Nuclear medicine and the failed joint replacement: Past, present, and future

Dual-Energy Computed Tomography Iodine Maps: Application in the Diagnosis of Periprosthetic Joint Infection in Total Hip Arthroplasty

BACKGROUND

The challenge of early and rapid diagnosis of periprosthetic joint infection (PJI) remains important. This study aimed to assess the efficacy of dual-energy computed tomography (DECT) iodine maps for diagnosing PJI in total hip arthroplasty.

METHODS

We prospectively enrolled 68 patients who had postoperative joint pain after hip arthroplasty. All patients underwent preoperative DECT iodine imaging to quantify iodine concentration (IC) in periprosthetic tissues during arterial and venous phases. The diagnostic efficacy of DECT iodine maps was evaluated by constructing receiver operating characteristic curves according to the Musculoskeletal Infection Society criteria.

RESULTS

Compared with erythrocyte sedimentation rate (area under the curve [AUC] = 0.837), polymorphonuclear cell percentage (AUC = 0.703), and C-reactive protein (AUC = 0.837), periprosthetic tissue venous-phase IC (AUC = 0.970) and arterial-phase IC (AUC = 0.964) exhibited outstanding discriminative capability between PJI and aseptic failure. The PJI cut-off point was venous IC = 1.225 mg/mL, with a sensitivity of 92.31% and specificity of 90.48%; for arterial IC = 1.065 mg/mL, the sensitivity was 96.15% and specificity was 90.70%.

CONCLUSIONS

This study demonstrates the great potential of DECT iodine maps for the diagnosis of PJI around hip arthroplasty, which helps to differentiate between periprosthetic infection and aseptic failure after hip arthroplasty.

SPECT/CT of Total Ankle Arthroplasty

Use of SPECT/CT (Single Photon Emission Computed Tomography/Computed Tomography) is increasing providing additional information in patients with inconclusive clinical examination and unremarkable imaging findings presenting with chronic pain after total ankle arthroplasty. To differentiate the cause of pain after total ankle arthroplasty can be challenging. SPECT/CT combines structural and metabolic imaging as a hybrid tool leading to higher specificity and overall diagnostic accuracy presumably in cases of gutter impingement, prosthetic loosening, and osteoarthritis of adjacent joints. Moreover, SPECT/CT can complement diagnostic work up in periprosthetic joint infections. Basal tracer enhancement has to be considered for the interpretation of imaging findings.

Is 18F-fluoride PET/CT an Accurate Tool to Diagnose Loosening After Total Joint Arthroplasty?

BACKGROUND

Several studies using positron emission tomography (PET) show highly elevated periprosthetic bone uptake of fluorine-18 sodium fluoride (18F-fluoride), suggestive of implant loosening after arthroplasty. Focus so far has been on qualitative but not on quantitative assessment. There is also a lack of intraoperative confirmation of preoperative 18F-fluoride PET findings. Although the method seems to have acceptable accuracy and high sensitivity, an attempt to improve the specificity and an overall validation of the method appear warranted.

QUESTIONS/PURPOSES

(1) Is there a difference in 18F-fluoride uptake around loose versus well-fixed THA and TKA components? (2) Can 18F-fluoride uptake measures provide a threshold that differentiates loose from well-fixed implants undergoing revision for a variety of septic and aseptic indications? (3) In a population restricted to THA and TKA undergoing revision for aseptic indications, can measurement of 18F-fluoride uptake still distinguish loose from well-fixed components? (4) What is the interrater reliability of measuring 18F-fluoride uptake?

METHODS

This was a retrospective assessment of a diagnostic test, 18F-fluoride PET/CT, which was performed prior to revision surgery. We included 63 patients with 31 THAs and 32 TKAs. Sixty-five percent of patients were female, and the mean age at 18F-fluoride PET/CT was 66 years. The THA had different modes of fixation (cemented, cementless, and hybrid; 45%, 32%, and 23%, respectively), whereas all TKAs were cemented. Imaging was conducted using routine protocols 1 hour after tracer injection. The interobserver reproducibility was analyzed using Spearman rank correlations and Bland-Altman analyses. Two independent observers were trained separately by a nuclear physician to measure maximal periprosthetic standardized uptake values (SUVmax) for each arthroplasty component (n = 126). Findings at surgery (whether the components were well fixed or loose, as well as the presence or absence of infection) were used as a reference. Presence of periprosthetic joint infection was retrospectively determined based on the criteria suggested by the European Bone and Joint Infection Society (EBJIS): clinical features in combination with blood analysis, synovial fluid cytologic analysis, and microbiology test results. Receiver operating characteristic (ROC) curves were plotted to assess the area under the curve (AUC) for each investigated component separately, indicating suitable SUVmax thresholds that differentiate loose from well-fixed components. After excluding patients with confirmed or suspected PJI per the EBJIS criteria (n = 12), the above analysis was repeated for the remaining patients with aseptic loosening (n = 51).

