Magnetic resonance imaging for the diagnosis of osteomyelitis in the diabetic patient with a foot ulcer

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.

Update on MRI findings of osteomyelitis of long bones in the adult population

OBJECTIVES

To evaluate the usefulness of new and established MRI signs of osteomyelitis in long bones in adults.

METHODS

All patient records over a 9-year period with clinical or MRI suspicion for osteomyelitis were retrospectively reviewed, using strict criteria for proof of infection. Two musculoskeletal radiologists independently reviewed the MRIs of proven osteomyelitis.

RESULTS

Out of 45 MRIs of confirmed osteomyelitis, 2 MRIs (4%) did not show confluent low-signal intensity on T1-weighted images, but all showed confluent high-signal intensity on T2-weighted images. Central hypoenhancing regions of marrow without abscess formation were found in 15-18/35 (43-51%) cases where gadolinium was given. We often found multiple foci of marrow replacement in the same bone. The areas of marrow involvement often had an irregular contour. Penumbra sign, marrow fat globules, and sequestra were uncommon.

CONCLUSION

Multiple foci of bone marrow signal abnormalities, an irregular contour of marrow abnormality, and central marrow hypoenhancement without abscess are common signs of osteomyelitis of long bones in adults. Confluent low T1-signal intensity is not always present.

Assessing the optimal imaging modality in the diagnosis of jaw osteomyelitis. A meta-analysis

Osteomyelitis is an inflammatory infectious disease that affects bone and bone marrow. Histopathology remains the gold standard method for diagnosis, but imaging modalities also play an important role. We systematically reviewed five articles with comparative studies on plain films, computed tomography (CT) scan, magnetic resonance imaging (MRI), cone beam computed tomography (CBCT), positron emission tomography (PET), single photon-emission computed tomography (SPECT), scintigraphy, and SPECT/CT. Scintigraphy and SPECT/CT has the highest sensitivity of 100%. PET is only to be used in cases of follow up. Orthopantomography (OPG) is the most common initial diagnostic tool despite its low sensitivity. CT provides the necessary specificity needed for radionuclide imaging, which has the highest negative predictive value of 100% and a positive predictive value >95%. SPECT/CT with 100% sensitivity and 85% specificity can be considered as the imaging modality of choice for initial diagnosis and follow up.

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.

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.

Correlation of Systemic Inflammatory Markers With Radiographic Stages of Charcot Osteoarthropathy

BACKGROUND

Charcot osteoarthropathy (COA) is characterized by a progressive destruction of bone and joint associated with neuropathy and is most common in the foot and ankle. Clinical manifestation of COA is frequently indistinguishable from other causes of pain, swelling, and erythema of the affected extremity, in particular, infection. Diagnosis of COA can be challenging in particular in early stages where radiographic changes are sparse. The presence of elevated systemic inflammatory parameters in the context of suspected infection may delay early diagnosis and treatment of COA. The aim of this retrospective analysis was to assess whether elevated systemic inflammatory parameters may be present, in particular in early stages of COA and thus not be used as an exclusion criterion for the diagnosis of COA.

METHODS

Forty-two patients (mean age 48.2 ± 9.4 years, 36 male, 6 female) with a diagnosis of unilateral COA were the subject of this retrospective study. The diagnosis of COA was confirmed by plain radiographs, magnetic resonance imaging and clinical course. Systemic inflammatory parameters were recorded at the time of referral. Acute stages (stages 0 and 1) were treated with a total contact cast (TCC) and protected weight bearing for a minimum of 6 weeks. For chronic stages (stages 2 and 3) custom-made shoes were prescribed. The feet were stratified into "acute" (Eichenholz stages 0 and 1) and "subacute/chronic" (Eichenholz stages 2 and 3) groups.

RESULTS

Statistically significant differences were observed for all recorded systemic inflammatory parameters (C-reactive protein level, WBC count, erythrocyte sedimentation rate) between the acute and subacute/chronic groups. No statistical difference was observed considering the anatomic pattern of involvement.

CONCLUSION

The present study demonstrated that elevated systemic inflammatory parameters may be present in COA and can further be used to distinguish between acute and subacute stages of COA, based on the Eichenholtz classification. Thus, we suggest that elevated inflammatory markers should not be considered an exclusion criterion for the diagnosis of COA.

