Sonication of orthopaedic implants: A valuable technique for diagnosis of prosthetic joint infections

Evaluation of the use of sonication combined with enzymatic treatment for biofilm removal in the microbiological diagnosis of prosthetic joint infection

Sonicating explanted prosthetic implants to physically remove biofilms is a recognized method for improving the microbiological diagnosis of prosthetic joint infection (PJI); however, chemical and enzymatic treatments have been investigated as alternative biofilm removal methods. We compared the biofilm dislodging efficacy of sonication followed by the addition of enzyme cocktails with different activity spectra in the diagnosis of PJI with that of the sonication of fluid cultures alone. Consecutive patients who underwent prosthesis explantation due to infection at our institution were prospectively enrolled for 1 year. The diagnostic procedure included the collection of five intraoperative tissue cultures, sonication of the removed devices, and conventional culture of the sonication fluid. The resulting sonication fluid was also treated with an enzyme cocktail consisting of homemade dispersin B (0.04 µg/mL) and proteinase K (Sigma; 100 µg/mL) for 45 minutes at 37°C. The resulting sonication (S) and sonication with subsequent enzymatic treatment (SE) fluids were plated for aerobic and anaerobic culture broth for 7 days (aerobic) or 14 days (anaerobic). Identification was performed by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (Bruker). We included 107 patients from whom a prosthetic implant had been removed, among which PJI was diagnosed in 36 (34%). The sensitivity of S alone was significantly greater than that of SE alone (82% vs 71%; P < 0.05). Four patients with PJI were positive after sonication alone but negative after sonication plus enzymatic treatment. The four microorganisms missed after the addition of the enzyme cocktail were Staphylococcus aureus, two coagulase-negative Staphylococci, and Cutibacterium acnes. In conclusion, sonication alone was more sensitive than sonication followed by enzymatic treatment. The combination of these two methods had no synergistic effect; in contrast, the results suggest that the combination of both dislodgment methods affects the viability of gram-positive microorganisms.

IMPORTANCE

While the potential of sonication and enzymes as biofilm dispersal agents has been previously described, the originality of our work resides in the combination of both methods, which is hypothesized to enhance the ability to remove biofilm and, therefore, improve the microbiological diagnosis of PJI.

Sonication in Patients With Spinal Cord Stimulation: A New Approach for Infection Diagnostics

INTRODUCTION

Spinal cord stimulation (SCS) offers improvement in pain and function for several chronic pain conditions. There are concerns regarding bacterial colonization of the temporary lead extensions and subsequent infection risk in a two-session implantation procedure. Although there is no standardized evaluation of SCS lead contamination, this study evaluates the infection rate and microbial colonization of SCS lead extensions with sonication, a method that is established in implant-related infection diagnostics.

MATERIALS AND METHODS

This prospective observational study comprised 32 patients with a two-stage SCS implantation procedure. Microbial colonization of the lead extensions was assessed with sonication. The presence of organisms in the subcutaneous tissue was evaluated separately. Surgical-site infections were recorded. Patient demographics and risk factors including diabetes, tobacco use, obesity, trial length, and infection parameters in serum were recorded and analyzed.

RESULTS

The mean age of the patients was 55 years. On average, the trial length was 13 days. In seven cases (21.9%), a microbial lead colonization was found with sonication. In contrast, there was one positive culture (3.1%) from the subcutaneous tissue samples. The C-reactive protein and leukocyte count remained at the preoperative level. One early surgical-site infection (3.1%) occurred. No other late infections occurred six months after surgery.

CONCLUSIONS

There is a discrepancy between the presence of microbial colonization and the occurrence of clinically relevant infections. Although the rate of microbial colonization of the lead extensions is high (21.9%), the surgical-site infection rate remained low (3.1%). Therefore, we can conclude that the two-session procedure is a safe approach that is not associated with a higher incidence of infection. Although the sonication method cannot be used as the sole tool for detecting infections in patients with SCS, it can provide additional value in microbial diagnostics in combination with clinical and laboratory parameters and conventional microbiological methods.