RESULTS

We found higher 18F-fluoride uptake around loose versus well-fixed components in all but femoral TKA components (median [range] SUVmax for well-fixed versus loose THA cups 10 [7 to 30] versus 22 [6 to 64], difference of medians 12; p = 0.003; well-fixed versus loose TKA femoral components 14 [4 to 41] versus 19 [9 to 42], difference of medians 5; p = 0.38). We identified favorable ROC curves for all investigated components except femoral TKA components (THA cups AUC 0.81 [best threshold 13.9]; THA femoral stems AUC 0.9 [best threshold 17.3]; femoral TKA components AUC 0.6 [best threshold 14.3]; tibial TKA components AUC 0.83 [best threshold 15.8]). 18F-fluoride was even more accurate at diagnosing loosening when we limited the population to those patients believed not to have prosthetic joint infection (THA cups AUC 0.87 [best threshold 14.2]; THA femoral stems AUC 0.93 [best threshold 15.0]; femoral TKA components AUC 0.65 [best threshold 15.8]; tibial TKA components AUC 0.86 [best threshold 14.7]). We found strong interrater correlation when assessing SUVmax values, with Spearman ρ values ranging from 0.96 to 0.99 and Bland-Altman plots indicating excellent agreement between the two independent observers.

CONCLUSION

Measuring SUVmax after 18F-fluoride PET/CT is a useful adjunct in the diagnostic evaluation for suspected implant loosening after THA and TKA. The method appears to be both accurate and reliable in diagnosing implant loosening for all components except femoral TKA components. In a real-world mixed population with both low-grade infection and aseptic loosening, the method seems to be fairly easy to learn and helpful to subspecialized arthroplasty clinicians. When infection can be ruled out, the method probably performs even better. Further prospective studies are warranted to explore the reason why femoral TKA component loosening was more difficult to ascertain using this novel technique.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Management of Bone Loss in Revision Total Knee Arthroplasty: An International Consensus Symposium

The evaluation, classification, and treatment of significant bone loss after total knee arthroplasty (TKA) continue to be a complex and debated topic in revision TKA (rTKA). Despite the introduction of new evidence and innovative technologies aimed at addressing the approach and care of severe bone loss in rTKA, there is no single document that systematically incorporates these newer surgical approaches. Therefore, a comprehensive review of the treatment of severe bone loss in rTKA is necessary. The Stavros Niarchos Foundation Complex Joint Reconstruction Center Hospital for Special Surgery, dedicated to clinical care and research primarily in revision hip and knee replacement, convened a Management of Bone Loss in Revision TKA symposium on June 24, 2022. At this meeting, the 42 international invited experts were divided into groups; each group was assigned to discuss questions related to 1 of the 4 topics: (1) assessing preoperative workup and imaging, anticipated bone loss, classification system, and implant surveillance; (2) achieving durable fixation in the setting of significant bone loss in revision TKA; (3) managing patellar bone loss and the extensor mechanism in cases of severe bone loss; and (4) considering the use of complex modular replacement systems: hinges, distal femoral, and proximal tibial replacements. Each group came to consensus, when possible, based on an extensive literature review and interactive discussion on their group topic. This document reviews each these 4 areas, the consensus of each group, and directions for future research.

Application of Nuclear Medicine Techniques in Musculoskeletal Infection: Current Trends and Future Prospects

Nuclear medicine has become an indispensable discipline in the diagnosis and management of musculoskeletal infections. Radionuclide tests serve as a valuable diagnostic tool for patients suspected of having osteomyelitis, spondylodiscitis, or prosthetic joint infections. The choice of the most suitable imaging modality depends on various factors, including the affected area, potential extra osseous involvement, or the impact of previous bone/joint conditions. This review provides an update on the use of conventional radionuclide imaging tests and recent advancements in fusion imaging scans for the differential diagnosis of musculoskeletal infections. Furthermore, it examines the role of radionuclide scans in monitoring treatment responses and explores current trends in their application. We anticipate that this update will be of significant interest to internists, rheumatologists, radiologists, orthopedic surgeons, rehabilitation physicians, and other specialists involved in musculoskeletal pathology.

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.

SPECT/CT of Total Ankle Arthroplasty

Use of SPECT/CT (Single Photon Emission Computed Tomography/Computed Tomography) is increasing providing additional information in patients with inconclusive clinical examination and unremarkable imaging findings presenting with chronic pain after total ankle arthroplasty. To differentiate the cause of pain after total ankle arthroplasty can be challenging. SPECT/CT combines structural and metabolic imaging as a hybrid tool leading to higher specificity and overall diagnostic accuracy presumably in cases of gutter impingement, prosthetic loosening, and osteoarthritis of adjacent joints. Moreover, SPECT/CT can complement diagnostic work up in periprosthetic joint infections. Basal tracer enhancement has to be considered for the interpretation of imaging findings.

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.

