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<v ->Let's move on now and talk a bit about sesamoid bones.

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These are small typically round or ovoid bones.

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They occasionally are fibro cartilages in nature.

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They're embedded within tendons

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and they will help the tendon

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in certain functions for which it is responsible.

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They're often divided into two types.

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Here are the two types

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type A, the sesamoid bone is located adjacent

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to the articulation incorporated in the joint capsule.

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Think of the patella, the sesamoids

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in the great toe or thumb, and then type B sesamoid bone

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which is located where tendons

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are angled about bone surfaces.

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And the example I would think

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of here would be the peroneus longest tendon.

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These are easy to identify their most commonly

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seen of course, within the hands and in the feet.

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And in the hands we see them

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especially at the metatarsophalangeal joints

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and the interphalangeal joint of the thumb

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and they can be multiple or they can be single.

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And again, of course, massified, they're easy to appreciate

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but they can be fibro cartilages.

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And there are two of them that I would emphasize here.

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They both occur in the foot.

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The first is a fibro cartilage sesamoid

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that occupies this area

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just medial to the tibialis posterior tendon

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along the tailer head

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it is separate from the tendon.

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At least you can see the lower signal of the tendon

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but this can simulate severe tendonosis or in fact

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a tendon tear and a similar phenomenon occasionally is seen

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within the peroneus longest tendon.

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And this is a fibro cartilaginous nodular sesamoid here.

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You see it in the cuboid groove.

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It looks like severe tendonosis of the peroneus longest.

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This brings our us to the hallux, the great toe.

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And let's talk for a while

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about the sesamoids of the great toe.

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There's a lot of interest in these particular sesamoids

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because as you know, this is an area of sports injury

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which I'll talk about in a few minutes

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You're gonna see a number of pictures, specimens, and MRR

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done by our UCSD musculoskeletal research group.

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And they're magnificent pictures of this particular region.

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These are transverse images showing you a section

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through the metatarsal head and the medial

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and lateral sesamoids this being the medial

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this being the lateral you'll note that typically

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the sesamoids have a convex surface covered by cartilage.

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And they sit in facets, which are concave.

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There's a medial

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and lateral sesamoid facet between those facets.

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There's an elevated area known as a metatarsal crest.

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There's an inter sesamoid ligament

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a strong ligament that connects the medial

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and lateral sesamoids and superficial to it.

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We can find the flexor hallucis longest tendon.

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If we look at the dorsal surface we can see the

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extensor hallucis, longest tendon and lateral to it,

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a smaller tendon, the extensor hallucis brevis tendon.

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So that's the regional anatomy.

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If we go ahead and look at it, it, and look

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at the muscles and tendons

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you can see how complex this region is.

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Let's look at the medial sesamoid things attaching

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to the medial sesamoid

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or the abductor hallucis tendon abbreviated (AB)here

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and the medial head

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of the flexor hallucis brevis muscle that's (FHBm).

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They attach should the medial sesamoid

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and the lateral sesamoid things are even more complicated.

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Here, we have the oblique

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and transverse heads of the adductor hallucis muscle

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and the lateral heads of flexor hallucis brevis muscle

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all converging on that lateral sesamoid

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between the two is the inter sesamoid ligament

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that I mentioned earlier.

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And we can see in these particular drawings

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portions of the plantar plate, these are ligaments that run

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from the sesamoid in a transverse direction

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attaching to the proximal phalanx

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both immediately and laterally.

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Those portions of the plantar plate are the strongest.

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But unfortunately, they're also the site

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of most common site of injury.

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Now, when in fact a sesamoid is developmentally absent

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the facet on the metatarsal head may be absent

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or may be convexy even as shown in this example

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of developmental absence of the lateral sesamoid.

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This is a very unusual example.

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We published it in the rad source web clinic

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a number of years ago, because it's typically

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the medial sesamoid that is more often absent.

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And in addition, the crest

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between those two facets may be shallow or absent here.

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It looks up the it shallow.

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So this indicates this is not surgically removed

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but this is a developmental absence of the sesamoid.

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Now there is a name that is often used

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for anything that produces a painful sesamoid.

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I don't like this name, but I know that podiatrists

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and orthopedic surgeons and radiologists do use it.

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So sesamoiditis in my mind represents in fact

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painful sesamoid bones, and it can relate to an injury

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be it in a single episode or repetitive stress.

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It can relate to developmental changes, ischemia.

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I mean, it can relate to so many different things.

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I'm gonna show you a few examples.

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So this is a developmentally partition sesamoid

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Let me just say a word or two about that

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'cause I know when you look

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at cases like this, that question arises

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is it a fracture or is it developmental?

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There's one thing that will help you in some cases

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developmental bipartite or multi partite sesamoids

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are far more common immediately than laterally.

