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

Diagnostic and prognostic relevance of plain radiographs for periprosthetic joint infections of the hip: a literature review

Conventional radiography is regularly used to evaluate complications after total hip arthroplasty. In various recent consensus meetings, however, plain radiographs of a potentially infected hip joint have been judged as being only relevant to exclude diagnoses other than infection. Solid data on radiographic presentations of periprosthetic joint infection (PJI) are scarce. As a result, the prognostic value of radiological features in low-grade PJI remains uncertain. The present review article aims to present an overview of the available literature and to develop ideas on future perspectives to define the diagnostic possibilities of radiography in PJIs of the hip. The primary outcome of interest of this systematic review was the radiologic presentation of periprosthetic joint infections of the hip. As secondary outcome of interest served the sensitivity and specificity of the radiologic presentation of periprosthetic joint infections. Of the included articles, 26 were reviews, essays, or case reports and only 18 were clinical studies. Typical radiologic abnormalities of PJI were a periosteal reaction, a wide band of radiolucency at the cement-bone or metal-bone interface, patchy osteolysis, implant loosening, bone resorption around the implant, and transcortical sinus tracts. The frequency of their occurrence is still inadequately defined. A deeper understanding of the underlying causes and the relation between microorganisms to radiologic abnormalities can probably help clinicians in the future to diagnose a PJI. This is why further research shall focus on the radiographic features of PJI.

Interleukin-1β Polymorphisms Are Genetic Markers of Susceptibility to Periprosthetic Joint Infection in Total Hip and Knee Arthroplasty

Periprosthetic joint infections (PJIs) are serious complications of prosthetic surgery. The criteria for the diagnosis of PJI integrate clinical and laboratory findings in a complex and sometimes inconclusive workflow. Host immune factors hold potential as diagnostic biomarkers in bone and joint infections. We reported that the humoral pattern-recognition molecule long pentraxin 3 (PTX3) predicts PJI in total hip and knee arthroplasty (THA and TKA, respectively). If and how genetic variation in PTX3 and inflammatory genes that affect its expression (IL-1β, IL-6, IL-10, and IL-17A) contributes to the risk of PJI is unknown. We conducted a case-control study on a Caucasian historic cohort of THA and TKA patients who had prosthesis explant due to PJI (cases) or aseptic complications (controls). Saliva was collected from 93 subjects and used to extract DNA and genotype PTX3, IL-1β, IL-6, IL-10, and IL-17A single-nucleotide polymorphisms (SNPs). Moreover, the concentration of IL-1β, IL-10, and IL-6 was measured in synovial fluid and plasma. No association was found between PTX3 polymorphisms and PJI; however, the AGG haplotype, encompassing rs2853550, rs1143634, and rs1143627 in IL-1β, was linked to the infection (p = 0.017). Also, synovial levels of all inflammatory markers were higher in cases than in controls, and a correlation emerged between synovial concentration of PTX3 and that of IL-1β in cases only (Spearman r = 0.67, p = 0.004). We identified a relationship between rs2853550 and the synovial concentration of IL-1β and PTX3. Our findings suggest that IL-1β SNPs could be used for the early identification of THA and TKA patients with a high risk of infection.

Canadian Association of Radiologists Musculoskeletal System Diagnostic Imaging Referral Guideline

The Canadian Association of Radiologists (CAR) Musculoskeletal System Expert Panel consists of musculoskeletal radiologists, a family physician, a sports and exercise medicine physician, emergency medicine physicians, a patient advisor, and an epidemiologist/guideline methodologist. After developing a list of 25 musculoskeletal clinical/diagnostic scenarios, a systematic rapid scoping review was undertaken to identify systematically produced referral guidelines that provide recommendations for 1 or more of these clinical/diagnostic scenarios. Recommendations from 41 guidelines (50 publications) and contextualization criteria in the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) for guidelines framework were used to develop 124 recommendation statements across the 25 scenarios related to the evaluation of the musculoskeletal system. This guideline presents the methods of development and the recommendations for imaging in the context of musculoskeletal pain, infection, tumors, arthropathies, metabolic bone disease, stress injuries, orthopedic hardware, avascular necrosis/bone infarction, and complex regional pain syndrome.

Diagnostics in Late Periprosthetic Infections-Challenges and Solutions

The rising number of arthroplasties is combined with a rising number of periprosthetic joint infections, which leads to life-concerning consequences for the patients, including extended antibiotic treatment, further surgery and increased mortality. The heterogeneity of the symptoms and inflammatory response of the patients due to, e.g., age and comorbidities and the absence of a single diagnostic test with 100% accuracy make it very challenging to choose the right parameters to confirm or deny a periprosthetic joint infection and to establish a standardized definition. In recent years, additional diagnostic possibilities have emerged primarily through the increasing availability of new diagnostic methods, such as genetic techniques. The aim of the review is to provide an overview of the current state of knowledge about the various tests, including the latest developments. The combination of different tests increases the accuracy of the diagnosis. Each physician or clinical department must select the tests from the available methods that can be best implemented for them in organizational and technical terms. Serological parameters and the cultivation of the samples from aspiration or biopsy should be combined with additional synovial tests to create an accurate figure for the failure of the prosthesis, while imaging procedures are used to obtain additional information for the planned therapeutic procedure.

Potential value of a rapid syndromic multiplex PCR for the diagnosis of native and prosthetic joint infections: a real-world evidence study

Introduction: The BIOFIRE Joint Infection (JI) Panel is a diagnostic tool that uses multiplex-PCR testing to detect microorganisms in synovial fluid specimens from patients suspected of having septic arthritis (SA) on native joints or prosthetic joint infections (PJIs). Methods: A study was conducted across 34 clinical sites in 19 European and Middle Eastern countries from March 2021 to June 2022 to assess the effectiveness of the BIOFIRE JI Panel. Results: A total of 1527 samples were collected from patients suspected of SA or PJI, with an overall agreement of 88.4 % and 85 % respectively between the JI Panel and synovial fluid cultures (SFCs). The JI Panel detected more positive samples and microorganisms than SFC, with a notable difference on Staphylococcus aureus, Streptococcus species, Enterococcus faecalis, Kingella kingae, Neisseria gonorrhoeae, and anaerobic bacteria. The study found that the BIOFIRE JI Panel has a high utility in the real-world clinical setting for suspected SA and PJI, providing diagnostic results in approximately 1 h. The user experience was positive, implying a potential benefit of rapidity of results' turnover in optimising patient management strategies. Conclusion: The study suggests that the BIOFIRE JI Panel could potentially optimise patient management and antimicrobial therapy, thus highlighting its importance in the clinical setting.

Musculoskeletal infections through direct inoculation

Musculoskeletal infections consist of different clinical conditions that are commonly encountered in daily clinical settings. As clinical findings and even laboratory tests cannot always be specific, imaging plays a crucial role in the diagnosis and treatment of these cases. Musculoskeletal infections most commonly occur secondary to direct inoculation into the skin involuntarily affected by trauma, microorganism, foreign bodies, or in diabetic ulcers; direct infections can also occur from voluntary causes due to surgery, vaccinations, or other iatrogenic procedures. Hematogenous spread of infection from a remote focus can also be a cause for musculoskeletal infections. Risk factors for soft tissue and bone infections include immunosuppression, old age, corticosteroid use, systemic illnesses, malnutrition, obesity, and burns. Most literature discusses musculoskeletal infections according to the diagnostic tools or forms of infection seen in different soft tissue anatomical planes or bones. This review article aims to evaluate musculoskeletal infections that occur due to direct inoculation to the musculoskeletal tissues, by focusing on the traumatic mechanism with emphasis on the radiological findings.

