Neuropathic osteoarthropathy with and without superimposed osteomyelitis in patients with a diabetic foot

Imaging of lower extremity infections: predisposing conditions, atypical infections, mimics, and differentiating features

Imaging evaluation for lower extremity infections can be complicated, especially in the setting of underlying conditions and with atypical infections. Predisposing conditions are discussed, including diabetes mellitus, peripheral arterial disease, neuropathic arthropathy, and intravenous drug abuse, as well as differentiating features of infectious versus non-infectious disease. Atypical infections such as viral, mycobacterial, fungal, and parasitic infections and their imaging features are also reviewed. Potential mimics of lower extremity infection including chronic nonbacterial osteomyelitis, foreign body granuloma, gout, inflammatory arthropathies, lymphedema, and Morel-Lavallée lesions, and their differentiating features are also explored.

Differential Diagnosis of Charcot Neuroarthropathy in Subacute and Chronic Phases: Unusual Diseases

Charcot Neuroarthropaty (CN) is a complication of diabetes with devastating consequences as it produces severe deformities in the foot developing in recurrent ulcers that rise the probability of amputation. There are several diseases mentioned in the literature that have to be considered for the differential diagnosis of CN, often related to the acute phase (gout, ankle sprain, inflammatory arthritis, cellulitis, venous thrombosis) but there is paucity of information related to the differential diagnosis in later stages (coalescence, remodeling) when there is deformity of the foot. Clinicians and diabetologists are not familiarized with orthopedic pathology and do not have in mind certain diseases that could mimic CN in the subacute or chronic phases and this can develop in a wrong diagnosis. It is important to make a correct diagnosis in patients with suspected CN not only in the acute phase but also in the chronic phase to establish an accurate treatment. This article is a review of the differential diagnosis of CN in subacute and chronic phases showing similarities and differences that can help clinicians and diabetologists to make an accurate diagnosis and treatment. We describe unusual diseases like tendon and muscles disorders, Frieberg's disease, complex pain regional syndrome, transient regional osteoporosis and osteomyelitis superimposed to CN and the main features of each one that could help in making a differential diagnosis.

Non-Enhancing Tissue on Diabetic Foot Magnetic Resonance Imaging in Relation to Osteomyelitis Investigation: Magnetic Resonance Imaging Performance, Pitfalls and Clinical Considerations

Background: Geographic non-enhancing zones in diabetic foot magnetic resonance imaging (MRI) were first described in 2002. No previous report has described the impact and clinical significance of geographic non-enhancing tissue seen in the evaluation of diabetic foot MRI. Purpose: To evaluate the prevalence of devascularization areas on contrast-enhanced MRI in diabetic patients suspected of having foot osteomyelitis, the impact on the performance of the MRI assessment, and the possible pitfalls. Methods: A retrospective study was conducted between January 2016 and December 2017 during which 72 CE-MRIs of 1.5 and 3T were reviewed by 2 musculoskeletal radiologists for the presence of non-enhancing tissue areas and for osteomyelitis. A blinded third party collected clinical data including pathology reports, revascularization procedures, and surgical interventions. The prevalence of devascularization was calculated. Results: Among the 72 CE-MRIs (54 men, 18 women; mean age 64), 28 demonstrated non-enhancing areas (39%). All but 6 patients were found to have been correctly diagnosed on imaging (3 false positives, 2 false negatives, and 1 non-diagnostic). A greater discordance was also observed between the radiological and pathological diagnoses in the MRIs which showed non-enhancing tissue. Conclusion: Non-enhancing tissue is found in a non-negligible portion of diabetic foot MRIs and affects its diagnostic performance when looking for osteomyelitis. The recognition of these areas of devascularization may be helpful for the physician in planning the best treatment option for the patient.

Imaging of the Diabetic Foot

Diabetic foot complications are increasingly prevalent in the world, leading to significant morbidity and driving up associated health care costs. Complex pathophysiology and suboptimal specificity of current imaging modalities have made diagnosis challenging, mainly in the evaluation of superimposed foot infection to underlying arthropathy or other marrow lesions. Recent advances in radiology and nuclear medicine have the potential to streamline the assessment of diabetic foot complications. But we must be aware of the specific strengths and weaknesses of each modality, and their applications. This review offers a comprehensive approach to the spectrum of diabetic foot complications and their imaging appearances in conventional and advanced imaging studies, including optimal technical considerations for each technique. Advanced magnetic resonance imaging (MRI) techniques are highlighted, illustrating their complementary role to conventional MRI, in particular their potential impact in avoiding additional studies.

