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Subtalar joint axis palpation

Discussion in 'Biomechanics, Sports and Foot orthoses' started by davsur08, May 26, 2011.

  1. davsur08

    davsur08 Active Member


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    Dear Colleagues,

    This has been bugging me for some time. I hope someone would through some light on this.

    I had a patient with anterior tibial tendonopathy. The subtalar joint axis, when i marked on her foot was slightly lateral deviated. but, when i watched her walk the heel begins to pronate and the forefoot abducted. ive tried marking the axis again, the markings showed a lateral deviated axis. am i doing something wrong here?

    also, in some cases especially in pts with severe pronation, the Subtalar joint axis is palpated at the lateral aspect of the plantar heel and as it progresses in to the forefoot passes medial to the first metatarsal head. "Does this mean that the forefoot in this case has a greater magnitude of pronation than the rearfoot"? or a partially compensated or fully compensated rearfoot varus?

    Much appreciate your response
    regards
    david
     
  2. The non-weightbearing axial position is not necessarily the same as the weightbearing axial position. Moreover, the axis will change position with time during gait as the subtalar joint moves.
     
  3. davsur08

    davsur08 Active Member

    Dr.Spooner,
    if the axis changes with phase of gait, then what is the clinical significance of marking such axis? Most reasoning of biomechanical pathology is explained around the axis location. are you saying what we mark on the foot is not the same axis as during gait?

    david
     




  4. As a rule ie generally a more medial Subtalar joint axis location found using the palpation method will be more medial during gait. As a Rule there will be exceptions to the rule , generally from muscle activation or spasm.
     
    Last edited by a moderator: Sep 22, 2016
  5. Absolutely. The non-weightbearing technique gives a reasonable approximation of the non-weghtbearing position of the axis. On weightbearing, this position will generally change. As the subtalar joint pronates and supinates during gait so the axial position will change. The fact that the axis changes position doesn't change the reasoning behind the biomechanical pathological theories. It just adds a level of complexity in that we need to know the axial position as a function of time.

    Take a look at figure 4 of this paper: http://www.podologiaalicante.com/articulos/kirby/The Subtalar Joint Axis Locator.pdf
     
  6. efuller

    efuller MVP

    There is more than one cause of pronation. You can have a pronation moment caused by the center of pressure of ground reaction force being medial to the STJ axis. Another kind of "pronator" is from the pronation moment from the peroneal muscles. Often, in feet with a laterally deviated STJ axis, the resting position of the STJ will be not maximally pronated. In gait, the STJ may reach equilibrium before it reaches the end of range of motion of the STJ. As gait progresses, there will be increased tension in the Achilles tendon. In a foot with a lateral axis this will create a supination moment at the STJ. If there were no peroneal activity then there would probably be an unopposed supination moment and the person would sprain their ankle in propulsion. To prevent this, there is increased peroneal activity in these people (more prone to peroneal tendonitis) and because of the moment from the muscle you will see STJ pronation in late stance or early propulsion.


    STJ axis position and partially compensated varus are two totally different things that may have some interrelations. When the varus is not fully compensated, that is the STJ does not pronate far enough to fully load the medial forefoot, there will tend to be a lateral location of the center of pressure. A lateral location of center of pressure will tend to cause a high pronation moment regardless of STJ axis position.

    The moment from ground reaction force is determined by the location of the center of pressure of ground reaction force relative to the STJ axis. So, with the axis relatively lateral on the heel and relatively medial to the forefoot you will have two things that have to be added together to get the net moment acting on the joint. You also have to have consider Achilles tendon activation that occurs in gait. As the Achilles contracts, it will shift the center of pressure forward. So, as the heel lifts in gait you will get the center of pressure to move anteriorly, so the effect of the forefoot becomes more important.

    I have that foot. It feels real good to have a varus heel wedge. But too much wedge and I can get peroneal fatigue that is noticible at heel contact, but feels good in stance.

