All, in another thread Robert wrote:
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Here is a reliability study: http://www.japmaonline.org/cgi/content/abstract/91/5/262, regardless of their moderate reliability in the hands of these testers, what do the tests actually show? Hylton Menz assumed they were measures of foot pronation: http://www.japmaonline.org/cgi/content/abstract/88/3/119 Robert appears to be assuming that some inference can be made from these to planal dominance? Planal dominance, described by Don Green http://www.japmaonline.org/cgi/content/citation/74/2/98 relates to the relationship between a joints axial position and the amount of motion that should occur about that axis in the cardinal body planes. What does navicular drift / drop tell us about planal dominance, if anything, and if so, the planal dominance of which joint? Talonavicular joint? Navicular-cuboid joint? Navicular-medial cuneiform joint? Navicular-intermediate cuneiform joint? Navicular-lateral cuneiform joint? All of these? None of these? Given the relatively unconstrained nature of some of these joints, and Nesters contention that the axis is created by the motion, not vice versa, is the concept of planal dominance even valid and worthy of consideration for these joints?
P.S. edit the title please Craig, typo on the word navicular!
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'Planal dominance' is a term often used in surgical circles in the context of planning flatfoot surgery. When planning which particular operation the surgeon feels will provide the best chance of success (which I hope is a happy, pain-free patient) you assess the flatfoot deformity's dominant plane and offer a particular operation or combination of operations to address that as the major component of the painful flatfoot. An example of this would be a transverse plane dominant flatfoot, where you might perform an Evan's calcaneal osteotomy in an attempt to achieve a more 'rectus' foot - and hopefully that coincides with a patient with a functioning, more comfortable foot.
I guess Navicular drift (where I presume the assessor sees medial motion of the navicular?) would be one clinical sign of a transverse plane dominant flatfoot. Increased navicular drop I'm guessing would be one sign of a sagittal plane dominant flatfoot. So, in answer to your question as to what do they show - my best guess is that they are clinical signs that you could use to justify what type of surgery you will offer (in combination with other clinical signs, x-ray charting, etc...).
Your point on Nester et al's work is interesting. In between being totally overworked and severely lacking in motivation I have read one of that group's papers and it seems to me that their conclusions that the axis is created by motion (if that is their conclusion?) is based on the technology they have available to them - they seem to use a system for measuring relative motion of body segments that relies on a set of infra-red tracking cameras. Forgive me if I'm being a bit slow here, but they use a measurement tool that displays 3d motion of markers applied to different bit of the surface of the foot and ankle so I can't see what other conclusions they can draw from this? Even the bone pin study that I read didn't really tell me a great deal more than 'this bone moves this way relative to this one' etc... Can these 3d tracking systems tell you much more than that? I have not read that much around the area, but all they seem to churn out in that paper is angular motion of segments of the foot from what I recall. It did not seem all that clinically relevant, so I had a short attention span for the paper in all honesty, so I'd appreciate anyone's thoughts on that (probably in a different thread if it's not too relevant here).
Thanks,
Bob -
I grasp the calcaneus and apply inversion/eversion forces observing the forefoot to 'roughly' estimate the STJ planal dominance, fully realising there's multiple other joints and soft tissue structures affecting the motion of the distal forefoot.
I tried the drop/drift once at a boot camp and didn't fancy grovelling on the floor (dodgy knees).
Although the same criticism could be made for this method, I can't comprehend why I wouldn't use it to determine certain characteristics of the shape of the orthoses.
Looking forward to Michael and Robert with quick responses then in 24-36 hours time Kevin's. -
As I remember the measurements of Navicular drift and drop are part of FPI and it too much (whatever that is ) is seen as a bad thing or poor score as part of FPI.
We never seem to discuss drift as medial or lateral - can there be lateral Navicular drift ?, I guess there could when the compression forces cuboid-navicular increase.
We also never discuss Navicular lift, but tend to discuss the whole MLA , should we discuss Navicular lift ?
The point to these Questions all comes back to some of the discussion on the Midtarsal Joint Equilibrium thread, if we are going to look at the Midtarsal joint and surrounding soft tissue are we better to look at the forces acting on tissue and use free body diagrams.
Eric wrote this in the above midtarsal joint thread.
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Anyone got a copy of Don Greens planal dominance article - JAPMA don´t seem to have a copy on the website.
