A Cable Approach to Peroneal Dysfunction

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Transcript

Jennifer Spector, DPM, FACFAS: Welcome back to Podiatry Today Podcasts, where we bring you the latest in foot and ankle medicine and surgery from leaders in the field. Today we're thrilled to have with us Dr. John Visser to talk with us about a cable approach to peroneal dysfunction. Dr. Visser is a Diplomate of the American Board of Foot and Ankle Surgery, as well as a Diplomate of the American Board of Podiatric Medicine. He's a Fellow of the American College of Foot and Ankle Surgeons. He's a Past President of the St. Louis Podiatric Medical Society and the Missouri Podiatric Medical Association. Dr. Visser has served on the Missouri State Board of Podiatric Medicine, where he's been appointed by three governors. He's a past Director of Residency Training in foot and ankle surgery at Mineral Area Regional Medical Center and later at SSM DePaul Health Center in Bridgeton, Missouri. Welcome Dr. Visser and thank you for being with us today.

John Visser, DPM, FACFAS:Thank you, it's an honor and a pleasure.

Dr. Spector: Well, this concept that you've explained to us and that we're going to get into today is really interesting, so I would love it if first could you briefly share the basic concept of the cable approach to peroneal dysfunction?

Dr. Visser: Yes, I think we tend to throw the peroneal tendons kind of under the rug. Everything's always been, and you hear just a lot of literature and talks about tibialis posterior dysfunction, the so-called progressive collapsing foot deformity, of which it's become just one of many things that could cause that condition. When I think about peroneal dysfunction, I think of it as a situation of progressing, elevating foot deformity. Elevation meaning that with the dysfunction and tears from tendinosis of the peroneal tendons, the patients develop an adducto-cavovarus foot. And the fact that often surgeons fail to recognize preoperatively when the patient presents with a peroneal problem or a peroneal tear that it may be related to a varus reducing deformity at the foot and ankle that really has to be evaluated. And at times, adjunctive surgery needs to be done in combination with repair of that particular tendon.

Dr. Spector: Can you start us off by talking a little bit about some anatomic and biomechanical considerations?

Dr. Visser: I do run a residency program and I have 15 residents under my helm so teaching is very important to me and I do really accentuate peroneal dysfunction. Basically the doctor goes in, repairs the tendon, doesn't do much more to that. There's been nothing more to do. In fact, you have to really, really evaluate that patient very, very carefully. We know preoperatively a patient with so-called peroneal dysfunction or if we’re concerned about they have a peroneal problem, they can have instability. This can be one of their complaints. And of course, instability tends to correlate with lateral ligament instability, but in fact, peroneal dysfunction can also be a big player. The other thing I would point out about the peroneals in general it's because of the fact that we get so much literature about tibialis posterior dysfunction and that the peroneus brevis is aplayer there which it is because once the TP tendon is not functioning well, the brevis has some mechanical advantage so you get this idea that the peroneus brevis is a much stronger muscle. In fact, it's the weaker of the two peroneals. The peroneus longus, in fact, is the strongest of the two. It carries about 33% stronger.

And this is a factor when we start considering things that where we have loss of one tendon, we consider transfers. The longus is a very good muscle for transfer, especially with the weaker brevis. What I'll start off with is just to kind of review the anatomy really quickly here. I'm sure you're familiar with the location of the peroneals in what I call the A zone. You have the peroneus longus being the most superficial and then you have the brevis and then the tendons pass in what's called the retrofibular groove and that's the so-called A pulley. And that area is probably going to be the most common instance where you have a problem with the peroneal tendons. And probably the most common instance that you'll have an issue with a peroneal tendon is the brevis there in that area of the retrofibular groove.

Injuries such as various instability deformities like ankle sprains or patients who have varus states to their foot, it will lead to traction on the superior peroneal retinaculum. And this can lead to the fact that that retrofibular groove is not stable and the tendons can move out of that groove into an area where the fibula basically has a longitudinal zone that is sharp. And the tendon, the one lying closest, that being the brevis, can come in contact with that and lead to a longitudinal split tear.

Dr. Spector: So, what options exist if this is the case?

Dr. Visser: Once that tear occurs, there's not much you can do because the longus is right behind it and it's going to fill that defect and so there's just no way conservatively you could do anything with that. So, at the A pulley, as we say, we look at the brevis heavily, once in a while we'll see a longus issue, but not much. There is one other thing that does pop up now, which is basically instability of the peroneals, where there's no tear to the brevis or the longus, yet patients have swelling, They have pain there, they'll get an MRI, an MRI is completely negative. And if you do ultrasound, you'll see what happens is, again, the superior peroneal retinaculum is unstable, they're shifting of the brevis out of the out of the notch or the retrofibular groove. And what happens is the longus and the brevis switch over on each other, where the longus basically then falls underneath the brevis.

