Periprothetische Infektion

Advantages in orthopaedic implant infection diagnostics by additional analysis of explants

PURPOSE

Implant-associated infections are the most challenging complication in orthopaedics and trauma surgery as they often lead to long courses of illness and are a financial burden for the healthcare system. There is a need for fast, simple, and cheap identification of pathogens but the ideal detection method was not found yet. The work aims to test whether the detection of pathogens culturing the removed implant is more successful than from simultaneously taken tissue samples or punction fluid.

METHODS

Implants were removed due to infection, irritation, or loosening. Tissue samples and joint fluids were processed for bacterial growth in sterile conditions. Samples were incubated and checked for growth. Bacterial identification and antibiotic sensitivity testing were performed. Data were anonymized, and statistical analysis was done using Excel and SAS, employing tests like Shapiro-Wilk, Mann-Whitney-U, and Kruskal-Wallis. Ethical approval was obtained for this study.

RESULTS

Between February 2018 and April 2019, a total of 163 patients (175 cases) underwent orthopaedic implant removal for various reasons. 30 cases were not usable or analyzable due to missing or damaged reference material, so 145 cases could be evaluated due to study protocol. The range of detected bacteria was as expected and included low-virulent bacteria such as Micrococcus luteus and Corynebacteria. Pathogen detection by culture of the the explant´s was more sensitive (84.83%) than pathogen detection from tissue samples and punction fluid (64.14%, p<0.0001). Comorbidities did not play any role in the quality of detection but prior antibiotic treatment did influence the results of tissue diagnostics.

CONCLUSION

This study showed with a higher frequency of bacterial detection of orthopedic explant´s surface compared to tissue samples or punction fluid. This may reduce the number of samples and cost but enhances the quality of orthopaedic implant-related infection diagnostics.

Epidemiology of traumatic injuries and associated infectious complications in the Republic of Kazakhstan

Traumatism is one of the most important contemporary medical and social issues for most countries worldwide. Since the 20^th century, the urgency of traumatism has been increasing. There was an increase in fatal traumatism, including non-fatal cases resulting in permanent disability or temporary disability. This study aimed to investigate the epidemiology of injuries in the Republic of Kazakhstan and identify the statistical patterns of surgical treatment. Furthermore, this study aimed to identify the incidence of infectious complications in patients who received trauma and orthopedic care, their structure and dynamics, and compare this data with the literature. From 2017 to 2019, there were more upper and lower extremity injuries in the Republic of Kazakhstan in the age group of 15-17 years, which corresponds to Russian statistics. Of the 10 injuries, one in three undergoes surgical intervention. In two large cities, Nur-Sultan and Almaty, surgical interventions are performed more often than in other regions. The most frequent infectious complication associated with traumatism is osteomyelitis, with the most causative species being staphylococci.

Low Diagnostic Value of Synovial Aspiration Culture Prior to Reimplantation in Periprosthetic Joint Infection

BACKGROUND/AIM

We aimed to determine the diagnostic value of the synovial aspiration culture prior to reimplantation in two- (or more) stage exchange of periprosthetic joint infection.

PATIENTS AND METHODS

This was a retrospective study, spanning over ten years including all synovial cultures of patients with two- (or more) stage exchange due to periprosthetic joint infection.

RESULTS

A total of 183 patients were included, mean age was 66.6 years (range=12.8-93.4 years). Overall sensitivity of synovial aspiration cultures before reimplantation was 56.6%, specificity 84.6%, negative predictive value (NPV) 63.8%, positive predictive value (PPV) 80.2%, area under the curve (AUC) 70.6%. Sensitivity of the knee in comparison to the hip culture was significantly higher, as well as the NPV and the AUC (p=0.038). In case of complete removal of prosthesis, the sensitivity and AUC were significantly reduced, whereas the specificity was comparable with prosthesis in situ, partial removal or complete removal.

CONCLUSION

Due to the low sensitivity, obtaining several synovial cultures in the prosthesis-free interval to exclude persistence of infection, does not seem reasonable.

Chylomicronemia Mimicking an Infection During Emergent Fracture Surgery: A Case Report

CASE

A 36-year-old patient with chronic alcohol abuse and previous medical history of total hip arthroplasty suffered a fracture of the femoral shaft. During osteosynthesis, a milky fluid similar to purulent discharge emerged at multiple locations. Immediate Gram stains were negative, and the surgery was performed as planned. Laboratory tests showed massive elevated levels of triglycerides. During further workup, chylomicronemia syndrome was diagnosed.

CONCLUSION

This case report shows that chylomicronemia syndrome can have an appearance during surgery similar to a purulent infection. Immediate Gram stains and laboratory work can identify the reason.

Persistent Fistula for Treatment of a Failed Periprosthetic Joint Infection: Relic From the Past or a Viable Salvage Procedure?

