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Welcome to our vignettes on the

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hip, and we're right on the cusp of

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transitioning from the anatomic sequence

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side to the anatomic pathology side.

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So you've heard a lot about sequences in the

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past, and we're going to continue framing the

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important sequences, but I think we need to

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get a few terminology issues out of the way.

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So I've created by hand, as you can tell from

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my rudimentary art skills, this line drawing,

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which shows a few key anatomic areas.

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And I'm sure you have noticed, while

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I make my line a little bit thinner,

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that we have a femur and an acetabulum.

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So here's our femoral head with a

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little notch in it, the fovea capitis,

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where the ligamentum teres inserts.

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Both the pubic and the ischial head.

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When I look at a hip in the coronal

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orthogonal projection, or in the coronal

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oblique, I am looking at the fit

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between the head and the cup.

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People that have a shallow cup, under coverage,

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are more prone to CAM type impingement.

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People that have deep cups may be

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prone to pincer type impingement,

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and the arthritis that goes with it.

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There are conventional radiographic

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measurements for a deep cup.

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But we're here to talk about MRI,

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and you can find these standard

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measurements on any Google search.

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But let's look at these lines as they

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might appear on a radiograph because

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we're going to translate them into MRI.

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Let's start out with this line, which

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is known as the iliopectineal line.

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And then this line right here, which forms a

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loop, which is known as the ilioischial line.

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On a plain film, when the femoral head projects

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medial to this line, so the head projects

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inward this way, that is known as coxa profunda.

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If the femoral head starts to weigh in on

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the center of the socket, and protrudes

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medial to the normal arc of the socket,

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and protrudes into the pelvis.

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You all know that as protrusio acetabuli.

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Now for reference we have

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the ilium right here,

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and the sacrum and the sacroiliac joint.

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Just to get you oriented.

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But here are two other key important lines.

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The anterior aspect of the acetabulum,

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which contributes to this loop on the x-ray.

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Everybody.

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And the posterior aspect of the

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acetabulum, as well as the roof.

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Now, if I simplify my drawing a little

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bit, and I'm gonna go with a nice

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yellow color and a little thicker line,

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let's make our acetabular roof

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in a single planar projection.

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If our acetabular roof is very vertically

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oriented, there's a pretty good chance that

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the femur underneath is gonna be undercovered.

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In other words, the acetabulum

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won't cover it at its drop-off.

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That is one form of a shallow cup.

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But when you have a cup that is not just

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arc-shaped, but up and down, vertically

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oriented, then most likely you have a form

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of developmental dysplasia of the hip, which

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may have gone unrecognized at birth, lasting

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into adulthood, and the patient then presents

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with pretty severe osteoarthritis, or

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the manifestations of CAM-type impingement.

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On the other hand, if you have a very deep cup,

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not only may you see the phenomena of protrusio

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acetabuli, or coxa profunda, you may see

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these big, large, sweeping arcs of acetabulum

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coming around and simply overcovering

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the femoral head in multiple projections.

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The coronal as well as the

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sagittal and even the axial.

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And we'll talk specifically about axial

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overcoverage in a separate discussion

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because that has its own implications.

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A few other critical aspects of

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morphology before we move into the MRI.

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You will hear the term coxa valga.

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In coxa valga, the relationship

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between the femoral head

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and the neck and stem is laid

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out a little more laterally.

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In other words, it goes this way.

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In coxa vera,

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the femoral head-neck junction will

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have more of an angulated appearance,

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a sharp angle between the two.

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Some additional basic terminology.

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Includes the reference of the femoral head to

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the neck, and primarily the shaft of the femur,

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which when angulated out or laterally at or

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greater than 125 degrees, is known as coxa valga.

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The opposite is when this angle between

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the head and basically the shaft

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and neck is angled inward or more

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medially and is 125 to 120 degrees,

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or less.

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Another term you may hear is coxa magna, when

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the femoral head is too big for the acetabulum.

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So you could have a normal acetabular

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size, but it may be too shallow because

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simply, the femoral head is just too large.

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Another term that you might hear is the

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term known as os acetabuli, which in the

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past was considered to be an ossicle

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at the level of the labrum.

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We now know that many of these foci previously

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referred to as os acetabuli are either

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ossifications of the labrum itself or they

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are areas of anterior column spur formation

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that have broken off in the scenario

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of pincer type impingement or type 2.

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So now let's take on some cases.

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You can move on to the next

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vignette if you'd like.