Nanoparticle ultrasonication outperforms conventional irrigation solutions in eradicating Staphylococcus aureus biofilm from titanium surfaces: an in vitro study

PURPOSE

Bacterial biofilms create a challenge in the treatment of prosthetic joint infection (PJI), and failure to eradicate biofilms is often implicated in the high rates of recurrence. In this study, we aimed to compare the effectiveness of a novel nanoparticle ultrasonication technology on Staphylococcus aureus biofilm eradication compared to commonly used orthopedic irrigation solutions.

METHODS

Twenty-four sterile, titanium alloy discs were inoculated with a standardized concentration of methicillin-resistant S. aureus and cultured for seven days to allow for biofilm formation. Discs were then treated with either ultrasonicated nanoparticle therapy or irrigation with chlorhexidine gluconate, povidone-iodine or normal saline. The remaining bacteria on each surface was subsequently plated for colony-forming units of S. aureus. Bacterial eradication was reported as a decrease in CFUs relative to the control group. Mann-Whitney U tests were used to compare between groups.

RESULTS

Treatment with ultrasonicated nanoparticles resulted in a significant mean decrease in CFUs of 99.3% compared to controls (p < 0.0001). Irrigation with povidone-iodine also resulted in a significant 77.5% reduction in CFUs compared to controls (p < 0.0001). Comparisons between ultrasonicated nanoparticles and povidone-iodine demonstrated a significantly higher reduction in bacterial CFUs in the nanoparticle group (p < 0.0001).

CONCLUSION

Ultrasonicated nanoparticle were superior to commonly used bactericidal irrigation solutions in the eradication of S. aureus from a titanium surface. Future clinical studies are warranted to evaluate this ultrsonication technology in the treatment of PJI.

Modern Microbiological Methods to Detect Biofilm Formation in Orthopedy and Suggestions for Antibiotic Therapy, with Particular Emphasis on Prosthetic Joint Infection (PJI)

Biofilm formation is a serious problem that relatively often causes complications in orthopedic surgery. Biofilm-forming pathogens invade implanted foreign bodies and surrounding tissues. Such a condition, if not limited at the appropriate time, often requires reoperation. This can be partially prevented by selecting an appropriate prosthesis material that prevents the development of biofilm. There are many modern techniques available to detect the formed biofilm. By applying them we can identify and visualize biofilm-forming microorganisms. The most common etiological factors associated with biofilms in orthopedics are: Staphylococcus aureus, coagulase-negative Staphylococci (CoNS), and Enterococcus spp., whereas Gram-negative bacilli and Candida spp. also deserve attention. It seems crucial, for therapeutic success, to eradicate the microorganisms able to form biofilm after the implantation of endoprostheses. Planning the effective targeted antimicrobial treatment of postoperative infections requires accurate identification of the microorganism responsible for the complications of the procedure. The modern microbiological testing techniques described in this article show the diagnostic options that can be followed to enable the implementation of effective treatment.

Optimal ultrasonic treatment frequency and duration parameters were used to detect the pathogenic bacteria of orthopedic implant-associated infection by ultrasonic oscillation

INTRUDUCTON

The most accurate method for detecting the pathogen of orthopedic implant-associated infections (OIAIs) is sonication fluid (SF). However, the frequency and duration of ultrasound significantly influence the number and activity of microorganisms. Currently, there is no consensus on the selection of these two parameters. Through this study, the choice of these two parameters is clarified.

METHODS

We established five ultrasonic groups (40kHz/10min, 40kHz/5min, 40 kHz/1min, 20kHz/5min, and 10kHz/5min) based on previous literature. OIAIs models were then developed and applied to ultrasound group treatment. Subsequently, we evaluated the efficiency of bacteria removal by conducting SEM and crystal violet staining. The number of live bacteria in the SF was determined using plate colony count and live/dead bacteria staining.