BACKGROUND

New treatment algorithms for periprosthetic joint infections (PJIs) show high success rates in achieving permanent infection eradication with some degree of failure. Different salvage procedures are described, but there is no evidence for persistent fistula (PF). The purpose of this study was to analyze PF as a salvage procedure in patients with therapy-resistant PJIs.

METHODS

This retrospective analysis included all patients treated with PF (2005-2018) in a maximum care center with PJI (knee or hip). The baseline parameters (age, sex, BMI) and other data (number of surgeries, pathogen spectrum, American Society of Anesthesiologists classification) were recorded. The function was documented using the Harris Hip Score, the Knee Society Score, and the quality of life using the SF-36 Health Survey.

RESULTS

A total of 159 patients were included (80 ± 12 years) and subdivided into four groups: hip (n = 66), knee (n = 13), Girdlestone resection arthroplasty (n = 50), knee arthrodesis (n = 27). Patients stayed 111 ± 87 days in the hospital, underwent six operations and three revisions after establishing PF. The mean American Society of Anesthesiologists score was 2.7. The BMI was 31 ± 3 kg/m² (P = .1). The follow-up was 2.8 ± 0.5 years including 27 patients. The Harris Hip Score and Knee Society Score were 38 and 34, respectively. SF-36 showed no significant difference.

CONCLUSION

The study showed poor outcomes regarding quality of life and the function of the infected joint. Therefore, the indication for establishing a PF in the treatment of PJI must be assessed very critically. PF is only an option for multimorbid patients with a limited life expectancy.

Efficacy of different revision procedures for infected megaprostheses in musculoskeletal tumour surgery of the lower limb

Purpose

The incidence of recurrent infections in patients following one or two stage revision for infected megaprostheses after resection of bone tumours was investigated. The difference between retaining at least one well fixed stem and a complete removal of the megaprosthesis during a two stage revision was also analysed.

Methods

627 patients who experienced a replacement of a musculoskeletal tumour by megaprostheses were recorded. An infection occurred in 83 of 621 patients available for follow-up. 61 patients underwent one stage revision, and 16 patients two stage revision for the first revision surgery. In the entire study period, two stage revision was performed 32 times (first, second, and third revision).

Results

The cumulative incidence analysis showed a reinfection probability after one stage revision of 18% at one year, 30% at two years, 39% at five years, 46% at ten years, and 56% at 15 years. After two stage revision, a reinfection probability of 28% at two years, and 48% at five years was calculated. Cumulative incidence curves did not differ significantly (Gray’s test; p = 0.51) between one and two stage revision (with and without complete removal of the stems). In two stage revision (n = 32), a statistically significant difference in infection rates between patients treated with complete removal of the megaprosthesis (n = 18) including anchorage stems and patients with at least one retained stem (n = 14) was shown (Fisher’s exact test, p = 0.029).

Conclusion

Two stage revisions with complete removal of the megaprosthesis showed the best results among limb salvage procedures for the treatment of infected megaprosthesis.

[Not Available]

Zusammenfassung. Mit stetig steigender Häufigkeit endoprothetischer Eingriffe nimmt auch die Bedeutung der damit vergesellschafteten Revisionschirurgie zu. Die Gelenksprothesen-Infektion ist hierbei eine der schwerwiegendsten Komplikationen, die zur Erlangung eines bestmöglichen Behandlungsergebnisses eine differenzierte Diagnose- und Therapiestrategie erfordert. Anamnese, klinische Untersuchung, Laborkontrollen, Radiologie (konventionelle und spezialisierte), Gelenkspunktion sowie Mikrobiologie und Histologie liefern entscheidende Hinweise zur Diagnosestellung als unabdingbare Voraussetzung zur Erstellung und Einleitung des entsprechenden Therapiekonzeptes. Insbesondere die Abgrenzung zwischen aseptischen und septischen Prothesenlockerungen ist schwierig und erfordert ein differenziertes und interdisziplinäres Vorgehen. Die kurative Behandlungsstrategie ist abhängig von: Dauer der Symptome, Latenz seit Primärimplantation, Keimspektrum, Antibiogramm und Weichteilverhältnissen und umfasst prothesenerhaltende Strategien bei nicht gelockerter Prothese, reizlosen Weichteilen und Abwesenheit von Problemkeimen, bis hin zum kompletten ein- oder zweizeitigen Prothesenwechsel bei einer chronischen Infektion. In diesem Beitrag werden die aktuellen Management-Konzepte der Gelenksprothesen-Infektionen diskutiert.

[Periprosthetic infections of the hip joint : Clinical approach]

BACKGROUND

Increasing rates of periprosthetic joint infections (PJI) will present orthopedic surgeons and the health care system with challenges in the next few years. New concepts in diagnostic and surgical pathways allow specialized centers to offer differentiated therapy of PJI.

