The predictive value of indium-111 leukocyte scans in the diagnosis of infected total hip, knee, or resection arthroplasties

ACR Appropriateness Criteria® Imaging After Total Knee Arthroplasty: 2023 Update

Total knee arthroplasty is the most commonly performed joint replacement procedure in the United States. This manuscript will discuss the recommended imaging modalities for six clinical variants; 1. follow-up of symptomatic or asymptomatic patients with a total knee arthroplasty. Initial imaging, 2. Suspected infection after total knee arthroplasty. Additional imaging following radiographs, 3. Pain after total knee arthroplasty. Infection excluded. Suspect aseptic loosening or osteolysis or instability. Additional imaging following radiographs, 4. Pain after total knee arthroplasty. Suspect periprosthetic or hardware fracture. Additional imaging following radiographs, 5. Pain after total knee arthroplasty. Measuring component rotation. Additional imaging following radiographs, and 6. Pain after total knee arthroplasty. Suspect periprosthetic soft-tissue abnormality unrelated to infection, including quadriceps or patellar tendinopathy. Additional imaging following radiographs. The American College of Radiology 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 where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Nuclear Medicine Scans in Total Joint Replacement

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A 3-phase bone scan is a potential first-line nuclear medicine study for pain after total joint arthroplasty (TJA) when there is concern for periprosthetic joint infection or aseptic loosening.

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In patients who have a positive bone scintigraphy result and suspected infection of the joint, but where aspiration or other studies are inconclusive, labeled leukocyte scintigraphy with bone marrow imaging may be of benefit.

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Magnetic resonance imaging (MRI), while not a nuclear medicine study, also shows promise and has the advantage of providing information about the soft tissues around a total joint replacement.

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Radiotracer uptake patterns in scintigraphy are affected by the prosthesis (total knee arthroplasty [TKA] versus total hip arthroplasty [THA]) and the use of cement.

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Nuclear medicine scans may be ordered 1 year postoperatively but may have positive findings that are due to normal physiologic bone remodeling. Nuclear studies may be falsely positive for up to 2 years after TJA.

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Single-photon emission computed tomography (SPECT) combined with computed tomography (CT) (SPECT/CT), fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/CT, and MRI show promise; however, more studies are needed to better define their role in the diagnostic workup of pain after TJA.

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

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

Proceedings from the 2018 International Consensus Meeting on Orthopedic Infections: evaluation of periprosthetic shoulder infection

The Second International Consensus Meeting on Orthopedic Infections was held in Philadelphia, Pennsylvania, in July 2018. More than 800 experts from all 9 subspecialties of orthopedic surgery and allied fields of infectious disease, microbiology, and epidemiology were assembled to form the International Consensus Group. The shoulder workgroup reached consensus on 27 questions related to culture techniques, inflammatory markers, and diagnostic criteria used to evaluate patients for periprosthetic shoulder infection. This document contains the group's recommendations and rationale for each question related to evaluating periprosthetic shoulder infection.

Potential usefulness of 68Ga-citrate PET/CT in detecting infected lower limb prostheses

Background

Prosthetic joint infections may lead to failures of total joint arthroplasty. Radionuclide imaging can play a diagnostic role in identifying such infections, which require two-stage exchange arthroplasty (instead of simple revision surgery performed in non-infected cases). Although ¹⁸F-FDG PET/CT has emerged as a novel diagnostic tool in this setting, the clinical usefulness of ⁶⁸Ga-citrate PET/CT has not been previously investigated. This single-center prospective study was designed to address this issue.

Methods

Between January 2016 and October 2017, we examined 34 patients with clinically proven or suspected prosthetic hip/knee joint infections scheduled to undergo surgery. All patients underwent ⁶⁸Ga-citrate PET/CT scans and sequential ¹⁸F-FDG PET/CT imaging for comparative purposes. Intraoperative findings and the results of microbiological analyses of surgical specimens served as gold standard. The diagnostic results were examined according to (1) image interpretation based on radiotracer uptake patterns and (2) quantitative analysis using volumes of interest (VOIs) to calculate standard uptake values (SUVs) and metabolic volumes (MVs).

Results

A total of 26 (76%) patients were diagnosed as having infections. Based on radiotracer uptake pattern criteria, the sensitivity, specificity, and accuracy of ⁶⁸Ga-citrate PET/CT and ¹⁸F-FDG PET/CT were 92%, 88%, and 91% and 100%, 38%, and 85%, respectively. MV was significantly higher in the infected group when ⁶⁸Ga-citrate PET/CT was used (422.45 vs. 303.65 cm³, p = 0.027), whereas no significant differences were observed on ¹⁸F-FDG PET/CT. According to receiver operating characteristic (ROC) curve analysis, a cut-off value of 370.86 for MV resulted in a sensitivity of 61.5% and a specificity of 87.5% (area under curve: 0.75, 95% confidence interval: 0.57–0.88, p = 0.035).

Conclusions

Subject to future confirmation, our data provide preliminary evidence that ⁶⁸Ga-citrate PET/CT may have a complimentary role to ¹⁸F-FDG PET/CT in detecting prosthetic joint infections, being characterized by a higher specificity and the possibility to discriminate between an infectious condition and sterile inflammation.

Trial registration

This prospective study was registered at clinicaltrials.gov (registration number: NCT02855190).

What Markers Best Guide the Timing of Reimplantation in Two-stage Exchange Arthroplasty for PJI? A Systematic Review and Meta-analysis

BACKGROUND

There is no consensus on the appropriate marker to use when deciding to perform reimplantation after two-stage exchange arthroplasty for periprosthetic joint infection (PJI).

QUESTIONS/PURPOSES

What tests provide acceptable diagnostic value to guide appropriate timing of reimplantation in two-stage exchange arthroplasty for PJI?