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The FPI item assessing navicular position looks at the “bulging” or congruence of the Talo-Nav joint, meaning only the transverse plane. More bulging = higher score = more pronated. If this is a bad thing…I´m not going into deep water.
talking about deep water, hope you and the family had a nice holiday is AUS. -
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Hope your on the improve soon Mate. -
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Was a nice Holiday, hope yours was good. Good luck with the Dr studies hope if goes fast. -
Ian,
Could I have a copy of that too please. Also, you wouldn't happen to have the Hylton Menz one would you?
many thanks
Robin -
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What influence does the state of the spring ligament have on this "planal dominance"? Moreover, what influence does the state of the spring ligament have on navicular drop and drift? Or, on the spatial orientation of helical axes of the joints I mentioned in the original post?
How do you assess the "planal dominance" of a flat foot deformity? Once the navicular hits the ground (sagittal plane), it can't go any further, but the transverse plane motion is somewhat less constrained.
As an aside, do surgeons repair spring ligaments in the same way that surgeons repair, for example, cruciate ligaments when performing flat foot surgery in feet in which this ligament is torn / elongated?
As another aside, when you perform an Evan's procedure, how do you work out how far you need to slide the calcaneus?
If we go back to your "surgical" definition of planal dominance and added markers to all of the bones of the foot, we should need to see all of the markers rotating and or translating about a single helical axis at given time in order to demonstrate a valid model of whole foot planal dominance. Do you think this is possible? I thought the point of some of the research Chris did with Erin Ward using the cadaver simulator was to work out which segments of the foot you could "lump" together, and which segments you could not? -
To all those who asked for a copy of the Don Green paper via this thread and PM - check your inboxes
IG -
Quick thought: we have navicular drop, i.e we measure the translation of the navicular in the sagittal plane; we have navicular drift, i.e. translation of the navicular in the frontal plane, put them together and we have a 2-dimensional translation axis for the navicular (whatever significance that may have), i.e. we can calculate the angulation of this translational axis for the navicular and hence its (the navicular translation axis) planal dominance in 2- dimensions. Why not measure anterior / posterior displacement of the navicular relative to the transverse plane too, and call it "navicular slide", put all three together and get a 3-dimensional translation vector for the navicular; call this composite measure "navicular translation"; get a 3-dimensional translational axis; work out the 3-dimensional planal dominance of this net translational axis and then work out its clinical significance? ;) If nothing else, if foot pronation and supination are triplanar motions it should give a better measure of foot pronation/ supination than measuring only navicular drop and drift as was Menz's contention to include "drift" with the "drop" measure. You can quote me on that and use this post in your references ;);):cool:
Then, I'll spoil your fun and tell you that foot position doesn't necessarily predict pathology, and ask you why you are measuring this anyway? Yet, if I can apply a "braking" force in a direction directly opposite the translational vector of the navicular, via a foot orthosis, should this not be the most efficient point and direction to apply such a force... assuming deceleration of navicular motion is important? Knock yourselves out. -
So, the butterfly thoughts of a madman on a Tuesday evening leads to this conclusion: we have spent the last too many years trying to control the position of joints with foot orthoses, when really we stand better chance of controlling the motion of the individual bones which make up the joints by applying forces to these bony segments (the joint is a fluid filled space between the bony segments) with our foot orthoses. So, if we assume that it is the deceleration of the motion of the segments that is important, if we work out the translational/ rotational motions of each bony segment in 3-dimensions, but within dynamic function, you should be able to apply forces via a foot orthosis which should be optimised to decelerate the motion of each segment by designing the orthoses to apply directly opposing, "countering" forces to decelerate the motions of the foot's bony segments with the minimal internal stress to the soft tissues by angulation of the orthosis surface geometry. Yet, we still have to allow enough stress to maintain the tissues within their zones of optimal stress, by manipulating the orthosis stiffness... Then it turns into a bummer, when we realise that the magnitude and direction of the translations and rotations etc, will be environmental and task dependent.... doh.
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The state of the spring ligament is often investigated pre-operatively using MR scans. It is not uncommon to find spring ligament attenuation/ tears in patients with tibialis posterior tendon dysfunction and associated flatfoot deformity. I guess it depends on the individual as to how much influence the spring ligament has on either drop or drift of the navicular. I have seen patients with both sagittal and/ or transverse plane dominant flatfeet having spring ligament attenuation (for some reason I see more transverse and sagittal than frontal plane flatfeet) and can not really say for sure how much influence attenuation of the ligament truly has on planal dominance – especially since I can not remember a single case where spring ligament rupture/ attenuation has occurred in isolation. And the same goes for the helical axis question. Very basically, if the spring ligament is rupture or attenuated, I repair it as part of the surgery.
