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Plantar fascial tenson and digital purchase force

Discussion in 'Biomechanics, Sports and Foot orthoses' started by admin, Nov 9, 2005.

  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 2001 Newsletter (you can buy the 2 books of newsletters off Precision Intricast):


    During relaxed bipedal stance in the normal foot, the plantar aspects of the digits exert a force on the ground. The ground reaction force (GRF) that results from the interaction of the plantar digits with the ground allows the plantar digits to lay flat on the ground and also allows the digits to bear body weight during standing and other weightbearing activities. Since the magnitude of force with which the digits purchase the ground is directly related to the magnitude of GRF on the plantar digits, then the GRF plantar to the digits will be called, throughout this discussion, the digital purchase force (DPF).

    Hicks was one of the first authors to attempt to mechanically analyze the cause of the DPF seen both in living and cadaver feet. He noted that the tension in the plantar fascia that results during standing tends to “pull the windlass into the unwound position”, or have a “reverse windlass” effect. Hicks described that the increased DPF that results from the pull of the plantar fascia can be observed in any standing foot especially when the individual leans forward and can be easily detected by noting how difficult it is to slip a piece of paper from beneath the digits. He also felt that the magnitude of DPF equaled approximately one half of the magnitude of GRF exerted on the plantar metatarsal heads. Hicks claimed that the ability of the digits to “share the load” of the forefoot resulted in decreased load on the metatarsal heads and also resulted in an increased ability for the body to balance its center of mass (CoM) in a more anterior position during relaxed bipedal standing (Hicks, J.H. The Three Weight Bearing Mechanisms of the Foot. Pages 161-191 in F.G. Evans (ed): Biomechanical Studies of the Musculoskeletal System. C.C. Thomas Co., Springfield, Ill. 1961).

    When an individual is standing in relaxed bipedal stance, the CoM of the body is nearly always anterior to the ankle joint axis. As a result of this anterior position of the CoM to the ankle joint, a dorsiflexion moment across the ankle joint axis is generated which would tend to make an individual fall forward if there were no muscular activity to balance the CoM in that position. In order to balance the CoM of the body in an anterior position in relation to the ankle joint, the gastrocnemius muscle becomes tonically active in relaxed bipedal stance (Fig. 1). The increased tension in the Achilles tendon that results from contractile activity in the gastrocnemius muscle generates a plantarflexion moment across the ankle joint that counterbalances the ankle joint dorsiflexion moment from the anteriorly positioned CoM (Kirby, Kevin A: Biomechanics of the normal and abnormal foot. JAPMA, 90:30-34, 2000).


    Figure 1. In relaxed bipedal stance, gastrocnemius muscle contractile activity causes increased tension in the Achilles tendon that is necessary to maintain balance of the center of mass of the body anterior to the ankle joint axis. In turn, the Achilles tendon tension causes increased ground reaction force plantar to the metatarsal heads (GRFM) that causes an increased forefoot dorsiflexion moment and increased rearfoot plantarflexion moment across the oblique midtarsal joint (OMTJ) axis. Increased tension in the plantar fascia is required to resist the arch flattening force that results.

    The increased tensile force in the Achilles tendon that results from the contractile activity of the gastrocnemius muscle also causes other effects on the foot. One important effect is to increase the GRF plantar to the metatarsal heads of the foot. Because of the increased GRF on the plantar metatarsal heads, there is increased dorsiflexion moment of the forefoot on the rearfoot and increased plantarflexion moment of the rearfoot on the forefoot being generated across the oblique midtarsal joint (OMTJ) axis. This combination of the rearfoot tending to plantarflex and the forefoot tending to dorsiflex results in a flattening force on the medial and lateral longitudinal arches of the foot (Fig. 1). One of the main structures resisting this arch flattening force is the plantar fascia (Kirby, K. A. Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Inc., Payson, Arizona, 1997, pp. 33-36, 87-89, 191-192).

    The plantar fascia sends individual digital slips anteriorly to insert onto the bases of the proximal phalanges of the lesser digits by way of its insertion into the plantar plate of the metatarsophalangeal joint (MPJ). Increased tension in the plantar fascia during relaxed bipedal stance causes a plantarflexion moment across the MPJ axis that tends to plantarflex the digit into the ground. Therefore, the tension in the plantar fascia which results from increased GRF plantar to the metatarsal heads in relaxed bipedal stance directly causes increased MPJ plantarflexion moment and increased digital purchase force (Fig. 2).


