Diagnosis of osteomyelitis of the foot in diabetic patients: value of 111In-leukocyte scintigraphy

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.

Is the Combination of Plain X-ray and Probe-to-Bone Test Useful for Diagnosing Diabetic Foot Osteomyelitis? A Systematic Review and Meta-Analysis

A systematic review and meta-analysis was conducted to assess the diagnostic accuracy of the combination of plain X-ray and probe-to-bone (PTB) test for diagnosing diabetic foot osteomyelitis (DFO). This systematic review has been registered in PROSPERO (a prospective international register of systematic reviews; identification code CRD42023436757). A literature search was conducted for each test separately along with a third search for their combination. A total of 18 articles were found and divided into three groups for separate analysis and comparison. All selected studies were evaluated using STROBE guidelines to assess the quality of reporting for observational studies. Meta-DiSc software was used to analyze the collected data. Concerning the diagnostic accuracy variables for each case, the pooled sensitivity (SEN) was higher for the combination of PTB and plain X-ray [0.94 (PTB + X-ray) vs. 0.91 (PTB) vs. 0.76 (X-ray)], as was the diagnostic odds ratio (DOR) (82.212 (PTB + X-ray) vs. 57.444 (PTB) vs. 4.897 (X-ray)). The specificity (SPE) and positive likelihood ratio (LR+) were equally satisfactory for the diagnostic combination but somewhat lower than for PTB alone (SPE: 0.83 (PTB + X-ray) vs. 0.86 (PTB) vs. 0.76 (X-ray); LR+: 5.684 (PTB + X-ray) vs. 6.344 (PTB) vs. 1.969 (X-ray)). The combination of PTB and plain X-ray showed high diagnostic accuracy comparable to that of MRI and histopathology diagnosis (the gold standard), so it could be considered useful for the diagnosis of DFO. In addition, this diagnostic combination is accessible and inexpensive but requires training and experience to correctly interpret the results. Therefore, recommendations for this technique should be included in the context of specialized units with a high prevalence of DFO.

Imaging tests for the detection of osteomyelitis: a systematic review

BACKGROUND

Osteomyelitis is an infection of the bone. Medical imaging tests, such as radiography, ultrasound, magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT) and positron emission tomography (PET), are often used to diagnose osteomyelitis.

OBJECTIVES

To systematically review the evidence on the diagnostic accuracy, inter-rater reliability and implementation of imaging tests to diagnose osteomyelitis.

DATA SOURCES

We conducted a systematic review of imaging tests to diagnose osteomyelitis. We searched MEDLINE and other databases from inception to July 2018.

REVIEW METHODS

Risk of bias was assessed with QUADAS-2 [quality assessment of diagnostic accuracy studies (version 2)]. Diagnostic accuracy was assessed using bivariate regression models. Imaging tests were compared. Subgroup analyses were performed based on the location and nature of the suspected osteomyelitis. Studies of children, inter-rater reliability and implementation outcomes were synthesised narratively.

RESULTS

Eighty-one studies were included (diagnostic accuracy: 77 studies; inter-rater reliability: 11 studies; implementation: one study; some studies were included in two reviews). One-quarter of diagnostic accuracy studies were rated as being at a high risk of bias. In adults, MRI had high diagnostic accuracy [95.6% sensitivity, 95% confidence interval (CI) 92.4% to 97.5%; 80.7% specificity, 95% CI 70.8% to 87.8%]. PET also had high accuracy (85.1% sensitivity, 95% CI 71.5% to 92.9%; 92.8% specificity, 95% CI 83.0% to 97.1%), as did SPECT (95.1% sensitivity, 95% CI 87.8% to 98.1%; 82.0% specificity, 95% CI 61.5% to 92.8%). There was similar diagnostic performance with MRI, PET and SPECT. Scintigraphy (83.6% sensitivity, 95% CI 71.8% to 91.1%; 70.6% specificity, 57.7% to 80.8%), computed tomography (69.7% sensitivity, 95% CI 40.1% to 88.7%; 90.2% specificity, 95% CI 57.6% to 98.4%) and radiography (70.4% sensitivity, 95% CI 61.6% to 77.8%; 81.5% specificity, 95% CI 69.6% to 89.5%) all had generally inferior diagnostic accuracy. Technetium-99m hexamethylpropyleneamine oxime white blood cell scintigraphy (87.3% sensitivity, 95% CI 75.1% to 94.0%; 94.7% specificity, 95% CI 84.9% to 98.3%) had higher diagnostic accuracy, similar to that of PET or MRI. There was no evidence that diagnostic accuracy varied by scan location or cause of osteomyelitis, although data on many scan locations were limited. Diagnostic accuracy in diabetic foot patients was similar to the overall results. Only three studies in children were identified; results were too limited to draw any conclusions. Eleven studies evaluated inter-rater reliability. MRI had acceptable inter-rater reliability. We found only one study on test implementation and no evidence on patient preferences or cost-effectiveness of imaging tests for osteomyelitis.

LIMITATIONS

Most studies included < 50 participants and were poorly reported. There was limited evidence for children, ultrasonography and on clinical factors other than diagnostic accuracy.

CONCLUSIONS

Osteomyelitis is reliably diagnosed by MRI, PET and SPECT. No clear reason to prefer one test over the other in terms of diagnostic accuracy was identified. The wider availability of MRI machines, and the fact that MRI does not expose patients to harmful ionising radiation, may mean that MRI is preferable in most cases. Diagnostic accuracy does not appear to vary with the potential cause of osteomyelitis or with the body part scanned. Considerable uncertainty remains over the diagnostic accuracy of imaging tests in children. Studies of diagnostic accuracy in children, particularly using MRI and ultrasound, are needed.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42017068511.

