Blister Prevention Pro

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Blisters From Orthoses: How To Fix

Rebecca Rushton: Thanks for joining us for Blister Prevention Office Hours this month. We’re going to be talking about what to do when you issue a pair of orthoses and your patient gets blisters. Because there’s nothing worse than solving one problem, only to cause another. Probably the five, most common that I wanted to talk about today are:

  • Under the arch
  • The back of the heel
  • Heel edge
  • Plantar first MPJ and even the edge of the medial forefoot
  • Under the big toe

1. Medioplantar arch blisters

So, under the arch is probably the most common one and I guess it’s kind of easy to understand because we’re taking a relatively non-weight bearing area and giving it some weight bearing force. So all of a sudden it’s having to deal with some shear deformation which it’s just unaccustomed to. I’m sure you already let your patient know that that is generally a transient thing that your skin will get used to it. It can be because there’s a mismatch in the contouring of the arch. So the arch might be too high altogether or too high in a particular area. And it may even be insufficient support. When you get these blisters with orthoses, sometimes it’s not the best thing just to grind down the arch or heat gun the arch down, it’s actually to get better support.

So how do we fix it? We talk about the wearing in process and often that’s all it takes is just an understanding that the skin will become a bit more resilient as we subject it to that shear deformation. We can if we feel it’s necessary, we can heat gun and flatten the arch. We can also improve the windlass mechanism. So basically, what we want to have happen is we’re trying to… if we give an orthotic that impedes the windlass mechanism, that means there’s an arch flattening force. And then, we go, and put a big chunky orthotic under the arch, and so, we actually get an increase in pressure because of it. Rather than lowering the arch, we just need to facilitate the windlass mechanism. So the foot can intrinsically go through that arch lifting process or mechanism. So things like calf stretches, heel lifts, Cluffy wedge, reverse Morton’s extension, that kind of thing. All of these things will increase the windlass mechanism. And we can also just put an Engo patch in the arch, knowing that we’re reducing the friction level. So if we have a look at this chart.

This chart basically shows us all the ways that we can prevent blisters. If we look at each of those factors that we just discussed. So first of all, there’s the wearing-in process. What we’re doing here is we’re implementing this strategy. We’re essentially increasing the skin’s resilience to shear gradually by wearing the orthotic in gradually. The other one was heat gun/flatten the arch. What we are doing there is reducing pressure. That’s an easy one. Next one is improve the windlass function. What we’re doing here is we’re reducing the abnormal bone movement. And thereby reducing pressure.

That goes for calf stretches and heel lifts. So we’re just reducing the arch flattening forces. And the Engo patch, that reduces the coefficient of friction. You could also argue for, if it’s just a poly orthotic, you could put a Spenco cover on it. That would thereby absorb a bit of shear under the arch. So you could also do that. Spreading shear load is all about taping. So you can do that, especially in this wearing improcess, but hopefully your patient doesn’t have to do that day-in day-out forever. This is just a photo of the Engo patch two patch technique for edge blisters or medio-plantar arch blisters.

Often these blisters aren’t literally under the arch – it’s along the edge of the orthotic, so the two patch technique is the best way to go about that so that you can take the orthotic out and so the patch sticks for a good amount of time.

2. Posterior heel

The next one is the back of the heel. This is the next most common area that sustain blisters from orthoses being issued. I would think that you would agree. By putting an orthotic in the shoe, we are making the heel sit a little bit higher in the shoe. And that might mean that it’s abutting sort of a firmer or more protruding area of the plastic in the heel cup of the shoe… heel counter, sorry of the shoe. And also it might become apparent that your patient isn’t really lacing that efficiently so it’s not really holding the heel down.

