rate in 98 patients with sarcoma or giant-cell tumor in the proximal tibia who underwent placement of a titanium (n = 42) or silver-coated (n = 56) megaprosthesis (MUTARS) was assessed, along with the treatments administered for any infection.

RESULTS

As the primary end point of the study, the rates of infection were 16.7% in the titanium group and 8.9% in the silver group, resulting in 5-year prosthesis survival rates of 90% in the silver and 84% in the titanium group. Whereas in the titanium group 37.5% of patients ultimately had to undergo amputation in the present study, these mutilating surgical procedures were only necessary in the silver group in one patient (14.3%).

CONCLUSION

The use of silver-coated prosthesis reduced the infection rate in a relatively large and homogeneous group of patients. In addition, less-aggressive treatment of infection was possible in the group with silver-coated prosthesis.

Silver-coated megaprostheses: review of the literature

Periprosthetic infection remains one of the most serious complications following megaendoprostheses. Despite a large number of preventive measures that have been introduced in recent years, it has not been possible to further reduce the rate of periprosthetic infection. With regard to metallic modification of implants, silver in particular has been regarded as highly promising, since silver particles combine a high degree of antimicrobial activity with a low level of human toxicity. This review provides an overview of the history of the use of silver as an antimicrobial agent, its mechanism of action, and its clinical application in the field of megaendoprosthetics. The benefits of silver-coated prostheses could not be confirmed until now. However, a large number of retrospective studies suggest that the rate of periprosthetic infections could be reduced by using silver-coated megaprostheses.

Antimicrobial coated implants in trauma and orthopaedics-A clinical review and risk-benefit analysis

Implant-associated infections remain a major issue in orthopaedics and antimicrobial functionalization of the implant surface by antibiotics or other anti-infective agents have gained interest. The goal of this article is to identify antimicrobial coatings, for which clinical data are available and to review their clinical need, safety profile, and their efficacy to reduce infection rates. PubMed database of the National Library of Medicine was searched for clinical studies on antimicrobial coated implants for internal fracture fixation devices and endoprostheses for bone surgery, for which study design, level of evidence, biocompatibility, development of resistance, and effectiveness to reduce infection rates were analyzed. Four different coating technologies were identified: gentamicin poly(d, l-lactide) coating for tibia nails, one high (MUTARS^®) and one low amount silver (Agluna) technology for tumor endoprostheses, and one povidone-iodine coating for titanium implants. There was a total of 9 published studies with 435 patients, of which 7 studies were case series (level IV evidence) and 2 studies were case control studies (level III evidence). All technologies were reported with good systemic and local biocompatibility, except the development of local argyria with blue to bluish grey skin discoloration after the use of silver MUTARS^® megaendoprostheses. For the local use of gentamicin, there is contradictory data on the risk of emergence of gentamicin-resistance strains, a risk that does not seem to exist for silver and iodine based technologies. Regarding reduction of infection rates, one case control study showed a significant reduction of infection rates by Agluna silver coated tumor endoprostheses. Based on socio-economic data, there is a strong need for improvement of infection prevention and treatment strategies, including implant coatings, in fracture care, primary and revision arthroplasty, and bone tumor surgery. The reviewed gentamicin, silver Agluna, and povidone-iodine technologies have shown a good risk benefit ratio for patients. Further data from randomized control trials are desirable, although this will remain challenging in the context of infection prevention due to the required large sample size of such studies.

Antibacterial and Biocompatible Titanium-Copper Oxide Coating May Be a Potential Strategy to Reduce Periprosthetic Infection: An In Vitro Study

BACKGROUND

Periprosthetic infections are devastating for patients and more efficacious preventive strategies are needed. Surface-modified implants using antibacterial coatings represent an option to cope with this problem; however, manufacturing limitations and cytotoxicity have curbed clinical translation. Among metals with antibacterial properties, copper has shown superior in vitro antibacterial performance while maintaining an acceptable cytotoxicity profile. A thin film containing copper could prevent early biofilm formation to limit periprosthetic infections. This pilot study presents the in vitro antibacterial effect, cytotoxicity, and copper ion elution pattern of a thin film of titanium-copper oxide (TiCuO).