FUNDING

This project was funded by the National Institute for Health Research Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 23, No. 61. See the NIHR Journals Library website for further project information.

Imaging for detection of osteomyelitis in people with diabetic foot ulcers: A systematic review and meta-analysis

BACKGROUND

Osteomyelitis is an infection of the bone which can occur in people with diabetic foot ulcers. It can be diagnosed using X-rays, ultrasound, scintigraphy, magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT) and positron emission tomography (PET).

OBJECTIVES

To review the evidence on the diagnostic accuracy of imaging tests to diagnose osteomyelitis in people with diabetic foot ulcers.

METHODS

We conducted a systematic review and meta-analysis. MEDLINE, EMBASE and other databases were searched to July 2018. Risk of bias was evaluated. Diagnostic accuracy was estimated using bivariate meta-analyses.

RESULTS

Thirty-six studies were included in the meta-analysis. Eight studies were at high risk of bias MRI had high diagnostic accuracy (22 studies: 96.4 % sensitivity (95 % CI 90.7-98.7); 83.8 % specificity (76.0-89.5)). PET scans also had high accuracy (6 studies: 84.3 % sensitivity (52.8-96.3); 92.8 % specificity (75.7-98.2)), and possibly also SPECT, but with few studies (3 studies: 95.6 % sensitivity (76.0-99.3); 55.1 % specificity (19.3-86.3)). Scintigraphy (17 studies: 84.2 % sensitivity (76.8-89.6); 67.7 % specificity (56.2-77.4)), and X-rays (16 studies: 61.9 % sensitivity (50.5-72.1); 78.3 % specificity (62.9-88.5)) had generally inferior diagnostic accuracy.

CONCLUSIONS

MRI and PET both reliably diagnose osteomyelitis in diabetic foot ulcer patients. SPECT may also have good diagnostic accuracy, although evidence is limited. This review confirms most current guidelines, showing that MRI may be the preferable test in most cases, given its wider availability and the lack of potentially harmful ionising radiation.

Diabetic Foot Infections: The Diagnostic Challenges

Diabetic foot infections (DFIs) are severe complications of long-standing diabetes, and they represent a diagnostic challenge, since the differentiation between osteomyelitis (OM), soft tissue infection (STI), and Charcot’s osteoarthropathy is very difficult to achieve. Nevertheless, such differential diagnosis is mandatory in order to plan the most appropriate treatment for the patient. The isolation of the pathogen from bone or soft tissues is still the gold standard for diagnosis; however, it would be desirable to have a non-invasive test that is able to detect, localize, and evaluate the extent of the infection with high accuracy. A multidisciplinary approach is the key for the correct management of diabetic patients dealing with infective complications, but at the moment, no definite diagnostic flow charts still exist. This review aims at providing an overview on multimodality imaging for the diagnosis of DFI and to address evidence-based answers to the clinicians when they appeal to radiologists or nuclear medicine (NM) physicians for studying their patients.

Ultrasonographic features of acute Charcot neuroarthropathy of the foot: a pilot study

OBJECTIVES

Our aim was to characterize the ultrasonographic features of patients with acute Charcot neuroarthropathy (CN) of the foot.

METHODS

In this prospective study, 26 patients with CN of the foot proved by MRI were enrolled. All patients were in early stage of CN with normal radiography (grade 0 modified Eichenholtz classification system). Ultrasonographic examination of mid-tarsal and ankle joints was performed with a 7-15 MHz linear probe.

RESULTS

Ages of our patients ranged from 38 to 67 years (57.3 ± 6.4). About 96.2% of our patients (25 patients) had diabetes mellitus. Ultrasonographic findings were as follows: effusion/synovitis (100%) with high Doppler activity (92.3%) in the mid-tarsal joints, and effusion/synovitis (92.3%) and high Doppler activity (84.6%) in the ankle joints. Bone erosions were present in the distal fibula in 23 patients (79.3%), while in distal tibia in 9 patients (34.6%). Tendonitis was found in tibialis posterior tendons in 23 patients (88.4%), and in peroneal tendons in 22 patients (84.6%). A combination of active synovitis (in mid-tarsal joints and ankle joints), active tendonitis (of tibialis posterior and peroneal tendons), and erosions in the distal end of fibula was present in 21 patients (80.8%).

CONCLUSIONS

Ultrasonography is able to detect soft tissue inflammation and pre-radiographic bony changes in early stages of CN. Key Points •Ultrasound is a useful diagnostic tool for pre-radiographic stages of Charcot joint. •High-grade synovitis, high-grade tenosynovitis, and bony erosions are highly suggestive of Charcot arthropathy.

Clinical Applications for Radiotracer Imaging of Lower Extremity Peripheral Arterial Disease and Critical Limb Ischemia

Peripheral arterial disease (PAD) is an atherosclerotic occlusive disease of the non-coronary vessels that is characterized by lower extremity tissue ischemia, claudication, increased prevalence of lower extremity wounds and amputations, and impaired quality of life. Critical limb ischemia (CLI) represents the severe stage of PAD and is associated with additional risk for wound formation, amputation, and premature death. Standard clinical tools utilized for assessing PAD and CLI primarily focus on anatomical evaluation of peripheral vascular lesions or hemodynamic assessment of the peripheral circulation. Evaluation of underlying pathophysiology has traditionally been achieved by radiotracer-based imaging, with many clinical investigations focusing on imaging of skeletal muscle perfusion and cases of foot infection/inflammation such as osteomyelitis and Charcot neuropathic osteoarthropathy. As advancements in hybrid imaging systems and radiotracers continue to evolve, opportunities for molecular imaging of PAD and CLI are also emerging that may offer novel insight into associated complications such as peripheral atherosclerosis, alterations in skeletal muscle metabolism, and peripheral neuropathy. This review summarizes the pros and cons of radiotracer-based techniques that have been utilized in the clinical environment for evaluating lower extremity ischemia and common pathologies associated with PAD and CLI.

