0:00

Let's move on to our second category,

0:03

and that's the category of transient osteopenia.

0:07

Once again, I'd like to begin

0:08

by talking about the terminology that we use to describe

0:13

this and related entities.

0:15

Osteoporosis represents qualitatively normal,

0:20

but quantitatively deficient.

0:22

Bone osteomalacia relates

0:25

to decreased bone mineralization with the presence

0:28

of non mineralized os.

0:30

Osteo seams.

0:32

Radiologists for years, for decades,

0:35

had trouble distinguishing between osteoporosis

0:38

and osteomalacia.

0:39

So in part they solved the problem

0:42

by introducing a third term.

0:44

And the third term was osteopenia,

0:47

which simply meant radiographically the bones

0:50

were too lucid.

0:51

So now you had a term that covered both osteoporosis

0:54

and osteomalacia, perhaps eliminating the need

0:58

for the radiologist to figure out which one was present.

1:02

But I would maintain in many cases,

1:04

and here I show you the spine, you can tell the two apart.

1:08

When you deal with osteoporosis, you often have resorption

1:12

of horizontal trabecula

1:14

and accentuation of the vertical trabecular.

1:17

When you deal with osteomalacia, you have a hazy interior

1:22

to the vertebral body.

1:23

When you deal with osteoporosis, you may have collapse

1:27

of one vertebral body more than a neighboring vertebral

1:30

body, whereas with osteomalacia,

1:32

they often collapse a similar degree

1:35

as you compare one vertebral body with its neighbors.

1:39

And when you deal with osteoporosis, often one side

1:42

of the vertebral body is collapsed more than the opposite.

1:45

When you deal with osteomalacia, typically the top

1:48

and bottom of the involved vertebral bodies, in fact,

1:53

are involved to the same extent.

1:54

So there are differences,

1:56

but if you're not sure,

1:57

you can always use the term osteopenia.

2:01

Now, when we talk about osteopenia

2:03

and specifically about osteoporosis,

2:05

we often divide it into three categories.

2:08

The first of these is generalized involving most

2:11

of the bone, but dominating in the axial skeleton.

2:14

And I've listed here some of the things, the disorders

2:18

that can produce generalized osteopenia.

2:22

We also talk about a regional pattern of osteopenia

2:25

or osteoporosis where one

2:28

or several extremities are involved.

2:31

Okay? Sometimes on a transient basis.

2:34

In the slides that follow,

2:36

I'll be emphasizing this particular form

2:38

of regional osteopenia.

2:41

And then we include localized osteopenia or osteoporosis,

2:45

because sometimes about other disease processes,

2:49

you will find histologic evidence of too little bone.

2:54

So these are the general categories.

2:56

Our job today is to emphasize

2:58

Transgen osteopenia.

3:01

So let's go back to the original description of

3:03

what was called Transgen osteoporosis of the hip.

3:07

The author was Michelle Deca,

3:09

someone I knew he was a radio rheumatologist,

3:12

good at both radiology and rheumatology.

3:15

And in 1968, he described

3:19

10 patients varying in age with the rapid development

3:22

of pain, limp, and disability typically involving one

3:27

or both hips, less commonly both hips who demonstrated.

3:31

And these are images taken from his original paper,

3:34

what appeared to be localized osteopenia.

3:38

He called it osteoporosis, involving the femoral head.

3:41

And typically what would occur is the clinical findings,

3:44

which were pain, a limp,

3:47

and disability as well as the radiographic finding

3:50

of osteopenia would resolve over a period of time,

3:54

typically an average period of uh, two years.

3:58

So if we go back to the typical uh, characteristics,

4:03

clinical and imaging characteristics of

4:05

what was originally called transient osteoporosis of the hip

4:10

men more common than women, young and middle aged typically,

4:15

and a woman as shown in the case, I'm illustrating

4:18

in late pregnancy

4:19

or postpartum here in late pregnancy,

4:22

you can see the loss of bone.

4:24

It's hard to identify the subchondral bone plate.

4:27

Three months later, pregnancy ended at that point.

4:32

And you can see now

4:33

that the bone mineral has to return to normal.

4:36

These patients usually had pain, a limp, limited hip motion.

4:41

We saw the osteopenia in the femoral head and neck, and

4:45

although self-limited, okay, as I've already mentioned,

4:48

it might affect another region, typically the opposite hip

4:53

or some other location usually in the lower extremity.

4:58

So this was a phenomenon in the lower extremity,

5:02

typically involving the hip.

5:06

Along came MR Imaging in the 1980s,

5:08

and this article appeared out

5:10

of the Mallinckrodt Institute in St.

5:13

Louis when they applied MR Imaging to patients who seemed

5:17

to have trans in osteoporosis.

5:19

And when they did,

5:21

and they applied it not just a hip involvement,

5:23

but also to a similar phenomenon occurring about the knee.

5:27

When they did that, the imaging features were that of edema

5:32

or edema like uh, alterations.

5:35

And so they proved that when you had trans

5:38

and osteoporosis,

5:39

often the MR equivalent was transient marrow edema.

5:44

Here's a typical example of what it looked like.

5:46

These are old images, but they're beautiful images.

5:50

So when looking at transit marrow edema here involving the

5:54

proximal femur, low signal on

5:56

T one, high signal on the fluid sensitive sequences,

6:00

and I want to call your attention to two things.

6:03

Number one, in some cases the medial aspect

6:06

of the femoral head may not be involved.

6:08

That was emphasized in some

6:10

of the early articles on the subject.

6:12

And number two, how far down

6:16

or extensive the marrow edema

6:18

and even the low signal may be on the T one weighted images

6:22

that could be dramatic.

6:25

Then along came Yamamoto

6:28

and other colleagues and said, wait a minute.

6:30

When you look at these examples of trans osteoporosis

6:34

of the hip, as he did in 2001,

6:37

looking at 12 hips in 11 patients,

6:40

that when you look carefully at them,

6:43

what you really saw was a subcon insufficiency fracture.

6:47

Hence, he believed that this condition

6:50

of osteopenia related again to an insufficiency fracture.

6:55

Now, I know, uh, I go, uh, we,

6:57

we argue a bit in our own practice at UCSD

7:01

because I'm of the belief that

7:03

that doesn't prove the insufficiency fracture caused

7:06

the marrow edema.

7:07

You could argue, and I do that perhaps the osteopenia

7:11

and the marrow edema occurred first weakened the bone

7:15

and then an insufficiency fracture occurred in the subc

7:19

chondral bone because it's remarkable how much

7:22

of the bone may be abnormal when we're only dealing

7:25

with a very small, even microscopic insufficiency fracture.

7:31

So perhaps in fact, the marrow edema

7:34

and the osteopenia curve first.