RESULTS

The results of crystal violet staining revealed that both the 40kHz/5min group and the 40kHz/10min group exhibited a significantly higher bacterial clearance rate compared to the other groups. However, there was no significant difference between the two groups. Additionally, the results of plate colony count and fluorescence staining of live and dead bacteria indicated that the number of live bacteria in the 40kHz/5min SF group was significantly higher than in the other groups.

CONCLUSION

40kHz/5min ultrasound is the most beneficial for the detection of pathogenic bacteria on the surface of orthopedic implants.

Fracture related infection in open tibial fractures

Open tibia fractures frequently occur following high-energy trauma. Contamination of the fracture site combined with limited soft tissue coverage and blood supply means that these open fractures are associated with a high rate of complications, including fracture related infection (FRI). FRI is associated with lowered patient outcomes and requires early recognition and appropriate surgical and medical management. The current evidence on FRI after open tibial fractures largely is limited to case series, small retrospective cohort studies and expert opinion. Recent expert consensus has produced guidelines with the aim of standardising care for these patients. This review summarises the current management strategies employed in treating FRI following open tibial fractures and where possible the evidence behind them.

Fracture-related infections

Fracture-related infection is a serious complication which can occur following musculoskeletal injury and is associated with significant morbidity. These complications can be challenging to recognise, and experts have provided a clearer definition of fracture-related infection to help with the diagnosis and detection of these infections. This system includes clinical, radiological and laboratory-based diagnostic features which are either confirmatory or suggestive of fracture-related infection. Treatment requires a multifaceted approach with multidisciplinary involvement, and generally a combination of surgical techniques and prolonged antibiotics, the timing and choice of which should be optimised. This article provides an evidence-based review of the British Orthopaedic Association Standards for Trauma for the diagnosis and management of fracture-related infections.

Direct detection and identification of periprosthetic joint infection pathogens by metagenomic next-generation sequencing

This study assessed the application of metagenomic next-generation sequencing in pathogen detection of periprosthetic joint infections. A total of 95 cases who previously had undergone hip and knee replacement undergoing revision from January 2018 to January 2021 were included in this study. Specimens of synovial fluid and deep-tissue were collected for culture and metagenomic next-generation sequencing, and patients were retrospectively categorized as infected or aseptic using the Musculoskeletal Infection Society criteria after revision surgery. The sensitivity, specificity, positive and negative predictive values were compared. A total of 36 cases had positive culture results and 59 cases had positive metagenomic next-generation sequencing results. Culture was positive in 34 infected cases (58.6%) and 2 aseptic cases (5.4%). Metagenomic next-generation sequencing was positive in 55 infected cases (94.8%) and 4 aseptic cases (10.8%). Five cases diagnosed with infection had other potential pathogens detected by metagenomic next-generation sequencing. Among the 24 culture-negative periprosthetic joint infections, metagenomic next-generation sequencing was able to identify potential pathogens in 21 cases (87.5%). From sampling to reporting, the average time needed for culture was 5.2 (95% CI 3.1-7.3) days, while that for metagenomic next-generation sequencing was 1.3 (95% CI 0.9-1.7) days. Metagenomic next-generation sequencing is more advantageous in pathogen detection of periprosthetic joint infection after total joint replacement, especially in patients with multiple infections or negative culture results.

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.

Induction of Viable but Non-Culturable State in Clinically Relevant Staphylococci and Their Detection with Bacteriophage K

