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MRI Anatomy Review: A Look at the Acetabular Anatomy in the Axial Plane

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Let's show you some axial projections.

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Without and with intra-articular contrast.

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On your left, we see the without straight,

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orthogonal axial with the triangular

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shaped normal appearance of the labrum

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transitioning into the capsular ligament.

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Which is strong and secures the anterior hip.

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The structure in front is the iliopsoas tendon.

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The higher signal intensity represents

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the two opposed surfaces of the femoral

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and acetabular hyaline cartilage, and

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we're in the upper quadrant of the hip.

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Look at how strong the ligamentous anatomy

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is as it crosses over from medial to lateral.

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In the back, the labrum is also a large,

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triangular, hypo intense structure with the

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ischiofemoral ligament emanating from it.

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These small areas of irregularity

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represent the normal embryologic fusion

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sites of the triradiate cartilage.

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On the right is the contrast

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enhanced arthrographic image.

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This small, ill-defined, hyper intense

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area anterior to the labrum, which

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is here. This brighter area here

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represents a recess and nothing more.

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The posterior labrum is highlighted with

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the ischiofemoral ligament and capsule

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lifted off and coming straight into the

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screen, coming right at you, are the pubic

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and ischial heads of the ligamentum teres.

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Now let me scroll down one.

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More level in this patient.

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This is scrolling up.

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There's the upper portion of

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The ischiofemoral ligament.

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Acetabulolabral complex, and let me go down one.

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And as we go down, there is

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A small defect in the labrum.

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A very common, difficult problem for all imagers

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And surgeons when they look at their images.

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So what do we do with this little cleft?

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If it's round and smooth, it is said that

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This is non problematic and a variation.

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But such clefts are really

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Uncommon in younger individuals.

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And when a cleft is truly a cleft,

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It will maximize in its depth

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In the anteroinferior quadrant.

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So let's go down and see if it gets bigger.

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It doesn't get bigger.

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In fact, it disappears.

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It is not behaving like the normal

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Cleft, which has its greater depth at

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The 7 or 8 o'clock position, again, in

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The anteroinferior quadrant of the hip.

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That is problematic.

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Now let's look at our arthrographic image.

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In which our cleft, which is greater than 25

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Percent depth, maybe not a cleft, on the second

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Cut, we see an oblique orientation of it.

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I'll blow it up a little

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Bit more so you can see it.

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There it is.

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What we thought was a cleft, not a cleft.

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So we have some beautiful normal anatomy,

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But we also have some extremely subtle

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Abnormal anatomy that many people

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Would have deemed normal anatomy.

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A couple of other pearls before we step away.

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The posterior labrum and the axial projection.

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Right smack dab in the middle of

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The fibrous labrum should line up

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With the center of the femoral head.

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The anterior labrum should be medial, or towards

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The midline, relative to the posterior labrum.

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For if the anterior labrum is sitting out

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Here, I'll draw it with a little arrow,

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If it's sitting over here, relative

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To the posterior labrum. There it is.

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Then you have the condition of

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Retroversion, and this is just too long.

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That is problematic, and

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Either acquired or a dysplasia.

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Finally, let's go over to our contrast

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Enhanced image, and scroll it a little bit,

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And look at some of the capsular recesses.

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They can be quite large in the

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Inferior aspect of the hip.

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Here we are down low.

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Maybe I won't make it so large.

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So you can see where you are, and you can

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See how floppy and distensible the capsule

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Is as we come up with the anterior boundary

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Of the capsule, seen relative to the labrum,

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And the recess, seen anterior to the labral

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Complex, and posterior to the labral complex.

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Let's move on to another projection, shall we?

Report

Description

Faculty

Stephen J Pomeranz, MD

Chief Medical Officer, ProScan Imaging. Founder, MRI Online

ProScan Imaging

Tags

Musculoskeletal (MSK)

MRI

Hip & Thigh

Bone & Soft Tissues

Arthrography

Acquired/Developmental

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