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The xrays are a brilliant depiction of the dynamacy of the STJ location in different STJ positions. But how does this impact on treatment options?
I recollect in the tertiary days, that a medially located STJ axis needed a lot of force (postero-medial) to combat (large) pronation (torque) and the mechanically advantaged peroneal musculature.
Physics nomenclature is not my forte, so pardon me in advance. How does the new dynamic understanding translating to treatment options. How does this help Scott's patient? Is the next step an orthoses that has a changing role/impact through the gait cycle?
Ron Bateman
Physiotherapist (Masters) & Podiatrist
Ron:
I don't believe that Scott was asking solely how we should treat his patient or describe all the treatment options available to help this patient. Rather he was asking a question of why he noted his patient with what seemed to be a lateral subtalar joint (STJ) axis was pronating in gait.
Even an automobile mechanic is expected to know in detail how the automoble he/she is repairing works and functions. In fact, I would expect the best automobile mechanics have a much greater understanding of function of automobile components when compared to a mediocre automobile mechanic. If this is the case, then wouldn't you also expect the podiatrist who is working on the part of the human body that is regularly subjected to the greatest magnitudes of external loading forces during daily activities to understand, in great detail, about the mechanical function of the foot? Wasn't Scott asking a question about foot biomechanics that should allow him to acquire a much better understanding of how his patient's feet work so that he can become a better "foot mechanic"?
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Re: Lateral STJ axis feet that look as though they are pronating
Quote:
Originally Posted by Simon Spooner
P.S. all foot orthoses have a changing role / impact through the gait cycle. Is this concept new to you and others, and worthy of a new thread?
Don´t that they have to as every ground-shoe-foot-orthotic impact will be slightly different and therefore the role the that the orthotic has will be different every time ? Thats they way Ive been thinking.
Re: Lateral STJ axis feet that look as though they are pronating
Quote:
Originally Posted by m weber
Don´t that they have to as every ground-shoe-foot-orthotic impact will be slightly different and therefore the role the that the orthotic has will be different every time ? Thats they way Ive been thinking.
Think about how the net reaction force vector progresses during the contact phase, and how the shape of the foot-orthosis interface influences this.
Re: Lateral STJ axis feet that look as though they are pronating
Quote:
Originally Posted by Simon Spooner
Think about how the net reaction force vector progresses during the contact phase, and how the shape of the foot-orthosis interface influences this.
Ok back.
The orthotoic reaction force ( ORF)can only be equal and opposite to the force the foot applies to the orthotic. So the point of impact will be the place that the net force vector is at it highest it will then decrease. The only time that the vector can increase is if the foot applies more pressure on the device. This can be achieved by reducing the area of contact with the orthotic at times such as when the heel lifts and at toe-off.
The shape of the foot-orthosis interface can not increase the amount of force vector but can change the angle of that force vector.
ie the medial skive will cause a change in the angle of the ORF compaired to a flat heel.
A more contured ( ie the shape of the foot) or a negative conture ( ie skive device ) will also return the force faster and this will mean that the orthotic will cause a earlier change in foot kinemetics during the gait cycle.
note: I made up negative conture for heel skive not sure if it´s a good discription for a device which has had some of the positive foot mold removed in manufactor such as a heel skive or cuboid notch.
Re: Lateral STJ axis feet that look as though they are pronating
Quote:
Originally Posted by Simon Spooner
P.S. all foot orthoses have a changing role / impact through the gait cycle. Is this concept new to you and others, and worthy of a new thread?
With all this advanced knowledge about dynamic axes of rotation, I thought the next step in orthotic therapy would be to better target therapeutic orthotic reaction forces. I assume old school viewpoint was single static axis of rotation and hence the old-school therapy of ORF here would suffice.
I assume newer school viewpoint in IAOR and more dynamacy. Accordingly, what can we do to orthotics to provide the most targeted therapeutic ORS pending the specific moving axis of rotation.
And another point on futuristic science fiction orthotics:
Surely, the rearfoot post (for instance) of an orthotic has a greater impact at heel strike than it does during heel lift. Likewise, a forefoot valgus wedge for instance comes into play at FF loading to toe-off I would assume.
If I crystal ball it now, some clever dick in 100 years may be able to work out how the rear aspect of an orthotic can still maintain its strong influence after heel lift; and how the anterior aspect can have a beneficial impact outside FF-load - to - toe-off. Debate will remain regarding what would be the clinical benefit, but that may not be settled until we can actually achieve it.
That is what I mean about futuristic orthotics having a more changing/dynamic function through different aspects of gait, in accordance with pathology (clinically) and the those dynamic axis of joint rotation (theoretically).
Ron Bateman
Physiotherapist (Masters) & Podiatrist
Re: Lateral STJ axis feet that look as though they are pronating
Hi All
I have been following this thread with interest and a couple of questions popped up.
1. Looking at the video that Dave provided, whilst there seems to be some pronation evident, I would not of thought it as any more than is required in normal gait (to act primarily as a shock absorption measure). Definitely not enough for me to worry about preventing the degree of it with an orthosis.
My thought process is that due to the lack of propulsion in this instance there is no supination occuring through late midstance and toe off. This results in less resupination of the foot in general during the swing phase which in turn causes a more everted heel strike (which is exacerbated by the genu valgum). Thoughts?