    Eric
     
  7. David:

    The subtalar joint (STJ) palpation technique, which I first described within the literature 24 years ago (Kirby KA: Methods for determination of positional variations in the subtalar joint axis. JAPMA, 77: 228-234, 1987), is not without its problems. Even though, in the skilled examiner's hands, this technique will allow the examiner to very closely estimate the representation of the STJ axis on the plantar foot while the subject is non-weightbearing, once the subject then becomes weightbearing, the STJ rotational position may change from the non-weightbearing position. (See illustration of technique below.)

    For example, let's say you determine a patient's plantar STJ axis location via palpation with the STJ positioned 4 degrees from the maximally pronated position. However, when now standing, the patient's foot is maximally pronated (i.e. the patient's foot has pronated 4 degrees from the position that the STJ axis was palpated). As a result, the STJ axis spatial location will be markedly more medially translated and internally rotated compared to the STJ axis location when you first determined the STJ axis location while non-weightbearing.

    It is for this reason that now I more commonly assess the STJ axis spatial location while the patient is in relaxed bipedal stance, since this technique, I believe, more accurately reflects the STJ axis spatial location during weightbearing activities.

    Hope this helps.
     

    Attached Files:

  8. markjohconley

    markjohconley Well-Known Member

    Kevin I try never to miss any of your (or there's a few others) posts but I must have missed one, as I read this as you assessing whilst pt is weightbearing????, thanks, mark
     
  9. To assess the STJ axis spatial location while weightbearing, I visually estimate the line between the superior-lateral quadrant of the posterior calcaneus (i.e. posterior STJ axis exit point) and the central aspect of the dorsal neck of the talus (i.e. anterior STJ axis exit point) during relaxed bipedal stance. This estimation technique closely approximates the spatial location of the STJ axis during weigtbearing. I will be demonstrating this technique at the Biomechanics Summer School in Manchester in about 4 weeks.
     
  10. Here I am demonstrating how to locate the subtalar joint axis spatial location during a weightbearing examination in a lecture/workshop I did in Madrid in February 2011.

    The marks are placed on the superior-lateral quadrant of the posterior calcaneus and bisection of the dorsal talar neck, and then the pen is used to demonstrate how aligning along a line connecting these exit points of the STJ axis gives an estimation of the STJ axis spatial location.
     

    Attached Files:

  11. drsha

    drsha Banned

    ????????
    Is this your EBM way of saying that you have no idea what you are saying or do you have evidence to explain this snake oil?

    Dr Sha
     
  12. drsha

    drsha Banned

    Kevin, you look pretty serious and convincing taking an ESTIMATION of the STJ Axis Spacial Location.
    However, your description relies on locating points on the superior-lateral quadrant of the posterior calcaneus with accuracy?, bisecting the talar neck with accuracy? and finding the exit points of the STJ axis with accuracy which I don;t think you have proven you can do? Are these measurements and markings evidenced or just something you made up?
    Your random marks, connecting lines and a pen demonstrating an estimation of an axis that predicts its spatial location. Are these common terms or terms that are evidenced in the literature or just those that you made up?

    Are you a flim flam man or a scientist>
    Am I and others supposed to be able to reproduce with accuracy and small error rate what you are doing in Spain, in February 2011?
    I tried three times and failed miserably.

    Is this STJ Axis Spacial Location evidenced as accurate, reproducible and validated by anything more than your own beliefs?
    Do you have a STJ Axis Spacial Locator to go with your STJ Axis Locator as a set?
    Do you have a package with your three books as a giant set?
    Were you a paid performer in Madrid, expenses, flight, hotels ?

    In contrast, the study:

    Position of the subtalar joint axis and resistance of the rearfoot to supination.
    Payne C, Munteanu S, Miller K.

    Department of Podiatry, School of Human Biosciences, La Trobe University, Victoria, Australia.

    Abstract
    Determination of the position of the subtalar joint axis is being more widely used clinically to facilitate the prescription of foot orthoses and the understanding of foot function, but clinical determination of the axis has not been widely investigated. The aim of this study was to determine the relationship between clinical determination of the subtalar joint axis and the amount of force needed to supinate the foot. The transverse plane position of the subtalar joint axis was determined in 47 subjects. The sagittal plane orientation of the subtalar joint axis was determined using the relative amounts of forefoot adduction and abduction obtained when the rearfoot was supinated and pronated. The amount of force needed to supinate the foot was measured using a device designed to measure resistance to supination. The only two parameters that were correlated to supination resistance of the rearfoot were body weight (r = 0.52) and the perpendicular distance from the fifth metatarsal head to the subtalar joint axis (r = 0.59). The model on which determination of the subtalar joint axis is based may not be valid, but it might help determine how much force is needed to supinate a foot using foot orthoses.

    states that Subtalar Joint Axisl may not be valid.
    Comments, Dr Payne?