Molecular Imaging of Periprosthetic Joint Infections

Infection is an infrequent complication of lower extremity prosthetic joint surgery. Approximately one third develop within 3 months (early), another third within 1 year (delayed), and the remainder more than 1 year (late) after surgery. The diagnosis of periprosthetic joint infection is not always straightforward. Pain, the most common symptom, is present in 90%-100% of patients. The presence of fever is more variable, ranging from less than 5% to more than 40% of patients with infection. Erythema and joint swelling are often present in acute infections, but are less common in chronic infections. Erythrocyte sedimentation rate, C-reactive protein and interleukin-6 levels are useful "rule out" tests, while peripheral blood leukocyte count and serum tumor necrosis factor α are not helpful. The diagnosis of periprosthetic joint infection often requires a combination of blood, synovial fluid, and tissue sample tests, as well as imaging. Plain radiographs lack sensitivity and specificity. Molecular imaging is useful for evaluating painful joint replacements. Bone scintigraphy is most useful as a screening test. If it is negative then infection and aseptic loosening are unlikely. Combined labeled leukocyte/bone marrow imaging is a very specific test for diagnosing lower extremity joint arthroplasty infection; sensitivity is more variable. Despite more than two decades of investigation, there still is no consensus on the value of ¹⁸F-FDG for diagnosing periprosthetic joint infection. Differing test probabilities, an inability to discriminate between infection and inflammation secondary to physiologic reactions, and lack of standardized interpretative criteria are obstacles to incorporating ¹⁸F-FDG into the routine diagnostic imaging workup of periprosthetic joint infection. Preliminary results for gallium-68 citrate, fluorine-18, and technetium-99m labeled antimicrobial fragments are encouraging but no large scale trials with these agents have been conducted. Limited data suggest that labeled leukocyte/bone marrow SPECT/CT and ¹⁸F-FDG-PET/CT are specific but not sensitive for diagnosing periprosthetic infection of shoulder arthroplasties. There are minimal data on molecular imaging for monitoring treatment response in periprosthetic infections.

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.

Application of 68Ga-citrate PET/CT for differentiating periprosthetic joint infection from aseptic loosening after joint replacement surgery

AIMS

We aimed to evaluate the utility of ⁶⁸Ga-citrate positron emission tomography (PET)/CT in the differentiation of periprosthetic joint infection (PJI) and aseptic loosening (AL), and compare it with ^99mTc-methylene bisphosphonates (^99mTc-MDP) bone scan.

METHODS

We studied 39 patients with suspected PJI or AL. These patients underwent ⁶⁸Ga-citrate PET/CT, ^99mTc-MDP three-phase bone scan and single-photon emission CT (SPECT)/CT. PET/CT was performed at ten minutes and 60 minutes after injection, respectively. Images were evaluated by three nuclear medicine doctors based on: 1) visual analysis of the three methods based on tracer uptake model, and PET images attenuation-corrected with CT and those not attenuation-corrected with CT were analyzed, respectively; and 2) semi-quantitative analysis of PET/CT: maximum standardized uptake value (SUVmax) of lesions, SUVmax of the lesion/SUVmean of the normal bone, and SUVmax of the lesion/SUVmean of the normal muscle. The final diagnosis was based on the clinical and intraoperative findings, and histopathological and microbiological examinations.

RESULTS

Overall, 23 and 16 patients were diagnosed with PJI and AL, respectively. The sensitivity and specificity of three-phase bone scan and SPECT/CT were 100% and 62.5%, 82.6%, and 100%, respectively. Attenuation correction (AC) at 60 minutes and non-AC at 60 minutes of PET/CT had the same highest sensitivity and specificity (91.3% and 100%), and AC at 60 minutes combined with SPECT/CT could improve the diagnostic efficiency (sensitivity = 95.7%). Diagnostic efficacy of the SUVmax was low (area under the curve (AUC) of ten minutes and 60 minutes was 0.814 and 0.806, respectively), and SUVmax of the lesion/SUVmean of the normal bone at 60 minutes was the best semi-quantitative parameter (AUC = 0.969).

CONCLUSION

⁶⁸Ga-citrate showed the potential to differentiate PJI from AL, and visual analysis based on uptake pattern of tracer was reliable. The visual analysis method of AC at 60 minutes, combined with ^99mTc-MDP SPECT/CT, could improve the sensitivity from 91.3% to 95.7%. In addition, a major limitation of our study was that it had a limited sample size, and more detailed studies with a larger sample size are warranted. Cite this article: Bone Joint Res 2022;11(6):398-408.

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.

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.

Enhancing Diagnostics in Orthopedic Infections

Accurate diagnosis of orthopedic infection is crucial in guiding both antimicrobial therapy and surgical management in order to optimize patient outcomes. A variety of microbiological and nonmicrobiological methods are used to establish the presence of a musculoskeletal infection. In this minireview, we examine traditional culture-based and newer molecular methodologies for pathogen detection, as well as systemic and localized assays to assess host response to maximize diagnostic yield.

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.

Bone and Joint Infections: The Role of Imaging in Tailoring Diagnosis to Improve Patients' Care

Imaging is needed for the diagnosis of bone and joint infections, determining the severity and extent of disease, planning biopsy, and monitoring the response to treatment. Some radiological features are pathognomonic of bone and joint infections for each modality used. However, imaging diagnosis of these infections is challenging because of several overlaps with non-infectious etiologies. Interventional radiology is generally needed to verify the diagnosis and to identify the microorganism involved in the infectious process through imaging-guided biopsy. This narrative review aims to summarize the radiological features of the commonest orthopedic infections, the indications and the limits of different modalities in the diagnostic strategy as well as to outline recent findings that may facilitate diagnosis.