Diagnostic cutoff values of synovial fluid biomarkers for acute postoperative prosthetic joint infection: a systematic review and meta-analysis

Introduction: The assessment of white blood cell (WBC) count and polymorphonuclear cell (PMN) percentage in synovial fluid can help in the diagnosis of acute postoperative peri-prosthetic joint infection (PJI). Their cutoff values, which would differ from those for chronic PJI, have not yet been determined in acute postoperative PJI. The aim of this study was (1) to analyse studies reporting the optimal cutoff values for WBC count and the PMN percentage in synovial fluid and (2) to determine which is the best diagnostic tool for acute postoperative PJI. Methods: We performed a systematic review (SR) of primary studies analysing WBC count and the PMN percentage for diagnosis of acute postoperative PJI. A search was performed in MEDLINE and EMBASE. We studied the risk of bias and quality assessment. We extracted data on cutoff values, sensitivity, specificity, positive and negative predictive value, area under the curve, and accuracy. We calculated the diagnosis odds ratio (DOR), performed the meta-analysis and summarized receiver operating curves (sROCs) for WBC count and the PMN percentage. Results: We included six studies. WBC count showed a DOR of 123.61 (95 % CI: 55.38-275.88), an sROC with an area under the curve (AUC) of 0.96 (SE: 0.009) and a Q index of 0.917. The PMN percentage showed a summary DOR of 18.71 (95 % CI: 11.64-30.07), an sROC with an AUC 0.88 (SE: 0.018) and a Q index of 0.812. Conclusion: We concluded that WBC count and the PMN percentage are useful tests for the diagnosis of acute PJI; WBC is the more powerful of the two. Studies centred on other synovial fluid biomarkers not yet studied could help in this diagnosis.

Management of septic arthritis and prosthetic joint infection

Management of joint infection is an evolving topic. This article reviews the literature on the management of native and prosthetic joint infection and suggests some areas of improvement in short- and long-term management which could lead to better patient outcomes. Surgical management is the mainstay of treatment for native or prosthetic knee infection and aspiration should only be used for diagnostic purposes. A multidisciplinary team approach and compliance with national guidelines, alongside referral networks and pooling of expertise, should be mandatory to improve patient outcomes.

Imaging approach to prosthetic joint infection

The diagnosis of prosthetic joint infection (PJI) remains challenging, despite multiple available laboratory tests for both serum and synovial fluid analysis. The clinical symptoms of PJI are not always characteristic, particularly in the chronic phase, and there is often significant overlap in symptoms with non-infectious forms of arthroplasty failure. Further exacerbating this challenge is lack of a universally accepted definition for PJI, with publications from multiple professional societies citing different diagnostic criteria. While not included in many of the major societies' guidelines for diagnosis of PJI, diagnostic imaging can play an important role in the workup of suspected PJI. In this article, we will review an approach to diagnostic imaging modalities (radiography, ultrasound, CT, MRI) in the workup of suspected PJI, with special attention to the limitations and benefits of each modality. We will also discuss the role that image-guided interventions play in the workup of these patients, through ultrasound and fluoroscopically guided joint aspirations. While there is no standard imaging algorithm that can universally applied to all patients with suspected PJI, we will discuss a general approach to diagnostic imaging and image-guided intervention in this clinical scenario.

Practice of 18F-FDG-PET/CT in ICU Patients: A Systematic Review

18F-FDG-PET/CT imaging has become a key tool to evaluate infectious and inflammatory diseases. However, application of 18F-FDG-PET/CT in patients in the intensive care unit (ICU) is limited, which is remarkable since the development of critical illness is closely linked to infection and inflammation. This limited use is caused by perceived complexity and risk of planning and executing 18F-FDG-PET/CT in such patients. The aim of this systematic review was to investigate the feasibility of 18F-FDG-PET/CT in ICU patients with special emphasis on patient preparation, transport logistics and safety. Therefore, a systematic search was performed in PubMed, Embase, and Web of Science using the search terms: intensive care, critically ill, positron emission tomography and 18F-FDG or derivates. A total of 1183 articles were found of which 10 were included. Three studies evaluated the pathophysiology of acute respiratory distress syndrome, acute lung injury and acute chest syndrome. Three other studies applied 18F-FDG-PET/CT to increase understanding of pathophysiology after traumatic brain injury. The remaining four studies evaluated infection of unknown origin. These four studies showed a sensitivity and specificity between 85%-100% and 57%-88%, respectively. A remarkable low adverse event rate of 2% was found during the entire 18F-FDG-PET/CT procedure, including desaturation and hypotension. In all studies, a team consisting of an intensive care physician and nurse was present during transport to ensure continuation of necessary critical care. Full monitoring during transport was used in patients requiring mechanical ventilation or vasopressor support. None of the studies used specific patient preparation for ICU patients. However, one article described specific recommendations in their discussion. In conclusion, 18F-FDG-PET/CT has been shown to be feasible and safe in ICU patients, even when ventilated or requiring vasopressors. Specific recommendations regarding patient preparation, logistics and scanning are needed. Including 18F-FDG-PET/CT in routine workup of infection of unknown origin in ICU patients showed potential to identify source of infection and might improve outcome.

Diagnostic value of magnetic resonance imaging for patients with periprosthetic joint infection: a systematic review

PURPOSE

The purpose of this study was to provide a critical systematic review of the role of magnetic resonance imaging (MRI) as a noninvasive method to assess periprosthetic joint infections (PJIs).

METHODS

The electronic databases PubMed and EMBASE were searched, since their inception up to March 27, 2022. The included studies evaluated the reproducibility and accuracy of MRI features to diagnose PJIs. The article quality assessment was conducted by the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) and Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2).

RESULTS

Among 1909 studies identified in the initial search, 8 studies were eligible for final systematic review. The included studies evaluated the reproducibility and accuracy of MRI features to diagnose PJIs. Seven of 8 studies showed good to excellent reliability, but only one article among them in which accuracy was evaluated had a low risk of bias. The intraclass correlation coefficient (ICC) and Cohen coefficient (κ) varied between 0.44 and 1.00. The accuracy varied between 63.9% and 94.4%. Potential MRI features, such as lamellated hyperintense synovitis, edema, fluid collection, or lymphadenopathy, might be valuable for diagnosing PJIs.

CONCLUSION

The quality of the evidence regarding the role of MRI for PJIs diagnosis was low. There is preliminary evidence that MRI has a noteworthy value of distinguishing suspected periprosthetic joint infection in patients with total knee arthroplasty or total hip arthroplasty, but the definition of specific MRI features related to PJIs diagnosis lacks consensus and standardization. Large-scale studies with robust quality were required to help make better clinical decisions in the future.

HGT: A Hierarchical GCN-Based Transformer for Multimodal Periprosthetic Joint Infection Diagnosis Using Computed Tomography Images and Text

Prosthetic joint infection (PJI) is a prevalent and severe complication characterized by high diagnostic challenges. Currently, a unified diagnostic standard incorporating both computed tomography (CT) images and numerical text data for PJI remains unestablished, owing to the substantial noise in CT images and the disparity in data volume between CT images and text data. This study introduces a diagnostic method, HGT, based on deep learning and multimodal techniques. It effectively merges features from CT scan images and patients' numerical text data via a Unidirectional Selective Attention (USA) mechanism and a graph convolutional network (GCN)-based Feature Fusion network. We evaluated the proposed method on a custom-built multimodal PJI dataset, assessing its performance through ablation experiments and interpretability evaluations. Our method achieved an accuracy (ACC) of 91.4% and an area under the curve (AUC) of 95.9%, outperforming recent multimodal approaches by 2.9% in ACC and 2.2% in AUC, with a parameter count of only 68 M. Notably, the interpretability results highlighted our model's strong focus and localization capabilities at lesion sites. This proposed method could provide clinicians with additional diagnostic tools to enhance accuracy and efficiency in clinical practice.

Machine Learning for Detecting Total Knee Arthroplasty Implant Loosening on Plain Radiographs

(1) Background: The purpose of this study was to investigate whether the loosening of total knee arthroplasty (TKA) implants could be detected accurately on plain radiographs using a deep convolution neural network (CNN). (2) Methods: We analyzed data for 100 patients who underwent revision TKA due to prosthetic loosening at a single institution from 2012 to 2020. We extracted 100 patients who underwent primary TKA without loosening through a propensity score, matching for age, gender, body mass index, operation side, and American Society of Anesthesiologists class. Transfer learning was used to prepare a detection model using a pre-trained Visual Geometry Group (VGG) 19. For transfer learning, two methods were used. First, the fully connected layer was removed, and a new fully connected layer was added to construct a new model. The convolutional layer was frozen without training, and only the fully connected layer was trained (transfer learning model 1). Second, a new model was constructed by adding a fully connected layer and varying the range of freezing for the convolutional layer (transfer learning model 2). (3) Results: The transfer learning model 1 gradually increased in accuracy and ultimately reached 87.5%. After processing through the confusion matrix, the sensitivity was 90% and the specificity was 100%. Transfer learning model 2, which was trained on the convolutional layer, gradually increased in accuracy and ultimately reached 97.5%, which represented a better improvement than for model 1. Processing through the confusion matrix affirmed that the sensitivity was 100% and the specificity was 97.5%. (4) Conclusions: The CNN algorithm, through transfer learning, shows high accuracy for detecting the loosening of TKA implants on plain radiographs.