So exactly what are we doing? Or how do we fix these things? We can grind out under the heel just so that the orthotic sits down lower in the shoe and the heel is more at a lower area. So there’s less irritation and less slippage. We can obviously improve the lacing technique. If that looks like it’s necessary. We can also narrow the heel cup. What I mean by that is often I use Interpods and sometimes I just need to bevel that in a bit more so it sits down and towards the back of the shoe, a bit better. So we can grind out underneath but we can also grind a bit more of a bevel on there, so the orthotic sits down into the heel cup a bit better. And we can use an Engo patch just to reduce the friction level. So, what do we have there? Lacing techniques and reducing the pressure by letting the heel sit down a little bit further in the shoe, that’s what we’re doing. We’re reducing the bone movement by keeping the heel down in the shoe and reducing pressure by keeping it in the appropriate part of the heel counter of the shoe. And the Engo patches are the way we reduce friction typing, you can do for the wearing in process. But obviously, we don’t really want our patients to be having to type every day, just because they wear orthotics. And we can absorb here with gel or Spenco stuck to the back of the shoe, but it just doesn’t really last. That one is a bit of a hassle, to be honest. So that’s not quite so applicable. This is a photo of an Engo patch at the back of the heel. Fabulous way, just about the only thing that I ever need to do if someone’s getting blisters at the back of the heel.

3. Heel edge blister

This one is a patient of mine who wears crocs and he refuses to put the strap around the back of the heel. And so, he’s always sort of walking a bit on the edge of the heel cup of his crocs. So nothing to do with orthotics, but just I’m curious as to how any of you guys have actually seen heel edge blisters? In terms of an athletic situation, this is what they can look like. And you can be tricked into thinking that this blister is… blister is caused by a problem higher up on the heel. But in fact, it’s to do with the rim of the heel cup of the orthotic or insole and it just pushes the blister fluid away from that area. So, the path of least resistance is generally upwards, Why do we get them? We can get them because the orthotic is sitting forward in the shoe. I’m sure you’ve seen this before. Once the orthotic settles into the insole, it will just always sort of go there. And if it’s in the wrong spot, it can be very difficult to get it back and to make it sit back.

So, we just can’t afford for these heel edge blisters to have the orthotic sitting forward at all. It can also be an issue when the heel cup is quite narrow, but they’re wearing a shoe where the back of the heel circumference is quite wide. So there’s a bit of a mismatch there. And so the orthotic is sitting to one side and we are essentially walking on the edge of the heel cup. The heel cup can be thick and you can even just have a folded or worn insole. I’ve had that happen to me on a big long walk that I wasn’t anticipating doing and I looked down and there was a fold in the insole because I changed one insole from one shoe to another.

Here’s a picture of the orthotic sitting forward. And really the only way to fix these blisters from orthoses is to use some double-sided tape under the rearfoot post of the orthotic. I guess you could give them a new insole, like a Spenco insole or something underneath if there really is a decent divot and you just kind of avoid the orthotic slipping forward, you could do that, I guess. Narrow the heel cup of the heel of your thought is just too narrow for the foot, then you need to make it wider. You can heat gun it, you can grind out from the inside with a dremel or our nail drill. Sometimes if it’s just because of an imperfection in the cup of the insole, I’ll just say get a flat Spenco insole that can definitely solve the issue. And you can use an Engo patch to reduce the friction levels.

So, what are we actually doing with all of those things? So, double-sided tape under the rear foot post, we’re reducing pressure. Yep, we’re trying to get rid of that focal pressure, that really should not be there. It’s just caused by a malposition of the orthotic. Narrow the heel cup – we’re reducing pressure. Flat Spenco insole – we are reducing pressure as well. And then the Engo patches reduce coefficient of friction.

This one’s not so much about bone movement. Sometimes I do that but only if we’ve got all the other things in place at the same time and I’m talking sort of ultramarathon – a bit of taping can add that little bit more that can just make a bit of difference. And this one is not applicable. It just doesn’t last. There’s a photo of the Engo 2 patch technique for a lateral heel edge blister.

