Improved identification of polymicrobial infection in total knee arthroplasty through sonicate fluid cultures

Differences in Diagnostic Sensitivity of Cultures Between Sample Types in Periprosthetic Joint Infections: A Systematic Review and Meta-Analysis

BACKGROUND

Differences between the bacterial culture results of the preoperative fluid, intraoperative tissue, and sonication fluid of implants in the diagnosis of periprosthetic joint infection (PJI) are important issues in clinical practice. This study aimed to identify the differences in pooled diagnostic accuracy between culture sample types for diagnosing PJI by performing a systematic review and meta-analysis.

METHODS

This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement. A comprehensive literature search of PubMed, Cumulative Index to Nursing and Allied Health Literature, and Cochrane Library databases was performed. Data extraction and study assessment using the quality assessment of diagnostic accuracy studies were performed independently by two reviewers. The pooled sensitivity, specificity, summary receiver operating characteristic curve, and area under the summary receiver operating characteristic curve were estimated for each sample type.

RESULTS

There were thirty-two studies that were included in the analysis after screening and eligibility assessment. The pooled sensitivities of preoperative fluid, intraoperative tissue, and sonication fluid for the diagnosis of PJI were 0.63 (95% confidence interval [CI] 0.56 to 0.70), 0.71 (95% CI 0.63 to 0.79), and 0.78 (95% CI 0.68 to 0.85), while the specificities were 0.96 (95% CI 0.93 to 0.98), 0.92 (95% CI 0.86 to 0.96), and 0.91 (95% CI 0.83 to 0.95), respectively. The area under the curves for preoperative fluid, intraoperative tissue, and sonication fluid were 0.86, 0.88, and 0.90, respectively.

CONCLUSIONS

Sonication fluid culture demonstrated better sensitivity compared with the conventional culture method, and preoperative fluid culture provided lower sensitivity in diagnosing PJI.

Latent infections in conversion total hip arthroplasty following internal fixation of femoral neck fractures: a systematic review and meta-analysis of diagnostic methods

BACKGROUND

Accurate diagnosis of latent infections prior to conversion total hip arthroplasty (THA) following internal fixation of femoral neck fractures is crucial for successful surgical outcomes. This systematic review aimed to provide a comprehensive evaluation of the current literature regarding the diagnosis of latent infections before conversion THA.

METHODS

Systematic search of PubMed, EMBASE, and Cochrane (CENTRAL) databases was conducted, and the diagnostic accuracy of various markers and techniques was assessed. The quality of the included studies was evaluated using the QUADAS-2 instrument.

RESULTS

Five studies comprising 661 patients were included in the review. Pooled analysis using C-reactive protein (CRP) as a diagnostic marker resulted in a sensitivity and specificity of 72% and 76%, respectively, while using erythrocyte sedimentation rate (ESR) yielded a sensitivity and specificity of 75% and 78%, respectively. Fibrinogen and platelet count showed lower sensitivity and specificity compared to CRP and ESR. The best combined markers were CRP and serum platelet count, with a sensitivity of 76% and specificity of 86% based on one study.

CONCLUSION

Our review underscored the limitations and inconsistencies present in current diagnostic methods for latent infections in conversion surgery. Future research needs to focus on standardizing threshold values, exploring the potential of synovial fluid analysis, imaging techniques, and molecular methods, as well as developing tailored diagnostic algorithms.

PROSPERO

CRD42023394757.

Optimizing the use of low-frequency ultrasound for bacterial detachment of in vivo biofilms in dental research-a methodological study

OBJECTIVES

Low-frequency, low-intensity ultrasound is commonly utilized in various dental research fields to remove biofilms from surfaces, but no clear recommendation exists in dental studies so far. Therefore, this study aims to optimize the sonication procedure for the dental field to efficiently detach bacteria while preserving viability.

MATERIALS AND METHODS

Initial biofilm was formed in vivo on bovine enamel slabs (n = 6) which were worn by four healthy participants for 4 h and 24 h. The enamel slabs covered with biofilm were then ultrasonicated ex vivo for various time periods (0, 1, 2, 4, 6 min). Colony-forming units were determined for quantification, and bacteria were identified using MALDI-TOF. Scanning electron microscopic images were taken to also examine the efficiency of ultrasonications for different time periods.

RESULTS

Ultrasonication for 1 min resulted in the highest bacterial counts, with at least 4.5-fold number compared to the non-sonicated control (p < 0.05). Most bacteria were detached within the first 2 min of sonication, but there were still bacteria detached afterwards, although significantly fewer (p < 0.0001). The highest bacterial diversity was observed after 1 and 2 min of sonication (p < 0.03). Longer sonication periods negatively affected bacterial counts of anaerobes, Gram-negative bacteria, and bacilli. Scanning electron microscopic images demonstrated the ability of ultrasound to desorb microorganisms, as well as revealing cell damage and remaining bacteria.

CONCLUSIONS

With the use of low-frequency, low-intensity ultrasound, significantly higher bacterial counts and diversity can be reached. A shorter sonication time of 1 min shows the best results overall.

CLINICAL RELEVANCE

This standardization is recommended to study initial oral biofilms aged up to 24 h to maximize the outcome of experiments and lead to better comparability of studies.

Diagnostic accuracy of sonication fluid cultures from prosthetic components in periprosthetic joint infection: an updated diagnostic meta-analysis

BACKGROUND

Periprosthetic joint infection (PJI) is the most serious complication following total joint arthroplasty (TJA) and has a significant impact on patients and the national healthcare system. To date, the diagnosis of PJI is still confronted with dilemmas. The present study investigated the validity of sonication fluid culture (SFC) for removing implants in the diagnosis of PJI after joint replacement.

METHODS

From database establishment to December 2020, relevant literature was retrieved from the PubMed, Web of Science, Embase and Cochrane Library databases. Two reviewers independently performed quality assessment and data extraction to calculate the pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), area under the curve (AUC) and diagnostic odds ratio (DOR) to evaluate the diagnostic value of overall SFC for PJI.

RESULTS

A total of 38 eligible studies including 6302 patients were selected in this study. The pooled sensitivity, specificity, PLR, NLR, and DOR of SFC for PJI diagnosis were 0.77 (95% confidence interval [CI], 0.76-0.79), 0.96 (95% CI, 0.95-0.96), 18.68 (95% CI, 11.92-29.28), 0.24 (95% CI, 0.21-0.29), and 85.65 (95% CI, 56.46-129.94), respectively, while the AUC was 0.92.

CONCLUSION

This meta-analysis showed that SFC was of great value in PJI diagnosis, and the evidence of SFC on PJI was more favorable but not yet strong. Therefore, improvement of the diagnostic accuracy of SFC is still necessary, and the diagnosis of PJI continues to warrant a multiplex approach before and during a revision procedure.

The combined evaluation of fibrinogen and D-dimer levels are a helpful tool to exclude periprosthetic knee infection

This retrospective study was undertaken to (i) define the most appropriate thresholds for serum d-dimer and fibrinogen for differentiating aseptic failure from periprosthetic joint infection (PJI) and (ii) evaluate the predictive value of our d-dimer and fibrinogen threshold compared to previously proposed thresholds. This observational cohort study included consecutive patients who had undergone total knee arthroplasty (TKA) revision between January 2019 and December 2020. International Consensus Meeting diagnostic criteria were used to identify patients affected by the prosthetic infection. Receiver operating characteristic curve analyses assessed the predictive value of the parameters, and the areas under the curves were evaluated. We included 125 patients with a median age of 69 years (53-82) affected by painful TKA. Fifty-seven patients (47%) had PJI. Patients with PJI had higher median d-dimer, fibrinogen, ESR, and CRP when compared to patients believed to be free of PJI. The best threshold values for d-dimer and fibrinogen were 1063 ng/ml (sensitivity 0.72, specificity 0.74) and 420 mg/dl (sensitivity 0.67 and specificity 0.82), respectively. A d-dimer level >1063 ng/ml combined with a fibrinogen level >420 mg/dl had a sensitivity of 0.52, and a specificity of 0.90. We found that an increased d-dimer beyond 1063 ng/ml showed a better predictive value than the previously proposed threshold. The combined determination of d-dimer and fibrinogen displayed high specificity and should be considered an excellent tool to rule out an infection. The accuracy of the proposed cutoffs is more effective than previously reported.

