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Welcome back to our discussion on

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the hip labrum, which supports a

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lot of weight in most human beings.

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Let's talk about some variations.

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We'll start out with the shape of the

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labrum, which is most often triangular,

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probably about 70% of the time.

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The second most common appearance is the

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labrum being round, somewhat meniscoid looking.

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And as long as it's smooth, that's okay.

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The labrum may sometimes be

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flat or truncated looking.

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Now that produces kind of a problem.

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Because that can simulate a radial tear.

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The tip-off should be, you don't have an

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effusion, you do not have a fragment,

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and you don't have other signs of instability,

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or other signs of impingement syndrome.

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So it's there all by itself.

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And then there is the rare situation

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where as part of a dysplasia, whether it's

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developmental dysplasia or congenital absence

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of ligamentum teres, you don't have a labrum,

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which is reported in 3% of specimens,

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but I think this is an overestimation.

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Then you've got variations in signal intensity.

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Most hips, with labra, which is the majority

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of them, are going to have some signal inside.

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In fact, it is rare not to have some

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intralabral signal, analogous to what

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you have in the meniscus of the knee.

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It has an amorphous, somewhat central location.

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It can be seen on the T1,

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or the proton density fat

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suppression, less commonly on the T2.

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If it's on the T2, and it is specifically

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not just grey, but more bright, then you have

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to be worried about an intrameniscal cyst,

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which fortunately, isn't that common in the hip.

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It is more common in the knee,

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although both are uncommon.

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It is reported that high T2 signal

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occurs 15% of the time.

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That has not been my experience.

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A bigger problem is the sulcus.

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The labral sulcus is usually found just lateral

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to the interface between the hyaline cartilage

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and the labrum, the so-called transition zone.

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You'll usually see it over here.

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It'll be shallow,

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less than 25% to 30%

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of the depth of the labrum.

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It usually has a smooth top.

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It has smooth edges.

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In other words, it's not a

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serrated appearing structure.

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It usually isn't very needle-like

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or straight up and down.

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Like we see here with a very

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thin margin or edge to it.

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As stated, it isn't very deep, it's not

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associated with swelling, or an effusion,

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or a change in labral shape, or other signs

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of impingement syndrome most of the time.

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Now it's said that the most common

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location for the sulcus is posterosuperior

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about 48% of the time,

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anterosuperior, 44% of the time,

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anteroinferior, 4% of the time.

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My experience in looking at surgeries

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and labral specimens is not the same.

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In fact, there is a sulcus anterosuperior,

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but as you come down and around into the

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anteroinferior quadrant, it actually deepens.

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So you should be able to follow it.

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So if you go from low to high, and that

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defect in the labrum is getting deeper

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and deeper as you go up, that's a problem.

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And most of the time, in the anterosuperior

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quadrant, and directly

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superior, I am not reading a sulcus.

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I am reading either a chronic labral tear,

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age-related, from overuse, or from chronic

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impingement, or from developmental dysplasia,

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or a labral tear from other etiology.

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I will read a sulcus when I see something

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smooth and shallow that progressively deepens

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as I'm able to follow the labrum around into

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the anteromid and anteroinferior quadrant.

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And finally, we have another potential

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pitfall, and that is the paralabral

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plica, which I'll make here in yellow.

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It is a thin structure, oft attached to the

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ligament, that parallels the edge of the labrum.

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Now if we look at the labrum as a

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triangular structure, we have this

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little sliver-like structure next to it.

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You can see someone might confuse this as

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a piece of labrum that has been shaved off.

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Not unlike what occurs in the shoulder

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when you have low-grade subluxations and

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dislocations, and you have functional labral

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tears that are not through and through.

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And then one other comment.

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Don't confuse this area of hyaline

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transition between the labrum, which is

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here, and the hyaline cartilage, as a defect.

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There's going to be a slight transition in

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signal intensity between the two, but do pay attention to

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this area, because it is an area that is

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very prone to injury when you have large

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labral tears, or you have big traumas,

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where the labrum is detaching from the

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hyaline cartilage and the acetabulum,

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and this is oft the site of detachment.

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And then the labrum, as we've stated

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previously, will start to flip up.

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This area will get wider, and this area the

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area between the ligament and the underlying

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acetabulum will also widen and strip all the way

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up with fluid and effusion filling the space.

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Let's move on and look at some

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magnified images of the labrum on

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MRI if you've got the gumption today.

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Thanks.