Use of F-18 fluoride PET to differentiate septic from aseptic loosening in total hip arthroplasty patients. Clin Nucl Med. 2011;36:e156-e161. [PMID: 21975412 DOI: 10.1097/rlu.0b013e3182291ae7]

Multifunctional Prosthesis Surface: Modification of Titanium with Cinnamaldehyde-Loaded Hierarchical Titanium Dioxide Nanotubes

Orthopedic prostheses are the ultimate therapeutic solution for various end-stage orthopedic conditions. However, aseptic loosening and pyogenic infections remain as primary complications associated with these devices. In this study, a hierarchical titanium dioxide (TiO2) nanotube drug delivery system loaded with cinnamaldehyde for the surface modification of titanium implants, is constructed. These specially designed dual-layer TiO2 nanotubes enhance material reactivity and provide an extensive drug-loading platform within a short time. The introduction of cinnamaldehyde enhances the bone integration performance of the scaffold (simultaneously promoting bone formation and inhibiting bone resorption), anti-inflammatory capacity, and antibacterial properties. In vitro experiments have demonstrated that this system promoted osteogenesis by upregulating both Wnt/β-catenin and MAPK signaling pathways. Furthermore, it inhibits osteoclast formation, suppresses macrophage-mediated inflammatory responses, and impedes the proliferation of Staphylococcus aureus and Escherichia coli. In vivo experiments shows that this material enhances bone integration in a rat model of femoral defects. In addition, it effectively enhances the antibacterial and anti-inflammatory properties in a subcutaneous implant in a rat model. This study provides a straightforward and highly effective surface modification strategy for orthopedic Ti implants.

PET/CT and SPECT/CT for Infection in Joints and Bones: An Overview and Future Directions

Infections of the bones and joints, if misdiagnosed, may result in serious morbidity and even mortality. A prompt diagnosis followed by appropriate management may reduce the socioeconomic impact of bone and joint infections. Morphologic imaging such as ultrasound and plain radiographs form the first line investigations, however, in early infections findings may be negative or nonspecific. Nuclear medicine imaging techniques play a complementary role to morphologic imaging in the diagnosis of bone and joint infections. The availability of hybrid systems (SPECT/CT, SPECT/MRI, PET/CT or PET/MRI) offers improved specificity with ability to assess the extent of infection. Bone scans are useful as a gatekeeper wherein negative scans rule out sepsis with a good accuracy, however positive scans are nondiagnostic and more specific tracers should be considered. These include the use of labeled white blood cells and antigranulocyte antibodies. Various qualitative and quantitative interpretation criteria have been suggested to improve the specificity of the scans. PET has better image resolution and 18F-FDG is the major tracer for PET imaging with applications in oncology and inflammatory/infective disorders. It has demonstrated improved sensitivity over the SPECT based tracers, however, still suffers from lack of specificity. 18F-FDG PET has been used to monitor therapy in bone and joint infections. Other less studied, noncommercialized SPECT and PET tracers such as 111In-Biotin, 99mTc-Ubiquicidin, 18F-Na-Fluoride, 18F-labeled white blood cells and 124I-Fialuridine to name a few have shown great promise, however, their role in various bone and joint infections has not been established. Hybrid imaging with PET or PET/MRI offers huge potential for improving diagnostics in infections of the joints and bones.

ACR Appropriateness Criteria® Imaging After Total Hip Arthroplasty

This article reviews evidence for performing various imaging studies in patients with total hip prostheses. Routine follow-up is generally performed with radiography. Radiographs are also usually the initial imaging modality for patients with symptoms related to the prosthesis. Following acute injury with pain, noncontrast CT may add information to radiographic examination regarding the presence and location of a fracture, component stability, and bone stock. Image-guided joint aspiration, noncontrast MRI, and white blood cell scan and sulfur colloid scan of the hip, are usually appropriate studies for patients suspected of having periprosthetic infection. For evaluation of component loosening, wear, and/or osteolysis, noncontrast CT or MRI are usually appropriate studies. Noncontrast MRI is usually appropriate for identifying adverse reaction to metal debris related to metal-on-metal articulations. For assessing patients after hip arthroplasty, who have trochanteric pain and nondiagnostic radiographs, ultrasound, or MRI are usually appropriate studies. 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.