An interesting thing, and something that you have to be suspicious of clinically, lot of these patients will go undiagnosed yet they'll have chronic pain, and it's obviously up to you to try to sort that out. So, this A pulley area does seem to be particularly important when it comes to this pathology.

What else should surgeons keep in mind one thing to remember in this A pulley area is to look at things that could cause Insufficiency there. You have the retrofibular groove which is usually concave, but sometimes it'll be flat or convex This will basically lead to the brevis wanting to slip out of that notch Also low-lying muscle bellies - on occasion I will get a patient, in about 10 to 20% of cases, where they'll have a peroneus cordus that will run down into that retrofibular groove and then obviously cause it to slip out of the notch. The biggest thing that you need to look at is the sufficiency of the superior peroneal retinaculum. This you test once you open the incision and you basically, before you make the incision, you dorsiflex and abduct the foot and ankle and you will see subluxation occur. The other thing to look for then is obviously the low-lying peroneus brevis muscle belly. This is important because a lot of times you don't look at this, it fills the retrofibular groove and it leads to crowding and subluxation and this can lead to these longitudinal split tears.

Dr. Spector: So going back to the biomechanics for another minute, what other types of deformities or conditions do you find that surgeons need to be aware of when it comes to really working up these disorders properly?

Dr. Visser: The other thing to keep in mind here, and I'll go over them now, are the so-called mechanical conditions that affect the foot and ankle, the so -called elevation states, that can lead to instability in the area of the peroneal tendons. Those being, for example, patients who have a fixed calcaneal varus deformity, or they may have a subtalar joint arthritic condition that leads to lack of overall pronation in a varus state. Instability situations where the collateral ligaments are unstable. You look at it anatomically with stress views and you will see either the ATF ligament on an anterior drawer is insufficient or a positive talar tilt on a calcaneal fibular stress view. These are anatomic variants that lead to a lot of instability and they need to be addressed. This is where a Brostrum and anatomic repairs become important. And then obviously the other thing we look at is the so-called subtle cavovarus foot with a plantar flexed rigid first ray, possibly an equinus player there. And obviously plantarflexion of the first ray and adduction of the foot. If these are present, these structural matters need to be addressed. This is where we can use the Coleman block test. We can figure out whether we have a forefoot driven problem, which is kind of rare, where the first metatarsal is rigidly plantarflexed. And when we drop it out over the edge of the book, we find that the heel comes to vertical, indicating the varus of the heel, which is what our real concern, with peroneals unstable from the forefoot. So, if we had that situation, we would just have to address the first ray by an elevation osteotomy of the first metatarsal or a first met-cuneiform elevation osteotomy. And we would then address the rearfoot instability in the varus state, which is affecting the peroneal tendons. Often though, however, in these conditions, we drop out the first metatarsal and the heel remains in a fixed varus position. There, obviously, we need to work up why that's happening. Is it from arthritis in the subtalar joint? For example, maybe a coalition, maybe an old injury. Is it a congenital state … leading to loss of pronatory function or do we have a structural heel varus where the body of the heel on an axial view appears in a varus position that cannot be brought to vertical. These things all have to be looked at because if they are there then we're going to address the peroneal tendons.

Then, obviously, we have to make sure that these are properly addressed - the lateral ligaments with the Brostrum repair. If you do get a situation where you had a patient that you did a Brostrum, it failed. You had to go back in and do the tendons. Again, that's where the non-anatomic repairs like a Christman Snook are useful. I will still use a Christman Snook on a patient that's over 300 pounds. I don't think an anatomical pair is going to do the job.

Dr. Spector: What other adjunctive procedures might you employ?

Dr. Visser: If I have varus heel, I'll consider a Dwyer osteotomy, or if the subtalar joints are through, they come going to consider going ahead and doing a lateralization subtalar joint fusion to to bring the varus state into a more of a rectus position in these cases.

The other areas that we'll talk about are the B pulley area. This is the calcaneal tubercle. And remember now, with that, there's a switchover. What happens is the longus, which at point A, the point A pulley, basically is more superficial, It falls inferior to the tubercle where the brevis goes superior to it. Again, the tubercle oftentimes when there's a problem at this level is enlarged, and it's usually associated with a structural calcaneal varus condition. Sometimes subtalar joint arthritis,but a lot of these are structural heel varus issues, and you're going to have toconsider a Dwyer osteotomy with this. Again, depending on which particular tendon is damaged, determines then what you do. I'm going to go through all this in more detail with the tendons because I use a modification of the Redford -Myerson classification with a cable system.

Dr. Spector: What other anatomic zone should surgeons be focusing on?