Tissue sampling is non-inferior in comparison to sonication in orthopedic revision surgery

BACKGROUND

The aim of this study was to assess the role of sonication fluid cultures in detecting musculoskeletal infections in orthopedic revision surgery in patients suspected of having peri-prosthetic joint infection (PJI), fracture-related infections (FRI), or postoperative spinal implant infections (PSII).

METHODS

Between 2016 and 2019, 149 cases with a data set including sonication fluid cultures and tissue specimen and histological analysis were included. Accuracy of each diagnostic tool as well as the influence of antibiotic therapy was analyzed. Pathogens identified in the sonication cultures and in the associated tissue samples were compared based on the matching of the antibiograms. Therapeutic benefits were then assessed.

RESULTS

Of 149 cases, 43.6% (n = 65) were identified as PJI, 2.7% (n = 4) as FRI, 12.8% (n = 19) as PSII, 6.7% (n = 10) as aseptic non-union, and 34.2% (n = 51) as aseptic implant loosening. The sensitivity and specificity of tissue and synovial specimens showed no significant difference with respect to sonication fluid cultures (sensitivity/specificity: tissue: 68.2%/96.7%; sonication fluid cultures: 60.2%/98.4%). The administration of antibiotics over 14 days prior to microbiological sampling (n = 40) resulted in a lower sensitivity of 42.9% each. Histological analysis showed a sensitivity 86.3% and specificity of 97.4%. In 83.9% (n = 125) of the cases, the results of sonication fluid cultures and tissue specimens were identical. Different microorganisms were found in only four cases. In 17 cases, tissue samples (n = 5) or sonication (n = 12) were false-negatives.

CONCLUSION

Sonication fluid culture showed no additional benefit compared to conventional microbiological diagnostics of tissue and synovial fluid cultures. Preoperative administration of antibiotics had a clearly negative effect on microbiologic test accuracy. In over 83.9% of the cases, sonication fluid and tissue cultures showed identical results. In the other cases, sonication fluid culture did not further contribute to the therapy decision, whereas other factors, such as fistulas, cell counts, or histological analysis, were decisive in determining therapy.

Addressing the Needs of the Rapidly Aging Society through the Development of Multifunctional Bioactive Coatings for Orthopedic Applications

The unprecedented aging of the world's population will boost the need for orthopedic implants and expose their current limitations to a greater extent due to the medical complexity of elderly patients and longer indwelling times of the implanted materials. Biocompatible metals with multifunctional bioactive coatings promise to provide the means for the controlled and tailorable release of different medications for patient-specific treatment while prolonging the material's lifespan and thus improving the surgical outcome. The objective of this work is to provide a review of several groups of biocompatible materials that might be utilized as constituents for the development of multifunctional bioactive coatings on metal materials with a focus on antimicrobial, pain-relieving, and anticoagulant properties. Moreover, the review presents a summary of medications used in clinical settings, the disadvantages of the commercially available products, and insight into the latest development strategies. For a more successful translation of such research into clinical practice, extensive knowledge of the chemical interactions between the components and a detailed understanding of the properties and mechanisms of biological matter are required. Moreover, the cost-efficiency of the surface treatment should be considered in the development process.

Single-stage total hip arthroplasty after failed fixation of proximal femoral fractures: an increased risk for periprosthetic joint infections?

BACKGROUND

Higher complication rates have been reported for total hip arthroplasty (THA) after osteosynthesis of proximal femur fractures (PFF). This study evaluated the infection risk for conversion of internal fixation of PFF to THA by a single-staged procedure in the absence of clear infection signs.

METHODS

Patients undergoing a one-staged conversion to THA (2013-2018) after prior internal fixation of the proximal femur were included. Preoperative diagnostics with laboratory results, hip aspirations as well as intraoperative microbiology and sonication were assessed. Postoperative complications were recorded as well as patient demographics, duration between initial and conversion to THA, explanted osteosynthesis and implanted THA.

RESULTS

Fifty-eight patients (24 male/34 female, 62.8 ± 14.5 years) were included with a mean time of 3.8 ± 7.5 years between internal fixation and conversion to THA (45 cementless, 3 cemented, 3 hybrid and 7 hybrid inverse THAs). Preoperative mean blood level CRP was 8.36 ± 14 mg/l (reference value < 5 mg/l) and leukocyte count was 7.11 ± 1.84^3/µl (4.5-10.000^3/µl). Fifty patients had intraoperative microbiological diagnostics, with either swabs in 86.2% and/or sonication in 29.3%. Positive microbiological results were recorded in 10% (5 of 50 patients), with pathogens identified being mainly Staphylococcus. Complications after conversion occurred in 9.6% including a postoperative low-grade infection rate of 5.8% after a mean of 2.5 years.

CONCLUSION

This study found a positive microbiological test result in 10% of a one-stage conversion of PFF fixation to THA. Moreover, we found a high infection rate (5.8%) for early postoperative periprosthetic joint infection. Interestingly, CRP has not been proven to be an adequate parameter for low-grade infections or occult colonized implants. Therefore, we recommend a comprehensive pre- and intraoperative diagnostic including hip aspiration, swabs and sonication when considering one-staged revision.

Candida periprosthetic joint infections - risk factors and outcome between albicans and non-albicans strains

Background

Despite its scarcity, fungal periprosthetic joint infection (PJI) is of great clinical relevance as diagnosis and treatment are highly challenging. Previous analyses focused on the treatment rather than the role of the causative fungal agent on clinical outcome. This is the largest study of its kind to evaluate Candida strain–dependent differences in patients with fungal PJI.

Methods

We retrospectively analyzed 29 patients who underwent surgical intervention due to Candida hip or knee PJI in our department from 2010 to 2018. PJI was defined according to IDSA, recurrent PJI according to modified Delphi consensus criteria. Statistical analysis was performed using t-test, chi-square test with Yates correction, and log rank test.

Results

Besides age and affected joint, no significant differences were found between Candida albicans and non-albicans PJI patients (75.83 versus 64.11 years, p = 0.012; 12 hip versus two knee cases, p = 0.013). Most patients received two- (27.59%) or three-stage exchange surgery (41.38%). There was a statistical trend towards an increase in surgery needed in non-albicans Candida PJI (2.92 versus 2.12; p = 0.103). After initial Candida PJI treatment, functional prosthesis implantation was achieved in 72.41% of all patients. At last follow-up, infection-free survival was at 26.79% in Candida albicans versus 72.00% in non-albicans PJI (p = 0.046).

Conclusions

In this study, we found infection-free survival rates to be significantly decreased in patients with albicans compared to non-albicans Candida PJI. While age and affected joint might play a confounding role, we speculate the causative pathogen to play a decisive role in disease progression.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00264-021-05214-y.