Diagnostic accuracy of positron emission tomography/computerized tomography for periprosthetic joint infection of hip: systematic review and meta-analysis

BACKGROUND

American Academy of Orthopaedic Surgeons (AAOS) has provided the guidelines for diagnosing a patient with periprosthetic joint infection including the use of positron emission tomography/computed tomography (PET/CT). Systematic evidence focussing on periprosthetic joint infection (PJI) of hip is limited, which also contains limited number of studies. Hence, the current study aims to perform a pooled analysis of all studies that have assessed the diagnostic accuracy of PET/CT for PJI of hip.

METHODS

Searches were done in PubMed Central, EMBASE, MEDLINE, SCOPUS and Cochrane library until December 2022. Meta-analysis was carried out using random-effects model. With 95% confidence intervals (CIs), pooled sensitivity and specificity were reported.

RESULTS

Twenty-six studies met the inclusion criteria. The pooled sensitivity of PET/CT was 89% (95% CI 84-93%), while the pooled specificity was 86% (95% CI 79-91%). The AUROC was 0.94 (95% CI 0.72-0.99). There was statistically significant heterogeneity (p < 0.001) with I2 value of 96%. The diagnostic odds ratio was 52 (95% CI 26-106). Likelihood ratio positive was 6.5 (95% CI 4.1-10.3) and negative was 0.13 (95% CI 0.08-0.19).

CONCLUSION

Our study found that PET/CT was found to have higher level of accuracy in terms of sensitivity and specificity. Further large-scale research can help to find answers for such questions and provide final conclusive evidence on the inclusion of the imaging modality into the routine clinical practice guidelines for suspected periprosthetic joint infection patients.

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.

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.

Novel Musculoskeletal and Orthopedic Applications of 18F-Sodium Fluoride PET

PET imaging with ¹⁸F-sodium fluoride (NaF), combined with computed tomography or magnetic resonance, is a sensitive method of assessing bone turnover. Although NaF-PET is gaining popularity in detecting prostate cancer metastases to bone marrow, osseous changes represent secondary effects of cancer cell growth. PET tracers more appropriate for assessing prostate cancer metastases directly portray malignant activity and include ¹⁸F-fluciclovine and prostatic specific membrane antigen ligands. Recent studies investigating NaF-PET suggest utility in the assessment of benign musculoskeletal disorders. Emerging applications in assessing traumatic injuries, joint disease, back pain, orthopedic complications, and metabolic bone disease are discussed.

Diagnostic utility of fluorodeoxyglucose positron emission tomography in prosthetic joint infection based on MSIS criteria

AIMS

Prosthetic joint infection (PJI) and aseptic loosening in total hip arthroplasty (THA) can present with pain and osteolysis. The Musculoskeletal Infection Society (MSIS) has provided criteria for the diagnosis of PJI. The aim of our study was to analyze the utility of F18-fluorodeoxyglucose (FDG) positron emission tomography (PET) CT scan in the preoperative diagnosis of septic loosening in THA, based on the current MSIS definition of prosthetic joint infection.

PATIENTS AND METHODS

A total of 130 painful unilateral cemented THAs with a mean follow-up of 5.17 years (sd 1.12) were included in this prospective study. The mean patient age was 67.5 years (sd 4.85). Preoperative evaluation with inflammatory markers, aspiration, and an F18 FDG PET scan were performed. Diagnostic utility tests were also performed, based on the MSIS criteria for PJI and three samples positive on culture alone.

RESULTS

The mean erythrocyte sedimentation rate, C-reactive protein, and white cell count were 47.83 mm/hr, 25.21 mg/l, and 11.05 × 10⁹/l, respectively. The sensitivity, specificity, accuracy, negative predictive value, and false-positive rate of FDG PET compared with MSIS criteria were 94.87%, 38.46 %, 56.38%, 94.59 %, and 60.21%, respectively. The false-positive rate of FDG PET compared with culture alone was 77.4%.

