Osteomyelitis

Preliminary Diagnosis: Osteomyelitis

I. What imaging technique is first-line for this diagnosis?

• Plain film radiography

II. Describe the advantages and disadvantages of this technique for diagnosis of osteomyelitis.

Advantages

• Quick

• Can reliably exclude common causes of musculoskeletal pain, such as fracture, arthropathy, or neoplasm

• Can strongly suggest osteomyelitis given the appropriate clinical history, laboratory findings, and positive pertinent radiographic findings

• Provides superior resolution of the osseous structures

• In comparison to CT, patients are exposed to less ionizing radiation

Disadvantages

• Not sensitive for diagnosis or complications

• Radiographic changes of acute osteomyelitis occur 1-2 weeks following the clinical onset of infection

• Exposes the patient to ionizing radiation

III. What are the contraindications for the first-line imaging technique?

• No significant contraindications exist.

IV. What alternative imaging techniques are available?

• MRI with gadolinium

• Contrast enhanced CT

• Three-phase Tc-99m HDP/MDP bone scintigraphy

• Combined tagged WBC imaging/Tc-99m sulfur colloid imaging

V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of osteomyelitis.

MRI with Gadolinium

Advantages

• Gold standard for diagnosing osteomyelitis

• Highly sensitive and specific for diagnosing osteomyelitis, when contrast is used

• Provides detail on the extent of infection

• Findings substantially precede the radiographic changes of acute osteomyelitis

• Can accurately detect complications of osteomyelitis: sinus tract, skin ulceration, abscesses, and pathologic fractures

Disadvantages

• Provides less osseous detail than CT

• Expensive

• Time consuming

• Requires significant patient cooperation to minimize motion artifact

• Sensitivity/specificity decreases in setting of coexistent degenerative change or adjacent prosthesis

• Intravenous contrast requires that the patient have good renal function with a GFR greater than 60. Administration of intravenous contrast is decided individually on a case-by-case basis with a GFR greater than 30 and less than 60.

Contrast enhanced CT

Advantages

• Provides superior anatomic and spatial detail compared with plain radiographs

• Findings parallel the radiographic findings; however, osseous lytic destruction and serpiginous tracking are more evident.

• Can better detail the extent of infection and development of complications (ie, soft tissue abscesses) when iodinated contrast is utilized

Disadvantages

• Exposes the patient to a large amount of ionizing radiation

• Less sensitive and specific than MRI for detecting complications of osteomyelitis

• Decreased sensitivity in presence of adjacent metallic prosthesis, secondary to artifact

• Exposure to intravenous contrast

Multiphase Bone Scintigraphy

Advantages

• Highly sensitive in setting of acute infection, if increased activity detected on all three phases.

• Useful if suspecting multifocal osteomyelitis, as a larger region or the whole body may be imaged

• May be used despite CT or MR contraindications

Disadvantages

• May be falsely negative

• Lacks specificity, often requiring additional radiologic correlation with MRI or tagged WBC scan. Markedly diminished in the setting of arthropathy, surgical change (ie, prosthesis), trauma, and noninfectious processes (ie, Paget’s disease, fibrous dysplasia, etc)

• Lacks anatomic detail afforded by CT and MR

• Limited in patients with renal insufficiency

• Exposes patient to more radiation than if CT, plain film, or MR were utilized.

• Requires significant patient cooperation, often requiring patients not to move for prolonged periods

In-111 tagged WBC scan with Tc-99m Sulfur Colloid Marrow Mapping

Advantages

• Highly sensitive and specific for acute osteomyelitis

• Can reliably distinguish acute osteomyelitis from Charcot neuropathic change.

• Useful if suspecting multifocal osteomyelitis, as a larger region or the whole body may be imaged.

• May be used despite CT or MR contraindications

Disadvantages

• May be falsely positive in patients with recent fractures or orthopedic postsurgical change

• Not sensitive for spinal osteomyelitis

• Lacks anatomic detail afforded by CT and MR

• Exposes patient to more radiation than if CT, plain film, or MR were utilized

• Requires significant patient cooperation, often requiring patients not to move for prolonged periods

VI. What are the contraindications for the alternative imaging techniques?

MRI with Gadolinium

• Contraindicated in patients with non–MR-compatible metallic hardware or foreign bodies

• Gadolinium is contraindicated in the patient with impaired renal function and a GFR less than 30. Administration of intravenous contrast is decided individually on a case-by-case basis with a GFR greater than 30 and less than 60.

Contrast enhanced CT

• Contraindicated in pregnant women especially within the first two trimesters.

• Patients with allergic reactions (eg, itching, rash) to intravenous contrast and more severe allergic reactions (eg, angioedema of the throat, anaphylaxis) should be pretreated with steroids and antihistamines for a minimum of 13 hours prior to CT imaging with IV contrast.

Multiphase Bone Scintigraphy

• Bone scintigraphy is contraindicated in the pregnant patient.

In-111 tagged WBC scan with Tc-99m Sulfur Colloid Marrow Mapping

• No significant contraindications exist.