Emergence of Antibiotic Resistance Across Two-Stage Revision for Periprosthetic Joint Infection

BACKGROUND

The current preferred treatment for chronic hip and knee periprosthetic joint infection (PJI) involves both surgical intervention and antibiotic treatment as part of a two-stage revision. The purpose of this study is to determine how often patients who underwent a two-stage revision for chronic PJI developed a subsequent antibiotic-resistant infection.

METHODS

We retrospectively reviewed the clinical records of 142 patients who underwent a two-stage revision for a chronic culture-positive PJI from January 2014 to May 2019. Demographic data and risk factors for PJI were identified. Resistance was defined in accordance with microbiology laboratory report and minimum inhibitory concentration. Statistical analysis consisted of descriptive statistics and univariate analysis.

RESULTS

Only 10 of the 142 patients (7.04%) demonstrated emergence of resistance to antibiotics across their two-stage revision. At reimplantation, 25 (17.6%) patients had positive cultures. Of these, 16 patients presented with a novel organism and 9 patients had positive culture for the same organism as the initial infection. During the entire course of the two-stage revision, including spacer exchanges and irrigation and debridement procedures, 15 (10.56%) patients demonstrated persistent infections, whereas 25 (17.6%) patients presented with novel infections. 26 (18.3%) patients had reinfection of the same joint within one year.

CONCLUSION

In the given cohort, there does not appear to be a major emergence of antibiotic resistant organisms in patients undergoing two-stage exchange arthroplasty and antibiotic treatment.

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.

Targeted Swabbing of Implant-Associated Biofilm Formation-A Staining-Guided Sampling Approach for Optimizing Routine Microbiological Diagnostics

Background: Swabbing of implants removed from potentially infected sites represents a time saving and ubiquitously applicable alternative to sonication approaches. The latter bears an elevated risk of processing related contaminations due to the high number of handling steps. Since biofilms are usually invisible to the naked eye, adequate swabbing relies on the chance of hitting the colonized area on the implant. A targeted directed swabbing approach could overcome this detriment. Method: Three dyes were tested at different concentrations for their toxicity on biofilm-associated cells of S. epidermidis, the species most frequently identified as a causative agent of implant-associated infections. Results: Malachite green (0.2%) delivered the highest bacterial recovery rates combined with the best results in biofilm visualization. Its suitability for diagnostic approaches was demonstrated for smooth and rough implant surfaces. Biofilm-covered areas were successfully visualized. Conclusion: Subsequent targeted swab-sampling resulted in a significantly increased bacterial recovery rate compared to a dye-free “random swabbing” diagnostic approach.

Microbial yield from infectious tissues pretreated by various methods: an invitro study

Background

This study aimed to evaluate the effects of different pretreatment methods on the microbial yield from infectious tissues.

Methods

Strains of Staphylococcus aureus (SA), Escherichia coli (EC) and Candida albicans (CA) were used to construct single-surface, full-surface, and internal infection models in sterile pork tissue. Manual milling (MM), mechanical homogenization (MH), sonificated (SF), dithiothreitol (DTT), and direct culture (DC) were used to pretreat these tissues, the microbial yield from different pretreatment methods were recorded and compared. Moreover, periprosthetic tissues collected intraoperatively from periprosthetic joint infection (PJI) patients were used as a verification.

Results

The study showed that the microbial yield from MH pretreatment was significantly higher than that of MM (P < 0.01) and SF pretreatment method (P < 0.01). Furthermore, in the internal infection model, the microbial yield from MH group was also significantly higher than that of SF (P < 0.01), DTT (P < 0.01), and DC group (P < 0.01). Moreover, the number of bacterial colonies obtained from periprosthetic tissues pretreated by MH was significantly higher than pretreated by other pretreatment methods (P = 0.004).

Conclusions

The effects of MH and DTT in microbial yield were significantly higher than that of DC, SF and MM, and these methods can be used to process multiple tissue samples at the same time, which might further improve the diagnostic sensitivity of infectious disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04071-5.

The role of implant sonication in the diagnosis of periprosthetic shoulder infection

BACKGROUND

The aim of this study was to investigate the validity of implant sonication fluid cultures in the diagnosis of shoulder periprosthetic joint infection (PJI) compared with tissue culture.

METHODS

This was a retrospective case-control study analyzing all patients who underwent a revision surgery for any kind of suspected septic or aseptic event due to failed shoulder arthroplasty at our institution between July 2014 and December 2018. The diagnostic validity of implant sonication was analyzed on the basis of the last proposed definition criteria of the International Consensus Meeting and compared with standard tissue cultures.

RESULTS

Of the 72 patients, a total of 28 (38.9%) were classified as infected. Of the 28 infected patients, 20 (71.4%) had an identified organism by tissue cultures, and Cutibacterium acnes was the most commonly isolated pathogen. The sensitivities of sonicate fluid (≥50 CFU/mL) and periprosthetic tissue culture for the diagnosis of periprosthetic shoulder infection were 36% and 61% (P = .016), and the specificities were 97.7% and 100% (P > .99), respectively. If no cutoff value was used in sonication culture, the sensitivity increased to 75% whereas the specificity dropped to 82%. Although there was no significant difference in sensitivity between tissue culture and the no-cutoff sonication fluid culture (61% vs. 75%, P = .125), the specificity of tissue culture was significantly higher (100% vs. 82%, P = .01).

CONCLUSION

Tissue culture showed a higher sensitivity and specificity than implant sonication in the diagnosis of shoulder PJI and should remain the gold standard for microbiological diagnosis of shoulder PJI.

Sonication Leads to Clinically Relevant Changes in Treatment of Periprosthetic Hip or Knee Joint Infection

Background: Diagnosis of periprosthetic joint infection (PJI) can be troublesome. Sonication can be a helpful tool in culturing bacteria that are difficult to detect with standard tissue cultures. Aim of this study is to evaluate the clinical importance of our standardized sonication protocol in detecting periprosthetic joint infection. Materials and methods: All patients with revision surgery of a hip or knee prosthesis between 2011 and 2016 were retrospectively reviewed and divided in two groups: clinically suspected of infection or not suspected of infection. For both tissue culture and implant sonication, calculations of sensitivity and specificity were performed. Clinical relevance of sonication was evaluated by calculating in which percentage of patients' sonication influenced clinical treatment. Results: 226 patients with revision of a total hip prosthesis (122 patients) or a total knee prosthesis (104 patients) were included. Sensitivity of perioperatively taken tissue cultures was 94.3% and specificity was 99.3%. For sonication sensitivity was 80.5% and specificity was 97.8%. In the infection group eight patients (9%) with only one positive tissue culture and a positive sonication fluid culture with the same pathogen were found. Interpretation: Although sensitivity and specificity of sonication was lower compared to tissue cultures, periprosthetic joint infection could only be established in 8 patients (9%) suspected of infection because of a positive result of the sonication fluid culture. Sonication leads to clinically relevant changes in treatment and seems therefore to be a helpful diagnostic tool in clinical practice.

Sonication in shoulder surgery: is it necessary?

PURPOSE

The objective of the present study was to determine whether sonication yields greater sensitivity when compared with the traditional tissue culture in detecting peri-implant infections in shoulder surgery.

METHODS

It is a retrospective study that includes 99 shoulder surgeries with implants explanted. The inclusion criteria required at least four tissue cultures, sonication of the material explanted, and a minimum follow-up of two years. Patients were classified according to the definition of periprosthetic shoulder infection of the 2018 International Consensus Meeting on Orthopedic Infections. The classifications are definitive infection, probable infection, possible infection, and unlikely infection.

