Prosthetic joint infection

Plasma Cell Infiltration on Histopathological Samples of Chronic Bone and Joint Infections due to Cutibacterium acnes: A series of 21 Cases

Introduction: Histopathological definition of bone and joint infection (BJI) is based on Mirra's criterion (≥ 5 polymorphonuclears (PMNs) per field in 5 high power fields (HPFs)). However, this definition does not seem appropriate for chronic BJIs caused by slow-growing germs such as Cutibacterium acnes (C. acnes). The aim of this study was to confirm that Mirra's criterion is not adequate for diagnosis of BJIs due to C. acnes. The second objective was to determine if plasma cell infiltration could be useful for the diagnosis of chronic BJIs due to C. acnes. Methods: We retrospectively selected 25 consecutive patients from 2009 to 2013 with chronic BJIs due to C. acnes. Histological analysis was performed on the 21 cases with at least two C. acnes positive cultures. In addition of Mirra's criterion, the number of plasma cells (≥5 plasma cells/5 HPFs, defined as "CRIOAc Lyon's criterion") was implemented in the histopathological analysis. Patients were defined as infected, if at least one of the two criteria were present. Results: According to Mirra's and CRIOAc Lyon's criteria, positive histopathology was observed in 12 (57.1%) and 15 (71.4%) cases respectively. Considering the 9 cases with negative Mirra's criterion, high plasma cell infiltration (≥5 plasma cells per field/5 HPFs) was observed in 5 cases (55.6%), and low plasma cells infiltration (2-5 plasma cells per field/5 HPFs) was observed in 4 other cases (44.4%). Conclusions: Adding CRIOAc Lyon's criterion to Mirra's criterion might restore some histopathological diagnosis of chronic BJIs due to C. acnes when a chronic BJI is clinically suspected.

Impact of Cytokines and Phosphoproteins in Response to Chronic Joint Infection

The early cellular response to infection has been investigated extensively, generating valuable information regarding the mediators of acute infection response. Various cytokines have been highlighted for their critical roles, and the actions of these cytokines are related to intracellular phosphorylation changes to promote infection resolution. However, the development of chronic infections has not been thoroughly investigated. While it is known that wound healing processes are disrupted, the interactions of cytokines and phosphoproteins that contribute to this dysregulation are not well understood. To investigate these relationships, this study used a network centrality approach to assess the impact of individual cytokines and phosphoproteins during chronic inflammation and infection. Tissues were taken from patients undergoing total knee arthroplasty (TKA) and total knee revision (TKR) procedures across two tissue depths to understand which proteins are contributing most to the dysregulation observed at the joint. Notably, p-c-Jun, p-CREB, p-BAD, IL-10, IL-12p70, IL-13, and IFN-γ contributed highly to the network of proteins involved in aseptic inflammation caused by implants. Similarly, p-PTEN, IL-4, IL-10, IL-13, IFN-γ, and TNF-α appear to be central to signaling disruptions observed in septic joints. Ultimately, the network centrality approach provided insight into the altered tissue responses observed in chronic inflammation and infection.

A Biodegradable Antifungal-Loaded Sol-Gel Coating for the Prevention and Local Treatment of Yeast Prosthetic-Joint Infections

Fungal prosthetic-joint infections are rare but devastating complications following arthroplasty. These infections are highly recurrent and expose the patient to the development of candidemia, which has high mortality rates. Patients with this condition are often immunocompromised and present several comorbidities, and thus pose a challenge for diagnosis and treatment. The most frequently isolated organisms in these infections are Candida albicans and Candida parapsilosis, pathogens that initiate the infection by developing a biofilm on the implant surface. In this study, a novel hybrid organo-inorganic sol-gel coating was developed from a mixture of organopolysiloxanes and organophosphite, to which different concentrations of fluconazole or anidulafungin were added. Then, the capacity of these coatings to prevent biofilm formation and treat mature biofilms produced by reference and clinical strains of C. albicans and C. Parapsilosis was evaluated. Anidulafungin-loaded sol-gel coatings were more effective in preventing C. albicans biofilm formation, while fluconazole-loaded sol-gel prevented C. parapsilosis biofilm formation more effectively. Treatment with unloaded sol-gel was sufficient to reduce C. albicans biofilms, and the sol-gels loaded with fluconazole or anidulafungin slightly enhanced this effect. In contrast, unloaded coatings stimulated C. parapsilosis biofilm formation, and loading with fluconazole reduced these biofilms by up to 99%. In conclusion, these coatings represent a novel therapeutic approach with potential clinical use to prevent and treat fungal prosthetic-joint infections.

A Case of Actinomyces Prosthetic Hip Infection

Actinomyces is a species of gram-positive anaerobic commensal organisms found in the human oropharynx, gastrointestinal, and genitourinary tracts, which most often are implicated in cervicofacial infections. Rarely do these organisms cause joint infections. We present the case of a 68-year-old man with a prosthetic hip infection due to Actinomyces species. He underwent surgical incision and drainage with replacement of the prosthetic joint. Cultures grew Actinomyces species, and he was treated with a four-week course of ampicillin-sulbactam followed by eight weeks of amoxicillin-clavulanate. This organism is an uncommon pathogen, and few cases of prosthetic joint infection due to Actinomyces have previously been reported.

Validity of the KLIC and CRIME80 scores in predicting failure in late acute infection treated by debridement and implant retention

It is very important to treat prosthetic infections correctly in order to ensure a higher success rate. Debridement with implant retention (DAIR) is widely used in acute and late infections, however patients who fail after this surgery are known to have a higher risk of failure in subsequent surgeries. Therefore, it is important to find a scale that enables us to predict the risk of DAIR failure. Hence the KLIC and CRIME80 scores for acute and late acute infections, respectively. This study analysed the validity of both scores in acute late periprosthetic knee infections. We observed that the KLIC score has no predictive value for this type of infection, but the CRIME80 score does.

Reactive Arthritis Provoked by Campylobacter jejuni Enterocolitis Mimicking Prosthetic Joint Infection: A Case Report

CASE

A 59-year-old man with previously well-functioning partial knee replacement was admitted with a warm, swollen, and painful knee. The clinical presentation was consistent with prosthetic joint infection (PJI), but the synovial fluid analysis was negative for microbial growth. Further discussion revealed earlier Campylobacter jejuni enterocolitis that subsequently provoked reactive arthritis (ReA) mimicking PJI. The patient was treated with oral naproxen and intra-articular injection of triamcinolone and recovered completely without antibiotics or surgery. After 29 months, the knee is functioning normally.

CONCLUSION

ReA is rare but should be included in the differential diagnosis of PJI.

New developments and future challenges in prevention, diagnosis, and treatment of prosthetic joint infection

Prosthetic joint infection (PJI) is a devastating complication that results in substantial costs to society and patient morbidity. Advancements in our knowledge of this condition have focused on prevention, diagnosis, and treatment, in order to reduce rates of PJI and improve patient outcomes. Preventive measures such as optimization of patient comorbidities, and perioperative antibiotic usage are intensive areas of current clinical research to reduce the rate of PJI. Improved diagnostic tests such as synovial fluid (SF) α-defensin enzyme-linked immunosorbent assay, and nucleic acid-based tests for serum, SF, and tissue cultures, have improved diagnostic accuracy and organism identification. Increasing the diversity of available antibiotic therapy, immunotherapy, and alternative implant coatings remain promising treatments to improve infection eradication in the setting of PJI.

Clinical magnetic resonance imaging of arthroplasty at 1.5 T

Magnetic resonance imaging (MRI) has historically been avoided for the routine clinical evaluation of metal implants at many clinical centers due to the presence of artifact that creates in-plane and through-plane distortions and signal intensity voids in generated images. However, when the image acquisition parameters are appropriately modified and advanced multi-spectral pulse sequences are used, high-quality diagnostic images can be generated and may be used for diagnosing patients with suspected periprosthetic pathology. MRI provides superior soft-tissue contrast and excellent sensitivity for mobile water and is, therefore, a valuable tool in the evaluation of these patients, given the increasing prevalence of arthroplasty within the general population. Knowledge of expected normal postoperative appearance in patients with total hip arthroplasty, total knee arthroplasty, and total shoulder arthroplasty facilitates the detection of abnormal findings in this population, as does familiarity with common pathologic conditions encountered in the periprosthetic region. This review article will provide background information regarding the presence of image artifacts, methods to reduce the artifacts, and application of MRI at 1.5 T for evaluating common complications in subjects with total knee arthroplasty, total hip arthroplasty, and total shoulder arthroplasty.