METHODS

A search of online databases (MEDLINE, EMBASE, OVID, and Cochrane database) was performed containing articles that provided sensitivity and specificity values for accuracy for predicting reimplantation of the hip and/or knee. Twelve articles were included for final analysis, which included data from 1047 patients. Data that described the diagnostic accuracy of markers for reimplantation were evaluated and categorized into four main entities according to diagnostic method (serologic, synovial, tissue, and diagnostic imaging). Twelve parameters were examined, including serum erythrocyte sedimentation (ESR) rate, serum C-reactive protein (CRP), serum white blood cell (WBC) count, synovial fluid Gram stain, synovial fluid culture, synovial fluid sonication culture, synovial fluid WBC, synovial fluid polymorphonucleocyte percentage (PMN%), tissue Gram stain, tissue culture, positron emission tomography scan, and leukocyte scan. Each of the included articles was independently analyzed for risk of bias and applicability by using QUADAS-2. Statistical heterogeneity was calculated by using the Cochran Q test, and an α of 0.10 was considered significant for heterogeneity.

RESULTS

Tissue culture (sensitivity 0.82 [0.72-0.90], specificity 0.91 [0.89-0.95], diagnostic odds ratio (DOR) 46.87 [95% confidence interval {CI}, 22.03-99.69], synovial fluid PMN% (sensitivity 0.77 [0.46-0.95], specificity 0.74 [0.67-0.81], DOR 11.27 [95% CI, 2.89-43.61]), and synovial fluid culture (sensitivity 0.64 [0.52-0.74], specificity 0.96 [0.93-0.98], DOR 27.07 [95% CI, 2.55-288.00]) showed relatively high diagnostic performance. Other parameters had poorer diagnostic accuracy: ESR (sensitivity 0.56 [0.40-0.72], specificity 0.60 [0.53-0.66], DOR 2.41 [95% CI, 0.60-9.72), CRP (sensitivity 0.53 [0.39-0.67], specificity 0.72 [0.66-0.78], DOR 2.25 [95% CI, 0.09-4.63), and synovial fluid WBC count (sensitivity 0.37 [0.19-0.58], specificity 0.49 [0.41-0.57], DOR 0.94 [95% CI, 0.06-14.74). However, interpretation is limited, because only two to three studies were available for each pooled analysis. Both risks of bias and applicability concerns were low in the four domains assessed in QUADAS-2.

CONCLUSIONS

This meta-analysis suggests that no single marker was superior to all the others, and none (when used alone) is likely sufficient to confirm control of infection after the first stage of a two-stage protocol for PJI. Therefore, the current approach using multiple tools rather than a single marker is essential. Additionally, further studies must be conducted so that pooled analysis can be performed using multiple studies to determine ideal markers for reimplantation.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Two-Stage Reimplantation in Infected Total Knee Arthroplasty

Two-stage reimplantation is considered the gold standard for the management of periprosthetic joint infection. The first stage involves the removal of the prosthesis, followed by extensive debridement of all nonviable tissues, synovectomy, irrigation, and reaming of the medullary canals. Once the joint has been prepared, antibiotic-impregnated cement beads and/or spacer are inserted. Antibiotic-impregnated spacers are now more commonly used, and an increasing number of orthopaedic surgeons are using articulating spacers if indicated. Antibiotics are then prescribed to the patient based on the sensitivities of the infecting organism. The duration of systemic antibiotic use is decreasing, and short courses of antibiotic therapy have been shown to be as efficacious as prolonged therapy between the first and second stages. The second stage of the procedure involves removal of the antibiotic-impregnated cement beads and/or spacer, repeat irrigation and debridement, and final reconstruction with revision components. While two-stage reimplantation was considered the gold standard in many parts of the world, recent studies have demonstrated that it is associated with a considerable failure rate. This may be due to the lack of accurate diagnostic tools for infection eradication, and future investigation of risk factors for failure of the two-stage reimplantation should be conducted.

ACR Appropriateness Criteria® Imaging After Total Knee Arthroplasty

Total knee arthroplasty (TKA) is the most commonly performed joint replacement procedure in the United States and annual demand for primary TKA is expected to grow by 673% by 2030. The first part provides an overview of imaging modalities (radiographs, CT, MRI, ultrasound, and various nuclear medicine studies) and discusses their usefulness in the imaging evaluation of TKA. The second part focuses on evidence-based imaging and imaging-guided intervention algorithms for the workup of TKA and its complications, including routine follow-up, component wear, periprosthetic infection, aseptic loosening, granulomas/osteolysis, conventional and rotational instability, periprosthetic fracture, patellar complications, and a variety of periprosthetic soft tissue abnormalities. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Diagnosis of Periprosthetic Joint Infection-An Algorithm-Based Approach

BACKGROUND

Periprosthetic joint infection (PJI) remains one of the most challenging and devastating modes of failure after total hip and knee arthroplasties. Despite the profound urgency and impact of PJI on an individual and societal basis, historically, there have not been standardized definitions of and diagnostic algorithms for infection after total joint arthroplasty.

METHODS

In a recent symposium, the American Academy of Hip and Knee Surgeons put forth a standardized approach to the prevention, diagnosis, and management of the patient with a suspected PJI.

RESULTS

This review article summarizes these findings, and reviews the algorithmic approach to the diagnosis of PJI.

CONCLUSION

The diagnosis of PJI is easily made in our experience in 90% of patients by getting an erythrocyte sedimentation rate and C-reactive protein followed by selective aspiration of the joint if these values are elevated or if the clinical suspicion is high. Synovial fluid obtained should be sent for a synovial fluid white blood cell count, differential, and cultures.