    For me, the subtalar joint axis as an indicator of biomechanical importance clinically and its use as a tool for education has no basis in science and therefore the subtalar joint axis spacial locatoion is a red herring like much of your work.

    "It takes one to know one and vice versa"
    Alfred E. Newman

    Dr Sha
     
  13. Look at any of the bone pin studies which have calculated instant centres of rotation of the subtalar joint, Dennis. The axis moves as the joint moves. Earlier this week you had a pop and Craig and Kevin, now you're trying your luck with me. You are a funny little man Dennis. As I've told you before I have no desire to discuss anything with you on this forum ever, Dennis.
     
  14. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    It was a while since we did that work and I do not have it in front of me, but I pretty sure that is not what we said in those exact words or is what we meant. What we were commenting on was the use of the term "subtalar joint axis" and what we were probably palpating would have been some small movement in the ankle and midtarsal joints, with the vast majority happening in the STJ .... so it was probably more appropriate to call it "a rearfoot axis". Regardless of the use of the terminology of "a rearfoot axis" or "subtatlar joint axis", the principles were still the same and the correlations in the study were still the same.
     
  15. Not only a funny little man, but rather a sad one also. He is obviously jealous of all the attention that we are all getting and of how little attention anyone is paying to his pet ideas. I also have no desire to discuss anything with Dennis.......ever!
     
  16. drsha

    drsha Banned

    I got my quote from the internet, the same source you use to deride my work. I offered you partnership to what I was doing six years ago and you never sought my assistance in understanding Wellness Biomechanics.
    Are you saying that movement of the ankle and midtarsal joints would obscure measuring the STJ differently foot to foot making STJ Axis measurement invalid?
    So you call it a rearfoot axis (what about ankle and MTJ Axis) and does that infer that the STJ Axis is a misnomer and inappropriate as Dr, Kirby has Christened it?

    Why don't you take the time to review your work and what appears about it on the internet and post additional comments..

    Are you saying that what you meant was quoted inaccurately and biased and derided because of the agenda of those opposing your agenda.
    You wouldn't do that to any one else as a pure researcher and educator with no profit motive or bias would you.

    Finally does the disclaimer at the bottom of your posts insinuate that La Trobe is not responsible for the comments or opinions on this site reflect the fact that they are not profiting by the ads from Google, podiatry.com and the many others that feed the twins and your lifestyle mean that you are no different than me?

    "It takes one to know one....and vica versa"
    Alfred E. Newman

    Dr Sha
     
  17. drsha

    drsha Banned

    Originally Posted by Simon Spooner View Post
    Absolutely. The non-weightbearing technique gives a reasonable approximation of the non-weghtbearing position of the axis. On weightbearing, this position will generally change. As the subtalar joint pronates and supinates during gait so the axial position will change. The fact that the axis changes position doesn't change the reasoning behind the biomechanical pathological theories. It just adds a level of complexity in that we need to know the axial position as a function of time.

    Simon, no one is arguing with your foundation evidence that "the STJ Axis moves as the joint moves. But your next leap is totally biased and personally profitable and has absolutely no evidence.

    Your statement that "The non-weightbearing technique gives a reasonable approximation of the non-weghtbearing position of the axis. On weightbearing, this position will generally change. As the subtalar joint pronates and supinates during gait so the axial position will change. The fact that the axis changes position doesn't change the reasoning behind the biomechanical pathological theories. It just adds a level of complexity in that we need to know the axial position as a function of time".

    This is a leap that has nothing to do with evidence, accuracy and reproducibility as relates to biomechanics.