Prosthetic joint infections are frequently associated with biofilm formation and the presence of viable but non-culturable (VBNC) bacteria. Conventional sample culturing remains the gold standard for microbiological diagnosis. However, VBNC bacteria lack the ability to grow on routine culture medium, leading to culture-negative results. Bacteriophages are viruses that specifically recognize and infect bacteria. In this study, we wanted to determine if bacteriophages could be used to detect VBNC bacteria. Four staphylococcal strains were cultured for biofilm formation and transferred to low-nutrient media with different gentamycin concentrations for VBNC state induction. VBNC bacteria were confirmed with the BacLight^TM viability kit staining. Suspensions of live, dead, and VBNC bacteria were incubated with bacteriophage K and assessed in a qPCR for their detection. The VBNC state was successfully induced 8 to 19 days after incubation under stressful conditions. In total, 6.1 to 23.9% of bacteria were confirmed alive while not growing on conventional culturing media. During the qPCR assay, live bacterial suspensions showed a substantial increase in phage DNA. No detection was observed in dead bacteria or phage non-susceptible E. coli suspensions. However, a reduction in phage DNA in VBNC bacterial suspensions was observed, which confirmed the detection was successful based on the adsorption of phages.

Reliable Diagnostic Tests and Thresholds for Preoperative Diagnosis of Non-Inflammatory Arthritis Periprosthetic Joint Infection: A Meta-analysis and Systematic Review

Objective

The current diagnostic criteria for periprosthetic joint infection (PJI) are diverse and controversial, leading to delayed diagnosis. This study aimed to evaluate and unify their diagnostic accuracy and the threshold selection of serum and synovial routine tests for PJI at an early stage.

Methods

We searched the MEDLINE and Embase databases for retrospective or prospective studies which reported preoperative‐available assays (serum, synovial, or culture tests) for the diagnosis of chronic PJI among inflammatory arthritis (IA) or non‐IA populations from January 1, 2000 to June 30, 2022. Threshold effective analysis was performed on synovial polymorphonuclear neutrophils (PMN%), synovial white blood cell (WBC), serum C‐reactive protein (CRP), and erythrocyte sedimentation rate (ESR) to find the relevant cut‐offs.

Results

Two hundred and sixteen studies and information from 45,316 individuals were included in the final analysis. Synovial laboratory‐based α‐defensin and calprotectin had the best comprehensive sensitivity (0.91 [0.86–0.94], 0.95 [0.88–0.98]) and specificity (0.96 [0.94‐0.97], 0.95 [0.89–0.98]) values. According to the threshold effect analysis, the recommended cut‐offs are 70% (sensitivity 0.89 [0.85–0.92], specificity 0.90 [0.87–0.93]), 4100/μL (sensitivity 0.90 [0.87–0.93], specificity 0.97 [0.93–0.98]), 13.5 mg/L (sensitivity 0.84 [0.78–0.89], specificity 0.83 [0.73–0.89]), and 30 mm/h (sensitivity 0.79 [0.74–0.83], specificity 0.78 [0.72–0.83]) for synovial PMN%, synovial WBC, serum CRP, and ESR, respectively, and tests seem to be more reliable among non‐IA patients.

Conclusions

The laboratory‐based synovial α‐defensin and synovial calprotectin are the two best independent preoperative diagnostic tests for PJI. A cut off of 70% for synovial PMN% and tighter cut‐offs for synovial WBC and serum CRP could have a better diagnostic accuracy for non‐IA patients with chronic PJI.

Sonication of revised hip and knee prostheses detects occult infections, improves clinical outcomes and prevents re - revisions. A case series study

Introduction

Periprosthetic joint infection (PJI) is a devastating complication occurring in 1–2% of primary and up to 10% of revised total hip and knee arthroplasties (THA and TKA) impairing patient's quality of life. Occult infections are underdiagnosed, sub-treated and sub-clinically experienced by patients. This study aimed to correlate patients' clinical outcomes with early antibiotic treatment based on use or non-use of a sonication technique on explanted prostheses.

Methods

33 patients with revised THA or TKA were retrospectively evaluated. Clinical outcomes were assessed via Oxford hip or knee scores, and correlated with administration or not of antibiotic treatment based on sonication results.