An Articulating Antibiotic Cement Spacer for First-stage Reconstruction for Infected Total Elbow Arthroplasty

Management of an infected total elbow replacement is a significant clinical challenge. Although preservation of the prosthesis is ideal, a 2-stage revision is often necessary. Unlike lower limb arthroplasty, antibiotic spacers are not commercially available. Monoblock cement spacers do not allow elbow movements and are therefore associated with severe stiffness and scarring, leading to poor clinical outcomes. In our paper we present a simple and novel technique for constructing an articulating antibiotic-impregnated spacer for use as an implant for a 1-stage revision of an infected elbow arthroplasty.

What is the Accuracy of Nuclear Imaging in the Assessment of Periprosthetic Knee Infection? A Meta-analysis

BACKGROUND

In the assessment of possible periprosthetic knee infection, various imaging modalities are used without consensus regarding the most accurate technique.

QUESTIONS/PURPOSES

To perform a meta-analysis to compare the accuracy of various applied imaging modalities in the assessment of periprosthetic knee infection.

METHODS

A systematic review and meta-analysis was conducted with a comprehensive search of MEDLINE and Embase^® in accordance with the PRISMA and Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) recommendations to identify clinical studies in which periprosthetic knee infection was investigated with different imaging modalities. The sensitivity and specificity of each imaging technique were determined and compared with the results of microbiologic and histologic analyses, intraoperative findings, and clinical followup of more than 6 months. A total of 23 studies, published between 1990 and 2015, were included for meta-analysis, representing 1027 diagnostic images of symptomatic knee prostheses. Quality of the included studies showed low concerns regarding external validity, whereas internal validity indicated more concerns regarding the risk of bias. The most important concerns were found in the lack of uniform criteria for the diagnosis of a periprosthetic infection and the flow and timing of the included studies. Differences among techniques were tested at a probability less than 0.05 level. Where there was slight overlap of confidence intervals for two means, it is possible for the point estimates to be statistically different from one another at a probability less than 0.05. The z-test was used to statistically analyze differences in these situations.

RESULTS

Bone scintigraphy was less specific than all other modalities tested (56%; 95% CI, 0.47-0.64; p < 0.001), and leukocyte scintigraphy (77%; 95% CI, 0.69-0.85) was less specific than antigranulocyte scintigraphy (95%; 95% CI, 0.88-0.98; p < 0.001) or combined leukocyte and bone marrow scintigraphy (93%; 95% CI, 0.86-0.97; p < 0.001). Fluorodeoxyglucose positron emission tomography (FDG-PET) (84%; 95% CI, 0.76-0.90) was more specific than bone scintigraphy (56%; 95% CI, 0.47-0.64; p < 0.001), and less specific than antigranulocyte scintigraphy (95%; 95% CI, 0.88-0.98; p = 0.02) and combined leukocyte and bone marrow scintigraphy (93%; 95% CI, 0.86-0.97; p < 0.001). Leukocyte scintigraphy (88%; 95% CI, 0.81-0.93; p = 0.01) and antigranulocyte scintigraphy (90%; 95% CI, 0.78-0.96; p = 0.02) were more sensitive than FGD-PET (70%; 95% CI, 0.56-0.81). However, because of broad overlapping of confidence intervals, no differences in sensitivity were observed among the other modalities, including combined bone scintigraphy (93%; 95% CI, 0.85-0.98) or combined leukocyte and bone marrow scintigraphy (80%; 95% CI, 0.66-0.91; p > 0.05 for all paired comparisons).

CONCLUSIONS

Based on current evidence, antigranulocyte scintigraphy and combined leukocyte and bone marrow scintigraphy appear to be highly specific imaging modalities in confirming periprosthetic knee infection. Bone scintigraphy was a highly sensitive imaging technique but lacks the specificity needed to differentiate among various conditions that cause painful knee prostheses. FDG-PET may not be the preferred imaging modality because it is more expensive and not more effective in confirming periprosthetic knee infection.

LEVEL OF EVIDENCE

Level III, diagnostic study.

The Accuracy of Imaging Techniques in the Assessment of Periprosthetic Hip Infection: A Systematic Review and Meta-Analysis

BACKGROUND

Various imaging techniques are used for excluding or confirming periprosthetic hip infection, but there is no consensus regarding the most accurate technique. The objective of this study was to determine the accuracy of current imaging modalities in diagnosing periprosthetic hip infection.

METHODS

A systematic review and meta-analysis of the literature was conducted with a comprehensive search of MEDLINE and Embase to identify clinical studies in which periprosthetic hip infection was investigated with different imaging modalities. The sensitivity and specificity of each imaging technique were determined and compared with the results of microbiological and histological analysis, intraoperative findings, and clinical follow-up of >6 months.

RESULTS

A total of 31 studies, published between 1988 and 2014, were included for meta-analysis, representing 1,753 hip prostheses. Quality assessment of the included studies identified low concerns with regard to external validity but more concerns with regard to internal validity including risk of bias (>50% of studies had insufficient information). No meta-analysis was performed for radiography, ultrasonography, computed tomography, and magnetic resonance imaging because of insufficient available clinical data. The pooled sensitivity and specificity were 88% (95% confidence interval [CI], 81% to 94%) and 92% (95% CI, 88% to 96%), respectively, for leukocyte scintigraphy; 86% (95% CI, 80% to 90%) and 93% (95% CI, 90% to 95%) for fluorodeoxyglucose positron emission tomography (FDG PET); 69% (95% CI, 58% to 79%) and 96% (95% CI, 93% to 98%) for combined leukocyte and bone marrow scintigraphy; 84% (95% CI, 70% to 93%) and 75% (95% CI, 66% to 82%) for antigranulocyte scintigraphy; and 80% (95% CI, 72% to 86%) and 69% (95% CI, 64% to 73%) for bone scintigraphy.

CONCLUSIONS

Of the currently used imaging techniques, leukocyte scintigraphy has satisfactory accuracy in confirming or excluding periprosthetic hip infection. Although not significantly different, combined leukocyte and bone marrow scintigraphy was the most specific imaging technique. FDG PET has an appropriate accuracy in confirming or excluding periprosthetic hip infection, but may not yet be the preferred imaging modality because of limited availability and relatively higher cost.