Dr. Visser: The third is really the cuboid tunnel. And the only tendon there, obviously that's involved would be the peroneus longus. We know the brevis then begins to maneuver up towards the fifth metatarsal base at that level. Oftentimes in this area, we have an accessory bone, which is called the os peroneum. Remember, all accessory bones are in the actual tendon itself. And just as a little tip, with avulsion fractures of the fibula, for example, and if you have one of those and you have a very unstable situation and you're considering to doing a Brostrum repair, remember that chip is in the talofibular ligament. So you can't just go in and excise it. If you excise it, you obviously damage the ATFL ligament. So, you're going to have to do an excision with a Brostrum repair, just in that situation.

Dr. Spector: So now that you've talked about the pulley systems, where do we go next?

Dr. Visser: I'm going to kind of go ahead and talk about what I call a cable system. So we have one cable, we have a two-cable system, which would include both the peroneus brevis and the peroneus longus. So in the two-cable system, we have a situation where maybe one tendon is damaged, okay, commonly in the area of the brevis or in the B area, and we have to go in and repair it, but we can repair it. And it can become very functional. We use a system where we try to preserve at least 50 % of the tendon, although tendons are very, very effective in regenerating themselves. And I personally will cut them down to 30% and have no qualms whatsoever. The literature will talk about 50, but I don't think you have to leave that much in that situation.

Dr. Spector: What if both tendons are damaged, both the brevis and the longus?

Dr. Visser: So let's say you do have a damage of the longus in the A area. You still can go and repair them. They usually have a split there or basically where you have fraying of the tendon. You do a debridement and you do a tubularization process which restores the function of the tendon. So this continues to be a two-cable system with easy repair.

Again, go ahead and look, make sure what it is that caused this. Oftentimes it can be from an isolated injury. It was an inversion injury or a chronic injury that got missed and there was nothing mechanical that led to it. But you have to also remember that if it's been around a long time, be careful about the collateral ligaments because they can't have functional instability, not necessarily anatomic instability. Functional instability was described by Freeman basically where the proprioceptors were damaged from the injury and then so basically the foot and ankle loses its function in time and space and can have unstable symptoms, even though you do stress views and they're all basically normal in that situation. So that's pretty much the two cable that goes all through down the A, B. Obviously, the C would be a one-cable, so it wouldn't be in that particular discussion.

Dr. Spector: Can you tell us a little more about one-cable scenarios?

Dr. Visser: This is a situation where you cannot repair one of the tendons, okay? Let's take the A area and let's say the brevis tendon is really damaged or it's ruptured. We know that a lot of these tendon issues from injury or tendinosis, tendinosis is not an inflammatory condition. It's basically a situation where type one collagen gets replaced by type 2, and it's basically a lot of ground substance to the tendon. It loses its elasticity and function there, so when it's stressed, it's much easier to tear that tendon than a functional tendon that has nice fiber elasticity that occurs in that situation. So again, oftentimes there's tendinosis and the tendon does tear or has a partial tear rupture that when you go into repair it, there's not much you can do with it. It's badly damaged. If it is the brevis,then what we do is say, hey, you know what, we got that longus tendon. And what I discussed about at the beginning of the lecture is where the longest is the stronger of the two, we can feel pretty good about going ahead and transferring the brevis tendon into the longest. Again, at the A level, that transfer would be done high up into the area in the posterior fibula. If it was in the B area, in those areas, again, you'll have to debulk the tendon to some extent, and you can transfer it under the pulley. Now, the thing is, if you're in the B area and you're going to consider surgery in that area, as I told you, the tubercle is usually enlarged and that will have to be debulked, not resected.

A lot of people go in and resect it and then you lose the poly effect. You need to debulk it. If there is a fixed varus state, you have to address the varus state, usually with the lateralization osteotomy where the tuber is shifted from a medial position to a lateral position, okay, in those situations. Usually, if in the area where you do the longus transfer, I don't normally have to do anything more mechanical at that level, like an adjunct Brostrum or even something to the calcaneus where it might be relatively vertical, but I'm going to maybe put it in a slight valgus position to help the fact that the tendons are weakened. I don't normally do that in that situation. If however, I have a situation in the opposite situation where the longest is damaged in this area for some reason and I have a the brevis tendon. The brevis is not as strong, and I can't expect one tendon on that side to stabilize the foot and ankle, and especially on a larger person.

And in that case, I'm going to kind of consider some of the adjunctive things like a Brostum, for example, or a slight lateralization osteotomy to help assist the weaker construct that I'm up against. Certainly you can consider in these instances allografts if you choose to do so, and then basically you will take then just a one-cable situation that you have now and reestablish it back to a two-cable situation. Okay, and then obviously the B area is in the same situation.

Dr. Spector: Well, there's obviously a lot of detail on this topic, including the zero cable situation. So let's get into that scenario in our next episode with Dr. Visser. You can find this and other episodes of Podiatry Today Podcasts on SoundCloud.com, Spotify, Apple Podcasts, and your favorite podcast platforms. I'm Dr. Jennifer Spector, the Assistant Editorial Director for Podiatry Today, and we hope you'll join us for this and even more episodes.