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The Other Proprioceptive Medicine

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Phil Wells, Sep 10, 2007.

  1. deco

    deco Active Member

    Thought I'd uploaded pictures properly

    I'll try again
     

    Attached Files:

  2. Kevin,
    I do not see the "increased lateral deviation of the STJ axis on the left foot" which you describe. Is this real or imagined? Where is the axis?
    What I see is an inverted calcaneus. This can be the result of many factors, many of which can cause mechanical instability of the ankle.

    You describe the "tonic peroneal activity" of a patient, and speculate that this is an indication of succeptibility to lateral ankle sprain. If you examine research on neuromuscular control of the ankle, you will find quite the contrary.

    I refer you to my article: Richie DH. Functional Instability of the Ankle and the Role of Neuromuscular Control; A Comprehensive Review, Journal Foot and Ankle Surgery, 40:240-251, July/August 2001.
    I reviewed over 70 quality studies of neuromuscular control of the ankle and the causative factors of chronic ankle instability. I would ask that you focus on the sections dealing with peroneal latency and muscular control of torque on the ankle joint complex.

    Many esteemed researchers have determined that patients with chronic ankle instability have delayed peroneal reaction time. They have used terms such as peroneal latency and electromechanical delay to describe the time period which elapses between inversion perturbation and ultimate generation of eversion torque on the ankle joint. Many have proposed that a "pre-activation" of the peroneals is necessary for proper protection of the ankle from inversion sprain during sudden perturbation. When the peroneals are properly pre-activated, inversion perturbation causes an eccentric contraction of the peroneals, which will generate a significant stronger eversion torque on the ankle joint complex than a concentric contraction. My paper quotes one study which estimated that a pre-activated peroneal musculature is capable, thru a plymetric eccentric contraction, to generate more than double the eversion torque on the ankle necessary to resist an inversion sprain.

    So, I propse that your patient with tonic spasm in her peroneals is better prepared to protect her ankle from inversion perturbation and subsequent disruption of her lateral ligamentous structures. This, despite her imagninary deviated axis of her STJ!

    Doug
     
  3. Doug:

    The lateral deviation of the subtalar joint (STJ) axis is real, of course! The axis can be found any number of ways, two of the ways I have invented or helped invent and which I have authored or coauthored papers on within the peer-reviewed medical literature (Kirby KA: Methods for determination of positional variations in the subtalar joint axis. JAPMA, 77: 228-234, 1987.; Spooner SK, Kirby KA: The subtalar joint axis locator: A preliminary report. JAPMA, 96:212-219, 2006.)

    These patients do not have a tonic spasm in their peroneals. They have tonic contractile activity of the peroneals in order to keep their foot from oversupinating due to the increased STJ supination moment from ground reaction force acting across a STJ axis that is more laterally located relative to their plantar foot than normal.

    You think that STJ axis deviation is "imaginary"? I am confused by your statement. You must think then that the STJ axis has the same spatial location from one foot to another relative to the plantar foot?? All I can say that STJ axis deviation is not imaginary, it is very real. I have been measuring STJ axis deviations in feet for about 24 years now. My original technique came directly from discussions with John Weed, DPM, in 1984, and a technique he performed in order to determine when to use "anti-pronation orthosis techniques" or not. We have used my technique of axis palpation on cadavers at the Penn State Biomechanics lab with 3D motion analysis with good results.

    In fact, STJ axis deviation is no more imaginary than are "forefoot varus", "forefoot valgus", "rearfoot varus" and "rearfoot valgus" deformities that were proposed by Root et al as being the etiologies of many pathologies of the foot and lower extremity. The difference with the STJ axis deviation terminology/system is that I am using the spatial location of the STJ axis relative to the plantar foot as my system of reference rather than the calcaneal bisection relative to the ground or with the STJ in "neutral position".