Comparison of infection in cemented, cementless and hybrid primary total knee arthroplasty: a network meta-analysis and systematic review of randomized clinical trials

BACKGROUND

Prosthetic joint infection (PJI) is a serious complication of joint replacement surgeries. Surgeons often take extra measures to reduce the risk of PJI. Whilst many studies have compared between cemented, cementless and hybrid fixation (femoral cementless, tibial cemented), most focus on survivorship, clinical and function outcome scores as primary endpoints. This meta-analysis aims to study the association between fixation methods and risk of PJI in primary total knee arthroplasty (TKA).

METHODS

A systematic review and network meta-analysis of randomized controlled trials (RCT) were performed according to Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. Data from studies assessing prevalence of PJI in each fixation type were extracted and analysed.

RESULTS

Twelve RCT comprising a total of 1573 knees were included. Six RCT compared between cemented (n = 486 knees) and cementless (n = 440 knees) fixation, while six RCT compared between hybrid (n = 324 knees) and cementless (n = 323 knees) fixation. Network meta-analysis did not reveal any fixation type that significantly increased the infection rate in TKA. Rate of all infection was lowest in cemented TKA as compared to cementless (odds ratio (OR) 0.90, 95% confidence interval (CI) 0.35-2.28) and hybrid (OR 0.63, 95%CI 0.13-2.99) TKA. Rate of PJI requiring revision surgery was lowest in cementless TKA as compared to cemented (OR 0.89, 95%CI 0.30-2.41) and hybrid (OR 0.57, 95%CI 0.09-2.71) TKA. Rate of PJI not requiring revision surgery was lowest in cemented TKA as compared to hybrid (OR 0.56, 95%CI 0.06-6.10) and cementless (OR 0.55, 95% 0.14-5.63).

CONCLUSION

Unlike total hip arthroplasties, fixation method is not a predisposing risk factor for infections in TKA. However, this meta-analysis may not have sufficient statistical power to show a significant difference between fixation types. It is recommended that prophylactic precautions against other known risk factors for infection should still be clinically practiced.

LEVEL OF EVIDENCE

Level I, meta-analysis of randomized controlled trials.

Antibiotic containing bone cement in prevention of hip and knee prosthetic joint infections: A systematic review and meta-analysis

BACKGROUND

Prosthetic joint infection (PJI) is the most serious total joint arthroplasty (TJA) complication despite several aseptic and antiseptic preventive measures. There is no clear evidence or even consensus, whether antibiotic-loaded bone cement (ALBC) should be used, in addition to systemic short-term routine antibiotic prophylaxis, to reduce the risk of PJI in primary TJA. We aimed to analyze the efficacy of ALBC for prevention of PJI in patients undergoing primary TJA.

METHODS

We searched systematically for randomized controlled trials (RCTs) in PubMed, Scopus, Embase, Web of Science and Cochrane library. Two reviewers independently screened potentially eligible studies according to predefined selection criteria and assessed the risk of bias using a modified version of the Cochrane risk of bias tool. PJI was prespecified as the primary outcome of interest. The meta-analyses were based on risk ratios using random-effects model per default. For the purpose of sensitivity, the corresponding fixed effects model odds ratios were calculated with the use of the Peto method as well. To evaluate a potential difference in effect sizes using different types (subgroups) of antibiotics used in bone cement, and at different follow-up periods, we performed stratified meta-analyses.

RESULTS

Thirty-seven studies were eligible for the systematic review and qualitative synthesis, and 9 trials (6507 total joint arthroplasties) were included in this meta-analysis. Overall ALBC significantly reduced the risk of PJI following primary TJAs (RRs, 0.36; 95% CIs, 0.16 to 0.80; P = 0.01) with a moderate degree of inconsistency (I2 = 47%). Based on stratified meta-analyses the use of gentamicin appeared to have a better effect (P = 0.0005) in the total hip arthroplasty. Pooled data of different antibiotics used in knee arthroplasties showed a significant association of cefuroxime (RRs, 0.08; 95% CIs, 0.01 to 0.63; P = 0.02). Further, ALBCs significantly reduced the PJI at one and two years of follow-up (P = 0.03 and P = 0.005 respectively).

CONCLUSIONS

The evidence suggests that ALBCs are effective in reducing the PJI following primary TJA; i.e. between 20 and 84% reduced risk. However, the clear limitations of the available trial evidence highlight the need for joint-specific confirmatory trials, that will need to be designed as cluster-randomized trials of clinics in countries with well-functioning arthroplasty registries.The translational potential of this article: This meta-analysis highlights the prophylactic potential of ALBCs in lowering the risk of infection following primary hip or knee arthroplasties but emphasizes the need for more recent confirmatory trials.

How to manage treatment failure in prosthetic joint infection

BACKGROUND

Management for prosthetic joint infections remains a challenging area for both infectious diseases and orthopaedic surgery, particularly in the setting of treatment failure. This is compounded by a lack of level 1 evidence to guide approaches. The optimal management of prosthetic joint infections requires a multi-disciplinary approach combined with shared decision making with the patient.

AIMS

This article describes the approach to prosthetic joint infections in the setting of treatment failure.

SOURCES

Narrative review based on literature review from PubMed. There was no time limit on the studies included. In addition, the reference list for included studies were reviewed for literature saturation with manual searching of clinical guidelines. Management approaches described incorporate evidence- and eminence-based recommendations from expert guidelines and clinical studies, where applicable.

CONTENT

The surgical and antimicrobial approaches for prosthetic joint infections are described for first-line treatment of prosthetic joint infections and approaches in the event of treatment failure. Management approaches are based on an understanding of the role the biofilm plays in the pathogenesis of prosthetic joint infections. The management of these infections aims to fulfil two key goals: to eradicate the biofilm-associated microorganisms and, to maintain a functional joint and quality of life. In treatment failure, these goals are not always feasible, and the role of the multi-disciplinary team and shared-decision making are prominent.

IMPLICATIONS

Prosthetic joint surgery is a high-volume surgery, and the demand for this surgery is continually increasing. With this, the number of infections requiring expert care will also increase. Eminence-based management approaches have been established to guide treatment failure until knowledge gaps in optimal management are addressed by well-designed, clinical trials.

The Epidemiology and Outcomes of Septic Arthritis in the Maltese Islands: A Hospital-Based Retrospective Cohort Study

Objective/Aim:

Septic arthritis is an uncommon but important disease with significant morbidity and mortality, especially if inadequately managed. The aim of this epidemiological study was to identify the characteristics and outcomes of patients treated for septic arthritis at Mater Dei Hospital, Malta, over a 10-year period.

Methods:

This was a retrospective observational study. Patients diagnosed with septic arthritis between 2008 and 2018 were recruited. Cases were identified by reviewing all inhospital episodes of patients diagnosed with septic arthritis according to Newman criteria.

Results:

There were 124 cases of native joint septic arthritis and 138 of prosthetic joint infection. Cases were present amongst all age groups, with the highest incidence amongst those aged 61–70 years for both native and prosthetic infections. Fever was present in around 40% of cases. Raised white cell count was prevalent in 66.9% of native joint infections and 52.9% of prosthetic joints. Elevated C-reactive protein was overwhelmingly seen in most cases, present in 93.5% (median=159.5 mg/L; IQR=85.8–291) of native joints and 92.0% of prosthetic joint infections (median=68.7 mg/L; IQR=20.5–186). Over 55% of patients had one or more risk factors for joint sepsis, diabetes mellitus being the most prevalent clinical comorbidity (22.6% and 24.6% for native and prosthetic joint infections respectively). Synovial cultures were positive in 66% and 82% of native and prosthetic joint aspirates respectively. Staphylococcus aureus was the most commonly isolated organism from both native and prosthetic joint infection, followed by streptococcal infections in native joints and coagulase negative staphylococci and gram-negative infections in prosthetic joints. Fifteen deaths were directly attributed to joint sepsis.

Conclusion:

Absence of fever and elevated white cell count does not exclude the diagnosis. The mortality rate due to septic arthritis in this cohort of patients was found to be 5.7%. All deaths occurred in elderly patients with clinical comorbidities suggesting that this group is at highest risk.

