Eva Reidemeister​

Interviewer

Denis Poddubnyy

Rheumatologist

Expert Interview:

Osteitis Condensans and the Pitfalls of Sacroiliac Joint Imaging (Part 2: Management and Treatment)

This second part (➡️ part 1) of our expert interview turns to the management and treatment of osteitis condensans ilii (OCI). The rheumatologist Denis Poddubnyy explains why the condition is challenging in clinical practice – and which treatment options may help patients.

Eva Reidemeister: We’ve already touched on this in the previous part: But are there any guidelines for osteitis condensans ilii yet? After all, the condition hasn’t been studied very well yet.

Denis Poddubnyy: Unfortunately, there is virtually nothing available on osteitis condensans ilii to date. There are some smaller studies, including one of our own, where we attempted a cross-sectional comparison of axial spondyloarthritis with osteitis condensans ilii. Despite the relatively small sample sizes, I believe we have identified the most relevant aspects, both clinically and in terms of imaging.

What we still don’t know is, first of all: What is the course of this disease? Are there self-limiting courses where the symptoms eventually subside, or do the symptoms persist? And: Is back pain always a part of it? And secondly, there are still no studies on how best to treat this disease and who is best suited to treat it.

In Germany, the situation is such that as soon as it is determined: This is not an inflammatory condition…

Eva Reidemeister: …you can really only administer painkillers.

Denis Poddubnyy: Yes, and rheumatologists are also losing interest in treating this condition. This is partly because rheumatologists are in short supply and are expected to focus on “true” inflammatory diseases. But seriously: These patients end up seeing orthopedists and are prescribed painkillers. But I think that, because bone marrow edema is often present, these cases require not only painkillers but also medications with both pain-relieving and anti-inflammatory effects, such as nonsteroidal anti-inflammatory drugs.

Eva Reidemeister: So, would those actually help?

Denis Poddubnyy: Yes, there are certainly situations where they do help. But on their own, they won’t improve the situation in the long term. The medications would, however, be important for managing symptoms so that the pain doesn’t become chronic. At the same time, though, you have to try to restore stability in the pelvis somehow, for example through physical therapy. Of course, performing physical therapy exercises regularly must not be accompanied by acute pain. That is, you must not make any movements that trigger acute pain. In that case, the combination most likely to be recommended to affected individuals is physical therapy plus nonsteroidal anti-inflammatory drugs.

In addition, there are repeated attempts to improve stability in the sacroiliac joint through pelvic belts, through screw fixation, or through fusion of the sacroiliac joint. However, the studies on this are quite limited. And in my view, this would be the last resort for this condition – the very last thing one would consider. Experience shows that surgical intervention, in particular, does not solve all problems. I would always try to proceed with conservative measures first.

Eva Reidemeister: So we don’t have much information yet on the risk factors, but we also don’t know much about this disease in general. And one challenge is probably that the condition is simply very rare. As a result, there aren’t that many patients to study. Or where do the challenges in research lie?

Denis Poddubnyy: I think there are several factors at play here. Personally, I don’t think the disease is all that rare. It has become one of the most important differential diagnoses [for axial spondyloarthritis]. But the challenge lies in recognizing it and telling it apart from axial spondyloarthritis. The second challenge is: Who is responsible for these patients? Because here we find ourselves right at the intersection of orthopedics and rheumatology. Rheumatologists say: This isn’t inflammatory, so it’s not our area. Orthopedists, of course, have other priorities. So affected patients are left in limbo between two worlds.

But because the condition is so important to rheumatologists [as a differential diagnosis], rheumatologists – and radiologists, of course – need to launch the necessary studies. That includes long-term studies on disease progression and treatment efficacy. That would be very important. We need to convince potential sponsors that this is a significant condition that places a considerable burden on those affected. I’m convinced of that. But we need more data to back it up.

Eva Reidemeister: Perhaps a somewhat technical question regarding research: At the beginning, you mentioned that the conditions are actually better identified on X-rays. That might be surprising, since X-ray technology is generally considered somewhat “old-fashioned” in imaging – MRI and CT are, after all, more modern. Does this amount to a case for why X-rays remain important?

Denis Poddubnyy: Well, if you know how to tell osteitis condensans ilii apart from axial spondyloarthritis on MRI, it’s not a problem. But I also believe we have this problem of misdiagnosing osteitis condensans ilii as axial spondyloarthritis precisely because MRI is used more often and X-rays are no longer taken. With X-rays, bone marrow edema is unlikely to be misdiagnosed as axial spondyloarthritis. With MRI, there’s a much higher chance that bone marrow edema will suddenly be misread as a sign of axial spondyloarthritis. However, X-ray imaging has many drawbacks when it comes to diagnosing sacroiliitis and can also produce false-positive results.