The acute Charcot foot in diabetics: Diagnosis and management

Acute Charcot foot is a diagnostic challenge.

The exact pathophysiology is not fully understood.

Acute Charcot foot is often present with a history of trauma or cellulitis which does not respond to antibiotics.

The condition is best managed within a multidisciplinary team.

The mainstay of the treatment is mechanical off-loading and total contact casting.

Surgery is reserved for select cases.

Cite this article: EFORT Open Rev 2018;3:568-573. DOI: 10.1302/2058-5241.3.180003

Detection of Osteomyelitis in the Diabetic Foot by Imaging Techniques: A Systematic Review and Meta-analysis Comparing MRI, White Blood Cell Scintigraphy, and FDG-PET

OBJECTIVE

Diagnosing bone infection in the diabetic foot is challenging and often requires several diagnostic procedures, including advanced imaging. We compared the diagnostic performances of MRI, radiolabeled white blood cell (WBC) scintigraphy (either with ^99mTc-hexamethylpropyleneamineoxime [HMPAO] or ¹¹¹In-oxine), and [¹⁸F]fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET)/computed tomography.

RESEARCH DESIGN AND METHODS

We searched Medline and Embase as of August 2016 for studies of diagnostic tests on patients known or suspected to have diabetes and a foot infection. We performed a systematic review using criteria recommended by the Cochrane Review of a database that included prospective and retrospective diagnostic studies performed on patients with diabetes in whom there was a clinical suspicion of osteomyelitis of the foot. The preferred reference standard was bone biopsy and subsequent pathological (or microbiological) examination.

RESULTS

Our review found 6,649 articles; 3,894 in Medline and 2,755 in Embase. A total of 27 full articles and 2 posters was selected for inclusion in the analysis. The performance characteristics for the ¹⁸F-FDG-PET were: sensitivity, 89%; specificity, 92%; diagnostic odds ratio (DOR), 95; positive likelihood ratio (LR), 11; and negative LR, 0.11. For WBC scan with ¹¹¹In-oxine, the values were: sensitivity, 92%; specificity, 75%; DOR, 34; positive LR, 3.6; and negative LR, 0.1. For WBC scan with ^99mTc-HMPAO, the values were: sensitivity, 91%; specificity, 92%; DOR, 118; positive LR, 12; and negative LR, 0.1. Finally, for MRI, the values were: sensitivity, 93%; specificity, 75%; DOR, 37; positive LR, 3.66, and negative LR, 0.10.

CONCLUSIONS

The various modalities have similar sensitivity, but ¹⁸F-FDG-PET and ^99mTc-HMPAO-labeled WBC scintigraphy offer the highest specificity. Larger prospective studies with a direct comparison among the different imaging techniques are required.

Diagnosis and management of infection in the diabetic foot

Foot infections are common in persons with diabetes mellitus. Most diabetic foot infections occur in a foot ulcer, which serves as a point of entry for pathogens. Unchecked, infection can spread contiguously to involve underlying tissues, including bone. A diabetic foot infection is often the pivotal event leading to lower extremity amputation, which account for about 60% of all amputations in developed countries. Given the crucial role infections play in the cascade toward amputation, all clinicians who see diabetic patients should have at least a basic understanding of how to diagnose and treat this problem.

Charcot neuroarthropathy of the foot and ankle: a review

Charcot neuroarthropathy is a limb-threatening, destructive process that occurs in patients with neuropathy associated with medical diseases such as diabetes mellitus. Clinicians' treating diabetic patients should be vigilant in recognizing the early signs of acute Charcot neuroarthropathy, such as pain, warmth, edema, or pathologic fracture in a neuropathic foot. Early detection and prompt treatment can prevent joint and bone destruction, which, if untreated, can lead to morbidity and high-level amputation. A high degree of suspicion is necessary. Once the early signs have been detected, prompt immobilization and offloading are important. Treatment should be determined on an individual basis, and it must be determined whether a patient can be treated conservatively or will require surgical intervention when entering the chronic phase. If diagnosed early, medical and conservative measures only will be required. Surgery is indicated for patients with severe or unstable deformities that, if untreated, will result in major amputations. A team approach that includes a foot and ankle surgeon, a diabetologist, a physiotherapist, a medical social councilor, and, most importantly, the patient and immediate family members is vital for successful management of this serious condition.

The Charcot foot in diabetes

The diabetic Charcot foot syndrome is a serious and potentially limb-threatening lower-extremity complication of diabetes. First described in 1883, this enigmatic condition continues to challenge even the most experienced practitioners. Now considered an inflammatory syndrome, the diabetic Charcot foot is characterized by varying degrees of bone and joint disorganization secondary to underlying neuropathy, trauma, and perturbations of bone metabolism. An international task force of experts was convened by the American Diabetes Association and the American Podiatric Medical Association in January 2011 to summarize available evidence on the pathophysiology, natural history, presentations, and treatment recommendations for this entity.