    Doug, the pathologies that Mert Root described using his STJ neutral system of classification such as a "rigid forefoot valgus" and "excessive degrees of rearfoot varus" will result in a laterally deviated STJ axis. Root said that a rigid forefoot valgus will cause excessive STJ supination. My system, since it uses the plane of the plantar forefoot placed parallel to the ground (i.e. plantar parallel position) to assess STJ axis position, will find that a patient with a "rigid forefoot valgus" will have also have a "laterally deviated STJ axis". For "excessive degrees of rearfoot varus" using Root's description, the inverted heel of the "excessive rearfoot varus deoformity" will also cause a laterally deviated STJ axis since the plantar calcaneus will now be more medially located relative to the talo-calcaneal joint and the STJ axis will map out more lateral on the plantar heel than a subject that had a less inverted heel.

    As further evidence of the importance of and the interest from the mainstream international biomechanics community in STJ axis location, I have been involved with research with Greg Lewis (getting his PhD) and Steve Piazza, PhD, at the Penn State Biomechanics Lab for the last three years. We are directing our research toward mapping out the spatial locations of the STJ axis in live subjects using fast MRI scanning of the subject's feet being moved with a non-metallic platform. Like I said, the STJ axis deviations we see are not imaginary, they are very real. Our first paper has already been published on cadavers (Lewis GS, Kirby KA, Piazza SJ: Determination of subtalar joint axis location by restriction of talocrural joint motion. Gait and Posture. 25:63-69, 2007) with our second paper on live subjects to be published within the next year in the Journal of Biomechanics (Lewis GS, Cohen TL, Seisler AR, Kirby KA, Sheehan FT, Piazza SJ: In vivo tests of an improved method for functional location of the subtalar joint axis. Submitted to J Biomechanics, November 2007).

    For further information on the biomechanical importance of STJ axis location, you may want to read Dr. Piazza's 2005 paper on the subtalar joint and it's mechanics (Piazza SJ: Mechanics of the subtalar joint and its function during walking. Foot Ankle Clin N Am, 10:425-442, 2005) in which he references two of my papers from his 69 references. It is attached below.

    Great discussion!:drinks
     
    Last edited: May 1, 2008
  4. Declan:

    Thanks for the case reports on patients with laterally deviated subtalar joint (STJ) axes. Now that you have made your patients better with evaluating their STJ axis position, what do you think about whether there is such a thing as a laterally deviated subtalar joint axis, whether STJ axis lateral deviation is important mechanically and whether a laterally deviated STJ axis is real or imaginary?

    Going to the PFOLA meeting again this year in Vancouver? Maybe I'll buy you a Guinness, just for old times sake.:drinks
     
    Last edited: May 1, 2008
  5. efuller

    efuller MVP

    I have to add to Kevin's comments about "theoretical lateral deviation of STJ axis." You cannot deny that there is variation of the location of the axis. (Inman's book). When I was lecturing with Kevin and doing my demonstration on examination techniques I said that this particular woman had a significantly laterally deviated STJ axis and then Kevin pointed out the "static stance" contraction of the peroneal muscles. We were able to demonstrate the effects of a laterally deviated STJ axis not in a journal, but in an audience of over 100.

    It's not just about STJ axis position. It's about the location of the center of pressure relative to the STJ axis position. Nigg has shown that lateral flares on shoes (shifting the center of pressure more laterally) will increase pronation velocity. In the pictures submitted of laterally unstable feet on this thread you can see the that the position of the weight bearing foot is more medial to the ankle (or more specifically the articular facets on the talus that determine the location of the STJ axis.) If there is more foot medial to the axis, that foot will supinate easier. Root Orien and Weed were correct in noticing that some feet with inverted heels will often have lateral instability. However, there are exceptions to this rule. There are feet with inverted heels that have most of their weight bearing surface lateral to the ankle. It's not the position of the heel bisection, it's the position of the force relative to the axis.