AIM

This article presents an overview of recent treatment concepts for PJI of the hip emphasizing diagnosis and the clinical approach.

METHOD

A selective literature search was performed focusing on evidence-based concepts including diagnostics, surgical treatment, and biofilm active antibiotics.

RESULTS

PJI of the hip are classified as mature biofilm or immature biofilm infections. The most important step in the diagnostic procedure is to identify the pathogen and its antimicrobial susceptibility. Preoperative joint aspiration and leukocyte count, differentiation, and microbiological culture should be standard. Arthroscopic biopsy may be necessary to identify the pathogen. Depending on the biofilm maturity and the antimicrobial susceptibility, implant retention or two-stage revisions should be performed. Combination of surgical therapy and biofilm-active antibiotics are of utmost importance for successful treatment.

DISCUSSION

PJI represents a significant challenge for the orthopedic surgeon. Evidence-based and standardized clinical pathways are necessary for accurate and rapid diagnosis as well as patient-specific treatment concepts.

Iodine-Supported Hip Implants: Short Term Clinical Results

We developed a new povidone iodine coating technology for titanium hip implants and performed a clinical trial to assess its usefulness in suppressing postoperative infection. Results indicate that iodine-supported titanium has favorable antibacterial activity, biocompatibility, and no cytotoxicity. Thirty joints in 28 patients were treated using iodine-supported implants. Fourteen joints were revision total hip arthroplasty (THA) after periprosthetic infection, 13 were primary THA for immunosuppressive conditions or pyogenic arthritis, and 3 were conversions from hemiarthroplasty to THA for immunosuppressive conditions. Two examinations were conducted sequentially until final follow-up: white blood cell (WBC) and C-reactive protein (CRP) were measured pre- and postoperatively and thyroid hormone levels in the blood were examined. The mean follow-up period was 33 months (14-78). There were no signs of infection in any patient at the last follow-up. WBC and CRP levels returned to normal within several weeks. No abnormalities of thyroid gland function were detected. Loosening of the implants did not occur in any patient. Excellent bone ingrowth and ongrowth were found around prostheses. No cytotoxicity or adverse effects were detected. These results suggest that iodine-supported THA implants can be highly effective in preventing and treating postoperative infections.

Introducing a semi-coated model to investigate antibacterial effects of biocompatible polymers on titanium surfaces

Peri-implant infections from bacterial biofilms on artificial surfaces are a common threat to all medical implants. They are a handicap for the patient and can lead to implant failure or even life-threatening complications. New implant surfaces have to be developed to reduce biofilm formation and to improve the long-term prognosis of medical implants. The aim of this study was (1) to develop a new method to test the antibacterial efficacy of implant surfaces by direct surface contact and (2) to elucidate whether an innovative antimicrobial copolymer coating of 4-vinyl-N-hexylpyridinium bromide and dimethyl(2-methacryloyloxyethyl) phosphonate (VP:DMMEP 30:70) on titanium is able to reduce the attachment of bacteria prevalent in peri-implant infections. With a new in vitro model with semi-coated titanium discs, we were able to show a dramatic reduction in the adhesion of various pathogenic bacteria (Streptococcus sanguinis, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis), completely independently of effects caused by soluble materials. In contrast, soft tissue cells (human gingival or dermis fibroblasts) were less affected by the same coating, despite a moderate reduction in initial adhesion of gingival fibroblasts. These data confirm the hypothesis that VP:DMMEP 30:70 is a promising antibacterial copolymer that may be of use in several clinical applications.

Synovial C-reactive protein as a marker for chronic periprosthetic infection in total hip arthroplasty

The aim of this study was to assess the role of synovial C-reactive protein (CRP) in the diagnosis of chronic periprosthetic hip infection. We prospectively collected synovial fluid from 89 patients undergoing revision hip arthroplasty and measured synovial CRP, serum CRP, erythrocyte sedimentation rate (ESR), synovial white blood cell (WBC) count and synovial percentages of polymorphonuclear neutrophils (PMN). Patients were classified as septic or aseptic by means of clinical, microbiological, serum and synovial fluid findings. The high viscosity of the synovial fluid precluded the analyses in nine patients permitting the results in 80 patients to be studied. There was a significant difference in synovial CRP levels between the septic (n = 21) and the aseptic (n = 59) cohort. According to the receiver operating characteristic curve, a synovial CRP threshold of 2.5 mg/l had a sensitivity of 95.5% and specificity of 93.3%. The area under the curve was 0.96. Compared with serum CRP and ESR, synovial CRP showed a high diagnostic value. According to these preliminary results, synovial CRP may be a useful parameter in diagnosing chronic periprosthetic hip infection.

Cite this article: Bone Joint J 2015; 97-B:173–6.

