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Osteomyelitis: The Role of Radiography in Diagnosis Spencer McClelland, HMS III Gillian Lieberman, MD March, 2011 Spencer McClelland, HMS III Gillian Lieberman, MD 2 Spencer McClelland, HMS III Gillian Lieberman, MD Let us begin with a patient presentation. Our Patient: History • 51 yo M with a history of hypertension who presents with right foot swelling of two months’ duration • The process began with a “callus” that he noticed on the underside of his right foot, which flaked off to reveal an ulcerated surface • Over the intervening two months, his foot became progressively swollen, but not painful • His PCP had tried him on courses of Doxycycline and Ciprofloxacin, with some improvement, but without resolution • On the day prior to admission, he underwent a foot X-ray which showed findings concerning for osteomyelitis 3 Spencer McClelland, HMS III Gillian Lieberman, MD Our Patient: Foot X-ray 4 Spencer McClelland, HMS III Gillian Lieberman, MD Source: BIDMC PACS 5 Spencer McClelland, HMS III Gillian Lieberman, MD Having introduced our patient and looked briefly at his presenting X-ray, let us talk about osteomyelitis. We will return to his X-ray shortly. Osteomyelitis: Overview • Infection of bone • Can occur by: • Contiguous spreading (i.e. from an ulcer) • Hematogenous seeding (i.e. in bacteremia) • Direct inoculation (i.e. from trauma) • Organisms responsible can be monomicrobial or polymicrobial • Hematogenous is usually monomicrobial 6 Spencer McClelland, HMS III Gillian Lieberman, MD Jeffcoate, WJ, et al. Clin Infec Dis. 2004 Osteomyelitis: Diagnosis • Diagnosis of osteomyelitis requires one of the following: • Isolation of bacteria from a bone biopsy sample obtained via sterile technique, together with histologic findings of inflammation and osteonecrosis • Positive radiologic finding beneath a foot ulcer • Positive radiologic finding with positive blood cultures • Probing to bone in a diabetic foot ulcer • Diabetic foot ulcer greater than 2 X 2 cm 7 Spencer McClelland, HMS III Gillian Lieberman, MD Jeffcoate, WJ, et al. Clin Infec Dis. 2004; Grayson, ML, et al, JAMA, 1995 Osteomyelitis: Diagnosis • Diagnosis of osteomyelitis requires one of the following: • Isolation of bacteria from a bone biopsy sample obtained via sterile technique, together with histologic findings of inflammation and osteonecrosis • Positive radiologic finding beneath a foot ulcer • Positive radiologic finding with positive blood cultures • Probing to bone in a diabetic foot ulcer • Diabetic foot ulcer greater than 2 X 2 cm 8 Spencer McClelland, HMS III Gillian Lieberman, MD Jeffcoate, WJ, et al. Clin Infec Dis. 2004; Grayson, ML, et al, JAMA, 1995 9 Spencer McClelland, HMS III Gillian Lieberman, MD Having introduced the concept of osteomyelitis and the ways to diagnose it, let us discuss the specific radiologic findings that support a diagnosis. We will start with X-ray. Osteomyelitis: X-ray Findings 10 Spencer McClelland, HMS III Gillian Lieberman, MD • Sensitivity 43-75%, specificity 75-83% • Timing • Soft tissue changes visible in 3 days • Bone changes visible in 1-2 weeks • Early findings • Bone: osteopenia • Late findings • Bone: cortical erosion, mixed lucency and sclerosis, periosteal reaction • Soft tissue: swelling Pineda, C, et al. Infect Dis Clin North Am. 2006 11 Spencer McClelland, HMS III Gillian Lieberman, MD Now let us return to our patient’s foot X-ray to look for some of the specific findings suggestive of osteomyelitis. 