Expert opinion on the management of infections in the diabetic foot

This update of the International Working Group on the Diabetic Foot incorporates some information from a related review of diabetic foot osteomyelitis (DFO) and a systematic review of the management of infection of the diabetic foot. The pathophysiology of these infections is now well understood, and there is a validated system for classifying the severity of infections based on their clinical findings. Diagnosing osteomyelitis remains difficult, but several recent publications have clarified the role of clinical, laboratory and imaging tests. Magnetic resonance imaging has emerged as the most accurate means of diagnosing bone infection, but bone biopsy for culture and histopathology remains the criterion standard. Determining the organisms responsible for a diabetic foot infection via culture of appropriately collected tissue specimens enables clinicians to make optimal antibiotic choices based on culture and sensitivity results. In addition to culture-directed antibiotic therapy, most infections require some surgical intervention, ranging from minor debridement to major resection, amputation or revascularization. Clinicians must also provide proper wound care to ensure healing of the wound. Various adjunctive therapies may benefit some patients, but the data supporting them are weak. If properly treated, most diabetic foot infections can be cured. Providers practising in developing countries, and their patients, face especially challenging situations.

The Charcot foot in diabetes

The diabetic Charcot foot syndrome is a serious and potentially limb-threatening lower-extremity complication of diabetes. First described in 1883, this enigmatic condition continues to challenge even the most experienced practitioners. Now considered an inflammatory syndrome, the diabetic Charcot foot is characterized by varying degrees of bone and joint disorganization secondary to underlying neuropathy, trauma, and perturbations of bone metabolism. An international task force of experts was convened by the American Diabetes Association and the American Podiatric Medical Association in January 2011 to summarize available evidence on the pathophysiology, natural history, presentations, and treatment recommendations for this entity.

Current concepts in imaging diabetic pedal osteomyelitis

Diabetic pedal osteomyelitis is primarily a manifestation of vascular insufficiency with resultant tissue ischemia, neuropathy, and infection. Nearly all cases of pedal osteomyelitis arise from a contiguous ulcer and soft tissue infection. MR imaging is the modality of choice to assess for the presence of osteomyelitis and associated soft tissue complications, to guide patient management, and to aid in limited limb resection.

Surgical aspects of the diabetic foot

A comprehensive review of the literature relating to the pathology and management of the diabetic foot is presented. This should provide a guide for the treatment of ulcers, Charcot neuro-arthropathy and fractures involving the foot and ankle in diabetic patients.

Potential role of FDG PET in the setting of diabetic neuro-osteoarthropathy: can it differentiate uncomplicated Charcot's neuroarthropathy from osteomyelitis and soft-tissue infection?

BACKGROUND

This paper is based on the results from an ongoing prospective trial designed to investigate the usefulness of FDG PET in the complicated diabetic foot.

AIM

To investigate the potential utility of FDG PET imaging in the setting of acute neuropathic osteoarthropathy (Charcot's foot).

PATIENTS AND METHODS

A total of 63 patients, in four groups, were evaluated. The groups were: (A) 17 patients with a clinical diagnosis of Charcot's neuroarthropathy (11 men, six women; mean age: 59.4+/-8.6 years); (B) 21 patients with uncomplicated diabetic foot (16 men, five women; mean age: 63+/-10 years); (C) 20 non-diabetic patients with normal lower extremities (12 men, eight women; mean age 54+/-19 years); and (D) five patients with proven osteomyelitis secondary to complicated diabetic foot (three men, two women; mean age: 61.2+/-13.9 years). Five patients in group A had foot ulcer and intermediate to high degree of suspicion for superimposed osteomyelitis. Each subject underwent FDG PET imaging of the lower extremities in addition to MRI and the findings were compared with the final diagnostic outcome based on histopathology and clinical follow-up. The images were examined visually for focal abnormalities. Regions of interest were assigned to the sites of abnormal FDG uptake for calculating maximum standardized uptake value (SUVmax). Two important clinical decision-making issues were explored: (1) whether FDG PET shows a definitive uptake pattern in Charcot's neuroarthropathy and if so whether that could be utilized to differentiate it from other complicated forms of diabetic foot like osteomyelitis and cellulitis, which is frequently a diagnostic challenge in this clinical setting; and (2) how accurate FDG PET is in detection soft tissue infection in patients with Charcot's foot. These issues were examined by utilizing FDG PET findings along with MRI results in the same patient.

RESULTS

We observed a low degree of diffuse FDG uptake in the Charcot's joints. This was clearly distinguishable from the normal joints. The SUVmax in the Charcot's lesions varied from 0.7 to 2.4 (mean, 1.3+/-0.4) while those of midfoot of the normal control subjects and the uncomplicated diabetic foot ranged from 0.2 to 0.7 (mean 0.42+/-0.12) and from 0.2 to 0.8 (mean 0.5+/-0.16), respectively. The only patient with Charcot's foot with superimposed osteomyelitis had an SUVmax of 6.5. The SUVmax of the sites of osteomyelitis as a complication of diabetic foot was 2.9-6.2 (mean: 4.38+/-1.39). Unifactorial analysis of variance test yielded a statistical significance in the SUVmax between the four groups (P<0.01). The SUVmax between the normal control groups and the uncomplicated diabetic foot was not statistically significant by the Student's t-test (P>0.05). In the setting of concomitant foot ulcer FDG PET accurately ruled out osteomyelitis. Overall sensitivity and accuracy of FDG PET in the diagnosis of Charcot's foot was 100 and 93.8%, respectively; and for MRI were 76.9 and 75%, respectively. FDG PET showed foci of abnormally enhanced uptake in the soft tissue which was suggestive of inflammation in seven cases (43.75%) which were proven pathologically to be secondary to infection. In only two of these cases the features of soft tissue infection were noted on the magnetic resonance images.

CONCLUSION

The results support a valuable role of FDG PET in the setting of Charcot's neuroarthropathy by reliably differentiating it from osteomyelitis both in general and when foot ulcer is present.