    Your quote is based on Spooner opinion, anecdote and supposition unless you have evidence to the contrary.
    and
    you are the inventor/co-inventor of The Subtalar Joint Axis Locator with Kevin Kirby of which there are two and you are involved in their potential profit if they were ever manufactured and if they were ever marketed and if someone actually wanted to use one, isn't that correct?

    What you are saying is like me saying that only a fool would argue from a foundation that all feet are different and that profiling them into subgroups would be a sensible platform from which to evaluate and treat feet from and then tried to sell you an anecdotal, unproven, personally profitable paradigm called functional foot typing.

    It takes one to know one...... and vica versa.
    Alfred E. Newman

    Dr Sha
     
  18. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    Nope. It was just quoted out of context.
    Nope. The disclaimer simply means that the comments I make here are mine and mine alone and not the "official" view of my employer. Nothing sinister in that.

    As for the money this site makes .. I have never made a secret of that - the Google ads bring in $150-$250/month; the affiliate adverts down the right (eg Amazon) on a good month bring in $20; the Buy Admin a beer makes a few dollars; eBay paid me $2.68 last month; occasionally I sell an advert that might appear down the right for $300 for a few months. Take off that the cost of the vBulletin software and annual upgrades; the most recent design change cost $750; the hosting costs (it has to be a dedicated server and not a shared one due to the volume of traffic) - $170/month; we have a few paid subscriptions services to alert us re news; I pay for some adverts on Google and Facebook; lawyers aren't cheap and have had to engage them 3 times in the last 4 yrs to make **** go away. That does not take into account the time I spend doing Admin stuff in the background (see: a day in the life of a forum admin) and helpers I have who are unpaid. ..... so you can see I am laughing all the way to the bank.

    This is a hobby, not a business. It has grown into the most visited podiatry site on the web by a substantial margin, but that does not mean that its a cash cow.

    If anyone wants to buy an advert, send me a message.
     
  19. markjohconley

    markjohconley Well-Known Member

    Thanks, again, Prof. Kirby.
     
  20. Hey Craig:

    I want to buy an ad for my new trademarked and patented Hyper-Functional Foot Classification System TM which has 25 categories of Foot Classes TM, soooooo much better than any system that only uses 16 "Foot Types", which, by the way, is a blatant rip-off of the original foot typing system first described by Drs. Paul Scherer and Jack Morris (Scherer PR, Morris JL. The Classification of Human Foot Types, Abnormal Foot Function, and Pathology. In: Valmassy RL. Clinical Biomechanics of the Lower Extremities. St. Louis: Mosby; 1996. p. 85-93).

    We use devices called Foot HyperLevelers TM that are designed specifically for each of the 25 Foot Classes TM. For only $94.00, my HyperFoot Strengthener Lab TM can make a pair of foot orthoses which are much better than any orthotic lab that only uses the imaginary and unoriginal 16 "Foot Types" in its classification system. This is all part of my HyperHealthy Biomechanics TM approach that should allow me to finally make a name for myself in my old age so I can retire early.:rolleyes:
     
  21. davsur08

    davsur08 Active Member

    Dr. Spooner, Dr. Fuller, Prof. Kirby THANK YOU all for the explanation. Ive few doubts and would appreciate your time.

    As the subtalar joint pronates and supinates during gait so the axial position will change.

    aren't supination or pronation moments occur around an axis?

    If the non-weight bearing subtalar joint axis changes its location during gait, then there had to be other forces acting. Is this other forces, muscular forces? If it is then, is it fair to say that changes in subtalar joint axis during gait is the sum of joint range of motion, muscle strength and ground reaction forces?

    Is orthotic intervention directed to minimise the excursion of the subtalar joint axis during gait? For example a patient with anterior tibial tendonopathy who has a lateral heel strike and continues to pronate all the way to toe-off. This Pt has his subtalar joint axis laterally deviated during heel strike and medially deviated at toe off, right? So, the tibialis anterior being lateral to the subtalar joint aids to supinate the foot at heel strike and during toe off may contribute to pronation assuming it lies medial to subtalar joint axis. Do we say the tib. anterior pathology in this case is due to the strain of adapting to different foot postures? If so, would the intervention aim at reducing the axis excursion.