LEVEL OF EVIDENCE

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

Two-stage management of the infected total hip arthroplasty

There is currently no consensus on the optimal management of the infected total hip arthroplasty. Multiple management techniques have been described in contemporary literature.This paper focuses on 2-stage revision for the infected total hip arthroplasty. We discuss the rationale and examine the current evidence for the use of this technique.

FDG PET Assessment of Osteomyelitis: A Review

This article discusses the role of [(18)F]Fluorodeoxyglucose (FDG) PET and PET/computed tomography in diagnosis and therapeutic response assessment for the management of patients with osteomyelitis, to increase awareness of imaging pitfalls and to improve understanding of specific technical and diagnostic challenges in patients with posttraumatic chronic osteomyelitis, spinal infections, prosthetic joint infections, and diabetic foot infections. This article focuses on the usefulness of modern imaging modalities in the setting of suspected infection or inflammation and on the role of FDG-PET in the management of patients with suspected or confirmed infection in the bones.

The Painful Total Knee Arthroplasty

There are many causes of residual pain after total knee arthroplasty (TKA). Evaluation and management begins with a comprehensive history and physical examination, followed by radiographic evaluation of the replaced and adjacent joints, as well as previous films of the replaced joint. Further workup includes laboratory analysis, along with a synovial fluid aspirate to evaluate the white blood cell count with differential as well as culture. Advanced imaging modalities may be beneficial when the diagnosis remains unclear. Revision surgery is not advisable without a clear diagnosis, as it may be associated with poor results.

The Diagnosis of Periprosthetic Joint Infection

Periprosthetic joint infection remains one of the most common failure modes following total hip and total knee arthroplasty. As such, a systematic and cost effective approach to the evaluation and work-up of a patient with a suspected periprosthetic joint infection should be undertaken in every patient with a painful total joint. Although we have many diagnostic tools, a history and physical remain the most important. Many of the current laboratory tests are indirect measure of infection, lack specificity for diagnosis of infection, but serve as sensitive and cost effective screening tools. In addition, a new definition of periprosthetic infection helps to standardize the diagnosis. Biomarkers hold the promise of improved specificity and are becoming increasingly popular as a diagnostic tool.

Diagnosis and Management of Periprosthetic Shoulder Infections

➤ The unique bacterial flora of the shoulder present diagnostic and treatment challenges that are distinct from those seen with failed hip and knee arthroplasties.➤ The presentation, diagnosis, and management of suppurative periprosthetic joint infections of the shoulder are similar to those of the hip and the knee.➤ Failed arthroplasties with positive cultures (FAPCs) are poorly performing shoulder reconstructions associated with low-virulence microorganisms that do not evoke a suppurative inflammatory response. Propionibacterium acnes is the predominant bacterium isolated from these cases.➤ With improved surgeon awareness and the addition of longer tissue-culture incubation times, detection of FAPCs has become more common. However, management is hampered by the lack of reliable, timely tests that can determine the presence of less virulent organisms in the preoperative or intraoperative settings.➤ The implications of positive culture results in FAPCs are unclear. Key test characteristics such as the false-positive rate and the prevalence of positive cultures in well-performing shoulders are unknown as there is no useful confirmatory test to validate the culture data and no reliable way to detect the presence of less virulent microorganisms without reoperation.➤ Soft-tissue and osseous deficits are frequently encountered when revising previously infected shoulders. The rate of complications in these scenarios is high, and the outcomes are the least favorable compared with revisions for any other indication.➤ The development of a consensus definition of a periprosthetic shoulder infection is critical to future investigations of these devastating complications.

Prosthetic joint infection

Prosthetic joint infection (PJI) is a tremendous burden for individual patients as well as the global health care industry. While a small minority of joint arthroplasties will become infected, appropriate recognition and management are critical to preserve or restore adequate function and prevent excess morbidity. In this review, we describe the reported risk factors for and clinical manifestations of PJI. We discuss the pathogenesis of PJI and the numerous microorganisms that can cause this devastating infection. The recently proposed consensus definitions of PJI and approaches to accurate diagnosis are reviewed in detail. An overview of the treatment and prevention of this challenging condition is provided.

The painful total hip replacement: diagnosis and deliverance

Total hip replacement (THR) is a very common procedure undertaken in up to 285 000 Americans each year. Patient satisfaction with THR is very high, with improvements in general health, quality of life, and function while at the same time very cost effective. Although the majority of patients have a high degree of satisfaction with their THR, 27% experience some discomfort, and up to 6% experience severe chronic pain. Although it can be difficult to diagnose the cause of the pain in these patients, this clinical issue should be approached systematically and thoroughly. A detailed history and clinical examination can often provide the correct diagnosis and guide the appropriate selection of investigations, which will then serve to confirm the clinical diagnosis made.

[SECOT consensus on painful knee replacement]

The opinions of 21 experts in knee surgery were evaluated in this study, using a DELPHI questionnaire method in two successive rounds, on 64 controversial scenarios that covered both the diagnosis and possible treatment of painful knee replacements. The level of consensus was significantly unanimous in 42 items and of the design in 5, with no agreement in 17 of the questions presented. light of the published scientific evidence, the surgeons who took part showed to have a notable level of information on the most effective diagnostic tests, although, it should be pointed out that there was a lack of confidence in the possibility of ruling out an infection when the erythrocyte sedimentation rate and the C-reactive protein were within normal values, which have been demonstrated in the literature to have a high negative predictive value As regards the treatments to employ in the different situations, the responses of the expert panel were mainly in agreement with the data in the literature. The conclusions of this consensus may help other surgeons when they are faced with a painful knee prosthesis.