LEVEL OF EVIDENCE

Level III, retrospective comparative series.

Magnetic resonance imaging of diabetic foot complications

This pictorial review aims to illustrate the various manifestations of the diabetic foot on magnetic resonance (MR) imaging. The utility of MR imaging and its imaging features in the diagnosis of pedal osteomyelitis are illustrated. There is often difficulty encountered in distinguishing osteomyelitis from neuroarthropathy, both clinically and on imaging. By providing an accurate diagnosis based on imaging, the radiologist plays a significant role in the management of patients with complications of diabetic foot.

Assessing diabetic foot osteomyelitis remission with white blood cell SPECT/CT imaging

AIMS

Diabetic foot osteomyelitis is an important risk factor of lower limb amputation. Antibiotic therapy is often effective in preventing surgery. However, the duration of antibiotic therapy is difficult to define in the absence of a marker to diagnose osteomyelitis remission at the end of the treatment. In this study, we assessed the diagnostic performance of white blood cell SPECT/CT imaging for evaluating osteomyelitis remission.

PATIENTS AND METHODS

Twenty-nine out of 42 episodes of diabetic foot osteomyelitis seen between December 2009 and April 2012 had radiographs, a three-phase bone scintigraphy and a white blood cell SPECT/CT at the end of antibiotic therapy. They were treated with antibiotics alone and considered in clinical remission. White blood cell SPECT/CT results were considered positive when abnormal uptake in the osteomyelitis location was identified. Osteomyelitis remission was defined by the absence of an osteomyelitis relapse after 12 months' follow-up.

RESULTS

A negative white blood cell SPECT/CT was seen for 22 episodes of osteomyelitis. All of them were in remission. A positive white blood cell SPECT/CT was observed for seven episodes. A relapse occurred in five episodes (71.5%) after a median duration of 4 months (2-7 months). Sensitivity, specificity, positive predictive value and predictive negative value in predicting osteomyelitis relapse after the discontinuation of antibiotic treatment were, respectively, for radiographs 80%, 33%, 20% and 89%; for three-phase bone scintigraphy 100%, 12.5%, 15.5% and 100%; and for the white blood cell SPECT/CT 100%, 91.5%, 71.5% and 100%.

CONCLUSION

Negative uptake on white blood cell SPECT/CT is a good marker for diagnosis of diabetic foot osteomyelitis remission and might be very useful in guiding antibiotic therapy.

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.

Diabetic foot infections with osteomyelitis: efficacy of combined surgical and medical treatment

Diabetic foot infections are a high risk for lower extremity amputation in patients with dense peripheral neuropathy and/or peripheral vascular disease. When they present with concomitant osteomyelitis, it poses a great challenge to the surgical and medical teams with continuing debates regarding the treatment strategy. A cohort prospective study conducted between October 2005 and October 2010 included 330 diabetic patients with osteomyelitis mainly involving the forefoot (study group) and 1,808 patients without foot osteomyelitis (control group). Diagnosis of osteomyelitis was based on probing to bone test with bone cultures for microbiological studies and/or repeated plain radiographic findings. Surgical treatment included debridement, sequestrectomy, resections of metatarsal and digital bones, or toe amputation. Antibiotics were started as empirical and modified according to the final culture and sensitivities for all patients. Patients were followed for at least 1 year after wound healing. The mean age of the study group was 56.7 years (SD = 11.4) compared to the control group of 56.3 years (SD = 12.1), while the male to female ratio was 3:1. At initial presentation, 82.1% (n=271) of the study group had an ulcer penetrating the bone or joint level. The most common pathogens were Staphylococcus aureus (33.3%), Pseudomonas aeruginosa (32.2%), and Escherichia coli (22.2%) with an almost similar pattern in the control group. In the study group, wound healing occurred in less than 6 months in 73% of patients compared to 89.9% in the control group. In the study group, 52 patients (15.8%) had a major lower extremity amputation versus 61 in the control group (3.4%) (P=0.001). During the postoperative follow-up visits, 12.1% of patients in each group developed wound recurrence. In conclusion, combined surgical and medical treatment for diabetic foot osteomyelitis can achieve acceptable limb salvage rate and also reduce the duration of time to healing along with the duration of antibiotic treatment and wound recurrence rate.