Chronic Suppressive Antibiotic Treatment for Staphylococcal Bone and Joint Implant-Related Infections

Prosthetic joint infection (PJI) and fracture-related infection (FRI) are difficult-to-treat conditions in patients with severe comorbidity or significant surgical risk. In cases not eligible for standard strategy, debridement procedures with the retention of prosthesis or internal fixation device, combined with long-term antibiotic treatment and subsequent indefinite chronic oral antimicrobial suppression (COAS), can be the only reasonable choice. The aim of this study was to investigate the role of COAS and its follow-up in the management of these cases. We retrospectively analyzed a cohort of 16 patients with a follow-up of at least 6 months (mean age 75 yo, 9F, 7M, 11 PJI, 5 FRI). All microbiological isolates were tetracycline-susceptible staphylococci and for this reason a minocycline-based COAS was adopted after debridement and 3 months of antibiogram-guided antibiotic treatment. Patient monitoring was carried out on a clinical basis, with bimonthly execution of the inflammation indices and serial radiolabeled leukocyte scintigraphy (LS). The overall median time of COAS follow-up was 15 months (min 6-max 30). Moreover, 62.5% of patients were still taking COAS with no relapse after cure at the last evaluation available. Clinical failure with a relapse of the infection was observed in 37.5% of patients; interestingly, 50% of them had previously stopped COAS due to side effects of the antibiotic used. In the COAS follow-up, a combination of clinical, laboratory and LS evaluation seems to monitor the infection properly. COAS can be considered as an interesting approach in patients not suitable for standard treatments of PJI or FRI but it requires careful monitoring.

Emerging Technologies in Diagnosing Periprosthetic Joint Infections

Periprosthetic joint infection (PJI) is a well-known serious complication following joint replacement surgeries and is responsible for high failure rates of implanted devices. Any delay in the diagnosis can compromise treatment success, putting a huge burden on the patients' wellness and healthcare systems. Diagnosing PJIs is quite complex as there is still no gold standard test to reach the definitive diagnosis in a timely manner. A number of laboratory tests and radiological imaging inventions have evolved in the past few years, requiring consistent updates of the available guidelines to keep up with the latest advances in the field. This article highlights the recent advances in diagnosing PJIs and discusses their validity for use in clinical practice.

Image-guided synovial biopsy with a focus on infection

Image-guided biopsy of the synovium is a relatively uncommon but safe procedure with a high-diagnostic yield in the correct clinical scenario. Whilst surgical and arthroscopic techniques are still commonly performed and remain the gold standard, they are more invasive, expensive and not widely available. Ultrasound and X-ray-guided synovial biopsy are being increasingly performed by radiologists to diagnose both native and periprosthetic joint infection (PJI) to guide surgical and microbiological management. The purpose of this review article is to present the historical background to synovial biopsy particularly related to potential joint infection, including common and uncommon pathogens encountered, sampling techniques and pitfalls, focusing mainly on its role in PJI and its role in patient pathways and decision-making within a joint infection multi-disciplinary framework.

Detection of Prosthetic Loosening in Hip and Knee Arthroplasty Using Machine Learning: A Systematic Review and Meta-Analysis

Background: prosthetic loosening after hip and knee arthroplasty is one of the most common causes of joint arthroplasty failure and revision surgery. Diagnosis of prosthetic loosening is a difficult problem and, in many cases, loosening is not clearly diagnosed until accurately confirmed during surgery. The purpose of this study is to conduct a systematic review and meta-analysis to demonstrate the analysis and performance of machine learning in diagnosing prosthetic loosening after total hip arthroplasty (THA) and total knee arthroplasty (TKA). Materials and Methods: three comprehensive databases, including MEDLINE, EMBASE, and the Cochrane Library, were searched for studies that evaluated the detection accuracy of loosening around arthroplasty implants using machine learning. Data extraction, risk of bias assessment, and meta-analysis were performed. Results: five studies were included in the meta-analysis. All studies were retrospective studies. In total, data from 2013 patients with 3236 images were assessed; these data involved 2442 cases (75.5%) with THAs and 794 cases (24.5%) with TKAs. The most common and best-performing machine learning algorithm was DenseNet. In one study, a novel stacking approach using a random forest showed similar performance to DenseNet. The pooled sensitivity across studies was 0.92 (95% CI 0.84-0.97), the pooled specificity was 0.95 (95% CI 0.93-0.96), and the pooled diagnostic odds ratio was 194.09 (95% CI 61.60-611.57). The I2 statistics for sensitivity and specificity were 96% and 62%, respectively, showing that there was significant heterogeneity. The summary receiver operating characteristics curve indicated the sensitivity and specificity, as did the prediction regions, with an AUC of 0.9853. Conclusions: the performance of machine learning using plain radiography showed promising results with good accuracy, sensitivity, and specificity in the detection of loosening around THAs and TKAs. Machine learning can be incorporated into prosthetic loosening screening programs.

The synovial fluid calprotectin lateral flow test for the diagnosis of chronic prosthetic joint infection in failed primary and revision total hip and knee arthroplasty

PURPOSE

The diagnostic criteria of prosthetic joint infection (PJI) recommended by the most commonly used diagnostic algorithms can be obscured or distorted by other inflammatory processes or aseptic pathology. Furthermore, the most reliable diagnostic criteria are garnered during revision surgery. A robust, reliable addition to the preoperative diagnostic cascade is warranted. Calprotectin has been shown to be an excellent diagnostic marker for PJI. In this study, we aimed to evaluate a lateral flow test (LFT) in the challenging patient cohort of a national referral centre for revision arthroplasty.

METHODS

Beginning in March 2019, we prospectively included patients scheduled for arthroplasty exchange of a total hip (THA) or knee arthroplasty (TKA). Synovial fluid samples were collected intra-operatively. We used the International Consensus Meeting of 2018 (ICM) score as the gold standard. We then compared the pre-operative ICM score with the LFT result to calculate its diagnostic accuracy as a standalone pre-operative marker and in combination with the ICM score as part of an expanded diagnostic workup.

RESULTS

A total of 137 patients with a mean age of 67 (± 13) years with 53 THA and 84 TKA were included. Ninety-nine patients (72.8%) were not infected, 34 (25.0) were infected, and four (2.9%) had an inconclusive final score and could not be classified after surgery. The calprotectin LFT had a sensitivity (95% confidence interval) of 0.94 (0.80-0.99) and a specificity of 0.87 (0.79-0.93). The area under the receiver operating characteristic curve (AUC) for the calprotectin LFT was 0.94 (0.89-0.99). In nine cases with an inconclusive pre-operative ICM score, the calprotectin LFT would have led to the correct diagnosis of PJI.

CONCLUSIONS

The synovial fluid calprotectin LFT shows excellent diagnostic metrics both as a rule-in and a rule-out test, even in a challenging patient cohort with cases of severe osteolysis, wear disease, numerous preceding surgeries, and poor soft tissue conditions, which can impair the common diagnostic criteria. As it is available pre-operatively, this test might prove to be a very useful addition to the diagnostic algorithm.

MRI-based artificial intelligence to predict infection following total hip arthroplasty failure

PURPOSE

To investigate whether artificial intelligence (AI) can differentiate septic from non-septic total hip arthroplasty (THA) failure based on preoperative MRI features.

MATERIALS AND METHODS

We included 173 patients (98 females, age: 67 ± 12 years) subjected to first-time THA revision surgery after preoperative pelvis MRI. We divided the patients into a training/validation/internal testing cohort (n = 117) and a temporally independent external-testing cohort (n = 56). MRI features were used to train, validate and test a machine learning algorithm based on support vector machine (SVM) to predict THA infection on the training-internal validation cohort with a nested fivefold validation approach. Machine learning performance was evaluated on independent data from the external-testing cohort.