Advances in the diagnosis of periprosthetic joint infection

INTRODUCTION

Identification of periprosthetic joint infection (PJI) is critical, as the treatment between infected and non-infected arthroplasties is fundamentally different and missing the diagnosis may lead to a delay in diagnosis and the potential for a decreased rate of treatment success. Yet in the absence of a true gold standard, the diagnosis of PJI can be elusive. Given the rising incidence of this PJI and the growing infection burden anticipated in coming years, much effort is being put toward improving diagnostic tests for PJI.

AREAS COVERED

The best current practice for diagnosis of PJI is to follow an algorithmic approach. Emerging technology such as advanced imaging modalities, increasing availability of serum markers, synovial fluid biomarker analysis and new point-of-care modalities offer the potential to greatly enhance our ability to identify PJI in the future.

EXPERT OPINION

As there has been more focus on the diagnosis of PJI in recent years, new tests have been developed. These new tests will need to be rigorously evaluated before being incorporated into the diagnostic algorithm. Synovial fluid biomarker analysis and greater access to point-of-care testing may allow the biggest improvements in the diagnosis of PJI in the near future.

The diagnostic protocol for evaluation of periprosthetic joint infection

Infection is becoming the most important as well as the most devastating mechanism of prosthetic joint failure. The incidence is increasing because the absolute number of patients operated is increasing and because more often very sick, debilitated and immunocompromised patients are operated. The trend reveals a further increase in the years to come. Diagnosis may be very easy in case of high grade processes, but also extremely difficult in some other instances. Misdiagnosing infection leads to repeated early failures that are distressing for patients as well as surgeons. To avoid failures related to misdiagnosed prosthetic joint infections a step-wise algorithm of action is proposed and the diagnostic strength of the steps discussed. The key point is to select potential candidates to define the probability of an ongoing infection and then to select the tools to strengthen the suspicion. Further procedures are based on the analysis of the pseudo-synovial fluid obtained by aspiration. Diagnostic conclusions form the basis for treatment decisions.

Prosthetic joint infections: radionuclide state-of-the-art imaging

Prosthetic joint replacement surgery is performed with increasing frequency. Overall the incidence of prosthetic joint infection (PJI) and subsequently prosthesis revision failure is estimated to be between 1 and 3%. Differentiating infection from aseptic mechanical loosening, which is the most common cause of prosthetic failure, is especially important because of different types of therapeutic management. Despite a thorough patient history, physical examination, multiple diagnostic tests and complex algorithms, differentiating PJI from aseptic loosening remains challenging. Among imaging modalities, radiographs are neither sensitive nor specific and cross-sectional imaging techniques, such as computed tomography and magnetic resonance imaging, are limited by hardware-induced artefacts. Radionuclide imaging reflects functional rather than anatomical changes and is not hampered by the presence of a metallic joint prosthesis. As a result scintigraphy is currently the modality of choice in the investigation of suspected PJI. Unfortunately, there is no true consensus about the gold standard technique since there are several drawbacks and limitations inherent to each modality. Bone scintigraphy (BS) is sensitive for identifying the failed joint replacement, but cannot differentiate between infection and aseptic loosening. Combined bone/gallium scintigraphy (BS/GS) offers modest improvement over BS alone for diagnosing PJI. However, due to a number of drawbacks, BS/GS has generally been superseded by other techniques but it still may have a role in neutropenic patients. Radiolabelled leucocyte scintigraphy remains the gold standard technique for diagnosing neutrophil-mediated processes. It seems to be that combined in vitro labelled leucocyte/bone marrow scintigraphy (LS/BMS), with an accuracy of about 90%, is currently the imaging modality of choice for diagnosing PJI. There are, however, significant limitations using in vitro labelled leucocytes and considerable effort has been devoted to developing alternative radiotracers, such as radiolabelled HIGs, liposomes, antigranulocyte antibodies and fragments, as well as more investigational tracers such as radiolabelled antibiotics, antimicrobial peptides, bacteriophages and thymidine kinase. On the other hand, positron emission tomography (PET) is still growing in the field of PJI imaging with radiotracers such as (18)F-fluorodeoxyglucose (FDG), (18)F-FDG white blood cells and (18)F-fluoride. But unfortunately this superb tomographic technique will only receive full acceptance when specific PET uptake patterns can be successfully developed. The emergence of hybrid modality imaging using integrated single photon emission computed tomography (SPECT) and PET with computed tomography (SPECT/CT and PET/CT) may also have a contributing role for more accurate assessment of joint replacement complications, especially combined with new radiotracers such as (68)Ga and (64)Cu. Finally, in searching for infection-specific tracers, currently there is no such diagnostic agent available.

Diagnosis of periprosthetic joint infections of the hip and knee

No preferred test for diagnosis of periprosthetic joint infection exists, and the algorithm for the workup of patients suspected of infection remains unclear. The work group evaluated the available literature to determine the role of each diagnostic modality and devise a practical algorithm that allows physicians to reach diagnosis of periprosthetic joint infection. Ten of the 15 recommendations have strong or moderate evidence in support. These include matters involving erythrocyte sedimentation rate and C-reactive protein level testing, knee and hip aspiration, and stopping the use of antibiotics prior to obtaining intra-articular cultures. The group recommends against the use of intraoperative Gram stain but does recommend the use of frozen sections of peri-implant tissues in reoperation patients in whom infection has not been established, as well as multiple cultures in reoperation patients being assessed for infection. The group recommends against initiating antibiotic treatment in patients with suspected infection until after joint cultures have been obtained, but recommends that prophylactic preoperative antibiotics not be withheld in patients at lower probability for infection.

Metal artifact reduction image reconstruction algorithm for CT of implanted metal orthopedic devices: a work in progress

INTRODUCTION

Despite recent advances in CT technology, metal orthopedic implants continue to cause significant artifacts on many CT exams, often obscuring diagnostic information. We performed this prospective study to evaluate the effectiveness of an experimental metal artifact reduction (MAR) image reconstruction program for CT.

