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<v ->Now I wanna go back to a case of the acetabulum

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and once again I'm showing you a case

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that I showed on a quiz panel

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of the International Skeletal Society

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a number of years ago.

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I'm sure you all realize that when I show it on a quiz panel

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I won't include these arrows

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to give them an idea of what's going on,

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but for the experts who form the panels

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for a quiz panel at the ISS,

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you're dealing with very smart people.

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So there's no question as they looked at this,

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and I showed them the right and left side,

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that they were gonna detect this man of increased density,

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because I think even some of my residents

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would immediately pick that out

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as evidence of a stress fracture,

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probably of the insufficiency type.

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So you might wonder why did I possibly show this case

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to these experts, these teams of experts

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at the ISS film panel?

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Well, because it was an interesting case.

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I then showed them the MR and this was bilateral

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and I was showing it to indicate

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how subtle the insufficiency fracture can be.

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These are just too many nodular areas, right?

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You can see beautifully how that shows up on the MR.

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The one on the other side, the right side, far more evident.

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So yes, they got this right, but not immediately.

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They all concentrated on one side

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and did not initially pick up

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the fracture on the other side.

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Earlier in this course I talked about the appearance

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of insufficiency fractures in the sacrum,

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which is the common site in the osteos pelvis.

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These fractures involve the periphery of the sacrum,

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generally, bilateral, not always symmetrical.

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Here you can see it with conventional radiography,

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quite subtle, well shown on CT,

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on the bone scan, again that Honda, or capital H sign,

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and on MR a nice demonstration

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of the lateral location within the sacrum.

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Now I'm showing you this case

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which brings back painful memories to me.

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I arrived in San Diego, well, many years ago,

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as the only skeletal radiologist at UCSD, and sure enough,

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within the first week this case came through.

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Being well trained in New York

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and having spent a lot of time

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at Memorial Sloan Kettering Cancer Hospital,

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I knew all about bone tumors

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and immediately saw this aggressive process

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and said, you know, we're dealing with a chondrosarcoma here

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involving the parasymphyseal bone.

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They did a biopsy of this

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and it was read locally as a chondrosarcoma.

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But in those days, all of the malignant tumors were sent off

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to the AIFP, the pathology Institute in Washington, DC,

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and sure enough, within a week or so,

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this came back and said, this is not a malignant tumor,

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this is an insufficiency fracture

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involving the parasymphyseal bone.

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Showing you the degree of bone destruction

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and disorganization that can occur.

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I learned a lot from that case.

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I've never missed an insufficiency fracture

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in this location since.

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I've missed a few chondrosarcomas however, in this location.

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We even published articles

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showing you that these insufficiency fractures

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and fatigue fractures,

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about the parasymphyseal bone,

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can be very, very aggressive looking,

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as you can see here, initial radiograph and six weeks later.

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Insufficiency fractures also can involve

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the subchondral bone of the femur, shown here,

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again with perhaps a second insufficiency fracture,

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very small, on the acetabular side.

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Tetyana Gorbachova, who was a clinical fellow of ours,

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currently located in Philadelphia,

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wrote a very nice article about insufficiency fractures

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occurring in the subchondral bone about the knee.

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And she described three patterns.

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Pattern one was a hypointense line.

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Remember these fractures involved the subchondral bone,

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they may later merge with the subchondral bone plate,

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pattern two, producing a thick subchondral bone plate.

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And pattern three where you seem to have both.

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Those were the three patterns that she came across.