RESULTS

MRI features were significantly more frequently observed in THA infection (P < 0.001), except bone destruction, periarticular soft-tissue mass, and fibrous membrane (P > 0.005). Considering all MRI features in the training/validation/internal-testing cohort, SVM classifier reached 92% sensitivity, 62% specificity, 79% PPV, 83% NPV, 82% accuracy, and 81% AUC in predicting THA infection, with bone edema, extracapsular edema, and synovitis having been the best predictors. After being tested on the external-testing cohort, the classifier showed 92% sensitivity, 79% specificity, 89% PPV, 83% NPV, 88% accuracy, and 89% AUC in predicting THA infection. SVM classifier showed 81% sensitivity, 76% specificity, 66% PPV, 88% NPV, 80% accuracy, and 74% AUC in predicting THA infection in the training/validation/internal-testing cohort based on the only presence of periprosthetic bone marrow edema on MRI, while it showed 68% sensitivity, 89% specificity, 93% PPV, 60% NPV, 75% accuracy, and 79% AUC in the external-testing cohort.

CONCLUSION

AI using SVM classifier showed promising results in predicting THA infection based on MRI features. This model might support radiologists in identifying THA infection.

Metal Artifact Reduction MRI in the Diagnosis of Periprosthetic Hip Joint Infection

A 54-year-old woman presented with progressive right hip pain after hip arthroplasty 9 years earlier. The emerging role of metal artifact reduction MRI in the noninvasive diagnosis of infectious synovitis as the surrogate marker for periprosthetic hip joint infection and differentiation from other synovitis types is discussed.

Spacer exchange in persistent periprosthetic joint infection: microbiological evaluation and survivorship analysis

PURPOSE

The purposes of this study were to determine demographics and characteristics of patients who underwent spacer exchange for persistent infection in the setting of two-stage arthroplasty for periprosthetic joint infection, to describe the microbiology of pathogens involved, to analyze survivorship free from infection in these patients.

METHODS

The institutional prospectively collected database was reviewed to enroll patients with minimum 2 years follow-up. Patients who underwent two-stage procedure for septic arthritis were excluded, as were patients who had spacer fracture or dislocation.

RESULTS

A total of 34 patients (41 procedures) were included. Mean age was 65.0 ± 12.8 years. Mean follow-up was 53.4 ± 24.8 months. Mean number of previous procedures was 3.6 ± 1.2. A total of 27 (79.4%) patients underwent final reimplantation. The most frequently isolated pathogen in spacer exchange was Staphylococcus epidermidis (10 cases, 28.6%). Polymicrobial cultures were obtained from 9 (25.71%) patients, 10 (28.6%) presented culture-negative infections. A total of 11 (32.4%) resistant pathogens were isolated, and 16 (47.0%) difficult to treat pathogens were detected. Eradication rate was 78.8%. Overall survivorship of implants after final reimplantation was 72.8% at 51.8 months.

CONCLUSION

Surgeons should be aware that subjects necessitating spacer exchange often present multiple comorbidities, previous staged revision failures, soft-tissue impairment and difficult to treat infection. In these patients, spacer exchange provides good clinical results and infection eradication, preventing arthrodesis or amputation.

Success of staged revision reverse total shoulder arthroplasty in eradication of periprosthetic joint infection

INTRODUCTION

Management of periprosthetic joint infection (PJI) in shoulder arthroplasty remains a challenge, with no established gold standard treatment. This study presents the unique experience of a high-volume single-surgeon, single-institution approach on staged revision reverse total shoulder arthroplasty (RTSA) for infection. The authors theorize that staged revision RTSA is an effective treatment for PJI.

MATERIALS AND METHODS

Between 2013 and 2018, 38 patients underwent a staged RTSA for treatment of PJI. Patient histories were collected and classified using Cierny-Mader classification. Infection workup for all patients included radiographs, laboratory indices, and computed tomographic aspiration arthrogram. PJI was identified based on high clinical and radiographic suspicion, elevated serologic markers, and/or aspirate culture results per 2018 International Consensus Meeting Shoulder guidelines on Orthopedic Infections. All patients underwent first stage with implant removal, irrigation and débridement, and antibiotic spacer placement. Next, intravenous antibiotics were administered by infectious disease consultants for a minimum of 6 weeks. Infection workup was then repeated and, if normalized, final-stage revision commenced with antibiotic spacer removal and revision to RTSA. If indices were persistently abnormal, an additional stage of débridement and spacer placement procedure was performed. Treatment failure was defined as recurrent periprosthetic infection after final prosthesis implantation or persistently elevated indices despite adequate débridement and spacer placement.

RESULTS

Mean age of the cohort was 68 (standard deviation [SD] 8.9) years and mean follow-up was 33 (SD 14) months with 34 Cierny-Mader C hosts and 4 B hosts. Patients underwent a mean of 2 (SD 1.1) previous surgeries. The staged revision protocol was successful in 34 (89.5%) patients for management of PJI. Four patients (10.5%) were considered failures with recurrent infections at a mean of 13 months (range 2-26 months) after the final RTSA implantation and underwent repeat staged revisions. Of the 34 patients who had successful infection eradication, 31 had 2-stage treatment and 3 had to undergo 3 stages. There were no treatment-associated mortalities and 10 major complications (26%), including permanent neuropathy, instability, and periprosthetic fractures. The most common cultured microorganism was Cutibacterium acnes (18%), with no polymicrobial infections detected.

DISCUSSION

Although there are multiple treatment options for PJI management, staged revision remains an effective means of treatment. Although there were several patients who required an additional stage of treatment, and a significant complication rate, staged revision RTSA proved successful in the ultimate eradication of the PJI.

Current Status of SPECT Radiopharmaceuticals for Specific Bacteria Imaging

Imaging infection still represents a challenge for researchers. Despite nuclear medicine (NM) offers valuable tools able to discriminate between infections and inflammation, there is an unmet clinical need to develop new strategies able to specifically target the causative pathogen, to select the best antimicrobial treatment for each patient and to accurately assess therapeutic efficacy. These aspects are commonly addressed by microbiology or histology but the diagnosis often relies on invasive procedures that are prone to contamination or sample bias and do not reflect the spatial heterogeneity of the infective process. Therefore, in the era of personalized medicine and treatment, a lot of efforts are in play to improve a personalized diagnosis. Molecular imaging is an ideal candidate for this purpose and, indeed, research is going fast to this direction aiming to find more selective and proper antimicrobial treatments and to overcome broad-spectrum antibiotic use, which still represents the major cause of bacterial drug-resistance. Several approaches for specifically image bacteria have been proposed and provided encouraging perspectives in preclinical studies. Nevertheless, the majority of these promising approaches are still confined in "bench stages" and crucial issues still need to be addressed before their translation in clinical practice. This review will focus on radiolabeled antibiotics for SPECT imaging of bacteria, their mechanisms of action, their potentiality and limitations for "bed-side" applications.

Expert opinions in nuclear medicine: Finding the "holy grail" in infection imaging

Nuclear medicine imaging techniques are now widely accepted and increasingly used for diagnosing and treatment monitoring of infectious and inflammatory diseases. The latter has been exemplified by numerous recent clinical guidelines in which PET imaging is now part of the diagnostic flowcharts. In this perspective paper we discuss the current available guidelines, the current limitations, and we provide the future aims of research to achieve the holy grail in nuclear medicine: the differentiation between infection, inflammation and malignancy.

Antibiotic Stewardship in Treatment of Osteoarticular Infections Based on Local Epidemiology and Bacterial Growth Times

Incubation for 14 days is recommended for the culture of microorganisms from osteoarticular infections (OAI), but there are no recommendations for postoperative antibiotic stewardship concerning empirical antimicrobial therapy (EAT), while prolonging broad-spectrum EAT results in adverse effects. The aim of this study was to describe the local OAI epidemiology with consideration of bacterial growth times to determine which antibiotic stewardship intervention should be implemented in cases of negative culture after 2 days of incubation. We performed a 1-year, single-center, noninterventional cohort study at the Pitié-Salpêtrière hospital OAI reference center. Samples were taken as part of the local standard of care protocol for adult patients who underwent surgery for OAI (native or device related) and received EAT (i.e., piperacillin-tazobactam plus daptomycin [PTD]) following surgery. The time to culture positivity was monitored daily. Overall, 147 patients were recruited, accounting for 151 episodes of OAI, including 112 device-related infections. Microbiological cultures were positive in 144 cases, including 42% polymicrobial infections. Overall, a definitive microbiological result was obtained within 48 h in 118 cases (78%) and within 5 days in 130 cases (86%). After 5 days, only Gram-positive bacteria were recovered, especially Cutibacterium acnes, Staphylococcus spp., and Streptococcus spp. Overall, 90% of culture-positive OAI were correctly treated with the locally established EAT. EAT guidance for OAI was in agreement with our local epidemiology. Our results supported antibiotic stewardship intervention consisting of stopping piperacillin-tazobactam treatment at day 5 in cases of negative culture. IMPORTANCE Osteoarticular infections (OAI) remain challenging to diagnose and to treat. One of the issues concerns postoperative empirical antimicrobial therapy (EAT), which is usually a combination of broad-spectrum antibiotics. This EAT is maintained up to 2 weeks, until the availability of the microbiological results (identification and drug susceptibility testing of the microorganisms responsible for the OAI). Our results provide new data that will help to improve OAI management, especially EAT. Indeed, we have shown that antibiotic stewardship intervention consisting of stopping the antibiotic targeting Gram-negative bacteria included in the EAT could be implemented in cases where culture is negative after 5 days of incubation. The benefits of such an antibiotic stewardship plan include improved patient outcomes, reduced adverse events (including Clostridioides difficile infection), improvement in rates of susceptibilities to targeted antibiotics, and optimization of resource utilization across the continuum of care.

