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Subtalar joint neutral approach to mechanical foot therapy

Discussion in 'Biomechanics, Sports and Foot orthoses' started by admin, Jan 5, 2006.

  1. admin

    admin Administrator Staff Member


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    I am grateful to Kevin Kirby and Precision Intricast for permission to reproduce this January 2002 Newsletter (you can buy the 2 books of newsletters off Precision Intricast):

    SUBTALAR JOINT NEUTRAL APPROACH TO MECHANICAL FOOT THERAPY

    Podiatric biomechanics is a field that is devoted to developing increased knowledge of the complex mechanical interactions of the foot and lower extremity. The potential benefit of an in-depth knowledge of podiatric biomechanics is that it allows the podiatrist to more effectively treat pathology and injuries of the foot and lower extremity that are caused by abnormal forces or abnormal motions of the foot and lower extremity during weightbearing activities. Whether the podiatrist can effectively utilize their knowledge of podiatric biomechanics to successfully treat injuries of the foot and lower extremity is largely dependent on the theoretical framework upon which their knowledge is based and the therapeutic approach that they take in making treatment decisions.

    For the past thirty years, podiatric biomechanics theory has been based on the idea that there is an ideal structure of the foot and lower extremity that tends to allow the most normal function of the foot and lower extremity during weightbearing activities. Traditional podiatric biomechanics theory was proposed and developed by Merton Root, DPM and coworkers at the California College of Podiatric Medicine (CCPM). The traditional biomechanics theory of Root and coworkers was based on the idea that there are eight “Biophysical Criteria for Normalcy” which the foot and lower extremity should possess in order to be considered “normal” (Root, M.L., W.P. Orien, J.H. Weed and R.J. Hughes: Biomechanical Examination of the Foot, Volume 1. Clinical Biomechanics Corporation, Los Angeles, 1971). For example, if an individual does not have a vertical tibia and a vertical calcaneus in relaxed bipedal stance, then this individual would be considered to have “deformities” or an “abnormal” foot and lower extremity and would be expected to have increased likelihood of injury versus an individual that had a “normal” foot and lower extremity with no “deformities”. This thirty-year-old theory of foot function will be called, in this discussion, the Subtalar Joint Neutral (SJN) Theory.

    The SJN Theory relied on the idea that certain structural “deformities” of the foot and lower extremity caused abnormal movements of the joints of the foot and lower extremity that resulted in non-ideal, or “abnormal compensations” to occur when the foot mechanically interacted with the ground during weightbearing activities. For example, proponents of the SJN Theory believed that a foot with a posterior calcaneus which was inverted to the ground while the subtalar joint (STJ) was in neutral position (i.e. rearfoot varus deformity) would undergo abnormal “compensatory” pronation motion during weightbearing activities until the posterior calcaneus reached the vertical position relative to the ground (Sgarlato, T.E.(ed): A Compendium of Podiatric Biomechanics. California College of Podiatric Medicine, San Francisco, March 1971, pp. 210-213).

    Therefore, in the SJN Theory, any foot that stood in relaxed bipedal stance with the STJ pronated from the neutral position was considered to be “abnormally pronated”. Any lower extremity that did not have a vertical tibia while in relaxed bipedal stance was considered to have an abnormal structural alignment of either a tibial valgum or tibial varum deformity. In addition, any foot that didn’t have a perpendicular forefoot to rearfoot relationship was considered to have an abnormal structural alignment of either a forefoot varus or a forefoot valgus deformity (Root, et al, 1971, p. 70-75).

    The basic goal of the treatment approach utilizing the theoretical framework of the SJN Theory was to restore the STJ to a rotational position that was closer to the neutral position during weightbearing activities so that improved foot function would result. One of the assumptions of the SJN Theory was that treating the foot with foot orthoses would lessen or eliminate the “abnormal compensations” of the foot and lower extremity so that improved foot function was achieved and pathology and/or injury would heal or improve.

    The therapeutic approach of foot orthosis therapy that was taught from 1979-1983 at CCPM while I was a podiatry student and from 1984-1985 while I was the CCPM Biomechanics Fellow was dependent largely on the biomechanical examination of the patient, which determined the type and degree of deformity present in the foot and lower extremity. Biomechanical examination parameters such as the bisection of the posterior calcaneus, tibial frontal plane position, location of the STJ neutral position, forefoot to rearfoot relationship, and ankle joint dorsiflexion were some of the more important parts of the decision making process used for determining the prescription variables of foot orthoses for patients with mechanically based pathology of the foot and lower extremity (Root, et al, 1971).