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.

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.

Imaging of the Charcot foot

Charcot foot is a serious problem that causes considerable morbidity and may lead to limb loss. Arriving at a definitive diagnosis can be challenging. Given the progressive, destructive nature of Charcot's arthropathy, this delay can result advancing deformity, ulceration, infection, and place the limb at risk for amputation. Although clinical signs and symptoms and historical information are crucial, this article focuses on the imaging modalities that can aid practitioners in arriving at an early diagnosis, and how to differentiate Charcot's arthropathy from osteomyelitis of the feet.

Diabetic foot osteomyelitis

Bone infection in the diabetic foot is always a complication of a preexisting infected foot wound. Prevalence can be as high as 66%. Diagnosis can be suspected in two mains conditions: no healing (or no depth decrease) in spite of appropriate care and off-loading, and/or a visible or palpated bone with a metal probe. The first recommended diagnostic step is to perform (and if necessary to repeat) plain radiographs. After a four-week treatment period, if plain radiographs are still normal, suspicion for bone infection will persist in case of bad evolution despite optimized management of off-loading and arterial disease. It is only in such cases that other diagnosis methods than plain radiographs must be used. Staphylococcus aureus is the most common pathogen cultured from bone samples, followed by Staphylococcus epidermidis. Among enterobacteriaceae, Escherichia coli, Klebsiella pneumonia and Proteus sp. are the most common, followed by Pseudomonas aeruginosa. Surprisingly, bacteria usually considered contaminant (as coagulase negative staphylococci (CNS) and Corynebacterium sp.) have been documented to be pathogens in the osteomyelitis of diabetic foot. Traditional approach to treatment of chronic osteomyelitis was by surgical resection of infected and necrotic bone. But new classes of antibiotics have both the required spectrum of activity and the capacity to penetrate and concentrate in the infected bone. Recently, several observations of osteomyelitis remission following non-surgical management with a prolonged course of antibiotics have been published. Lastly, combined approach with local bone excision and antibiotics has been proposed. Prospective trials should be undertaken to determine the relative roles of surgery and antibiotics in managing diabetic foot osteomyelitis.

Unsuspected osteomyelitis is frequent in persistent diabetic foot ulcer and better diagnosed by MRI than by 18F-FDG PET or 99mTc-MOAB

AIM

Prevalence, optimal diagnostic approach and consequences of clinically unsuspected osteomyelitis in diabetic foot ulcers are unclear. Early diagnosis of this infection may be crucial to ensure correct management.

METHODS

We conducted a prospective study in 20 diabetic patients with a chronic foot ulcer (>8 weeks) without antibiotic pretreatment and without clinical signs for osteomyelitis to assess the prevalence of clinically unsuspected osteomyelitis and to compare the value of magnetic resonance imaging (MRI), 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) and 99mTc-labelled monoclonal antigranulocyte antibody scintigraphy (99mTc-MOAB). Those with suggestive scans underwent bone biopsy for histology (n = 7).

RESULTS

Osteomyelitis was confirmed by biopsy in seven of the 20 clinically unsuspected foot ulcers. Presence of osteomyelitis was not related to age, ulcer size, ulcer duration, duration of diabetes or HbA1c. C-reactive protein was slightly elevated in patients with osteomyelitis (35.1 +/- 16.0 mg L(-1) vs. 12.2 +/- 2.6 mg L(-1) in patients with and without osteomyelitis respectively; P = 0.07). MRI was positive in six of the seven patients with proven osteomyelitis, whereas 18F-FDG PET and 99mTc-MOAB were positive only in (the same) two patients. Of the seven patients with osteomyelitis, five had lower limb amputation and in one patient the ulcer was persisting after 24 months of follow-up. In contrast, of the 13 patients without detectable signs of osteomyelitis on imaging modalities only two had lower limb amputation and two persisting ulcers.

CONCLUSIONS

Clinically unsuspected osteomyelitis is frequent in persisting foot ulcers and is a high risk factor for adverse outcome. MRI appears superior to 18F-FDG PET and 99mTc-MOAB in detecting foot ulcer-associated osteomyelitis and might be the preferred imaging modality in patients with nonhealing diabetic foot ulcers.

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.

