0:00

The other root joint in the upper extremity,

0:03

the Glen Humeral joint.

0:05

And one of the features described years ago was extensive

0:09

erosion involving the lateral aspect of

0:13

the humeral head, a big marginal erosion.

0:16

This was called the hatchet deformity.

0:19

Here's what it looks like on an MR

0:21

with synovitis present within the involved joint.

0:26

Now let's run through some of the differential diagnosis

0:29

of sacroiliitis

0:30

because there are a number of other things

0:32

that can look like it.

0:35

We can see with osteo can then ZZ bone sclerosis

0:40

involving the uh, ileum on both sides.

0:43

Typically in a multiparous woman, occasionally in a woman

0:47

who has not had a child,

0:49

but generally it's in a woman

0:50

following multiple pregnancies.

0:52

The dominant abnormality here in the ileum,

0:56

not in the sacrum.

0:58

And dominant bone sclerosis with low signal intensity.

1:02

Here's another example showing you osteo an ilei

1:07

bilateral symmetrical involvement,

1:10

low signal on the T one low signal also on

1:13

the stir sequence.

1:16

Another problem in differential diagnosis occurs following

1:20

pregnancy, postpartum, sacroiliac joint changes.

1:24

These have been emphasized in our literature

1:26

with MR Imaging over the last 10 years.

1:29

And just to give you an idea,

1:31

I took these particular images from a recent article

1:35

showing you altered signal intensity

1:37

and fluid present within the sacroiliac region

1:43

two days following the uh, pregnancy.

1:47

Okay? And here three months later in a different person,

1:50

you can see extensive abnormalities involving the sacroiliac

1:54

joint region that can simulate the appearance

1:58

of s sacroiliitis.

2:00

Another disorder

2:02

that can produce abnormalities in many different skeletal

2:05

sites, including the sacroiliac region is safo.

2:10

S-A-P-H-O stands for synovitis, acne, pustulosis,

2:15

hyperos, ptosis, and Osteitis.

2:17

And it ties together pustular skin lesions,

2:21

typically involving the feet and the hands,

2:25

but sometimes elsewhere with skeletal abnormalities

2:28

that range in distribution and morphology.

2:32

Typically we see bone sclerosis on radiographs.

2:36

It may be involvement of the clavicle, it may be involvement

2:39

of long or short tubular bones

2:42

or it may be involvement of the sacroiliac joint region.

2:46

Here's a nice case showing you safo in a patient

2:49

with pustular skin lesions

2:51

with abnormalities predominantly involving one

2:55

of the sacroiliac joints.

2:56

But looking at this, this certainly

2:58

Does look like sacroiliitis.

3:01

And to make matters worse, these patients

3:03

with safo may have abnormalities in the spine

3:07

centered in the region of the disco vertebral junction

3:10

looking a lot like spondylitis.

3:13

So this can be a diagnostic challenge.

3:17

Here's another example.

3:19

I'll let you look at this for a moment.

3:23

This is safo pustular skin lesions

3:27

and skeletal abnormalities dominated by bone sclerosis,

3:30

particularly in this region, in one of the joints.

3:34

There's involvement of the other joint as well,

3:37

but you can see this looks a lot like Citis.

3:40

And when you study this with mr,

3:42

it certainly does look like sacroiliitis.

3:45

So this is in the differential diagnosis in children.

3:49

There is a phenomenon seen in T two waiting called flaring,

3:53

typically seen in the sacrum shown here.

3:57

It can simulate sacroiliitis shown in this

4:00

example in children.

4:02

So something to be aware of.

4:06

Psoriasis with sacroiliitis can produce bilateral

4:10

abnormalities and in some cases they are symmetrical,

4:12

as in this example.

4:14

Because of this, we often have to look elsewhere

4:17

and the elsewhere we look is the spine.

4:20

The classic features in psoriasis

4:23

and also in reactive arthritis is something we call

4:28

paravertebral ification.

4:31

These are bulky bony expressives

4:34

that are initially ill defined

4:37

and then become better defined.

4:40

That sweep across the intervertebral disc from a mid

4:44

vertebral body level to a mid vertebral body level,

4:48

representing ossification in the soft tissues

4:51

about the spine.

4:53

And one of the characteristics, at least early on

4:56

as you may have involvement of one side

4:58

and then it skips over to the other side

5:01

and skips back again.

5:03

So that is a very important diagnostic feature of psoriasis

5:08

with involvement of the spine.

5:10

Here I show you two examples,

5:13

psoriatic spondylitis on your left

5:16

and ankylosing spondylitis on your right.

5:19

This is power of vertebral ossification.

5:22

This is what it looks like pathologically.

5:25

Here is ankylosing spondylitis again

5:27

occurring in an older person.

5:29

And these are the syn deses representing ossification

5:34

in the outer fibers of the annulus fibrosis.