You need the two patch technique for two reasons. Number one, so you can take the insole or the orthotic out. And number two, if the insole or the orthotic is quite cushioned, and you’ve used the one patch to cover both the vertical and the horizontal surface, every time you step on it, it’s going to drag the patch that’s on the vertical surface down. So you step on, the cushioning flattens and the patch will come unstuck.

4. Plantar first metatarsal head/MPJ

Next one – the plantar first MPJ. This one’s not quite so common, but an orthotic could potentially cause this. Either the orthotic is too long in that area, or the orthotic is slipped forward again and it’s sitting too far forward in the shoe. So, double-sided tape under the heel of the orthotic. Obviously, grind back the disto-medial edge, so it’s not impinging on the first MPJ and you can use an Engo patch. So these are really all about reducing pressure by modifying orthotic and the coefficient of friction with the Engo patch.

And just quickly. I know this one we were talking about directly underneath the first MPJ. But edge blisters are very common, if you’ve got bunions and Adult Acquired Flat Foot Deformity. I had a lady in not long ago who has Adult Acquired Flat Foot Deformity that’s not really being supported by orthotics well, although we changed that. But the orthotics in themselves weren’t doing enough. And so she was getting calluses and blisters particularly on the edge of the first MPJ but also the edge of the hallux. And we just put the Engo patches in – because she’s from Perth, which is miles away. She just holidays down here every now and then. We put the Engo patches in and I saw her a year later because she holidays down here every summer, and she said that that one simple change was life-changing to her. The blisters under her calluses were just so painful. And although she had an orthotic in it, just wasn’t doing enough to reduce the shear at this medial edge of the first MPJ. So reducing friction can make a massive difference for these. And you’ll definitely need the two patch technique for this, because it’s not just underneath, it’s also bit to the side.

5. Plantar hallux

Under the big toe. This is essentially an inefficient windlass mechanism. So either, the reason they’re getting orthotics is because of an inefficient windlass mechanism and you haven’t managed that effectively enough with the orthotic. And so what happens is the first metatarsal a dorsiflexes. So the first met head’s, not bearing enough pressure. It’s all borne by the big toe.

This is kind of what it looks like on force plates. So this pressure is not nearly as much as it should be. And all the pressure is borne by the plantar hallux under the IPJ. So the aim here is to improve the windlass mechanism through whatever means that is going to mean for your patient. It could be calf stretches, heel lifts, heel height differential on the shoe, rearfoot post, medial heel skives, increase the proximal arch height. So you don’t want the arch to be high distally because that is essentially just flattening the arch out, not letting the windlass mechanism happen as effectively. The forefoot wedge 2-5, Cluffy wedge. All of these are essentially changing bone movement and reducing pressure. And then the Engo patches reduce the coefficient of friction. Taping – not so good for this. Absorbing shear – You could put a Spenco insole on there. You could get them wearing a gel toe sleeve. I find that when there’s a really significant lack of windlass function, or functional or structural hallux limitus, the gel just wears through too quickly because the forces are just too big. So gels will help some people but will wear through prematurely.


So, wrapping all that up in regards to how or what to do if your orthoses are causing blisters. No matter where the blister, no matter what the reason, all of the prevention strategies basically fall into this chart. So let me just recap that. So we can reduce the number of shear repetitions. That means not walking as far – not really helpful to anyone. Although, in the initial wearing in process, that can obviously help. It kind of helps with this one. It increases the resilience of the skin to shear load by increasing gradually the amount that we are wearing them.

