Medical imaging of the diabetic foot

Medical imaging of the diabetic foot entails a variety of imaging modalities. The diagnostic evaluation often includes a gamut of studies that include conventional radiography, CT, nuclear medicine scintigraphy, MRI, ultrasonography, and a newcomer, positron emission tomography combined with CT and leukocyte labeling. There is not yet "one best test" for sorting out the diagnostic dilemmas that are commonly encountered. Confirmation or exclusion of the frequent diagnosis of osteomyelitis often requires multiple studies, which are complementary to one another.     

Preoperative imaging of Charcot neuroarthropathy in diabetic patients: comparison of ring PET, hybrid PET, and magnetic resonance imaging

INTRODUCTION: The treatment of Charcot neuroarthropathy in the feet of diabetic patients has undergone fundamental changes in the last few years. Formerly, treatment was almost exclusively limited to nonoperative measures; since the late 1990s, however, current practice has shifted to early, stage-appropriate surgical therapy. The objective of this prospective study was to investigate the value of two types of positron emission tomography (PET) in the preoperative evaluation of diabetic patients with Charcot foot deformities. MATERIALS AND METHODS: Ring [(18)F]FDG (2-fluoro-2-deoxy-glucose) and hybrid PET were compared to magnetic resonance imaging (MRI). MRI, ring PET, and hybrid PET imaging were used as part of the preoperative evaluation of 16 patients with type II diabetes mellitus. The diagnosis of Charcot neuropathy of the foot requiring operative treatment had been made on the basis of clinical and radiographic criteria. RESULTS: Of 39 Charcot lesions confirmed at surgery, 37 were detected by ring PET, 30 by hybrid PET, and 31 by MRI. CONCLUSIONS: PET (ring or hybrid) can be used in the evaluation of patients with metal implants that would compromise the accuracy of MRI. Another advantage of PET is its ability to distinguish between inflammatory and infectious soft-tissue lesions, and between osteomyelitis and Charcot neuroarthropathy. The differentiation between Charcot neuroarthropathy and florid osteomyelitis provides the surgeon with important additional information that often is unavailable from MRI. Because it provides important additional data, ring PET may be preferable to radiography and MRI in the preoperative evaluation of patients with Charcot neuroarthropathy of the foot. Hybrid PET, because of its poorer resolution compared to ring PET, appears less suitable for routine clinical application.     

Update on functional imaging in the evaluation of diabetic foot infection

Diabetic foot infection is a preventable complication of diabetes mellitus. It is an essential component of diabetic foot disease, which is characterised by a triad of neuropathy, ischaemia and infection. These factors may lead to foot ulceration, sepsis and amputation resulting in increased morbidity and poor quality of life. Confirming or excluding infection can be difficult especially when routine laboratory tests and plain radiographs are inconclusive. Early diagnosis and localization of diabetic foot infection is extremely important to institute timely, appropriate therapy. Structural imaging using computed tomography and magnetic resonance imaging all have individual applications towards the diagnostic workup of this condition but have their own limitations. Scintigraphic detection is based on physiochemical changes and hence provides a functional evaluation of bone pathology.We describe the evolution of functional nuclear medicine imaging including immunoscintigraphy in diabetic foot infection and highlight current applications of physiological 18-Fluoro-deoxyglucose positron emission tomography (18-FDG-PET) and computed tomography (18-FDG-PET/CT) in such patients.18-FDG-PET/CT is a promising modality for imaging diabetic foot infection. Future studies will allow standardisation of technological details and options of 18-FDG-PET/CT interpretation in diabetic foot infection.     

