Clinical Biomechanics Boot Camps

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Tag archives for biomechanics

The Supination Resistance Test

In the early days of the Clinical Biomechanics Boot Camps we spent a lot of time on the supination resistance test and the concept of supination resistance, as the concept was so new to so many, but as time went by less time was spent on it as the test has become so widely used and quite pervasive when it comes to prescribing foot orthotics.

The test was first described by Kevin Kirby, DPM and we have done a lot of work on it with a number of studies exploring the concept. Along with that research I used clinically and we did a lot of practical sessions on it in the boot camps – all of this lead to what I think was a good understanding of it and just how useful it was to use clinically when it came to the prescribing of foot orthotics in clinical practice. I think those who did the clinical biomechanics boot camps did get to agree with me just how important that the concept was for the prescribing of foot orthotics and understanding pathology. There are a lot of threads on Podiatry Arena on the topic that get updated regularly.

The supination resistance test is simply a test to estimate just how much force is needed to supinate the foot and then applying that knowledge to how much force is needed to come from the foot orthotic. If the force to supinate the foot is high, then the force needed from a foot orthotic needs to be high. No point using a soft flexible foot orthotic in those with a high supination resistance as the orthotic is probably going to do nothing. If the supination force is low, then a soft flexible foot orthotic is going to be adequate. Using a rigid inverted type of foot orthotic in a foot with low supination resistance is probably going to sprain the ankle.

For our research we used a device that we built to quantify it but that device really has no practical use in clinical practice, so the use of the hands and manually estimating is adequate. There are some devices on the market, such as the Keystone that can be used to put a number on it.

What I used to like saying to people who were unfamiliar with the test is to just do it. Get a feel for it. Find those feet that are high or low and see how that might relate to the pathology that the patient has. Get a feel for how people with different levels of supination resistance respond to different foot orthotic designs. You soon start to see patterns.

Posterior tibial tendon dysfunction or adult acquired flat foot or progressive collapsing foot deformity?

What should it be called? I have long been part of the school that thinks we should be sticking with the posterior tibial tendon dysfunction name as that is the one that has mostly stuck and the problem was considered one of the posterior tibial muscle no longer being able to do its job – it just made sense. Two things are starting to change my mind:

  1. The pathomechanical and other studies have shown there is a lot more to it than just the posterior tibial tendon.
  2. The confusion between posterior tibial tendon dysfunction and posterior tibial tendonitis is too common and leading to wrong treatment choices (especially in runners).

It is the later point that is getting more and more attention. They are not the same thing. Posterior tibial tendonitis is an overuse injury in active healthy people. Posterior tibial tendon dysfunction is a progressive flatfoot deformity in older, often overweight adults. Two totally different sets of symptoms; two totally different populations; two totally different sets of clinical features …. yet some think they are the same thing on a continuum and some mix the two up and use the same treatment interventions. Nope.

I now think we should be calling posterior tibial tendon dysfunction either adult acquired flatfoot or progressive collapsing foot deformity to avoid the confusion and better reflect the underpinning pathological process. This terminology of progressive collapsing foot deformity is the name that seems to be being used more frequently in the most recent literature on this problem.

Peroneal Tendinopathy is easy!

In my hands peroneal tendinopathy or tendonitis used to be a challenge. In the past I reckon I was close to a 100% failure rate in managing it. In the last 10 or so years I think I am now close to a 100% success in managing it. What changed? It was based on our research evidence. I talked about that in this blog post: Peroneal Tendonitis in Runners on my running research blog. It was pretty clear that almost everyone with peroneal tendinopathy had a lower than average supination resistance. That means the force needed to supinate the foot was low and as a consequence the peroneal tendons have to work harder, increasing the risk for tendinopathy. This also means that those with it need lateral wedging under the heel to decrease the loads in the tendon. That wedging actually leads to a substantial reduction in the forces that the tendon is subjected to, so hence the lateral wedging is a very and often is dramatically effective to manage peroneal tendonitis.

Yes, lateral wedging does try to pronate the foot more, but never had a problem with doing that. It did take a mindset change to get confident to start doing this 10 or more years ago, but I have not looked back. This is a perfect example of research informing and changing clinical practice.

This also means that a typically arch supporting medially wedged foot orthotic is going to increase the load on the peroneal tendon and is not going to be indicated. This also explains why I had almost a 100% failure on managing this in the past.

Also, of course, we do the usual load management approaches to this tendon once that reduction in load on the tendon with the wedge is done.

The Clinical Importance of Navicular Drop and Navicular Drift

I am a big fan of teaching people how to measure the navicular drift and drop. However, the evidence is that for clinical use they are not that reliable, so that does limit the usefulness of these clinical tests in clinical practice.