Imaging of osteomyelitis: current concepts

Osteomyelitis frequently requires more than one imaging technique for an accurate diagnosis. Conventional radiography still remains the first imaging modality. MRI and nuclear medicine are the most sensitive and specific methods for the detection of osteomyelitis. MRI provides more accurate information regarding the extent of the infectious process. Ultrasound represents a noninvasive method to evaluate the involved soft tissues and cortical bone and may provide guidance for diagnostic or therapeutic aspiration, drainage, or tissue biopsy. CT scan can be a useful method to detect early osseous erosion and to document the presence of sequestra. PET and SPECT are highly accurate techniques for the evaluation of chronic osteomyelitis, allowing differentiation from soft tissue infection.

Nuclear medicine imaging of diabetic foot infection: results of meta-analysis

BACKGROUND AND AIM

Osteomyelitis of the foot is the most commonly encountered complication in diabetic patients. Nuclear medicine techniques are usually complementary to radiology in the diagnosis of foot infections; they play an important role in various clinical situations. The aim of this study was to develop a practical guideline to describe the radiopharmaceuticals to be used for different clinical conditions and different aims in diabetic foot infection.

METHODS

In this study, we reviewed 57 papers (published between 1982 and 2004; 50 original papers and seven reviews) that described the imaging of the diabetic foot and examined a total of 2889 lesions. We performed data analysis to establish which imaging technique could be used as a 'gold standard' to diagnose infection, evaluate the extent of disease and monitor the efficacy of therapy.

RESULTS AND CONCLUSION

We provide a guideline to assist in the selection of the optimal radiopharmaceuticals for different clinical conditions and different aims.

Evaluating diabetic foot infection with magnetic resonance imaging: Kuwait experience

OBJECTIVE

The aim of this study was to evaluate the capability of magnetic resonance imaging (MRI) to depict and characterize the changes seen in diabetic foot infections.

SUBJECTS AND METHODS

MRI studies of 29 diabetic patients with suspected foot infection were evaluated. Sagittal and transverse T1-weighted images before and after intravenous gadolinium, and transverse fat-suppressed T2-weighted images were performed on the affected regions. The MRI findings were compared to subsequent clinical and/or histopathological findings.

RESULTS

The MRI findings were: osteomyelitis in 14 patients, abscess in 5, cellulitis in 26, tenosynovitis in 4 and neuropathic joint in 8. Three cases were normal. Pathological confirmations were obtained in 19 patients. MRI and histological diagnosis were in concordance in 79% of osteomyelitis cases, 100% of neuropathy cases and 100% of cellulitis cases. The sensitivity and specificity of MRI in diagnosing osteomyelitis were 100 and 63%, respectively. The positive predictive and negative predictive values, and the accuracy were 79, 100 and 84%, respectively. MRI helped surgical planning for limb salvage procedures in 6 of the osteomyelitis cases and in a cellulitis case.

CONCLUSION

The results indicate that MRI is a sensitive and accurate imaging modality for the evaluation of foot infections in diabetic patients and for planning proper treatment.

Imaging modalities of the diabetic foot

Charcot osteoarthropathy is a devastating process that occurs in the diabetic foot. It must be distinguished from other conditions, such as osteomyelitis, with efficiency and accuracy. The prognosis and treatment depends on it. Charcot progresses along four radiographically identifiable stages; therefore, plain films should be the first step in the evaluation. When osteomyelitis is suspected, a three-phase bone scan may allow clear enough anatomic detail to diagnosis bony involvement compared with soft tissue in the forefoot. In the midfoot, a three-phase bone scan alone is not specific enough to distinguish between Charcot and osteomyelitis. Enhancing the bone scans by adding an additional phase (four-phase) or tracer (gallium) does not appear to improve specificity significantly. Computerized bone flow studies may be more helpful in making the distinction, particularly in acute presentation. A CT scan is not indicated because the MR image will better define the anatomic extent of the process for preoperative planning. The combined WBC scans and sulfur colloid marrow scans show improved specificity and can distinguish between Charcot and osteomyelitis. Combined leukocyte scan with bone marrow imaging is superior to leukocyte and bone scan alone or in combination for detecting infection in the neuropathic foot. The combined leukocyte scan and bone marrow imaging is the current gold standard for evaluating the presence of diabetic foot infection versus osteoarthropathy, and MR imagine is the anatomic gold standard that may be used to define the extent of the process.

Diabetic foot infections and antibiotic therapy

Diabetic foot infections are associated with high morbidity and mortality rates as well as significant financial impact on the health care system. Improved patient outcomes and intelligent use of resources should determine the selection of diagnostic procedures and the therapeutic modalities used. Diabetic patients who develop lower extremity infections require a multidisciplinary approach in the management of their infections and other disorders. Aggressive surgical debridement and appropriate and adequate antibiotic therapy are necessary to successfully treat severe foot infections and permit faster recovery.

Bone scintigraphic findings in patients with foot ulcers and normal plain film radiographs

A prospective study was performed to examine the performance of bone scintigraphy in the earliest stage of soft-tissue foot ulceration with potential risk for progression to osteomyelitis. Twenty-three podiatry clinic patients with new or recurrent foot ulcers but negative plain film radiographs of the foot underwent 24 (one patient was studied twice) multiphase bone scans (flow, blood pool, and 3- and 24-hour delayed images) that were visually scored for severity of increased uptake on a scale of 0 to 3+, with 0 indicating normal and 3+ indicating severe. Twenty-one scans (88%) showed abnormal uptake on at least one phase, with 17 (71%) having increased bone uptake on late images. Ulcer healing without complications occurred in 20 cases (83%), whereas 4 cases had adverse outcomes, 3 requiring surgical resection for failure to heal and 1 having radiographic progression to frank osteomyelitis. All three patients whose bone scans showed severe abnormal uptake had an adverse clinical outcome.