    I ask this because, as the subtalar joint axis changes its position during gait (a resultant foot pathology is explained on the basis of subtalar joint location as it influences moments and forces across the foot), is orthotic therapy aims to minimise the axis excursion?

    I Fail to comprehend the concept as to why the subtalar joint axis location which is a variable measure during gait (either weight bearing or non-weight bearing) is essential to understand a pathology, unless the magnitude of the change in axis position is vital to create or treat a pathology.

    Thank you and greatly appreciate

    Regards
    David
     
  22. davsur08

    davsur08 Active Member

    Dr. Fuller. THANK YOU.

    As the achilles tendon activation is causing COP shift anteriorly, why would not a heel lift be effective? I would imagine a varus rearfoot wedge would shift the axis more laterally in the heel? or have i missed the point?

    Many thanks

    regards

    David
     
  23. David:

    As the subtalar joint (STJ) pronates and supinates (i.e. undergoes rotational motion) in any weightbearing situation, including walking and running gait, the STJ axis spatial location will also change by translating and/or rotating relative to the plantar foot. These STJ rotational motions (i.e. pronation/supination) occur as a result of angular accelerations across the STJ axis which, in turn, are caused by the sum total of all the internal and external STJ pronation and supination moment acting across the STJ axis at any instant in time.

    Foot orthosis therapy shouldn't primarily be directed toward "limiting STJ axis excursion" but should, rather, be primarily directed toward decreasing the pathological stresses that are causing the patient's foot and lower extremity tissue injury in the first place. For example, in a patient with anterior tibial tendinopathy, I would be more concerned at reducing the tensile stress within the anterior tibial tendon than changing the excursion of the STJ axis. If, however, the foot had a significantly medially deviated STJ axis, then I would aim to try to supinate the foot by increasing the external STJ supination moments with the orthosis to bring the STJ axis to a more normal position which, in turn, should help reduce the anterior tibial tendon tensile force and improve the patient's symptoms.

    Understanding the principles of STJ axis location and rotational equilibrium does not solve all the problems for the clinician seeing patients with foot and lower extremity biomechanical pathology. However, it does provide a firm basis for understanding how altering the forces across the STJ axis with foot orthoses or other therapeutic measures may help relieve the abnormal tissue stresses that cause the pathologies that are present within the feet and lower extremities of our patients in our clinics.

    David, please write to me privately at kevinakirby@comcast.net and I will give you the password to my website where you can download the papers that I and others have written on these subjects that may help you further in your understanding of these important concepts.

    References:

    Van Langelaan EJ: A kinematical analysis of the tarsal joints: An x-ray photogrammetric study. Acta Orthop. Scand., 54:Suppl. 204, 135-229, 1983.

    Benink, RJ: The constraint mechanism of the human tarsus. Acta Orthop Scand, 56: (Suppl) 215, 1985.

    Kirby KA: Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Inc., Payson, Arizona, 1997.

    Kirby KA: Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002. Precision Intricast, Inc., Payson, AZ, 2002.

    Kirby KA: Foot and Lower Extremity Biomechanics III: Precision Intricast Newsletters, 2002-2008. Precision Intricast, Inc., Payson, AZ, 2009.

    Kirby KA: Methods for determination of positional variations in the subtalar joint axis. JAPMA, 77: 228-234, 1987.

    Kirby KA: Rotational equilibrium across the subtalar joint axis. JAPMA, 79: 1-14, 1989.

    Kirby KA, Green DR: Evaluation and Nonoperative Management of Pes Valgus, pp. 295-327, in DeValentine, S.(ed), Foot and Ankle Disorders in Children. Churchill-Livingstone, New York, 1992.

    Kirby KA: The medial heel skive technique: improving pronation control in foot orthoses. JAPMA, 82: 177-188, 1992.

    Kirby KA.: Biomechanics and the treatment of flexible flatfoot deformity in children. PBG Focus, J. Podiatric Biomechanics Group, 7:10-11, 1999.

    Kirby KA: Biomechanics of the normal and abnormal foot. JAPMA, 90:30-34, 2000.

    Kirby KA: Conservative treatment of posterior tibial dysfunction. Podiatry Management, 19:73-82, 2000.