The diabetic foot: Charcot joint and osteomyelitis

Foot problems are common causes of disability in diabetic patients with as many as 25% expected to develop severe foot or leg problems during their lifetimes. Although skin ulceration is the most frequent problem, bones may also be involved in two different clinical conditions: osteomyelitis and Charcot osteoarthropathy. Osteomyelitis causes complications in up to one third of diabetic foot infections and is due to direct contamination from a soft-tissue ulcer. Osteoarthropathy Charcot foot is a chronic and progressive disease of the bone and joints. Both osteomyelitis and Charcot joint are conditions with an increased risk of lower limb amputation, both may have a successful outcome when recognized and treated in the early stages. The major diagnostic difficulty is in distinguishing bone infection (osteomyelitis) from non-infectious neuropathic bony disorders as in osteoarthropathy Charcot foot. An additional difficulty is found when a bone infection superimposes a Charcot osteopathy. This condition, which can be clinically suspected when foot ulceration appears in Charcot foot, needs to be diagnosed because it implies a different therapeutic strategy. This article aims to summarize both these two clinical conditions and give indications to make a timely and correct diagnosis.

Diagnosis and treatment of diabetic foot infections

EXECUTIVE SUMMARY: 1. Foot infections in patients with diabetes cause substantial morbidity and frequent visits to health care professionals and may lead to amputation of a lower extremity. 2. Diabetic foot infections require attention to local (foot) and systemic (metabolic) issues and coordinated management, preferably by a multidisciplinary foot-care team (A-II). The team managing these infections should include, or have ready access to, an infectious diseases specialist or a medical microbiologist (B-II). 3. The major predisposing factor to these infections is foot ulceration, which is usually related to peripheral neuropathy. Peripheral vascular disease and various immunological disturbances play a secondary role. 4. Aerobic Gram-positive cocci (especially Staphylococcus aureus) are the predominant pathogens in diabetic foot infections. Patients who have chronic wounds or who have recently received antibiotic therapy may also be infected with Gram-negative rods, and those with foot ischemia or gangrene may have obligate anaerobic pathogens. 5. Wound infections must be diagnosed clinically on the basis of local (and occasionally systemic) signs and symptoms of inflammation. Laboratory (including microbiological) investigations are of limited use for diagnosing infection, except in cases of osteomyelitis (B-II). 6. Send appropriately obtained specimens for culture before starting empirical antibiotic therapy in all cases of infection, except perhaps those that are mild and previously untreated (B-III). Tissue specimens obtained by biopsy, ulcer curettage, or aspiration are preferable to wound swab specimens (A-I). 7. Imaging studies may help diagnose or better define deep, soft-tissue purulent collections and are usually needed to detect pathological findings in bone. Plain radiography may be adequate in many cases, but MRI (in preference to isotope scanning) is more sensitive and specific, especially for detection of soft-tissue lesions (A-I). 8. Infections should be categorized by their severity on the basis of readily assessable clinical and laboratory features (B-II). Most important among these are the specific tissues involved, the adequacy of arterial perfusion, and the presence of systemic toxicity or metabolic instability. Categorization helps determine the degree of risk to the patient and the limb and, thus, the urgency and venue of management. 9. Available evidence does not support treating clinically uninfected ulcers with antibiotic therapy (D-III). Antibiotic therapy is necessary for virtually all infected wounds, but it is often insufficient without appropriate wound care. 10. Select an empirical antibiotic regimen on the basis of the severity of the infection and the likely etiologic agent(s) (B-II). Therapy aimed solely at aerobic Gram-positive cocci may be sufficient for mild-to-moderate infections in patients who have not recently received antibiotic therapy (A-II). Broad-spectrum empirical therapy is not routinely required but is indicated for severe infections, pending culture results and antibiotic susceptibility data (B-III). Take into consideration any recent antibiotic therapy and local antibiotic susceptibility data, especially the prevalence of methicillin-resistant S. aureus (MRSA) or other resistant organisms. Definitive therapy should be based on both the culture results and susceptibility data and the clinical response to the empirical regimen (C-III). 11. There is only limited evidence with which to make informed choices among the various topical, oral, and parenteral antibiotic agents. Virtually all severe and some moderate infections require parenteral therapy, at least initially (C-III). Highly bioavailable oral antibiotics can be used in most mild and in many moderate infections, including some cases of osteomyelitis (A-II). Topical therapy may be used for some mild superficial infections (B-I). 12. Continue antibiotic therapy until there is evidence that the infection has resolved but not necessarily until a wound has healed. Suggestions for the duration of antibiotic therapy are as follows: for mild infections, 12 weeks usually suffices, but some require an additional 12 weeks; for moderate and severe infections, usually 24 weeks is sufficient, depending on the structures involved, the adequacy of debridement, the type of soft-tissue wound cover, and wound vascularity (A-II); and for osteomyelitis, generally at least 46 weeks is required, but a shorter duration is sufficient if the entire infected bone is removed, and probably a longer duration is needed if infected bone remains (B-II). 13. If an infection in a clinically stable patient fails to respond to 1 antibiotic courses, consider discontinuing all antimicrobials and, after a few days, obtaining optimal culture specimens (C-III). 14. Seek surgical consultation and, when needed, intervention for infections accompanied by a deep abscess, extensive bone or joint involvement, crepitus, substantial necrosis or gangrene, or necrotizing fasciitis (A-II). Evaluating the limb's arterial supply and revascularizing when indicated are particularly important. Surgeons with experience and interest in the field should be recruited by the foot-care team, if possible. 15. Providing optimal wound care, in addition to appropriate antibiotic treatment of the infection, is crucial for healing (A-I). This includes proper wound cleansing, debridement of any callus and necrotic tissue, and, especially, off-loading of pressure. There is insufficient evidence to recommend use of a specific wound dressing or any type of wound healing agents or products for infected foot wounds. 16. Patients with infected wounds require early and careful follow-up observation to ensure that the selected medical and surgical treatment regimens have been appropriate and effective (B-III). 17. Studies have not adequately defined the role of most adjunctive therapies for diabetic foot infections, but systematic reviews suggest that granulocyte colony-stimulating factors and systemic hyperbaric oxygen therapy may help prevent amputations (B-I). These treatments may be useful for severe infections or for those that have not adequately responded to therapy, despite correcting for all amenable local and systemic adverse factors. 18. Spread of infection to bone (osteitis or osteomyelitis) may be difficult to distinguish from noninfectious osteoarthropathy. Clinical examination and imaging tests may suffice, but bone biopsy is valuable for establishing the diagnosis of osteomyelitis, for defining the pathogenic organism(s), and for determining the antibiotic susceptibilities of such organisms (B-II). 19. Although this field has matured, further research is much needed. The committee especially recommends that adequately powered prospective studies be undertaken to elucidate and validate systems for classifying infection, diagnosing osteomyelitis, defining optimal antibiotic regimens in various situations, and clarifying the role of surgery in treating osteomyelitis (A-III).

