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Tibial Tunnel Placement

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As I said earlier, tibial tunnel placement, not

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as critical, but still important, um,

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to maintain isometry throughout the range of motion.

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If you have a tibial tunnel that's too far anterior,

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what can result in knee extension is impingement.

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Um, sometimes referred to as notch

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or roof impingement on the graft.

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And if it's too far posterior, we run into this problem

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with laxity where you could have

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translational laxity of the knee.

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Going back to the radiographic assessment, again,

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blooming SATs line is your thread, so you wanna make sure

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that blooming SATs line basically aligns

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with the anterior aspect of the tibial tunnel.

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If it's not aligned, if it's too far anterior,

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you could have problems with a graft including, uh,

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graft failure or roof impingement.

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What's a good landmark as far

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as the anterior posterior placement?

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At least some studies in the literature has suggested

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that using the anterior cortical margin

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and the posterior cortical margins of the tibia as landmark

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landmarks, the center of the footprint roughly should be at

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the 40%, uh, mark from anterior to posterior.

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And if it's too far anteriorly 20%

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or less, then you're going to have problems

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with roof in impingement.

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And here is just an example from the literature, uh,

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from Radiographics, uh, showing in, um, roof impingement.

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You can see some posterior bowing

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of the anterior cruciate ligament

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and some altered signal on the anterior graft fibers.

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Although you may, uh, look at this

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and say, well, the center of

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that footprint actually isn't too far, um, anterior,

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it's actually kind of more in the middle

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of the tibial plateau,

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but nevertheless, this was the, um,

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sample that they provided.

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So, MRI is the preferred examination for symptomatic

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ACL reconstructions, of course, CT arthrography in patients

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who have contraindications to MRI

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and similar to radiographs, you want

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to look at tunnel positioning, graft positioning, and

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or any intrinsic complications that you may see on MRI.

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