    During my Biomechanics Fellowship at CCPM, I began to notice that one of the major problems in the therapeutic approach to foot orthosis therapy that relied on the theoretical framework of the SJN Theory was that little regard was given to the actual anatomical site of the injury of the patient. Foot orthoses were designed primarily to “prevent compensation for deformities”. Foot orthoses were not altered significantly from the “basic recipe” depending on which specific anatomical structure of the foot and/or lower extremity was injured or involved. As an example, if a patient was measured to have a 50 forefoot valgus deformity, had no tarsal coalition, and the posterior calcaneus could evert to a vertical position in relaxed bipedal stance, the standard orthosis prescription was always the same “basic recipe” of a vertically balanced thermoplastic shell with a 40/40 rearfoot post, regardless of whether the patient had posterior tibial tendinitis, peroneal tendinitis, medial tibial stress syndrome, Morton’s neuroma, plantar fasciitis, hallux limitus, or just about any other anatomical site of pathology.

    Many proponents of the SJN Theory also believed that a “functional foot orthosis” could only be made of a relatively rigid thermoplastic material ending distally at the metatarsal neck level. The addition of forefoot extensions to the distal orthosis was also not promoted as a method to increase the functionality or effectiveness of the foot orthosis since it was thought that adding such “padding” materials under the metatarsal heads may decrease the ability of the metatarsophalangeal joints to plantarflex during propulsion (Merton Root, DPM, Root Orthotic Laboratory Seminar, February 1987).
    Despite its limitations, the SJN Theory has been used as the therapeutic basis for foot orthosis therapy by many well-respected individuals within the podiatry community for the past thirty years. This therapeutic approach to foot orthosis therapy is based on the idea that “abnormal compensations” for “deformities” is the major mechanical factor that causes injury and it has produced good treatment results in many cases. However, it does not necessarily involve specific modification of foot orthosis design to account for either the anatomical site of injury or for the magnitude and mechanical nature of the pathologic loading forces which are occurring at the site of injury which are very important factors in successfully treating many mechanically based injuries in the foot and lower extremity.

    [Reprinted with permission from: Kirby KA.: Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002. Precision Intricast, Inc., Payson, AZ, 2002, pp. 11-12.]
     
  2. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    In one of my lectures, I have a slide that lists some of the problems with subtalar joint neutral:
    ...don't figure that we still use it everyday and patients actually get better when we use it :confused:
     
  3. DrPod

    DrPod Active Member

    Kevin - your insights; and Craig - your cynicisms are refreashing.
     
  4. The subtalar joint neutral (SJN) approach to foot orthosis therapy is, as far as I can see in my discussions with podiatrists in many countries, is dying a slow death after years of dominance in podiatric biomechanics educational circles. It seems to be only the older zealots who have taught SJN theory for years in the podiatric medical institutions around the globe that are still teaching these theories to their students and that still cling stubbornly to its teachings.

    The only reason that I can think of why these individuals are still teaching these theories after so little research support is either because they have not done any independent thinking of their own for the past 20 years, don't like the feeling of being uncomfortable by having to actually read the research literature and learn something new that is based on more modern research and more valid biomechanical principles, or just think that Mert Root, John Weed and William Orien were never wrong and that it is "blasphemous" to think that they could have been wrong in some of what they taught.

    Why do I think that the SJN approach to foot orthosis therapy is dying? Let me list a partial list of the reasons why:

    1. It doesn't explain many biomechanical phenomena that are apparent in the human foot.
    2. It assumes that the STJ neutral position is the position of ideal STJ function for nearly all feet.
    3. It does not have an explanation that allows prediction of the wonderfully effective anti-pronation orthosis techniques of the Blake inverted or medial heel skive technique within its theory.
    4. It teaches that an inverted heel is abnormal.
    5. It teaches that a non-perpendicular forefoot to rearfoot relationship is abnormal.
    6. It teaches that there is only one correct posterior heel bisection whereas informal studies have repeatedly shown that the range of error in bisecting the calcaneus is +/- 5 degrees (at least) from one clinician to another.
    7. It bases nearly all measurements on the calcaneal bisection, which has a wide range of interexaminer error, so that the common errors in calcaneal bisection made by clinicians will lead to errors in most of the important measurement parameters that form the basis of orthosis prescription for the theory (i.e. forefoot to rearfoot measurement, STJ range of motion, RCSP and NCSP).
    8. It teaches that a non-vertical tibia is abnormal.
    9. It teaches that foot orthoses work by forcing the foot to function more in STJ neutral position, whereas multiple research studies have shown that this is definitely not the case.
    10. It teaches that an inverted heel will pronate to vertical, to make it more stable (?), but that if it pronates more than 2 degrees past vertical, it will become maximally pronated (all from a measurement that is +/- 5 degrees from one clinician to another!!). What a joke!!!! :eek:

    However, those of you who have heard me lecture know that I do still make these measurements myself since I find it helps in my clinical decision making process. This still does not change my opinion that the SJN approach to foot orthosis therapy is woefully inadequate by itself to explain how foot orthoses work and how the clinician can best optimize the design of foot orthoses for patients with mechanically based pathology of the foot and lower extremity.
     
  5. I think I also forgot to mention that there is large range of error in the determination STJ neutral postion from one clinician to another. I have seen (numerous times) other podiatrists position the STJ 5 degrees more inverted from what I would call the STJ neutral position in the same foot.

    In addition, John Weed and Mert Root both lectured numerous times that the very common practice of using talo-navicular congruency as an indicator for STJ neutral position was not an appropriate method for determining STJ neutral position since the talo-navicular joint is not part of the STJ but is rather part of the midtarsal joint.

    This talo-navicular congruency method of determining STJ neutral position did not originate with Mert Root, John Weed, or Bill Orien. I heard this technique originated, instead, at one of the major orthosis labs in the east coast of the US when Mert Root had first made the neutral suspension casting technique popular. To my knowledge, talo-navicular congruency is not mentioned as a method for determining STJ neutral either in Root et al's book on Neutral Position Casting Technique.
     
  6. podomania

    podomania Active Member

    Dear Mr. Kirby
    I originate from Greece and I am 'newly' qualified podiatrist (3years ago) with an MSc in Clinical Biomechanics. The Stjt neutral approach to foot therapy has been bothering me since the 1st day that i was taught about it (mostly due to the reasons that you have mentioned). However it has been the basis of my approach to all my patients and the basis of the podiatric biomechanics in general. If somebody withdrew this theory from the 'market' it would really frighten me as i would not know were to start from when i examine a patient. Stjt neutral is the nucleus of what i was tought in biomechanics as a student in the UK. It is obvious that there is not enough scientific support to use it as major clinical tool but are there any alternatives? What would you suggest if a podiatrist skips the STjt neutral approach? Is there an alternative or shall we make our diagnosis only by looking the patients foot?

    Please forgive any mistakes as English is not my native language.
    Sincerely
    Lefteris
     
  7. I started with the STJ neutral approach and formerly taught it to podiatry students while I was a Biomechanics Fellow at CCPM from 1984-1985. I still use it in evaluating patients but use the STJ axis location/rotational equilibrium theory of foot function (Kirby KA: Subtalar joint axis location and rotational equilibrium theory of foot function. JAPMA, 91:465-488, 2001) for trying to decide how best to treat patients with orthoses. You could look at both my first and second books to get a better idea of how I approach a variety of pathologies using this approach to foot orthosis therapy.

    By the way, your English writing skills are better than many English-only speaking podiatrists who contribute to this forum so I wouldn't worry too much.
     
    Last edited: Mar 15, 2006
  8. podomania

    podomania Active Member

    Thank you vey much for the quich response, although i have to admit that i have no idea of what the "STJ axis location/rotational equilibrium theory of foot function" is and unfortunately i am not able to get hold of this article....I am going to try harder to find it, so that i can have a view of what you are talking about.
    Many thanks
    Lefteris
     
  9. I am going to be somewhat controversial in order to provoke a response from my good friend Kevin.

    If we strip down the STJ neutral approach described by Root et al. we see at it's heart the philosophy that by attempting to control extreme excursions of the STJ through RoM (i.e. hold it around it's neutral position) we may prevent/ treat foot an lower limb pathology.