Diagnostic performance of Fluorine-18-Fluorodeoxyglucose positron emission tomography for the diagnosis of osteomyelitis related to diabetic foot: A systematic review and a meta-analysis

ObjectiveTo systematically review and meta-analyse published data about the diagnostic performance of Fluorine-18-Fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) and PET/computed tomography (PET/CT) in osteomyelitis related to diabetic foot.MethodsA comprehensive literature search of studies on ¹⁸F-FDG-PET and PET/CT in patients with diabetic foot was performed. Pooled sensitivity, specificity, positive and negative likelihood ratio (LR+ and LR?) and diagnostic odds ratio (DOR) and area under the summary ROC curve of ¹⁸F-FDG-PET and PET/CT in patients with osteomyelitis related to diabetic foot were calculated.ResultsNine studies comprising 299 patients with diabetic foot were included in the qualitative analysis (systematic review) and discussed. The quantitative analysis (meta-analysis) of four selected studies provided the following results on a per patient-based analysis: sensitivity was 74% [95% confidence interval (95%CI): 60–85%], specificity 91% (95%CI: 85–96%), LR+ 5.56 (95%CI: 2.02–15.27), LR? 0.37 (95%CI: 0.10–1.35), and DOR 16.96 (95%CI: 2.06–139.66). The area under the summary ROC curve was 0.874.ConclusionsIn patients with suspected osteomyelitis related to diabetic foot ¹⁸F-FDG-PET and PET/CT demonstrated a high specificity, being potentially useful tools if combined with other imaging methods such as MRI. Nevertheless, the literature focusing on the use of ¹⁸F-FDG-PET and PET/CT in this setting remains still limited.     

Impact of magnetic resonance imaging on the management of diabetic foot infections

This combined retrospective/prospective study evaluated the value of magnetic resonance imaging (MRI) in 18 diabetic patients with apparent foot infections. The goal was to define the impact of MRI on directing the expedient and accurate surgical intervention so important in achieving optimal preservation of limb tissue and function. We found that MRI provides a rapid and reliable means of "viewing" the diabetic foot. Unsuspected or poorly localized abscess cavities can be pinpointed for thorough drainage with minimal exploration. An abscess can be differentiated from cellulitis or osteomyelitis. Moreover, persistent fever following drainage of a foot abscess can be reliably evaluated via MRI, obviating the need for empiric surgical reexploration. This exciting noninvasive imaging technique leads to the most accurate surgical drainage of foot abscesses and, at the same time, can prevent unnecessary surgical exploration of the tenuous diabetic foot.     

Magnetic Resonance Imaging of Diabetic Foot Osteomyelitis: Imaging Accuracy in Biopsy-Proven Disease

Magnetic resonance imaging (MRI) is the recommended diagnostic imaging technique for diabetic foot osteomyelitis (DFO). The gold standard to diagnose osteomyelitis is bone biopsy with a positive culture and/or histopathology finding consistent with osteomyelitis. The purpose of this study is to assess the accuracy of MRI readings in biopsy-proven diabetic foot osteomyelitis with a second read done by a blinded, expert musculoskeletal radiologist. A retrospective chart review of 166 patients who received a bone biopsy to confirm the diagnosis of a suspected DFO at a large county hospital between 2010 and 2014. A second, blinded musculoskeletal radiologist reviewed the images for accuracy, once the official reading was recorded. Imaging results were correlated with the final diagnosis of osteomyelitis determined by bone biopsy. In 17 of 58 patients (29.3%), the diagnosis of DFO by MRI was not confirmed by bone biopsy. There were 12 false positives and 5 false negatives. After the second expert read, there were 5 false positives and 4 false negatives. The overall accuracy was 84% for the second read. Our study demonstrated results comparable to the previously reported meta-analysis findings. There is a clear variation on the read of MRI that could lead to an incorrect diagnosis of DFO. An integrated approach with evaluation of clinical findings, communication with radiologist about the MRI results when indicated, and bone biopsy is warranted for accurate diagnosis management of DFO.     

Diagnostic imaging of musculoskeletal infection. Roentgenography; gallium, indium-labeled white blood cell, gammaglobulin, bone scintigraphy; and MRI.

