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Foreign Body Reaction

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Now there are different types of ear interference screws.

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The metallic ones are the radiologist's worst, right?

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Nightmare in that they create tons

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of metallic susceptible artifact, making it very difficult

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to evaluate the grafts.

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We like the, um, either the radiolucent, the peak, uh,

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spacer, uh, now spacers, but peak, uh, interference grooves

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or alternatively these bioabsorbable screws.

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The problem with bioabsorbable screws

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that in some patients they may incite an inflammatory

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foreign body reaction that can be difficult

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to distinguish from infection.

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Here's a patient with extensive bone marrow edema about this

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interference screw, and you can see

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as well there's a soft tissue reaction around this,

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uh, interference screw.

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Clearly this has to be correlated with clinical parameters

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of infection, but in some cases patients may not be, uh, uh,

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may not behave infected

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and still have infection, so tissue sampling

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may be needed in those cases.

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So infection is a dreaded complication,

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but fortunately it's, uh, not too frequent, less than 1%.

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Obviously. Again, these need to be correlated

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with clinical SI signs and symptoms, which may be absent,

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but certainly with the MRI findings, here are the list

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of findings you wanna look for, as with infection,

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anywhere else in the musculoskeletal system.

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So here's a patient, uh, who, uh, clinically had infection

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and can see the bone marrow edema surrounding the

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interference screws.

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You can see the joint effusion as well.

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So the simplest thing to do at least, is to do a joint tap

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and send it for a white cell count.

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And for culture and sensitivity.

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Here's a patient with a more dramatic example of infection

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where we can see, uh, basically periosteal reaction.

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These are post contrast enhanced sequences.

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We can see sinus tract formation within the

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medullary space of the bone.

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We can see developing abscesses within the medullary space,

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and we can see the synovial proliferation,

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the enhancing synovium, uh, throughout the joint space.

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And this patient, uh, had proven infection.

Report

Faculty

Donald Resnick, MD

Professor Emeritus, Department of Radiology

University of California, San Diego

Mini N. Pathria, MD, FRCP(C)

Division Chief, Musculoskeletal Imaging

University of California San Diego

Eric Y. Chang, MD

Adjunct Professor, Radiology

University of California, San Diego

Brady K. Huang, MD

Clinical Professor of Radiology

UC San Diego Medical Center

Tags

Musculoskeletal (MSK)

MRI

Knee