    If we strip down SALRE (subtalar joint axis location and rotational equilibrium theory) we see at it's heart the philosophy that by attempting to control extreme excursions of the subtalar joint axis and/ or the moments acting about it we may prevent/ treat foot and lower limb pathology.

    Since axial position is directly linked to joint position and thus the moments produced about the STJ are directly linked to joint position, I put it to you, that these two philosphies are one and the same, just stated in differing terms.

    Looking forward to the debate. :D

    Satan, Toby, Maphisto.............. any sympathy?
     
  10. When have you ever been controversial, Simon? :D

    Isn't your line of reasoning something like the non-athlete who never played sports saying that Rugby is just a game involving a bunch of guys running around a field of grass trying to keep the ball away from the other team and trying to make an occasional score. And this is basically the same as Soccer (aka football) which is just a game involving a bunch of guys running around a field of grass trying to keep the ball away from the other team and trying to make an occasional score?!

    The basis of the STJ neutral approach is that the foot ideally stands in relaxed bipedal stance and functions in the middle of midstance of walking in the STJ neutral position. It relies on the assumption that heel verticality is the ideal position to cast correct most patients' foot orthoses and also assumes that the calcaneal bisection is easily reproduced with little error from examiner to examiner. Unfortunately, none of these ideas of the STJ neutral position are correct.

    The STJ neutral approach did not involve specifically designing orthoses to treat specific pathologies. The STJ neutral approach did involve specifically involve designing orthoses to "prevent compensation for foot deformitiies". The idea was, and I got this directly from listening to lectures by Mert Root, John Weed, Bill Orien and Tom Sgarlato, that by making the patient function closer to the STJ neutral position that this would improve gait function and, as a direct result of improved gait function, would heal most mechanically-based injuries of the foot and lower extremity. In other words, a patient with a 5 degree everted forefoot deformity and with a 5 degree rearfoot varus that stood in relaxed calcaneal stance position with the calcaneus vertical would need an orthosis balanced with the heel vertical with a 5 degree intrinsic forefoot valgus correction and a 4/4 degree rearfoot post (regardless of whether that patient had posterior tibial tendinitis or chronic peroneal tendinitis).

    The Subtalar Joint Axis Location and Rotational Equilibrium (SALRE) Theory of Foot Function, on the other hand, is a theory of foot function that allows one to predict internal forces within the foot so that, when combined with the idea of Tissue Stress can be used together to design mechanical therapy for the patient. In other words, using this approach, orthosis therapy can be more precisely tuned to obtain optimal orthosis prescriptions for mechanically-based pathologies of the foot and lower extremity.

    Therefore, regardless of the STJ neutral position and regardless of the forefoot to rearfoot relationship of the foot, the patient with a posterior tibial tendinitis/dysfunction is treated in a very different manner from the patient with chronic peroneal tendinitis since internal forces that cause each pathology are very different from each other. Therefore, the treatments are dictated by specific pathology and internal forces, not are not always guided by externally apparent "deformities". However, the STJ neutral and SALRE approaches are similar in that they both use foot orthoses to try and make the patient better and both try to prevent abnormal joint motions and abnormal forces.

    Those with a deeper understanding of these two theories of foot function, just like those who have a deeper understanding of the games of rugby and soccer, will realize that they are not basically the same, but are, indeed, very different from each other.
     
  11. If legend is true, Webb-Ellis was playing association football at Rugby school when he picked up the ball and ran with it. Given that the two modern games have their origins in the same game, one may conclude that they share many of their attributes, and philosophies ;)

    All feet stand in relaxed bipedal stance. (I'm sure this is a typo Kevin)

    From a tissue stress point of view this makes good sense, since the net least tissue stress in the soft-tissues around the STJ is likely to occur around the midrange of the joint. At this point the STJ axis is also likely to be around it's midrange position, so by attempting to limit the STJ axis excursion about this region would seem to reflect the SALRE point of view too.

    Regardless of the model adopted the majority of casts are taken in neutral ala Root et al. In terms of balancing heel to vertical is this any less random than adding a 15 degree, 3mm heel skive?