    Figure 2. Ground reaction force on the metatarsal (GRFM) causes increased tension on the plantar fascia which inserts on the base of the proximal phalanx of lesser digits by way of the plantar plate. The result of the increased plantar fascial tension is increased plantarflexion moment across the metatarsophalangeal joint axis and increased digital purchase force.

    In summary, the tension within the plantar fascia that results from the mechanics of the body trying to balance itself over the two feet during relaxed bipedal standing helps maintain the digits in a stable position against the ground by causing increased MPJ plantarflexion moment and increased digital purchase force. It is critical to understand that the ability of the plantar fascia to maintain the digits purchased firmly on the ground is a result of a passive increase in tensile force in the fascia, and is not dependent on the contractile activity of any of the digital flexors muscles. Therefore, when considering a plantar fasciotomy or when treating patients with traumatic rupture of the plantar fascia , the wise physician should inform patients of the potential change in function of the plantar fascia which will result from the loss of integrity of the fascia.

    [Reprinted with permission from: Kirby, Kevin A.: Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002. Precision Intricast, Inc., Payson, AZ, 2002, pp. 117-118.]
    Last edited: Nov 9, 2005
  2. Craig Payne

    Craig Payne Moderator

    We published a review on the reverse windlass a while back:
    It also reminds me of the work by Stainsby, an orthopaedic surgeon in the UK, who has apparently been working on a book for a very long time ... I heard him speak at a conference in Leeds in 98 or 99(?) in which he pretty much blamed all forefoot pathology on a lack of the reverse windlass, or what Kevin call the digital purchase. We use the FEWT (Footstool edge weightbearing test) or sometimes the YPEWT (the Yellow Pages edge weightbearing test) to test this --- ie if the reverse windlass is intact, the toes should plantarflex below the weightbearing plane when the toes are hanging over the edge of the stool or yellow pages.

    If they do not do this then plantar fasica is very ineffective at holding the toes on the ground during propulsion --> claw toes, hammer toes and HAV .... apparently.
    Last edited: Nov 9, 2005
  3. Was hoping this newsletter would generate some interesting discussion on the mechanical role of the plantar fascia in allowing the digits to contact the ground in standing without the individual exerting muscular contractile force to the digits. Obviously, one can readily see that patients with plantar fasciotomies or plantar fascial ruptures will be much more likely to suffer hammertoe deformities, when one understands the priniciples outlined in this newsletter.
  4. PF 3

    PF 3 Active Member

    Craig and Kevin,

    Do we know any other reasons why someone might have an in-effective reverse windlass mechanism apart from plantar fascial rupture and fasciotomies?

    Also explains why a patient of mine missing her distal phalanges on her right foot struggled with balance even when simply standing still.

  5. The plantar fascia will not be under normal resting tension if the Achilles tendon has been overlengthened or has been ruptured which, in turn, will cause of lack of digital purchase force. A plantar fascia that has been plastically elongated (I don't know how often this occurs, but it should be able to occur theoretically) will cause a lack in digital purchase force to occur.

    Digital purchase force (DPF) provides a mechanism by which to increase the surface area of the foot to reduce the ground reaction force (GRF) and pressure plantar to the metatarsal heads. DPF also allows the center of mass (CoM) of the body to be positioned more anteriorly than would be possible without DPF. DPF allows the individual to increase the magnitude of posterior accelaration of their CoM when the CoM is perturbed anteriorly or the CoM is positioned too far anteriorly.

    In conclusion, a patient without digits loses much more than simply a filler for the toe box of their shoes.
  6. David Smith

    David Smith Well-Known Member


    When analysing plantar facia tension and DPF would you consider it more valid to use the Truss model or the arch model. The Truss model of a triangle of two weight bearing sides and a tensioner or binder (plantar facia) holding them in position is quite convenient as the stable truss has only compression and tension forces thru its members and no bending moments or turning moments about the nodes..

    Cheers Dave smith
  7. Dave:

    Obviously, it is better to use a model of the longitudinal arch and plantar fasca which is closest to reality, but not so complicated that most podiatrists will not be able to grasp the mechanical concepts that are trying to be conveyed. Of course, most podiatrists don't know what a moment is anyway so I guess I shouldn't be so worried.