    Kirby KA: Subtalar joint axis location and rotational equilibrium theory of foot function. JAPMA, 91:465-488, 2001.

    Kirby KA.: What future direction should podiatric biomechanics take? Clinics in Podiatric Medicine and Surgery, 18 (4):719-723, 2001.

    Kirby KA: Foot orthoses: therapeutic efficacy, theory and research evidence for their biomechanical effect. Foot Ankle Quarterly, 18(2):49-57, 2006.

    Kirby KA: Emerging concepts in podiatric biomechanics. Podiatry Today. 19:(12)36-48, 2006.

    Kirby KA: "Evolution of Foot Orthoses in Sports", in Werd MB and Knight EL (eds), Athletic Footwear and Orthoses in Sports Medicine. Springer, New York, 2010.

    Kirby KA: Introduction to Recent Advances in Orthotic Therapy. In Scherer PR (ed), Recent Advances in Orthotic Therapy: Improving Clinical Outcomes with a Pathology Specific Approach, Lower Extremity Review, USA, 2011.

    Fuller EA: Center of pressure and its theoretical relationship to foot pathology. JAPMA, 89 (6):278-291, 1999.

    Spooner SK, Kirby KA: The subtalar joint axis locator: A preliminary report. JAPMA, 96:212-219, 2006.

    Payne C, Munteaunu S, Miller K: Position of the subtalar joint axis and resistance of the rearfoot to supination. JAPMA, 93(2):131-135, 2003.

    Pascual Huerta J, Ropa Moreno JM, Kirby KA: Static response of maximally pronated and nonmaximally pronated feet to frontal plane wedging of foot orthoses. JAPMA, 99:13-19, 2009.

    Pascual Huerta J, Ropa Moreno JM, Kirby KA, Garcia Carmona FJ, Orejana Garcia AM: Effect of 7-degree rearfoot varus and valgus wedging on rearfoot kinematics and kinetics during the stance phase of walking. JAPMA, 99(5):415-421, 2009.

    Piazza SJ: Mechanics of the subtalar joint and its function during walking. Foot Ankle Clin N Am, 10:425-442, 2005.

    Lewis GS, Kirby KA, Piazza SJ: A motion-based method for location of the subtalar joint axis assessed in cadaver specimens. Presented at 10th Anniversary Meeting of Gait and Clinical Movement Analysis Society in Portland, Oregon. April 7, 2005.

    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.

    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. J Biomechanics, 42:146-151, 2009.
     
  24. efuller

    efuller MVP

    Generally, you want to use the Achilles tendon during gait to cause propulsion of the trailing limb so that it can become the leading limb. You are going to tend to use the gastroc and soleus muscles whether or not you are on a heel lift. You could make the heel lift so high that there is no additional shortening of the muscle available, but this is probably not going to be comfortable or stable. Although some women do wear some very high heels.

    When you stand on a varus heel wedge, you often do not see a change in position of the joint. If the wedge did cause supination of the joint, then there would be a lateral shift in the position of the STJ axis relative to the ground because of the external rotation of the leg. However, you rarely see more than a couple of degrees of motion with a wedge. If you did see a couple of degrees of motion, you could assume a couple of degrees of movement of the axis. So, not very much motion.

    Eric
     
  25. efuller

    efuller MVP

    The moment from the ground about the STJ axis at any particular instant in time will be related to the distance the center of pressure is at that in point in time from the location of the axis at that point in time. So, the moment from the ground will change over time. More on an individual's axis below.

    It's not really a sum. The location of the STJ axis is determined by the articular surfaces of the talus and calcaneus. So, if the talus externally rotates the location of the STJ axis will rotate. When the foot is in contact with the ground and the STJ pronates there will be internal rotation of the talus. It's not really a sum, it's where the bones are when you want to find the location of the axis.



    As others have said, the intervention is directed at reducing stress on the injured structure. In your example of the anterior tibial tendon, the tendon creates a dorsiflexion moment at the ankle joint. It has very little leverage at the STJ and therefore is probably not used much in response to high pronation moments. The anterior tibial tendon is used most just after heel contact to slow plantar flexion of the ankle to prevent the foot from slapping. A shoe with a posterior flare will increase the plantar flexion moment from the ground so the Anterior tibial tendon would have to work harder to slow plantar flexion.