Diabetic Foot Osteomyelitis: Is it all the Same?

Diabetic foot osteomyelitis (OM) requires a longer duration of therapy, a greater need for surgery and implies a higher rate of recidivism, a higher amputation risk, and lower treatment success. But do all bone infections behave the same way, require the same treatment, or imply the same prognosis? Actually, in clinical practice we can verify there are different clinical presentations of OM. The first one is that associated with the infected diabetic foot attack. It requires urgent surgery and debridement since "time is tissue." Clinical features and radiographs are enough for the diagnosis, and treatment should not be delayed. The second one is related to a sausage toe. It affects phalanges and it can be treated with a 6- or 8-week antibiotic course with a high rate of success. Clinical features and radiographs are sufficient for the diagnosis in this case. The third presentation is OM superimposed to Charcot's neuroarthropathy, which mainly comprises midfoot or hindfoot. It starts with a plantar ulcer in a foot that has developed a deformity. The treatment is based on an accurate diagnosis that often includes magnetic resonance, and requires a complex surgery to preserve the midfoot and to avoid recurrent ulcers or foot instability. The final presentation is that of an OM without large soft tissue compromise secondary to a chronic ulcer or a previous unsuccessful surgery secondary to minor amputation or debridement. There is often a small ulcer with a positive probe to bone test over a bony prominence. Diagnosis is made by clinical features, radiographs, and laboratory tests. Treatment includes antibiotic therapy guided by surgical or transcutaneous biopsy, but this presentation often requires surgery. Different presentations of OM mentioned above need to be recognized because the diagnosis, type of culture, antibiotic treatment, surgical treatment, and prognosis are different upon the presentation.

Bone Marrow Changes and Lesions of Diabetic Foot and Ankle Disease: Conventional and Advanced Magnetic Resonance Imaging

Diabetic foot and ankle complications contribute to substantial mortality and morbidity. Early detection and treatment can lead to better patient outcomes. The primary diagnostic challenge for radiologists is distinguishing Charcot's neuroarthropathy from osteomyelitis. Magnetic resonance imaging (MRI) is the preferred imaging modality for assessing diabetic bone marrow alterations and for identifying diabetic foot complications. Several recent technical advances in MRI, such as the Dixon technique, diffusion-weighted imaging, and dynamic contrast-enhanced imaging, have led to improved image quality and increased capability to add more functional and quantitative information.We discuss the bone marrow abnormalities encountered in daily radiologic assessment: osteopenia, reactive bone marrow edema-like signal, insufficiency fractures, Charcot's neuroarthropathy, osteomyelitis, serous marrow atrophy, digital ischemia, and bone infarcts, along with their pathophysiology and the conventional and advanced imaging techniques used for a comprehensive marrow evaluation.

Systematic review: investigating the added diagnostic value of gadolinium contrast agents for osteomyelitis in the appendicular skeleton

OBJECTIVE

Osteomyelitis is an infection of the bone marrow. MRI with gadolinium-based contrast is frequently performed for cases of suspected osteomyelitis. The objective of this systematic review is to examine the diagnostic accuracy of contrast-enhanced vs non-contrast-enhanced MRI for osteomyelitis in the appendicular skeleton.

MATERIALS AND METHODS

We conducted a systematic review of MRI in the diagnosis of osteomyelitis by searching MEDLINE and EMBASE from January 2000 to March 2020. There were 21 studies that met the inclusion criteria for the systematic review for a total of 1095 patients. Analytic methods were based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Evidence was evaluated using the STARD criteria for evaluation of completeness and transparency of reporting.