Evidence-Based Protocol for Diabetic Foot Ulcers

BACKGROUND

Diabetic foot ulcers are the single biggest risk factor for nontraumatic foot amputations in persons with diabetes. Foot ulcers occur in 12 to 25 percent of persons with diabetes and precede 84 percent of all nontraumatic amputations in this growing population. Because of the high incidence of foot ulcers, amputations remain a source of morbidity and mortality in persons with diabetes. Strict adherence to evidence-based protocols as described herein will prevent the majority of these amputations.

METHODS

The collective experience of treating patients with neuropathic diabetic foot ulcers in four major diabetic foot programs in the United States and Europe was analyzed.

RESULTS

The following protocol was developed for patients with diabetic foot ulcers: (1) establishment of good communication among the patient, the wound healing team, and the primary medical doctor; (2) comprehensive, protocol-driven care of the entire patient, including hemoglobin A1c, microalbuminuria, and cholesterol as well as early treatment of retinopathy, nephropathy, and cardiac disease; (3) weekly objective measurement of the wound with digital photography, planimetry, and documentation of the wound-healing process using the Wound Electronic Medical Record, if available; (4) objective evaluation of blood flow in the lower extremities (e.g., noninvasive flow studies); (5) débridement of hyperkeratotic, infected, and nonviable tissue; (6) use of systemic antibiotics for deep infection, drainage, and cellulitis; (7) off-loading; (8) maintenance of a moist wound bed; (9) use of growth factor and/or cellular therapy if the wound is not healing after 3 weeks with this protocol; and (10) consideration of the use of vacuum-assisted therapy in complex wounds.