Results

According to laboratory findings the patients were divided in the following three groups: 1. Septic loosening (conventional cultures and/or sonication positive), 2. Aseptic loosening (conventional cultures and sonication negative) and 3. Occult loosening (conventional cultures negative, sonication not performed). The average Oxford score was poor (27.9/60) for the septic, excellent (43.8/60) for the aseptic and intermediate (37.7/60) for the occult group. Additionally, conventional cultures were negative, but sonication-positive, in 6 individuals with patient-related risk factors (male gender, BMI > 30 kg/m², diabetes, hypertension, steroids and rheumatoid arthritis).

Conclusions

Sonication represents a valuable diagnostic technique to guide administration of effective antibiotic treatment for patients, especially for detection of persistent post-revision occult infections. We recommend the systematic investigation of revised prostheses with a sonication technique, but especially in cases with risk factors for infection who it is suspected may have occult loosening.

Diagnosing Periprosthetic Joint Infection: a Scoping Review

PURPOSE OF REVIEW

The goal of this review is to provide an up to date understanding of the utility and limitations of the current tests utilized in the diagnosis of periprosthetic joint infection (PJI) in total knee and hip arthroplasty.

RECENT FINDINGS

Despite the growth in literature surrounding PJI diagnosis, there remains challenges in establishing a diagnosis of PJI. A combination of clinical, serum, and synovial tests and microbiologic and histologic examinations can yield a diagnosis in the majority of cases. Novel molecular and imaging studies may be beneficial for indeterminant cases. A number of emerging diagnostic tests have been proposed and may be incorporated into diagnostic algorithms in the future. Recently proposed stepwise diagnostic algorithms have shown high sensitivity and specificity. The diagnosis of PJI remains challenging due to a lack of tests that can definitively rule out infection. Diagnosis and investigations should occur in a stepwise fashion. There has been a plethora of new diagnostic tests introduced in attempts to improve the accuracy of diagnostic algorithms. The definition and algorithms for the diagnoses of PJI will continue to evolve as new techniques and tests are introduced.

Different microbial and resistance patterns in primary total knee arthroplasty infections - a report on 283 patients from Lithuania and Sweden

Background

The microbiology and the susceptibility patterns of infected total knee arthroplasties (TKAs) vary depending on demographic, local antimicrobial stewardship, and surgical factors. We wanted to compare the recent microbial profile and antimicrobial resistance pattern in revisions due to infections after primary TKAs in Sweden and Lithuania. Our hypothesis was that there is a difference in bacteriology and resistance pattern based on patient related, societal and local hospital factors as almost similar praxis have been applied for TKA surgery, short term systemic prophylaxis and routine use of local gentamicin containing bone cement.

Methods

Primary TKAs revised for the first time due to verified or suspected infection were collected nationwide in Sweden during 2018, and in Lithuania between 2011 and 2020 from a single major TKA revision centre in Kaunas. We identified 202 TKAs in Sweden from the Swedish Knee Arthroplasty Register and 84 from Kaunas revised due to infection. We collected available culture reports and evaluated the type of microorganisms with antimicrobial resistance pattern at revision.

Results

The majority of the infected cases in Sweden were early-type prosthetic joint infection (PJI) (44%), whereas late-type PJI (52%) were more common in the Kaunas cases. Gram-positive bacteria prevailed in both Sweden (55%) and Lithuania (80%). Staphylococcus aureus was the most frequent organism identified in both countries (33% in Sweden and 34% in Lithuania). More polymicrobial infections were observed in Sweden than in Lithuania (16 and 6% respectively). Methicillin resistance in Staphylococcus aureus and coagulase-negative staphylococci were higher in Lithuania (4/28 and 19/29) than in Sweden (1/42 and 9/41).

Conclusions

The type of infections, microbial profile, and drug resistance pattern differed between Sweden and Lithuania. Societal and local hospitals factors with emerging resistance in Lithuania are the most plausible explanation for the difference. Lack of complete data on a national level in Lithuania underlines the importance of adding microbiology of PJIs in implant registers for national aggregation and allow cross country comparisons.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04689-5.