Imaging of osteomyelitis and musculoskeletal soft tissue infections: current concepts

The diagnostic imaging of osteomyelitis can require the confluence of multiple imaging technologies. Conventional radiography should always be the first imaging modality. Sonography is most useful in the diagnosis of fluid collections in a joint or in the extra-articular soft tissues but is not useful for evaluating presence of osseous infection. CT scan can be a useful method to detect early osseous erosion and to document the presence of sequestrum, foreign body, or gas formation but generally is less sensitive than other modalities for the detection of bone infection. Nuclear medicine and MRI are the most sensitive and most specific imaging modalities for the detection of osteomyelitis. Nuclear medicine is particularly useful in identifying multifocal involvement, which is common in children. MRI provides more accurate information of the local extent of the soft tissues and possible soft tissue abscess in patients with musculoskeletal infection.

Work-up of the diabetic foot

Diabetes is a common disease with potentially devastating complications affecting the foot and ankle. A combination of vascular disease, peripheral neuropathy, and immunopathy results in a cascade of conditions including ischemia and infarction, tendinopathy, atrophy, edema, deformity, neuropathic osteoarthropathy, callus, ulceration, and infection. MRI is useful for evaluation of these complications, and assists the clinician in medical or surgical planning.

Osteomyelitis: diagnosis with (99m)Tc-labeled antigranulocyte antibodies compared with diagnosis with (111)In-labeled leukocytes--initial experience

PURPOSE

To compare a technetium 99m-labeled murine immunoglobulin M monoclonal antigranulocyte antibody that binds to human polymorphonuclear leukocyte CD15 antigens with indium 111 ((111)In)-labeled leukocytes in the diagnosis of appendicular skeletal osteomyelitis.

MATERIALS AND METHODS

Twenty-four patients suspected of having infected joint replacement (n = 12), diabetic pedal osteomyelitis (n = 8), or long bone osteomyelitis (n = 4) were imaged 5, 30, 60, and 120 minutes after antibody injection. Following injection, one patient experienced moderate joint pain exacerbation that resolved spontaneously. Patients underwent imaging with (111)In-labeled leukocytes and three-phase bone imaging. All studies were interpreted alone. Images obtained in antibody and (111)In-labeled leukocyte studies were also interpreted with the bone scans. One reader, without knowledge of other study results or final diagnoses, reviewed and interpreted images in a random order. Sensitivity, specificity, and accuracy were calculated for the antibody study at each time point, the (111)In-labeled leukocyte study, the three-phase bone scanning procedure, and dual-tracer studies.

RESULTS

There were 11 cases of osteomyelitis. Bone scintigraphy was sensitive (1.0) but nonspecific (0.38). Images obtained in the 120-minute antibody study were sensitive (0.91), moderately specific (0.69), and comparable to those obtained in the (111)In-labeled leukocyte study (0.91 sensitivity, 0.62 specificity). When interpreted with bone scans, images obtained in the antibody and (111)In-labeled leukocyte studies showed improved sensitivity and specificity (1.0 and 0.85 and 1.0 and 0.77, respectively).

CONCLUSION

Use of the monoclonal antigranulocyte antibody was comparable to the use of (111)In-labeled leukocytes in the diagnosis of appendicular skeletal osteomyelitis. The combined results of the monoclonal antibody study and bone scanning were more accurate (0.91) for diagnosing this entity than were the results of any of the other studies.

Current concepts in magnetic resonance imaging of the adult hip and pelvis

MRI is the diagnostic imaging modality of choice for most disorders of the hip and pelvis in the setting of nondiagnostic plain radiographs. Quality images of the entire pelvis with high-resolution images of the affected hip are recommended. Intravenous gadolinium is administered in cases of suspected soft-tissue or bone infection. MR arthrography enables assessment of the joint space and the acetabular labrum. With MRI, the radiologist has the ability to stage pathological conditions of the hip and pelvis in such a way as to determine prognosis and influence therapeutic decisions.

Detection of osteomyelitis in the neuropathic foot: nuclear medicine, MRI and conventional radiography

The diagnostic efficacy of (1) combined three-phase bone scintigraphy and In-111 labeled WBC scintigraphy (Bone/WBC), (2) MRI, and (3) conventional radiography in detecting osteomyelitis of the neuropathic foot was compared. Conventional radiography was comparable to MRI for detection of osteomyelitis. MRI best depicted the presence of osteomyelitis in the forefoot. Particularly in the setting of Charcot joints, Bone/WBC was more specific than conventional radiography or MRI.

99mTc-nanocolloid scintigraphy for assessing osteomyelitis in diabetic neuropathic feet

Distinguishing osteomyelitis from neuropathic osteoarthropathy in diabetic feet is a common and difficult clinical problem with no highly accurate discriminatory investigation. This study assesses the novel use of marrow scintigraphy and compares it with magnetic resonance imaging (MRI) for the diagnosis of osteomyelitis in neuropathic osteoarthropathic diabetic feet. Nine diabetic patients with chronic foot ulcers were prospectively assessed independently using 99mTc-nanocolloid scintigraphy and MRI. Those patients showing features of osteomyelitis underwent percutaneous bone biopsy or surgical ray excision for histological confirmation. Other patients were followed up clinically for a minimum of 6 months to exclude osteomyelitis. Marrow scintigraphy, in agreement with MRI, demonstrated all four cases of biopsy proven osteomyelitis and excluded three cases with neuropathic osteoarthropathy alone. One case of suspected osteomyelitis of the ankle on marrow scintigraphy, but not MRI, was not confirmed clinically. One case of suspected osteomyelitis on both imaging modalities was shown on biopsy to demonstrate changes of avascular necrosis but not osteomyelitis. In this study 99mTc-nanocolloid scintigraphy shows a sensitivity of 100% and specificity of 60%. An important false positive result is seen with avascular necrosis, both on marrow scintigraphy and on MRI. Although larger studies are needed to evaluate this technique, 99mTc-nanocolloid marrow scintigraphy may be an alternative to MRI for assessing diabetic feet for osteomyelitis.

