0:00

That brings us to the third category that we want

0:04

to discuss in this particular lecture,

0:07

and that is subc chondral insufficiency fractures.

0:10

So once again, let me introduce the terminology that I use

0:14

that describes such fractures.

0:19

The general term is stress fracture.

0:22

It's a general term for a fracture that relates

0:25

to repetitive normal

0:27

or abnormal force placed on normal or weakened bone.

0:32

A fatigue fracture relates to a fracture

0:35

that is involving a repetitive

0:38

abnormal force placed on normal bone,

0:41

and I show you a picture of what that might look like here.

0:44

An insufficiency fracture represented

0:47

by these two pictures is a fracture that relates

0:50

to repetitive normal

0:52

or abnormal force placed upon weakened bone

0:55

to be an insufficiency fracture.

0:58

By that definition, the bone cannot be normal.

1:02

It has to be abnormal bone, whether it relates

1:05

to osteoporosis, osteomalacia, radiation, what have you,

1:09

the bone is not normal.

1:12

So let's talk about insufficiency fractures

1:14

and hear some data taken from the literature to indicate

1:18

that they dominate in the spine, the pelvis,

1:21

and in the lower extremities,

1:23

and in many cases appear in the subchondral bone.

1:27

The most common place that we see them is the sacrum,

1:31

but you can read some of these other numbers as well,

1:33

indicating involvement of the synthesis, pubis, acetabulum,

1:37

femoral neck, femoral head, et cetera, but lower extremity

1:41

and often in the subcon bone.

1:46

We've already commented a little bit about sacral

1:50

insufficiency fractures.

1:51

I may have shown you this particular case

1:53

before we talked about the involvement of the outer aspect

1:57

of the sacrum and the H sign with bone scintigraphy.

2:01

This was an interesting case that I saw,

2:04

saw early on in my career as an academic radiologist at UCSD

2:09

once again, being well trained at Memorial Hospital.

2:14

I looked at this and I was certain this was a chondro

2:18

sarcoma involving the paras al bone

2:22

and we biopsied it, the VA medical center

2:24

and the local pathologist, in fact,

2:27

I think several pathologists agreed with me,

2:29

but we're dealing with a chondro sarcoma.

2:32

We sent it to the A FIP.

2:34

They came back and said, this is not a chondro sarcoma.

2:38

This is an insufficiency fracture involving the paray bone

2:43

with this extensive bone resorption and fragmentation.

2:47

I learned a lot from that case.

2:49

I've never missed an insufficiency

2:51

fracture in this location.

2:53

I've missed several chondro sarcomas

2:55

unfortunately through the years.

2:58

I wanted to show you an example of a stress fracture perhaps

3:01

of the insufficiency type involving the proximal femur.

3:06

I wanted to point out this particular area of compact bone

3:10

that is the calcar, the femoral calcar.

3:13

It's not the medial aspect of the femoral neck.

3:17

It's a plate of bone that is important in uh,

3:21

absorbing some of the compressive forces placed

3:24

on the femoral head.

3:26

And some of these fractures, in fact, will appear as edema

3:29

around the calcar.

3:31

That can be a very helpful sign suggesting

3:34

that the edema relates to a stress fracture.

3:38

The typical appearance

3:39

of a subcon insufficiency fracture is a transverse line

3:44

like this that occurs through the trabecula,

3:47

beneath the subcon bone plate.

3:49

That's the classic, uh,

3:51

appearance described in the literature.

3:54

So we see examples like this

3:57

of a subc chondral insufficiency fracture producing a band

4:01

of low signal, slightly separated from the low signal

4:05

of the subcon bone plate.

4:08

Now, there's another pattern that is not as well known,

4:11

and I wanted to emphasize that,

4:13

and it's a nodular pattern of callous.

4:16

Here's how I would draw it here.

4:18

Taken from the literature, these little dots of

4:22

ovoid increased radio density,

4:25

and where I have seen this most commonly

4:27

is in the acetabular.

4:29

Now, you have to be a little bit careful

4:31

because normally you'll get small dots here

4:34

where trabecula intersect.

4:37

But if the dots get larger

4:39

or there are more of them be concerned that you're dealing

4:43

with an insufficiency fracture in the subchondral bone about

4:47

the acetabulum.

4:48

And in fact, I show you this case which we used on a film

4:52

panel for the International Skeletal Society

4:55

showing you this.

4:57

And of course these are experienced bone radiologists

5:00

and everyone said, gee, that is a classic

5:03

stress fracture in the subcon bone of the aceta.

5:08

And then we showed them the corresponding Mr to point out

5:11

that these dots occurring in the left alium also represent

5:16

a subcon insufficiency fracture.

5:19

So too many dots

5:21

or too large the dots you ought to consider you're dealing

5:25

with an insufficiency fracture.

5:27

Here's another example of the dotted pattern.

5:30

This one occurring in a focal region in the posterior

5:34

superior aspect of the calcaneus.