CONCLUSION

FDG PET has a definitive role in the preoperative evaluation of suspected PJI. This the first study to evaluate its utility based on MSIS criteria and compare it with microbiology results alone. However, FDG PET has a high false-positive rate. Therefore, we suggest that F18 FDG PET is useful in confirming the absence of infection, but if positive, may not be confirmatory of PJI. Cite this article: Bone Joint J 2019;101-B:910-914.

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.

Molecularly specific detection of bacterial lipoteichoic acid for diagnosis of prosthetic joint infection of the bone

Discriminating sterile inflammation from infection, especially in cases of aseptic loosening versus an actual prosthetic joint infection, is challenging and has significant treatment implications. Our goal was to evaluate a novel human monoclonal antibody (mAb) probe directed against the Gram-positive bacterial surface molecule lipoteichoic acid (LTA). Specificity and affinity were assessed in vitro. We then radiolabeled the anti-LTA mAb and evaluated its effectiveness as a diagnostic imaging tool for detecting infection via immunoPET imaging in an in vivo mouse model of prosthetic joint infection (PJI). In vitro and ex vivo binding of the anti-LTA mAb to pathogenic bacteria was measured with Octet, ELISA, and flow cytometry. The in vivo PJI mouse model was assessed using traditional imaging modalities, including positron emission tomography (PET) with [¹⁸F]FDG and [¹⁸F]NaF as well as X-ray computed tomography (CT), before being evaluated with the zirconium-89-labeled antibody specific for LTA ([⁸⁹Zr]SAC55). The anti-LTA mAb exhibited specific binding in vitro to LTA-expressing bacteria. Results from imaging showed that our model could reliably simulate infection at the surgical site by bioluminescent imaging, conventional PET tracer imaging, and bone morphological changes by CT. One day following injection of both the radiolabeled anti-LTA and isotype control antibodies, the anti-LTA antibody demonstrated significantly greater (P < 0.05) uptake at S. aureus-infected prosthesis sites over either the same antibody at sterile prosthesis sites or of control non-specific antibody at infected prosthesis sites. Taken together, the radiolabeled anti-LTA mAb, [⁸⁹Zr]SAC55, may serve as a valuable diagnostic molecular imaging probe to help distinguish between sterile inflammation and infection in the setting of PJI. Future studies are needed to determine whether these findings will translate to human PJI.

A new imaging technique distinguishes bacterial infection at the site of joint implants from less-serious postoperative inflammation, saving patients from unnecessary and invasive treatments. Daniel Thorek of Johns Hopkins University School of Medicine and colleagues used an antibody that binds to lipoteichoic acid on the cell wall of Staphylococcus bacteria to detect infection at joint implant sites. The antibody was labeled with a radioactive agent and injected into mice that simulated infection of a knee replacement site. A PET scan conducted 1 day after antibody injection showed that it gathered at the infected joint significantly more than it did at the uninfected implant sites in other mice. This method could improve the diagnosis of joint implant infection, which necessitates removal of the prosthetic and all infected tissues, followed by prolonged antibiotic therapy.

Management of periprosthetic infections

Periprosthetic joint infection (PJI) is considered one of the most challenging complications compromising patient health and is considered an economic burden. Despite all strategies PJI prevalence is between 1%-2%. Considerable efforts have been investigated in the past decade to diminish or erradicate PJI prevalence. This article manages the definition of PJI and the new major and minor criteria from Parvizi et al Then a scientific analysis of every minor and major criteria. Multidisciplinary management is reccommended according to guidelines. A numerous of surgical options exist each and everyone with its indications, contraindications and specific antibiotic therapy regimen. Surgical options are: (1) irrigation and cleaning with retention of the prosthesis with a success rate 0%-89%; (2) single-stage revision surgery with a succes rate of > 80%; and (3) two-stage revision surgery (authors preferred method) with a succes rate of 87%. Radical treatment options like arthrodesis and amputation are reserved for specific group of patients, with a succes rate varying from 60%-100%. The future of PJI is focused on improving the diagnostic tools and to combat biofilm. The cornerstone of management consists in a rapid diagnosis and specific therapy. This article presents the most current diagnostic and treatment criteria as well as the different surgical treatment options depending on the type of infection, bacterial virulence and patient comorbidities.