A great deal of effort has been made to evaluate and define the role of various diagnostic imaging techniques in various clinical settings that complicate the diagnosis of osteomyelitis. Except possibly in neonates, bone scintigraphy remains generally recommended when there has been no previous osseous involvement. In other cases of chronic disease, previous fracture or trauma, prosthesis, and diabetic foot, In-WBC scintigraphy is generally accepted as an appropriate imaging technique. MRI will play an increasingly important role in diagnosing osteomyelitis and may prove to be an important adjunct in these cases. Research continues to improve our current diagnostic armamentarium. In-IgG appears to avoid practical deficiencies encountered with 67Ga and In-WBC; it remains to be seen what role this agent will play in routine clinical practice. All agents to date image inflammation, not infection, and most require delayed imaging sessions, usually at 24 hours. These shortcomings necessitate further research to develop new radiotracers that can provide useful images within several hours and that are specific for infection, perhaps ultimately delineating the particular microorganism involved.     

Statistical reliability of bone biopsy for the diagnosis of diabetic foot osteomyelitis

Bone biopsy is often referred to as the reference standard for the diagnosis of diabetic foot osteomyelitis (OM), and it also serves as an important interventional tool with respect to diabetic foot infections and limb salvage. However, the phrase bone biopsy lacks a standardized definition, and the statistical reliability of the pathologic diagnosis has not been previously examined. The objective of the present study was to quantify the reliability of the histopathologic analysis of bone with respect to the diagnosis of diabetic foot OM. Four pathologists, kept unaware of the previous pathology reports and specific patient clinical characteristics, retrospectively reviewed 39 consecutive tissue specimens and were informed only that it was "a specimen of bone taken from a diabetic foot to evaluate for OM." As a primary outcome measure, the pathologists were asked to make 1 of 3 possible diagnoses: (1) no evidence of OM, (2) no definitive findings of OM, but cannot rule it out, or (3) findings consistent with OM. There was complete agreement among all 4 pathologists with respect to the primary diagnosis in 13 (33.33%) of the 39 specimens, with a corresponding kappa coefficient of 0.31. A situation of clinically significant disagreement, or in which at least 1 pathologist diagnosed "no evidence of OM," but at least 1 other pathologist diagnosed "findings consistent with OM," occurred in 16 (41.03%) of the specimens. These results indicate agreement below the level of a "reference standard" and emphasize the need for a more comprehensive diagnostic protocol for diabetic foot OM.     

Level of Agreement With a Multi-Test Approach to the Diagnosis of Diabetic Foot Osteomyelitis

Although bone biopsy has historically been considered the “gold standard” or “standard reference” for the diagnosis of diabetic foot osteomyelitis, some contemporary investigations have provided evidence against this as a single diagnostic test and in support of a combination of clinical, laboratory, and radiographic findings. The objective of this investigation was to measure the level of agreement between several commonly used forms of diagnostic testing for diabetic foot osteomyelitis. A retrospective chart review was performed of 50 consecutive patients admitted to a single tertiary healthcare center with the documented performance of 1) a clinical probe-to-bone test on hospital admission; 2) plain film radiographs prior to any surgical intervention; 3) magnetic resonance imaging prior to any surgical intervention; and an intraoperative excisional bone debridement performed, with samples sent for both 4) histologic analysis and 5) microbiologic analysis. A frequency count of agreement among these 5 tests was performed, and the interobserver (or inter-test) agreement was measured using the kappa statistic. We observed low levels of inter-test agreement between the 5 diagnostic tests (range 42.0%–62.0%), and levels of chance-corrected agreement were well below what would be considered appropriate for a “gold standard” or “standard reference.” Levels of the kappa statistic ranged from 0.0 to 0.220, with most inter-test comparisons falling in the “poor agreement” and “slight agreement” interpretation ranges. The highest level of agreement occurred between the plain film radiographs and magnetic resonance imaging (62.0% agreement and kappa statistic of 0.220). Although it is likely that a combination of clinical, radiographic, and laboratory tests provides the best diagnostic approach for diabetic foot osteomyelitis, the data provided herein indicate that the tests themselves might have high intrinsic levels of unreliability and that the specific combination of tests that might be best used remains unclear.     