Explaining Osteomyelitis and Prosthetic Joint Infections (PJI) in terms of Biofilm - A Review

Osteomyelitis is a chronic infection of bones. Eradication of bone infection is usually with antibiotics and debridement, but it is slow and the infection can recur even after many years. It is now established that osteomyelitis is due to biofilm and a better understanding of the process is required. We review the development of biofilm and apply it to osteomyelitis management. The planktonic microbes' response to adverse conditions is the formation of biofilm. Bacterial infections in planktonic forms cause infections that can be controlled with antibiotics and immunisation, however the same microbe when its phenotype becomes biofilm is more resilient. The understanding of how planktonic bacteria convert to biofilm is one of the aims set out for this article.

Sonication improves microbiologic diagnosis of periprosthetic elbow infection

BACKGROUND

Periprosthetic joint infection (PJI) is a relatively frequent and oftentimes devastating complication after total elbow arthroplasty (TEA). Its microbiologic diagnosis is usually based on periprosthetic tissue culture (hereafter referred to as tissue culture), but the sensitivity of tissue culture is variable. Although implant sonication culture has been shown to be superior to tissue culture for the diagnosis of hip and knee PJI, only a single small study (of fewer than 10 infected implants) has assessed sonication for PJI diagnosis after elbow arthroplasty.

METHODS

We retrospectively analyzed 112 sonicate fluid cultures from patients who underwent revision of a TEA at a single institution between 2007 and 2019, comparing results to those of tissue cultures. We excluded patients who had fewer than 2 tissues submitted for culture. Using the Infectious Diseases Society of America guidelines to define PJI, there were 49 infected and 63 non-infected cases. Median ages in the PJI and non-infected groups were 66 and 61 years, respectively. In the non-infected group, 65% were female vs. 63% in the PJI group. We reviewed clinical characteristics and calculated the sensitivity and specificity of tissue compared with sonicate fluid culture. In addition, we compared the sensitivity of tissue culture to the combination of tissue and sonicate fluid culture.

RESULTS

The most common pathogens were coagulase-negative Staphylococcus sp (49%), followed by Staphylococcus aureus (12%). Sensitivity of tissue culture was 63%, and sensitivity of sonicate fluid culture was 76% (P = .109). Specificity of tissue culture was 94% and specificity of sonicate fluid culture was 100%. Sensitivity of sonicate fluid culture in combination with tissue culture was 84% (P = .002 compared to tissue culture alone).

CONCLUSION

In this study, we found that the combination of sonicate fluid and tissue culture had a greater sensitivity than tissue culture alone for microbiologic diagnosis of PJI after TEA.

Targeted next generation sequencing for elbow periprosthetic joint infection diagnosis

16S ribosomal RNA (rRNA) gene PCR followed by next-generation sequencing (NGS) was compared to culture of sonicate fluid derived from total elbow arthroplasty for periprosthetic joint infection (PJI) diagnosis. Sonicate fluids collected from 2007 to 2019 from patients who underwent revision of a total elbow arthroplasty were retrospectively analyzed at a single institution. PCR amplification of the V1-V3 region of the 16S rRNA gene was performed, followed by NGS using an Illumina MiSeq. Results were compared to those of sonicate fluid culture using McNemar's test of paired proportions. Forty-seven periprosthetic joint infections and 58 non-infectious arthroplasty failures were studied. Sensitivity of targeted NGS was 85%, compared to 77% for culture (P = 0.045). Specificity and positive and negative predictive values of targeted NGS were 98, 98 and 89%, respectively, compared to 100, 100 and 84%, respectively, for culture. 16S rRNA gene-based targeted metagenomic analysis of sonicate fluid was more sensitive than culture.