Procalcitonin and α-Defensin for Diagnosis of Periprosthetic Joint Infections

BACKGROUND

Current methods to diagnose periprosthetic joint infection (PJI) before revision surgery have limited diagnostic accuracy. This meta-analysis was performed to estimate the accuracy of procalcitonin (PCT) and α-defensin for the diagnosis of PJI.

METHODS

Articles on the diagnostic value of PCT or α-defensin for PJI diagnosis were searched in the PubMed database. Sensitivity, specificity, diagnostic odds ratio, the area under the curve of summary receiver operating characteristic curves (AUC), the positive likelihood ratio, and the negative likelihood ratio were calculated to evaluate the diagnostic ability of PCT and the α-defensin test for the diagnosis of PJI.

RESULTS

The pooled sensitivities for detecting PJI using PCT and α-defensin were 0.53 (95% confidence interval [CI], 0.24-0.80) and 0.96 (95% CI, 0.85-0.99), respectively. The pooled specificities for detecting PJI using PCT and α-defensin were 0.92 (95% CI, 0.45-0.99) and 0.95 (95% CI, 0.89-0.98), respectively. The pooled diagnostic odds ratios for detecting PJI using PCT and α-defensin were 13 (95% CI, 3-70) and 496 (95% CI, 71-3456), respectively. The pooled AUCs for PCT and α-defensin were 0.76 (95% CI, 0.72-0.80) and 0.99 (95% CI, 0.97-0.99), respectively. The positive likelihood ratio and the negative likelihood ratio of PCT were 6.8 (95% CI, 1.0-48.1) and 0.51 (95% CI, 0.31-0.84), respectively, whereas those of α-defensin were 19.6 (95% CI, 8.2-46.8) and 0.04 (95% CI, 0.01-0.17), respectively.

CONCLUSION

Synovial fluid α-defensin has a great potential to diagnose PJI.

Designing a New Molecular Probe: The Potential Role for Tilmanocept (Lymphoseek®) in the Assessment of Patients with Painful Hip and Knee Joint Prostheses

BACKGROUND

There is a long history of nuclear medicine developments in orthopaedics beginning in the early 20th century. Technetium-99m (99mTc) has a short half-life of six hours, emits 140 keV gamma rays and is the most widely used isotope, imaged with the Anger (gamma) camera. Gamma image quality and test sensitivity in painful prosthetic joints can be improved with single photon emission computed tomography (SPECT) and SPECT/CT. Positron Emission Tomography-Computed Tomography (PET-CT) with Sodium Fluoride (18F-NaF) and 18Fluorine-fluorodeoxyglucose (18F-FDG) PET have promising and limited roles respectively in the investigation of painful prosthetic joints. New SPECT/CT and PET-CT isotopes targeting activated macrophages with 99mTc Tilmanocept (Lymphoseek®) and 68Gallium labelled Tilmanocept respectively show potential as agents to demonstrate wear particles ingested by macrophages and multinucleated giant cells. An imaging algorithm using SPECT and/or PET agents is proffered as a cost effective way of speedily and accurately arriving a diagnosis.

METHODS

Review of the historical role of nuclear medicine in orthopaedics and research into the potential role of new radiopharmaceutical agents was undertaken. Guidelines and algorithms for the imaging of complicated joint prosthesis are provided.

RESULTS

There is an established role for nuclear medicine in orthopaedics and particularly in the investigation of complicated joint prostheses. Imaging with Tilmanocept provides new opportunities to shorten the time to diagnose loosened and infected joint prostheses.