Imaging update in arthroplasty

Imaging of metal implants has historically been difficult, regardless of the applied modality. The number of primary arthroplasties is increasing over the years. With it, we expect the number of symptomatic complications to increase as well. Acquiring accurate imaging for diagnosis and treatment planning for these cases is of paramount importance. Significant advancements have been made to reduce artifacts, leading to better imaging representation of arthroplasty. This review article would give a background on the current ways of imaging arthroplasty and metal implants, covering recent advances in imaging techniques.

Use of PET-CT in diagnostic workup of periprosthetic infection of hip and knee joints: significance in detecting additional infectious focus

Introduction

The diagnosis and management of periprosthetic knee and hip infections as well as the identification and management of possible additional infectious foci is of great importance for successful therapy. This study analyses the importance of ¹⁸F deoxyglucose PET-CT (PET-CT) in the identification of additional infectious focus and subsequent impact on management of periprosthetic infection (PPI).

Material and methods

A retrospective analysis of the clinical data and findings in the period from January 2008 to December 2018 was carried out. One hundred and four patients with in-hospital treatment due to PPI of a hip or knee joint were identified and included in this study. All patients underwent a standardized clinical examination and further surgical and antibiotic therapy. The reevaluation of performed PET-CTs was specifically carried out with regard to the local PPI or detection of secondary foci.

Results

PET-CT successfully verified the PPI in 84.2% of the patients. A total of 78 possible additional foci were detected in PET-CT in 56 (53.8%) of the examined patients. Predilection sites for possible secondary foci were joints (42.3%), pulmonary (15.4%), ear-nose-throat (15.4%), spine (11.5%), and the musculocutaneous tissues (11.5%). Fifty-four positive PET-CT findings were confirmed clinically with need of additional adequate treatment.

Conclusion

PET-CT is a valuable diagnostic tool to confirm periprosthetic joint infection. At the same time, the whole-body PET/CT may detect additional foci of infection with impact on subsequent treatment strategy. PET was of special value in detecting infections at distant locations far from the primary infected joint in significant number. These distant infection locations can be potential cause of a re-infection. This clearly reflects the need of their diagnosis.

Hip prosthetic loosening: A very personal review

Hip prosthetic loosening is often difficult to detect at an early stage, and there has been uncertainty for a long time as to when the loosening occurs and thus to the basic causes. By comparing different diagnostic methods, we found that loosening is best defined as prosthetic migration and measured by radiostereometric analysis. Convincing evidence indicates that poor interlock, poor bone quality, and resorption of a necrotic bone bed may initiate loosening during or shortly after surgery; this forms the basis of the theory of early loosening. Biomechanical factors do affect the subsequent progression of loosening, which may increase subclinically during a long period of time. Eventually, the loosening may be detected on standard radiographs and may be interpreted as late loosening but should to be interpreted as late detection of loosening. The theory of early loosening explains the rapid early migration, the development of periprosthetic osteolysis and granulomas, the causality between wear and loosening, and largely the epidemiology of clinical failure of hip prostheses. Aspects discussed are definition of loosening, the pattern of early migration, the choice of migration threshold, the current understanding of loosening, a less exothermic bone cement, cemented taper-slip stems, a new exciting computed tomography-based technique for simpler implant migration studies, and research suggestions.

Radiologic Mimics of Osteomyelitis and Septic Arthritis: A Pictorial Essay

Various imaging techniques may be employed in the investigation of suspected bone and joint infections. These include ultrasound, radiography, functional imaging such as positron emission tomography (PET) and nuclear scintigraphy, and cross-sectional imaging, including computed tomography (CT) and magnetic resonance imaging (MRI). The cross-sectional modalities represent the imaging workhorse in routine practice. The role of imaging also extends to include assessment of the anatomical extent of infection, potentially associated complications, and treatment response. The imaging appearances of bone and joint infections are heterogeneous and depend on the duration of infection, an individual patient's immune status, and virulence of culprit organisms. To add to the complexity of radiodiagnosis, one of the pitfalls of imaging musculoskeletal infection is the presence of other conditions that can share overlapping imaging features. This includes osteoarthritis, vasculopathy, inflammatory, and even neoplastic processes. Different pathologies may also coexist, for example, diabetic neuropathy and osteomyelitis. This pictorial review aims to highlight potential mimics of osteomyelitis and septic arthritis that are regularly encountered, with emphasis on specific imaging features that may aid the radiologist and clinician in distinguishing an infective from a noninfective aetiology.

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.

Initial results of the use of a novel semiquantitative parameter in three-phase bone scan to predict 99mTc-HMPAO-labeled leukocyte scintigraphy in patients with unilateral total knee replacement

OBJECTIVES

The aim of the study was to predict the results of 99mTc-hexamethylpropyleneamine oxime (HMPAO)-labeled autologous leukocytes scintigraphy assessing count ratios in the perfusion (Pr) and blood-pool (BPr) phase images in three-phase bone scan (3PBSr) between the prosthetic knee and the 'healthy' knee and a novel semiquantitative parameter (P/BP ratio) in patients with unilateral knee arthroplasty.