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So if you see partitions in the lateral sesamoid

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you ought to consider, maybe you're dealing with trauma

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and not developmental, but when it is developmental

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abnormal motion may occur at the site of partition.

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And that can lead as

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in a case like this to pain and inflammation.

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So this is a cause

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in my view of sesamoiditis repetitive stress, particularly

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in those young people who are active can lead to changes

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including stress factors that may involve the

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sesamoid here's one example, Marcello, Deborew.

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One of the instructors in this course sent me this case

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and other things can occupy the sesamoids.

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I mean, we all recognize in the foot the

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that we deal with infections and patients who have diabetes

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a typical mechanism is a soft issue ulcer that then

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extends the bone.

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And indeed a sesamoid may be the first bone that is involved

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as in this particular example.

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So it's an extended definition of sesamoiditis in this case.

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And similarly we know gout

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and I'll talk detail about gout later this week

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but gout involves the first metatarsal phalangeal joint

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but you may not know that it can begin

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in the sesamoid and may be isolated to the sesamoid

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without involving the other portions of, of the joint.

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This is a case again, Marcelo sent this to me

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showing you involvement

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of the medial sesamoid as well as the metatarsal

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and phalangeal portions of the joint,

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perhaps again sesamoiditis

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but let's look at that plantar plate

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for a moment and talk briefly about it.

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It has components that attach the sesamoid

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to the metatarsals and components that attach the sesamoid

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to the proximal failings.

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Those that attach to the metatarsals are

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noticed sesamoid metatarsal ligaments.

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They have a kind of a vertical or vertical

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(indistinct).

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Those that attach to the phalanx.

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So notice sesamoidal phalangeal

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they're more transverse or horizontal in location.

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As I mentioned, these are the strongest

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particularly the medial one, but these are the

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this is the site.

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More often that we see abnormalities

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they occur both immediately and laterally.

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This is what they would look like on a transverse image.

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So the ones that run from the sesamoid

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to the Metatarsal often that have seen in the axial plane

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whereas the ones that run from the sesamoid to the phalanx

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or more often better seen in this agile plane here

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again from our UCSD musculoskeletal research group, look

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look how beautifully we can see these components

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of the plantar plate.

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Here we see the medial

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and lateral sesamoidal metatarsal ligaments.

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Here's the inter sesamoid ligament.

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And here in the sagittal image

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we see the mesial sesamoidal phalangeal ligament

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and just lateral to it would be the pad where

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the inter sesamoid ligament might be also extended

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into this region.

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It's known as a fibro cartilages pad.

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The typical mechanism of injury that we see

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is hyperextension.

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And this was, I think originally described

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in American football players who were

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were playing on a artificial turf.

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And what would occur would be an injury where

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they would stub their toe lead to hyperextension Brady Wong.

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One of the radiologists who

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at UCSD made the beautiful illustration to

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show you exactly what happens.

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Here's the hyperextension.

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You can see the force extending down

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tearing the sesamoidal phalangeal ligaments.

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Stress test can be done here.

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We're looking at a stress test

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of the left foot and a stress test of the right foot.

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And if you do these, you can make measurements

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between the sesamoid and the base of the metatarsal.

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And when you're dealing with in fact

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a turf toe that distance

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on the injured side will be greater than on the normal side.

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In this case, there's a bone fragment that we can see there.

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So here is that case and the images the MR

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images show you disruption here

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of that medial sesamoid phalangeal ligament, well shown.

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Here's another case similar abnormality involving

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that sesamoidal phalangeal ligament, but

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in this case also associated

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with the transverse fracture involving the sesamoid itself.

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So these are plantar plate injuries, turf toes.

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We obviously get plantar plate injuries

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in the other toes as well.

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Another interesting sesamoid bone that we find

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in the foot is the sesamoid when the peroneum longest tendon

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and this is the osteopenia

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in a normal position of the foot

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we find it at the level of the calcaneal cuboid joint

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or just distal to it

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near a facet on the lateral aspect of the cuboid.

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When we have fractures of it,

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those fractures may displace and the more the displacement

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the more likely you're dealing

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with an injury to the peroneum longest tendon.

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Here's an example how dramatic that displacement may occur.

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We can see the position at this point is abnormal

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but not as far as it is in March one month later

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or in June in a patient

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with a complete tear of the peroneus longest tendon.

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Here's another one where that Os peroneum has now displaced

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to the level of the ankle joint complete tear

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in the Peroneus longest tendon.

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And there is a syndrome associated

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with Os peroneum at the level of the calcaneal cuboid joint.

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It's known as the POPS Painful Os Peroneum Syndrome.

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There's often edema within the

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Os Peroneum as shown in this case.

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And there's often as well, pathology of the peroneus longest

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and edema within the cuboid or calcaneus or in both bones.

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Another example here with edema

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in that Os Peroneum so be aware of the POPS syndrome.