Accuracy of Tissue and Sonication Fluid Sampling for the Diagnosis of Fracture-Related Infection: Diagnostic Meta-Analysis

Evidence shows that tissue sample culturing is the gold standard approach for diagnosing fracture-related infection (FRI). Sonication fluid sampling has also been reported to be efficacious and superior to tissue sample culturing with prosthetic joint infection. However, data from the current literature are not enough to validate this hypothesis for FRI. We conducted a meta-analysis to validate the diagnostic accuracy of tissue sample culturing and sonication fluid aspiration and to find which one is superior to the other. An extensive search through the relevant databases was conducted to obtain all the relevant studies. We have included 13 relevant studies, including nine retrospective cohorts and four prospective ones. The overall pooled estimates of sensitivity, specificity, and diagnostic odds ratio (DOR) of tissue sampling culture in diagnosing fracture-related infections were 98% (95% CI, 92% to 99%), 38% (95% CI, 23% to 56%), and 25 (4 to 154), respectively. The overall pooled estimates of sensitivity, specificity, and DOR of sonication fluid sample culture in diagnosing fracture-related infections were 86% (95% CI, 79% to 92%), 98% (95% CI, 93% to 100%), and 353 (78 to 1598), respectively. No significant risk of bias was found regarding the sensitivity and specificity among studies investigating both modalities, however, significant heterogeneity was noticed. Sonication fluid sampling can be used to confirm FRI while tissue sampling can be used to exclude it and both modalities should be combined for obtaining the most accurate outcome.

The utility of dithiothreitol treatment of periprosthetic tissues and explanted implants in the diagnosis of prosthetic joint infection

PURPOSE

The methods used for the processing of periprosthetic tissues and explanted implants to improve culture outcome especially in biofilm mediated prosthetic joint infections (PJIs) are still debated upon. Studies have reported that Dithiothreitol (DTT) pretreatment of infected devices gives similar results as sonication. However, none of them evaluated the DTT treatment of periprosthetic tissues and explanted implants in the same cohort. We evaluated the diagnostic utility of DTT treatment of periprosthetic tissue and explanted implants, as compared to the normal saline treatment of periprosthetic tissues and sonication of explanted implants for the diagnosis of PJI.

METHODS

Seventy-three revision arthroplasty cases were prospectively included in this study. Three to five tissue specimens and the explanted implants were collected from each patient. Periprosthetic tissue samples were processed by both normal saline and DTT treatments. Explanted implants were subjected to both DTT treatment and sonication. Musculoskeletal Infection Society (MSIS) PJI criteria was used as the reference standard for the diagnosis of PJI.

RESULTS

Of the 73 cases enrolled, 34 had PJI and 39 were aseptic failures. The sensitivity of DTT treated periprosthetic tissue culture (PTC) and saline treated PTC was similar (66.6% vs 58.8%, P = 0.25). The specificity of both was 100%. Sonication and DTT treatment of explanted implants showed comparable sensitivity (85.3% vs 82.4%) and specificity (100% vs 97.4%), P > 0.99. Compared to DTT treated PTC, culture of DTT treated explanted implants significantly improved the diagnosis of PJI (P = 0.03).

CONCLUSIONS

We could verify that DTT can be used to improve culture outcome in laboratories where biofilm detaching sonication techniques are not available for infected implants. In addition, we showed that it is possible to use DTT for treating tissue biopsies, but larger studies are required to confirm our findings.

Application of leukocyte esterase strip test in the screening of periprosthetic joint infections and prospects of high-precision strips

Periprosthetic joint infection (PJI) represents one of the most challenging complications after total joint arthroplasty (TJA). Despite the availability of a variety of diagnostic techniques, the diagnosis of PJI remains a challenge due to the lack of well-established diagnostic criteria. The leucocyte esterase (LE) strips test has been proved to be a valuable diagnostic tool for PJI, and its weight in PJI diagnostic criteria has gradually increased. Characterized by its convenience, speed and immediacy, leucocyte esterase strips test has a prospect of broad application in PJI diagnosis. Admittedly, the leucocyte esterase strips test has some limitations, such as imprecision and liability to interference. Thanks to the application of new technologies, such as machine reading, quantitative detection and artificial intelligence, the LE strips test is expected to overcome the limitations and improve its accuracy.