CONCLUSION

There is a potential new role for Tilmanocept, which can be utilised with both PET-CT and SPECT-CT technologies. Tilmanocept is a relatively new radiopharmaceutical which has a potential role in the imaging assessment of painful joint prosthesis.

Diagnosis of Periprosthetic Joint Infection Following Hip and Knee Arthroplasty

The diagnosis of periprosthetic joint infection (PJI) following total hip arthroplasty and total knee arthroplasty has been one of the major challenges in orthopedic surgery. As there is no single absolute test for diagnosis of PJI, diagnostic criteria for PJI have been proposed that include using several diagnostic modalities. Focused history, physical examination, plain radiographs, and initial serologic tests should be followed by joint aspiration and synovial analysis. Newer diagnostic techniques, such as alpha-defensin and interleukin-6, hold great promise in the future diagnosis of equivocal infections.

Comparative analysis of dual-phase 18F-fluoride PET/CT and three phase bone scintigraphy in the evaluation of septic (or painful) hip prostheses: A prospective study

BACKGROUND

The preoperative differentiation of aseptic and septic loosening of hip prostheses remains a diagnostic challenge for clinicians and many molecular imaging techniques have been evaluated. The objective of current study was to establish the clinical utility of dual phase 18F-fluoride PET/CT (DPFP) in diagnosing implant loosening, differentiation between septic and aseptic loosening and to compare the diagnostic accuracy of DPFP and three-phase bone scan (TPBS).

METHODS

In this prospective study, we evaluated 57 hip components in 45 patients (bilateral prostheses in 12 patients, 45 painful and 12 asymptomatic contralateral hip components) with dual phase fluoride PET/CT and TPBS. Findings of skeletal scintigraphy and PET/CT were evaluated by two expert nuclear medicine physicians, blinded with clinical findings and final diagnosis. The patterns of tracer uptake and maximum standardized uptake value (SUVmax) were noted for each joint. The final diagnosis was based on intraoperative findings, histopathological or microbiological examinations.

RESULTS

Out of twelve non-painful hips, DPFP correctly identified no loosening in 11 hips while TPBS detected in 10 hips. In the remaining 45 hips with radiological proven loosening to rule out sepsis, DPFP had a sensitivity, specificity, PPV, NPV and accuracy of 75%, 97%, 92%, 88% and 88% respectively while TPBS revealed 81%, 86%, 76%, 89% and 82% respectively. DPFP had shown a higher specificity and PPV as compared to the TPBS in the evaluation of painful hip prostheses. The pattern of tracer uptake may help in the differentiation between the two entities. We also noted a significant difference between SUVmax values of septic and aseptic loosening.

CONCLUSIONS

The results suggested that DPFP has considerable potential in differentiating septic from aseptic loosening of hip prostheses and more specific to rule out sepsis than TPBS. It may be employed before revision arthroplasty to evaluate implant for loosening and sepsis in loosened implant.

Sodium 18F-fluoride PET/CT of bone, joint, and other disorders

The use of (18)F-sodium fluoride ((18)F-NaF) with PET/CT is increasing. This resurgence of an old tracer has been fueled by several factors including superior diagnostic performance over standard (99m)Tc-based bone scintigraphy, growth in the availability of PET/CT imaging systems, increase in the number of regional commercial distribution centers for PET radiotracers, the recent concerns about potential recurring shortages with (99m)Tc-based radiotracers, and the recent decision by the Centers for Medicare and Medicaid Services to reimburse for (18)F-NaF PET/CT for evaluation of patients with known or suspected bone metastases through the National Oncologic PET Registry. The major goal of this article is to review the current evidence on the diagnostic utility of (18)F-NaF in the imaging assessment of the bone and joint in a variety of clinical conditions.