So where resources allow, the trend is toward cross-sectional imaging such as MRI. We’re also training radiologists and rheumatologists to tell the different processes in the sacroiliac joint apart, so that misdiagnoses can be prevented.

However, there are certainly countries where, for example, the health care system doesn’t allow an MRI scan right away. And that’s perfectly fine. It’s entirely legitimate to start with an X-ray and to refer the patient for cross-sectional imaging only if the findings are unclear or inconclusive.

MRI is now the gold standard for the diagnosis or differential diagnosis of axial spondyloarthritis. It’s important that the protocol includes an erosion-sensitive sequence, so that erosions can truly be detected or ruled out. Even with today’s protocols, that’s not always a given. We’re also working to show rheumatologists and radiologists how important erosion-sensitive sequences are. That can sometimes spare patients a CT scan. In the past, CT was the gold standard for imaging structural changes in bone, particularly erosions. By now, MRI has caught up with CT and can image bone changes essentially as well.

I’ve also prepared a case study that applies various imaging methods. It’s the case of a 45-year-old woman who was referred to us by the orthopedics department to find out whether she has Bekhterev’s disease [an outdated term for ankylosing spondylitis, the radiographic form of axial spondyloarthritis]. The suspicion arose because she has long-standing back pain with inflammatory features. Her medical history tells us: There’s a family history of Bekhterev’s disease, and she is HLA-B27 positive. She has no physically demanding job or hobbies, and she has two children.

At events where I’ve shown this X-ray, even experienced rheumatologists have said, “This is clearly a case of Bekhterev’s disease.” Because here you can’t see the joint space, so it’s ankylosis – and therefore axSpA.

That’s precisely the danger with X-rays: You can clearly see the triangular sclerosis here. But you cannot clearly see the joint space. That’s why you need cross-sectional images.

The case also includes a few cross-sectional MR images. STIR (this is the third series of our case) is a sequence optimized for fluid retention and inflammation, where you can see the bone marrow edema. In this sequence, however, you can see the structural changes. There is massive sclerosis. But it is impossible to say whether there is erosion or ankylosis present. The actual resolution is only achieved by using a sequence optimized for erosion, a so-called VIBE sequence, where one can see that the joint space is well preserved.

In this case, there is also further evidence that our theory regarding instability in the pelvic ring, specifically at the sacroiliac joint, is likely correct – and that is this capsular ossification. It occurs only when the joint is unstable and moves more than usual on a constant basis. Normally, there is only one to two millimeters of movement in this joint. If it increases, this is perceived as mechanical stress. This, in turn, leads to ossifications or bony spurs, similar to those seen in osteoarthritis. That is why it is now said that osteitis condensans ilii is actually an extreme form of osteoarthritis. In the anterior, ventral region – where mechanical stress is greatest – both typical features of osteitis condensans ilii are visible: sclerosis and edema.

Eva Reidemeister: So we’ve come back to the terminology – with osteitis condensans ilii possibly being a type of osteoarthritis. With Bekhterev’s disease, we see how names can change over time: Today we speak of axial spondyloarthritis, or of ankylosing spondylitis when the bone changes are visible on imaging. Could something similar happen here, so that OCI eventually goes by a different name altogether?

Denis Poddubnyy: Well, to be honest, I would have preferred to stick with the old terminology for axial spondyloarthritis [Bekhterev’s disease]. There’s so much confusion. When you introduce new terminology, you really have to think very, very carefully about why. Well, in the case of axSpA, there were actually good reasons. The goal is to emphasize the inflammatory nature of the disease rather than its ankylosing nature. Here, I think if we stick with osteitis condensans ilii, that would be fine. The main thing is that we understand what it is and can recognize it.

Eva Reidemeister: If that isn’t a fitting closing remark! Thank you very much, Denis Poddubnyy!

This concludes our expert interview with rheumatologist Denis Poddubnyy on osteitis condensans ilii (OCI) as an important differential diagnosis for axial spondyloarthritis. The journey took us from the challenges of imaging and clinical decision-making to current treatment options, and it points to the gaps that remain – gaps that only more long-term research can close.

If you’d like to keep learning, the BCV Online Academy offers video lessons and case collections that take you further.

Go to BCV Online Academy
Read Part 1: Diagnosis

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