Anti-rheumatic treatment and prosthetic joint infection: an observational study in 494 elective hip and knee arthroplasties

Background

Surgical site infections are more frequent among patients with rheumatic disease. To what extent this is related to immunosuppressive antirheumatic drugs is unclear, as is the value of discontinuing medication perioperatively. The aim of study was to assess the rate of surgical site infections after knee and hip replacement in patients with inflammatory joint disease, with an emphasis on periprosthetic joint infection, and to investigate the influence of treatment with disease-modifying antirheumatic drugs (DMARDs) in this regard.

Methods

Data were collected from 494 primary elective hip (51.4%) and knee arthroplasties, along with demographic and medication data. The primary outcome was surgical site infection during the first year after surgery.

Results

In 78% (n = 385) of the cases the patient used 1 to 3 disease-modifying antirheumatic drugs perioperatively. Thirty-two percent (n = 157) of patients used a TNF-alpha inhibitor. The rate of surgical site infection was 3.8% (n = 19). The rate of periprosthetic joint infection was 1.4% (n = 7), all of which occurred after knee arthroplasty. Periprosthetic joint infection occurred in only 1 patient medicating perioperatively with a TNF-alpha inhibitor.

Conclusion

Surgical site infections were not associated with ongoing medication with disease-modifying antirheumatic drugs. Due to the low event rate this should be interpreted with caution, but our center will maintain its routine of continuing treatment with TNF-alpha inhibitors perioperatively.

Two-Stage Primary Arthroplasty of Native Hips and Knees That Had Previously Failed Treatment for Septic Arthritis: A Single-Center Experience

Background

Patients with a history of degenerative joint disease secondary to an acute or remote episode of septic arthritis of the native knee or hip present a unique challenge for the orthopaedic surgeon. This study describes our experience with two-stage primary arthroplasty for such patients.

Methods

We reviewed 42 patients with a history of septic arthritis treated with two-stage primary arthroplasty between 2008 and 2018. Patients were evaluated using modified Harris Hip Score, Knee Society Score (KSS), and KSS functional component (KSSF). Paired t-tests were used to compare changes for continuous variables within cohorts. Multivariate linear and logistic regression models were constructed to determine predictors of outcomes and complications.

Results

At a mean of 3.3-year follow-up, there were 14 (33.3%) complications and the infection cure rate was 95.2%. On average, patients improved in the modified Harris Hip Score (42.9 ± 11.8 vs 83.3 ± 11.1, P < .001), KSS (35.9 ± 16.9 vs 80.1 ± 16.6, P < .001), KSSF (38.0 ± 15.1 vs 71.5 ± 24.0, P < .001), knee flexion (90.9 ± 14.9 vs 100.5 ± 17.1), and hip flexion (73.8 ± 21.2 vs 102.1 ± 11.8, P < .001). Age (β: -0.78, P = .004) was independently associated with lower Harris Hip Score in the hip cohort. There were no independent predictors of the KSS or KSSF. The erythrocyte sedimentation rate (odds ratio: 1.07, P = .043) and C-reactive protein (odds ratio: 1.43, P = .018) at stage 2 were independently associated with a higher likelihood of complications at the final follow-up.

Conclusion

Patients with a history of native septic arthritis of the hip and knee, and secondary end-stage degenerative joint disease, showed significant postoperative improvements and a high rate of complications after two-stage primary total joint arthroplasty. Despite improvements, some patients may necessitate a third operation because of the incidence of reinfection and spacer exchange. This information should be used to counsel patients who present with this challenging clinical scenario.

Time-Transient Effects of Silver and Copper in the Porous Titanium Dioxide Layer on Antibacterial Properties

Recently, silver (Ag) and copper (Cu) have been incorporated into a titanium (Ti) surface to realize their antibacterial property. This study investigated both the durability of the antibacterial effect and the surface change of the Ag- and Cu-incorporated porous titanium dioxide (TiO2) layer. Ag- and Cu-incorporated TiO2 layers were formed by micro-arc oxidation (MAO) treatment using the electrolyte with Ag and Cu ions. Ag- and Cu-incorporated specimens were incubated in saline during a period of 0-28 days. The changes in both the concentrations and chemical states of the Ag and Cu were characterized using X-ray photoelectron spectroscopy (XPS). The durability of the antibacterial effects against Escherichia coli (E. coli) were evaluated by the international organization for standardization (ISO) method. As a result, the Ag- and Cu-incorporated porous TiO2 layers were formed on a Ti surface by MAO. The chemical state of Ag changed from Ag2O to metallic Ag, whilst that of Cu did not change by incubation in saline for up to 28 days. Cu existed as a stable Cu2O compound in the TiO2 layer during the 28 days of incubation in saline. The concentrations of Ag and Cu were dramatically decreased by incubation for up to 7 days, and remained a slight amount until 28 days. The antibacterial effect of Ag-incorporated specimens diminished, and that of Cu was maintained even after incubation in saline. Our study suggests the importance of the time-transient effects of Ag and Cu on develop their antibacterial effects.

A Bioinformatic Approach to Utilize a Patient's Antibody-Secreting Cells against Staphylococcus aureus to Detect Challenging Musculoskeletal Infections

Noninvasive diagnostics for Staphylococcus aureus musculoskeletal infections (MSKI) remain challenging. Abs from newly activated, pathogen-specific plasmablasts in human blood, which emerge during an ongoing infection, can be used for diagnosing and tracking treatment response in diabetic foot infections. Using multianalyte immunoassays on medium enriched for newly synthesized Abs (MENSA) from Ab-secreting cells, we assessed anti-S. aureus IgG responses in 101 MSKI patients (63 culture-confirmed S. aureus, 38 S. aureus-negative) and 52 healthy controls. MENSA IgG levels were assessed for their ability to identify the presence and type of S. aureus MSKI using machine learning and multivariate receiver operating characteristic curves. Eleven S. aureus-infected patients were presented with prosthetic joint infections, 15 with fracture-related infections, 5 with native joint septic arthritis, 15 with diabetic foot infections, and 17 with suspected orthopedic infections in the soft tissue. Anti-S. aureus MENSA IgG levels in patients with non-S. aureus infections and healthy controls were 4-fold (***p = 0.0002) and 8-fold (****p < 0.0001) lower, respectively, compared with those with culture-confirmed S. aureus infections. Comparison of MENSA IgG responses among S. aureus culture-positive patients revealed Ags predictive of active MSKI (IsdB, SCIN, Gmd) and Ags predictive of MSKI type (IsdB, IsdH, Amd, Hla). When combined, IsdB, IsdH, Gmd, Amd, SCIN, and Hla were highly discriminatory of S. aureus MSKI (area under the ROC curve = 0.89 [95% confidence interval 0.82-0.93, p < 0.01]). Collectively, these results demonstrate the feasibility of a bioinformatic approach to use a patient's active immune proteome against S. aureus to diagnose challenging MSKI.

Long acting anti-infection constructs on titanium

Peri-prosthetic joint infections (PJI) are a serious adverse event following joint replacement surgeries; antibiotics are usually added to bone cement to prevent infection offset. For uncemented prosthesis, alternative antimicrobial approaches are necessary in order to prevent PJI; however, despite elution of drug from the surface of the device being shown one of the most promising approach, no effective antimicrobial eluting uncemented device is currently available on the market. Consequently, there is a clinical need for non-antibiotic antimicrobial uncemented prosthesis as these devices present numerous benefits, particularly for young patients, over cemented artificial joints. Moreover, non-antibiotic approaches are driven by the need to address the growing threat posed by antibiotic resistance. We developed a multilayers functional coating on titanium surfaces releasing chlorhexidine, a well-known antimicrobial agent used in mouthwash products and antiseptic creams, embedding the drug between alginate and poly-beta-amino-esters. Chlorhexidine release was sustained for almost 2 months and the material efficacy and safety was proven both in vitro and in vivo. The coatings did not negatively impact osteoblast and fibroblast cells growth and were capable of reducing bacterial load and accelerating wound healing in an excisional wound model. As PJI can develop weeks and months after the initial surgery, these materials could provide a viable solution to prevent infections after arthroplasty in uncemented prosthetic devices and, simultaneously, help the fight against antibiotic resistance.

Rifabutin Use in Staphylococcus Biofilm Infections: A Case Series

This is a case series of 10 patients who had staphylococcal biofilm infections that were treated with adjuvant rifabutin therapy instead of rifampin therapy. In these cases, rifampin was contraindicated secondary to drug–drug interactions with the patients’ chronic medications. Rifabutin therapy was well tolerated with no side effects. As well, no patients had recurrence of their staphylococcal infections. This case series shows that rifabutin can be a beneficial adjuvant therapy in Staphylococcus biofilm infections when drug–drug interactions limit the use of rifampin.