METHODS

Patients with unilateral knee arthroplasty and available 3PBS and 99mTc-HMPAO-labeled autologous leukocytes scintigraphic images were searched in two hospitals (A and B). In center A, the perfusion phase was not available. Regions of interest (ROI) were delineated in the perfusion (P) and blood-pool (BP) phase images, incorporating the prosthetic region and applying an isocontour (40% of the maximum pixel activity); corresponding mirror ROIs were placed on the healthy knee. The P/BP ratio was calculated as {[(Pr/BPr) × 100] - 100}. Receiver operator curves (ROCs) were generated for each semiquantitative parameter to identify the optimal cutoff for predicting the results of the autologous leukocytes scintigraphy.

RESULTS

In the whole group (79 patients), BPr demonstrated an area under the curve (AUC) of 0.722 (optimal cutoff = 1.43). In center A (52 patients), BPr demonstrated an AUC of 0.737 (cutoff = 1.43), whereas, in center B (27 patients), AUC for BPr was 0.718 (cutoff = 1.6). A better diagnostic performance was obtained selecting Pr (AUC = 0.918; cutoff = 2.34) and P/BP ratio (AUC = 0.947; cutoff = 26.5%) for the discrimination between septic and aseptic loosening.

CONCLUSIONS

The novel P/BP ratio seems to be a promising semiquantitative parameter to predict septic loosening. These findings warrant confirmation in larger patient samples.

The Role of Imaging Techniques to Define a Peri-Prosthetic Hip and Knee Joint Infection: Multidisciplinary Consensus Statements

Diagnosing a peri-prosthetic joint infection (PJI) remains challenging despite the availability of a variety of clinical signs, serum and synovial markers, imaging techniques, microbiological and histological findings. Moreover, the one and only true definition of PJI does not exist, which is reflected by the existence of at least six different definitions by independent societies. These definitions are composed of major and minor criteria for defining a PJI, but most of them do not include imaging techniques. This paper highlights the pros and cons of available imaging techniques—X-ray, ultrasound, computed tomography (CT), Magnetic Resonance Imaging (MRI), bone scintigraphy, white blood cell scintigraphy (WBC), anti-granulocyte scintigraphy, and fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT), discusses the added value of hybrid camera systems—single photon emission tomography/computed tomography (SPECT/CT), PET/CT and PET/MRI and reports consensus answers on important clinical questions that were discussed during the Third European Congress on Inflammation/Infection Imaging in Rome, December 2019.

Should scintigraphy be completely excluded from the diagnosis of periprosthetic joint infection?

AIM

To analyse the diagnostic performance of bone and leukocyte scintigraphy for periprosthetic joint infection before excluding the test from routine practice, and to analyse the possible benefit of bone marrow scintigraphy in inconclusive cases.

MATERIALS AND METHODS

From 2012 to 2018, all patients with a total hip or knee arthroplasty who had a bone and leukocyte scintigraphy performed and underwent revision surgery were included. Bone marrow scintigraphy was indicated only in cases in which bone and leukocyte scintigraphy were inconclusive. Diagnosis of periprosthetic joint infection was confirmed by positive intraoperative cultures after revision surgery.

RESULTS

A total of 105 patients were included. Eighteen patients had total hip arthroplasties (18.1%) and 86 had total knee arthroplasties (81.9%). Mean age was 74 years. Nineteen cases were diagnosed with a periprosthetic joint infection. Bone and leukocyte scintigraphy had 64% sensitivity and 97% specificity. Bone marrow scintigraphy increased sensitivity and specificity to 88% and 100%, respectively.

CONCLUSION

Bone and leukocyte scintigraphy possesses high sensitivity and specificity for the diagnosis of chronic periprosthetic joint infection. The additional use of bone marrow scintigraphy significantly increases diagnostic performance. For these reasons, bone scintigraphy is reserved for inconclusive cases of chronic periprosthetic joint infection.

Nuclear Medicine for the Orthopedic Foot and Ankle Surgeon

Nuclear medicine has been widely applied as a diagnostic tool for orthopedic foot and ankle pathology. Although its indications have diminished with improvements in and the availability of magnetic resonance imaging, nuclear medicine still has a significant and valuable role. The present article offers a comprehensive and current review of the most common nuclear imaging modalities for the orthopedic foot and ankle surgeon. Methods discussed include bone scintigraphy, gallium citrate scintigraphy, labeled-leukocyte scintigraphy, and single-photon emission computed tomography (SPECT). We review the indications and utility of these techniques as they pertain to specific foot and ankle conditions, including osteomyelitis, stress fractures, talar osteochondral lesions, complex regional pain syndrome, oncology, plantar fasciitis, and the painful total ankle arthroplasty. We conclude with a discussion of our approach to nuclear medicine with illustrative cases. Level of Evidence: Level V, expert opinion.