RESULTS

Among the 99 surgical procedures, 31 were considered definitive infections, 11 possible/probable infections, and 57 unlikely infections. Considering the cases with a definitive infection, the sensitivity of the tissue culture was 87.09% and the sensitivity of sonication stood at 80.64% (p = 0.406). Analyzing the cases with a definitive infection and those having a possible/probable infection together and comparing them with those with unlikely infection, the sensitivity of sonication was 80.4% and the sensitivity of the tissue culture came to 91.4%. The specificity of the sonication was 98.1% and the specificity of the tissue culture was 99.6%.

CONCLUSION

The sensitivity of sonication in shoulder surgery (80.64%) is not superior to the sensitivity of the tissue culture (87.09%). Specificity remains high with both methods, being 98.1% in the sonication group and 99.6% in the tissue culture. Sonication brings no benefit to the detection of shoulder per-implant infections.

Laboratory-based versus qualitative assessment of α-defensin in periprosthetic hip and knee infections: a systematic review and meta-analysis

INTRODUCTION

Two methods are currently available for the assay of α-defensin: the enzyme-linked immunosorbent assay (ELISA) and the lateral flow test. We aimed to assess the diagnostic accuracy of synovial fluid α-defensin and to compare the accuracy of the laboratory-based test and the qualitative assessment for the diagnosis of hip and knee prosthetic infection.

MATERIALS AND METHODS

We searched (from inception to May 2018) MEDLINE, Scopus, EMBASE, Web of Science, and Cochrane for studies on α-defensin in the diagnosis of periprosthetic joint infection (PJI). Sensitivity, specificity, positive and negative likelihood ratio (LR), and diagnostic odds ratio were analyzed using the bivariate diagnostic random-effects model. The receiver-operating curve for each method was calculated.

RESULTS

We included 13 articles in our meta-analysis, including 1170 patients who underwent total hip and knee arthroplasties revision; 368 (31%) had a joint infection according to MSIS and MSIS-modified criteria. Considering the false-positive result rate of 8% and false-negative result rate of 3%, pooled sensitivity and specificity were 0.90 (95% CI 0.83-0.94) and 0.95 (0.92-0.96), respectively. The area under the curve (AUC) was 0.94 (0.92-0.94). No statistical differences in terms of sensitivity and specificity were found between the laboratory-based and qualitative test. The pooled sensitivity and specificity of the two alpha-defensin assessment methods were: laboratory-based test 0.97 (95% CI 0.93-0.99) and 0.96 (95% CI 0.94-0.98), respectively; qualitative test 0.83 (95% CI 0.73-0.91) and 0.94 (95% CI 0.89-0.97), respectively. The diagnostic odds ratio of the α-defensin laboratory based was superior to that of the qualitative test (1126.085, 95% CI 352.172-3600.702 versus 100.9, 95% CI 30.1-338.41; p < 0.001). The AUC for immunoassay and qualitative tests was 0.97 (0.95-0.99) and 0.91 (0.88-0.99), respectively.

CONCLUSION

Detection of α-defensin is an accurate test for diagnosis of hip and knee prosthetic infections. The diagnostic accuracy of the two alpha-defensin assessment methods is comparable. The lateral flow assay is a valid, rapid, and more available diagnostic tool, particularly to rule out PJI.

The World Association against Infection in Orthopaedics and Trauma (WAIOT) procedures for Microbiological Sampling and Processing for Periprosthetic Joint Infections (PJIs) and other Implant-Related Infections

While implant-related infections continue to play a relevant role in failure of implantable biomaterials in orthopaedic and trauma there is a lack of standardised microbiological procedures to identify the pathogen(s). The microbiological diagnosis of implant-related infections is challenging due to the following factors: the presence of bacterial biofilm(s), often associated with slow-growing microorganisms, low bacterial loads, previous antibiotic treatments and, possible intra-operative contamination. Therefore, diagnosis requires a specific set of procedures. Based on the Guidelines of the Italian Association of the Clinical Microbiologists (AMCLI), the World Association against Infection in Orthopaedics and Trauma has drafted the present document. This document includes guidance on the basic principles for sampling and processing for implant-related infections based on the most relevant literature. These procedures outline the main microbiological approaches, including sampling and processing methodologies for diagnostic assessment and confirmation of implant-related infections. Biofilm dislodgement techniques, incubation time and the role of molecular approaches are addressed in specific sections. The aim of this paper is to ensure a standardised approach to the main microbiological methods for implant-related infections, as well as to promote multidisciplinary collaboration between clinicians and microbiologists.

Diagnosis of peripheral bone and prosthetic joint infections: overview on the consensus documents by the EANM, EBJIS, and ESR (with ESCMID endorsement)

OBJECTIVES

Peripheral bone infection (PBI) and prosthetic joint infection (PJI) are two different infectious conditions of the musculoskeletal system. They have in common to be quite challenging to be diagnosed and no clear diagnostic flowchart has been established. Thus, a conjoined initiative on these two topics has been initiated by the European Society of Radiology (ESR), the European Association of Nuclear Medicine (EANM), the European Bone and Joint Infection Society (EBJIS), and the European Society of Clinical Microbiology and Infectious Diseases (ESCMID). The purpose of this work is to provide an overview on the two consensus documents on PBI and PJI that originated by the conjoined work of the ESR, EANM, and EBJIS (with ESCMID endorsement).

METHODS AND RESULTS

After literature search, a list of 18 statements for PBI and 25 statements for PJI were drafted in consensus on the most debated diagnostic challenges on these two topics, with emphasis on imaging.

CONCLUSIONS

Overall, white blood cell scintigraphy and magnetic resonance imaging have individually demonstrated the highest diagnostic performance over other imaging modalities for the diagnosis of PBI and PJI. However, the choice of which advanced diagnostic modality to use first depends on several factors, such as the benefit for the patient, local experience of imaging specialists, costs, and availability. Since robust, comparative studies among most tests do not exist, the proposed flowcharts are based not only on existing literature but also on the opinion of multiple experts involved on these topics.

KEY POINTS

• For peripheral bone infection and prosthetic joint infection, white blood cell and magnetic resonance imaging have individually demonstrated the highest diagnostic performance over other imaging modalities. • Two evidence- and expert-based diagnostic flowcharts involving variable combination of laboratory tests, biopsy methods, and radiological and nuclear medicine imaging modalities are proposed by a multi-society expert panel. • Clinical application of these flowcharts depends on several factors, such as the benefit for the patient, local experience, costs, and availability.

Diagnostic Accuracy of Serum, Synovial, and Tissue Testing for Chronic Periprosthetic Joint Infection After Hip and Knee Replacements: A Systematic Review

BACKGROUND

Chronic periprosthetic joint infection (PJI) is a devastating complication that can occur following total joint replacement. Patients with chronic PJI report a substantially lower quality of life and face a higher risk of short-term mortality. Establishing a diagnosis of chronic PJI is challenging because of conflicting guidelines, numerous tests, and limited evidence. Delays in diagnosing PJI are associated with poorer outcomes and morbid revision surgery. The purpose of this systematic review was to compare the diagnostic accuracy of serum, synovial, and tissue-based tests for chronic PJI.

METHODS

This review adheres to the Cochrane Collaboration's diagnostic test accuracy methods for evidence searching and syntheses. A detailed search of MEDLINE, Embase, the Cochrane Library, and the grey literature was performed to identify studies involving the diagnosis of chronic PJI in patients with hip or knee replacement. Eligible studies were assessed for quality and bias using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Meta-analyses were performed on tests with sufficient data points. Summary estimates and hierarchical summary receiver operating characteristic (HSROC) curves were obtained using a bivariate model.

