Section: CME Category: Biomechanics

Equinus - The Sleeping Giant

Jeffrey Cusack, DPM

Jeffrey Cusack, DPM discusses soft tissue versus osseous equinus deformity, specific radiographic signs associated with each, as well as proposing a new theory regarding mechanism and location of compensation for an osseous equinus.

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Goals and Objectives
  1. Distinguish soft tissue versus osseous equinus deformities
  2. Review specific radiographic signs associated with each
  3. Propose a new theory regarding mechanism and location of compensation for an osseous equinus
  4. List useful treatment options available
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  • Lecture Transcript
  • TAPE STARTS – [00:00]


    Dr. Rogers:: All right. We're going to bring up Dr. Cusack. Jeff Cusack is an assistant professor in the Department of Orthopedics and Pediatrics at NYCPM, and he's going to talk about Equinus - The Sleeping Giant.

    Dr. Jeff Cusack: Good morning, and thank you to Dr. Schoenhaus and those in the presence here for inviting me here this morning. One of the things that in listening to the presentations, especially in the context of the Charcot foot, which we've heard an awful lot about from various angles this morning, one of the things that we're going to discuss for you is perhaps something that might help us avoid getting to where we are this morning.

    And in looking at what the objectives are going to be, we're going to look at differentiation between soft tissue and osseous equinus, and I'll jog you up a little bit when we talk about osseous equinus, in the context of Charcot arthropathy as far as location within the foot, look at some radiographic signs that will help you determine early signs, early recognition of these problems. Maybe talk about sort of a new approach at how and why osseous equinus compensates, where it does. It is a little bit different than soft tissue equinus, and of course leave you with something that you can bring back to your office, and hopefully help some of these folks before we get to where we've seen over the course of yesterday and today.

    By way of background, you've seen just a representative photograph, I just Googled an angry patient, and this is a nice representation.

    [02:00]

    Apart from our wound care patients, the patients with sensorium on happy patients for whatever reason, the orthotics aren't working. The surgery that was performed isn't functioning well. Of course in the context of this weekend's presentations, the end manifestation of what is often an equinus derived deformity, Dr. Kalish mentioned that just a few moments ago that it is a strong deforming force in the foot. If there was ever an outcome killer, yeah equinus.

    A strong mentor of many of those that you know my background, I spent an awful lot of years with Dr. Langer, Wernick, and Schuster, and Shelly was always have to say that, yeah, there are deforming influences within the foot. We know them all but of all of them, equinus is probably the most destructive on the foot. And maybe this morning, we can show you why it is and maybe you'll have a bit more respect for it, and hopefully diagnose it when it's there and use that information to offset.

    Again, I don't want us to get to where we were with some of these feet that I've seen this morning. Another strong mentoring influence of mine and on many of you in the audience, lucky enough to have had Dr. Wernick either as a professor, or certainly listen to him, whether through his laboratory or in his lectures.

    Rather than take the classic definition of equinus-fixed position of plantar flexion, Joe always say, "Let's look at it a little bit differently and take a more functional approach, and that is that equinus really is an inhibition of forward movement of the body across the foot." And make no mistake, folks, anything that gets in the way of that bodies moving forward, is going to present us with some significant compensatory issues.

    [04:00]

    And of course, by definition, equinus, we always assume that we are examining our static patient, the range of motion when the subtalar joint is congruent or as we say, neutral, and the knee is fully extended.

    You need to maybe look at your patients differently and it's always interesting that most of our offices are set up shotgun or railroad style, so that even if we have an internal hallway, we have an excellent frontal plane view of our patients. Unfortunately, the good stuff, as Howard Dananberg likes to say, the good stuff occurs primarily on the sagittal plane and it's difficult sometimes to fully evaluate what's going on.

    However, dorsiflexion is critical and the understanding of human gait that we teach the kids at the college is that the efficient way the human creature moves is by the application and release of elastic stresses to two key opponents of the body, one being the ankle, the stretching and release of energy stored within the ankle complex through the Achilles complex. And whether it's due to age or a contracture of that unit, the restriction of forward movement, and therefore the inability to release any potentially stored energy, provides for some very interesting issues when you watch these folks function.

    Jacqueline Perry described eloquently the so-called rocking mechanisms within the foot, the ankle being a critical one, which again enables the body to pass across the foot. And the block of that is going to result in some severe compensatory problems, which is one of the reasons why we're going to see equinus being so destructive in influence on the foot.