Review of the role of dynamic 18F-NaF PET in diagnosing and distinguishing between septic and aseptic loosening in hip prosthesis

Joint replacements may fail due to infection, dislocation, peri-prosthetic fracture and loosening. Between 0.4 and 4% of joint replacements are known to be complicated by infection and aseptic loosening 2–18%. Differentiating between infection and aseptic loosening has an important bearing on the ongoing strategy for antimicrobial therapy and surgical intervention, but distinguishing one from the other can be difficult and will often require a battery of clinical and biochemical tests including the use of varying radiological modalities to accurately identify whether problematic joints are infected or aseptically loose. Prompt diagnosis is important due to the development of a biofilm on the surface of the infected prosthesis, which makes treatment difficult. There is no consensus among experts on the ideal imaging technique nor the methodology for image interpretation, but there is an increasing trend to apply hybrid imaging in the investigation of painful joint prosthesis and recent attempts have been made using PET-CT to identify aseptic loosening and infection with ¹⁸F-fluorodeoxyglucose (FDG) and sodium fluoride ¹⁸F-Na. The aim of this paper is to evaluate the role of ¹⁸F-NaF sodium fluoride (¹⁸F-NaF) positron emission tomography (PET) in distinguishing between septic and aseptic failure in hip and knee replacements, in addition to evaluating the feasibility of using multi-sequential ¹⁸F-NaF PET-CT for the assessment of painful lower limb prostheses.

Metabolic Pattern of Asymptomatic Hip-Prosthesis by 18F-FDG-Positron-Emission-Tomography

Background:

Joint replacement is a procedure with a major impact on the quality of life of patients with joint degenerative disease or traumatic injuries. However, some patients develop symptoms after the intervention caused by mechanical loosening or infection. Metabolic imaging by 18F-FDG-PET investigated in these patients isoften hampered by low specificity for diagnosis of possible septic vs. mechanical loosening. The reason for this shortcoming is to our opinion the unawareness of physiological remodeling processes that could be seen in asymptomatic patients.

Objectives:

In order to overcome this drawback, we aimed to find out the physiological metabolic functional pattern in asymptomatic patients with implanted hip prosthesis

Patients and Methods:

Twelve patients (6 males, 6 females); mean age 73 ± 7 (range 58 - 91) years were prospectively enrolled in the study. The patients were admitted to our department for oncological referral with implanted hip prostheses. All patients explained no symptoms with regard to their implanted prosthesis. The attenuation corrected images were used for analysis.

Results:

Fourteen hip prostheses in 12 patients were visually analyzed. Seven out of 14 prostheses among 12 patients showed focal periprosthetic enhanced metabolism, two of which showed two sites of enhanced uptake; whereas, the remaining five prostheses showed singular hypermetabolic areas within the periprosthetic site. The remaining seven prostheses in the other five patients showed no periprosthetic-enhanced uptake.

Conclusion:

Of the asymptomatic patients investigated, 58% showed focal enhanced periprosthetic glucose metabolism. This finding should be taken into consideration as a more probable unspecific metabolic pattern for correct interpretation of 18F-FDG-PET studies in patients with suspected septic loosening of the hip prosthesis.

Comparative uptake of ¹⁸F-FEN-DPAZn2, ¹⁸F-FECH, ¹⁸F-fluoride, and ¹⁸F-FDG in fibrosarcoma and aseptic inflammation

The aim of this study is to evaluate uptake of 2-(18)F-fluoroethyl-bis(zinc(II)-dipicolylamine) ((18)F-FEN-DPAZn2) as a promising cell death imaging agent, a choline analog (18)F-fluoroethylcholine ((18)F-FECH), (18)F-fluoride as a bone imaging agent, and a glucose analog 2-(18)F-fluoro-2-deoxy-d-glucose ((18)F-FDG) in the combined S180 fibrosarcoma and turpentine-induced inflammation mice models. The results showed that (18)F-FDG had the highest tumor-to-blood uptake ratio and tumor-to-muscle ratio, and high inflammation-to-blood ratio and inflammation-to-muscle ratio. (18)F -FECH showed moderate tumor-to-blood ratio and tumor-to-muscle ratio, and low inflammation-to-blood ratio and inflammation-to-muscle ratio. However, accumulation of (18)F FEN-DPAZn2 in tumor was similar to that in normal muscle. Also, (18)F-FEN-DPAZn2 and (18)F-fluoride exhibited the best selectivity to inflammation. (18)F-FECH positron emission tomography (PET) imaging demonstrates some advantages over (18)F-FDG PET for the differentiation of tumor from inflammation. (18)F FEN-DPAZn2 and (18)F-fluoride can be used for PET imaging of aseptic inflammation.

