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

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.

Semi-quantitative analysis with 99mTc-Besilesomab in musculoskeletal system infections

Objectives

To evaluate the usefulness of 99mTc-Besilesomab to diagnose infectious processes by using monoclonal antibodies BW 250/183 in a semi-quantitative analysis, and to determine the effect on diagnostic capacity of different thresholds for the difference between counts in early versus delayed images.

Methods

The study included 77 patients with suspected osteomyelitis who underwent scintigraphy with 99mTc-Besilesomab. After confirming the absence of human anti-mouse antibodies in all patients, early and delayed static images were acquired at 4 and 24 h post-injection, respectively. Visual and semi-quantitative analyses were conducted of regions of interest (ROIs) in areas suspected of infection on early and delayed images. Findings were considered positive when the ratio between counts in delayed and early images exceeded a given threshold after correction for decay. The definitive diagnosis was obtained by clinical follow-up, microbiological culture, or response to medical and/or surgical treatment.

Results

The optimal threshold was 1.02 (i.e., positive result = count increase of >2 % in delayed image), obtaining a sensitivity of 0.864, specificity of 0.858, positive predictive value of 0.708, negative predictive value of 0.940, and accuracy of 0.860. Application of the usual threshold of 1.10 (10 %) reduced the sensitivity to 0.734.

Conclusion

Semi-quantitative analysis of studies with 99mTc-Besilesomab is a useful technique for the diagnosis of musculoskeletal system infections and contributes to the definitive diagnosis when visual assessments are doubtful or non-conclusive.

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

Total knee arthroplasty is the most commonly performed joint replacement procedure in the United States. This manuscript will discuss the recommended imaging modalities for six clinical variants; 1. follow-up of symptomatic or asymptomatic patients with a total knee arthroplasty. Initial imaging, 2. Suspected infection after total knee arthroplasty. Additional imaging following radiographs, 3. Pain after total knee arthroplasty. Infection excluded. Suspect aseptic loosening or osteolysis or instability. Additional imaging following radiographs, 4. Pain after total knee arthroplasty. Suspect periprosthetic or hardware fracture. Additional imaging following radiographs, 5. Pain after total knee arthroplasty. Measuring component rotation. Additional imaging following radiographs, and 6. Pain after total knee arthroplasty. Suspect periprosthetic soft-tissue abnormality unrelated to infection, including quadriceps or patellar tendinopathy. Additional imaging following radiographs. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Nuclear Medicine Scans in Total Joint Replacement

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

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

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

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

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

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

Nuclear medicine imaging of bone infections

Osteomyelitis is a broad group of infectious diseases that involve the bone and/or bone marrow. It can arise haematogenously, via extension from a contiguous infection, or by direct inoculation during surgery or trauma. The diagnosis is not always obvious and imaging tests are frequently performed as part of the diagnostic work-up. Commonly performed radionuclide tests include technetium-99m ((99m)Tc)-diphosphonate bone scintigraphy (bone), and gallium-67 ((67)Ga) and in vitro labelled leukocyte (white blood cell; WBC) imaging. Although they are useful, each of these tests has limitations. Bone scintigraphy is sensitive but not specific, especially when underlying osseous abnormalities are present. (67)Ga accumulates in tumour, trauma, and in aseptic inflammation; furthermore, there is typically an interval of 1-3 days between radiopharmaceutical injection of and imaging. Currently, this agent is used primarily for spinal infections. Except for the spine, WBC imaging is the nuclear medicine test of choice for diagnosing complicating osteomyelitis. The in vitro leukocyte labelling process requires skilled personnel, is laborious, and is not always available. Complementary marrow imaging is usually required to maximise accuracy. Not surprisingly, alternative radiopharmaceuticals are continuously being investigated. Radiolabelled anti-granulocyte antibodies and antibody fragments, investigated as in vivo leukocyte labelling agents, have their own limitations and are not widely available. (111)In-biotin is useful for diagnosing spinal infections. Radiolabelled synthetic fragments of ubiquicidin, a naturally occurring human antimicrobial peptide that targets bacteria, have shown promise as infection specific radiopharmaceuticals. 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography (PET) with or without computed tomography (CT) is very useful in musculoskeletal infection. Sensitivities of more than 95% and specificities ranging from 75-99% have been reported in acute and subacute bone and soft-tissue infection. FDG is the radionuclide test of choice for spinal infection. It is sensitive, has a high negative predictive value, and can differentiate degenerative from infectious vertebral body end-plate abnormalities. Data on the accuracy of FDG for diagnosing diabetic pedal osteomyelitis and prosthetic joint infection are inconclusive and its role for these indications remains to be determined. Other PET radiopharmaceuticals that are under investigation as infection imaging agents include gallium-68 citrate ((68)Ga) and iodine-124 fialuridine ((124)I -FIAU).