12 Spencer McClelland, HMS III Gillian Lieberman, MD • Marked bone lysis of the distal first metatarsal, first proximal phalanx, and first distal phalanx • Mild cortical lucency and sclerosis of the medial aspect of the distal second metatarsal • Marked soft tissue swelling along the medial foot and surrounding the first toe joints • Solid periosteal reaction of the first metatarsal Source: BIDMC PACS Our Patient: Foot X-ray 13 Spencer McClelland, HMS III Gillian Lieberman, MD Having discussed the findings of osteomyelitis on X-ray and examined our patient’s foot X-ray, let us continue with a discussion of findings on MRI that are suggestive of osteomyelitis. We will then look at an example from a patient with recurrent pubic symphysis osteomyelitis. Osteomyelitis: MRI Findings Acute/Active • Medullary space: • Fat is replaced by edema, so: • Low signal on T1 • High signal on T2, STIR, or fat-suppressed sequences • Possible cortical disruption • Wide transition zone • Soft tissue: edema, abscess, sinus tract, ulcer, cellulitis Chronic • Low signal on T1 and T2 • Bone sclerosis with cortical thickening • Sequestra on gadolinium- enhanced T1 • Narrow transition zone 14 Spencer McClelland, HMS III Gillian Lieberman, MD • Sensitivity 82-100%, specificity 75-96% • Can detect early (i.e. within 3-5 days) Pineda, C, et al. Infect Dis Clin North Am. 2006; Sammak, B, et al, Eur Radiol, 1999 Source: BIDMC PACS Source: BIDMC PACS Companion Patient #1: MRI Pelvis 15 Spencer McClelland, HMS III Gillian Lieberman, MD Axial T1 Axial T2 Fat Suppression • Areas of low signal intensity • Soft tissue irregularity • Areas of high signal intensity • Soft tissue irregularity • Superficial hyperintensity consistent with cellulitis Source: BIDMC PACSSource: BIDMC PACS 16 Spencer McClelland, HMS III Gillian Lieberman, MD Coronal Post-ContrastAxial Pre-Contrast • Sinus tract Companion Patient #1: MRI Pelvis 17 Spencer McClelland, HMS III Gillian Lieberman, MD Having discussed the findings of osteomyelitis on MRI, let us continue with a discussion of findings on CT that are suggestive of osteomyelitis. We will then look at an example from a patient with osteomyelitis involving the left hip joint. Osteomyelitis: CT Findings • Superior spatial resolution compared to MRI, but lower sensitivity and specificity • Useful when MRI is contraindicated or unavailable, or for surgical planning • Bone findings: cortical breakdown, trabecular changes, periosteal reaction, intraosseous gas • Soft tissue findings: sinus tract projection • Particularly good for showing sequestra and involucra (discussed later) 18 Spencer McClelland, HMS III Gillian Lieberman, MD Pineda, C, et al. Infect Dis Clin North Am. 2006; Sammak, B, et al, Eur Radiol, 1999 • Intraosseous gas • Cortical thinning • Soft tissue edema 19 Spencer McClelland, HMS III Gillian Lieberman, MD Axial C- Coronal C- Sagittal C- • Intraosseous gas • Cortical thinning • Soft tissue edema • Intraosseous gas • Deep tissue emphysema Source: BIDMC PACS Source: BIDMC PACS Source: BIDMC PACS Companion Patient #2: CT Hip 20 Spencer McClelland, HMS III Gillian Lieberman, MD Having looked at the findings of osteomyelitis on X-ray, MRI, and CT, let us look briefly at some findings specific to osteomyelitis that are visible on all three modalities. Osteomyelitis: Additional Findings 21 Spencer McClelland, HMS III Gillian Lieberman, MD • Sequestrum • Large devascularized fragment of bone separated from healthy bone after undergoing ischemic necrosis • Involucrum • New bone deposited around a sequestrum, resulting from cortical damage stimulating the periosteum to lay down new bone and surround the sequestrum • Brodie’s abscess • Subacute form of osteomyelitis • Common in children, especially boys • Focal abscess most commonly found in the metaphyses of long bones, particularly the tibia All photos courtesy of Sergio Fernández Tapia, MD, Tampico, Mexico, from Pineda, C, et al, Infect Dis Clin North Am. 2006 Pineda, C, et al. Infect Dis Clin North Am. 2006; Sammak, B, et al, Eur Radiol, 1999 22 Spencer McClelland, HMS III Gillian Lieberman, MD Now let us discuss the role of nuclear medicine in diagnosing osteomyelitis. Osteomyelitis Nuclear Medicine: Bone Scan Findings • Three-phase bone scan with radiolabeled marker like Technetium-99 • Flow phase: immediately after injection • Shows areas of increased blood flow, i.e. inflammation • Pooling phase: 15 minutes after injection • Shows areas of vascular permeability • Delayed phase: 4 hours after injection • Shows areas of retained uptake, most specific for osteomyelitis • Sensitivity/Specificity • If positive in three phases, sensitivity 73-100% • Metanalysis: sensitivity 61%, specificity 25% • Sensitivity decreases with coexisting conditions, like trauma, surgery, orthopedic hardware, diabetes 23 Spencer McClelland, HMS III Gillian Lieberman, MD Pineda, C, et al. Infect Dis Clin North Am. 2006 24 Spencer McClelland, HMS III Gillian Lieberman, MD Now we will see an example of a three-phase bone scan, showing increased uptake in the right foot in all three phases, consistent with a diagnosis of osteomyelitis. Companion Patient #3 Foot Bone Scan: Flow Phase 25 Spencer McClelland, HMS III Gillian Lieberman, MD R L Courtesy of Dr. Kevin Donohoe 26 Spencer McClelland, HMS III Gillian Lieberman, MD Companion Patient #3 Foot Bone Scan: Flow Phase Courtesy of Dr. Kevin Donohoe 27 Spencer McClelland, HMS III Gillian Lieberman, MD Courtesy of Dr. Kevin Donohoe Companion Patient #3 Foot Bone Scan: Flow Phase 28 Spencer McClelland, HMS III Gillian Lieberman, MD Now let us turn to a brief discussion of other nuclear modalities, with an emphasis on the gallium scan. Osteomyelitis Nuclear Medicine Findings: Gallium Scan • Uses radiolabeled gallium, which likely attaches to acute phase reactant proteins • Good sensitivity (25-80%) • More specific than three-phase bone scan (67%) • False positives due to fracture and neoplasm • Scan occurs 24 hours after injection, so only useful in the clinically stable patient 29 Spencer McClelland, HMS III Gillian Lieberman, MD Pineda, C, et al. Infect Dis Clin North Am. 2006 Osteomyelitis Nuclear Medicine: Other Studies • Tagged WBCs • Radiolabeled antibiotics • Labeled immunoglobulins • Streptavidin • 111In-biotin 30 Spencer McClelland, HMS III Gillian Lieberman, MD Pineda, C, et al. Infect Dis Clin North Am. 2006 31 Spencer McClelland, HMS III Gillian Lieberman, MD Having completed our discussion of the various imaging modalities used in diagnosing osteomyelitis, we will now return to our patient. Our Patient: Surgery • Given his foot ulcer with radiographic findings consistent with osteomyelitis, he underwent surgical exploration, debridement, and biopsy • Grossly, there was very little necrotic or actively infected tissue • The biopsy result showed: • “Fragments of granulation tissue with chronic inflammation, bone with reparative changes and focal necrosis with marrow space fibrosis and chronic inflammation; no significant acute inflammation noted.” • Wound culture grew Staphylococcus aureus, susceptible to Methicillin 32 Spencer McClelland, HMS III Gillian Lieberman, MD Our Patient: Treatment • Given a known Penicillin allergy, the patient was started on IV Daptomycin, with a PICC line for home therapy totaling six weeks • At the time of last