MATERIALS AND METHODS

We examined image quality on CT exams performed in patients with hip arthroplasties as well as other types of implanted metal orthopedic devices. The exam raw data were reconstructed using two different methods, the standard filtered backprojection (FBP) program and the MAR program. Images were evaluated for quality of the metal-cement-bone interfaces, trabeculae < or = 1 cm from the metal, trabeculae 5 cm apart from the metal, streak artifact, and overall soft tissue detail. The Wilcoxon Rank Sum test was used to compare the image scores from the large and small prostheses. Interobserver agreement was calculated.

RESULTS

When all patients were grouped together, the MAR images showed mild to moderate improvement over the FBP images. However, when the cases were divided by implant size, the MAR images consistently received higher image quality scores than the FBP images for large metal implants (total hip prostheses). For small metal implants (screws, plates, staples), conversely, the MAR images received lower image quality scores than the FBP images due to blurring artifact. The difference of image scores for the large and small implants was significant (p = 0.002). Interobserver agreement was found to be high for all measures of image quality (k > 0.9).

CONCLUSION

The experimental MAR reconstruction algorithm significantly improved CT image quality for patients with large metal implants. However, the MAR algorithm introduced blurring artifact that reduced image quality with small metal implants.

(99m)Tc-Fab' fragments (sulesomab) for imaging septically loosened total knee arthroplasty

The diagnostic accuracy of infection scintigraphy with (99m)Tc-labelled monoclonal antibody Fab' fragments (sulesomab) was studied in patients with suspected total knee arthroplasty (TKA) infection. Images from 26 patients were evaluated by two independent readers and compared with a quantitative interpretation of time-activity courses. Microbiological examinations and joint aspiration results were used as reference standards. Histologically, aseptic TKA loosening occurred in two patients and severe, moderate or mild septic loosening in four, nine and 11 patients, respectively. Diagnostic accuracy for severe infection was 100% for both readers, whereas for moderate infection accuracy decreased by 12% and 12% for readers one and two, respectively. For mild infection a further decrease of approximately 61% and 52% occurred for readers one and two, respectively. Quantitative evaluation gave significantly better results over visual interpretation with a diagnostic accuracy of 100% for severe infection and decreased by only 10% and 15% in patients with moderate and mild infection, respectively. Quantitative evaluation of (99m)Tc-Fab' fragments is highly sensitive and specific for diagnostic imaging of infection in patients with septically-loosened TKA.

[Management of periprosthetic infection]

Periprosthetic infection is a permanent risk and severe complication in joint arthroplasty. Systematic diagnostics under optimal conditions are necessary for a successful therapy. Patient history, clinical examination and an elevated CRP-level is the basis for suspicion of infection. The diagnosis is confirmed by identification of the pathogen from a sample collected through joint aspiration under sterile conditions. The microbiological examination is done in a laboratory specialized in the diagnosis of foreign body infections. The pattern of resistance of the identified pathogen determines the topical and systemic course of antibiotics. Surgical treatment is characterized by exchange of the prosthesis and radical debridement. The exchange can be carried out in one or two stages. The one-stage exchange offers several advantages compared to two or more stage procedures for all those involved - patient, surgeon and health care system - while providing the same chance of successful elimination of infection, with even better functional results.

Role of modern imaging techniques for diagnosis of infection in the era of 18F-fluorodeoxyglucose positron emission tomography

During the past several years, it has become quite evident that positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) imaging can play a major role in the management of patients with suspected infection. Particularly, several groups have demonstrated that this powerful imaging methodology is very effective in the evaluation of osteomyelitis, infected prostheses, fever of unknown origin, and AIDS. In view of its extraordinary sensitivity in detecting disease activity and the ability to quantitate the degree of FDG uptake, PET might prove to be an appropriate modality for monitoring disease activity and evaluating response to therapy. FDG-PET has many advantages over existing imaging techniques for the diagnosis of infectious diseases. These include feasibility of securing diagnostic results within 1.5 to 2 h, excellent spatial resolution, and accurate anatomical localization of sites of abnormality. The availability of PET/computed tomography as a practical tool has further enhanced the role of metabolic imaging in many settings. In the future, this modality is very likely to be employed on a routine basis for detecting, characterizing, and monitoring patients with suspected and proven infection.

A simple, cost-effective screening protocol to rule out periprosthetic infection

The differential diagnosis of pain after total knee arthroplasty includes infection. Effective screening tools should have high sensitivity and are cost-effective. We evaluated 296 patients who underwent total knee revision at our institution. One hundred sixteen patients (39%) were classified as infected and 180 patients (61%) were considered noninfected. The mean erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) of the infected patients were 85 mm/h and 110 mg/L, respectively. The mean ESR and CRP of the noninfected patients were 22 mm/h and 7 mg/L, respectively. Five patients (4%) in the infected group had both normal ESR and CRP. Infection was suspected in all 5 patients, and an organism was cultured in 4 of the 5 cases. Erythrocyte sedimentation rate and CRP, when used in combination, serve as a useful screening tool in patients with a painful total knee arthroplasty.

Preoperative testing for sepsis before revision total knee arthroplasty

One hundred five consecutive painful knee arthroplasties were evaluated by a single surgeon for the presence of infection using a uniform protocol that included an erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), perioperative aspiration with synovial fluid white blood cell (WBC) count and differential, intraoperative frozen section analysis, and culture. A synovial fluid WBC count of greater than 3000 was the most precise test with a sensitivity of 100%, specificity of 98%, and accuracy of 99%. The preoperative use of an ESR and CRP proved to be an excellent screening modality with only one infection identified with both values being normal. A rational approach to perioperative testing for sepsis includes a screening ESR and CRP, and if elevated, aspiration with synovial fluid WBC count or an intraoperative frozen section.