The concordance between preoperative synovial fluid culture and intraoperative tissue cultures in periprosthetic joint infection: a systematic review

Background: this systematic review aims to evaluate the concordance between preoperative synovial fluid culture and intraoperative tissue cultures in patients with periprosthetic joint infection (PJI) undergoing total hip (THA) or knee arthroplasty (TKA) revision surgery. Methods: this review was conducted in accordance with the preferred reporting items for a systematic review and meta-analysis of diagnostic test accuracy studies (PRISMA-DTA) statement. Cochrane, Embase, PubMed, and Web of Science databases were searched to identify studies involving patients who had THA or TKA revision surgery for PJI and for whom preoperative synovial fluid culture and intraoperative tissue cultures were performed. Studies were only included if the diagnosis of PJI was based on the EBJIS (the European Bone and Joint Infection Society) or MSIS (Musculoskeletal Infection Society) criteria. Risk of bias was assessed using an amended version of Joanna Briggs Institute's (JBI) critical appraisal checklist for case series. Results: seven studies were included in this review comprising 1677 patients. All studies had a retrospective study design and five studies explored patients undergoing revision surgery of THA or TKA. Concordance rates varied between 52 % and 79 %, but different authors defined and calculated concordance differently. Six studies were judged as having an unclear to high risk of bias and one study as having a low risk of bias. Conclusions: the included studies showed a wide range of concordance rates between preoperative synovial fluid culture and intraoperative tissue cultures and the majority of studies had a high risk of bias. Higher-quality studies are warranted to obtain a more accurate estimate of this concordance rate. We recommend continuing the use of a system such as the EBJIS definition or MSIS criteria when diagnosing PJI.

D-lactate is a promising biomarker for the diagnosis of periprosthetic joint infection

Introduction

Reliable biomarkers for the diagnosis of periprosthetic joint infection (PJI) are of paramount clinical value. To date, synovial fluid leukocyte count is the standard surrogate parameter indicating PJI. As D-lactate is almost solely produced by bacteria, it represents a promising molecule in the diagnostic workflow of PJI evaluation. Therefore, the purpose of this study was to assess the performance of synovial fluid D-lactate for diagnosing PJI of the hip and knee.

Materials and Methods

These are preliminary results of a prospective multicenter study from one academic center. Seventy-two consecutive patients after total hip arthroplasty (THA) or total knee arthroplasty (TKA) were prospectively included. All patients received a joint aspiration in order to rule out or confirm PJI, which was diagnosed according to previously published institutional criteria. Synovial fluid D-lactate was determined spectrophotometrically at 450 nm. Receiver operating characteristic (ROC) analysis was performed to assess the diagnostic performance.

Results

Eighteen patients (25%) were diagnosed with PJI and 54 patients (75%) were classified as aseptic. Synovial fluid D-lactate showed a sensitivity of 90.7% (95% CI: 79.7%-96.9%) and specificity of 83.3% (95% CI: 58.6%-96.4%) at a cut-off of 0.04 mmol/L. The median concentration of D-lactate was significantly higher in patients with PJI than in those with aseptic conditions (0.048 mmol/L, range, 0.026-0.076 mmol/L vs. 0.024 mmol/L, range, 0.003-0.058 mmol/L, p < 0.0001). The predominat microogranisms were staphylococci, followed by streptococci and gram-negative bacteria.

Conclusion

D-lactate bears a strong potential to act as a valuable biomarker for diagnosing PJI of the hip and knee. In our study, a cutoff of 0.04 mmol/L showed a comparable sensitivity to synovial fluid leukocyte count. However, its specificity was higher compared to conventional diagnostic tools. The additional advantages of D-lactate testing are requirement of low synovial fluid volume, short turnaround time and low cost.

Management of periprosthetic knee joint infections: focus on the role of Nuclear Medicine (v2)

BACKGROUND

When faced with a painful knee replacement, ruling out infection is mandatory to set the correct therapeutic approach. However, it is not always easy, especially in subclinical/chronic infections. A multidisciplinary approach is necessary to assess in the most correct way each case of suspected periprosthetic knee joint infection. This review explores the role of nuclear medicine investigations in the management of periprosthetic knee infections and their proper use within a multidisciplinary pathway.

METHODS

A PubMed search was conducted selecting studies from the past 10 years.

RESULTS

Triphasic bone scintigraphy has high sensitivity (93%) but poor specificity (56%) for periprosthetic joint infections of the knee, with a high negative predictive value (NPV), ranging from 96% to 100%. Consequently, a negative bone scan is useful in ruling out infection. In contrast, radiolabeled leukocyte scintigraphy is characterized by a sensitivity of 85.7-93%, specificity of 93.6-100%, diagnostic accuracy of 92.6-98%, NPV of 93-97.8%, and positive predictive value (PPV) of 66.7-100%. By adding a tomographic acquisition with hybrid single-photon emission computed tomography combined with computed tomography technique (SPECT/CT), the diagnostic accuracy increases. Because 18F-fluorodeoxyglucose (FDG) accumulates at both sites of inflammation and infection, FDG positron emission tomography (PET/CT) shows low specificity.

CONCLUSIONS

A common decision-making process in the diagnosis of periprosthetic joint infection is not yet validated and multidisciplinary integration is mandatory. In this context, nuclear medicine can contribute decisively.

The Ratio of IL-6 to IL-4 in Synovial Fluid of Knee or Hip Performances a Noteworthy Diagnostic Value in Prosthetic Joint Infection

The diagnosis of prosthetic joint infection (PJI) is still a challenge, the ratio of interleukin-6 (IL-6) to IL-4 in the joint fluid of knee or hip was used to analyze whether the diagnostic accuracy of PJI can be improved. Between January 2017 and May 2022, 180 patients who developed pain after revision total hip or knee arthroplasty were enrolled retrospectively. 92 patients of PJI and 88 of aseptic failure were included. PJI was as defined by the Musculoskeletal Infection Society (MSIS). The content of IL-6 and IL-4 in synovial fluid of knee or hip were measured, and the areas under the receiver operating characteristic curve (ROC) and IL-6/IL-4 curve were analyzed to obtain a better diagnostic effect. The area under the curve of IL-6/IL-4 in synovial fluid of knee or hip was 0.9623, which was more accurate than ESR 0.5994 and C-reactive protein 0.6720. The optimal threshold of IL-6/IL-4 ratio was 382.10. Its sensitivity and specificity were 81.32% and 98.86%, respectively. The positive predictive value for the diagnosis of PJI was 98.91%. This study showed that the level of IL-6/IL-4 in synovial fluid of knee or hip could further improve the diagnostic accuracy for PJI.