Hybrid imaging with 99mTc‐WBC SPECT/CT to monitor the effect of therapy in diabetic foot osteomyelitis

This study sought to assess the utility of monitoring response to treatment of diabetic foot osteomyelitis (DFO) with Tc‐99m WBC‐labelled single photon emission computed tomography (SPECT/CT) imaging. This is a retrospective cohort study of 20 patients with DFO with sequential Tc‐99m WBC‐labelled SPECT/CT imaging. Radiologic findings of osteomyelitis were evaluated and imaging results were correlated with clinical outcomes subtracted from chart review. Successful treatment of osteomyelitis was defined by wound healing and/or lack of re‐admission for bone infection of the same site within 1 year. The sensitivity, specificity, positive predictive value and negative predictive value of SPECT/CT to determine osteomyelitis treatment remission were 90%, 56%, 69% and 83%, respectively. Tc‐99m WBC‐labelled SPECT/CT imaging may be useful to help determine treatment outcomes for DFO.     

Osteomyelitis in the diabetic foot: diagnosis and management

Neuropathic ulcerations and altered immune function place the diabetic patient at increased risk for polymicrobial osteomyelitis of the foot and ankle. The optimal method for evaluation and management of this difficult condition is controversial, and further studies are needed. Infected ulcers with exposed or palpable bone can be assumed to have underlying osteomyelitis. Although plain film should be ordered in each case, MRI is most often used for evaluation and surgical planning. Difficult cases, such as those associated with Charcot osteoarthropathy, may require labeled leukocyte scanning or bone biopsy to arrive at the diagnosis. A multidisciplinary team approach is best, allowing optimal treatment of all associated conditions that commonly affect patients with diabetes mellitus. Vascular evaluation and intervention are critical in the presence of vascular insufficiency or ischemia. Empiric, usually broad-spectrum antibiotics and meticulous local wound care may achieve remission of mild to moderately severe infections and should be included in all treatment regimens. Severe, infections, ischemia, or sepsis requires an aggressive surgical approach. Bone resection, correction of deformity, or amputation often are necessary and should be done with the goal of salvaging a functional foot.     

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.     

Interdisciplinary treatment of diabetic foot syndrome

The amputation rate in patients with diabetic foot syndrome (DFS) in Germany is still as high as 28,000 per year. Ischemia and osteomyelitis often complicate the DFS. Impaired wound healing frequently requires further surgery with a higher amputation level. The results of treating patients with DFS in our specialized foot care center were evaluated in order to assess our interdisciplinary strategy. Advanced diabetic foot wounds in patients with ischemia and osteomyelitis first require diagnostics concerning polyneuropathy, osteomyelitis, and blood supply. If peripheral arterial vessel disease is present, surgical revascularization by distal bypass grafting is the first and crucially important element of the interdisciplinary approach. Minor amputation or elective resection of the infected bone improves wound healing. Post-interventional care for wounds with secondary healing and prevention of new ulcers are provided in a foot care clinic specialized in diabetes. The clinical and radiological results of 77 patients who underwent this treatment algorithm including bypass surgery and bone resection within 1 year were collected using a standardized questionnaire. Those results were subjected to a historical comparison. Only three patients needed further intervention because of persisting ulcers and osteomyelitis. The frequency of major amputations in all patients with DFS and ischemia combined with osteomyelitis was low (10.3%). This interdisciplinary concept of treatment guarantees a high healing rate in patients even with osteomyelitis and ischemia and allows the reduction of the rate of major amputations. The data obtained allow a fact-based design for future studies.     