Radionuclide imaging of osteomyelitis

Radionuclide procedures frequently are performed as part of the diagnostic workup of osteomyelitis. Bone scintigraphy accurately diagnoses osteomyelitis in bones not affected by underlying conditions. Degenerative joint disease, fracture, and orthopedic hardware decrease the specificity of the bone scan, making it less useful in these situations. Gallium-67 scintigraphy was often used as an adjunct to bone scintigraphy for diagnosing osteomyelitis. However, now it is used primarily for spinal infections when (18)F-FDG imaging cannot be performed. Except for the spine, in vitro-labeled leukocyte imaging is the nuclear medicine test of choice for diagnosing complicating osteomyelitis. Leukocytes accumulate in bone marrow as well as in infection. Performing complementary bone marrow imaging with (99m)Tc-sulfur colloid facilitates the differentiation between osteomyelitis and normal marrow and improves test overall accuracy. Antigranulocyte antibodies and antibody fragments, such as (99m)Tc-besilesomab and (99m)Tc-sulesomab, were developed to eliminate the disadvantages associated with in vitro-labeled leukocytes. These agents, however, have their own shortcomings and are not widely available. As biotin is used as a growth factor by certain bacteria, (111)In-biotin is useful to diagnose spinal infections. Radiolabeled synthetic fragments of ubiquicidin, a naturally occurring human antimicrobial peptide that targets bacteria, can differentiate infection from sterile inflammation and may be useful to monitor response to treatment. (18)F-FDG is extremely useful in the diagnostic workup of osteomyelitis. Sensitivity in excess of 95% and specificity ranging from 75%-99% have been reported. (18)F-FDG is the radionuclide test of choice for spinal infection. The test is sensitive, with a high negative predictive value, and reliably differentiates degenerative from infectious vertebral body end-plate abnormalities. Data on the accuracy of (18)F-FDG for diagnosing diabetic pedal osteomyelitis are contradictory, and its role for this indication remains to be determined. Initial investigations suggested that (18)F-FDG accurately diagnoses prosthetic joint infection; more recent data indicate that it cannot differentiate infection from other causes of prosthetic failure. Preliminary data on the PET agents gallium-68 and iodine-124 fialuridine indicate that these agents may have a role in diagnosing osteomyelitis.

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

Soon after the introduction of the modern prosthetic joint, it was recognized that radionuclide imaging provides useful information about these devices. The bone scan was used extensively to identify causes of prosthetic joint failure. It became apparent, however, that although sensitive, regardless of how the images were analyzed or how it was performed, the test was not specific and could not distinguish among the causes of prosthetic failure. Advances in anatomic imaging, notably cross sectional modalities, have facilitated the diagnosis of many, if not most, causes of prosthetic failure, with the important exception of infection. This has led to a shift in the diagnostic paradigm, in which nuclear medicine investigations increasingly have focused on diagnosing infection. The recognition that bone scintigraphy could not reliably diagnose infection led to the development of combined studies, first bone/gallium and subsequently leukocyte/bone and leukocyte/marrow imaging. Labeled leukocyte imaging, combined with bone marrow imaging is the most accurate (about 90%) imaging test for diagnosing joint arthroplasty infection. Its value not withstanding, there are significant disadvantages to this test. In-vivo techniques for labeling leukocytes, using antigranulocyte antibodies have been explored, but have their own limitations and the results have been inconsistent. Fluorodeoxyglucose (FDG)-positron emission tomography (FDG-PET) has been extensively investigated for more than a decade but its role in diagnosing the infected prosthesis has yet to be established. Antimicrobial peptides bind to bacterial cell membranes and are infection specific. Data suggest that these agents may be useful for diagnosing prosthetic joint infection, but large scale studies have yet to be undertaken. Although for many years nuclear medicine has focused on diagnosing prosthetic joint infection, the advent of hybrid imaging with single-photon emission computed tomography(SPECT)/electronic computer X-ray tomography technique (CT) and the availability of fluorine-18 fluoride PET suggests that the diagnostic paradigm may be shifting again. By providing the anatomic information lacking in conventional radionuclide studies, there is renewed interest in bone scintigraphy, performed as a SPECT/CT procedure, for detecting joint instability, mechanical loosening and component malpositioning. Fluoride-PET may provide new insights into periprosthetic bone metabolism. The objective of this manuscript is to provide a comprehensive review of the evolution of nuclear medicine imaging of joint replacements.