    [05:56]

    So one thing I never learned is I never asked for show of hands in an audience, but we all know that when you look at equinus, and as I tell the kids, as Dr. Langer used to beat into my brain, and before him Schuster, a little more kindly though with Dick than Shelly was, but equinus, no matter where it manifests, whether it's within the foot or without the foot, from without, it is a sagittal plane influence.

    And therefore, the solution to a sagittal plane problem has to come on the sagittal plane. We heard an awful lot this morning about a surgical solution of a restriction of dorsiflexion, which is to lengthen the Achilles and provide that mobility, all right? But again, if we were to preoperatively look to compensate or neutralize that restriction of movement, there are loads of joints to potentially find that lost motion at.

    And the thing to keep in mind when we look at our patients is, don't be podiatrically as Wernick used to say, podiatrically myoptic and focus on the foot. Recognize, as Schuster was big on, any joint whose axis is roughly parallel to that of the ankle, potentially could solve your problem for you as I'll show you in a second.

    So again, we have basically two types of a restriction of dorsiflexion, the first being soft tissue, whether it's gastroc or soleus, and the so-called osseous or bony block, all right? Differentiated by our Silfverskiold test and the inability to achieve mobility when you release the gastrocnemius either as a soleus and/or a bony block. [Marook] [07:51] in the day talked about the compensated equinus and knows that – knew Langer knew he was a stickler for syntax, and he was a genius at editing and such, master of the English language, and he was very particular and very precise.

    [08:07]

    And the end stage is the compensated equinus, which is what we're seeing plenty of over this weekend. And in our little world, the idea is to evaluate these patients and maybe, just maybe do something to interrupt this progression in these neuropathic patients that we've seen, and maybe do something a bit helpful before we get to that end result.

    The beauty of the foot, and it never seizes to amaze me, is that because of the way it was designed and the alignment of the joints, and so on, it is an engineered product. It is predictable in many ways as to how a foot who is under attacked or under duress, will react to that duress. And using that information can be quite interesting too so we can actually predict sometimes very, very nicely what will occur, and therefore take the steps to neutralize it.

    Gastroc equinus just so you know, and maybe you'll take a look, the Chinese med – this was Langer, for sure. The thing with especially the gastrocnemius equinus, there are loads of ways to hide it, and this is why equinus is undervalued, or certainly not appreciated as I have put here. It's often missed, and the reason being that if the body chose to neutralize an equinus deformity using only one compensatory action, you're seeing one evidence here this morning, the Charcot breach. Look at the devastation that would occur and these are neuropathic patients if we took a fully sensed patient and broke their foot in half, they'd have a thing or two to say about it.

    [09:56]

    So we're looking at a progression over time. And over time, what individuals will do is as Dr. Langer used to say, they'll take one from column A, one from column B. They'll use various mechanisms and therefore a little of this as he used to say and a little of that oftentimes, unless you are really, really keyed into look for it, it could very well be missed. So again, this multisegmental way to hide the compensatory approach. I promise only one boring slide but it's important, and again just to reinforce what we all know, and that is that.

    The reason when we look for compensatory sides within the foot, when I have the students and we discussed all these things, and we talk about could a restriction of ankle dorsiflexion be compensated at the subtalar joint? And I always tell them, if you're interviewing for residency, listen to the question, because if the question is could it be compensated to the subtalar joint, you're to answer, yes. But as we all know because of the relationship of the axis, you're not going to see an awful lot of the dorsiflexion component by pronating the subtalar joint. You need to find something else.

    And as I said within the foot, move a little farther out and you move to the midtarsal joint. And because of its relationship to the ankle, keeping in mind by the way that for most of us, I see a lot of folks that are contemporaries of mine, the biaxial theory of the midtarsal joint is all but dead, buried, and put into the ground by some of the work that began in '01 with Nester. It is a monaxial joint but it still favors an awful lot of sagittal and transverse plane alignment.

    So through the midfoot, if you will, midtarsal joint, there are tremendous potentials for offsetting this lack of mobility at the ankle joint. However, what price glory, nothing comes cheaply when you talk about biomechanical compensation through the foot.

    [12:04]

    And keeping in mind that you look at the context of the patient, normal, many, the majority of patients in gait, it is a heel-toe event. So the search, if you will, for replacement movement, the search for mobility that is not at the ankle, is going to move from a proximal to distal direction, which is why I'm so glad that minimalist forefoot strike running is pretty much also dead and buried in the ground, because in those patients as you know, they change the rules of the game and became forefoot strikers, which completely changed the way the foot was engineered to function.