    In our study of axial palpation technique we found poor inter-tester reliability.

    I'm not sure SALRE really designs foot orthoses to treat specific pathologies, at the end of the day we try and either increase supination moment or pronation moment or a combination of both. After all, you can add a varus rearfoot post, valgus rearfoot post, you can do either of them with a heel lift or the heel lift on its own, you can varus forefoot post or you can valgus forefoot post. Given the available combinations there are really only 12 basic permutations of posting. Since we don't seem to know the relationship between the angles of posting and the changes in kinetics/ kinematics observed it could be seen as a little bit random.

    With regard to the concept of "compensations" I would ask this: what causes a medially deviated STJ axis?

    In terms of trying to make the patient function around neutral and help the patient heal, see my comments previously regarding tissue stress and joint position.

    So in the example you give above I think its important to remember gait is 4 dimensional and that orthotic posts need GRF to "work". So the rearfoot post may help the Post Tib, and the forefoot post may help the peroneals a little. The rearfoot post may limit medial excursion of the STJ axis and/ or increase net supination moment from initial contact through to unweighting of the heel (which if I remember my EMG is kinda when the post tib should be doing its thing -right?). As the forefoot loads and the heel begins to unweight through propulsion (when the peroneals need to do their thing) the forefoot post should have the reverse effect, limiting lateral excursion of the STJ axis and/ or increasing the pronation moment. So why couldn't this device be good for both conditions?

    Just playing devil's advocate (as you know) Kevin :)
     
  12. Yes it was a typo....it should have read:
    "The basis of the STJ neutral approach is that the foot ideally stands in the STJ neutral position in relaxed bipedal stance.



    All feet stand in relaxed bipedal stance. (I'm sure this is a typo Kevin)



    The difference between the two models comes from the fact that the STJ neutral approach balanced nearly all casts at heel vertical, and only balanced the heel in a non-vertical position in the specific cases of tarsal coalition/peroneal spasm (where the cast was balanced everted) and in partially compensated rearfoot varus (where the cast was balanced inverted) since the calcaneus was still inverted in its maximally pronated position. In the tissue stress/STJ equilibrium approach, however, there is no standard heel balancing position since the heel should be more inverted if there is a symptom caused by excessive STJ pronatoin moments and should be more everted if there is a symptom caused by STJ supination moments. These orthosis therapies aren't random but are specific for pathology and abnormal internal forces present. If you thought that the therapies are random why then would you limit your therapeutic orthosis options to only a 15 degree, 3 mm heel skive? Why not make a 65 degree 15 mm medial heel skive orthosis and see how it worked on that 80 year old lady with plantar fat pad atrophy? Or why not make a 6 mm lateral heel skive with extra medial expansion thickness with a 1/2" forefoot valgus extension orthosis in the patient with a grade II posterior tibial dysfunction? In other words, if the therapies were truly random, as you suggest, then all the permutations of orthosis therapy could be tried for each patient. The truth is, that in clinical practice for those of us that use these tissue stress/STJ axis location methods of treatment, that these therapies are not random but are very specific. The choice of orthosis prescription is dependent on internal forces, measurements both nonweightbearing and weightbearing, gait examination results, and importantly, clinical experience, as you well know, Dr. Spooner.


    Good point. Agreed that this is a very difficult technique to master. Using the STJ palpation technique (Kirby KA: Methods for determination of positional variations in the subtalar joint axis. JAPMA, 77: 228-234, 1987), I palpated for STJ axis location in three cadaver feet in an experimental study at Penn State a few summers ago. In our study at Penn State I was within a few mm in one foot but off by 2x-3x that much in the other two cadavers (using bone pins with marker quartets on talus, calcaneus and tibia). However, both Greg Lewis (biomechanics PhD student) and Steve Piazza (PhD biomechanist) felt that I was close enough for clinical usefulness in all three feet, but probably not close enough in the last 2 feet for scientific study. This is what I expected all along. However, our little study and collaboration has resulted in us putting our heads together to come up with a possible method by which to isolate the STJ axis spatial location in a live foot without drilling pins into the talus. This will be very exciting research for the international biomechanics community if we are successful [Lewis, G.S., Kirby, K.A., Piazza, S.J. Determination of subtalar joint axis location by restriction of talocrural joint motion. Gait and Posture (in press)].http://www.sciencedirect.com/scienc...serid=10&md5=4cce5703306ff4a3764e2e70f41342d4