Titanium particles induce apoptosis by promoting autophagy in macrophages via the PI3K/Akt signaling pathway

Chronic inflammation and infection in the tissue surrounding implants after total joint replacement is closely associated with the innate immune response to surgical implants. Wear particles are known to increase apoptosis and impair the innate immunity in macrophages, which can cause immunosuppression around the implants. Excessive autophagy can induce apoptosis. However, the link between autophagy and apoptosis in macrophages during chronic inflammation and infection remains unknown. In this study, we investigated the autophagy and apoptosis induced by titanium particles in RAW264.7 macrophages, and in the interface membrane of patients with late-onset periprosthetic joint infection (PJI). We found that titanium particles stimulated autophagy and apoptosis in macrophages. Inhibition of autophagy significantly reduced titanium particle-induced apoptosis in macrophages, which may be related to the PI3K/Akt signaling pathway. The secretion of inflammatory factors, such as IL-1β, IL-6, and TNF-α, decreased after inhibition of autophagy in titanium particle-stimulated macrophages, which may be caused by immune dysfunction due to titanium particle-induced autophagy and apoptosis in macrophages. Furthermore, our in vivo mouse calvarial model also showed that autophagy inhibitors lowered the rate of cell apoptosis. Our findings indicate that wear particle-induced apoptosis may be caused by enhanced autophagy in macrophages, which could potentially impair the local innate immunity in periprosthetic tissues and could be a risk factor for PJI. Based on these results, autophagy modulators may act as a new therapeutic option for PJI.

Periprosthetic knee infection reconstruction with a hinged prosthesis: Implant survival and risk factors for treatment failure

BACKGROUND

Severe bone and soft tissue defects are common after failed two-stage exchange arthroplasty for periprosthetic joint infection (PJI). There is a paucity of evidence on the outcomes of using a hinged prosthesis for knee PJI reconstruction during second-stage re-implantation, especially regarding implant survivorship, reinfection risk factors, and functionality after successful reconstruction.

METHODS

A total of 58 knee PJI patients with Anderson Orthopaedic Research Institute (AORI) type II/III defect and soft tissue insufficiency underwent reconstruction with hinged prosthesis. Enrolled patients adhered to a two-stage exchange arthroplasty protocol and were evaluated for a mean follow up of 65.1 months. Kaplan-Meier analysis was conducted for implant survivorship and infection-free survival. Multivariate analysis was used to determine independent risk factors for recurrent infections. Knee Society Score (KSS) was used to evaluate functional outcomes.

RESULTS

The survivorship of hinged prosthesis was 86.2% at 2 years and 70.2% at 5 years. Infection-free analysis revealed an estimation of 68.9% at 2 years and 60.6% at 5 years. Of the 58 patients, 13 (22.4%) developed recurrent PJI, three (5.2%) aseptic loosening, and one (1.7%) periprosthetic fracture. Multivariate analysis revealed that obesity (hazard ratio (HR), 3.11), high-virulent pathogen (HR, 3.44), and polymicrobial infection (HR, 3.59) were independent risk factors for reinfection. Patients showed a mean improvement of 32.8 ± 7.7 in Knee Society Clinical Score (KSCS) and 30.8 ± 11.0 in Knee Society Function Score (KSFS) after successful reconstruction (P<0.001).

CONCLUSIONS

Using hinged knee prosthesis for PJI reconstruction provided an overall implant survival of 70.2% and an infection-free survival of 60.6% at mid-term follow up. Obesity, virulent pathogens, and polymicrobial infections were independent risk factors for infection recurrence.

Platelet-rich plasma lysate displays antibiofilm properties and restores antimicrobial activity against synovial fluid biofilms in vitro

Infectious arthritis is difficult to treat in both human and veterinary clinical practice. Recent literature reports Staphylococcus aureus as well as other gram-positive and gram-negative isolates forming free-floating biofilms in both human and equine synovial fluid that are tolerant to traditional antimicrobial therapy. Using an in vitro equine model, we investigated the ability of platelet-rich plasma (PRP) formulations to combat synovial fluid biofilm aggregates. Synovial fluid was infected, and biofilm aggregates allowed to form over a 2-hour period. PRP was collected and processed into different formulations by platelet concentration, leukocyte presence, and activation or lysis. Infected synovial fluid was treated with different PRP formulations with or without aminoglycoside cotreatment. Bacterial load (colony-forming unit/mL) was determined by serial dilutions and plate counting at 8 hours posttreatment. All PRP formulations displayed antimicrobial properties; however, formulations containing higher concentrations of platelets without leukocytes had increased antimicrobial activity. Lysis of PRP and pooling of the PRP lysate (PRP-L) from multiple horses as compared to individual horses further increased antimicrobial activity. This activity was lost with the removal of the plasma component or inhibition of the proteolytic activity within the plasma. Fractionation of pooled PRP-L identified the bioactive components to be cationic and low-molecular weight (<10 kDa). Overall, PRP-L exhibited synergism with amikacin against aminoglycoside tolerant biofilm aggregates with greater activity against gram-positive bacteria. In conclusion, the use of PRP-L has the potential to augment current antimicrobial treatment regimens which could lead to a decrease in morbidity and mortality associated with infectious arthritis.

BMI is a Better Predictor of Periprosthetic Joint Infection Risk Than Local Measures of Adipose Tissue After TKA

BACKGROUND

Both body mass index (BMI) and local measures of adiposity at the surgical site have been identified as independent risk factors for periprosthetic joint infection (PJI) (periprosthetic joint infection) after total knee arthroplasty (TKA). We aimed to 1) evaluate previously used measures of assessing knee adiposity and 2) determine the best measure for predicting both surgical duration and PJI after TKA.

METHODS

We performed a multicentre retrospective review of 4745 patients who underwent primary TKA between January 2013 and December 2016. Patient demographic information, surgical duration and postoperative infection status within one year were obtained. Preoperative weight-bearing AP and lateral x-rays were analyzed to determine prepatellar adipose thickness, bony width of the tibial plateau, and total soft tissue knee width. The knee adipose index (KAI) was calculated from the ratio of bone to total knee width.

RESULTS

We observed substantial variability in both local measures of adiposity compared with BMI. Neither measure of local knee adipose showed a significant correlation with PJI risk. By contrast, there was a strong correlation between PJI risk and BMI >35 (odds ratio 2.9, 95% CI 1.4-6.1). Surgical duration increased with both BMI and measures of local adipose tissue (KAI and prepatellar fat thickness).

CONCLUSION

Local adipose deposition varies greatly for any given BMI. In this study, BMI was a better predictor of PJI after TKA than local measures of knee adipose tissue.

Characterization of synovial fluid from periprosthetic infection in revision total joint arthroplasty by single-molecule microscopy

Periprosthetic joint infection is among the most common and severe complications in total joint arthroplasty. Today, a combination of different methods is used for diagnosis because no single method with sufficient sensitivity and specificity is available. In this study, we explored the usability of single-molecule microscopy to characterize synovial fluid samples from periprosthetic joint infections. Patients (n = 27) that needed revision arthroplasty underwent the routine diagnostic procedures for periprosthetic joint infection of the University Hospital in Bonn. Additionally, the diffusion rate of two probes, dextran and hyaluronan, was measured in small volumes of periprosthetic synovial fluid samples using single-molecule microscopy. To evaluate the suitability of single-molecule microscopy to detect PJI the AUC for both markers was calculated. The diffusion rate of hyaluronan in periprosthetic synovial fluid from patients with septic loosening was faster than in samples from patients with aseptic loosening. Single-molecule microscopy showed excellent diagnostic performance, with an area under the receiver operating characteristic curve of 0.93, and allowed the detection of periprosthetic joint infection in patients that would be challenging to diagnose with current methods. For the first time, single-molecule microscopy was used to detect periprosthetic joint infection. Our results are encouraging to study the value of single-molecule microscopy in a larger patient cohort. The speed and accuracy of single-molecule microscopy can be used to further characterize synovial fluid, potentially allowing intraoperative diagnosis of periprosthetic joint infections in the future.