CONCLUSIONS

In diabetic foot ulcers, availability of the above modalities, in combination with early recognition and comprehensive treatment, ensures rapid healing, minimizes morbidity and mortality rates, and eliminates toe and limb amputations in the absence of ischemia and osteomyelitis.

MRI of the diabetic foot: differentiation of infection from neuropathic change

The aim of this review is to illustrate the magnetic resonance imaging features that can help differentiate osteomyelitis from neuropathic osteoarthropathy in the foot.

Neuropathic arthropathy of the foot with and without superimposed osteomyelitis: MR imaging characteristics

PURPOSE

To determine retrospectively the magnetic resonance (MR) findings associated with pedal neuropathic arthropathy with and without superimposed osteomyelitis and to identify any useful discriminating features.

MATERIALS AND METHODS

Investigational review board approval was obtained and allowed review of records and images without informed consent. HIPAA compliance was observed. Contrast-enhanced MR images in patients with diabetic neuropathic arthropathy of the foot were examined by two reviewers in consensus. Affected joints were examined for marrow, articular, periarticular, and soft-tissue findings. Presence of superimposed osteomyelitis was documented. A subgroup that had undergone MR before infection was evaluated for comparison; chi(2) and t tests were used to evaluate the associations.

RESULTS

Of 128 neuropathic joints in 63 patients (24 female, 39 male; aged 31-78 years), 43 had superimposed osteomyelitis. Effusion was common in all neuropathic joints, but thin rim enhancement was more common in noninfected joints (62% vs 21%, P < .001) and diffuse joint fluid enhancement was more common with infection (47% vs 26%, P = .052). Subluxation, bone proliferation, fragmentation, and erosion were seen in both groups, but intraarticular bodies were more common in noninfected joints (53% vs 12%, P < .001). In the periarticular soft tissues, edema, enhancement, and ulceration were common in both groups. Fluid collections in the soft tissues were more commonly associated with infected joints (95% vs 48%, P < .001) and, when present next to an infected joint, were larger than those next to noninfected neuropathic joints (2.6 cm(2) [range, 0.3-8.6 cm(2)] vs 1.6 cm(2) [range, 1.0-2.4 cm(2)]). Soft-tissue fat replacement (68% vs 36%, P = .002) and sinus tracts (84% vs 0%, P < .001) were also more common with infection. In the marrow, periarticular signal intensity abnormality was common in both groups, but the extent was greater with infection. Subchondral cysts were seen almost exclusively in noninfected joints (76% vs 2%, P < .001). Similar results were obtained in the subgroup of 21 joints (15 patients) with both pre- and postinfection MR images.

CONCLUSION

Sinus tract, replacement of soft-tissue fat, fluid collection, and extensive marrow abnormality are MR imaging features indicating superimposed infection. Thin rim enhancement of effusion, presence of subchondral cysts, or intraarticular bodies indicate absence of infection.

T1-Weighted MRI Characteristics of Pedal Osteomyelitis

OBJECTIVE

The objective of our study was to better define the T1-weighted MRI characteristics of surgically proven pedal osteomyelitis.

CONCLUSION

Decreased T1 marrow signal in a geographic medullary distribution with a confluent pattern and concordance with fat-suppressed T2- and T1-weighted postcontrast signal abnormality was present in 100% of the surgically proven cases of pedal osteomyelitis. None of the patients with decreased T1 marrow signal in a subcortical distribution or in a hazy, reticulated pattern had surgically proven osteomyelitis regardless of the fat-suppressed T2-weighted or postcontrast T1-weighted findings.

Is this bone infected or not? Differentiating neuro-osteoarthropathy from osteomyelitis in the diabetic foot

Osteomyelitis (bone infection) and neuro-osteoarthropathy (Charcot arthropathy) are limb-threatening complications of diabetic neuropathy with very different therapies. Distinguishing between them may be difficult, but it is important. In Charcot arthropathy, noninfectious soft tissue inflammation accompanies rapidly progressive destruction, first of joints, then of bone. This occurs in a well-vascularized and severely neuropathic, but nonulcerated, foot. In osteomyelitis, chronic soft tissue ulceration precedes infection of bone, which may be physically exposed. Magnetic resonance imaging and bone biopsy are the preferred diagnostic tests, provided adequate technical and interpretive skills are available.