    It's not surprising that authorities on neuromuscular control do not mention mechanical factors. Neuromuscular experts will look for neuromuscular explanations. There was a presentation at the last PFOLA meeting on ankle instability who cited my paper on COP and STJ axis Fuller, E.A. Center of pressure and its theoretical relationship to foot pathology. J Am Podiatr Med Assoc. 1999 Jun;89(6):278-91. The presenter mentioned STJ axis position as a cause, but he did not incorporate the concept into his conclusion. He reported a paradoxical finding that people with lateral ankle instability often had strong peroneal muscles. What he did not mention was this finding is entirely consistent with laterally deviation of the STJ axis. People with laterally deviated STJ axes will need to use their peroneal muscles more and hence have strong muscles, yet they will still be laterally unstable. They will be unstable because there will be a greater supination moment from the ground with slight inversion as compared to feet with an average STJ axis location. I realize that they are not hear yet, but I am confident the scientific studies will come.

    Regards,

    Eric
     
  6. Playing devils advocate: given the manner in which muscle strength is commonly tested in a clinical environment, is the observation of people with lateral ankle instability often having strong peroneal muscles consistent with a laterally deviated STJ axis? Moment = force x distance; a laterally deviated axis should result in a reduction in lever arm distance of the peroneals and thus one should expect them to test weaker, unless contractile force is increased. Do we see any evidence that would account for an increase in contractile force such as an increase in cross sectional area of the peroneals in patients with chronic lateral instability of the ankle?

    BTW I've been looking at variation in axial position since the early 90's, I have observed a correlation between more lateral STJ axial positions and lateral ankle instabilities. Unfortunately, correlation does not differentiate cause from effect.
     
    Last edited: May 1, 2008
  7. deco

    deco Active Member

    "Thanks for the case reports on patients with laterally deviated subtalar joint (STJ) axes. Now that you have made your patients better with evaluating their STJ axis position, what do you think about whether there is such a thing as a laterally deviated subtalar joint axis, whether STJ axis lateral deviation is important mechanically and whether a laterally deviated STJ axis is real or imaginary?

    Going to the PFOLA meeting again this year in Vancouver? Maybe I'll buy you a Guinness, just for old times sake"

    Hi Kevin,

    Glad I can make a contribution to this topic. To answer your questions I do believe it is possible to have a laterally deviated STJ axis and the position of this axis is mechanically significant. This is in my opinion and is something that is very real!!

    I will hopefully be able to attend PFOLA in November where I will look forward to talking to you a bit more about the MTJ and stiffness over a few beers (or guinness)!!!:drinks

    Best Wishes

    Declan
     
    Last edited: May 1, 2008

  8. Simon:

    I have noted that in patients with laterally deviated STJ axes, that their pereoneals seem much stronger when the STJ is placed in the maximally pronated position while testing than when the STJ is in the neutral position. [These patients invariably are some of the few patients that I see that actually stand in the STJ neutral position.....abnormal feet stand in neutral position, "normal feet" stand pronated from the neutral position, in my clinical experience.]

    The increase in apparent peroneal "muscle strength" makes good mechanical sense to me because the pronation moment arm for both the peroneal muscles will increase with the STJ rotated into its maximally pronated position so that in this maximally pronated position the "strength" of the peroneals will seem greater. However, in STJ neutral positon, the pronation moment arm of the peroneals is greatly reduced so that the peroneals need to exert significantly more contractile force to produce a significantly reduced STJ pronation moment while in STJ neutral position.

    Here is the bottom line regarding "muscle strength", until researchers and clinicians fully realize that what we currently call "muscle strength" is actually a combination of the three mechanical factors: 1) capacity of the muscle to exert contractile force, 2) distance from the muscle to the axis of rotation of the joint (i.e. muscle moment arm), and 3) distance from the examiner's applied manual force to the axis of rotation of the joint (i.e. resistance moment arm), then both researchers and clinicians will continue to be confused over research data and clinical findings regarding "muscle strength" and how they relate to function and pathology in the human foot and lower extremity. This includes most of the available research on "peroneal muscle strength" seen in papers on lateral ankle instability. These three important mechanical facts regarding "muscle strength" should be included in any serious discussion of lateral ankle instability.