RESULTS

A total of 12,616 citations were identified, and 203 studies met the inclusion criteria. Of these 203 studies, 170 had a high risk of bias. Eighty-three unique PJI diagnostic tests were identified, and 17 underwent meta-analyses. Laboratory-based synovial alpha-defensin tests and leukocyte esterase reagent (LER) strips (2+) had the best performance, followed by white blood-cell (WBC) count, measurement of synovial C-reactive protein (CRP) level, measurement of the polymorphonuclear neutrophil percentage (PMN%), and the alpha-defensin lateral flow test kit (Youden index ranging from 0.78 to 0.94). Tissue-based tests and 3 serum tests (measurement of interleukin-6 [IL-6] level, CRP level, and erythrocyte sedimentation rate [ESR]) had a Youden index between 0.61 to 0.75 but exhibited poorer performance compared with the synovial tests mentioned above.

CONCLUSIONS

The quality of the literature pertaining to chronic PJI diagnostic tests is heterogeneous, and the studies are at a high risk for bias. We believe that greater transparency and more complete reporting in studies of diagnostic test results should be mandated by peer-reviewed journals. The available literature suggests that several synovial fluid-based tests perform well for diagnosing chronic PJI and their use is recommended in the work-up of any suspected case of chronic PJI.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Periprosthetic Tibial Fracture with Nonunion and Ascending Prosthetic Joint Infection: A Case Report of an Individual Treatment Strategy

Introduction:

Periprosthetic fractures are severe injuries that demand the surgeon’s full expertise and special diagnostic and therapeutic strategies. A major complication is the occurrence of an infectious nonunion, including an ascending infection from the fracture site to the arthroplasty.

Case Report:

This case report presents on a patient with a well-functioning revision total knee arthroplasty (TKA) who suffered a periprosthetic tibia fracture. Initial treatment with plating failed and the fracture had to be revised due to an infectious non-union with a multidrug-resistant Staphylococcus epidermidis, and its eradication was complicated by septic loosening of the patient’s knee arthroplasty. After multiple revisions of the nonunion, a two-stage exchange arthroplasty with a partial replacement of the distal femur due to a bone defect was necessary to obtain an acceptable result.

Conclusion:

The objective of this case report is to present an individual surgical strategy in a complex case of periprosthetic fracture and TKA with major complications. It is shown that the infection of the bone and implants is a challenging situation for surgical treatment. There is still no optimal management strategy due to missing standards as well as controversies in treatment.

What is the optimal protocol to decontaminate a dropped custom polyethylene component?

BACKGROUND

With advancements in manufacturing technology, custom orthopedic implants have become commercially available. A new concern with these implants is what to do when custom heat-sensitive components are contaminated. While intraoperative decontamination protocols for dropped autograft tissue have been described, no literature describes an intraoperative protocol for decontaminating one-of-a-kind polyethylene implants. The purpose of this work is to describe and evaluate polyethylene decontamination protocols using materials found in the average operating suite that could be used intraoperatively.

METHODS

Sixteen custom polyethylene inserts were contaminated with potting soil and processed in one of four protocols: 1) hydrogen peroxide, 2) chlorhexidine gluconate, 3) povidone-iodine, or 4) control. Following processing, the implants were cultured with swabs or sonication. Each implant was evaluated with one aerobic, one anaerobic, and one fungal culture.

RESULTS

All cultures from implants processed with both the chlorhexidine and povidone-iodine protocols were negative. One colony of Ralstonia species was isolated on the aerobic culture from one of the implants processed with hydrogen peroxide. The remainder of the cultures from implants processed with the hydrogen peroxide protocol were negative. All of the cultures for each culture modality from all of the control implants were positive with florid proliferation.

CONCLUSION

In the rare situation that a custom polyethylene insert becomes contaminated intraoperatively, the surgeon should consider all salvage options. Chlorhexidine and povidone-iodine decontamination protocols eliminated bacterial growth following culture swabs or sonicate taken from the contaminated polyethylene inserts while hydrogen peroxide failed in one case to completely eradicate growth.

Consensus document for the diagnosis of prosthetic joint infections: a joint paper by the EANM, EBJIS, and ESR (with ESCMID endorsement)

Background

For the diagnosis of prosthetic joint infection, real evidence-based guidelines to aid clinicians in choosing the most accurate diagnostic strategy are lacking.

Aim and Methods

To address this need, we performed a multidisciplinary systematic review of relevant nuclear medicine, radiological, orthopaedic, infectious, and microbiological literature to define the diagnostic accuracy of each diagnostic technique and to address and provide evidence-based answers on uniform statements for each topic that was found to be important to develop a commonly agreed upon diagnostic flowchart.

Results and Conclusion

The approach used to prepare this set of multidisciplinary guidelines was to define statements of interest and follow the procedure indicated by the Oxford Centre for Evidence-based Medicine (OCEBM).

Electronic supplementary material

The online version of this article (10.1007/s00259-019-4263-9) contains supplementary material, which is available to authorized users.

Comparison of different human tissue processing methods for maximization of bacterial recovery

Tissues are valuable microbiological samples that have proved superiority over swabs. Culture of tissue samples is used in the diagnosis of a variety of infections. However, as well as factors such as the site of obtaining the sample, the number of samples, and previous antibiotic use, the method of tissue processing may have an important effect on sensitivity. Data from the literature comparing different tissue processing methods is very limited. This study aimed to compare different mechanical and chemical methods of tissue processing in terms of efficacy and retaining the viability of the bacteria in the tissues. Standard suspensions of Staphylococcus aureus and Escherichia coli were prepared and treated differently to test the effect of that treatment on bacterial viability. Artificially inoculated pork tissue and known infected human tissue samples were then processed by different methods prior to culture, and results were compared. Percentages of reduction in the number of viable bacteria compared to the control by homogenization was similar to 5-min dithiothreitol treatment but significantly lower than bead beating. Bacterial recovery from homogenized human tissues was significantly higher than from any other method of treatment. Although bead beating could be the most efficient method in obtaining a homogeneous tissue product, it significantly reduces the number of viable bacteria within tissues. Homogenization offers the most effective easily controllable retrieval of bacteria from tissue and retains their viability. Guidelines for diagnosing infections using tissue samples should include a standardized processing method.

Usefulness of Culturing the Periprosthetic Membrane or Neosynovium for the Diagnosis of Infection During Hip and Knee Revision Arthroplasty

INTRODUCTION

Identification of microorganisms is critical for correct management of an infected arthroplasty. Our hypothesis is that the culture yield depends on the location around the prosthesis from which samples are obtained.

METHODS

This prospective study included 298 revisions of the hip (123) and knee (175). We compared the yield of the intraoperative samples obtained, which included synovial fluid (two), neosynovium (two), and periprosthetic membrane (two).

RESULTS

Cultures were positive in 28 cases, in which 15 had the same diagnosis considering either the neosynovium or the membrane, and there were 3 cases in which the infection could have been diagnosed only by considering the combination of both. In all, there were 8 cases in which the infection might have been misdiagnosed unless considering a combination of both solid tissue samples (P = 0.004).

CONCLUSIONS

The yields of the periprosthetic membrane and neosynovium do not differ significantly, and we recommend considering a combination of both.

LEVEL OF EVIDENCE

Diagnostic Level II.

Cerclages after Femoral Osteotomy Are at Risk for Bacterial Colonization during Two-Stage Septic Total Hip Arthroplasty Revision

Aims: In cases of a two-stage septic total hip arthroplasty (THA) exchange a femoral osteotomy with subsequent cerclage stabilization may be necessary to remove a well-fixed stem. This study aims to investigate the rate of bacterial colonization and risk of infection persistence associated with in situ cerclage hardware in two-stage septic THA exchange.