Diagnosing foot infection in diabetes

Infection represents the presence of an inflammatory response and tissue injury due to the interaction of the host with multiplying bacteria. The disease spectrum is a consequence of the variability in these interactions. Diabetes, because of its effects on the vascular, neurological, and immune systems, can compromise the local and systemic response to infection, potentially masking the typical clinical features and hindering diagnosis. The early recognition of infection, particularly osteomyelitis, is paramount in the management of diabetic foot disease. Careful clinical appraisal remains the cornerstone of the assessment. Hematologic, biochemical, and radiological investigations are important aids in assessing the severity of infection. Microbiological assessment, particularly in more severe infection, requires good-quality samples, combined with rapid transport in an appropriate medium and effective communication with the laboratory. A focused, systematic approach to the accurate diagnosis and treatment of infection, combined with careful monitoring, ensures the maintenance of optimal management.

Protocol for treatment of diabetic foot ulcers

Each year, 82,000 limb amputations are performed in patients with diabetes mellitus. The majority of these amputations could be avoided by following strict protocols. The collective experience treating patients with neuropathic diabetic foot ulcers of 4 major diabetic foot programs in the United States and Europe were analyzed. The following protocol has been developed for patients with diabetic foot ulcers: (1) measurement of the wound by planimetry; (2) optimal glucose control; (3) surgical debridement of all hyperkeratotic, infected, and nonviable tissue; (4) systemic antibiotics for deep infection, drainage, and cellulitis; (5) offloading; (6) moist-wound environment; and (7) treatment with growth factors and/or cellular therapy if the wound is not healing after 2 weeks with this protocol and a new epithelial layer is not forming. In addition, the pathogenesis of diabetic foot ulcers is discussed, as well as the associated costs and complications, including amputation. Debridement, wound-bed preparation, antibiotics, various types of dressings, biological therapies, growth factors, and offloading are described as treatment modalities for patients with diabetic foot ulcers. In diabetic foot ulcers, availability of the above modalities, in combination with early recognition and comprehensive treatment, ensure rapid healing and minimize morbidity, mortality, and costs, as well as eliminate amputation in the absence of ischemia and osteomyelitis.

New treatments for diabetic neuropathic foot ulceration: views from a wound healing unit

The management of diabetic foot ulceration remains problematic despite advances in treatments. The evidence for many treatments is lacking and clinical experience remains important. Current diabetic foot ulcer management and an evaluation of new therapies are discussed. Research in wound healing and diabetic foot disease can complement each other in accurately evaluating and treating diabetic foot ulceration. This would aid in formulating personalized therapies, tailoring treatments to optimize the ulcer healing environment.

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.

Prognostic value of 99m Tc leukocyte scintigraphy in diabetic pedal osteomyelitis

While leukocyte scintigraphy is accurate in detection of pedal osteomyelitis, there has been little data relating the technique to outcomes. We designed a trial to examine the prognostic value of sequential 99m Tc labeled leukocyte scans to establish the diagnosis of osteomyelitis and after three to four weeks of culture-guided antibiotic therapy. Twenty-three diabetic patients with proven pedal osteomyelitis (21/23) or persistent uptake (2/23) on the sequence of scans were studied. Five additional episodes of osteomyelitis developed in the group over the period of the study. Eleven patients demonstrated persistent uptake in the sequential scans. Nine progressed to amputation. The remaining two patients were biopsy-negative for infection, did not have cutaneous ulceration and were thought to have rapidly progressive arthropathy. Sequential leukocyte scintigraphy accurately predicts the need for amputation and can circumvent ineffective prolonged antibiotic therapy.

Intra-articular neuropathic fracture of the calcaneal body treated by open reduction and subtalar arthrodesis

A novel pattern of neuropathic intra-articular calcaneal fracture in a diabetic patient is described. This fracture combined proximal retraction of the tuberosity and body along with hindfoot collapse and plantar ulceration. Following control of the acute Charcot process with total contact casting, surgical reduction and subtalar arthrodesis was performed to stabilize the hindfoot and decrease the risk of recurrent ulceration. After healing, the patient successfully resumed ambulation and presently uses extra-depth shoes for daily activities. Despite the risks of surgical treatment, this difficult fracture may be treated operatively to maintain plantigrade alignment and offer limb salvage for the neuropathic patient.