    Trying to answer this question is somewhat problematic. First of all, there is a multitude of potential causes for this abnormal spatial location of the STJ axis (e.g. inverted forefoot deformity, ligamentous laxity, weak or torn posterior tibial muscle/tendon, excessively dorsiflexed first ray, decreased first ray dorsiflexion stiffness, laterally deviated calcaneus, abnormal everted slope of sustentaculum tali, etc). Secondly, we don't know how much of the foot deformity, which we are seeing for the first time when we look at the patient's foot, is caused by a primary factor (i.e.congenital abnormality or traumatic accident) and/or how much is caused by a secondary factor such as the gradual reshaping of the foot structure and function that occurs over time due to ligament and tendon creep response, bony adaptation, etc.

    Since I don't have the answers due to lack of research data, I can only speculate. However, I can go back to the first principles of mechanics (i.e. Newton's Laws of Motion), can use the time-tested concepts of free body diagram analysis and mechanical modelling that has been used within engineering and physics for over a century in the bulding of bridges and buildings [that we all have encountered and trusted to live in, work in and drive over],and can tell you, with very good certainty, where the pathological forces are likely to be occurring within the structural components of the foot and/or lower extremity that I am seeing for the first time.

    In other words, in most cases, I don't concern myself with the past history of the foot and lower extremity as much as I concern myself with the currently present abnormal STJ axis spatial location, abnormal foot shape, other abnormal clinical measurements and abnormal gait findings and then put them all together to determine how they are all currently contributing to the abnormal internal tissue stresses that are likely causing the patient's symptoms. In this way, I can better design specific mechanical therapies with the goal of reducing the pathological internal tissue stresses that are most likely causing the patient's injury so that the patient may experience an optimal speed of healing from their injury.
     
  13. True enough Professor Kirby, but I'm just getting hung up on when to use a 15 degree 3mm heel skive and when to use that 16 degree ;)

    In light of Root's concepts of compensation, I asked what causes a medially deviated STJ axis:

    In other words a medially deviated STJ axis may well result because the STJ has pronated as a compensatory mechanism for other deformities. Viz Root rules man. ;)
     
  14. Did that last week, she'll be fine soon. :D

    Could be worse though, you could enter into a drug trial in the UK. Sick Sorry :cool:
     
    Last edited by a moderator: Mar 17, 2006
  15. Hi Kevin,
    I've been trying to find a previous thread that you provided a post for. It was for plantar fasciitis. You were writing about treatment involving 4/4 post(?). Excuse my ignorance here but what does that numerical notation mean.

    Thanks,

    Brendan
     
  16. A 4 degree/4 degree (4/4) rearfoot post indicates that there is a 4 degree varus rearfoot varus post and 4 degrees of rearfoot post motion. When viewing this orthosis from posterior to anterior, this rearfoot post would have its medial surface parallel to the anterior edge of the orthosis and its lateral surface angulated 4 degrees in valgus to the medial surface of the rearfoot post and anterior edge of the orthosis. In this fashion, when placing this orthosis on a table and pressing your fingertip onto the dorsal aspect of the posterior-lateral heel cup of the orthosis, the anterior edge of the orthosis will now be tilted into 4 degrees of varus relative to the table. Then, moving your finger more anterior and medial on the orthosis, the orthosis would evert 4 degrees to rest its anterior edge and medial rearfoot post flush to the table (i.e. 4 degrees post motion).

    This type of rearfoot post was developed by Tom Sgarlato, Mert Root and John Weed at CCPM back in the late 1960's/early 1970's as their standard rearfoot post prescription variable for their Rohadur foot orthoses in an attempt to "allow" the foot to have approximately 4 degrees of rearfoot pronation during the contact phase of walking gait and to prevent shock related symptoms that occurred when they used a flat rearfoot post on patients. Remember, back in that era, shoes were mostly very firm, and not so soft soled (also, interestingly enough, this is also prior to the world-wide epidemic of plantar fasciitis).
     
  17. AKA Meat-pie ;)
     
  18. davidh

    davidh Podiatry Arena Veteran

    Well.......

