4/8/2017 � NONE Alexander Reyzelman DPM, FACFAS - Co-Director, UCSF Center for Limb Preservation -Associate Professor, Dept of Medicine California School of Podiatric Medicine at Samuel Merritt University � Marrow: decreased signal intensity on T1-w images: • Geographic, medullary distribution, confluent = � MRI � Sensitivity – 90-99% osteomyelitis � Marrow edema � Specificity – 60-80% � Decreased signal on T1 � Increased signal on T2 � Abscesses, sequestra, sinus tracts T1 T2 FSE fatsat 1
4/8/2017 � Marrow: decreased signal intensity on T1-w � Short axis T1 with gadolinium with and increased signal intensity on T2-w, osteomyelitis of second metatarsal � Enhancement with intravenous gadolinium (Gd) – but not if ischemic due to PAD � IV gadolinium (Gd): improves detection of soft tissue abscess, sinus tracts and devitalized tissue (+/- for diagnosis of osteomyelitis) � 68 y.o. male DM x 30 yrs with history of healed right hallux IPJ ulcer � Reports recurrent redness and swelling of the hallux and has had several courses of oral ABX during the past 3 months � States that his right hallux and foot gets recurrent swelling and redness after he finishes the course of ABX 2
4/8/2017 � WBC- 9.8 � Afebrile � ESR – 4 � CRP – 2.2 � Xrays: � 1. Cortical collapse and irregularity with possible erosion of the lateral aspect of the articular surface of the first metatarsal head with increasing sclerosis is concerning for osteomyelitis given the clinical history of cellulitis. Posttraumatic change or osteonecrosis may also be considered. MRI may be helpful for further evaluation. � 90-100% � 60-80% � Early osteomyelitis � Many conditions can characterized by cause marrow edema marrow edema � Inflammation of associated with adjacent tissues may inflammation result in inflammation of the bone � Presence of Charcot makes it even more problematic Vartanians et al. Skel Rad 2009 3
4/8/2017 � Acute neuropathic osteoarthropathy � Acute fracture � Stress fracture � Recent surgery � Altered weight-bearing � Arthritis � Reactive marrow edema Post- Gd Infected Non-infected Subchondral cysts 2% 76% Joint erosion 51% 39% Diffuse marrow involvement T1-weighted 41% 12% T2-weighted 48% 12% Post-gadolinium 42% 9% Ahmadi ME et al: Radiology 2006;238:622-631 . 4
4/8/2017 Infected Non-infected � MRI is the best imaging modality for Joint effusion: diagnosing osteomyelitis 21% 62% Thin rim enhancement 47% 26% Diffuse enhancement � Sensitivity of >90% � Specificity of around 80% Soft tissue fluid collection 95% 48% Replacement of subcut. fat 68% 36% � Positive Predictive Value = 84% • With a Pre-test probability of 50% Sinus tract 84% 0% Ahmadi ME et al: Radiology 2006; 238:622-631. � The probability of disease prior to testing • Patient’s history (duration of the ulcer, lack of treatment response) • Objective findings (size of the ulcer, probing to bone) • Simple diagnostic test (Xrays, ESR) Kapoor et al. Arch In Med 2007 5
4/8/2017 Patient Evaluation � Large/extensive ulceration � Deep ulceration Acute Ulceration Chronic Ulceration Probe to Bone � Ulceration Overlying bony prominences Shallow Ulceration Deep Ulceration Exposed Bone � Ulceration that fails to heal with standard Cellulitis without Ulceration Extensive Ulceration Radiographic Bone Rapid Improvement/Healing Overlying Bony Structures destruction treatment Lack of Bony deformity Recurrent Infection Multiple Risk Factors � Biochemical markers (ESR, CRP) Low ESR Slow/Stalled healing High ESR � Radiographs showing bone destruction HIGH LOW MODERATE � Low ESR -4 � Low CRP- 2.2 � No ulcer � Not probing � LOW PRE TEST PROBABILITY � PPV= 36% 6
4/8/2017 � “Most clinicians agree that MRI is the most � Negative MRI does a good job of ruling out osteomyelitis useful of the clinical imaging tools” � Positive MRI should be interpreted with extreme caution. � Accuracy of MRI in distinguishing osteomyelitis vs. � 17 studies evaluating imaging of pedal Charcot has not been established in the general population of diabetic patients with low prevalence of infection osteomyelitis in diabetics: 55% pre-test � Interpretation of a positive MRI should be done in probability of disease - PPV of MRI = 84% conjunction with other objective findings. � As with most other diagnostic tests, the predictive value is � With 10% pre-test probability of disease: heavily influenced by the underlying prevalence of the disease. would yield 36% PPV of MRI � Conclusion: selection bias may over-value a diagnostic test *Vartanians VM et al: Skeletal Radiol 2009;38:633. 7
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