ACR Appropriateness Criteria® Suspected Osteomyelitis, Septic Arthritis, or Soft Tissue Infection (Excluding Spine and Diabetic Foot): 2022 Update

Musculoskeletal infections involve bones, joints, and soft tissues. These infections are a common clinical scenario in both outpatient and emergent settings. Although radiography provides baseline findings, a multimodality approach is often implemented to provide more detailed information on the extent of infection involvement and complications. MRI with intravenous contrast is excellent for the evaluation of musculoskeletal infections and is the most sensitive for diagnosing osteomyelitis. MRI, CT, and ultrasound can be useful for joint and soft tissue infections. When MRI or CT is contraindicated, bone scans and the appropriate utilization of other nuclear medicine scans can be implemented for aiding in the diagnostic imaging of infection, especially with metal hardware and arthroplasty artifacts on MRI and CT. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Ultrasound evaluations and guided procedures of the painful joint arthroplasty

The purpose of this article is to describe the use of ultrasound for the diagnosis and treatment of painful joint arthroplasty. Ultrasound plays a crucial role in the diagnosis of the painful joint arthroplasty, especially given its unique dynamic capabilities, convenience, and high resolution. Ultrasound guidance is also instrumental for procedures in both diagnosing and in select cases, treating the painful joint arthroplasty. Topics to be discussed in this article include trends in arthroplasty placement, benefits of the use of ultrasound overall, and ultrasound evaluation of periprosthetic joint infections. We will also review the sonographic findings with dissociated/displaced components and adverse reaction to metallic debris including metallosis, trunnionosis, and metal-on-metal pseudotumors. Additionally, we will discuss ultrasound evaluation of tendon pathologies with arthroplasties, including dynamic maneuvers to evaluate for tendon impingement/snapping. Finally, we will cover ultrasound-guided joint arthroplasty injection indications and precautions. KEY POINTS: • Ultrasound is preferred over MRI in patients with joint arthroplasty and plays a crucial role in diagnosis, especially given its unique dynamic capabilities, convenience and high resolution. • It is especially beneficial for US-guided aspiration in periprosthetic joint infections; effectively used to evaluate periprosthetic fluid collections, facilitating differentiation between abscesses and aseptic collections, and tracking sinus tracts. • Recently, the diagnosis of periprosthetic joint infections has shifted focus to biomarkers in the periprosthetic fluid, specifically α-defensin, which has a high sensitivity and specificity for diagnosing infection. • Cutibacterium acnes is a major pathogen responsible for shoulder arthroplasty infections, often presenting with normal laboratory values and since slow growing, must be kept for a minimum of 14 days.

Differential metabolism between biofilm and suspended Pseudomonas aeruginosa cultures in bovine synovial fluid by 2D NMR-based metabolomics

Total joint arthroplasty is a common surgical procedure resulting in improved quality of life; however, a leading cause of surgery failure is infection. Periprosthetic joint infections often involve biofilms, making treatment challenging. The metabolic state of pathogens in the joint space and mechanism of their tolerance to antibiotics and host defenses are not well understood. Thus, there is a critical need for increased understanding of the physiological state of pathogens in the joint space for development of improved treatment strategies toward better patient outcomes. Here, we present a quantitative, untargeted NMR-based metabolomics strategy for Pseudomonas aeruginosa suspended culture and biofilm phenotypes grown in bovine synovial fluid as a model system. Significant differences in metabolic pathways were found between the suspended culture and biofilm phenotypes including creatine, glutathione, alanine, and choline metabolism and the tricarboxylic acid cycle. We also identified 21 unique metabolites with the presence of P. aeruginosa in synovial fluid and one uniquely present with the biofilm phenotype in synovial fluid. If translatable in vivo, these unique metabolite and pathway differences have the potential for further development to serve as targets for P. aeruginosa and biofilm control in synovial fluid.

A deep learning framework for diagnosing periprosthetic joint infections using X-ray images: a discovery and validation study

BACKGROUND

X-ray examination is the first-line imaging test for periprosthetic joint infections (PJIs). Deep learning has the potential to improve the diagnostic performance of X-ray examination for PJIs.

METHODS

A deep learning framework was developed for PJI diagnosis based on 1,062 X-ray images of the index prosthesis from patients who had PJI or aseptic failure. The classification network was constructed based on an ensemble of four deep learning models in a two-channel format for dual-view X-ray images. The interpret network was developed based on gradient weighted class to generate disease probability maps of individual PJI risk. The discrimination performance and disease probability maps were estimated in the validation set.

RESULTS

This PJI deep learning technique achieved an area under the curve (AUC) of 0.913 (95% confidence interval [CI]: 0.840-0.948), sensitivity of 0.844 (95% CI: 0.768-0.861), and specificity of 0.882 (95% CI: 0.851-0.934) for PJI recognition in hip prostheses. The PJI deep learning technique achieved an AUC of 0.931 (95% CI: 0.893-0.978), sensitivity of 0.905 (95% CI: 0.806-0.942), and specificity of 0.889 (95% CI: 0.747-0.944) for PJI recognition in knee prostheses. The high-risk prosthetic regions predicted by PJI deep learning were closely tracked with intraoperative clinical and pathological findings.

CONCLUSIONS

Deep learning provided a clinically applicable strategy for diagnosing PJI with high accuracy and robustness using routinely available X-ray images. However, the finding should be considered preliminary, the diagnosis performance might be partially attributed to prosthesis loosening, and the deep learning method is only helpful in patients already deemed suitable for revision.

A role for artificial intelligence in molecular imaging of infection and inflammation

The detection of occult infections and low-grade inflammation in clinical practice remains challenging and much depending on readers’ expertise. Although molecular imaging, like [¹⁸F]FDG PET or radiolabeled leukocyte scintigraphy, offers quantitative and reproducible whole body data on inflammatory responses its interpretation is limited to visual analysis. This often leads to delayed diagnosis and treatment, as well as untapped areas of potential application. Artificial intelligence (AI) offers innovative approaches to mine the wealth of imaging data and has led to disruptive breakthroughs in other medical domains already. Here, we discuss how AI-based tools can improve the detection sensitivity of molecular imaging in infection and inflammation but also how AI might push the data analysis beyond current application toward predicting outcome and long-term risk assessment.

Diagnostic Performance of Advanced Metal Artifact Reduction MRI for Periprosthetic Shoulder Infection

BACKGROUND

The diagnosis of periprosthetic shoulder infection (PSI) in patients with a painful arthroplasty is challenging. Magnetic resonance imaging (MRI) may be helpful, but shoulder implant-induced metal artifacts degrade conventional MRI. Advanced metal artifact reduction (MARS) improves the visibility of periprosthetic bone and soft tissues. The purpose of our study was to determine the reliability, repeatability, and diagnostic performance of advanced MARS-MRI findings for diagnosing PSI.

METHODS

Between January 2015 and December 2019, we enrolled consecutive patients suspected of having PSI at our academic hospital. All 89 participants had at least 1-year clinical follow-up and underwent standardized clinical, radiographic, and laboratory evaluations and advanced MARS-MRI. Two fellowship-trained musculoskeletal radiologists retrospectively evaluated the advanced MARS-MRI studies for findings associated with PSI in a blinded and independent fashion. Both readers repeated their evaluations after a 2-month interval. Interreader reliability and intrareader repeatability were assessed with κ coefficients. The diagnostic performance of advanced MARS-MRI for PSI was quantified using sensitivity, specificity, and the area under the receiver operating characteristic curve (AUC). When applying the International Consensus Meeting (ICM) 2018 criteria, of the 89 participants, 22 (25%) were deemed as being infected and 67 (75%) were classified as being not infected (unlikely to have PSA and not requiring a surgical procedure during 1-year follow-up).

RESULTS

The interreader reliability and intrareader repeatability of advanced MARS-MRI findings, including lymphadenopathy, joint effusion, synovitis, extra-articular fluid collection, a sinus tract, rotator cuff muscle edema, and periprosthetic bone resorption, were good (κ = 0.61 to 0.80) to excellent (κ > 0.80). Lymphadenopathy, complex joint effusion, and edematous synovitis had sensitivities of >85%, specificities of >90%, odds ratios of >3.6, and AUC values of >0.90 for diagnosing PSI. The presence of all 3 findings together yielded a PSI probability of >99%, per logistic regression analysis.

CONCLUSIONS

Our study shows the clinical utility of advanced MARS-MRI for diagnosing PSI when using the ICM 2018 criteria as the reference standard. Although the reliability and diagnostic accuracy were high, these conclusions are based on our specific advanced MARS-MRI protocol interpreted by experienced musculoskeletal radiologists. Investigations with larger sample sizes are needed to confirm these results.

LEVEL OF EVIDENCE

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

Fluorodeoxyglucose PET/Computed Tomography in Evaluation of Prosthetic Joints and Diabetic Foot: A Comparative Perspective with Other Functional Imaging Modalities

Infection imaging has been an important part of nuclear medicine practice. Infections in prosthetic joints and diabetic foot are associated with devastating complications, posing substantial challenge for both diagnosis and overall management. For many years, conventional nuclear medicine techniques have been used to frame a painful joint arthroplasty or diabetic foot infection. The various functional nuclear imaging modalities used include labeled leukocyte imaging, combined leukocyte-marrow scintigraphy, antigranulocyte antibody scintigraphy, 3-phase bone scintigraphy, and fluorodeoxyglucose PET/computed tomography, yet no single method has proved to be highly sensitive and specific and at the same time safe, simple, and time-effective.