QUESTIONS/PURPOSES

(1) Do titanium alloy (Ti6Al4V) discs coated with a thin film of TiCuO reduce Staphylococcus epidermidis biofilm and planktonic cell density compared with uncoated discs? (2) Do Ti6Al4V discs coated with a thin film of TiCuO affect normal human osteoblast viability compared with untreated cells? (3) Is copper ion concentration generated by coated discs lower than previously published copper ion concentrations that cause 50% toxicity in similar human cell lines in vitro (TC50)?

METHODS

Ninety Ti6Al4V discs (12.5 mm diameter; 1.25 mm thick) were used in this study. Seventy-two Ti6Al4V discs were coated with a thin film of either titanium oxide (TiO) or TiCuO containing 20%, 40%, or 80% copper using high-power impulse magnetron sputtering (HiPIMS). Eighteen Ti6Al4V discs remained uncoated for control purposes. We tested antibacterial properties of S epidermidis grown on discs in wells containing growth medium. After 24 hours, planktonic bacteria as well as biofilms removed by sonication were quantitatively cultured. Annexin/Pi staining was used to quantify in vitro normal human osteoblast cell viability at 24 hours and Day 7, respectively. Copper elution was measured at Days 1, 2, 3, 7, 14, and 28 using an inductively coupled plasma mass spectrometer to analyze aliquots of culture medium. Copper ion concentration achieved at 24 hours was compared with previously published TC50 for gingival fibroblast, a phenotypically similar cell line with available data regarding copper ion exposure.

RESULTS

Discs coated with TiCuO 80% copper showed greater biofilm and planktonic cell density reduction when compared with other tested compositions (analysis of variance [ANOVA]; p < 0.001). Discs coated with TiCuO 80% copper showed mean biofilm and planktonic cell density of 4.0 log₁₀ (SD = 0.4) and 5.7 log₁₀ (SD = 0.2). Discs coated with TiCuO 80% showed a mean difference in biofilm and planktonic cell density of 2.5 log₁₀ (95% confidence interval [CI], 1.9-3.1 log_10; p < 0.001) and 1.2 (95% CI, 0.6-1.8; p < 0.001), respectively, when compared with uncoated discs. Normal human osteoblast viability did not differ among all groups at 24 hours (ANOVA; p = 0.2) and Day 7 (ANOVA; p = 0.7). Discs coated with TiCuO 80% copper showed a mean difference (95% CI) in relative cell viability (%) at 24 hours and Day 7 of 31.1 (95% CI, -19.4 to 81.7; p = 0.4) and -5.0 (95% CI, -7.8 to 17.9; p = 0.9), respectively, when compared with untreated cells. For all TiCuO-coated discs, copper ion elution peaked at 24 hours and slowly decreased in a curvilinear fashion to nearly undetectable levels by Day 28. Discs coated with TiCuO 80% copper showed mean copper ion concentration at 24 hours of 269.4 µmol/L (SD = 25.2 µmol/L) and this concentration was lower than previously published TC50 for similar human cell lines at 24 hours (344 µmol/L, SEM = 44 µmol/L).

CONCLUSIONS

This pilot study demonstrates a proof of concept that a thin-film implant coating with TiCuO can provide a potent local antibacterial environment while remaining relatively nontoxic to a human osteoblast cell line. Further research in an animal model will be necessary to establish efficacy and safety of this technique and whether it might be useful in the design of implants.

CLINICAL RELEVANCE

A thin film coating with TiCuO demonstrates high antibacterial activity and low cellular cytotoxicity to human osteoblasts in vitro. Taken together, these properties represent a potential strategy for preventing periprosthetic infection if further work in animal models can confirm these results in vivo.

Levels of silver ions in body fluids and clinical results in silver-coated megaprostheses after tumour, trauma or failed arthroplasty

INTRODUCTION

Infection in megaprostheses remains an unsolved problem, with a rate of occurrence ranging from 5% to 12%. Silver coating of medical devices has recently been proposed to reduce infection rate because of the antibacterial effect of silver. This innovation could be particularly interesting for megaprostheses, but few data have been reported in the literature.