2. Could the genu valgum be caused due to muscular weakness in some areas and tightness in others, such as overly tight ilio-tibial band and weak gluteus medius?
3. In light of some recent evidence (Nester etc), indicating significantly more movement in the talo-navicular and calcaneo-cuboid joints than the STJ and possible impact this has in gait in general, have we been focusing too much on the rearfoot at the expense of the forefoot in discussing what we are seeing in this type of case?
I am by no means a biomechanical expert, rather I am interested in peoples thoughts and ideas on these and any other questions.
Re: Lateral STJ axis feet that look as though they are pronating
Quote:
Originally Posted by Andrea Castello
Hi All
I have been following this thread with interest and a couple of questions popped up.
1. Looking at the video that Dave provided, whilst there seems to be some pronation evident, I would not of thought it as any more than is required in normal gait (to act primarily as a shock absorption measure). Definitely not enough for me to worry about preventing the degree of it with an orthosis.
Andrea, The point was that she pronates rather than supinates, which is what might be predicted by a observation of genu valgum, valgus f/foot and lateral stj axis
My thought process is that due to the lack of propulsion in this instance there is no supination occuring through late midstance and toe off. This results in less resupination of the foot in general during the swing phase which in turn causes a more everted heel strike (which is exacerbated by the genu valgum). Thoughts?
Wouldn't an everted heel position combined with genu valgum be likely to result in a supination of the STJ at heel strike?
2. Could the genu valgum be caused due to muscular weakness in some areas and tightness in others, such as overly tight ilio-tibial band and weak gluteus medius?
A true genu valgum may be due to uneven growth or erosion of the epiphyseal plates of the femoral condyles. More likely weak ITB allowing internal knee rotation gives the impression of genu valgum
3. In light of some recent evidence (Nester etc), indicating significantly more movement in the talo-navicular and calcaneo-cuboid joints than the STJ and possible impact this has in gait in general, have we been focusing too much on the rearfoot at the expense of the forefoot in discussing what we are seeing in this type of case?
Which paper is this? I think I've read it but I can't find it at the moment.
I am by no means a biomechanical expert, rather I am interested in peoples thoughts and ideas on these and any other questions.
Warm Regards
Andrea
Cheers Dave Dave
__________________
Descartes seems to consider here that beliefs formed by pure reasoning are less doubtful than those formed through perception.
Re: Lateral STJ axis feet that look as though they are pronating
Prediction: bone pin study soon that shows no significant difference in kinematics with and without orthoses. I have no inside info, I'm just guessing.
Re: Lateral STJ axis feet that look as though they are pronating
Hi Dave.
In isolation you would expect the rearfoot to supinate, however what about shifts in the lower back, pelvis and hip moving the CoF more medially again? Wouldn't this have the effect of reducing or cancelling out the supination moment?
Also what about the ability for the Talo-Navicular in particular to account for that supination moment through increased mobility (over the STJ)?
Again I'm only thinking out loud here and am asking these questions in the interest of challenging my knowledge and beliefs.
Re: Lateral STJ axis feet that look as though they are pronating
Quote:
Originally Posted by Andrea Castello
Hi All
I have been following this thread with interest and a couple of questions popped up.
1. Looking at the video that Dave provided, whilst there seems to be some pronation evident, I would not of thought it as any more than is required in normal gait (to act primarily as a shock absorption measure). Definitely not enough for me to worry about preventing the degree of it with an orthosis.
My thought process is that due to the lack of propulsion in this instance there is no supination occuring through late midstance and toe off. This results in less resupination of the foot in general during the swing phase which in turn causes a more everted heel strike (which is exacerbated by the genu valgum). Thoughts?
2. Could the genu valgum be caused due to muscular weakness in some areas and tightness in others, such as overly tight ilio-tibial band and weak gluteus medius?
3. In light of some recent evidence (Nester etc), indicating significantly more movement in the talo-navicular and calcaneo-cuboid joints than the STJ and possible impact this has in gait in general, have we been focusing too much on the rearfoot at the expense of the forefoot in discussing what we are seeing in this type of case?
I am by no means a biomechanical expert, rather I am interested in peoples thoughts and ideas on these and any other questions.
Warm Regards
Andrea
As you have shown, you don't have to be a biomech expert to come up with gold.
1. You have better eyes than me.
2. No
3. Great point. Forefoot pain is out there in bucket loads. But do we hang on to some myth that "its all in the rearfoot"? Despite the forefoot pain being the main complaint, there are many devices out there that end proximal to the met-heads that have no features at all in the distal section. No domes, no padding, no forefoot wedging; nil.
Its has been all about introducing physiological forces at the STJ that dominates a guestimate of 95% of our thinking/discussion. But forefoot pathologies/complaints are surely much much greater than 5%!!!
We carry on as if the heel never lifts in stance IMO, because at FF load, the influence (at the forefoot) of the rear section of an orthotic surely diminishes. At this stage, we have body weight going through the forefoot, and I assume then through the TN, TC and up the leg.
How are we changing the forces through the forefoot at FF load, if the plain shell device ends proximal to the met heads? Surely to change forefoot pathology, the device must have an effect at the distal half of the shell and beyond.
Ron Bateman
Physiotherapist (Masters) & Podiatrist
Re: Lateral STJ axis feet that look as though they are pronating
Linear Mode