Having said that, I still think we should be teaching how to do it, but in the context of the unreliability of them. The reason for this is that the concept behind navicular drift and drop does have implications for foot orthotic prescribing. What learning how to do the tests gives clinicians is an appreciation of the relative movements of the midfoot in the sagittal and transverse planes. Navicular drop measures the sagittal plane motion of the midfoot and navicular drift measures the transverse plane motion of the midfoot. Learning how to do the measurement of these two gives an appreciation of the relative motion of that midfoot in the sagittal and transverse plane. Once that appreciation and understanding is grasped, then there is probably no need to do the measurements on a routine basis in clinical practice. You can just observe it and note how much drop there is compared to how much drift there is. Are the about the same or is there more of one compared to the other?

My impression is that the amount of navicular drift should be about the same as navicular drop. If drop is greater, then that means that there is more movement in the sagittal place compared to the transverse plane. This means there is more arch collapse, when means that the foot orthotics need to have more support in the midfoot. If the drift is greater, then that means there is more movement in the transverse plane compared to the sagittal plane. This means that there is more movement of the midfoot medially rather than arch collapse. This means that foot orthotics need more medial and lateral support to control that midfoot transverse plane motion.

The Lunge Test Should be Done in Footwear

I think we all know that the range of motion of the ankle joint is important for normal function. I have made no secret of how useful I think the lunge test is in evaluating that ankle joint range of motion. While there is some discussion as to what is the normal value for the lunge test (I think its around 35-38 degrees) or even if the ankle joint range of motion must be done in subtalar joint neutral (I don’t think it doesn’t need to be), the lunge test is still proving useful and being widely used in clinical practice.

In the early days of running the Clinical Biomechanics Boot Camps we used to do a lot of practicals on the lunge test. Participants would practice on each other and I would go around the room to check how they were going. It was surprising just how many would be considered tight on the lunge test. I would then use my hand as a “heel raise” and get then to stand on that. Almost always they then had a normal range of motion using the lunge test. I soon come to realise that the “heel raise” of my hand was doing what the shoe did, in that all shoes typically have a higher stack height in the heel than the forefoot (the drop). People function and walk in shoes, so the lunge test (and probably as many clinical tests as possible) should be done in the shoes. When we started doing the lunge test barefoot and then in the shoes at the Clinical Biomechanics Boot Camps, almost everyone who was under what was considered normal, was within normal limits when the test was repeated in their footwear. This has implications of the nature of the intervention and if the calf muscles were really limited or not.

There is a whole lesson in the online version of the Clinical Biomechanics Boot Camp devoted to this.

Please consider doing the lunge test in the patients shoes.

The Entity that is “Functional Hallux Limitus”

Functional hallux limitus is a theoretical construct. There is no doubt that the phenomenon that is functional hallux limitus exists, but that can often be as far any any agreement or consensus gets with this. There is no doubt that there are some feet when the foot is up in the air that there is a full range of motion available at the the first metatarsophalangeal joint yet when that foot is weightbearing during gait, that joint just does not want to move. That is the definition of what functional hallux limitus is.

I have written about this a lot, speculating that functional hallux limitus has many possible causes and that it may be better to conceptualize it as a nothing more that each person having a variable stiffness range of motion at the first metatarsophalangeal joint and that this may be related to the windlass mechanism. If this is the case then what we typically considered to be a functional hallux limitus is really the extreme of this variable stiffness and that functional hallux limitus probably exists as a continuum and not as an either/or entity.

Abductory twist or medial heel whip?

The abductory twist is an observation that is frequently made during a gait analysis. Just recently I have started to notice a common terminology issue and I am somewhat confused if they are the same thing or separate things. Most people seem to use the term ‘abductory twist‘ as the same thing as a ‘medial heel whip‘. I believe they are probably different things and they get confused as to what the entity actually is.

I consider an abductory twist to be that sudden medial or abductory movement of the heel just as the heel come off the ground. I wrote here about the possible reasons for this, one being an ‘overpronation’ and the other being a functional hallux limitus. I do not consider that this comes from a more proximal problem like others do. Some people also call this a medial heel whip. They only way to help this is to deal with the ‘overpronation’ or functional hallux limitus. Exercises can not help this.

However, when you listen to or read about what some people consider to be a medial heel whip they are talking about the heel being whipped medially, especially in runners, after the foot has come off the ground. That is something different to the abductory twist that has been previously described. I do consider that this medial heel whip could be due to a proximal problem around the hip and pelvis. The only way to deal with this is deal with the proximal causes and exercises may be very helpful.

If you hear or read someone talking about an abductory twist and/or medial heel whip try to ascertain which one of the two entities they are talking or writing about and just when in the gait cycle that they are observed.