MATERIALS AND METHODS

From June 2010 to August 2014 a modified MegaC System megaprosthesis with an innovative peripheral silver-added layer of titanium alloy ('Porag') was implanted in 33 patients after previous infection (21 patients) or at high risk for infection because of local or general conditions (12 patients). Previous infection followed megaprosthesis or standard arthroplasty procedures in 14 patients and trauma surgery in seven patients. A proximal femur replacement was performed in 13 patients, distal femur replacement in 13, total femur in one, and knee arthrodesis in six. Clinical results and levels of silver in blood, urine and wound drains were examined.

RESULTS

Minimum follow-up of the patients was one year (average 25.9 months). There was no infection during the first two years after surgery in the 12 patients who received a silver-coated megaprosthesis and had no previous history of infection. An infection developed in one patient at 25 months after surgery following two further surgical procedures. Infection recurred at seven months and 24 months in two out of the 21 patients (9.5%) who had received the implant because of previous septic complications. There was no clinical evidence of argyria, and no local or systemic side effects related to silver were detected. Mean levels of silver ranging from 0.41 to 5.33μg/L in blood and from 0.28 to 0.86μg/L in urine were detected at 24h to 36 months after surgery.

CONCLUSIONS

Silver-coated megaprostheses showed promising results in this series in terms of prevention of infection in a high-risk group of patients, many of whom had a history of infection. No side-effects were detected. The circulating silver levels confirm both the persistence of silver-coating activity after three years and the safety of silver-coated implants. Longer follow-up and larger series are needed.

Silver-Coated Hip Megaprosthesis in Oncological Limb Savage Surgery

Silver coating has demonstrated good antimicrobial activity and low toxicity. Silver-coated megaprostheses have been introduced in oncological musculoskeletal surgery considering the high rate of infection. We conducted a retrospective analysis on 68 cases of primary or metastatic bone tumors, affecting the proximal femur, treated between 2005 and 2016 with wide margins resection and tumor implants reconstruction. All patients were treated by the same surgeon, with antibiotic prophylaxis according to a standard protocol. In 55.9% of patients silver-coated hip hemiarthroplasty was implanted; in the remaining 44.1% uncoated megaprostheses were implanted. Patients were reevaluated recording the complications and focusing the analysis on infective complications. The average follow-up was 46.5 months. No patient has shown any sign of local or general silver toxicity. A SEM analysis was conducted on the 3-silver-coated hip hemiarthroplasty explanted confirming a severe degradation with a small amount of residual silver on the coating surface. Silver-coated hip prostheses have a lower rate of early infection than traditional implants but showed a reduction of antimicrobial activity for silver coating wear. We recommend using silver-coated prosthesis as primary implants for limb salvage surgery, in primary or metastatic bone tumors affecting the proximal femur, considering the absence of signs of toxicity and the lower rate of early infection.

Current concepts in total femoral replacement

Total femoral replacement (TFR) is a salvage arthroplasty procedure used as an alternative to lower limb amputation. Since its initial description in the mid-20^th century, this procedure has been used in a variety of oncologic and non-oncologic indications. The most compelling advantage of TFR is the achievement of immediate fixation which permits early mobilization. It is anticipated that TFR will be increasingly performed as the rate of revision arthroplasty rises worldwide. The existing literature is mainly composed of a rather heterogeneous mix of retrospective case series and a wide assortment of case reports. Numerous TFR prostheses are currently available and the surgeon must understand the unique implications of each implant design. Long-term functional outcomes are dependent on adherence to proper technique and an appropriate physical therapy program for postoperative rehabilitation. Revision TFR is mainly performed for periprosthetic infection and the severe femoral bone loss associated with aseptic revisions. Depending on the likelihood of attaining infection clearance, it may sometimes be advisable to proceed directly to hip disarticulation without attempting salvage of the TFR. Other reported complications of TFR include hip joint instability, limb length discrepancy, device failure, component loosening, patellar maltracking and delayed wound healing. Further research is needed to better characterize the long-term functional outcomes and complications associated with this complex procedure.

