Rheumatoid Arthritis: The Convergent Talus Episode 2

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Clinical Summary

• Rheumatoid Arthritis Impact

  • Classically associated with forefoot deformities (hammer toes, hallux valgus), but midfoot and rearfoot involvement are underrecognized.

  • Disease mechanism: synovial-based antigen–antibody process forming pannus → symmetrical cartilage destruction, periarticular erosions, and subchondral cysts.

• Midfoot Involvement (TMT 2–3 joints)

  • Central column destruction destabilizes the foot.

  • Compensatory peroneus longus activity plantarflexes 1st metatarsal, leading to closed kinetic chain supination and heel varus.

  • Coleman block test distinguishes forefoot-driven varus.

  • Surgical approach:

    • TMT 2–3 fusion with grafting (due to bone loss).

    • First metatarsal elevational osteotomy to restore heel alignment and correct closed kinetic chain deformity.

• Rearfoot Target Joints

  • Talonavicular (TN) Joint

    • Symmetrical pannus-related cartilage loss vs. asymmetric OA.

    • Leads to medial column shortening and mild forefoot adduction.

    • Usually requires isolated in-situ TN fusion with grafting.

    • Foot often remains relatively rectus; minimal supinatory effect.

  • Subtalar Joint

    • Disease may involve posterior, anterior/middle facets, or entire joint.

    • Posterior facet involvement → severe destruction, ligament damage (spring, cervical, interosseous talocalcaneal), potential divergence/dislocation.

    • Anterior/middle facet involvement → medial-sided destruction, heel varus, talar convergence.

    • Surgical approach:

      • Subtalar arthrodesis with medial distraction bone grafting to elongate talus–sustentaculum distance.

      • Possible dwyer osteotomy adjunct if residual varus persists.

      • Bioengineered struts may be used for structural support.

• Clinical Recognition & Diagnosis

  • Rearfoot disease may precede forefoot deformities in rare cases.

  • Advanced imaging (CT, MRI, serial radiographs) essential for detecting early TN or subtalar pathology.

  • Cases exist where rearfoot changes led to initial RA diagnosis.

• Modern Context

  • With biologic therapies, severe forefoot destruction is now less common.

  • However, podiatrists should remain vigilant for midfoot and rearfoot rheumatoid changes—especially talonavicular and subtalar joints—as they may present first.

Transcript

Welcome back to Podiatry Today Podcasts where we continue to bring you the best in foot and ankle medicine and surgery from leaders in the field. We're welcoming back Dr. Visser with us today to continue our conversation on the convergent talus and let's get into a couple more of these topics and scenarios that lead us back to the same foundational information. He was the President of the St. Louis Podiatric Medical Society and he is also a Past President of the Missouri Podiatric Medical Association. He has served as an eEaminer of the American Board of Podiatric Surgery and served on the Missouri State Board of Podiatric Medicine over several governorships. In addition, Dr. Visser has been a residency director for 40 years, most currently at SSM DePaul, Foot and Ankle Reconstructive and Trauma Surgical Program in St. Louis, Missouri, where he has trained at present 114 residents. He was also in 2015 inducted into the Kent State University School of Podiatric Medicine Hall of Fame. Why don't we talk a little bit about rheumatoid arthritis? Does that play into this consideration at all?

Yes, rheumatoid arthritis is a very interesting issue when it comes to the so-called convergence of the talus. We are kind of taught when we come to think about rheumatoid arthritis is the severe forefoot deformities, the hammer toe deformities, the severe hallux abductovalgus deformities, okay? And it's never much been accentuated.

What happens to the rheumatoid midfoot, for example, or what are target joints in the rearfoot?

This is something that, as I question my residents often, they have no real clue about any of this kind of thing. When it comes to the midfoot you'll see an interesting thing occur occasionally and again this is not something that's relatively common but it can occur and when you do see involvement it tends to be destruction of the TMT 2-3 joints which would be the central column of the foot. As we know in the rheumatoid process it's a synovial based disease state, an antigen antibody issue that forms what we call pannus formation, which destroys the cartilage in a symmetrical fashion because the pannus encompasses the entire contents of the cartilage inside the joint. Also, the periarticular structures, the capsule which comes out outside of the cartilage can be the first thing that gets involved with basically subchondral cysts and basically erosions that occur, which occur first and then you begin to see this symmetrical destruction of the joint. In this particular instance, when this joint is involved in this way, what happens is the medial column will then attempt to help stabilize this loss of stability of the central column. And what will happen is then the peroneus longus, this will begin to fire, to plantar flex the first metatarsal to help maintain arch integrity, okay? Once the first metatarsal is plantar flexed, it then can have a retrograde effect on the subtalar joint and create what we call closed kinetic chain supination, which will lead to a heel varus.

That's so interesting. Can you share a little bit more about that?

Now the heel varus needs to be determined. Is this a forefoot-driven problem? And in that particular case, if on Coleman's block test, we dropped out the first metatarsal over the edge of the block. And basically we indicated that the heel came to a vertical or pronated position. Then what we understand then is that this is a forefoot-driven problem. And so if indeed we had that developmental convergence happened because what happens for the heel to get in that supinated position, the talus has to dorsiflex and abduct, we would have to potentially consider not only with a fusion of the TMT 2-3 joints, which usually involves grafting, because of the fact of destruction of the bases of these joints and their bone loss, with this, that they will have to potentially also have a platform reconstruction. And that would require, in this case, basically, an elevational osteotomy of the first metatarsal. Because by elevating the first metatarsal, the heel will come to a vertical position. And thus, close kinetic chain supination will be replaced by close They change pronation and the heel will come to a normal corrected position. So this is a very interesting case that can affect the midfoot. It's not common, but interestingly, if you start looking for it in the rheumatoid, they're more often than you may think.