Role of 18F-flurodeoxyglucose in orthopaedic implant-related infection: review of literature and experience

Infection and inflammation are a common occurrence with orthopaedic procedures. Anatomical modalities can show the transformation in the disease process; however, these may occur later when compared with functional imaging modalities that are more likely to identify early disease patterns. Various molecular imaging modalities such as three-phase bone scintigraphy, labelled leucocyte scintigraphy, as well as radiolabelled antibiotics and immunoglobulins have been considered and have played key roles in assisting clinical decision-making. While 18F-flurodeoxyglucose (FDG) PET/computed tomography (CT) has been relatively well established in cancer pathways, it has the potential to contribute to surgical decision making for possible osteomyelitis post-metal implant surgery. In this article, we present a review of recently used tracers, and share our experience with using 18F-FDG PET/CT studies in a few diverse clinical settings related to post-metal implant osteomyelitis.

Evaluation of the Painful Total Knee Arthroplasty

Total knee arthroplasty (TKA) has been associated with notable improvements in health-related quality of life of patients with end-stage knee arthritis. Although most patients experience substantial symptomatic relief after TKA, up to 19% of patients are unsatisfied with their outcome. With the dramatic, projected increase in the number of TKAs performed annually, it is crucial to appreciate the various modes of failure associated with this procedure. A comprehensive understanding of the symptomatology and thorough clinical examination aid in identifying the etiology of ongoing knee pain. Ancillary testing including conventional laboratory analyses, imaging studies, and diagnostic injections supplement a thorough history and physical examination. In addition, novel laboratory markers, RNA/DNA-based tests, and novel imaging modalities are emerging as beneficial tools in evaluating patients with a painful TKA. A well-structured, algorithmic approach in the management of these patients is essential in correctly diagnosing the patient and optimizing clinical outcomes.

Detection of aseptic loosening in total knee replacements: a systematic review and meta-analysis

OBJECTIVE

The aim of this study was to compare the diagnostic accuracy of nuclear imaging modalities in the detection of aseptic loosening of total knee arthroplasty (TKA).

MATERIALS AND METHODS

MEDLINE, EMBASE, and the Cochrane Database of Systematic Reviews were searched from database inception to December 2018 in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Included studies compared the results of a single imaging modality against an appropriate reference standard of prosthetic TKA loosening, with sufficient information to determine either sensitivity and/or specificity. The methodological quality of the studies was assessed using the QUADAS-2 tool.

RESULTS

The search strategy identified 572 abstracts. Of these, 12 studies comprising 401 patients across four modalities (bone scintigraphy, 18F-FDG-PET, SPECT/CT arthrogram, radionuclide arthrogram) met the inclusion criteria. All included studies used operative findings, a period of clinical or radiographic observation or both as a reference standard for aseptic loosening. Sixteen comparisons with the reference standards were extracted. All studies were at risk of bias across patient selection, the index test, reference standard, and flow and timing of patients. The most accurate test for diagnosis of aseptic loosening in TKA was SPECT/CT arthrography demonstrated by the summary receiver operating characteristic curve.

CONCLUSIONS

The best available evidence suggests the most accurate modality for the detection of aseptic loosening in TKA is SPECT/CT arthrography. However, the available evidence has a high risk of bias, and total number of patients studied for each modality is small so further studies are warranted.

An Implantable Wireless Inductive Sensor System Designed to Monitor Prosthesis Motion in Total Joint Replacement Surgery

Currently, the most common method for detecting prosthetic implant loosening is imaging. Unfortunately, imaging methods are imprecise in detecting the early signs of implant loosening. This paper describes a new wireless inductive proximity sensor system for detecting early implant loosening. The loosening of the implant is accurately detected by analyzing the electromagnetic field generated by the passive sensors located around the implant. The sensor system was modeled and simulated using COMSOL, and then tested experimentally. The inductive proximity sensor and the metallic implant form a coupled circuit is tuned to oscillate at a designed frequency. The circuit's integrated controller measures and records specific sensor's parameters such as resistance and inductance of the sensor that are directly related to the distance between the sensor system and the implant. A prototype has been developed and the results show that the designed proximity sensor is capable of measuring the loosening of the hip implant at [Formula: see text]m resolution at distances of less than [Formula: see text], and of [Formula: see text]m resolution at a distance of [Formula: see text]. Furthermore, there is a good correlation between the simulated and experimental results.

What Is the Value of Component Loosening Assessment of a Preoperatively Obtained Bone Scan Prior to Revision Total Knee Arthroplasty?

BACKGROUND

Bone scintigraphy (BS) is frequently ordered to investigate cause of failure following total knee arthroplasty (TKA). Its correlation of component loosening with intraoperative findings (IFs) at the time of revision TKA (rTKA) has not been well studied. This study investigated correlations between the preoperatively obtained radiologist report (RR) of BS, preoperatively documented surgeon prediction (SP) of component loosening, and operative reports documenting IFs.

METHODS

Our institutional database was retrospectively reviewed for all rTKA done after BS and revealed 96 eligible cases. The RR and SP cohorts were subdivided into all potential combinations of component loosening and were then compared with each other as well as IF. In addition to calculating the percentage correct of RR and SP compared with IF, the levels of agreement between RR and SP were compared using the kappa statistic.