Prosthetic joint infections: diagnosis, management, and complications of the two-stage replacement arthroplasty

Despite improved strategies to prevent prosthetic joint infection, as the total number of joint replacements increases, so does the absolute number of infections. Radiography serves as the first-line imaging modality for the assessment of a suspected prosthetic joint infection. Additionally, serial radiographs acquired after a surgery to eradicate a prosthetic joint infection are an important clinical tool. Prosthetic joint infections are often treated with a 2-stage replacement arthroplasty utilizing a prosthesis with antibiotic-loaded acrylic cement. While complications are uncommon with this procedure, imaging may demonstrate periprosthetic fractures, as well as spacer migration, joint dislocation, and spacer fracture. We describe the classification of prosthetic joint infections, the clinical and imaging diagnosis, and treatment strategies. Familiarity with the hardware utilized in the management of the prosthetic joint infection, and its potential complications is fundamental to accurate imaging interpretation.

Genotypic and phenotypic changes of Staphylococcus epidermidis during relapse episodes in prosthetic joint infections

Staphylococcus epidermidis is a coagulase-negative bacterium capable of causing recurrent relapses in prosthetic joint infection (PJI). The aim of this study was to determine if Staphylococcus epidermidis isolates from patients with recurrent relapses of prosthetic joint infection (PJI) changed genotypically (pulsed-field gel electrophoresis (PFGE) pattern analysis and genes involved in biofilm formation) and phenotypically (antimicrobial resistance, biofilm formation) during the different episodes. Four patients with PJI recurrent relapses were evaluated clinically and microbiologically. Genotypic and phenotypic characteristics of 31 S. epidermidis isolates were determined. In all cases, PJI was treated with antimicrobial therapy and resection of the prosthesis without reimplantation. Months later, all patients had a relapse episode and treated with rifampin plus vancomycin and surgical debridement. Changes in the antibiotics resistance profile in isolates from patients 1 and 2 were observed in the two episodes. Patient 1 had four clones A, B, C, and D that were distributed differentially in the two episodes. Similarly, patients 2 and 3 had two clones and subclones (E-E1 and F-F1, respectively), and patient 4 had only the clone G in both episodes. The clone F formed small-colony variants (SCVs). High level of biofilm formation was found in all clones, except for clones D and G. Clones/subclones showed a genotypic variation in icaA, sdrF, bap, sesI, and embp genes. The principal coordinate analysis showed that all clones/subclones were different. These results showed that the initial infective clone of S. epidermidis from PJI, changed genotypically and phenotypically after a second relapse as a response to the treatment.

Induction heating for eradicating Staphylococcus epidermidis from biofilm

Aims

Induction heating is a noninvasive, nonantibiotic treatment modality that can potentially be used to cause thermal damage to the bacterial biofilm on the metal implant surface. The purpose of this study was to determine the effectiveness of induction heating on killing Staphylococcus epidermidis from biofilm and to determine the possible synergistic effect of induction heating and antibiotics.

Methods

S. epidermidis biofilms were grown on titanium alloy (Ti6Al4V) coupons for 24 hours (young biofilm) and seven days (mature biofilm). These coupons with biofilm were heated to temperatures of 50°C, 55°C, 60°C, 65°C, 70°C, 80°C, and 90°C for 3.5 minutes and subsequently exposed to vancomycin and rifampicin at clinically relevant concentrations.

Results

For the young biofilm, total eradication was observed at 65°C or higher for 3.5 minutes followed by 24 hours of vancomycin 10 mg/l and rifampicin 1 mg/l. For the mature biofilm, total eradication was observed at 60°C for 3.5 minutes followed by 24 hours of vancomycin 10 mg/l and rifampicin 1 mg/l. Total eradication was also observed at 60°C for 3.5 minutes followed by 24 hours of vancomycin 1 mg/l and rifampicin 1 mg/l followed by another thermal shock of 60°C for 3.5 minutes (two thermal shocks).

Conclusion

Induction heating of Ti6Al4V coupons is effective in reducing bacterial load in vitro for S. epidermidis biofilms. Induction heating and antibiotics have a synergistic effect resulting in total eradication of the biofilm at 60°C or higher for clinically relevant concentrations of vancomycin and rifampicin.

Cite this article:Bone Joint Res. 2020;9(4):192–199.

Prosthetic joint infections: clinical management, diagnosis, and treatment

PURPOSE OF REVIEW

Prosthetic joint infections (PJIs) represent one of the most disastrous complications in prosthetic surgery, requiring long hospitalization, prolonged antimicrobial treatment and repeated surgical interventions. No gold standard test to formulate diagnosis exist. A combination of high index of suspicion, physical examination, microbiological and biohumoral investigations is required. Therapeutical approach should be based on a multidisciplinary team. In our center, a two-stage approach is preferred. As regards the choice of the empirical antibiotic backbone, individual risk factors for multiple-drug resistant (MDR) pathogens should be considered. Several studies enhance the possibility to shorten the length of antibiotic couses.

RECENT FINDINGS

Some interesting improvements have been made in the setting of PJIs management. As regards diagnosis, novel biomarkers and nuclear imaging are acquiring more importance. Molecular biology techniques also offer the possibility to formulate rapid microbiological identification. The pattern of PJIs is evolving towards higher rates of MDR causes. During the last decade, a number of new antibiotic molecules with activity against MDRs have been approved. Some of them are also available either in oral formulation or as long-acting compounds, offering the opportunity for early patient's discharge, with expected healthcare costs saving.

SUMMARY

Management of PJIs still represents a major threat for clinicians. Improvements in surgical techniques and antibiotic pipeline promise to revolutionize the approach in next years. Despite data from our experience confirm the efficacy of shorter antibiotic courses and the value of new molecules, randomized clinical trials are lacking. More data are needed in order to modify the routine clinical practice.

Diagnosis of Periprosthetic Hip Joint Infection Using MRI with Metal Artifact Reduction at 1.5 T

Background MRI with metal artifact reduction has gained importance in assessment of pain with total hip arthroplasty (THA). However, its role in diagnosis of periprosthetic joint infection (PJI) has not been well defined. Purpose To evaluate findings of PJI after THA and to determine the diagnostic performance of 1.5-T MRI with metal artifact reduction. Materials and Methods Dedicated compressed sensing-based slice encoding for metal artifact correction 1.5-T MRI examinations (from January 2015 to April 2018) in patients with THA PJI (infection group) and noninfected THA (control group) were retrospectively evaluated by two musculoskeletal radiologists. Fisher exact test was used to compare the groups. Sensitivity, specificity, and accuracy were evaluated for each finding. Interobserver reliability was assessed with κ statistics. Results Forty patients (mean age, 69 years ± 11 [standard deviation]; 26 men) in the infection group and 100 patients (mean age, 67 years ± 11; 42 men) in the control group were evaluated. Periosteal reaction, capsule edema, and intramuscular edema differed between the two groups (P < .001 for each finding). Periosteal reaction was found in 31 of 40 patients with infection and 10 of 100 participants in the control group (sensitivity, 78%; specificity, 90%; accuracy, 86%); capsule edema was found in 33 of 40 (infection group) and five of 100 (control group) (sensitivity, 83%; specificity, 95%; accuracy, 91%); and intramuscular edema was found in 38 of 40 (infection group) and 14 of 100 (control group) (sensitivity, 95%; specificity, 86%; accuracy, 89%). Interobserver agreement was almost perfect, with κ values between 0.88 and 0.92. No difference between the two groups was found regarding the presence of osteolysis (infection group, 23 of 40; control group, 60 of 100), bone marrow edema (39 of 40 vs 87 of 100), effusion (20 of 40 vs 26 of 100), abductor tendon lesion (22 of 40 vs 62 of 100), or bursitis (14 of 40 vs 34 of 100) (P > .05 for each finding). Conclusion The presence of periosteal reaction, capsule edema, and intramuscular edema after total hip arthroplasty at 1.5-T MRI with metal artifact reduction had a high accuracy in evaluation of periprosthetic joint infection. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Zanetti in this issue.

Prevalence and burden of orthopaedic implantable-device infections in Italy: a hospital-based national study

BACKGROUND

Healthcare-associated infections (HAIs) represent a serious burden to individual safety and healthcare sustainability. Identifying which patients, procedures and settings are most at risk would offer a significant contribution to HAI management and prevention. The purpose of this study is to estimate 1) orthopaedic implantable device-related infection (OIDRI) prevalence in Italian hospitals and 2) the gap between the remuneration paid by the Italian healthcare system and the real costs sustained by Italian hospitals to treat these episodes.