Patients and Methods: Twenty-three patients undergoing two-stage THA exchange between 2011 and 2016 were included in this retrospective cohort study. During the re-implantation procedure synovial fluid, periprosthetic tissue samples and sonicate fluid cultures (SFC) of the cerclage hardware were acquired.

Results: Seven of 23 (30%) cerclage-SFC produced a positive bacterial isolation. Six of the seven positive cerclage-SFC were acquired during THA re-implantation.

Two of the seven patients (29%) with a positive bacterial isolation from the cerclage hardware underwent a THA-revision for septic complications. The other five patients had their THA in situ at last follow-up.

Conclusions: Despite surgical debridement and antimicrobial therapy, a bacterial colonization of cerclage hardware occurs and poses a risk for infection persistence. All cerclage hardware should be removed or exchanged during THA reimplantation.

Diagnosing periprosthetic hip joint low-grade infection via arthroscopic neo synovium biopsies

BACKGROUND

There is currently a lack of consensus regarding the most effective diagnostic algorithm for cases of supposed low-grade infection after total hip arthoplasty (THA).

OBJECTIVE

The aim of this study was to assess reliability in the use of biopsies, obtained by hip arthroscopy, to detect a periprosthetic hip joint infection (PJI).

METHODS

From 2012 to 2016, diagnostic arthroscopy of the hip joint was performed in 20 patients with a supposed PJI following THA. In 10 of these patients, the THA was revised for various reasons after diagnostic arthroscopy. The microbiological and histological findings of the biopsies obtained by arthroscopy were compared to findings from intraoperative samples of the revision arthroplasty.

RESULTS

For arthroscopic biopsies, we detected a sensitivity of 1.00 (95% confidence interval [CI] 0.40-1.00), a specificity of 0.83 (95% CI 0.36-1.00), a positive predictive value of 0.80 (95% CI 0.28-1.00), and a negative predictive value of 1.00 (95% CI 0.48-1.00). The accuracy was 0.90.

CONCLUSIONS

The analysis of arthroscopic biopsies represents a helpful tool to verify or rule out a PJI in selected patients. Nevertheless, minimally invasive diagnostic tools (e.g., laboratory analysis and aspiration) should be utilized beforehand.

Value of PCR in sonication fluid for the diagnosis of orthopedic hardware-associated infections: Has the molecular era arrived?

INTRODUCTION

Bone healing disturbance following fracture fixation represents a continuing challenge. We evaluated a novel fully automated polymerase chain reaction (PCR) assay using sonication fluid from retrieved orthopedic hardware to diagnose infection.

PATIENTS AND METHODS

In this prospective diagnostic cohort study, explanted orthopedic hardware materials from consecutive patients were investigated by sonication and the resulting sonication fluid was analyzed by culture (standard procedure) and multiplex PCR (investigational procedure). Hardware-associated infection was defined as visible purulence, presence of a sinus tract, implant on view, inflammation in peri-implant tissue or positive culture. McNemar's chi-squared test was used to compare the performance of diagnostic tests. For the clinical performance all pathogens were considered, whereas for analytical performance only microorganisms were considered for which primers are included in the PCR assay.

RESULTS

Among 51 patients, hardware-associated infection was diagnosed in 38 cases (75%) and non-infectious causes in 13 patients (25%). The sensitivity for diagnosing infection was 66% for peri-implant tissue culture, 84% for sonication fluid culture, 71% (clinical performance) and 77% (analytical performance) for sonication fluid PCR, the specificity of all tests was >90%. The analytical sensitivity of PCR was higher for gram-negative bacilli (100%), coagulase-negative staphylococci (89%) and Staphylococcus aureus (75%) than for Cutibacterium (formerly Propionibacterium) acnes (57%), enterococci (50%) and Candida spp. (25%).

CONCLUSION

The performance of sonication fluid PCR for diagnosis of orthopedic hardware-associated infection was comparable to culture tests. The additional advantage of PCR was short processing time (<5 h) and fully automated procedure. With further improvement of the performance, PCR has the potential to complement conventional cultures.

Results of cement spacer sonication in the second stage of two-stage treatment of shoulder arthroplasty infection

Background

The objective of this study is to present the results of cement spacer sonication in the second stage of two-stage treatment of shoulder arthroplasty infection and to determine the rate of positive cultures in the second-stage surgery in shoulder arthroplasty and its meaning.

Methods

Twenty-one patients (22 cement spacers) treated with two-stage surgery because of a shoulder arthroplasty infection were included. In the second stage, the cement spacer was sent for sonication and at least four tissue cultures were obtained. Epidemiological data, comorbidities, sensitivity of the microorganisms to the antibiotic loaded in the cement spacer in the first revision surgery, time elapsed since an antibiotic was last administered until second revision procedure, functional shoulder status at last follow-up, and any complication were recorded.

Results

Three out of the 22 cases (13.6%) presented positive cultures at the second-stage surgery. Periprosthetic tissue culturing detected the three positive culture cases in the second stage while the cement spacer sonication detected two and missed one. Considering periprosthetic tissue culturing as the standard procedure, the cement spacer sonication showed sensitivity at 66.6%. Recurrent infection over time was considered present in 3 patients; two of them had been previously diagnosed with a positive culture at the second stage (66.6%).

Conclusions

A good number of patients (13.6%) present a positive culture at the second stage of the two-stage surgical procedure for infected shoulder arthroplasty, and those patients seem to be at high risk for recurrent infection. Periprosthetic tissue cultures have a higher sensitivity to detecting a positive culture at the second stage than cement spacer sonication.

Diagnostic accuracy of synovial fluid, blood markers, and microbiological testing in chronic knee prosthetic infections

INTRODUCTION

This retrospective study was undertaken to define cut-off values for synovial fluid (SF) leukocyte count and neutrophil percentage for differentiating aseptic failure and periprosthetic joint infection (PJI) and to evaluate the diagnostic accuracy of blood inflammatory markers, and microbiological testing according to the criteria proposed by the International Consensus Meeting (ICM) of Philadelphia.

METHODS

All patients who underwent revision total knee arthroplasty from January 2010 to July 2015 were included: we identified and classified 31 PJIs and 136 aseptic joints. The diagnostic performance of single test was assessed by receiver operating characteristic curve analyses. The sensitivity and specificity were calculated for each of the cut-off values and the area under the curve (AUC) was calculated.

RESULTS

The median SF leukocyte count as well as the neutrophil percentage and inflammatory markers were significantly higher in patients with PJI than in those with aseptic failure (p < 0.001). A leukocyte count of > 2.8 × 10³/μL had a sensitivity of 83.8% and a specificity of 89.7% whereas a neutrophil percentage of > 72% yielded a marginally higher sensitivity of 84% and a specificity of 91%. Applying the ICM criteria we found a significant correlation between all these diagnostic measures and PJI (p < 0.001) except for a single positive culture. The most accurate criterion of the ICM was the synovial neutrophil differential (AUC = 0.89; 95% CI 0.81-0.97), followed by SF leukocyte count (AUC = 0.86; 95% CI 0.78-0.94), increased inflammatory markers (AUC = 0.85; 95% CI 0.76-0.93), and two positive periprosthetic cultures (AUC = 0.84; 95% CI 0.73-0.94). The presence of sinus tract communicating with the joint and a single positive culture showed unfavourable diagnostic accuracy (AUC = 0.60, 95% CI 0.47-0.72; AUC = 0.49, 95% CI 0.38-0.61, respectively) CONCLUSIONS: The present study highlights the adequate ability of fluid cell count and neutrophil differential to distinguish between PJI and aseptic loosening. The clinical utility of fluid analysis in diagnosing infection can be improved by evaluation of other diagnostic criteria.

