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Dr. P here. This is a 41-year-old man who

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3 00:00:03,690 --> 00:00:07,600 comes in, rule out posterior tibial tendon

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tear, which is usually the history that

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is given when this diagnosis is afoot.

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We've got on the left a water-weighted

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fat-suppressed proton density image, in

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the middle, same, and on the right, same.

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So everything here is water-weighted, and

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I'll come back to at least one T1-weighted or

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proton density-weighted image in a minute. But

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it is obvious to all observing that there is

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extensive edema in the region of the navicular.

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And there is an extra bone here.

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Now, this is the condition known

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as Osteo Navicular Syndrome.

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And there are three types of accessory naviculars.

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So let's see if we can put my drawing skills to

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work, which used to be pretty good, but they've

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gotten more rudimentary as time has gone by.

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So, one that everybody knows the

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best is the os Tibiale Externum.

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And that one occurs within the tendon

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of the posterior tibial tendon.

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And you all know that the posterior tibial

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tendon, as it comes down, splays, it has an

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avicular insertion, and then has small divisions

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that go to many other bones in the foot.

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Too numerous to even say.

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As a matter of fact, if you say it went

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to every bone in the foot except that

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might be an easier way to handle it.

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So, this is the classic

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type of accessory navicular.

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The os Tibiale Externum.

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And then we have the type 2 accessory navicular.

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Where we have the accessory navicular, and then

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it has this sort of jagged edge to it, and then

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we have a synchondrotic interface right here.

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It looks like a joint, and you often get

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irregularity across the border here, and these

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two wiggle between each other and create an

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extensive amount of edema, and that is occurring.

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In this instance, and it presents

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with medial foot pain in the distal

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distribution of the posterior tibial tendon.

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Frequently, the posterior tibial

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tendon, surprisingly, is not torn.

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It may have some tendinopathy, as it does,

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maybe a little bit more proximally, but it

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usually is intact because it takes a structure

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to tug on this type 2 accessory navicular

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to produce the accessory navicular syndrome.

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So at the very least, it's

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intact to do the job of tugging.

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Then we have the third type of accessory

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navicular, also known as type 3, and

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this time instead of having some type of

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ossicle, it has fused. And it makes what

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we call a cornuate shape to the navicular.

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So the whole thing is one bone.

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You might think, well, so what?

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But a few of my fellows have been

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symptomatic from this condition.

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One I can remember in particular who

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was a competitive speed skater on land.

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And when he put on his tight-fitting boots,

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he had quite a bit of discomfort after

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about 10 or 15 minutes while skating.

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He also taught my children how to rollerblade.

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Very, very talented guy and a

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musculoskeletal radiologist down in Florida.

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So this is the arcuate or cornuate type navicular.

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So three types.

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Ostibiale externum, type 2 accessory

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navicular, and cornuate navicular.

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And it's the type 2, as we see

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here, that is the problem child.

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I mean, look at this irregularity between the

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accessory bone and the underlying navicular.

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And here's our axial projection.

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This is a T2-weighted image.

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So not the best.

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To really show the character and internal

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constituents of the posterior tibial tendon.

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But it looks just peachy.

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If we go over here to the heavily

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water-weighted image, the posterior

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tibial tendon is absolutely intact.

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There it is, splaying and making its direction

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over to some of the other bones of the foot.

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The diagnosis, type 2 accessory

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navicular with os navicular syndrome.

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Dr. P out.