    If you can accept the notion that STJ neutral (an appoximation of, at that time of day, on that subject/patient) produces an inverted forefoot in pretty much all cases, and you can further accept that a FF-posted or RF-posted (or combination, or whatever takes your fancy) allows the subject/pt to ambulate on a hard and flat surface (approximation of) without the inverted foot having to conform to what is, after all, an unnatural surface for us, then then using STJ neutral as a reference point makes perfect sense.

    It's only when we start using the accepted "criteria of normalcy" that the STJ theory doesn't make any sense.

    Oh, we also have to accept that the STJ (more correctly the Ankle Joint Complex) works around neutral (or an approximation of).

    Regards,
    davidh
     
  19. Berms

    Berms Active Member

    Salre

    Dear professor Kirby,
    I know this is an old thread, but I was wondering if you had any links to previous threads in which you explained the basics of the SALRE theory. Any feedback would be greatly appreciated.

    Sincerely,
    Adam
     
  20. efuller

    efuller MVP

    Yes, there are some pathologies where this is true e.g. sinus tarsi syndrome. However, there are pathologies where this is not true, eg. peroneal tendonitis. Under STJ neutral we would try and put the foot in a more "stable" position by supinating it. In SARLE and tissue stress we would try and pronate the STJ to treat peroneal tendonits. True, a forefoot valgus wedge/post may help the peroneal tendonits if the patient was lucky enough to have that measurement under STJ Neutral theory.

    If you choose to look at the similarities and ignore the differences then you will see them as the same. They do have many similarties, because you cannot ignore the numerous successes that occured with NP theory. (My own feet owe a lot to NP theory. However, I prefer my orthoses with the medial heel skive added to the original NP cast.) Any replacement theory has to be able to account for the successes of the previous theory.

    Where I find one of the most troubling parts of neutral position theory is trying to put into practice the notion that you should not evert the foot farther than it can go. When I was a student, aproximately an entire semester was spent saying this in more words and a lot more indirectly. Additionally, in measureing forefoot to rearfoot relationship and calcaneal position it is nearly impossible to predict whether or not your device will attempt to evert the foot farther than it can go. (You measure forefoot to rearfoot in neutral position, but in stance >90% of the population stands in a more pronated position than neutral position and hence the true forefoot to rearfoot relationship, in stance, is not measured) This criticism is staying within the pardigm and doesn't even address the problem that forefoot to rearfoot cannot be measured accurately. (Heel bisection + variable amount of load on 5th met when you measure.)

    Yes, SARLE and tissue stress have used some of the ideas of NP theory, but I disagree with the idea that they are the same thing. SARLE uses wedges on both the forefoot and rearfoot, but it uses a different rationale for their selection, and sometimes uses a different treatment (See peroneal tendonitis above.) However, SARLE gives you some idea of how to modify your device if it does not work the first time. I remember as a student, patients coming back and having to make them a whole new pair of devices because the first pair did not work. Occaisionally, we tried to figure out the mistake, (there must have been a mistake, because they didn't work.) but most of the time we just used the exact same process and hoped we would get different results. Spot heating the device was frowned upon. Under tissue stress and SARLE it is OK to modify the existing shell and you can choose to add more varus rearfoot or more valgus forefoot based on what you see. I think that there is a difference between the two theories.

    On what causes a medially deviated STJ axis. Individual variation. The position of the axis is determined by shape of the facets of the talocalcaneal joint. I would agree that if there is some foot problem that would cause more internal talar rotation, the axis will be more medially deviated. Some people will start with a more medially deviated STJ axis than others. Those with a more medially deviated STJ axis are more likely to get PT dysfunction and then if the tendon becomes ruptured the forefoot will abduct more, worsening the position of the axis.

    Cheers,
    Eric Fuller
     
    Last edited by a moderator: Sep 6, 2006
  21. Adam:

    Please send me your e-mail address and I will send you a pdf copy of my 2001 paper that explains SALRE theory in great detail (Kirby KA: Subtalar joint axis location and rotational equilibrium theory of foot function. JAPMA, 91:465-488, 2001).

    Once you have read the paper then please feel free to ask me specific questions regarding the theory. I will try to answer them in a timely manner for you and any other lurkers that may be interested.
     
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