METHODS

This is a cross-sectional study based on hospital discharge forms registered in 2012 and 2014. To address the first goal of this study, the national database was investigated to identify 1) surgical procedures associated with orthopaedic device implantation and 2) among them, which patient characteristics (age, sex), type of admission, and type of discharge were associated with a primary diagnosis of infection. To address the second goal, 1) each episode of infection was multiplied by the remuneration paid by the Italian healthcare system to the hospitals, based on the diagnosis-related group (DRG) system, and 2) the total days of hospitalization required to treat the same episodes were multiplied by the average daily cost of hospitalization, according to estimates from the Ministry of the Economy and Finance (MEF).

RESULTS

In 2014, 1.55% of the total hospitalizations for orthopaedic device implantation procedures were associated with a main diagnosis of infection, with a negligible increase of 0.04% compared with 2012. Hip and knee replacement revisions, male patients and patients older than 65 years were more exposed to infection. A total of 51.63% of patients were planned admissions to the hospital, 68.75% had an ordinary discharge to home, and 0.9% died. The remuneration paid by the healthcare system to the hospitals was € 37,519,084 in 2014, with 3 DRGs covering 70.6% of the total. The cost of the actual days of hospitalization to treat these episodes was 17.5 million more than the remuneration received.

CONCLUSIONS

The OIDRI prevalence was lower than that described in recent surveys in acute care settings, although the numbers were likely underestimated. The cost of treatment varied significantly depending on the remuneration system adopted.

Epidemiology of Revision Total Hip Arthroplasty: An Indian Experience

BACKGROUND

With increasing numbers of primary total hip replacement (THR), there has been a substantial increase in revision total hip replacement (RTHR) surgeries. RTHR are complex joint reconstruction surgeries involving significant cost, expertise and infrastructure. With its significant socioeconomic impact, we need to keep a close watch on the epidemiological trends of these procedures.

METHODS

We prospectively studied the first-time RTHR performed at our institution for a 7-year period (2011-2017). We looked at patient demographics, the workload of RTHR and its etiology. We reviewed the microbiological profiles of septic revisions.

RESULTS

Of the 1244 THR procedures performed, 260 (21%) were first-time revisions. The predominant cause of revisions was a prosthetic infection (38%) followed by aseptic loosening (33%), instability (15%), peri-prosthetic fracture (11%) and implant breakage (3%). In the aseptic loosening group, 55% of cases had primary cemented implant, 44% had only stem loosening, 31% had cup loosening and 25% had both cup and stem loosening. In the early, midterm, and late-failure groups, prosthetic infection remained the main cause of failure. In 60% of the septic revisions, the offending organisms could not be identified and of those identified most (77%) were gram negative.

CONCLUSION

In our study, the RTHR burden was 21%, which is similar to historic revision data from the west (1998-2001) and twice as compared to recent trends from the west (9-11%). Unlike western data, which show aseptic loosening (30-60%) as the predominant cause of hip revisions, in our study infection was the number one cause (38%).

The Performance of a Dithiothreitol-Based Diagnostic System in Diagnosing Periprosthetic Joint Infection Compared to Sonication Fluid Cultures and Tissue Biopsies

PURPOSE

The aim of this study was to evaluate the performance of a commercially available dithiothreitol (DTT) kit for routine use in diagnosing periprosthetic joint infections (PJIs) in comparison to conventional microbiological tissue specimens and sonication procedures in a maximal care hospital.

METHODS

We applied the DTT system in 40 consecutive cases of revision arthroplasty (23 PJIs and 17 aseptic revisions), with an exchange or a removal of components. The hardware components were split between the DTT system and the conventional sonication procedure. At least three tissue biopsies and a joint fluid specimen were sent for microbiological and histopathological analysis. Data was analysed retrospectively to compare between the different methods.

RESULTS

Cultures of the DTT fluid showed a sensitivity of 65% and specificity of 100%, as referenced to conventional microbiological cultures. Sonication had better sensitivity (75%) but lower specificity (85%). The categorical agreement of DTT cultures compared to sonication fluid cultures was 78% (31/40). Neither pathogen type, infection duration nor antibiotic pretreatment influenced the accuracy of the DTT, but a low pH in the DTT seemed to be associated with false-negative results.

CONCLUSION

DTT was inferior in sensitivity when diagnosing PJIs compared to sonication fluid cultures and tissue biopsies. A low pH in the DTT fluid correlated with false-negative results. Nevertheless, the closed system of the DTT kit avoids contamination and false-positive results, and DTT can be an alternative where sonication is not available.

Corynebacterium Total Hip and Knee Arthroplasy Prosthetic Joint Infections

Prosthetic joint infections (PJIs) are typically caused by Staphylococcus aureus and coagulase-negative Staphylococci species. Corynebacterium species are microorganisms of the human skin and mucous membranes that are often considered contaminants when grown in culture. In the past, Corynebacterium species were often classified as diphtheroids based on growing as gram-positive rods in aerobic environments, but with advances in technology, the identification of Corynebacterium species has improved. Corynebacterium can cause infection, but there are few case reports of orthopaedic infection. We present 3 cases of total hip arthroplasty and 3 cases of total knee arthroplasty PJI caused by Corynebacterium species. We found a high failure rate of surgical treatment of Corynebacterium PJI, defined as reoperation for infection. This information adds to the limited literature on these organisms in total joint arthroplasty PJI.

Preliminary evaluation of a rapid lateral flow calprotectin test for the diagnosis of prosthetic joint infection

AIMS

This pilot study tested the performance of a rapid assay for diagnosing prosthetic joint infection (PJI), which measures synovial fluid calprotectin from total hip and knee revision patients.

METHODS

A convenience series of 69 synovial fluid samples from revision patients at the Norfolk and Norwich University Hospital were collected intraoperatively (52 hips, 17 knees) and frozen. Synovial fluid calprotectin was measured retrospectively using a new commercially available lateral flow assay for PJI diagnosis (Lyfstone AS) and compared to International Consensus Meeting (ICM) 2018 criteria and clinical case review (ICM-CR) gold standards.

RESULTS

According to ICM, 24 patients were defined as PJI positive and the remaining 45 were negative. The overall accuracy of the lateral flow test compared to ICM was 75.36% (52/69, 95% CI 63.51% to 84.95%), sensitivity and specificity were 75.00% (18/24, 95% CI 53.29% to 90.23%) and 75.56% (34/45, 95% CI 60.46% to 87.12%), respectively, positive predictive value (PPV) was 62.07% (18/29, 95% CI 48.23% to 74.19%) and negative predictive value (NPV) was 85.00% (34/40, 95% CI 73.54% to 92.04%), and area under the receiver operating characteristic (ROC) curve (AUC) was 0.78 (95% CI 0.66 to 0.87). Patient data from discordant cases were reviewed by the clinical team to develop the ICM-CR gold standard. The lateral flow test performance improved significantly when compared to ICM-CR, with accuracy increasing to 82.61% (57/69, 95% CI 71.59% to 90.68%), sensitivity increasing to 94.74% (18/19, 95% CI 73.97% to 99.87%), NPV increasing to 97.50% (39/40, 95% CI 85.20% to 99.62%), and AUC increasing to 0.91 (95% CI 0.81 to 0.96). Test performance was better in knees (100.00% accurate (17/17, 95% CI 80.49% to 100.00%)) compared to hips (76.92% accurate (40/52, 95% CI 63.16% to 87.47%)).

CONCLUSION

This study demonstrates that the calprotectin lateral flow assay could be an effective diagnostic test for PJI, however additional prospective studies testing fresh samples are required.Cite this article: Bone Joint Res. 2020;9(5):202-210.

Two-Stage Exchange Arthroplasty for Periprosthetic Joint Infection Following Total Hip or Knee Arthroplasty Is Associated With High Attrition Rate and Mortality

BACKGROUND

We sought to determine the ultimate fate of patients undergoing resection arthroplasty as a first stage in the process of 2-stage exchange and evaluate risk factors for modes of failure.

METHODS

A retrospective case study was performed including all patients with minimum 2-year follow-up who underwent first-stage resection of a hip or knee periprosthetic joint infection from 2008 to 2015. Patient demographics, laboratory, and health status variables were collected. The primary outcome analyzed was defined as failure to achieve an infection-free 2-stage revision. Univariate pairwise comparison followed by multivariate regression analysis was used to determine risk factors for failure outcomes.