    By the way, Simon, if I remember correctly, one of your feet had a more laterally deviated STJ axis and this is the one that had recurrent ankle sprains. Can you elaborate on this further?
     
  9. So what you are saying is that by standing in a pronated position the STJ axis is shifted more medially than it would be in neutral position standing and that this increases lever arm hence the muscles test strong- right?

    Janda (1979) lists the peroneals as being primarily phasic in function and suggests that in a dysfunctional situation phasic muscles tend to become weak. Given that the position of rotational equilibrium about a joint is to a large extent determined by the muscular forces acting about it's axis, if Janda's observations were correct, should we not expect to see an increased supinated position of the foot in standing unless some other, "new" forces are at play? How is this pronated STJ position achieved then? One possible explanation appears to be via the increased activity level within the peroneals that you described in your case observation?

    Agreed.

    I'll try and post some of the video we shot and the X-rays of my "funny" foot in max pronation and max supination with the STJ locator in situ when I get back from Poland (if I can find them!- moved house and several computers since then). As I recall, it seems to support the theory ;)
     
  10. deco

    deco Active Member

    I'll try and post some of the video we shot and the X-rays of my "funny" foot in max pronation and max supination with the STJ locator in situ when I get back from Poland (if I can find them!- moved house and several computers since then). As I recall, it seems to support the theory ;)[/QUOTE]


    Hi Simon,

    Any chance of a look at that funny foot?

    Declan
     
  11. Yeah, when my hangover subsides. Rugby tour + Poland = too much vodka = brain still not with it. I got it on CD-rom somewhere! I'll find it (if only I was a pack-rat like Kirby)

    You a daddy yet?
     
  12. deco

    deco Active Member


    Cheers Simon,

    Cleonagh was due yesterday but no movement so far!!

    Declan
     
  13. deco

    deco Active Member

    Rugby in Poland?
     
  14. You got it. Cool double cool. They're steroid monsters, but lacking in skill. One of their players fractured his fibula. Or, should I say one of our players fractured one of their player fibula. Nice. We won.

    Grace came 10 days late, by the time she arrived we were both going round the bend. Sounds like you need to keep off the dark stuff for just a few more days- you never know when you got to make that drive (midnight and foggy when I did it- longest couple of miles I ever had to drive). I'm sure you'll make up for missed drinking time later. Good luck, and let us know the result.
     
  15. Stanley

    Stanley Well-Known Member

    Declan,

    Are you saying that the reason for the peroneal's inability to stabilize the ankle is related to the lateraly deviated STJA?

    Regards,

    Stanley
     
  16. deco

    deco Active Member

    Stanley,

    In the cases above -underlying neurological everter weakness has resulted in pictured foot/ankle position with resulting LDSTJ axis position when weightbearing.


    Regards

    Declan
     
    Last edited by a moderator: May 7, 2008
  17. Stanley

    Stanley Well-Known Member

    Declan,

    So the muscle weakness causes the change in the position of the axis?:confused:

    Regards,

    Stanley
     
  18. efuller

    efuller MVP

    Axis movement with STJ movement:
    The axis is determined by the articular facets of the joint. So, when there is internal and external rotation of the talus (with STJ motion) the position of the axis will rotate in the transverse plane as much as the talus rotates in the transverse plane. The question remains is whether we can change the position of the jonit (and the axis) to significantly alter foot function. It may be possible for some feet and not others.

    Cheers,

    Eric
     
  19. Stanley

    Stanley Well-Known Member

    Thanks Eric for your reply. You have a way to explain this complex stuff if I ask enough questions.
    I am a little more confused. If we were to use a wheel and an axle (to simplify it for me) then the spinning of the wheel around the axis would result in the axis moving? I remember this is called precession. Are you suggesting that the subtalar joint has precession?