18F sodium fluoride PET/CT detects osseous metastases from breast cancer missed on FDG PET/CT with marrow rebound

Intense FDG uptake by bone marrow following recent chemotherapy limits evaluation for osseous metastases. The impact of marrow rebound on accuracy of (18)F-fluoride PET/CT is unclear. A 73-year-old woman with breast cancer presented for restaging FDG PET/CT, which showed intense activity throughout almost the entire axial skeleton and no osseous metastases. An (18)F-fluoride PET/CT performed 7 days later identified multiple osseous metastases in the spine, ribs, and pelvis. This case demonstrates that (18)F-fluoride PET/CT should be considered for the evaluation of osseous metastases in patients with rebound marrow uptake on FDG PET/CT.

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.

18F-Fluoride PET/CT allows detection of hyperostosis and osseous involvement in meningioma: initial experience

PURPOSE

The present study was conducted to assess the diagnostic performance of (18)F-fluoride PET/CT in evaluating hyperostosis and osseous involvement in patients with meningioma.

PATIENTS AND METHODS

Thirty-four patients with meningioma (mean age, 61 years) underwent (18)F-fluoride PET/CT before surgery. In 24 patients (71%), (18)F-FDG PET/CT was also given before surgery, and the results were compared. The images were reviewed by 2 board-certified nuclear medicine specialists who were unaware of any clinical information and a consensus was reached. Uptake patterns and measurements of tracers were compared with pathological findings from resected specimens, with hyperostosis and osseous involvement as the reference standard.

RESULTS

There were 27 grade I tumors (79%) and 7 grade II tumors (21%). The primary tumor focus was identified in each patient using both (18)`F-fluoride PET/CT and (18)F-FDG PET/CT, but there were no significant correlations in the degree of uptake between the 2 tracers. The SUV(max), SUV(max) corrected for lean body mass (SUL(max)), and tumor metabolic volume (TMV) for (18)F-fluoride and (18)F-FDG were greater in grade II tumors than in grade I tumors. Hyperostosis and osseous involvement was identified in 12 tumors (38%). The SUV(max), SUL(max), and TMV of tumors visualized with (18)F-fluoride PET/CT were greater in tumors with hyperostosis and osseous involvement than in those without (P = 0.005, P = 0.003, and P = 0.006, respectively). In contrast, the SUV(max), SUL(max), and TMV of tumors visualized with (18)F-FDG PET/CT were similar regardless of hyperostosis or osseous involvement.

CONCLUSIONS

(18)F-fluoride PET/CT may improve detection of hyperostosis and osseous involvement in patients with meningioma.

A comparative uptake study of multiplexed PET tracers in mice with turpentine-induced inflammation