LEVEL OF EVIDENCE

Level I Diagnostic Study.

C-reactive protein course during the first 5 days after total knee arthroplasty cannot predict early prosthetic joint infection

INTRODUCTION

Periprosthetic joint infection (PJI) is one of the most devastating major complications after total knee arthroplasty (TKA). The laboratory value C-reactive protein (CRP) is the inflammatory biomarker most suitable for detecting a potential postoperative (p.o.) early infection in orthopaedic surgery. However, on the basis of multiple receiver operating characteristic (ROC) analyses, CRP only has limited sensitivity and specificity. The objective of the present study was to test the hypothesis that, besides the absolute preoperative CRP value, also the absolute postoperative CRP value and its course over the first 5 days after TKA are valid indicators of periprosthetic early infection.

MATERIALS AND METHODS

A total of 1068 subjects who had been treated with a unilateral primary cemented total knee replacement due to primary osteoarthritis of the knee were included in the study. Retrospectively, for all patients, the preoperative CRP value, the p.o. CRP course and a history of the medical course, including any superficial surgical site infection (SSI) or deep PJI of the knee joint operated on, were recorded; further, any follow-up operations (septic revision) were documented. Using receiver operating characteristic (ROC) analysis, an optimum preoperative CRP cutoff value for the positive prediction of a PJI was determined.

RESULTS

34 of 1068 patients developed an SSI or a PJI that had to be revised. After TKA implantation, the CRP value increased significantly and achieved its maximum between the second and third p.o. day. At no p.o. day was there a difference in CRP between patients who developed an SSI or a deep PJI and patients with a normal complication-free p.o.

COURSE

In contrast, the preoperative CRP value proved to be a reliable predictor for septic revision due to an SSI or a PJI: the ROC analysis showed the optimum preoperative CRP cutoff value for a positive prediction of PJI to be 5 mg/L.

CONCLUSION

The most important finding of the present study is that neither the absolute p.o. CRP value nor its course in the first 5 days after TKA is suitable for detecting an early infection. In contrast, an increased preoperative CRP value proved to be a valid predictor for septic revision due to an SSI or a PJI after TKA.

Polymicrobial and Monomicrobial Infections after Spinal Surgery: A Retrospective Study to Determine which Infection is more Severe

Study Design

A retrospective clinical review.

Purpose

To investigate the difference in clinical manifestations and severity between polymicrobial and monomicrobial infections after spinal surgery.

Overview of Literature

Surgical site infections (SSIs) after spinal surgery are a major diagnostic and therapeutic challenge for spinal surgeons. Polymicrobial infections after spinal surgery seem to result in poorer outcomes than monomicrobial infections because of complementary resistance to antibiotics. However, comparison of the clinical manifestations and severity between polymicrobial and monomicrobial infections are limited.

Methods

Sixty-seven patients with SSIs after spinal surgery were studied: 20 patients with polymicrobial infections and 47 with monomicrobial infections. Pathogenic bacteria identified were counted and classified. Age, sex, and body mass index were compared between the two groups to identify homogeneity. The groups were compared for clinical manifestations by surgical site, postoperative time to infection, infection site, incisional drainage, incisional swelling, incisional pain, neurological signs, temperature, white blood cell count, and the percentage of neutrophils. Finally, the groups were compared for severity by hospital stay, number of rehospitalizations, number of debridements, duration of antibiotics administration, number of antibiotics administered, and implant removal.

Results

Polymicrobial infections comprised 29.9% of SSIs after spinal surgery, and most polymicrobial infections (70.0%) were caused by two species of bacteria only. There was no difference between the groups in terms of clinical manifestations and severity. In total, 96 bacterial strains were isolated from the spinal wounds: 60 strains were gram-positive and 36 were gram-negative pathogenic bacteria. Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Enterobacter cloacae were cultured in order of the frequency of appearance.

Conclusions

Most polymicrobial infections were caused by two bacterial species after spinal surgery. There was no difference in clinical manifestations or severity between polymicrobial and monomicrobial infections.

Low sensitivity of implant sonication when screening for infection in revision surgery

Background and purpose - Prosthetic-joint infection (PJI) is the most serious complication of arthroplasty, and accurate identification of a potentially responsible microorganism is essential for successful antibiotic treatment. We therefore determined the diagnostic accuracy of sonication and compared it with tissue culture as a screening tool in detecting prosthetic joint infection in revision arthroplasty. Patients and methods - 252 consecutive revision arthroplasty cases were enrolled. These cases were determined as being suspected or unsuspected of having infection according to standard criteria. Perioperatively, 6 periprosthetic interface tissue biopsies were obtained from each patient and the implants removed were sonicated. The sensitivity and specificity of periprosthetic tissue culture and sonication fluid cultures were determined. Results - Preoperatively, 75 revision cases were classified as having PJI (33 early and 42 late) and 177 were unsuspected of having infection. Compared with tissue culture, the sensitivity of the sonication fluid analysis was low: 0.47 (95% CI: 0.35-0.59) for sonication as compared to 0.68 (95% CI: 0.56-0.78) for tissue culture. The specificity of the sonication fluid analysis was higher than that for tissue culture: 0.99 (95% CI: 0.96-1.0) as compared to 0.80 (95% CI: 0.74-0.86). Interpretation - Sonication is a highly specific test for diagnosis of PJI. However, due to the low sensitivity, a negative sonication result does not rule out the presence of PJI. Thus, sonication is not of value for screening of microorganisms during revision surgery.

[Joint infections of the hand]

Joint infections of the hand may lead to irreversible lesions and impairment of hand function due to early cartilage damage. Furthermore, persistent infections which are not treated immediately can cause osteitis and/or spread systemically. Finger joints are prone to infection due to bite wounds or crush and sharp injuries. Whereas the wrist is often affected in patients with immunosuppression or chronic diseases, such as diabetes mellitus. If diagnosis and therapy are delayed, joint damage may be inevitable. Therefore, urgent treatment of the infected joint is imperative to preserve the function of the hand. This article reviews the current diagnostics and treatment of joint infections of the hand.

Outcome following subluxation of mobile articulating spacers in two-stage revision total knee arthroplasty

INTRODUCTION

Infection after total knee arthroplasty (TKA) is a severe complication. It is usually treated with two-stage revision and implantation of a cement spacer. Few studies describe the complications associated with a mobile articulating spacer. This study examined the subluxation of articulating antibiotic spacers in knees and correlated it with prospectively collected early outcome scores after implantation of a revision prosthesis.

METHODS

Staged revisions for 72 infected primary total knee arthroplasties between 2004 and 2012 were examined. The mean age of the patients was 70.2 ± 10.8 years, with 40 right and 32 left knees. Sagittal and coronal subluxation was measured using radiographs prior to second-stage revision and grouped to be within (Group 1) or outside (Group 2) one standard deviation from the mean. Medical Outcomes Study Short Form-12 (SF-12), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Knee Society Score (KSS) were obtained via patient-administered questionnaire. Statistical analysis was carried out to look at the correlation between subluxation and outcome.

