osteomyelitis: the role of radiography in diagnosis

Osteomyelitis: The Role of Radiography in Diagnosis

Spencer McClelland, HMS IIIGillian Lieberman, MD

March, 2011Spencer McClelland, HMS IIIGillian Lieberman, MD

2


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


Our Patient: Foot X-ray

4


Source: BIDMC PACS

5


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


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


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


Jeffcoate, WJ, et al. Clin Infec Dis. 2004; Grayson, ML, et al, JAMA, 1995

9


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


• 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


Now let us return to our patient’s foot X-ray to look for some of the specific findings suggestive of osteomyelitis.

12


• 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


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


• 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


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


Coronal Post-ContrastAxial Pre-Contrast

• Sinus tract

Companion Patient #1: MRI Pelvis

17


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



• Intraosseous gas• Cortical thinning• Soft tissue edema

19


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


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


• 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


22


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



24


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


R LCourtesy of Dr. Kevin Donohoe

26



Courtesy of Dr. Kevin Donohoe

27


Courtesy of Dr. Kevin Donohoe


28


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



Osteomyelitis Nuclear Medicine: Other Studies

• Tagged WBCs• Radiolabeled antibiotics• Labeled immunoglobulins• Streptavidin• 111In-biotin

30



31


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


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


34


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


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


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, yearGillian 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).


THANK YOU!

And Happy Belated St. Patty’s Day, from Brooklyn the Irish Croco-Dog!

39


osteomyelitis: the role of radiography in diagnosis

Documents