The management of periprosthetic infections in the future: a review of new forms of treatment

The number of arthroplasties being undertaken is expected to grow year on year, and periprosthetic joint infections will be an increasing socioeconomic burden. The challenge to prevent and eradicate these infections has resulted in the emergence of several new strategies, which are discussed in this review. Cite this article: Bone Joint J 2015;97-B:1162-9.

[Antimicrobial prosthesis coatings]

BACKGROUND

Antimicrobial coatings have a great potential in the treatment and prevention of periprosthetic joint infection.

OBJECTIVE

To present established and novel concepts of antimicrobial coatings.

METHODS

A literature review and discussion of published concepts in basic research, pre-clinical animal studies, and clinical practice were carried out.

RESULTS

To date there has been a wide range of technical solutions (anti-adhesive surfaces, bioactive surfaces with antimicrobial effects, surfaces releasing antimicrobial substances, nanostructures, bioactive surfaces affecting biofilm development) demonstrating a high potential in pre-clinical studies. Only a few with the bactericidal activity of silver ions have been prepared for the market. Conclusive results with regard to biocompatibility and toxicity are lacking.

DISCUSSION

Despite the great potential of antimicrobial coatings, no conclusive decisions can be made because of the limited data and the lack of evidence of their clinical efficacy on the basis of prospective controlled clinical studies. In addition to their unlimited biocompatibility, innovative concepts have to be feasible in everyday clinical routine.

Retrospective evaluation of the incidence of early periprosthetic infection with silver-treated endoprostheses in high-risk patients: case-control study

We conducted a case-control study to examine the merit of silver-coated tumour prostheses. We reviewed 85 patients with Agluna-treated (silver-coated) tumour implants treated between 2006 and 2011 and matched them with 85 control patients treated between 2001 and 2011 with identical, but uncoated, tumour prostheses. In all, 106 men and 64 women with a mean age of 42.2 years (18.4 to 90.4) were included in the study. There were 50 primary reconstructions (29.4%); 79 one-stage revisions (46.5%) and 41 two-stage revisions for infection (24.1%). The overall post-operative infection rate of the silver-coated group was 11.8% compared with 22.4% for the control group (p = 0.033, chi-square test). A total of seven of the ten infected prostheses in the silver-coated group were treated successfully with debridement, antibiotics, and implant retention compared with only six of the 19 patients (31.6%) in the control group (p = 0.048, chi-square test). Three patients in the silver-coated group (3.5%) and 13 controls (15.3%) had chronic periprosthetic infection (p = 0.009, chi-square test). The overall success rates in controlling infection by two-stage revision in the silver-coated group was 85% (17/20) compared with 57.1% (12/21) in the control group (p = 0.05, chi-square test). The Agluna-treated endoprostheses were associated with a lower rate of early periprosthetic infection. These silver-treated implants were particularly useful in two-stage revisions for infection and in those patients with incidental positive cultures at the time of implantation of the prosthesis. Debridement with antibiotic treatment and retention of the implant appeared to be more successful with silver-coated implants.

Evaluation of osseous integration of PVD-silver-coated hip prostheses in a canine model

Infection associated with biomaterials used for orthopedic prostheses remains a serious complication in orthopedics, especially tumor surgery. Silver-coating of orthopedic (mega)prostheses proved its efficiency in reducing infections but has been limited to surface areas exposed to soft tissues due to concerns of silver inhibiting osseous integration of cementless stems. To close this gap in the bactericidal capacity of silver-coated orthopedic prostheses extension of the silver-coating on surface areas intended for osseous integration seems to be inevitable. Our study reports about a PVD- (physical-vapor-deposition-) silver-coated cementless stem in a canine model for the first time and showed osseous integration of a silver-coated titanium surface in vivo. Radiological, histological, and biomechanical analysis revealed a stable osseous integration of four of nine stems implanted. Silver trace elemental concentrations in serum did not exceed 1.82 parts per billion (ppb) and can be considered as nontoxic. Changes in liver and kidney functions associated with the silver-coating could be excluded by blood chemistry analysis. This was in accordance with very limited metal displacement from coated surfaces observed by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) 12 months after implantation. In conclusion our results represent a step towards complete bactericidal silver-coating of orthopedic prostheses.