Posttreatment Changes of the Elbow

Radiologists should be familiar with the typical surgical procedures applied at the elbow and aware of the spectrum of normal and pathologic appearances of posttreatment situations throughout all radiologic modalities. Most important in the case of posttraumatic surgical elbow procedures is correct postoperative elbow joint alignment, appropriate fixation of joint-forming fragments, and proper insertion of screws, plates, and anchor devices that do not conflict with intra-articular or bony structures. To report soft tissue repair procedures correctly, radiologists need to know the broad spectrum of different techniques applied and their appearance on magnetic resonance imaging.

A Systematic Review and Meta-Analysis on the Accuracy of Fluorodeoxyglucose Positron Emission Tomography/ Computerized Tomography for Diagnosing Periprosthetic Joint Infections

Objective

Fluorodeoxyglucose Positron emission tomography/computerized tomography (FDG PET/CT) has become popular for diagnosing periprosthetic joint infections (PJI). However, the diagnostic accuracy for this technique has varied from report to report. This meta-analysis was performed to assess the accuracy of FDG PET/CT for PJI diagnosis.

Material and Methods

We conducted a systematic search of online academic databases for all studies reporting the diagnostic accuracy of FDG PET/CT for PJI. Meta-analysis was performed using STATA software.

Results

23 studies, containing data on 1,437 patients, met inclusion criteria. Pooled sensitivity and specificity of FDG PET/CT for diagnosing PJI were 85% (95% CI, 76%, 91%) and 86% (95% CI, 78%, 91%), respectively with an AUC of 0.92. LRP was 6.1 (95% CI, 3.8, 9.7) and LRN was 0.17 (0.11, 0.28), indicating that FDG PET/CT cannot be used for confirmation or exclusion of PJI. There was significant inter-study heterogeneity, but no significant publication bias was noted.

Conclusions

Our study found that FDG PET/CT has an important role as a diagnostic tool for PJI with high sensitivity and specificity. Further studies exploring its accuracy in different PJI locations remain necessary.

Lymphopenia in patients affected by SARS-CoV-2 infection is caused by margination of lymphocytes in large bowel: an [18F]FDG PET/CT study

BACKGROUND

To investigate the cause of lymphopenia in patients with newly diagnosed COVID-19, we measured [¹⁸F]FDG uptake in several tissues, including the ileum, right colon, and caecum at diagnosis and after recovery and correlated these measurements with haematological parameters.

METHODS

We studied, by [¹⁸F]FDG PET/CT, 18 newly diagnosed patients with COVID-19. Regions of interest were drawn over major organs and in the terminal ileum, caecum, and right colon, where the bowel wall was evaluable. Five patients were re-examined after recovery, and three of them also performed a white blood cell scan with ^99mTc-HMPAO-WBC on both occasions. Complete blood count was performed on both occasions, and peripheral blood lymphocyte subsets were measured at diagnosis. Data were analysed by a statistician.

RESULTS

Patients had moderate severity COVID-19 syndrome. Basal [¹⁸F]FDG PET/CT showed focal lung uptake corresponding to hyperdense areas at CT. We also found high spleen, ileal, caecal, and colonic activity as compared to 18 control subjects. At recovery, hypermetabolic tissues tended to normalize, but activity in the caecum remained higher than in controls. Regression analyses showed an inverse correlation between CD4 + lymphocytes and [¹⁸F]FDG uptake in the caecum and colon and a direct correlation between CD8 + lymphocytes and [¹⁸F]FDG uptake in lungs and bone marrow. WBC scans showed the presence of leukocytes in the caecum and colon that disappeared at recovery.

CONCLUSIONS

These findings indicate that lymphopenia in COVID-19 patients is associated with large bowel inflammation supporting the hypothesis that CD4 + lymphocytes migrate to peripheral lymphoid tissues in the bowel.

Diagnosis of prosthetic joint infection at the hip using the standard uptake value of three-phase 99mTc-hydroxymethylene diphosphonate SPECT/CT

PURPOSE

To retrospectively investigate whether the standard uptake value (SUV) of 99mTc-bone single-photon emission computed tomography (SPECT)/CT could be useful for predicting prosthetic joint infection (PJI) at the hip.

PATIENTS AND METHODS

We analyzed the cases of 37 patients with a suspected PJI at the hip who underwent 99mTc-bone SPECT/CT and surgical intervention with pathological and bacterial examinations. We divided the cases into those with and those without a causative bacterium detected in a surgical specimen, i.e., the positive bacterial culture (PBC) group (n = 17) and negative bacterial culture (NBC) group (n = 20). Cases with neutrophilic infiltration of surgical specimen comprised the positive neutrophilic infiltration (PINF) group (n = 18) and those without INF comprised the non-neutrophilic infiltration (NINF) group (n = 19). Quantitative analyses were performed using maximum SUVs and peak SUVs of blood-pool (BP) phase images (SUVmaxBP and SUVpeakBP) and late (LT)-phase images (SUVmaxLT and SUVpeakLT).

RESULTS

Regarding the bacterial cultures, there were significant differences between the PBC and NBC groups in SUVmaxBP (5.26 ± 1.49 vs. 4.21 ± 1.15, respectively; p = 0.019), SUVpeakBP (4.89 ± 1.32 vs. 3.87 ± 1.06, p = 0.012), SUVmaxLT (16.10 ± 6.36 vs. 11.67 ± 4.95, p = 0.026), and SUVpeakLT (14.58 ± 5.83 vs. 10.49 ± 4.31 p = 0.036). Regarding neutrophilic infiltration, there were significant differences between the PINF and NINF groups in SUVmaxBP (5.18 ± 1.48 vs. 4.24 ± 1.19, p = 0.047) and SUVpeakBP (4.78 ± 1.32 vs. 3.92 ± 1.10, p = 0.043).

CONCLUSION

An SUV analysis of 99mTc-bone SPECT/CT is a useful method to differentiate a PJI at the hip from non-infection.

Diagnostic Value of Advanced Metal Artifact Reduction Magnetic Resonance Imaging for Periprosthetic Joint Infection

MATERIALS AND METHODS

Magnetic resonance imaging around metal joint prostheses including multiacquisition variable-resonance image combination selective at 1.5 T (from April 2014 to August 2020) was retrospectively evaluated by 2 radiologists for detection of abnormal findings (joint effusion, capsular thickening, pericapsular edema, soft-tissue fluid collection, soft-tissue edema, bone marrow edema pattern around the implant [BME pattern], lymphadenopathy, and others) and overall image impression for PJI. Regarding the soft-tissue fluid collection, presence of communication to the joint or capsular-like structure was evaluated. Clinical assessments were recorded. Positive predictive values (PPVs), negative predictive values (NPVs), and odds ratios (ORs) for PJI were calculated for the abnormal findings. Overall image impression for PJI was evaluated. χ2, Fisher exact, t, and Mann-Whitney U tests and receiver operating characteristic analysis were used. Interobserver agreement was assessed with κ statistics.

RESULTS

Forty-three joints in 36 patients (mean ± SD age, 75.4 ± 8.8 years; 30 women; hip [n = 29], knee [n = 12], and elbow [n = 2]) were evaluated. Eighteen joints (42%) were clinically diagnosed as PJI. The findings suggesting PJI were capsular thickening (PPV, 70%; NPV, 90%; OR, 20.6), soft-tissue fluid collection (PPV, 81%; NPV, 81%; OR, 19.1), soft-tissue edema (PPV, 67%; NPV, 89%; OR, 17), pericapsular edema (PPV, 76%; NPV, 81%; OR, 13.7), and joint effusion (PPV, 55%; NPV, 100%; OR, 12). Soft-tissue fluid collection without capsular-like structure (PPV, 83%; NPV, 74%; OR, 14.4) or with communication to the joint (PPV, 75%; NPV, 71%; OR, 7.3) suggested PJI. The combinations of joint effusion, capsular thickening, pericapsular edema, soft-tissue fluid collection, and soft-tissue edema highly suggested PJI. Regarding the BME pattern, the combination with soft-tissue edema raised the possibility of PJI (PPV, 73%; NPV, 69%; OR, 5.9). Regarding the interobserver agreements for each abnormal finding, κ values were 0.60 to 0.77. Regarding the overall image impression, weighted κ value was 0.97 and areas under the receiver operating characteristic curve were 0.949 (95% confidence interval, 0.893-1.005) and 0.926 (95% confidence interval, 0.860-0.991) with no significant difference (P = 0.534).