Update on imaging of orthopedic infections

Although the diagnosis of infection is only a small part of the orthopedist's job description, it is a important part. This article discusses the fundamentals of orthopedic infections and highlights the refinements on this topic from a radiologic perspective. In addition to reviewing the imaging appearance of musculoskeletal infections in bone and the surrounding soft tissues, we focus on the advantages and disadvantages of five imaging methods: radiography, sonography, CT, scintigraphy, and MR imaging. Finally, we review three specific situations that have garnered substantial attention in recent medical literature: chronic recurrent multifocal osteomyelitis, musculoskeletal infections in AIDS patients, and pedal infections in diabetic patients.

A musculoskeletal radiologist's view of nuclear medicine

The introduction of cross-sectional and multiplanar imaging techniques has not diminished the value of radionuclide bone scanning. Skeletal scintigraphy remains an extremely effective and relatively inexpensive tool for diagnosis of many disorders of bones and joints. The sensitivity of scintigraphy in detecting stress fractures approaches 100%, although it is less specific than plain film radiography. However, radionuclide bone scanning can reveal subtle early changes in bone metabolism. For evaluation of infections, particularly in patients with diabetic foot neuropathy, scintigraphy is the modality of choice, although a combination of imaging techniques may be necessary in previously damaged bone. Radionuclide bone scanning has retained its place in the evaluation of primary bone tumors and metastases, and in screening of patients with metabolic bone disease. The radiologist should be aware that although this modality is generally used as an ancillary technique in conjunction with plain radiography, conventional tomography, computed tomography (CT), and magnetic resonance imaging (MRI), at times it can be used as the primary modality not only for the identification of skeletal lesions but also to provide important information required to make a definite diagnosis.

The use of intravenous contrast in MRI of extremity infection

Infection of the musculoskeletal system encompasses a variety of conditions, affecting skin, fascia, muscle, joints, tendon sheaths, and bone. In addition to features unique to each tissue site, these processes vary with respect to organism virulence, overall host condition, and the condition of the extremity itself, particularly its circulation. Treatment of musculoskeletal infection varies according to these features, and with respect to the presence of devitalized tissue. Unfortunately, while clinical examination is accurate for the presence of infection as a process in most circumstances, it lacks specificity for the variety of disorders within the spectrum of extremity infection. MRI examination using intravenous contrast is becoming the preferred modality to study complicated extremity infections, since it provides an accurate portrayal of the extent of osseous and non osseous involvement, and identifies areas of necrosis. This information provides a basis from which clinicians may more accurately choose from among treatment options.

Diagnosis of pedal osteomyelitis with Tc-99m HMPAO labeled leukocytes

The diagnosis of pedal osteomyelitis is often complicated by the presence of pre-existing bony abnormalities. In this study, the utility of radiolabeled white blood cell imaging for the detection of complicated pedal osteomyelitis was evaluated. Twenty-seven men and women were prospectively enrolled and underwent plain film radiography, three-phase bone scan, and Tc-99m hexamethylpropylamine oxine white blood cell scintigraphy of their feet. The presence or absence of osteomyelitis was confirmed in all subjects by microbiologic and histopatholigic analysis of resected bone tissue. The results indicated that white blood cell imaging was more sensitive (90%) and specific (86%) for infection than either bone scan (75% sensitive, 29% specific) or plain film radiography (55% sensitive, 57% specific). This preliminary study suggests that Tc-99m hexamethylpropylamine oxine-labeled white blood cell scintigraphy is a simple, accurate test for the detection of pedal osteomyelitis.

Role of magnetic resonance imaging in the diagnosis of osteomyelitis in diabetic foot infections

PURPOSE

The role of magnetic resonance imaging (MRI) in the diagnosis of osteomyelitis in foot infections in diabetics was investigated. The accuracy, sensitivity, and specificity of MRI, plain radiography, and nuclear scanning were determined for diagnosing osteomyelitis, and a cost comparison was made.

METHODS

Twenty-seven patients with diabetic foot infections were studied prospectively. All patients underwent MRI and plain radiography. Twenty-two patients had technetium bone scans, and 19 patients had Indium scans. Nineteen patients had all four tests performed. Patients with obvious gangrene or a fetid foot were excluded.

RESULTS

The diagnosis of osteomyelitis was established by pathologic specimen (n = 18), bone culture (n = 3), or successful response to medical management (n = 6). Osteomyelitis was confirmed in nine of the pathologic specimens. The diagnostic sensitivity, specificity, and accuracy for MRI was 88%, 100%, and 95%, respectively, for plain radiography it was 22%, 94%, and 70%, respectively, for technetium bone scanning it was 50%, 50%, and 50%, respectively, and for Indium leukocyte scanning it was 33%, 69%, and 58%, respectively. The data were analyzed statistically with the two-tailed Fisher's exact test. MRI was the only test that was statistically significant (p < 0.01).