    It is nearly impossible to limit axis excursion of the STJ significantly. If the STJ moves 4 degrees in gait then if there is 4 degrees of talar adduction with that 4 degrees of motion then the axis will rotate about 4 degrees during gait. That said there are not many treatments that have been shown to actually limit the amount of STJ pronation. I've looked at a lot of heels on top of orthotics and I haven't seen many that change the position of the heel more than a couple of degrees. Particularly in feet where you want to change the axis position the most are usually the hardest to get a change in STJ axis position.


    Take two identical feet except one has a more medially positioned STJ axis than the other. In gait, at heel contact, they will hit about the same position. The one with the more medially positioned STJ axis will have a greater pronation moment than the other one. They will both go through STJ pronation after heel contact until forefoot loading. So, if they have a pronation range of motion of the same amount, their axes will move the same amount and the one with the medially deviated STJ axis will always be more medially deviated than the other one. The medially deviated STJ axis will always have a higher pronation moment from ground reaction force than the other. So, the medially positioned axis foot will have more stress on the anatomical structures that resist pronation. Also, it will be harder to resupinate this foot later in gait, so it is more likely that its axis will stay more medially deviated than an average axis foot. This is why comparing the relative position of the STJ axis across feet can help predict and explain why certain feet are more prone certain pathologies.

    Eric
     
  26. davsur08

    davsur08 Active Member

    Thank you Dr.Fuller, This has been helpful.
     
  27. davsur08

    davsur08 Active Member

    Dr.Fuller, am still having difficulty understanding this. as the rearfoot is in a varus position and the medial aspect of the forefoot in an attempt to make ground contact pronates assisted by achilles tendon, isn't the varus rearfoot the cause of 1. the forward progression of COP, 2. achilles tendon firing early to allow medial Forefoot contact? How would a rearfoot varus post reduce stress on structures that promote supination? would not a forefoot valgus post promote effective medial forefoot contact?

    You are going to tend to use the gastroc and soleus muscles whether or not you are on a heel lift.

    A heel lift would reduce the stress on achilles tendon. early heel lift during gait can lead to increased pronation during propulsion right? i suppose in this case as the varus heel is the cause of the forefoot pronation is it not prudent to address that as means of treatment?

    may be am wrong. i have to do more reading.

    Thanks again

    regards

    David
     
  28. 1. The angle of the rearfoot does not cause forward progression of the center of pressure (CoP), the body's response to the center of mass (CoM) of the body moving forward relative to the foot during gait causes the forward progression of the CoP.

    2. The Achilles tendon does not "fire", it is a tendon, not a muscle.

    3. A varus rearfoot wedge increases the external subtalar joint (STJ) supination moment. If the individual had been using the posterior tibial (PT) muscle to increase the internal STJ supination moment to prevent STJ pronation during relaxed bipedal stance and then a varus rearfoot wedge was added under the foot, a likely response by the individual would be to reduce the contractile activity to the PT muscle since now the varus rearfoot wedge was effectively "doing the same job" as the PT muscle. In this way, a varus rearfoot wedge may reduce the stress on an internal structure that increases the STJ supination moment.

    4. A valgus forefoot wedge increases the external STJ pronation moment. If the STJ does not pronate in response to the valgus forefoot wedge, then there will be an increase in ground reaction force (GRF) plantar to the lateral metatarsal heads, and a decrease in GRF on the medial metatarsal heads. The only way that a valgus forefoot wedge will increase the GRF plantar to the medial metatarsal heads is if the valgus forefoot wedge causes STJ pronation motion that is effectively larger than the amount of valgus forefoot wedge...and this may or not be the case depending on the internal forces/moments acting within the foot when the wedge is applied to the forefoot.

    No. An increase in tensile force within the Achilles tendon may cause increased STJ pronation moment only if there is also a medially deviated STJ axis. An increase in tensile force within the Achilles tendon will cause increased STJ supination moment if there is a normal to laterally deviated STJ axis. Most commonly, an early heel off is associated with earlier STJ supination during the stance phase of gait since contractile activity of the gastrocnemius and soleus muscles produce an internal STJ supination moment in most feet.
     