RESULTS

Eighty-nine patients underwent resection arthroplasty in a planned 2-stage exchange protocol (27 hips, 62 knees). Mean age was 64 years (range, 43-84), 56.2% were males, and mean follow-up was 56.3 months. Also, 68.5% (61/89) of patients underwent second-stage revision. Of the 61 patients who complete a 2-stage protocol, 14.8% (9/61) of patients failed with diagnosis of repeat or recurrent infection. Mortality rate was 23.6%. Multivariate analysis identified risk factors for failure to achieve an infection-free 2-stage revision as polymicrobial infection (P < .004; adjusted odds ratio [AOR], 7.8; 95% confidence interval [CI], 2.1-29.0), McPherson extremity grade 3 (P < .024; AOR, 4.1; 95% CI, 1.2-14.3), and history of prior resection (P < .013; AOR, 4.7; 95% CI, 1.4-16.4).

CONCLUSION

Patients undergoing resection arthroplasty for periprosthetic joint infection are at high risk of death (24%) and failure to complete the 2-stage protocol (32%). Those who complete the 2-stage protocol have a 15% rate of reinfection at 4.5-year follow-up.

Prescribing Patterns and Patient Outcomes for Bone and Joint Infections Treated with Cefazolin and Probenecid: A Retrospective Observational Study

BACKGROUND

Previous studies have described the use of cefazolin with probenecid to treat uncomplicated skin and soft-tissue infections. Some prescribers are extrapolating from this evidence to treat more invasive infections, which have a greater potential for poor outcomes, including treatment failure that could lead to increased morbidity and mortality. Information supporting cefazolin with probenecid as effective treatment in this context is needed.

OBJECTIVES

To describe prescribing patterns and outcomes for patients who received cefazolin with probenecid for the treatment of bone and joint infections.

METHODS

This single-centre retrospective study involved adult outpatients for whom cefazolin and probenecid were prescribed for bone and joint infections between April 1, 2012, and March 31, 2017. Patient charts were reviewed, and data were collected for clinical and microbiological variables using a standardized data collection form.

RESULTS

In a total of 80 cases, the patient received cefazolin and probenecid for treatment of a bone or joint infection, of which 69 cases met the inclusion criteria. In most cases (n = 67), the patients were treated with cefazolin 2 g IV plus probenecid 1 g PO, both given twice daily. Completion of prescribed treatment occurred in 56 patient cases (81%), resolution of signs and symptoms in 53 (77%), readmission to hospital in 11 (16%), recurrence of infection in 6 (9%), and treatment failure requiring a change in therapy in 7 (10%).

CONCLUSIONS

The effectiveness of cefazolin and probenecid for the treatment of bone and joint infections appears to be similar to that of standard treatment, as reported in the literature. Antibiotic effectiveness is difficult to determine conclusively in a retrospective analysis, so these results should be interpreted with caution, but they may stimulate further research.

Reinfection and re-revision rates of 113 two-stage revisions in infected TKA

Introduction: Two-stage revision is the most frequently performed revision procedure of a (suspected) periprosthetic joint infection (PJI) after total knee arthroplasty (TKA). The reported results of this treatment show large variability between studies, ranging between 0 - 40 percent failure. The purposes of this study were to determine long term (1) reinfection rate, (2) re-revision rates for any reason, and (3) the reinfection rate of patients with positive cultures at reimplantation.

Methods: We prospectively followed and retrospectively reviewed 113 consecutive two-stage revision TKAs, performed between 2003 and 2013 in our clinic with a minimum follow-up of 2 years. Diagnosis of PJI was based on the major Musculoskeletal Infection Society criteria for PJI.

Results: After a mean follow-up of 94 months (range 24-172 months), infection recurred in 23 cases (23%). Of these, nine cases (9%) were defined as relapse (same micro-organism as index revision) and in 14 cases another causative was found (14%). In 11 patients debridement, antibiotics and retention of the prosthesis successfully eradicated the reinfection. After overall follow-up 17 patients (17%) underwent re-revision surgery, 11 patients (11%) due to an infection and 6 patients (6%) for aseptic reasons.

Conclusions: Treatment of a (suspected) infection of a TKA by a two-stage revision had acceptable results based on re-revision and re-infection rates in the long term (>5 years), resembling the short-term results (<2 years). Focussing on the cultures at the index two-stage revision, episodes of relapse and new infections during follow-up were almost equally divided. Reinfection rates were higher in cases with positive cultures at reimplantation. Patients should be counselled appropriately in this particular situation.

Development of a Novel and Rapid Antibody-Based Diagnostic for Chronic Staphylococcus aureus Infections Based on Biofilm Antigens

Prosthetic joint infections are difficult to diagnose and treat due to biofilm formation by the causative pathogens. Pathogen identification relies on microbial culture that requires days to weeks, and in the case of chronic biofilm infections, lacks sensitivity. Diagnosis of infection is often delayed past the point of effective treatment such that only the removal of the implant is curative. Early diagnosis of an infection based on antibody detection might lead to less invasive, early interventions. Our study examined antibody-based assays against the Staphylococcus aureus biofilm-upregulated antigens SAOCOL0486 (a lipoprotein), glucosaminidase (a domain of SACOL1062), and SACOL0688 (the manganese transporter MntC) for detection of chronic S. aureus infection. We evaluated these antigens by enzyme-linked immunosorbent assay (ELISA) using sera from naive rabbits and rabbits with S. aureus-mediated osteomyelitis, and then we validated a proof of concept for the lateral flow assay (LFA). The SACOL0688 LFA demonstrated 100% specificity and 100% sensitivity. We demonstrated the clinical diagnostic utility of the SACOL0688 antigen using synovial fluid (SF) from humans with orthopedic implant infections. Elevated antibody levels to SACOL0688 in clinical SF specimens correlated with 91% sensitivity and 100% specificity for the diagnosis of S. aureus infection by ELISA. We found measuring antibodies levels to SACOL0688 in SF using ELISA or LFA provides a tool for the sensitive and specific diagnosis of S. aureus prosthetic joint infection. Development of the LFA diagnostic modality is a desirable, cost-effective option, potentially providing rapid readout in minutes for chronic biofilm infections.

Using Bacteriophages as a Trojan Horse to the Killing of Dual-Species Biofilm Formed by Pseudomonas aeruginosa and Methicillin Resistant Staphylococcus aureus

Pseudomonas aeruginosa and Staphylococcus aureus are pathogens able to colonize surfaces and form together a mixed biofilm. Dual-species biofilms are significantly more resistant to antimicrobials than a monomicrobial community, leading to treatment failure. Due to their rapid bactericidal activity, the self-amplification ability and the biofilm degrading properties, bacteriophages represent a promising therapeutic option in fighting biofilm-related infections. In this study, we investigated the effect of either the simultaneous or staggered application of commercially available phages and ciprofloxacin versus S. aureus/P. aeruginosa dual-species biofilms in vitro. Biofilms were grown on porous glass beads and analyzed over time. Different techniques such as microcalorimetry, sonication and scanning electron microscopy were combined for the evaluation of anti-biofilm activities. Both bacterial species were susceptible to ciprofloxacin and to phages in their planktonic form of growth. Ciprofloxacin tested alone against biofilms required high concentration ranging from 256 to >512 mg/L to show an inhibitory effect, whereas phages alone showed good and moderate activity against MRSA biofilms and dual-species biofilms, respectively, but low activity against P. aeruginosa biofilms. The combination of ciprofloxacin with phages showed a remarkable improvement in the anti-biofilm activity of both antimicrobials with complete eradication of dual-species biofilms after staggered exposure to Pyophage or Pyophage + Staphylococcal phage for 12 h followed by 1 mg/L of ciprofloxacin, a dose achievable by intravenous or oral antibiotic administration. Our study provides also valuable data regarding not only dosage but also an optimal time of antimicrobial exposure, which is crucial in the implementation of combined therapies.

Antibiotic-Loaded Hydrogel Coating to Reduce Early Postsurgical Infections in Aseptic Hip Revision Surgery: A Retrospective, Matched Case-Control Study

Periprosthetic joint infections (PJIs) are a cause of frequent implant failure in revision hip replacement surgery. The purpose of this study is to evaluate the onset of early postoperative infections in patients who underwent hip surgery with cementless prostheses treated with an antibiotic loaded hydrogel on their surface, in addition to systemic prophylaxis, and compare them to a control group. The secondary objective was to evaluate the onset of any local and systemic adverse effects and interference with bone ingrowth processes and functional recovery. A retrospective observational study was conducted on patients who underwent revision hip surgery by performing a 1:1 match between patients treated with an antibiotic hydrogel (ALH) and the control patients. The incidence of PJIs was assessed with a minimum of six months follow-up. Seventeen patients treated with the ALH were compared with 17 patients from the control group. No PJIs were reported in the ALH group versus the six cases encountered in the control group (p < 0.0001). No significant differences were reported with regard to prosthetic osseointegration and functional results, nor were there side effects in the ALH group. Despite the low sample size, the use of on-site prophylaxis with ALH has proven effective and safe in reducing the risk of PJIs in patients with a high risk for infections. Further studies are needed to validate these results in other implant-related surgeries.