But most prevention strategies aim to reduce the magnitude of shear deformation. And they do that by either reducing the abnormal bone movement. Because remember, there’s always relatively high friction levels, in the shoe between the skin, the sock and the shoe surface or the orthotic surface. That’s because that’s the way materials are made. That’s because our foot needs a bit of traction in the shoe for the efficiencies of gait. And because our feet sweat. So, there’s always relatively high-ish friction levels. So with that known, not fixed, but it’s kind of just a given, it’s the baseline, that keeps everything stuck together. But the bones are still moving in the foot. And so that mismatch is skin shear or soft tissue shear. And by reducing the relative bone movement, we can reduce the shear load deformation magnitudes. Spreading shear is all about applying adhesive products to spread that shear load over a larger area. Just like cushioning reduces the vertical force per unit area, thereby reducing the peak pressure, we can think of reducing shear load by spreading it over a larger area in a similar way. We can use materials that absorbs shear, like Spenco and gel toe protectors. And we can reduce friction force by either reducing pressure or reducing the coefficient of friction. That just means using pairs of materials that make it more slippery. So, like lubricants, for example, that takes the skin-sock interface friction level, which is relatively high, and reduces it because of the lubricant. So it’s basically lubricant on the skin, and then the sock and that’s kind of slippery. Same with Engo patches, but at the sock-shoe interface, or the sock-orthotic interface.

Q & A

So, that’s Orthotics. Let’s move on to the Q&A because we had a couple of really good questions.

Does moisture cause blisters?

Aileen asks: Does moisture cause blisters? I like the simplicity of this question. Because it’s a common one that kind of trips people up. So, yes. high moisture levels are relevant to blister formation. And it’s a given in the shoe. So let’s think of it. Perspiration is the constant moisture factor. There are other reasons for moisture – running through the rain, puddles, water tipped over your head and running down your legs into your shoes, all that kind of stuff. But the intrinsic source of moisture is perspiration, that’s always there. Some people are sweatier than others, but there’s always a bit of moisture. That makes our skin clammy. Clammy is just another way of saying it’s sticky.

Yeah. Imagine having clammy sweaty hands – they kind of stick together. Sticky is another way of saying there’s a higher coefficient of friction at that interface, so it’s stickier, it stays in stationary contact for longer. It takes a larger force to actually break free of that static friction. And high coefficient of friction means high friction force. Because coefficient of friction, combined with pressure, determines the friction force.

So high friction force keeps the skin sock and shoe surfaces in stationary contact for longer while the underlying bones move back and forth with each step increasing the magnitude of shear deformation. It’s normal for our skin, our sock and our shoe to be in stationary contact with one another. It’s normal for the bones to move back and forth within our foot. That’s all part of normal function. And it’s normal that mismatch is being taken up by the soft tissues of the foot. This only becomes a problem when it becomes a problem, which is when we get blisters or some other shear-related problem, like ulcers or calluses.
But the thing to understand here is, reducing or eliminating moisture is not a necessity in preventing blisters. So, you don’t have to concentrate on moisture management. You can ignore moisture management. You can have the sweatiest person in the hottest, humid climates, exercising to large degrees, really sweaty feet, nothing you can do about that. But you can still be blister free because moisture isn’t essential to blister formation. Excessive moisture causes maceration. But maceration isn’t blisters. Maceration is weakened skin and when there is shear deformation which inevitably there is when we walk, that can become so weakened that we just get these skin tears. So it’s similar but it’s not really blisters.

So, excessive moisture will cause maceration, but that’s a bit different to blisters. Blisters are a mechanical fatigue within the stratum spinosum of the epidermis caused by repetitive shear deformation. Maceration is more when moisture levels are too high. So, when we think about, can we leave moisture alone? Every moisture management strategy is a coefficient of friction reduction strategy. When we’re trying to reduce the moisture within the shoe, we are trying to make things more slippery. Now, I want you to think about is… because we know that very dry skin has a low friction level or a low coefficient of friction. But is there ever really a point where we have low friction levels and bone dry skin in the shoe, especially when we’re exercising? I don’t really think there is. And so people think there’s nothing I can do. Moisture is to do with blisters, I can’t stop the moisture, Therefore, I’m always going to get blisters. There are better ways to manage friction, coefficient of friction, like Engo patches, lubricants.