    So the search begins proximal, and as I said, through the subtalar joint. And I tried to subtly enlarge the font moving from subtalar to midtarsal, to midfoot, and I'll show why I did that in a second. And so as you move distal, the potential for compensation for equinus becomes greater and greater. Still talking about a gastrocnemius equinus on radiograph, the classic findings, I don't know if it was the first speaker this morning, but talked about the fact that when the Achilles pulls straight up, you simply decrease the inclination angle of the calcaneus, which of course affects the cyma arrangement, the cyma line breaches, and so on.

    The classic findings of a gastrocnemius are what we are all familiar with. The entire rear foot essentially collapses on the forefoot. Mechanical compensations or, if you will, postural or functional accommodations, are also quite useful and employed certainly not to the extent that I'm showing you.

    [14:01]

    However, as I tell the kids at the school, the easiest is to change the alteration of the foot to the line of progression, and we call it Chaplin, they'll Chaplin the gait, the old Charlie Chaplin gait. If you externally rotate far enough, you change the pitch or the relationship of the ankle. And if you can get your hips out far enough, you don't need your ankle at all. You can just simply hobble around left and right, back and forth, left and right.

    Again, this young fellow here exaggerating the vertical takeoff, the prematurity of the heel lift and those instances of course, the heel can make it to the ground. It just cannot stay down long enough until contralateral swing, keeping in mind in all of these patients that these alterations in gait patterns do not come without a price. For instance, even a mildly abducted gait increases the reaction force of the ground against the entire medial column, and can contribute to, and feed into a functional hallux limitus. So one begets the other.

    With our patients, this is often the first time that we are aware in equinus influence has actually been hidden from us very well. We have a patient that presents with a diagnosis of a fasciitis and we do see some arch alteration. We recommend, prescribe, and construct a controlling foot orthosis for the patient. Unfortunately, if said orthosis is not modified with something to neutralize that equinus, what we've now done is eliminated the areas of the foot that have been used to that point to compensate for the equinus. And any number of things can happen as a result of this, so for those of you that do orthotic therapy in your practice, and patients all of a sudden, you dispense the orthosis and they often complain, this is a common one to them. It feels like they're standing on a golf ball.

    [16:07]

    If the module is stiff enough and [indecipherable] [16:12] was notorious for this where you would develop transverse fractures, which interestingly enough, were exactly parallel to and beneath the midtarsal joint. You may have to look closely because this was an early capture. But one of the earliest signs that a patient has an equinus condition, and this was something again that Langer had noted and just looking at thousands of orthotics that the laboratory, that if you start to see the medial aspect of the top cover being pulled away, and I promise at some point next time if I ever give this again, I'll get a better photograph. But you'll all – if you've seen this, you'll know what I'm speaking about. The top cover begins to be dragged away in the tail of navicular areas, being pulled away in a circular area laterally, and keeping in mind, the alignment of the midtarsal joint relative to the sagittal and transverse plane, roughly 50% of mobility and both directions, the foot is escaping, or at least is trying to escape from that orthotic device, by abducting off the shell, and of course dragging the top cover with it.

    So an early sign that in fact an equinus is present may well be that the top cover, and the patient, you'll see here that the patient will just complain, "I just paid several hundred dollars for this and look at this cover. It's peeling off already." Well, take a look and see where it's peeling off. A treatment we know – one thing that's always interesting to me, Schuster always used to say to his patients, "Show me how you stretch your calves. That's all I want to hear about first." And inevitably, you'd see this. They'd shown him how he's stretching, and notice the left foot completely externally rotated, abducted, and useless as far as a gastrocnemius stretch. They're avoiding the ankle entirely.

    [18:03]

    Other points might well be with runners especially have them stretch wearing their orthosis if they are wearing an orthotic device, so you're not inadvertently breaking the midtarsal down. We do want to apply the stretch to the ankle and not the midtarsal joint. Of course if indicated surgery, we've heard an awful lot about it.

    What I would like to talk to you about this morning, however, is this osseous breech. And one of the newsletters that [Daca 00:18] had written, he used to call this, the subtle destroyer. And another quote is often forgotten, "seldom looked for and generally missed influence".