Use of anti-granulocyte scintigraphy with 99mTc-labeled monoclonal antibodies for the diagnosis of periprosthetic infection in patients after total joint arthroplasty: a diagnostic meta-analysis

The accurate diagnosis of periprosthetic joint infections (PJI) is crucial for therapy and the prevention of complications. No diagnostic test of PJI is 100% accurate. The aim of this study was to assess the use of anti-granulocyte scintigraphy using 99 mTc-labeled monoclonal antibodies to diagnose PJI after total joint arthroplasty. A systematic search of all relevant studies published through January 2013 was conducted using the MEDLINE, EMBASE, OVID, and ScienceDirect databases. Observational studies that assessed the accuracy of the anti-granulocyte scintigraphy with monoclonal antibodies or antibody fragments labeled with technetium 99 m in diagnosis for PJI and provided data on specificity and sensitivity were identified. Standard methods recommended for meta-analysis of diagnostic accuracy were used. Nineteen studies were eligible for inclusion. The results demonstrated that the area under the summary receiver operator curve was 0.88, and the diagnostic accuracy (Q*) was 0.81. Additionally, the diagnostic odds ratio (DOR) was 18.76 with a corresponding 95% confidence interval of 10.45–33.68. The pooled sensitivity and specificity of the diagnostic method for the diagnosis of PJI were 83% and 79%, respectively, while the pooled positive likelihood ratio (PLR) was 3.56, and the negative likelihood ratio (NLR) was 0.26. Anti-granulocyte scintigraphy using 99 mTc-labeled monoclonal antibodies has a reasonable role in the diagnosis of PJI after total joint arthroplasty. Due to the limitations of the present meta-analysis, additional high-quality original studies are required to confirm the predictive value.

Tibial tubercle osteotomy or quadriceps snip in two-stage revision for prosthetic knee infection? A randomized prospective study

BACKGROUND

Although 7% to 38% of revision total knee arthroplasties (RTKAs) are attributable to prosthetic knee infections, controversy exists regarding the best surgical approach while reducing the risk of extensor mechanism complications and the reinfection rate.

QUESTIONS/PURPOSES

We compared The Knee Society Score(©) (KSS), incidences of complications, maximum knee flexion, residual extension lag, and reinfection rate in patients with prosthetic knee infections treated with two-stage RTKAs using either the tibial tubercle osteotomy (TTO) or the quadriceps snip (QS) for exposure at the time of reimplantation.

METHODS

We prospectively followed 81 patients with chronic prosthetic knee infections treated between 1997 and 2004. Patients were randomized to receive a TTO or QS for exposure at the time of reimplantation. All patients had the same rehabilitation protocol. The minimum followup was 8 years (mean, 12 years; range, 8-15 years).

RESULTS

Patients in the TTO group had a higher mean KSS than the QS group (88 versus 70, respectively). Mean maximum knee flexion was greater in the TTO group (113° versus 94°); with a lower incidence of extension lag (45% versus 13%). We observed no differences in reinfection rate between groups.

CONCLUSIONS

We found the TTO combined with an early rehabilitation protocol associated with superior KSS did not impair extensor mechanism function or increase the reinfection rate. We believe a two-stage RTKA with TTO is a reasonable approach for treating prosthetic knee infections.

LEVEL OF EVIDENCE

Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Past and Present Scenario of Imaging Infection and Inflammation: A Nuclear Medicine Perspective

Nuclear medicine techniques provide potential non-invasive tools for imaging infections and inflammations in the body in a precise way. These techniques are further exploited by the use of radiopharmaceuticals in conjunction with imaging tests such as scintigraphy and positron emission tomography. Improved agents for targeting infection exploit the specific accumulation of radiolabeled compounds to understand the pathophysiologic changes involved in the inflammatory process and correlate them with other chronic illnesses. In the recent past, a wide variety of radiopharmaceuticals have been developed, broadly classified as specific radiopharmaceuticals and nonspecific radiopharmaceuticals. New developments in positron emission (leveraging 18F and 18fluorodeoxyglucose) and heterocyclic/peptide chemistry and radiochemistry are resulting in unique agents with high specific activity. Various approaches to visualizing infection and inflammation are presented in this review, in an integral manner, that give a clear view of the existing radiopharmaceuticals in clinical practice and those under development.

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.