RESULTS

For diagnosing osteomyelitis in the appendicular skeleton, MRI with gadolinium-based contrast has 89% sensitivity (95% CI, 86-92%), 79% specificity (95% CI, 75-83%), and 90% overall diagnostic accuracy ([SE] = 0.03). For diagnosing osteomyelitis in the appendicular skeleton, MRI without gadolinium-based contrast has a 92% sensitivity (95% CI, 87-96%), 89% specificity (95% CI, 84-93%), and 96% overall diagnostic accuracy ([SE] = 0.03). The median score of included studies was 85% utilizing the STARD criteria with excellent interobserver agreement of 83.4%. Limitations included small sample size of studies, with retrospective designs.

CONCLUSION

No evidence was found to suggest an added diagnostic value of gadolinium contrast for the diagnosis of osteomyelitis in the appendicular skeleton. For routine cases of suspected non-spinal osteomyelitis, non-contrast MRI of the area of interest is the next most appropriate study after radiographs.

Multivariate analyses of MRI findings for predicting osteomyelitis of the foot in diabetic patients

BACKGROUND

There have been no previous magnetic resonance imaging (MRI) studies using multivariable analysis to diagnose osteomyelitis in patients with diabetic foot.

PURPOSE

To retrospectively investigate the MRI findings of osteomyelitis in patients with diabetic foot using multivariate analyses.

MATERIAL AND METHODS

From November 2015 to March 2018, 118 patients who underwent MRI of the foot to evaluate suspected osteomyelitis were included in this study. The patients were categorized into the presence or absence of osteomyelitis. The primary and secondary MRI findings were retrospectively reviewed. To identify independent predictive MRI findings, multivariate analyses with binary logistic regression and receiver operating characteristic curve analyses were performed including all 118 patients and 93 patients presenting decreased T1 signal intensity, respectively.

RESULTS

T1 signal intensity, T1 marrow pattern, T1 marrow distribution, T2 signal intensity, concordance of marrow signal intensity, cortical interruption, ulcer depth, abscess, and wet gangrene were significantly different between the two groups (P < 0.05). Multivariate analyses indicated that fluid equivalent T2 signal intensity, deep ulcer, and confluent T1 marrow pattern were major factors associated with osteomyelitis. The area under the curve of predicted probabilities for the combination of these factors was 0.799 across all 118 patients and 0.761 across 93 patients with decreased T1 signal intensity.

CONCLUSION

Confluent T1 marrow pattern is a reliable finding to suggest osteomyelitis in patients with diabetic foot. In addition, fluid equivalent T2 signal intensity and deep ulcer are important findings that may suggest osteomyelitis, irrespective of T1 signal intensity change.

Comparison of White Blood Cell Scintigraphy, FDG PET/CT and MRI in Suspected Diabetic Foot Infection: Results of a Large Retrospective Multicenter Study

Diabetic foot infections (DFIs) represent one of the most frequent and disabling morbidities of longstanding diabetes; therefore, early diagnosis is mandatory. The aim of this multicenter retrospective study was to compare the diagnostic accuracy of white blood cell scintigraphy (WBC), ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography ((¹⁸F) FDG PET/CT), and Magnetic Resonance Imaging (MRI) in patients with suspected DFI. Images and clinical data from 251 patients enrolled by five centers were collected in order to calculate the sensitivity, specificity, and accuracy of WBC, FDG, and MRI in diagnosing osteomyelitis (OM), soft-tissue infection (STI), and Charcot osteoarthropathy. In OM, WBC acquired following the European Society of Nuclear Medicine (EANM) guidelines was more specific and accurate than MRI (91.9% vs. 70.7%, p < 0.0001 and 86.2% vs. 67.1%, p = 0.003, respectively). In STI, both FDG and WBC achieved a significantly higher specificity than MRI (97.9% and 95.7% vs. 83.6%, p = 0.04 and p = 0.018, respectively). In Charcot, both MRI and WBC demonstrated a significantly higher specificity and accuracy than FDG (88.2% and 89.3% vs. 62.5%, p = 0.0009; 80.3% and 87.9% vs. 62.1%, p < 0.02, respectively). Moreover, in Charcot, WBC was more specific than MRI (89.3% vs. 88.2% p < 0.0001). Given the limitations of a retrospective study, WBC using EANM guidelines was shown to be the most reliable imaging modality to differentiate between OM, STI, and Charcot in patients with suspected DFI.