    Equinus, again, and we're talking now an anatomic blockade, and he had a couple of theories why it often early on was neglected, and it was going back to again some of the contemporaries of mind when we had plain film, and you'd snap it up into the view box. And depending on how deep the restriction bar was and how hard you snap it up, and how you position the foot, oftentimes you'd cover up the entire ankle and not even see it. If you're concentrating on heel pain looking for an inferior enthesophyte, you would even bother looking a little bit more proximally to evaluate the ankle.

    More importantly was that early on when Marook wrote the bible, and again, a lot of it has been challenged over the years. However, in the day, and it still is somewhat out there, that osseous equinus is not as prevalent as one would think. And Marook felt it was probably no more than at best, 10% or 11% of the population. When in fact when you start looking at the numbers, it's probably 50% of all equinus patients, may well be osseous.

    [19:59]

    And that brings us a little bit forward because contemporarily, there are two folks. Langer of course has passed away but Dr. LaPorta at the first Schuster seminar, talked about how as a resident, and he had an interesting comment that he felt when he was a surgical resident that he singlehandedly wiped up the equinus within a 20-mile radius of the hospital. He was doing his residency out on California because everyone got TALs. And the interesting thing he said is that on many patients when he brought them back postoperatively and everything was healed, and he checked the range of motion, that no matter how hard he dorsiflex that foot, it still would not budge beyond 90 degrees.

    Dr. LaPorta said it wasn't until sometime later when he was pulled aside by a couple of orthopedic friends that said, "Hey, think about the alignment of the ankle as another source of restriction of ankle dorsiflexion, the osseous equinus and abnormal osseous factor in the bones."

    Langer and LaPorta were seeing the same thing and it's interesting that it's a shame the two of them never really got together and talked about this, the end result being the same. They were anatomically looking at two areas. Langer was infatuated with the dorsal talar anatomy and the fact that many patients were born without much of a notch, which allows of course the tibia to rotate forward into and fall into during midstance.

    [Wittow] [21:30] was looking at the arch of the tibia and the dorsal surface of the talar, talus, and the fact that in many patients, these arches don't match, leading to this convergence anteriorly, the end result being the same, a blockade of movement. With osseous, of course we do our Silfverskiold. We release the gastroc and we see no improvement, leaving us with either a soleus contracture or an osseous block. What you'll find is if you go to the, as Warner Wolf used to say, "Go to the videotape," well, here we go to the x-ray.

    [22:04]

    Specifically, you go to your laterals and you'll see a couple of things that may help you. Again, a soft tissue equinus is predominantly as I have just phrased it here, I didn't know how else to call it, it's midtarsal-centric. Therefore, the signs are consistent. You will see a lowered inclination angle and a cyma line disruption.

    Osseous block consistently, which you often will see, is that the inclination angle, and the cyma line, are often either completely within normal limits or modestly at best compromised. But what you will see time and again is the naviculocuneiform begins to open up and breech. When you look at these films on the left of your soft tissue, the classic findings, but when you see, and these are all early, early, early signs of an osseous block.

    If you look distally at the naviculocuneiform joint, you will start to see varying degrees of an opening that appears, and I'll tell you in a second why that is. Osseous block can use knee flexion as you would with gastroc. Of course not. You release the knee, it makes no difference. They will use genu recurvatum, and in some of the patients, it's interesting, Schuster always say, "Take a look. If you see someone that's back kneeing, take your goniometer and measure the ankle. Oftentimes, the recurvatum will match the plantar flex attitude of the foot."

    It's an awful way to compensate. They present as you would expect with tremendous posterior knee pain, but knee flexion know. An observation only by Langer that osseous blocking patients have a completely apropulsive gait. They pick the entire foot up, pick it up, put it down type of gait, which by the way when you look at their plantar surface of their feet, they show very little in the way of hyperkeratosis because the foot is so apropulsive, okay?

    [24:02]

    Why is it that with an osseous block that you often do see a distal manifestation? And again, we're going to look early on so that hopefully we don't get to where we've arrived, keeping mind when you look at some of the Charcot breeches, that often is in the navicular, the midfoot region of the patient's foot.

    You watch someone walk, and as I said, we're talking heel-toe gait. Heel-toe, heel-toe, the progression is proximal to distal. The search for dorsiflexion, if it is not available at the ankle, is going to move from a proximal to distal direction. If a block is from behind the ankle, the soft tissue influence, the goal will be satisfied, or the compensation can be easily satisfied by subtalar, followed by primarily midtarsal joint compensation.