Imaging in pelvic osteomyelitis: support for early magnetic resonance imaging

BACKGROUND: Children with pelvic osteomyelitis may present with symptoms that are nonspecific. Conventional imaging modalities including plain radiographs, ultrasound, technetium bone scan, and computed tomography rarely demonstrate pathology that is diagnostic of this condition. As a result, accurate diagnosis is often delayed, and children may undergo surgical diagnostic or therapeutic procedures that may be avoided. We report the radiographic and magnetic resonance imaging (MRI) findings in 23 children admitted with a suspected diagnosis of pelvic osteomyelitis. We are presenting imaging findings in children with suspected pelvic osteomyelitis with emphasis on MRI abnormalities and to propose an anatomical classification based on the patterns of pelvic involvement. METHODS: The medical records and imaging reports of all patients admitted to our institution with a history and physical examination suggestive of pelvic osteomyelitis between July 31, 1992, and March 10, 2003 were reviewed. Criteria were defined for the diagnosis of pelvic osteomyelitis based on criteria used by Farley et al in 1985. Specific attention was paid to the imaging strategies used and the influence of each radiographic method on the ultimate diagnosis. RESULTS: Abnormalities on the MRI included soft tissue inflammation and bone edema. These findings were bright on T2 and short inversion time Short T1 inversion recovery (STIR) images and enhanced after gadolinium administration. Five distinct patterns of pelvic involvement were observed, each corresponding to a cartilaginous epiphysis or apophysis. These were the sacroiliac joint, triradiate cartilage, pubic symphysis, ischium, and iliac apophysis. One patient had a noninfectious cause of presentation with a deep vein thrombosis, whereas another was diagnosed with Hodgkin lymphoma in addition to osteomyelitis of the ischium. CONCLUSIONS: Magnetic resonance imaging is a sensitive technique for evaluation of pyogenic infections involving the pelvis. In patients presenting with clinical findings and laboratory studies suggesting an infectious process, MRI with gadolinium enhancement should be performed as an early study. Magnetic resonance imaging is also effective in identifying other conditions that may resemble pelvic osteomyelitis.     

Cyst and cystlike lesions of the foot

A variety of cyst and cystlike lesions may present in the osseous structures of the foot. Such lesions are infrequent in their occurrence, and often cannot be diagnosed on the basis of radiographic appearance. In addition to the morphologic data that can be derived from evaluation of standard radiographs, other diagnostic radiographic studies such as tomography, CT scanning, radionuclide bone imaging, angiography, or other studies may be required to ascertain the nature and extent of cystlike lesions of the foot. This is dependent on histopathologic information derived from biopsy. A variety of cyst and cystlike lesions of the foot are presented with a review of their basic morphology and histopathologic, clinical, and prognostic characteristics.     

Efficacy of Magnetic Resonance Imaging in Diagnosing Diabetic Foot Osteomyelitis in the Presence of Ischemia

Magnetic resonance imaging (MRI) has been recognized as the most accurate imaging modality for the detection of diabetic foot osteomyelitis. However, how accurately MRI displays the extent of diabetic foot osteomyelitis in the presence of ischemia is still unclear. We retrospectively compared the preoperative MRI findings with the results of histopathologic examinations of resected bones and studied the efficacy of MRI in the diagnosis of diabetic foot osteomyelitis of different etiologies. A total 104 bones from 18 foot ulcers in 16 diabetic patients (10 men and 6 women; age range 42 to 84 years) treated by surgical intervention from 2008 to 2012 was examined. In 8 neuropathic ulcers, 29 bones were accurately diagnosed in detail using MRI, even those with severe soft tissue infection. Of 75 bones in 10 ischemic ulcers, only 7 bones evaluated by MRI after revascularization were diagnosed accurately; the other 68 could not be diagnosed because of unclear or equivocal MRI findings. On histopathologic examination, all the bones were found to be infected through the bone cortex by the surrounding infected soft tissue, not directly by articulation. Overall, preoperative MRI is effective in the diagnosis of neuropathic ulcers, but less so of ischemic ones.     