Molecular Imaging of Diabetic Foot Infections: New Tools for Old Questions

Diabetic foot infections (DFIs) are a common, complex, and costly medical problem with increasing prevalence. Diagnosing DFIs is a clinical challenge due to the poor specificity of the available methods to accurately determine the presence of infection in these patients. However, failure to perform an opportune diagnosis and provide optimal antibiotic therapy can lead to higher morbidity for the patient, unnecessary amputations, and increased healthcare costs. Novel developments in bacteria-specific molecular imaging can provide a non-invasive assessment of the infection site to support diagnosis, determine the extension and location of the infection, guide the selection of antibiotics, and monitor the response to treatment. This is a review of recent research in molecular imaging of infections in the context of DFI. We summarize different clinical and preclinical methods and the translational implications aimed to improve the care of patients with DFI.

Dynamic contrast-enhanced magnetic resonance imaging for differentiating osteomyelitis from acute neuropathic arthropathy in the complicated diabetic foot

OBJECTIVE

The main purpose of this study was to investigate the diagnostic value of dynamic contrast-enhanced MRI (DCE-MRI) in differentiating osteomyelitis from acute neuropathic arthropathy in the diabetic foot.

MATERIALS AND METHODS

This prospective study was carried out on 30 diabetic foot patients, with a mean age of 51 years. The patients all underwent clinical examinations, laboratory examinations and DCE-MRI. The DCE-MRI parameters (K^trans, K_ep and V_e) of the regions of acute neuropathic arthropathy and osteomyelitis were calculated. Receiver operating characteristic curves (ROCs) were used to identify the DCE-MRI parameters that showed the highest accuracy in differentiating the acute neuropathic arthropathy from the osteomyelitic regions. Pearson correlation coefficients were used to assess the correlations among the DCE-MRI parameters, the level of C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR).

RESULTS

The K^trans, K_ep and V_e values of the osteomyelitic regions were higher than those of the acute neuropathic arthropathy regions, and significant differences were found between the two groups (P = 0.000, P = 0.000, P = 0.000). The ROC analysis showed that K^trans and V_e performed best in differentiating osteomyelitis from acute neuropathic arthropathy, both with an area under the curve of 0.938. The Pearson correlation coefficients showed that the DCE-MRI parameters correlated significantly with the level of CRP and ESR (P = 0.000, P = 0.014, P = 0.000; P = 0.000, P = 0.000, P = 0.013).

CONCLUSIONS

Our results showed that DCE-MRI may provide reproducible parameters that can reliably differentiate osteomyelitis from acute neuropathic arthropathy.

Diagnostic performance of diffusion-weighted MR imaging in differentiation of diabetic osteoarthropathy and osteomyelitis in diabetic foot

PURPOSE

To study the diagnostic performance of diffusion weighted MR imaging in differentiation of diabetic osteoarthropathy and osteomyelitis in diabetic foot.

PATIENTS AND METHODS

This prospective study was carried out on 41 patients with diabetic foot, 22 males and 19 females with mean age of 51 years. They underwent diffusion-weighted MR imaging of the foot. The apparent diffusion coefficient (ADC) values of the bony lesions were calculated by two reviewers and correlated with the surgical findings or biopsy. The kappa statistic (k) was used to estimate the proportion of inter-observer agreement of two reviewers.

RESULTS

The mean ADC of acute diabetic osteoarthropathy was 1.27±0.19×10^-3mm²/s for reviewer 1 and 1.26±0.21×10^-3mm²/s for reviewer 2. The mean ADC value in diabetic osteomyelitis was 0.86±0.11×10^-3mm²/s for reviewer 1 and 0.85±0.12×10^-3mm²/s for reviewer 2. There was excellent inter-observer agreement of ADC value of bony lesions in diabetic foot by both reviewers (K=0.93). There was statistically significant difference in the ADC values of both groups (P=0.001). The cut-off point of ADC value of both reviewers used in differentiating acute diabetic osteoarthropathy and osteomyelitis were 0.98×10^-3mm²/s and 1.04×10^-3mm²/s with an accuracy of 94% and 93% and area under the curve of 0.94 and 0.93 respectively.

CONCLUSION

We conclude that the ADC value is a non-invasive imaging parameter that can help in differentiation of diabetic osteoarthropathy from osteomyelitis with excellent inter-observer agreement.