Synovial neutrophilic gelatinase-associated lipocalin in the diagnosis of periprosthetic joint infection after total knee arthroplasty

BACKGROUND

Periprosthetic joint infection (PJI) is one of the most serious complications following total knee arthroplasty (TKA). However, the diagnosis remains a challenge for clinicians. In 2011, the muscoskeletal infection society (MSIS) criteria provided a consensus which has been updated in 2013, but these criteria are complex and contain tests that are time-consuming. The same is applicable to the pro-Implant guidelines. Therefore, a simpler diagnostic test is desirable.

OBJECTIVES

The value of neutrophil gelatinase-associated lipocalin (NGAL), leucocyte esterase (LE) levels, and the white blood cell (WBC) count in synovial fluid to diagnose PJI after TKA was evaluated.

METHODS

In a retrospective cohort study, we analyzed 89 synovial fluid samples from 86 patients with suspected PJI after TKA. Thirteen and 23 of those samples were classified as PJI according to the MSIS and pro-Implant criteria, respectively. Subsequently, NGAL, LE levels, and the WBC count were determined, the former one using an immunoassay. Using either the MSIS or pro-Implant criteria as the golden standard for PJI, sensitivity and specificity of those markers were determined with ROC curves, and medians were compared with Mann-Whitney U and Pearson Chi-square tests.

RESULTS

When applying the MSIS criteria, NGAL revealed 92% sensitivity and 83% specificity. WBC count showed similar sensitivity (92%) and specificity (84%), whereas sensitivity and specificity for LE were 39% and 88% respectively. When applying the pro-Implant criteria, sensitivity was 95% and specificity was 95% for NGAL. Sensitivity and specificity for WBC count were 100% and 97% and for LE 39% and 92% respectively.

CONCLUSION

NGAL and WBC count in synovial fluid has high accuracy in the diagnosis of PJI after TKA and should seriously be considered as part of PJI diagnostics. Leucocyte esterase can serve as rule-in criterion peroperatively. These conclusions are independent of which criteria set was used as golden standard.

Sonication of antibiotic loaded cement spacers: A valuable technique for detection of infection persistence in two-stage revision for infected joint arthroplasty

We evaluated the diagnostic utility of sonication of antibiotic loaded cement spacers comparing with periprosthetic tissue cultures for the detection of persisting infection in 14 patients undergoing staged procedures. Sonication improved microbial detection of intraoperative cultures from 14.2% to 28.5% (P = 0.481). Routine sonication of spacers is recommended.

The Journey of Cultures Taken During Revision Joint Arthroplasty: Preanalytical Phase

Background: Microbiological culture has been considered the standard for pathogen identification for decades. However, culture is a laborious, time consuming, imperfect and outdated process. This study aims to inform the orthopedic community of the steps and timing of routine culture processing. Methods: We prospectively tracked 103 cultures from 33 revision hip and knee arthroplasty patients between September 2017-February 2018. Times were recorded at intraoperative collection; time of pick up from OR, transportation time; arrival at the laboratory; culture processing and plating time; and time to final result reporting. Results: Of the 103 cultures, 45.6% were processed and incubated in less than two hours, and 54.4% greater than or equal to two hours. The mean time spent in the OR, during transport, and within the laboratory prior to incubation was 0:53, 0:06 and 1:12. The range of time that samples remained at each stage varied considerably in the OR (0:03-3:33), in transit(0:04-0:16), and in the lab prior to incubation(0:26-3:01). The proportion of the total time to incubation attributed to idle time samples spent in the OR after initial sampling was 40.0%. In contrast, transport to the laboratory represented 5.1% of the total time. Idle time in the laboratory represented the greatest share at 54.9%. Conclusion: There is significant variability in the time to transport, process and incubate culture samples. Almost half of the specimens were processed outside the 2-hour recommended window. Surgeons should be aware of idle time during processing and seek to optimize their institutional pathways to maximize culture yield.

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.