The Optimized Evaluation of Diabetic Foot Infection by Dual Isotope SPECT/CT Imaging Protocol

Sequential Tc-99m hydroxymethylene-diphosphonate (HDP) 3-phase bone (BS) and In-111 leukocyte scanning (WBCS) have been frequently used to evaluate the diabetic foot, as nonosteomyelitis BS uptake is repeatedly observed and osteomyelitis (OM) in WBCS is often uncertain without BS correlation. Additionally, both modalities are limited in lesion localization because of low resolution and lack of anatomic details. We investigated a method that combined BS/WBCS, and if needed, WBCS/bone marrow scanning (BMS) using SPECT/CT to accurately diagnose/localize infection in a practical protocol. Blood flow/pool images were obtained followed by WBC reinjection and next day dual isotope (DI) BS/WBCS planar and SPECT/CT. BMS/WBCS SPECT/CT (step 2 DI) was obtained on the following day when images were suspicious for mid/hindfoot OM. Diagnosis accuracy and confidence were judged for the various imaging combinations. Diagnosis was classified as OM, soft tissue infection (STI), both OM/STI, and other/no bony pathology by microbiology/pathology or follow-up. Distinction between various diagnostic categories and overall OM diagnostic accuracy in 213 patients were higher for DI than WBCS or BS alone, and for DI SPECT/CT than DI planar or SPECT only. Diagnostic confidence/lesion site was significantly higher for DI SPECT/CT than other comparative imaging methods. In a group of 97 patients with confirmed microbiologic/pathologic diagnosis, similar results were attained. Step 2 DI SPECT/CT performed in 67 patients further improved diagnostic accuracy/confidence. DI SPECT/CT is a highly accurate modality that considerably improves detection and discrimination of STI and OM while providing precise anatomic localization in the diabetic foot. This combined imaging technique promises to beneficially impact diabetic patient care.     

Nuclear medicine imaging in podiatric disorders

Radionuclide scanning is a valuable diagnostic tool based on metabolic and anatomic imaging. When used in the appropriate clinical setting, radionuclide imaging is a sensitive, minimally invasive imaging modality that detects and differentiates skeletal from nonskeletal pathology in the painful foot. Isotopic scanning is of particular value in the evaluation of the diabetic foot and in the subsequent follow-up of response to therapy.     

An evidence based narrative review on treatment of diabetic foot osteomyelitis

ObjectiveThe diagnosis of diabetic food infection is usually clinical, and its severity is related to location and depth of the lesion, and the presence of necrosis or gangrene. Osteomyelitis of the foot and ankle can be extremely debilitating, and, in the preantibiotic era acute staphylococcal osteomyelitis carried a mortality rate of 50%. The microbiology of diabetic foot osteomyelitis (DFO) is usually polymicrobial. Indeed, gram-negative and gram-positive bacilli can be identified using molecular techniques applied to bone biopsies compared to conventional techniques. The aim of the present study is to report a complete overview regarding medical and surgical management of diabetic foot osteomyelitis (DFO) in combination or alone.Materials and methodsWe performed a search in PubMed and Scopus electronic databases (up to January 2019) of articles assessing the epidemiology, diagnostic strategy and pharmacological treatment of diabetic foot infection. In the search strategy, we used various combinations of the following key terms: infection, orthopaedic, diabetic foot, management, DFO.ResultsThis article discusses the definition, epidemiology, microbiological assessment, clinical evaluation, pharmacological and surgical management and a comparison between them, of DFO. After the initial literature search and removal of duplicate records, a total of 756 potentially relevant citations were identified. After a further screening and according to the inclusion criteria, a total of 65 articles were included in the present review.ConclusionThe association of antibiotic and surgical therapy seems to be more effective compared to each one alone. The lack of comparison studies and randomized controlled trials makes it difficult to give information about the efficacy of the different management therapies.     

Osteomyelitis and osteoarthropathy in diabetic foot]

Differentially diagnostic, clinical and radiological criteria were proposed, basing on experience of examination and treatment of 56 patients with osteomyelitis in syndrome of diabetic foot and of 28--with an acute course of diabetic osteoarthropathy.