CONCLUSIONS

The findings suggesting PJI were capsular thickening, soft-tissue fluid collection, soft-tissue edema, pericapsular edema, and joint effusion. The combinations of them highly suggested PJI. Regarding the BME pattern, the combination with soft-tissue edema raised the possibility of PJI.

The Role of Nuclear Medicine Imaging with 18F-FDG PET/CT, Combined 111In-WBC/99mTc-Nanocoll, and 99mTc-HDP SPECT/CT in the Evaluation of Patients with Chronic Problems after TKA or THA in a Prospective Study

Background: The aim of this prospective study was to assess the diagnostic value of nuclear imaging with ¹⁸F-FDG PET/CT (FDG PET/CT), combined ¹¹¹In-WBC/^99mTc-Nanocoll, and ^99mTc-HDP SPECT/CT (dual-isotope WBC/bone marrow scan) for patients with chronic problems related to knee or hip prostheses (TKA or THA) scheduled by a structured multidisciplinary algorithm. Materials and Methods: Fifty-five patients underwent imaging with ^99mTc–HDP SPECT/CT (bone scan), dual-isotope WBC/bone marrow scan, and FDG PET/CT. The final diagnosis of prosthetic joint infection (PJI) and/or loosening was based on the intraoperative findings and microbiological culture results and the clinical follow-up. Results: The diagnostic performance of dual-isotope WBC/bone marrow SPECT/CT for PJI showed a sensitivity of 100% (CI 0.74–1.00), a specificity of 97% (CI 0.82–1.00), and an accuracy of 98% (CI 0.88–1.00); for PET/CT, the sensitivity, specificity, and accuracy were 100% (CI 0.74–1.00), 71% (CI 0.56–0.90), and 79% (CI 0.68–0.93), respectively. Conclusions: In a standardized prospectively scheduled patient group, the results showed highly specific performance of combined dual-isotope WBC/bone marrow SPECT/CT in confirming chronic PJI. FDG PET/CT has an appropriate accuracy, but the utility of its use in the clinical diagnostic algorithm of suspected PJI needs further evidence.

99mTc-HMPAO-WBC SPECT/CT versus 18F-FDG-WBC PET/CT in chronic prosthetic joint infection: a pilot study

PURPOSE

The aim of this study was to compare 99mTc-HMPAO-WBC-SPECT/CT combined with 99mTc-nanocollloid SPECT/CT and 18F-FDG-WBC-PET/CT combined with 99mTc-Nanocollloid SPECT/CT for the diagnosis and treatment evaluation of chronic prosthetic joint infection (PJI).

METHODS

Patients with suspected chronic PJI were examined with 99mTc-HMPAO-WBC SPECT/CT, 18F-FDG-WBC PET/CT, and 99mTc-nanocolloid SPECT/CT (to visualize bone marrow). The location and patterns of uptake were noted and compared between the two leukocyte examinations. Both leukocyte examinations were evaluated visually for infection. The PET examinations were also evaluated semiquantitatively. Chronic PJI was verified clinically by microbial culture and successfully treated PJI was confirmed by 12 months symptom-free follow-up after cessation of antibiotics.

RESULTS

Nineteen patients were included with 10 hip prostheses and nine knee prostheses. Fourteen were diagnosed with chronic PJI and five with successfully treated PJI. The sensitivity of visual evaluation of 99mTc-WBC-HMPAO SPECT/CT for all joints was 0.31 and for 18F-FDG-WBC PET/CT 0.38. The specificity was 0.80 and 0.83, respectively. All patients with a true-positive SPECT examination had a false-negative PET examination and vice versa. Semiquantitative evaluation of the hips gave an area under the curve of 0.905 using the iliac crest as the background. Semiquantitative evaluation of the knees did not produce significant results.

CONCLUSION

This pilot study showed no difference in the sensitivity or specificity of 99mTc-HMPAO-WBC SPECT/CT and 18F-FDG-WBC PET/CT when combined with 99mTc-nanocollloid SPECT/CT in the diagnosis or treatment evaluation of suspected late chronic PJI.

Nuclear imaging does not have clear added value in patients with low a priori chance of periprosthetic joint infection. A retrospective single-center experience

Background: A low-grade periprosthetic joint infection (PJI) may present without specific symptoms, and its diagnosis remains a challenge. Three-phase bone scintigraphy (TPBS) and white blood cell (WBC) scintigraphy are incorporated into recently introduced diagnostic criteria for PJI, but their exact value in diagnosing low-grade PJI in patients with nonspecific symptoms remains unclear. Methods: In this retrospective study, we evaluated patients with a prosthetic joint of the hip or knee who underwent TPBS and/or WBC scintigraphy between 2009 and 2016 because of nonspecific symptoms. We reviewed and calculated diagnostic accuracy of the TPBS and/or WBC scintigraphy to diagnose or exclude PJI. PJI was defined based on multiple cultures obtained during revision surgery. In patients who did not undergo revision surgery, PJI was ruled out by clinical follow-up of at least 2 years absent of clinical signs of infection based on MSIS 2011 criteria. Results: A total of 373 patients were evaluated, including 340 TPBSs and 142 WBC scintigraphies. Thirteen patients (3.5 %) were diagnosed with a PJI. TPBS sensitivity, specificity, and positive and negative predictive values (PPV, NPV) were 71 %, 65 %, 8 % and 98 %, respectively. Thirty-five percent of TPBS showed increased uptake. Stratification for time intervals between the index arthroplasty and the onset of symptoms did not alter its diagnostic accuracy. WBC scintigraphy sensitivity, specificity, PPV and NPV were 30 %, 90 %, 25 % and 94 %, respectively. Conclusion: Nuclear imaging does not have clear added value in patients with low a priori chance of periprosthetic joint infection.

Classification and management options for prosthetic joint infection

Periprosthetic joint infection (PJI) is one of the major complications following arthroplasty implantation. Management of PJIs is a challenge for surgeons and various classification systems have been introduced, which consider variables such as onset of symptoms, pathogenesis and clinical manifestation. In an attempt to overcome the shortcomings which may limit their usefulness in borderline cases, a new classification system focusing on the topography of the infectious process has been proposed. This theory relies on the identification of the exact location of the bacterial colonization thus allowing to decide between a conservative or a more radical intervention irrespectively of the timing. The use of nuclear medicine device like radiolabelled white blood cells (WBC) scan could lead the path in identifying pathogenetic processes and their exact location thus guiding orthopaedic surgeons to the most appropriate diagnosis and treatment options. Currently management relies on debridement, antibiotics and implant retention (DAIR), which is traditionally performed at early stages, 1- or 2-stage revision arthroplasty which is commonly limited to chronic cases. Reports have demonstrated similar rates of infection recurrence following one and two-stage revisions, and the use of one-stage revision surgery is gaining popularity. More recently, satisfying results following partial implant retention during revision total arthroplasty for septic failures have been reported. In addition, in severe cases, definitive articulating antibiotic spacer, excision arthroplasty, arthrodesis or amputation can be performed.

Management of prosthetic joint infections: a guidelines comparison

BACKGROUND

In the last decade, the number of prosthetic joint replacements has been rising each year and this growing trend is related to the increased number of prosthetic joint infections (PJI). As PJI represent a devastating condition for the patient, physicians must identify the best treatment option for each case. Guidelines are not always clear regarding the most appropriate therapy pathway as they differ in many parameters.

MATERIALS AND METHODS

Aim of this article is to compare the different indications as reported by four major Academic Societies: the Infectious Disease Society of America, the American Academy of Orthopaedic Surgeons, and the Musculoskeletal Infection Society (MSIS) which published the guideline in partnership with the European Bone And Joint Infection Society.

CONCLUSIONS

PJI Guidelines differ in many parameters, therefore the choice of treatment for each case does not appear immediate; it would be desirable that, in the next few years, new scientific evidence will help clarify the indications of the most effective therapeutic protocols for PJI to determine the ultimate surgical strategy for every single patient.