Die Behandlung von periprothetischen Infektionen

Periprosthetic infections are severe complications following total joint arthroplasty. The infection rate is estimated to be 0.5-2%. Systemic diseases such as rheumatoid arthritis and previous surgery are considered risk factors for infection. The infection rate in the present patient cohort was low (0.72%). The recurrence rate (23.4%) is due to patients with rheumatoid arthritis and septic total knee arthroplasties. Successful treatment is dependent on various factors, one of which involves accurate preoperative bacterial diagnostics. Joint fluid aspiration is the appropriate procedure. Open biopsy or arthroscopically guided biopsy can be performed in cases of unclear diagnostic results. Early infection can be treated with thorough joint debridement without exchanging fixed implant components; "low-grade" or late infections require revision with implant removal in a one or two stage septic revision according to clearly determined algorithms. Antibiotic therapy is mandatory, and a combination with rifampicin is a very useful basis.

[Periprosthetic knee infection. One-stage exchange]

Systematic diagnostics and successful therapy of periprosthetic infection of the knee can only be achieved under optimal conditions. History, clinical examination and an elevated CRP level are the basis for suspicion of infection. Diagnosis is confirmed by identification of the pathogen through aspiration of the joint under sterile conditions. The microbiological examination is done in a laboratory, which is specialised in foreign body infections. Identification of the causing pathogens and their resistance pattern are essential to determine the topical and systemic course of antibiotics. When these conditions are fulfilled, the one-stage exchange procedure offers great advantages in comparison with procedures performed in two or more stages for all those involved--patients, surgeons and health care systems--while providing the same chance of a successful elimination of the infection, with an even better functional outcome. Currently, the treatment costs are not adequately reimbursed. In the future, prompt treatment of these especially unfortunate patients will only be possible, if the tremendous resources consumed by these patients are fully covered.

[Diagnostic strategies in cases of suspected periprosthetic infection of the knee. A review of the literature and current recommendations]

Reliable confirmation of periprosthetic infection after total knee arthroplasty is a diagnostic challenge. The present work reviews published data evaluating the available diagnostic tools. Erythrocyte sedimentation rate and C-reactive protein serum levels are relatively sensitive methods with rather low specificity towards periprosthetic infection and are mainly applied to exclude infection. Studies evaluating scintigraphic methods--especially white cell scans--provide inconsistent data with varying accuracy. Consequently, white cell scans cannot be recommended as standard methods. Immunoscintigraphy with antigranulocyte antibodies and FDG-PET scans demonstrated promising results with particularly high sensitivities, but have to be validated in larger studies. Microbiological evaluation of joint aspirates proved high specificity for periprosthetic infection. However, an average of 20% of infected cases remained undetected. Nevertheless, aspiration is widely recommended for preoperative isolation of the infecting organism. Intraoperative frozen sections demonstrated excellent specificity with good sensitivity. The real accuracy of intraoperative culture and permanent histology cannot be determined due to the missing golden standard; however, a combination of both methods is recommended to define the final diagnosis. Large studies validating both methods and criteria for the final diagnosis of periprosthetic infection are necessary to optimize the diagnostic algorithm.

Nuclear medicine imaging of bone infections

The inflammation and infection of bone include a wide range of processes that can result in a reduction of function or in the complete inability of patients. Apart from the inflammation, infection is sustained by pyogenic microorganisms and results mostly in massive destruction of bones and joints. The treatment of osteomyelitis requires long and expensive medical therapies and, sometimes, surgical resection for debridement of necrotic bone or to consolidate or substitute the compromised bones and joints. Radiographs and bone cultures are the mainstays for the diagnosis but often are useless in the diagnosis of activity or relapse of infection in the lengthy management of these patients. Imaging with radiopharmaceuticals, computed tomography and magnetic resonance are also used to study secondary and chronic infections and their diffusion to soft or deep tissues. The diagnosis is quite easy in acute osteomyelitis of long bones when the structure of bone is still intact. But most cases of osteomyelitis are subacute or chronic at the onset or become chronic during their evolution because of the frequent resistance to antibiotics. In chronic osteomyelitis the structure of bones is altered by fractures, surgical interventions and as a result of bone reabsorption produced by the infection. Metallic implants and prostheses produce artefacts both in computed tomography and magnetic resonance images, and radionuclide studies should be essential in these cases. Vertebral osteomyelitis is a specific entity that can be correctly diagnosed by computed tomography or magnetic resonance imaging at the onset of symptoms but only with radionuclide imaging is it possible to assess the activity of the disease after surgical stabilization or medical therapy. The lack of comparative studies showing the accuracy of each radiopharmaceutical for the study of bone infection does not allow the best nuclear medicine techniques to be chosen in an evidence-based manner. To this end we performed a meta-analysis of peer reviewed articles published between 1984 and 2004 describing the use of nuclear medicine imaging for the study of the most frequent causes of bone infections, including prosthetic joint, peripheric post-traumatic bone infections, vertebral and sternal infections. Guidelines for the choice of the optimal radiopharmaceuticals to be used in each clinical condition and for different aims is provided.

Evolving role of positron emission tomography in the management of patients with inflammatory and other benign disorders

Fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) has evolved from a research imaging modality assessing brain function in physiologic and pathologic states to a pure clinical necessity. It has been successfully used for diagnosing, staging, and monitoring a variety of malignancies. FDG-PET imaging also is evolving into a powerful imaging modality that can be effectively used for the diagnosis and monitoring of a certain nononcological diseases. PET has been shown to be very useful in the diagnosis of osteomyelitis, painful prostheses, sarcoidosis, fever of unknown etiology, and acquired immunodeficiency syndrome. Based on recent observations, several other disorders, such as environment-induced lung diseases, atherosclerosis, vasculitis, back pain, transplantation, and blood clot, can be successfully assessed with this technique. With the development and the introduction of several new PET radiotracers, it is expected that PET will secure a major role in the management of patients with inflammatory and other benign disorders.