  29. efuller

    efuller MVP

    David, You may be confusing cause and effect.. It's helpful to clarify the situation by comparing one case with another. For example, you could compare the foot in static stance with no modifications with the foot in static stance with a modification like a varus heel wedge. The varus heel wedge will decrease the pronation moment from the ground when compared with no wedge. When the foot is on the wedge, you may see no change in position of the STJ compared to barefoot, even though the moment from ground reaction force has changed.

    The Achilles tendon is interesting in that it crosses both the ankle and subtalar joints. When there is tension in the tendon it will simultaneously create a moment at both joints. It has a much longer lever arm at the ankle joint and a much smaller lever arm about the STJ. In most feet, tension in the Achilles tendon will directly create a supination moment at the STJ. However, at the same time the tension in the tendon is creating a plantarflexion moment at the ankle joint. This plantar flexion moment at the ankle will shift the center of pressure anteriorly. Since the STJ axis is usually angle to the foot, an anterior shift in the center of pressure will tend to also move it to a position more lateral to the STJ axis and this will create a pronation moment. So, tension in the Achilles tendon is simultaneously creating a direct supination moment because its attachment is medial to the aixs and it is creating a pronation moment, in most feet, because it is causing an anterior shift in the center of pressure. When you add the moments together you get a net moment and most of the time you will get a net pronation moment. In a laterally positioned axis foot the anterior shift in center of pressrue will have a smaller change in its distance relative to the STJ axis, so you could get a net supination moment in this particular foot type.



    To illustrate the quote of mine in itialics above a slightly different way. Stand on the floor and try and reach something on a high shelf. If you can't reach it initially, you will plantarflex your ankle to lift your body higher. Now try and reach the same object while standing on a heel lift. At the instant the ankle is plantar flexed to the point where the heel is no longer in contact with the lift, there will be no difference in tension in the tendon, in that particular foot position, than when the foot was not standing on the heel lift. The same thing also happens in gait. As the body moves over the foot, at some point the person will use their Achilles tendon to place force on the forefoot. This point may come later in gait when a heel lift is used, but the tendon will still have tension in it.

    I agree with Kevin's comments

    Eric
     
  30. stevewells

    stevewells Active Member

    who is this W*****?
     
  31. davsur08

    davsur08 Active Member

    Prof. Kirby and Dr. Fuller,
    Thank you very much for the explanation.
    achilles tendon firing early to allow medial Forefoot contact?
    apologise for the bad use of terminology. i'l be careful next time.

    Thank you again. It takes a great depth of understanding to grasp the concept. I havent acquired that understanding yet, its something am working towards.

    Greatly appreciate

    Kind regards


    David
     
  32. Perthpod

    Perthpod Active Member

    Thanks for having such an awesome hobby Craig!!
     
  33. Keith01

    Keith01 Welcome New Poster

    Dear Colleagues,

    This is my first time Podiatry Arena also my first thread.
    I have been using the Talar Head palpation method as outlined in Foot Posture Index for STJN and have found this extension to the method on youtube has anybody heard of this technique?



    feedback would be appreciated. Keith
     
    Last edited by a moderator: Sep 22, 2016
  34. Griff

    Griff Moderator

    Hi Keith,

    Welcome to the arena.

    Always worth remembering that the palpatory method of identifying 'neutral' does not have particularly high reliability (not to mention how poor the reliability of drawing lines on skin with a sharpie must surely also be). Not to let that put you off doing so if you find it useful to of course - but it all depends on what you will use this information for.

    Ian
     
  35. RobinP

    RobinP Well-Known Member

    HI Keith,

    What does sub talar neutral tell you?

    Here is some reading that Mike Weber linked to in another thread. linky

    It has a huge amount of information but the main thing is that a lot of the information contained within these threads questions the validity and applicability of the measurement.

    On a personal level, I give it no more than a fleeting glance and only remark upon it if it is grossly atypical(based on my limited experience)


    Hope it helps

    Robin
     
  36. DaVinci

    DaVinci Well-Known Member

    Agreed. Subtalar joint neutral is something I hardly ever bother paying much attention to these days.
     
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