Imaging of Pedal Osteomyelitis Timothy W. Deyer, MD East River Medical Imaging

Osteomyelitis Clinical assessment limited Only 32% (9/28) of pts with ulcers and osteomyelitis were clinically suspected of having osteomyelitis (Newman et al. JAMA 1991) Poor inter-observer agreement based on clinical exam in pts with ulcers (Edelman et al. J Gen Intern Med 1997) Probing to bone is only 66% sensitive (Grayson et al. JAMA 1995) In patients with ulcer and osteomyelitis will only probe to bone in 66%

Osteomyelitis Early identification of osteomyelitis important for patient management and prognosis

Ultrasound X-rays MRI CT Gadolinium Bone Scan WBC Scan Marrow Scan Radiology Ultrasound X-rays MRI CT Gadolinium Bone Scan WBC Scan Marrow Scan

ACR Recommendations for Pedal Osteomyelitis in Diabetics (2008) X-ray, MRI, Nuclear Medicine, CT, Ultrasound Evidence based recommendations 6 different clinical situations (-) neuroarthropathy with increasing soft tissue involvement (+) neuroarthropathy with increasing soft tissue involvement

ACR Recommendations (2008) No neuroarthropathy Soft tissue edema, no ulceration Ulcer without exposed bone Ulcer with exposed bone Neuroarthropathy

Soft tissue edema without ulceration or neuroarthropathy

Ulcer without exposed bone or neuropathy

Ulcer with exposed bone without neuropathy

Neuroarthopathy without ulceration

Neuroarthropathy with ulcer without exposed bone

Neuroarthropathy with ulcer with exposed bone

Suspicion of Osteomyelitis Conclusion Ulcer with Bone X-Ray - High Suspicion + MRI +/- Gad Suspicion of Osteomyelitis Osteomyelitis Moderate + Soft Tissue Swelling X-Ray Bone scan No/Low

Why? MRI has the highest sensitivity and specificity Wrobel and Connolly J Am Pod Med Assoc 1998 Radiographs 54% sens, 80% spec 99mTC BS 91% sens, 46% spec In 111 WBC 88% sens, 82% spec MRI 92% sens, 84% spec Meta-analysis of studies from 1960 to 2006 (Kapoor et al ARCH INTERN MED/VOL 167, JAN 22, 2007) “Magnetic resonance imaging performance was markedly superior to that of technetium 99m bone scanning, plain radiography, and white blood cell studies” Diagnostic odds ratio: Tc 99m Bone Scanning: 7 studies—149.9 vs 3.6 Plain radiography: 9 studies—81.5 vs 3.3 White blood cell studies: 3 studies—120.3 vs 3.4

Do I need Gadolinium? Does not increase sensitivity for osteomyelitis Improves Soft tissue evaluation Abscesses Sinus tracts Assessment of tissue viability Contraindications Poor renal function (CrCl<30) NSF-nephrogenic systemic fibrosis Tan et al, The British Journal of Radiology, 80 (2007), 939–948

MRI of Osteomyelitis Primary signs Secondary signs Bone marrow edema Bone marrow enhancement Secondary signs Cortical destruction Periosteal reaction Intra-osseous abscess Ulceration Sinus tract formation Abscess

Case 1 Bone marrow edema Cortical destruction Ulceration

Case 1 Cortical destruction Ulceration

Case 1 Bone marrow enhancement

Case 2 Bone marrow edema Ulceration with exposed bone Cortical destruction

Case 2 Bone marrow edema Sequestrum Cortical destruction

Case 3 Bone marrow edema Cortical destruction Sinus tract

Case 3 Cortical destruction Sinus tract

Case 3 Enhancing bone marrow Cortical destruction Sinus tract

Osteomyelitis vs. Neuroarthropathy Contiguous spread of infection from the skin Neuroarthropathy Primarily a joint process

Osteomyelitis vs. Neuroarthropathy Bone marrow signal High T2, Low T1, Enhancement Acute: mimics osteo Chronic: normal or low Bone marrow pattern Single bone Periarticular Distribution Focal Several joints Typical location Wt bearing, toes, metatarsal heads, calcaneus Midfoot Deformity Usually none without underlying neuroarthropathy Deformity common with bony debris Soft tissue changes Associated with ulcer, abscess or sinus tract Skin intact but edematous Tan et al, The British Journal of Radiology, 80 (2007), 939–948

Neuroarthropathy Midfoot - Centered at tarsometatarsal joints Osseous destruction and proliferation Tarsal disorganization

Neuroarthropathy Bone marrow edema Midfoot - centered at tarsometatarsal joints Soft tissues not involved

Neuroarthropathy with Superimposed Osteomyelitis Challenging diagnosis Secondary signs of osteomyelitis most helpful Sinus tract Fat infiltration Abscess Joint fluid enhancement Follow up MRI can be helpul Increasing erosions Increasing marrow edema Disappearing subchondral cysts Ahmadi ME et al. Radiology 2006;238:622–31.

Neuroarthropathy with Superimposed Osteomyelitis MR images show development of a sinus tract. (a) Sagittal T1-weighted fat-suppressed postcontrast fast multiplanar spoiled GRE image (230/2) obtained in a 60-year-old man with neuropathic arthropathy of the midfoot and hindfoot shows multiple joint subluxations with subcutaneous enhancement only (arrow). (b) Twelve months later the patient presented with a draining plantar ulcer; another sagittal T1-weighted fat-suppressed postcontrast fast multiplanar spoiled GRE image (280/2) shows a tram-track pattern of soft-tissue enhancement representing a sinus tract (arrowheads) leading to the cuboid (arrow), which demonstrates enhancement proved to represent osteomyelitis at surgery. Ahmadi M E et al. Radiology 2006;238:622-631 ©2006 by Radiological Society of North America

Conclusion Current ACR recommendations X-ray MRI MRI is most sensitive and specific test Gadolinium No improvement of osteomyelitis detection Improved detection of concomitant soft tissue processes Neuroarthropathy Often can be differentiated from osteomyelitis by MRI

Questions? Thank You