RESULTS

Of the 96 cases, the RR correctly correlated with IF in 35 cases (37%), whereas the SP was correct in 66 cases (69%), indicating the preoperative interpretation of the surgeon regarding component loosening at rTKA was correct more frequently (P < .001). The kappa statistic between RR and IF was only 0.23 (95% confidence interval [CI] = 0.15-0.32), indicating minimal agreement. The kappa statistic between SP and IF was 0.57 (95% = CI 0.46-0.68), indicating weak agreement. Furthermore, the kappa statistic between RR and SP was 0.36 (95% CI = 0.27-0.45), also indicating minimal agreement.

CONCLUSIONS

In rTKA, there is weak agreement regarding component loosening between a radiologist's opinion of a preoperatively obtained bone scan and the surgeon's preoperative interpretation of clinical and radiographic data. While neither reliably accurately predicts what is found at the time of rTKA, the surgeon's preoperative interpretation is more closely correlated with actual IFs of component loosening.

Radiological Imaging Evaluation of the Failing Total Hip Replacement

Total hip replacements (THR) have been performed in the UK from the 1960s and since then we have seen surgical techniques, the design of implants, and imaging modalities rapidly develop. This paper will aim to review the different complications and imaging appearance which help to evaluate each problem. As for all investigations for bone and joints, a radiograph is the first imaging to be performed for any patient with a THR and can detect a majority of complications. CT is relatively low-cost, simple to perform and easily available making it an excellent tool to supplement radiographs when trying to evaluate a hip prosthesis. Single photon emission computed tomography with CT (SPECT-CT) is an emerging modality which has shown to combine the sensitivity that bone scintigraphy offers with the high specificity of CT. SPECT imaging also has the advantage of showing the bone's metabolic activity and is less prone to metal artifact than Magnetic resonance imaging (MRI). MRI has evolved to become an important diagnostic tool for the evaluation of THR in the post-operative period. Optimized pulse sequences and metal artifact reduction techniques have made MRI a useful tool in diagnosis of soft tissue abnormalities and is particularly useful in identifying adverse local tissue reactions in metal on metal implants. CT and MRI are accurate in identifying the diagnosis of most causes of THR complications except infection. Research confirms that leukocyte-marrow scintigraphy is the modality of choice for accurately diagnosing prosthetic joint infection and reassures us of its superiority over other nuclear medicine imaging. However, due to the limited availability and increased costs when performing leukocyte-marrow scintigraphy, CT and SPECT-CT would be a more preferred option when suspecting prosthesis infection. Ultrasound (US) has a limited role in the assessment of most THR complications but can be useful to identify peri-prosthetic fluid collections and the presence of soft tissue sinus tracts. Being aware of the imaging modalities that are available to orthopedic surgeons, and discussing these challenging cases with specialist radiologists will enable optimal management of THR complications.

Complications of shoulder arthroplasty: added value of SPECT/CT imaging

The incidence of prosthetic shoulder replacements has increased considerably in recent years, as well as the complications derived from the procedure. The correct diagnosis of each type of complication is essential for therapeutic decision making, which is currently based on the information provided by radiological and nuclear medicine imaging. Nevertheless, both techniques have intrinsic limitations that could be mostly overcome with the advent of the hybrid SPECT/CT imaging, which is set to play a fundamental role in the evaluation of shoulder prostheses.

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

Background

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

Aim and Methods

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

Results and Conclusion

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

Electronic supplementary material

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

A new perspective on current prosthetic joint infection classifications: introducing topography as a key factor affecting treatment strategy

Periprosthetic joint infection (PJI) is a relatively frequent and devastating complication following prosthetic joint implantation. Several classification systems have been presented by various authors and are routinely used in clinical practice to help in early diagnosis and treatment. The most widely accepted classifications of periprosthetic infections rely on the timing of clinical presentation. Unfortunately, these schemes possess important shortcomings which limit their usefulness in clinical practice, as data reported in literature are contrasting, with success rate ranging from 60 to 80%, irrespectively of prosthetic infection timing. An attempt is made by us to update the current knowledge on PJIs by looking them from a different perspective, introducing a topographic principle in their classification. Our approach is based on the theory that identifying the exact location of the bacterial colonization may allow to decide whether to conservatively treat the patient or to perform a more radical intervention. The aim is to improve the understanding of the aetiology of this serious complication, lead to the appropriate treatment strategy according to the stage of the disease thus enhancing the outcomes of surgical management. Such a strategy, if widely accepted, could guide research studies on the management of PJIs. The availability of investigations like scintigraphy could aid in identifying pathogenetic processes and their exact location, which may be missed on conventional radiographs, and could enable orthopaedic surgeons to have a better understanding of PJI patterns.

In Vivo Molecular Imaging of Musculoskeletal Inflammation and Infection

In vivo molecular imaging detects biologic processes at molecular level and provides diagnostic information at an earlier time point during disease onset or repair. It offers definite advantage over anatomic imaging in terms of improved sensitivity and ability to quantify. Radionuclide molecular imaging has been widely used in clinical practice. This article discusses the role of radionuclide imaging in various infective and inflammatory diseases affecting musculoskeletal system with a focus on PET. It appears that, as more data become available, combined PET/MR imaging could emerge as a front runner in the imaging of musculoskeletal infection and inflammation.