Are there any other anatomic areas that show up here that we need to be aware of?

The other two target joints in the rear foot that a lot of people don't consider are the talonavicular joint and the subtalar joint. In the case of the talonavicular joint, the so-called pedis acetabuli, we have this big cup and cone joint basically. And what happens, pannus involves the joint, We have symmetric loss of the joint space because a pannus destroying the hyaline articular cartilage in a symmetrical fashion, as opposed to osteoarthritis, which is an asymmetric breakdown of the cartilage. And we'll get into more discussion about that as we discuss some of these other issues. And basically what happens then is we get a shortening of the medial column. The the cartilages eroded away depending on how aggressive and how long the process is. Subchondral bone can be destroyed. So we begin to start to see shortening of the medial column. Now, interestingly with this, because we're getting bone loss with the shortening, we will get obviously some adduction to the forefoot, But we really don't get much issues with a close kinetic chain supernatory effect because of loss of bone. If we didn't have that and it was a mild tenderness issue, then certainly, yes, we would probably be looking at something like that. So interestingly with this, the foot position basically develops a little bit of an increase in its ..., but not significant to create any kind of a posterior subtalar joint or rearfoot issue. So basically, the approach here would be a isolated in-situ fusion of the talonavicular joint, again, usually involving bone grafting because of loss of bone contact when the procedure is actually being performed. There is a bit of an induction component that needs to also be corrected when this procedure is being performed. But in essence, the foot maintains a relatively rectus appearance.

Can you talk a little bit more about the subtalar joint in this respect?

It can in fact, basically the posterior compartment of of the subtalar joint, which would include the posterior facet, or it could include the anterior and middle facet. Sometimes it can involve panfacet involvement, but there are instances where isolated facet involvement occurs. And what does this mean? Well, if it involves the posterior facet, then we're going to see a significant destruction of the posterior facet and the supporting structures of the subtalar joint. That includes the contents of the canalis tarsi, the interosseous talocalcaneal ligament, the cervical ligament. These are all going to be greatly damaged, the spring ligament, and we're actually going to see a very severe divergent form of the subtalar joint where it basically subluxes out of its mortise oftentimes, and at times can be dislocated. But there can be instances where only the anterior and middle facet or the anterior compartment are involved.

In this particular instance, then what happens?

With the destruction there, the contents of the canalis tarsi are not heavily involved here. It gets isolated to the medial side of the foot, the medial side of the subtalar joint. And with bone destruction, loss of cartilage there and loss of subcondral bone, what it does cause is the heel to tip into varus, okay? And as the heel tips in the varus, the talus becomes more convergent. It moves into a dorsiflex adducted position and we will get a varus deformity of the subtalar joint in that particular situation. In this particular case, a full subtalar joint arthrodesis will need to be performed in this particular case. And the way it is done primarily is by using bone grafting on the medial side to elongate the distance between the inferior neck of the talus and the, obviously the sustentaculum, of which it articulates underneath. If your CT scan shows the posterior facet not heavily involved, then the fusion would only need to be done on the medial side of the foot, okay? And if you found that your heel varus was not fully corrected with this elongating bone grafting procedure or using a strut, which can be bioengineered where we have now bioengineering and we're using struts in these particular instances. We may need to do a Dwyer osteotomy in combination, but in most instances, because the posterior facet is still mobile and not involved in the disease process, we will get an actual correction of the healed position by an elongation, distraction fusion on the medial side of the subtalar joint. Something that does not happen often, but I have had at least two cases in the last five years where the patient presented with an adductocavovarus foot deformity, talar convergence, basically people not having a good understanding, she had seen other practitioners, did not have a good understanding of what was basically going on in this particular situation and they were baffled and couldn't figure it out and basically this is the description how that can occur.

So with the rheumatoid when it comes to involvement. In the midfoot, we have that TMT 2-3 issue, and then certainly conditions that can affect the TN joint and the subtalar joint, which are target joints in the rearfoot. Now they do occur later than the forefoot changes, but as we know with biologics that are used nowadays, We are not seeing anything like we used to when I first came out where we saw severe destruction of the forefoot. And again, forefoot always usually seems to supersede the rearfoot involvement. But there are instances where the rearfoot may present in an initial form. And I've had at least five cases where the patient presented with telenovicular involvement had no diagnosis of rheumatoid arthritis and was diagnosed by the serial x-rays, the MR, and the CT scanning. So rheumatoid arthritis is very interesting in the way it can affect the foot.

Well, rheumatoid arthritis certainly has a lot of complexity by itself, but when it comes to the context of the convergent tailless, it has even more so. Thank you so much for sharing your expertise with us here in this area, and we look forward to future episodes where we're going to dive into even more related conditions when it comes to the convergent talus. You can find this, past and future episodes of Podiatry Today Podcasts at podiatrytoday.com are your favorite podcast platforms like Apple Podcasts and SoundCloud. We hope you'll join us next time.