Engo patches definitely have advantages over lubricants but they’re both good coefficient of friction management strategies. But then look at all this. You’ve got all this that you can move on to. Think about how the bone moves. Spread some shear load. Use some materials that absorb shear, reduce pressure. So, you can keep friction levels high due to sweating but reduce them in other ways like Engo patches. And then you can also work on these other mechanisms. So yes, blisters are in a way caused by moisture, or at least moisture is relevant to the blister story. But it is not necessary to the blister prevention story. I hope that makes sense. Thanks to John Vonhof for those images. I’m sure that you’ll appreciate them.

Epidermolysis bullosa blisters

And our final question Tania asks for advice on epidermolysis bullosa – I realise the mechanism is genetic but any tips on managing? EB is a terrible thing. It’s an issue of low shear deformation tolerance. So, I guess if you think about blister susceptibility on a continuum, you’ve got sort of blister prone people down this end and blister resistant people up this end. Yes, we can train the skin and cause it to adapt, structurally, to sort of shift us a bit up towards the more resistant end of the scale. But if you’re blister prone, that doesn’t tend to really get you right up to the end. You’ll get a little bit of a shift. But EB is further on back here. So if you think for a blister-prone, people and blister resistant people the continuum is here to here really, if we put EB into the equation although there’s a genetic reason for it, that continuum is their right down on the end of the continuum. And even within EB there are different levels of low shear deformation, tolerance and strength.

But at the end of the day, it is to do with shear deformation tolerance, and all the same things apply. EB treatment or prevention generally revolves around absorbing shear and reducing pressure. So it’s all about wearing sort of wool-lined shoes, really soft materials. So we’re talking about reducing pressure. Lots of bandaging. So extra layers, so that reduces pressure. Things that reduce pressure or cushion, they tend to also undergo a bit of share in themselves as well. So we’re really doing these two things when or these are the stock standard EB recommended treatments.

However, I feel that EB could really broaden their horizons and look at these other things. Fair enough spreading shear load with taping might not work so much because you’ve got to get that tape off and that can cause skin damage in itself. Although, it’s going to depend on what level of EB you have. I know some people that get by with taping.

This is something we could be looking at. Bone movement drives shear deformation in the presence of high friction levels, which are to a degree, a given. So, I would be always, I mean every blister I see no matter whether you have EB or not, I’m always thinking about how that bone is moving and how it can reduce that abnormal bone movement. And we can also use these things. Lubricants – probably, I mean you’d need really frequent application, that’s a problem, with lubricant, they sort of wear away after a while. Engo patches can be great, especially at particularly at-risk sites on the foot.

It’s a little bit tricky because what you don’t want to do is reduce friction everywhere. But in the case of EB, it can actually work. So I have a few patients also that use ArmaSkin socks. ArmaSkin socks are a coefficient of friction strategy. They’re like a silicone-lined sock which forms the inner sock and then you put any sock on the outside.

And you kind of roll these socks on. You can’t pull them on such is the high coefficient of friction between the skin and the sock, which sounds counterproductive and counterintuitive. But the value of the ArmaSkin socks is that the interface formed by the outer of the ArmaSkin and then your athletic sock which is now the double sock interface, is much lower. So thereby it gives you reduced coefficient of friction at the sock interface for the whole foot. So ArmaSkin can work well there. You can also use a product called GlideWear Socks. GlideWear socks are also a coefficient of friction management strategy. They’re also a double sock strategy. They have two layers of very low friction between the sock-sock interface. And they’re a bit more like standard socks, but way more lower coefficient of friction. But they’re ones that you can just pull on rather than having to roll them on the ArmaSkin socks.

Wrapping up

Right, that’s all we have for today. I’ve gone two minutes over. That’s not too bad. If anyone has any questions, feel free to send me an email. We won’t be here next month for Office Hours. I’m going to Europe for a few weeks, well six weeks. And I’ll be back on board in August with Office Hours. We’ll be talking about when to lance blisters, how to do it, when not to do it, how not to do it and all that kind of thing. So, if you have any questions at all, please give me an email. I’m not leaving for another two weeks. So I’ll be here if you need me. Thanks everyone. Bye for now.

Meeting ended after 00:33:23 👋

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