The molecular imaging approach to image infections and inflammation by nuclear medicine techniques

Inflammatory and infectious diseases are a heterogeneous class of diseases that may be divided into infections, acute inflammation and chronic inflammation. Radiological imaging techniques have, with the exception of functional MRI, high sensitivity but lack in specificity. Nuclear medicine techniques, by contrast, allow the in vivo detection in humans of different physiologic and pathologic phenomena and offer noninvasive tools to detect early pathophysiological changes before anatomical changes occur. In this review, we highlight the role of nuclear medicine in inflammation/infection with emphasis on molecular imaging for in vivo histological characterization of affected tissues for diagnostic purposes and follow-up of therapies. We also describe the clinical indications of all available radiopharmaceuticals in the light of the newly available guidelines.

[Nuclear medical imaging in case of painful knee arthroplasty]

RATIONALE

The aim of the present study was to calculate the overall diagnostic accuracy of nuclear medical imaging in patients with painful knee arthroplasty.

MATERIAL AND METHODS

This retrospective study of all patients (n=87) where a (99m)Tc-triple phase bone scintigraphy (TPBS; n=120) and (99m)Tc-anti-granulocyte scintigraphy (BW 250/183; n=20) for a painful knee arthroplasty was performed between 2003 and 2007.

RESULTS

A total of 87 patients with 94 knee arthroplasties were examined to detect septic and aseptic loosening and to differentiate between them. The sensitivity, specificity, the positive and negative predictive value and accuracy of TPBS for the detection of septic knee arthroplasty loosening was 100%, 85%, 55%, 100%, 73% and for BW 250/183 was 91%, 66%, 76%, 85%, 80% for sepsis, respectively. A significant increase in diagnostic accuracy with 94%, 88%, 89%, 95% und 89% (p <0.001) could be achieved when both methods were used in combination.

CONCLUSION

Both methods alone have high negative predictive values, but the combination of both is complementary and significantly increases the diagnostic accuracy and positive predictive value for final diagnosis of knee arthroplasty loosening.

New imaging tools for the diagnosis of infection

Infection imaging became widespread in 1971 with the release of 67Ga citrate. Multiphase skeletal scintigraphy and radiolabeled white blood cells (WBCs) have since become the most widespread clinically used agents for the imaging of infection. A wide variety of other radiolabeled probes are under investigation, based on antibodies, cytokines, assorted proteins and other molecules, alone or in various combinations. However, these latter agents, with a few exceptions, are not routinely used clinically. Radiolabeled ciprofloxacin represents the first attempt to develop an infection-specific imaging agent (most infection-imaging probes localized nonspecifically to inflammation as well), but it has not proven superior to radiolabeled WBCs or 18F-fluoro-deoxy-glucose (FDG) PET. Because of the ability to combine exquisite anatomic detail with focal uptake of 18F-FDG, PET–computed tomography has achieved great success in the detection and localization of infection, including in clinically adverse conditions. Despite these advances, at this time an infection-specific imaging agent does not exist.

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

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

Prosthesis Infection: Diagnosis after Total Joint Arthroplasty with Antigranulocyte Scintigraphy with99mTc-labeled Monoclonal Antibodies—A Meta-Analysis

PURPOSE

To perform a meta-analysis of diagnostic studies regarding the accuracy of antigranulocyte scintigraphy (AGS) with monoclonal antibodies in the identification of prosthesis infection after total hip or knee arthroplasty.

MATERIALS AND METHODS

PubMed and EMBASE searches were conducted for the identification of relevant studies. Data on the diagnostic performance of AGS with monoclonal antibodies were combined quantitatively across eligible studies, and the overall sensitivity and specificity, along with summary receiver operating characteristic (ROC) curves and likelihood ratios (LRs), were estimated. The above parameters were evaluated for all patients and for various subgroups among the eligible studies. The reference standard used in the individual studies was accepted.

RESULTS

Thirteen eligible studies on nonoverlapping patient groups were included in the meta-analysis; there was a total sample size of 522 implants. The independent random effects summary estimates of sensitivity and specificity were 83% and 80%, respectively. The summary ROC curve estimate for weighted analysis was a sensitivity of 90% for a specificity of 80%. LR syntheses gave a weighted positive LR of 3.99 (95% confidence interval [CI]: 3.13, 5.09) and a weighted negative LR of 0.22 (95% CI: 0.15, 0.34); there was no statistically significant between-study heterogeneity for either metric. Various subgroup analyses did not reveal any statistically significant differences.

CONCLUSION

AGS with monoclonal antibodies had a reasonably high discriminating ability to identify prosthesis infection in patients who underwent total joint arthroplasty.

Nuclear medicine imaging of bone infections

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