I am not completely familiar with the methodology for using these markers and tracking systems for assessing foot function, but my best guess is that it may well be possible to determine an overall dominant plane of motion of a defined ‘foot’ segment. How clinically relevant (in terms of surgery) this would be is something I don’t know. The good thing about looking at an x-ray or a scan is that I can feel more confident to offer surgery to a certain area of the foot.
I must confess that I am not aware of the paper you mention, so if you could provide a reference I’d appreciate it. Did they have any conclusions that could affect the way we manage painful flatfeet?
Cheers,
Bob -
I'll try to find it tomorrow, if not you could contact Erin or Chris, I'm sure they could put you in the frame regarding their research and its conclusions.
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http://www.lowerextremityreview.com/issues/how-cadavers-could-change-your-practice
among the references he gives are these:
http://www.gaitposture.com/article/S0966-6362(08)00063-5/abstract
http://www.jbiomech.com/article/S0021-9290(06)00329-0/abstract -
As far as the 10mm thing goes, I can not remember a reference for this leading to CCJ pain/ compression, but I seem to think that there is one somewhere in my past reading. Probably in the bible, old testament of course ;) It’s a generalisation and some people will need less, some more. As previously discussed in our arthroeresis conversation on here, the eyeball and hit and hope will come in to play to an extent. There are some wedges available from certain companies that sell allogenic bone grafts for the Evans. These kits have a sizer set of varying width wedges to help you assess how big the graft needs to be which helps the eyeball process. http://www.youtube.com/watch?v=zH18_dZIYOE
Why don’t you shorten the medial column – lateral column is easier to lengthen. Medial column shortening also generally means fusions which could mean losing a ‘healthy’ joint (I’d rather preserve where I can). Hoke fusions do this to a point, but I prefer to offer these for sagittal plane dominant flatfeet, especially in the presence of OA. -
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"Shad is then approached by a set of five alien clones who share a group consciousness named Nestor. These aliens say their life is incredibly dull, since their whole race shares one mind. In order to be entertained, they have sent five members in a ship to join Shad's cause. Nestor asks no payment, saying they are completely self sufficient having developed a rubbish insole to peddle to intergalactic chiropractors with little or no knowledge of foot function."
Sounds an interesting fellow :D
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How does foot position relate to pathology - a fairly simple example of this would be a medial displacement calcaneal osteotomy. Pre-surgery, you have a valgus heel with ground reaction force consistently increasing pronation moments about your rearfoot which probably contributes to the common pathology of tibialis posterior tendon tears. Post surgery, you've fixed your tendon tear and medialised the posterior aspect of the calcaneus to prevent future recurrence of tib post pathology by increasing supination moments about the rearfoot (or reducing pronation moments, depending on how you look at it). -
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In Erin Ward's 'cadaver' article it says, "have also indicated that custom Root-type orthotics appear to ..., as well as decreasing the subtalar eversion." Is that position or magnitude of motion or ..?
And thanks for the articles, mark -
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But say we take the navicular , we have navicular at point X and we have -x to any degree which would represent one or more of the following navicular lateral drift, lift and your posterior slide. On the X+ side we have medial drift,drop and anterior slide of the navicular.
Now during gait we will have the navicular be in mutipule positions from -X to X to +X, in this change of position we will have changes in force on bone and soft tissue ie increase bone compression force or increased tension in ligaments or tendons. If these changes in position are too great we may have cartilage damage or plastic deformation and then pathology.
So if we have -X motion or +X motion which is too great, we will have a new position of the navicular which may mean pathology.
Zones of optimal stress, which was my thinking with free body diagrams and looking at the forces at play.
And with plastic deformation we may over time have more of X+ position ie more navicular drop or drift or anterior slide which may lead to even greater pathology -
Right then. Still a bit punchy so you'll have to forgive me if I'm a bit more "fighty" than usual.
I'm going to start from the top if I may, rather than try to piggyback in on Simon and Bob's debate.
Can one derive, with any degree of accuracy, the position of the sub talar axis by observing the navicular drift / drop? I'd say no. Several reasons. Firstly, as Simon points out, this assumes that the sub talar axis is biplanar. The further the axis from the sagittal plane the more movement there will be in the frontal plane from that orientation.