RESULTS

Significant improvements were observed between the interim outcome scores prior to implantation of a revision prosthesis and scores obtained after second-stage revision. Debonding occurred in 5.6%, and one dislocation was found. Mean coronal subluxation was 4.8 ± 5.5% of the tibia width, in the lateral direction. Coronal subluxation did not affect SF12, WOMAC or KSS outcome scores. Mean sagittal subluxation was 6.1 ± 16.4% posteriorly. However, sagittal subluxation had a significant influence on Knee Society Scores, with Group 2 having a lower mean Knee Society Function Score of 39.3 than Group 1 (60.2) (p = 0.045). Sagittal subluxation did not affect SF12 or WOMAC scores.

CONCLUSION

Sagittal subluxation of the knee may influence the early to midterm outcome scores following a staged revision TKA for infection.

The value of arthroscopic neosynovium biopsies to diagnose periprosthetic knee joint low-grade infection

INTRODUCTION

The diagnostic algorithm in cases of assumed low-grade infection after total knee arthroplasty is discussed controversial. The aim of this study was to evaluate the reliability of neosynovium biopsies via knee arthroscopies in predicting a periprosthetic knee joint infection (PJI).

METHODS

From 2010 to 2015, 56 consecutive patients received a diagnostic arthroscopy of the knee joint by reason of an assumed PJI. In 34 cases, a revision arthroplasty was performed after the diagnostic arthroscopy. The microbiologic and histologic results from neosynovium biopsies were compared to intraoperative findings of the consecutively performed revision arthroplasty.

RESULTS

The arthroscopic neosynovium biopsies had a sensitivity of 0.88 (0.47-1.0 95 % confidence interval), a specificity of 0.88 (0.7-0.98), a positive predictive value of 0.7 (0.35-0.93), and a negative predictive value of 0.96 (0.79-1.0). The accuracy was 0.88. We determined a higher sensitivity of neosynovium biopsies compared to C-reactive protein (p = 0.038) and white blood cell count (p < 0.001) in serum. The itemized evaluation of histologic results showed a significant higher sensitivity compared to microbiologic results (p = 0.045) and a higher accuracy.

CONCLUSIONS

The analysis of arthroscopic neosynovium biopsies can be helpful to verify or exclude a PJI in selected patients. Especially, histologic assessment showed a high accordance with final results. Level of evidence IV, retrospective study.

Knee salvage in revision arthroplasty after massive bone loss of the femur condyles (≥Engh III) with a single-modular-hinged knee revision implant

PURPOSE

Massive bone loss of the femur condyles in revision arthroplasty often requires modular-hinged revision implants to restore a stable joint situation. In the present series, the outcome after knee revision surgery using a single modular-hinged revision implant in patients with severe bone defects (>Engh III) is investigated.

METHODS

Sixty patients with severe bone defects (≥Engh III) after failed primary and revision knee arthroplasty were included. Medium follow-up was 47 (range 10-84) months after knee revision surgery. Medium patient age was 70 (range 33-87) years at the time of surgery. An average of 2.3 prior knee operations per patient was performed. 70 % of the patients required the knee revision implant after two-stage revision because of a deep implant infection.

RESULTS

Estimated 5 year extremity survival was 95 and 65 % implant survival. Reasons for implant revision in decreasing order were reinfection (30 %), aseptic loosening (13 %), and periprosthetic fracture (9.8 %). The average active range of motion in the knee joint was 88° (range 40°-115°) for flexion. An extension deficit of a mean of -6° was (range -50-5° hyper-extension) observed. Patient age influenced the functional results significantly in terms of reduced walking distances and decreased modified WOMAC score.

CONCLUSION

In consideration of this complex study, population acceptable functional results can be achieved using a modular knee revision endoprosthesis. In younger patients (<60 years), satisfying results in terms of walking ability and overall satisfactory can be expected. The outcome in older multimorbid patients is worse. Yet, operation in these patients can be feasible to restore enough mobility for daily household activities.

Ertapenem Articulating Spacer for the Treatment of Polymicrobial Total Knee Arthroplasty Infection

Introduction. Periprosthetic joint infections (PJIs) are the primary cause of early failure of the total knee arthroplasty (TKA). Polymicrobial TKA infections are often associated with a higher risk of treatment failure. The aim of the study was to assess the efficacy of ertapenem loaded spacers in the treatment of polymicrobial PJI. Methods. There were 18 patients enrolled; nine patients with polymicrobial PJI treated with ertapenem loaded articulating spacers were compared to the group of 9 patients treated with vancomycin or ceftazidime loaded spacers. Results. Successful reimplantation with revision implants was possible in 66.67%. Ertapenem spacers were used in 6 cases in primary two-stage procedure and in 3 cases in secondary spacer exchange. Successful infection eradication was achieved in all cases; final reimplantation with revision knee arthroplasty implants was possible in 6 cases. Conclusion. Ertapenem can be successfully used as antimicrobial addition to the cement spacers in two-stage revision treatment of polymicrobial PJIs. However, this type of spacer may also be useful in the treatment of infections caused by monomicrobial extended spectrum beta-lactamases producing gram-negative bacilli. Further clinical studies are required to evaluate the efficacy and safety of ertapenem spacers in the treatment of polymicrobial and monomicrobial PJIs.

Two-stage revision arthroplasty for periprosthetic joint infections: What is the value of cultures and white cell count in synovial fluid and CRP in serum before second stage reimplantation?

INTRODUCTION

Besides CRP in serum, white cell counts and cultures of synovial fluid are routinely used to detect periprosthetic joint infections. But the sensitivities of these parameters do vary from 12 to 100 %. In two stage revision arthroplasty before the second stage surgeons have to decide if reimplantation is justified. Therefore, we investigated the value of cultures and white cell count from the synovial fluid with a polymethyl methacrylate spacer in place and CRP in serum before reimplantation to detect persistent infection in a standardized setting.

METHODS

115 patients with a two-stage revision hip or knee arthroplasty were included in this study. All patients had an antibiotic loaded polymethylmethacrylate spacer. Retrospectively synovial cultures, white blood count in synovial fluid and CRP in serum were assessed before reimplantation.

RESULTS

The sensitivity of the synovial cultures was 5 % (95 % CI 0.13-24.87), with a specificity of 99 % (95 % CI 94.27-99.97). For white blood count in synovial fluid the sensitivity was 31.3 %, specificity was 39.1 %. Sensitivity for CRP in serum was 42.10 %, specificity was 84.21 %.

CONCLUSION

Cultures from synovial fluid and white blood count in synovial fluid and CRP seem to be uncertain parameters to exclude persistent infection. We do not recommend joint aspiration before reimplantation anymore. Further research is necessary to find other markers to confirm or exclude persistent infection.

Microbiological Diagnosis of Implant-Related Infections: Scientific Evidence and Cost/Benefit Analysis of Routine Antibiofilm Processing

Prosthetic joint infection is one of the most severe complication following joint arthroplasty, producing a significant worsening of patient's quality of life. Management of PJIs requires extended courses of antimicrobial therapy, multiple surgical interventions and prolonged hospital stay, with a consequent economic burden, which is thought to markedly increase in the next years due to the expected burden in total joint arthroplasties. The present review summarizes the present knowledge on microbiological diagnosis of prosthetic joint infections, focusing on aethiological agents and discussing pros and cons of the available strategies for their diagnosis.Intra-operative clinical diagnosis and pathogen identification is considered the diagnostic benchmark, however the presence of bacterial biofilm makes pathogen detection with traditional microbiological techniques highly ineffective. Diagnosis of PJIs is a rather complex challenge for orthopedics and requires a strict collaboration between different specialists: orthopaedics, infectivologists, microbiologists, pathologists and radiologists. Diagnostic criteria have been described by national and international association and scientific societies. Clinicians should be trained on how to use it, but more importantly they should know potential and limitation of the available tests in order to use them appropriately.