follow-up, he had finished his Daptomycin course and, as his foot had showed signs of improvement, he had been transitioned to oral Moxifloxacin • Follow-up with Infectious Disease and Podiatry is ongoing 33 Spencer McClelland, HMS III Gillian Lieberman, MD 34 Spencer McClelland, HMS III Gillian Lieberman, MD To end, we will look at an algorithm for working up the possibility of osteomyelitis in a patient with a foot ulcer, highlighting our patient’s course as previously described. An Algorithm: Putting It All Together 35 Spencer McClelland, HMS III Gillian Lieberman, MD Source: Lipsky BA, et al. Clin Infect Dis. 2004 Take-Home Points • Osteomyelitis is an infection of bone • The gold standard for diagnosis is a sterile surgical biopsy, but imaging can play a great role in the absence of that • X-ray is the first line for imaging, as it is fast and inexpensive, but its sensitivity is only fair, since it takes weeks for changes to become apparent • MRI is the best modality, both in terms of sensitivity and specificity, and in terms of its ability to detect changes early on • Nuclear medicine studies have good sensitivity, but mixed specificity, as many other conditions can cause increased focal uptake of radiolabeled markers • Many algorithms exist for how to diagnose osteomyelitis in different clinical scenarios… follow them! 36 Spencer McClelland, HMS III Gillian Lieberman, MD 37 Acknowledgments • Dr. Jim Wu • Dr. Kevin Donohoe • Dr. David Glazier • Dr. Mai-Lan Ho • Dr. Monica Agarwal • Dr. Gillian Lieberman • Emily Hanson Student Name, year Gillian Lieberman, MD 38 References • Grayson, ML, et al. Probing to bone in infected pedal ulcers. A clinical sign of underlying osteomyelitis in diabetic patients. JAMA. 1995 Mar 1;273(9):721-3. • Jeffcoate, WJ, et al. Controversies in Diagnosis and Management of Osteomyelitis of the Foot in Diabetes. Clin Infect Dis. (2004) 39 (Supplement 2): S115-S122. • Lipsky, BA, et al. Diagnosis and Treatment of Diabetic Foot Infections. Clin Infect Dis. (2004) 39 (7): 885-910. • Mader JT, et al. Update on the diagnosis and management of osteomyelitis. Clin Podiatr Med Surg. 1996;13(4):701-24 • Pineda, C, et al. Imaging of Osteomyelitis: Current Concepts. Infect Dis Clin North Am. 2006 Dec;20(4):789-825. • Sammak, B, et al. Osteomyelitis: a review of currently used imaging techniques. Eur Radiol. 9,894-900 (1999). Student Name, year Gillian Lieberman, MD THANK YOU! And Happy Belated St. Patty’s Day, from Brooklyn the Irish Croco-Dog! 39 Student Name, year Gillian Lieberman, MD Osteomyelitis: �The Role of Radiography in Diagnosis Slide Number 2 Our Patient: History Our Patient:�Foot X-ray Slide Number 5 Osteomyelitis: Overview Osteomyelitis: Diagnosis Osteomyelitis: Diagnosis Slide Number 9 Osteomyelitis: X-ray Findings Slide Number 11 Slide Number 12 Slide Number 13 Osteomyelitis: MRI Findings Companion Patient #1:�MRI Pelvis Companion Patient #1:�MRI Pelvis Slide Number 17 Osteomyelitis: CT Findings Slide Number 19 Slide Number 20 Osteomyelitis: Additional Findings Slide Number 22 Osteomyelitis�Nuclear Medicine: Bone Scan Findings Slide Number 24 Companion Patient #3�Foot Bone Scan: Flow Phase Companion Patient #3�Foot Bone Scan: Flow Phase Companion Patient #3�Foot Bone Scan: Flow Phase Slide Number 28 Osteomyelitis�Nuclear Medicine Findings: Gallium Scan Osteomyelitis�Nuclear Medicine: Other Studies Slide Number 31 Our Patient: Surgery Our Patient: Treatment Slide Number 34 An Algorithm:�Putting It All Together Take-Home Points Slide Number 37 Slide Number 38 THANK YOU!��And Happy Belated St. Patty’s Day, from Brooklyn the Irish Croco-Dog!