Far more significantly, there is the issue of midfoot stiffness. If the midfoot is munted, and can dorsiflex freely and far, the navicular could be weight bearing with little or no sub talar motion at all! And just to really confuse matters, Sub talar pronation involves dorsiflexion so in the sagital plane, sub talar pronation could actually be raising the navicular in the sagittal plane, even as it lowers it in the other two.:wacko:.
And of course we are measuring the position of the navicular. The amount (if any) of navicular movement relative to the other tarsal bones may also be a confounding factor.
So no. In a biomechanical sense, I don't believe we can make any profound observations about the location of the sub talar axis based on nav drift / drop.
As Simon observed, knowing the direction of travel of the navicular, and its start and end point, offer a very useful piece of information when deriving prescription, both the shape of the device and potentially the covering material as well. From this perspective one might consider the movement of the gross morphology of the foot to be as important as the details of the axial componants of that movement. There are a limited number of places and ways we control the foot. Knowing what percentage of movement is originating from which of the tarsal joints is interesting from a theoretical, and perhaps diagnostic viewpoint. But if you were to know that the movement was 60% Talonavicular joint and 40% Navicular-medial cuneiform joint as opposes to 40% / 60% would it make a vast difference to the way you shaped the arch of your orthotic?
Here is another point to consider. I am a great fan of the "directly opposing force" concept Simon mentioned. If the navicular was a cricket ball and I want to control its fall, I want to hold my hand / orthotic perpendicular to its direction of travel right? But there is another element. As Simon and Kevin's recent paper illustrated, the effect of a force is not just about its location, but also its vector. The vector of the ORF, the equal and opposite reaction force, will, I suspect, depend significantly on the vector of the incoming force.
The idea of measuring navicular slide is a great one from a biomechanical point of view. But how much would that inform our treatment? We can't put anything in front of the navicular to stop it sliding forward, the cuniform gets in the way!
Thats why I use the two dimensional test to derive a two dimensional vector.
The drift / drop test may not tell me, with any degree of accuracy, the planal dominance of the sub talar joint axis, the mid tarsal axis, or any other axis. But these axes are theoretical constructs designed to help us reach a goal, that being the shape of the device. So far as that is concerned, when I talk about planal dominance, I am happy enough to think in terms of the planal dominance of the movement of the arch as measured from its peak, the navicular. Its crude, but then so are orthoses. While biomechanics, as a pure science, has no room for pragmatism, I believe MSK podiatry does, provided it does not masquerade as other than it is. If I have, in the past, inferred such then I shan't do so again.
And if you made it to the bottom of that ramble you're a better man / woman than I!!
Cheers
Robert -
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Help me out. Give me an example. Foot 1 has no slide and a 45 degree movement medial/plantar of, say, 1cm. Foot 2 has a 0.5 cm anterior slide at the same medial plantar vector. So we have 2 parts drift, 2 parts drop and 1 part anterior slide. How would I make my insole differently to take this into account?
I suppose higher friction cover would make a difference, but I tend to use those anyway.... -
A quick analogy, you drive your car along a horizontal surface into a concrete wall (orthotic) which is vertical and perpendicular to the direction of motion; you then drive you car into a concrete wall which is a wedge shaped inclined plane and therefore at an angle <90 degrees to the direction of motion. Which wall will decelerate the car more effectively?
Missed the bit about the talus. But you are not measuring the movement of the talar head, you are measuring the navicular displacement, and while the navicular articulates with the talar head, it also articulates with a host of other bones. Lets say I fused the navicular at all of its articulations other than the talonavicular joint and then moved the subtalar joint in isolation, what motion of the navicular might we observe? -
I'm not explaining this well. I feel a video with a skeleton and some cardboard coming on... -
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The cardboard video is uploading as we speak but I tried it with foam and that illustrated the point rather better. If I get time I'll do that one this PM.
Good thread BTW. Thanks for starting it. -
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ignore, going mad.
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Here Ya go.
Its not just for you simon. In fact its mainly for those folk following along (I hope there are a few) who are wondering what the hell we are talking about.
For some reason, try as I might, I cannot get these things to embed. Craig, would you mind? Thanks.
Here is number 1
Last edited by a moderator: Sep 22, 2016
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Impact attenuation during weight bearing activities in barefoot vs. shod conditions
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Impact frequency data suggest unique risks for forefoot strikers
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