CONCLUSIONS

MRI appeared to be the single best test for the diagnosis of osteomyelitis associated with diabetic foot infections. It had a better diagnostic accuracy than conventional modalities and appeared to be more cost-effective than the frequently used Indium scan.

Importance of dressing removal before radiolabeled WBC imaging for musculoskeletal infection

Leukocyte imaging performed with in-111 or Tc-99m is gaining widespread acceptance as a method for detection of osteomyelitis associated with soft tissue injury or infection. The authors present three cases in which initial imaging was suggestive of a focal infectious process in bone and soft tissue. However, repeat imaging after the removal of wound dressings, which revealed sero-sanguineous discharge in all cases, resulted in a scan appearance that was much less remarkable for focal radiotracer accumulation in the bone. The authors conclude that accumulation of labeled WBCs in wound discharge can result in scans that are false-positive for osteomyelitis. Therefore, the authors recommend that wounds should be cleaned and dressings changed before imaging in order to avoid scans that are false-positive for osteomyelitis.

Leukocytosis is a poor indicator of acute osteomyelitis of the foot in diabetes mellitus

The purpose of this article is to describe the frequency of leukocytosis and elevated erythrocyte sedimentation rate in a series of diabetics with acute foot infections and osteomyelitis due to neuropathic foot ulcerations. The authors reviewed the admission records of 28 type II diabetic patients admitted to University Hospital in San Antonio, Texas between January 1, 1990 and December 30, 1992 with acute osteomyelitis of the foot secondary to neuropathic ulceration. The mean white blood cell count on admission for all subjects studied was calculated at 11.9 +/- 5.4 x 10(3) cells/mm3. Of all white blood cell counts collected for patients admitted with acute osteomyelitis of the foot, 54% were within normal limits. Erythrocyte sedimentation rate was elevated in 96% of patients. Oral temperature was normal in 82% of patients. The authors conclude that a normal white cell count should not deter one from taking appropriate action to mitigate the propagation of a potentially limb-threatening foot infection.

Prospective study of bone, indium-111-labeled white blood cell, and gallium-67 scanning for the evaluation of osteomyelitis in the diabetic foot

Twenty-two adult diabetic patients with clinical suspicion of foot and/or ankle infection were prospectively evaluated using radiography, technetium-99m methylene diphosphonate bone scanning (99mTc), indium-111-labeled leukocyte scanning (111In), and gallium-67 scanning (67Ga) to determine the presence of clinically suspected osteomyelitis. Biopsy for culture and histology was performed in 16 patients. The diagnosis of osteomyelitis was confirmed by biopsy in 12 patients. The remaining 10 patients had no evidence of osteomyelitis with long-term follow-up. 99mTc was shown to be of limited valued when used alone in these patients with peripheral neuropathy. 67Ga, either alone or in combination with 99mTc bone scanning, was of little diagnostic value and gave no additional information that was not available from 111In. The combination of three-phase 99mTc and 111In had the highest diagnostic efficacy (100% sensitivity, 80% specificity, and 91% accuracy), followed closely by 111In alone (100% sensitivity, 70% specificity, and 86% accuracy). We conclude that for adult diabetic patients with clinical suspicion of osteomyelitis but no radiographic findings of that disease, 111In alone is an appropriate nuclear medicine evaluation for ruling out infection if it is negative. However, if an area of 111In white blood cell uptake is present, a "simultaneous" 99mTc is often helpful in providing the anatomic correlation to differentiate osteomyelitis from infection that is limited to soft tissue.

Imaging the diabetic foot

Early and accurate diagnosis of infection or neuropathy of the diabetic foot is the key to successful management. Angiopathy leads to ischemia which, in combination with peripheral neuropathy, predisposes to pedal skin ulceration, the precursor of osteomyelitis. Chronic hyperglycemia promotes production of glycosylated end products which accumulate on endothelial proteins, causing ischemia of the vasa nervorum. When combined with axonal degeneration of the sensory nerves, the result is hypertrophic neuroarthropathy. Should the sympathetic nerve fibers also be damaged, the resultant loss of vasoconstrictive impulses leads to hyperemia and atrophic neuroarthropathy. Plain radiography, although less sensitive than radionuclide, magnetic resonance (MR), and computed tomographic examinations, should be the initial procedure for imaging suspected osteomyelitis in the diabetic patient. If the radiographs are normal but the clinical suspicion of osteomyelitis is strong, a three-phase 99mTc-MDP scan or MR imaging is recommended. An equivocal 99mTc-MDP scan should be followed by MR imaging. To exclude osteomyelitis at a site of neuroarthropathy, a 111In white blood cell scan is preferable. To obtain a specimen of bone for bacteriological studies, percutaneous core biopsy is the procedure of choice, with the entrance of the needle well beyond the edge of the subjacent ulcer.

Multimodality imaging of osteomyelitis

Early diagnosis of osteomyelitis continues to be a clinical problem. Multiple imaging modalities are being used for the diagnosis of osteomyelitis, but none of them is ideal for all cases. The choice of modality depends on several factors based on an understanding of the pathophysiologic aspects of different forms of osteomyelitis. After a brief introduction outlining some basic principles regarding the diagnosis of osteomyelitis, pathophysiologic aspects are reviewed. Advantages and disadvantages of each imaging modality and their applications in different forms of osteomyelitis are discussed. The use of different imaging modalities in the diagnosis of special forms of osteomyelitis, including chronic, diabetic foot, and vertebral osteomyelitis, and osteomyelitis associated with orthopedic appliances and sickle cell disease is reviewed. Taking into account the site of suspected osteomyelitis and the presence or absence of underlying pathologic changes and their nature, an algorithm summarizing the use of various imaging modalities in the diagnosis of osteomyelitis is presented.