Applications of fluorodeoxyglucose-PET imaging in the detection of infection and inflammation and other benign disorders

FDG-PET has great potential in the evaluation of a variety of inflammatory and infectious disorders and possibly other benign disorders. FDG-PET is very helpful in the evaluation of chronic osteomyelitis, sarcoidosis, FUO, and differentiating toxoplasmosis from lymphoma in the central nervous system in HIV-positive patients. The assessment of efficacy of FDG-PET in the evaluation of arthroplasty-associated infection, large-vessel vasculitis, and other inflammatory and infectious disorders is ongoing but seems quite promising at this time.

Periprosthetic sepsis

The diagnosis of septic implant failure can be difficult to make, yet is imperative for optimal patient outcomes in revision total hip arthroplasty. In most cases, a thorough history and physical examination combined with preoperative laboratory tests and an intraoperative frozen section are sufficient to differentiate septic from aseptic failure. If preoperative laboratory test values are elevated, preoperative aspiration of the hip can be used in selected patients to confirm or exclude the diagnosis of infection. Nuclear medicine studies comprise a second-line investigation to evaluate patients with a painful total hip arthroplasty in whom revision surgery otherwise is not indicated. Intraoperative tissue appearance in combination with intraoperative Gram stains are unreliable for detecting periprosthetic sepsis, and neither is adequate when considered alone for ruling out infection at the time of revision total hip arthroplasty. It is imperative that the surgeon doing revision total hip arthroplasty thoroughly understands the relative utility of preoperative and intraoperative tests used to diagnose periprosthetic sepsis.

Immunoscintigraphy of septic loosening of knee endoprosthesis: a retrospective evaluation of the antigranulocyte antibody BW 250/183

Immunoscintigraphy with the use of the antigranulocyte antibody BW 250/183 is a reliable method for detecting infection, especially in septic loosening of hip prostheses, for which purpose quantitative interpretation of the time-activity course is employed. Therefore, we retrospectively studied whether similar results could be achieved in knee prostheses. We verified 28 scintigraphic examinations in 26 patients by histology. Scintigraphy was performed during an early (4-6 h post injection) and a late phase (23-25 h post injection). Infection was diagnosed when activity around the knee prosthesis increased by more than 10% compared with bone marrow. We found a sensitivity and a negative predictive value of 100%, a specificity of 80%, a positive predictive value of 81% and an accuracy of 89%. Specificity and accuracy are lower than in the evaluation of hip prostheses; however, in comparison to other scintigraphic modalities, scintigraphy with the antigranulocyte antibody BW 250/183 is superior in excluding infection and has better specificity and accuracy. Therefore, as in the case of hip prostheses, the described methodology appears to be the scintigraphic modality of choice for knee prostheses.

The value of (18)FDG-PET for the detection of infected hip prosthesis

We compared the accuracy of fluorine-18 labelled 2-fluoro-2-deoxy- d-glucose positron emission tomography ((18)FDG PET) with that of technetium-99m hexamethylpropylene amine oxime leucocyte scintigraphy (LS) in the detection of infected hip prosthesis. Seventeen patients with a hip prosthesis suspected for infection were prospectively included and underwent (99m)Tc-methylene diphosphonate bone scintigraphy (BS), LS and an (18)FDG-PET scan within a 2-week period. Seven volunteers with ten asymptomatic hip prostheses were used as a control group and underwent BS and an (18)FDG-PET scan. Bacteriology of samples obtained by surgery or by needle aspiration and/or clinical follow-up for up to 6 months were used as the gold standard. Planar images of BS and LS (4 and 24 h p.i.) were acquired, followed by single-photon emission tomography (SPET) LS images (after 4 h). These images were scored as positive or negative by two experienced readers. The (18)FDG-PET scans of the patients were compared with the tracer distribution pattern in the asymptomatic control group and with BS. A phantom study was performed in order to identify artefacts. For this purpose, three different attenuation correction methods were tested. The combined analysis of the planar BS and LS resulted in a 75% sensitivity and a 78% specificity. The SPET LS images showed a better lesion contrast, resulting in an 88% sensitivity and a 100% specificity, while 24-h planar images were of no additional value. The analysis of PET images alone resulted in an 88% sensitivity and a 78% specificity. The combination of (18)FDG-PET and BS images resulted in an 88% sensitivity and a 67% specificity. Given the presence of small errors near the edge of the metal, which can induce significant artefacts in the corrected emission image, we decided to use the data without attenuation correction. In this preliminary study, (18)FDG-PET scans alone showed the same sensitivity as combined BS and LS, although the specificity was slightly lower.

Total knee arthroplasty after prior bone or joint sepsis about the knee

The current study was done to determine the effect of current methods to diagnose and treat infection on the incidence of deep prosthetic infection after total knee arthroplasty for patients with previous sepsis or osteomyelitis about the knee. Between 1989 and 1999, one surgeon did 20 consecutive primary total knee arthroplasties in 19 patients with a previous history of either septic arthritis or osteomyelitis about the knee. Antibiotic-impregnated cement was used in all patients. One patient was lost to followup and two patients died before 2 years from the arthroplasty. The remaining 16 patients were followed up for an average of 5 years (range, 2-11 years). There was one (5%) recurrent deep periprosthetic infection for which the patient required resection arthroplasty at 3.5 years. No patients required chronic antibiotic suppression. With careful preoperative and intraoperative evaluation and the routine use of antibiotic bone cement for fixation, total knee arthroplasty, in patients with prior bone or joint sepsis about the knee can provide good pain relief, functional improvement, and an acceptably low rate of deep prosthetic infection.