    Langer's theory, and it's interesting, and he passed away before he could ever put this out, however, something for you to ponder. And that is that if the block is anterior, whether it is the dorsal neck architecture or the convergence of Dr. LaPorta, the blockade anterior to the ankle closes the window of opportunity for the most part through the midtarsal joint, midtarsal joint. Not saying it closes it entirely, but for the most part, you've lost that very opportunity to find that mobility to any great extent through the midtarsal joint.

    Again, the search is proximal to distal. What's next? What's next is all of these joints in the midfoot, and there's a wonderful paper that was published by this [indecipherable] [25:52] and [Sherriff 00:25], it's funny this year's Schuster seminar, [indecipherable] [25:57] that were there, Dr. LaPorta gave a very interesting theory on first ray hypermobility, and used this paper.

    [26:05]

    I was lecturing on plantar plate rupture and using this paper for different reasons. It's a cadaveric study. It's eloquent and they were using an implantation technique to measure relative movement of all the intertarsal bones of the foot. What they found in the context of this lecture is that the naviculocuneiform joint offered a tremendous, only second to the tail on navicular joint, potential range of mobility on the sagittal plane. A dorsiflexion stress moment can be satisfied very, very nicely through the naviculocuneiform joint.

    Here we are with an individual who is seeking tremendous amounts of dorsiflexion and lost the midtarsal joint. Naviculocuneiform becomes a very, very likely suspect joint. Radiographically again, the classic flattening of the talar dome, but anatomically, is there an adequate notch in the talar dome? Is there a convergence, the NC fault?

    Dr. LaPorta loves the angles, and one of his most favorites, or favorite rather, is the ADTA, the anterior distal tibial angle, indicating what he calls this tibial procurvatum. And it's a nice indication of whether or not there is that lack of an adequate match of the arch between the talus and the tibia. High ADTA, 83 is nice. As you approach 90, it indicates an actual bony block.

    What we need to do is, and these are the context again of some of these poor souls that we've seen exemplified particular this morning, I've sat in the back and just shake my head at some of these poor souls with these fully exploded feet.

    [27:58]

    Early recognition, what we're going to be able to do is ponder our options and this is important because in the context of this morning with a lot of the surgical procedures, we're talking about doing TALs for an equinus influence. However, what if the equinus is not of a soft tissue variety? What if it is bony? How much good is the TAL going to do? Number one is early recognition, right?

    Next thing is think about the fact that these feet, they just are resistant to, and attempt that dorsiflexion at the ankle. Okay. What's the problem leaving them somewhat plantar flexed? Dick Schuster, and maybe that new Dick was as much into evaluation trends of the foot and lower extremity as he was into his mechanics, and clearly the foot is headed toward a more plantar flexed attitude from an evolutionary point of view.

    Dick always had an interesting way of looking at things and those of you that had the experience of working with him or knew him, very simple approach to treating patients, but this piece of advice, this is a take home right here, especially if you're working with a recalcitrant orthosis patient. Clearly when in doubt, raise the heels. The functional approach therefore is allow them to function in a plantar flexed attitude. We do not want them to attempt dorsiflexion.

    How are we going to do it? Easily enough, you're going to need to elevate the heels, and I always get to ask the question, "How much?" The answer is, as much as it takes. Whether you can accomplish it within the shoe within orthosis, and by the way the orthosis, the module needs to be somewhat more forgiving, because it is primarily a vehicle against which the heel lift will be added. It may take these folks a bit more time to get accustomed to these and the heel needs to be quite elevated, a 12 to 16-degree rather, pardon me, heel drop mandatory.

    [30:01]

    One more thing with shoes, you can recreate the second and third rockers of Perry very nicely with the appropriate shoe modification and/or shoe choice. Any of these shoes with external rocking platforms, and before you beat me up in the face of neuropathic patient and say, "Well, I'm certainly not going to put them into an MBT or a Hoka type shoe, there are a number of flat-soled shoes with distal rockers that are modest only well-loafed or thin comfort. And by the way, brand new, I didn't have time to load it in, but this new Dr. Scholl therapeutic shoe if you've not seen it, double Velcro strap, comes in all widths, and has a very nice forefoot rocker only, are very nice adjuncts to anything you're going to design for your patients.

    In closing it down in my five seconds here, these equinus influences, take the time. They maybe subtle but they're there. Neutralization needs to be adequate and whether or not you're using the orthosis modification and/or shoe, or a combination of both, and you'll have an awful lot of success with your patients. And with that, I thank you very much.


    TAPE ENDS - [31:22]