The potential value of multiplexed positron emission tomography (PET) tracers in mice with turpentine-induced inflammation was evaluated and compared with 2-[¹⁸F]fluoro-2-deoxy-D-glucose ([¹⁸F]FDG) for glucose metabolism imaging. These PET tracers included [¹⁸F]fluoromethylcholine ([¹⁸F]FCH) for choline metabolism imaging, (S-[¹¹C]methyl)-D-cysteine ([¹¹C]DMCYS) for amino acid metabolism imaging, [¹¹C]bis(zinc(II)-dipicolylamine) ([¹¹C]DPA-Zn²⁺) for apoptosis imaging, 2-(4-N-[¹¹C]-methylaminophenyl)-6-hydroxybenzothiazole ([¹¹C]PIB) for β amyloid binding imaging, and [¹⁸F]fluoride (¹⁸F⁻) for bone metabolism imaging. In mice with turpentine-induced inflammation mice, the biodistribution of all the tracers mentioned above at 5, 15, 30, 45, and 60 min postinjection was determined. Also, the time-course curves of the tracer uptake ratios for inflammatory thigh muscle (IM) to normal uninflammatory thigh muscle (NM), IM to blood (BL), IM to brain (BR), and IM to liver (LI) were acquired, respectively. Moreover, PET imaging with the tracers within 60 min postinjection on a clinical PET/CT scanner was also conducted. [¹⁸F]FDG and ¹⁸F⁻ showed relatively higher uptake ratios for IM to NM, IM to BL, IM to BR, and IM to LI than [¹⁸F]FCH, [¹¹C]DPA-Zn²⁺, [¹¹C]DMCYS and [¹¹C]PIB, which were highly consistent with the results delineated in PET images. The results demonstrate that ¹⁸F⁻ seems to be a potential PET tracer for inflammation imaging. [¹⁸F]FCH and [¹¹C]DMCYS, with lower accumulation in inflammatory tissue than [¹⁸F]FDG, are not good PET tracers for inflammation imaging. As a promising inflammatory tracer, the chemical structure of [¹¹C]DPA-Zn²⁺ needs to be further optimized.

Periprosthetic Joint Infection: What is on the Horizon?

Periprosthetic joint infection (PJI) will emerge as one of the most important issues for both orthopedic surgeons and researchers active in the field over the coming decades. Although the rate of PJI has not changed significantly over the past decade, the affected patients (hosts) being treated often present with more comorbidities than in the past, and the organisms responsible for these infections are evolving to become more difficult to treat. Fortunately, though, major strides in basic, translational, and clinical research have occurred in recent years that have armed the clinician with an armamentarium of techniques and technologies to better diagnose, prevent, and treat PJI. Advances in diagnostics, including refinements in established biomarkers, the introduction of point of service tests, developments in molecular techniques, and new techniques in advanced imaging will allow us to correctly identify the infecting pathogens and their virulence factors. Utilizing developed risk indexes to stratify and medically optimize our patients, modifying implants to incorporate antimicrobial and anti-biofilm properties, and developing clinically applicable vaccines and biofilm inhibiting enzymes will address our struggles in preventing PJI. Success of our future treatment strategies will hinge on refining the indications and technique of our current surgical procedures as well as the rational use of biofilm disrupting technologies and photodynamic therapy. Finally, the field of metabolomics, though still relatively in its infancy, likely holds the key to a novel diagnostic and treatment approach to infection and a more profound understanding of the pathophysiology of PJI on the human body.

(18)F NaF PET/CT Versus Conventional Bone Scanning in the Assessment of Benign Bone Disease

Nuclear physicians in many centers nowadays have the choice of using different nuclear bone-imaging modalities. (18)F-labeled sodium fluoride (NaF) PET with computed tomography (PET/CT) is a promising tool for the evaluation of benign bone disease. The indications for NaF PET/CT in clinical practice are probably the same as those established for (99m)Tc-labeled methylene diphosphonate bone scintigraphy and single-photon emission computed tomography (SPECT)/CT. At present only preliminary data, often with a limited number of patients and lacking comparison with (99m)Tc-MDP SPECT/CT, are available. This article reviews the available literature and summarizes the authors' experience with NaF PET/CT in benign bone disease.

Promising Roles of PET in Management of Arthroplasty-Associated Infection

A number of diagnostic tests is often necessary to differentiate aseptic loosening from periprosthetic infection in most clinical settings. The accuracy of [(18)F]Fluorodeoxyglucose examined with positron emission tomography imaging (FDG PET) in diagnosing periprosthetic infection has been determined by a number of investigations. In general, Images are considered positive for infection if they demonstrate increased FDG activity at the bone-prosthesis interface of the prostheses. Based on the large number of reports in the literature the sensitivity and specificity for FDG PET are about 85-90%. The overall accuracy of this non-invasive imaging modality is superior to the other existing imaging techniques. Therefore, FDG PET appears a very promising and accurate diagnosing tool for distinguishing septic from aseptic painful hip prostheses.

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.