Biocompatibility of silver nanoparticles and silver ions in primary human mesenchymal stem cells and osteoblasts

The prevention of implant-related infections is an important issue in medical research. The aim is to exploit the strong antimicrobial effect of silver nanoparticles (AgNP) to develop new antibacterial coatings for implants. However, there is still a serious lack of information on the influence of AgNP on bone metabolism. In the present study we have evaluated the influence of AgNP on cell stress, viability, proliferation and differentiation of primary human mesenchymal stem cells (MSC) and osteoblasts (OB). Finally, cellular uptake of the AgNP was examined. After 21 days impairment of cell viability of MSC and OB occurred at a concentration of 10 μg/g of AgNP. Cytotoxicity and inhibition of proliferation was highly time and dose dependent. No influence on cell differentiation, but an increase in cell stress, was observed. Uptake of AgNP into MSC and OB could be confirmed. In summary, these results demonstrate AgNP-mediated cytotoxicity at higher concentrations. Therefore, a therapeutical window for the application of AgNP in medical products might exist. However, the antibacterial benefits and potential health risks of AgNP need to be weighed in further studies.

A model of implant-associated infection in the tibial metaphysis of rats

OBJECTIVE

Implant-associated infections remain serious complications in orthopaedic and trauma surgery. A main scientific focus has thus been drawn to the development of anti-infective implant coatings. Animal models of implant-associated infections are considered helpful in the in vivo testing of new anti-infective implant coatings. The aim of the present study was to evaluate a novel animal model for generation of implant-associated infections in the tibial metaphysis of rats.

MATERIALS AND METHODS

A custom-made conical implant made of Ti6Al4V was inserted bilaterally at the medial proximal tibia of 26 female Sprague-Dawley rats. Staphylococcus aureus in amounts spanning four orders of magnitude and each suspended in 15  μ l phosphate buffered saline (PBS) was inoculated into the inner cavity of the implant after the implantation into the defined position. Controls were treated accordingly with PBS alone. Animals were then followed for six weeks until sacrifice. Implant-associated infection was evaluated by microbiological investigation using swabs and determination of viable bacteria in the bone around the implant and the biofilm on the implants after sonification.

RESULTS

Irrespective of the initial inoculum, all animals in the various groups harbored viable bacteria in the intraoperative swabs as well as the sonication fluid of the implant and the bone samples. No correlation could be established between initially inoculated CFU and population sizes on implant surfaces at sacrifice. However, a significantly higher viable count was observed from peri-implant bone samples for animals inoculated with 10(6) CFU. Macroscopic signs of animal infection (pus and abscess formation) were only observed for implants inoculated with at least 10(5) CFU S. aureus.

DISCUSSION/CONCLUSION

The results demonstrate the feasibility of this novel animal model to induce an implant-associated infection in the metaphysis of rats, even with comparatively low bacterial inocula. The specific design of the implant allows an application of bacteria in reproducible numbers at well-defined contact sites to the animal bone.

Increased accumulation of magnetic nanoparticles by magnetizable implant materials for the treatment of implant-associated complications

Background

In orthopaedic surgery, accumulation of agents such as anti-infectives in the bone as target tissue is difficult. The use of magnetic nanoparticles (MNPs) as carriers principally enables their accumulation via an externally applied magnetic field. Magnetizable implants are principally able to increase the strength of an externally applied magnetic field to reach also deep-seated parts in the body. Therefore, the integration of bone-addressed therapeutics in MNPs and their accumulation at a magnetic orthopaedic implant could improve the treatment of implant related infections. In this study a martensitic steel platelet as implant placeholder was used to examine its accumulation and retention capacity of MNPs in an in vitro experimental set up considering different experimental frame conditions as magnet quantity and distance to each other, implant thickness and flow velocity.

Results

The magnetic field strength increased to approximately 112% when a martensitic stainless steel platelet was located between the magnet poles. Therewith a significantly higher amount of magnetic nanoparticles could be accumulated in the area of the platelet compared to the sole magnetic field. During flushing of the tube system mimicking the in vivo blood flow, the magnetized platelet was able to retain a higher amount of MNPs without an external magnetic field compared to the set up with no mounted platelet during flushing of the system. Generally, a higher flow velocity led to lower amounts of accumulated MNPs. A higher quantity of magnets and a lower distance between magnets led to a higher magnetic field strength. Albeit not significantly the magnetic field strength tended to increase with thicker platelets.

Conclusion

A martensitic steel platelet significantly improved the attachment of magnetic nanoparticles in an in vitro flow system and therewith indicates the potential of magnetic implant materials in orthopaedic surgery. The use of a remanent magnetic implant material could improve the efficiency of capturing MNPs especially when the external magnetic field is turned off thus facilitating and prolonging the effect. In this way higher drug levels in the target area might be attained resulting in lower inconveniences for the patient.