SPECT/CT in the Postoperative Painful Knee

This review summarizes the role of SPECT/CT in patients with a painful postoperative knee and describes typical diagnostic criteria in these patients. Pain after knee surgery is common and is influenced by the underlying pathology, the type of surgery, and the patient. Knee joint-preserving surgery includes osteotomy, ligament reconstruction, meniscus surgery, and cartilage repair procedures, often used in combination. Knee arthroplasty procedures consist of unicondylar, patellofemoral, and primary or revision total knee prosthesis. In patients with pain after knee joint-preserving surgery, MRI remains the reference standard. After ligament reconstruction, CT can evaluate postoperative tunnel positioning, and bone SPECT/CT can contribute by assessing overloading or biodegradation problems. After meniscal or cartilage surgery, SPECT/CT can be particularly helpful to identify compartment overloading or nonhealing chondral or osteochondral lesions as cause of pain. SPECT/CT arthrography can assess cartilage damage at an early stage due to altered biomechanical forces. After corrective osteotomy of the knee, SPECT/CT can reveal complications such as overloading, nonunion, or patellofemoral problems. After arthroplasty, conventional radiographs lack both sensitivity to detect aseptic loosening and specificity in differentiating aseptic from infectious loosening. Secondly, hardware-induced artifacts still hamper CT and MRI, despite improving and increasingly available metal artifact reduction techniques. Bone scintigraphy is a proven useful adjunct to conventional radiography and MRI to reveal the pain generator and is less hampered by artifacts from metallic implants compared with CT and MRI. Nevertheless, the optimal imaging strategy in evaluating complications after knee arthroplasty is still a matter of debate. Although the evidence of the use of BS SPECT/CT is still limited, it is growing steadily. In particular, recent data on specific uptake patterns in tibial and femoral zones after total knee arthroplasty and the impact of integrating biomechanics into the assessment of SPECT/CT appear promising, but more research is needed.

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.

Tubercular prosthetic joint infection: two case reports and literature review

PURPOSE

Tubercular prosthetic joint infection (TB-PJI) is an uncommon complication. Lack of evidence of systemic tuberculosis and clinical suspicion could bring a delay in the time of the diagnosis. The aims of this study are to underline the importance of awareness and suspicion of mycobacterial infection in the differential diagnosis in PJI and to evaluate the appropriateness of different therapeutic options.

METHODS

Case report and literature review.

RESULTS

We report two cases of TB-PJI after total knee arthroplasty in Caucasian patients without prior history of tubercular disease or exposure. In both cases, the diagnosis was obtained years after the onset of symptoms. Despite that, both patients improved during antitubercular treatment (a four-drug regimen consisting of rifampicin, isoniazid, ethambutol, and pyrazinamide for 2 months, followed by rifampicin and isoniazid). Moreover, after an 18-month course of treatment, there was no need for surgical therapy. The result of the literature review allows us to identify 64 cases of TB-PJI. Many differences in both medical and surgical management have been found, among those reviewed cases.

CONCLUSIONS

Considering our experience and the literature review, we recommend considering a conservative approach (debridement and adequate antituberculous chemotherapy) as a suitable and safe option.

Role of Nuclear Medicine for Diagnosing Infection of Recently Implanted Lower Extremity Arthroplasties

Infection is an infrequent complication of lower extremity prosthetic joint surgery. Approximately one-third develop within 3 months (early), another third within 1 year (delayed), and the remainder more than 1 year (late) after surgery. Diagnosing prosthetic joint infection, especially in the early postoperative period during the first year, is challenging. Pain is almost always present. The presence of fever is variable, ranging from less than 5% to more than 40% of patients. Leukocytosis is a poor predictor of infection. After primary uncomplicated arthroplasty, the C-reactive protein remains elevated for up to 3 weeks. The erythrocyte sedimentation rate can remain elevated for up to 1 year. Although joint aspiration with culture, the definitive preoperative diagnostic procedure, is specific, its sensitivity is variable. Plain radiographs lack sensitivity and specificity. Radionuclide studies are useful for evaluating painful joint replacements, but data on their utility during the early postoperative period are limited. During the first year after arthroplasty insertion, the bone scan can exclude infection. It is a good "rule-out" test, but it is not reliable for "ruling in" infection. Gallium-67 accumulates in normally healing surgical incisions and in aseptic inflammation. With an accuracy of 60%-80% for diagnosing prosthetic joint infection, there is little role for this radiopharmaceutical for evaluating prosthetic joints, regardless of age. Although data about diagnosing prosthetic joint infection with ¹⁸F-FDG in the early postoperative period are lacking, uptake of this radiopharmaceutical in a variety of postoperative settings for variable time periods is well known. Furthermore, its utility for diagnosing prosthetic joint infection in general, after nearly 2 decades of investigation, remains to be established. Indium-111-labeled leukocytes do not accumulate in normally healing surgical wounds, and in combination with marrow imaging, the test is about 90% accurate for diagnosing prosthetic joint infection. Preliminary data indicate a comparable accuracy in the early postoperative period.