Peri-Prosthetic Joint Infection of the Knee Causes High Levels of Psychosocial Distress: A Prospective Cohort Study

Background: Peri-prosthetic joint infection (PJI) is a major complication of knee arthroplasty that can cause long-term disability. In addition to its physical impact, there is a clear psychological burden that has not been measured yet. We hypothesized that the psychosocial burden of PJI can be assessed quantitatively using standardized questionnaires and may be correlated with treatment stage. Methods: Thirty-one patients were enrolled in this longitudinal prospective cohort study from August 2015 to November 2016. Participants had clinically established knee PJI after primary total knee replacement in osteoarthritis according to the Musculoskeletal Infection Society criteria and underwent a standardized two-stage protocol. After explantation of the prosthesis and implantation of a polymethylmethacrylate knee spacer, patients were treated with organism-specific intravenous antibiotics for two weeks, followed by oral antibiotics for four weeks; and then reimplantation was performed in all cases. Psychometrically validated standardized questionnaires were used to measure psychosocial stress via self-assessment at four time points: (1) Before explantation of the prosthesis; (2) after explantation; (3) after the antibiotic treatment before reimplantation; and (4) three months after reimplantation (follow-up). The Patient Health Questionnaire (PHQ)-4, Short Form (SF)-12 (including PSK and KSK), Questions about Life Satisfaction (FLZ^M) and Fear of Progression (PA-F-KF) (titles and abbreviations in German) scores were interpreted according to cut-off values for depression, fear of progression, anxiety, and quality of life. Results: Eighteen patients (58.1%) showed a PHQ-4 score above the cut-off value for depression at least once, with the highest score before reimplantation (time point 3). On the SF-12, the mean subtest mental scale (PSK) score was 42.6 (± 14.5), and the mean subtest physical scale (KSK) score was 26.9 (± 7.5) over the four time points, which was significantly lower than that of the general German population (PSK 53.1, KSK 44.0; p < 0.05). The SF-12 scores did not change significantly over time. On the FLZ, health was least satisfactory, followed by recreational activities and work. On the PA-F-KF, patients had the greatest fear of being dependent on outside help, drastic medical interventions, and infection progression. The mean PA-F-KF value was 31.24 (± 9.60; values ≥34 are regarded as critical). Conclusion: Peri-prosthetic joint infection is a measurable, relevant psychosocial stressor for patients. Their quality of life and fear of the disease progressing are comparable to those of oncology patients. Routine screening should be conducted to identify affected patients early for appropriate treatment, improving long-term outcomes. Orthopaedic surgeons who treat patients with PJI should initiate by psychologists as well in order to maintain the patient's long-term quality of life.

The Effect of Vancomycin on the Viability and Osteogenic Potential of Bone-Derived Mesenchymal Stem Cells

Traditionally, methicillin-resistant Staphylococcus aureus (MRSA) is treated with vancomycin, administrated intravenously or applied directly onto infected tissue. The effect of direct (as opposed to systemic) vancomycin treatment on bone formation and remodelling is largely unknown. The minimal inhibitory concentration (MIC) of vancomycin was determined by adding 200 μL of different concentrations (1-20 μg/mL) to actively growing cultures of S. aureus Xen 31 (methicillin-resistant) and S. aureus Xen 36 (methicillin-sensitive), respectively, and recording changes in optical density over 24 h. Bone marrow-derived and proximal femur-derived mesenchymal stem cells (bmMSCs and pfMSCs) from rat femora were exposed to 1 × MIC (5 μg/mL) and 4 × MIC (20 μg/mL) of vancomycin for 7 days. Cell viability was determined by staining with crystal violet and MTT (3-(4,5- di methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), respectively, and osteogenic differentiation by staining with Alizarin Red S. Vancomycin had no effect on the viability of bmMSCs and pfMSCs, even at high levels (20 μg/mL). The osteogenic differentiation of pfMSCs was partially inhibited, while osteogenesis in bmMSCs was not severely affected. The direct application of vancomycin to infected bone tissue, even at excessive levels, may preserve the viability of resident MSC populations.

Genomic characterization and outcome of prosthetic joint infections caused by Staphylococcus aureus

Staphylococcus aureus is a commensal colonizing the skin and mucous membranes. It can also act as a pathogen, and is the most common microorganism isolated from prosthetic joint infections (PJIs). The aim of this study was to explore the genomic relatedness between commensal and PJI S. aureus strains as well as microbial traits and host-related risk factors for treatment failure. Whole-genome sequencing (WGS) was performed on S. aureus isolates obtained from PJIs (n = 100) and control isolates from nares (n = 101). Corresponding clinical data for the PJI patients were extracted from medical records. No PJI-specific clusters were found in the WGS phylogeny, and the distribution of the various clonal complexes and prevalence of virulence genes among isolates from PJIs and nares was almost equal. Isolates from patients with treatment success and failure were genetically very similar, while the presence of an antibiotic-resistant phenotype and the use of non-biofilm-active antimicrobial treatment were both associated with failure.In conclusion, commensal and PJI isolates of S. aureus in arthroplasty patients were genetically indistinguishable, suggesting that commensal S. aureus clones are capable of causing PJIs. Furthermore, no association between genetic traits and outcome could be demonstrated, stressing the importance of patient-related factors in the treatment of S. aureus PJIs.

Neisseria meningitidis as a Cause of Septic Arthritis: An Unusual Case of Periprosthetic Joint Infection

One of the most feared complications after arthroplasty is infection due to its significant impact on patient morbidity. Infection may transfer to the joint at the time of surgery or be seeded, haematologically, to the prosthetic joint from another infection source. In this case, a 72-year-old female presented with symptoms of septic arthritis seven years after her original arthroplasty surgery. At presentation, she denied trauma and any comorbidity which would predispose her to infection. Culturing of samples taken revealed the patient was infected with Neisseria meningitidis, and the patient underwent a DAIR procedure. She continued postoperative long-term antimicrobial therapy with resolution of her infection. Follow-up at one year showed complete resolution of the patient's illness with a return to premorbid baseline. To our knowledge, this is the third reported case of septic arthritis caused by Neisseria meningitidis in a prosthetic joint in the literature.

Assessment of a Multiplex Serological Test for the Diagnosis of Prosthetic Joint Infection: a Prospective Multicentre Study

Introduction: The diagnosis of prosthetic joint infections (PJIs) can be difficult in the chronic stage and is based on clinical and paraclinical evidence. A minimally invasive serological test against the main pathogens encountered during PJI would distinguish PJI from mechanical loosening. Methods: We performed a prospective, multicentre, cross-sectional study to assess the contribution of serology in the diagnosis of PJI. Over a 2-year period, all patients undergoing prosthesis revision were included in the study. A C-reactive protein assay and a serological test specifically designed against 5 bacterial species (Staphylococcus aureus, S. epidermidis, S. lugdunensis, Streptococcus agalactiae, Cutibacterium acnes) were performed preoperatively. Five samples per patient were taken intraoperatively during surgery. The diagnosis of PJI was based on clinical and bacteriological criteria according to guidelines. Results: Between November 2015 and November 2017, 115 patients were included, 49 for a chronic PJI and 66 for a mechanical problem. Among patients with PJI, a sinus tract was observed in 32.6% and a C-reactive protein level ≥10 mg/L in 74.5%. The PJI was monomicrobial in 43 cases (targeted staphylococci, 24; S. agalactiae, 1; C. acnes, 2; others, 16), and polymicrobial in 6 cases (12.2%). Sensitivity, specificity, positive predictive value and negative predictive value were 75.0%, 82.1%, 58.3% and 90.8%, respectively, for targeted staphylococci. Specificity/negative predictive value was 97.3%/100% for S. agalactiae and 83.8% /96.9% for C. acnes. Conclusions: The serological tests are insufficient to affirm the diagnosis of PJI for the targeted bacteria. Nevertheless, the excellent NPV may help clinicians to exclude PJI.