    Does this also apply to the MTJ?:confused:

    Regards,

    Stanley
     
  20. deco

    deco Active Member

    Hi Stanley,

    Take a look at this article Chris Nester wrote regarding the MTJ with reference to MTJ axis. He has published more recent research but this is the only paper I have and it is a good starting point to looking at the mechanics of the MTJ

    Regards

    Declan
     

    Attached Files:

  21. efuller

    efuller MVP

    Have you seen Inman's pictures of the wires and the top of the talus. It's demonstrating how the different sizes of either side of the trochelar surface can create an axis of motion. It's the axis of a cone and the joint surfaces are not part of a cylandar, but a part of a cone.

    The joints of the STJ are similar in their being part of the shape of a cone. Cahil wrote a paper explaining this many years ago.

    I can't make the analogy of the wheel and axel work.


    No it does not apply to the MTJ, because you can conceptualize the MTJ as a planar joint with an infiinte number of axes.

    Remember, the motion determines the axis, the axis does not determine the motion. In other words, a joint axis is an easy way to describe the motion that is seen.

    Regards,

    Eric
     
  22. Stanley

    Stanley Well-Known Member

    Declan,

    I heard Chris Nester’s lecture at the PFOLA meeting in Miami several years ago.
    So correct me if I am wrong trying to put together what you are saying.
    Do you agree with Chris Nester that the motion determines the axis, and since the muscles change the motion, the STJ axis is changed to a more lateral position?
    To me, it seems that in CMT, there is a muscle weakness, so the foot is in an inverted position.

    Regards,

    Stanley
     
  23. Stanley

    Stanley Well-Known Member

    Eric,

    Can you give me the reference for Inman’s discussion about the axis of a cone, and Cahil’s paper?

    Thanks,

    Stanley
     
  24. kevin miller

    kevin miller Active Member

    Hello all,

    I find myself in the very position of understanding and agreeing with parts of every post on this topic. Obviously it is a hot one. It

    I do have some unpublished research with gauges. The results were very intriguing but I did not think it rigorous enough to submit for publication. I am currently trying to group and Infinity series of of EMG receptors with a Tekscan machine in order to better test the function of these mechanoreceptors. And I do think these are mechanoreceptors as Kevin Kirby said, they function as Bruce Williams and Stanley said, and semantically are described more like Craig Payne’s description. But to add fuel to the fire, it is not just one set of mechanoreceptors that will be affected by a joint manipulation, it will occur in every muscle crosses the joint. Further, the output ratios of each muscle will alter. Meaning that the sums of the output of each muscle equals the sum of the force available at the joint and while the sum may change very little -- or might change quite a bit -- force produced by each muscle changes dramatically. What difference does this make? If the ratios are not normal, one segment of the total muscle group may overwork and become damaged; a simple overuse syndrome that may lead to outright injury.

    Regards, Kevin M.
     
  25. deco

    deco Active Member

    Hi Stanley

    As Eric has previously mentioned "The axis is determined by the articular facets of the joint" Other factors which may influence the axis may include muscle: weakness, tightness, spasticity etc.

    In the CMT illustration the muscle weakness has resulted in the inverted foot position which has positioned the STJ axis in a lateraly deviated position.

    Regards

    Declan
     
  26. Stanley

    Stanley Well-Known Member

    I am just trying to follow this reasoning. Correct me where I am in error: the facets determine the axis, and the muscles can influence the axis. The facets are a constant, and the muscles are a variable, and the axis is a dependent variable. Therefore, the best thing to treat would be the muscles.
    To expand on this, if the orthoses are used to treat the foot based on the axis location, and if the muscles are a variable, and the axis can vary accordingly, then with a variable axis, how can your orthoses be made properly basing it on the axis location? :confused::craig:

    It would seem that we would first want to correct the muscles (which happens to be the gist of this thread).:cool:

    Regards,

    Stanley
     
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