Tibiocalcaneal arthrodesis for the management of severe ankle and hindfoot deformities

PURPOSE

The purpose of this investigation was to evaluate the outcome of tibiocalcaneal arthrodesis using an adolescent condylar blade plate for severe ankle and hindfoot deformities.

MATERIALS AND METHODS

We retrospectively reviewed the records of patients managed at our institutions between 1989 and 1996 whose tibiocalcaneal arthrodeses were performed with adolescent condylar blade plates and allograft bone. In these 30 patients (14 men, 16 women; average age, 53 years), the etiologies of the nonbraceable deformity included: diabetic neuroarthropathy with talar fragmentation and resorption (26), inflammatory arthritis (3), and posttraumatic avascular necrosis of the talus with collapse (1). Due to the severity of the deformity in 28 of these patients, the alternative treatment would have been amputation. Thirteen patients had undergone previous surgeries, eight had documented osteomyelitis, and 13 had ulcers ranging from 2 to 27 mm. At surgery, the remnants of the talus were removed. Morcellized bone graft mixed with tobramycin/vancomycin powder was inserted into the arthrodesis site and then fixed with a rigid plate. Intravenous antibiotics, followed by oral antibiotics, were given until wound healing and suture removal. Follow-up averaged 48 months (19 to 112 months).

RESULTS

Tibiocalcaneal fusion was achieved in 28/30 patients at an average of 16 weeks (12 to 18 weeks). Complications occurred in seven patients: two developed stress fractures of the tibia at the proximal end of the blade plate, three had superficial cellulitis that resolved with antibiotic therapy, and two had nonunions.

CONCLUSION

Tibiocalcaneal arthrodesis using an adolescent condylar blade plate and allograft bone can be a successful procedure in the patient with severe neuropathic ankle deformity and can achieve a stable plantigrade foot for limited community ambulation with relatively few complications.

Examination of the lower limb in high risk patients

When 'at risk' patients say that their feet are killing them, they may be right. Diabetes mellitus accounts for 50 to 70% of all nontraumatic amputations with a three year survival rate of those who undergo a lower limb amputation of 50%. Furthermore, when compared to the 'normal' foot, the 'at risk' foot is more likely to develop complications, thus it is vital to identify such 'at risk' individuals in an attempt to prevent the risk of deformity, ulceration, infection and/or necrosis/gangrene. The assessment involves history taking, the examination and further investigations, providing the necessary information to make a clinical diagnosis and identify 'at risk' groups. During the examination the foot-wear should be checked, nails and skin condition should be closely inspected and tests should be carried out for signs of peripheral neuropathy, ischaemia and venous/lymphatic deficiency. Other complications like deformity and increases in foot pressure may cause ulceration. Where ulcers are present, an in-depth systematic inspection is necessary. A thorough lower limb examination of high risk patients provides the necessary information to make a clinical diagnosis and plan preventative measures to avoid future complications.

Treatment of diabetic (neuropathic) foot ulcers with two-stage debridement and closure

We reviewed 33 patients with 37 wounds treated between November of 1991 and December of 1995 in the Wound Care Center. A two-stage debridement and closure technique for neuropathic foot ulcers was performed. Patients selected included those with obvious osteomyelitis and those who had failed nonsurgical treatment. The approach included initial surgical excision of the ulcer with biopsy, bone resection with biopsy, and deep culture. The second-stage procedure 4 to 8 days later included debridement of the wound and delayed closure. Intravenous antibiotic treatment using a central line was given postoperatively in patients with documented osteomyelitis for at least 6 weeks and in patients with infected soft tissues only for about 4 weeks. All patients remained nonweightbearing for 4 weeks; this was felt necessary to prevent separation of the wound edges. Four wounds in four patients failed to heal, and two of these went on to amputation. Satisfactory healing occurred in 29 of 33 patients and in 33 of 37 wounds. The authors conclude that two-stage surgical debridement and closure is an acceptable treatment in selected nonhealing diabetic (neuropathic) foot ulcers.

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.