    The problem with the truss model is that the mpjs allow plantarflexion motion of the digits with increased plantar fascial tension, which would not occur in a true truss where no rotational forces occur at the nodes. However, the truss is an excellent model to use in trying to understand why plantar fascial tension would need to increase in magnitude as the longitudinal arch height is lowered, assuming constant vertical loading force on that truss. This also is convenient to use in describing why functional hallux limitus is seen to exist with medial arch height that is lower than normal, but then you must add back on the digits to the truss model to do so, therefore making it again not a true truss.

    Another option, rather than the truss is to use the tied-arch model, similar to some bridge and arena dome constructions http://www.matsuo-bridge.co.jp/english/bridges/basics/arch.shtm

    A favorite website of mine for exploring the compression and loading forces through the structural elements of a struss with different geometries from John Hopkins University http://www.jhu.edu/virtlab/bridge/truss.htm

    I'll bet you'll be one of the few members of this forum who will have a lot of fun with this little program.
  8. Lawrence Bevan

    Lawrence Bevan Active Member

    As an aside in relation to this discussion.

    In diabetics, those with neuropathy often develop clawed, retracted toes. The research suggests that they develop increased thickness and stiffness in the plantar fascia and a reduction of the movement in the 1st MTP.

    Can we extrapolate the reverse windlass concept to expalin this?
  9. David Smith

    David Smith Well-Known Member

    Kevin K

    http://www.jhu.edu/virtlab/bridge/truss.htm Nice link, very useful.
    But it highlights a problem I have with arch lowering and the inelastic plantar facia.
    The plantar facia is relatively non elastic, it cannot stretch, so the plantar vault cannot lower or flatten in the saggital plane once all the slack is taken up in the joints and the digits are plantarflexed to the ground. There are only 2 ways I can see that the structure can lower and maintain the tension and length of the plantar facia. One is for the whole structure to fall over sideways, the other is for the rearfoot to twist on the f/foot, rotate in opposite directions, and the f/foot abduct on the rearfoot, which is effectively what happens in pronation.
    I have measured several feet and foot models and if one uses a truss model with the apex at the TC joint and the distal nodes at the MPJ's and the weight bearing plantar surface of the calcaneous then this gives tensions in the plantar facia of about 1/2 body weight when the rearfoot is at or somewhere near the vertical position and in resting stance and the CoM above the TC Joint.
    What would you say Kevin.
    What sort of tensions of the PF are achieved in normal stance in reality?

    Thanks Dave Smith
  10. Research from over 40 years ago has shown that the plantar fascia is elastic and can deform under tensile loads (Wright DG, Rennels DC: A study of the elastic properties of plantar fascia. JBJS, 46 (A):482-492, 1964). In other words, the plantar fascia can stretch!

    Erdimir and associates from Penn State Biomechanics Lab have shown in their work in their dynamic cadaver simulator that plantar fascial tension was low at heel strike, plantar fascial tension gradually increased during midstance to peak at heel off at 0.96 times body weight, and that Achilles tendon force was found to be effective predictor of plantar fascial tension (Erdimir A, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA: Dynamic loading of the plantar aponeurosis in walking. JBJS, 86A:546-552, 2004).

    Therefore, from the research from Erdimir et al, we can realistically estimate that for every extra pound of weight a patient carries on their feet, that the plantar fascia is subjected to an extra pound of tensile loading force! No wonder that obesity may cause plantar fasciitis.

    Dave, you should have been at my demonstration at the PFOLA meeting in Vancouver a few weeks ago with the wooden model of a foot that my older son and I constructed where I simulated the plantar fascia with 5 nylon cords, 1/8" diameter, and the plantar ligaments with 5 more 1/8" diameter nylon cords. As the arch was raised, vertical loading of the "wooden foot" produced little arch deformation, as the arch was lowered, loading of the foot produced quite a bit of "spring" in the arch, even though the cords were not changed in any way but their length, to allow for arch lowering or raising. This is probably due to the greater tensile loads in the rope (and plantar fascia) with decreased arch height and greater tensile strain in the rope (and fascia).

    Who says the plantar fascia is inelastic?!
    Last edited: Nov 16, 2005
  11. Craig Payne

    Craig Payne Moderator

    We have done exactly that:
  12. One more study that shows that the plantar fascia and plantar ligaments all stretch and are spring-like structures under load comes from a study that was done on a cadaver foot placed under a mechanical actuator and measured the load vs deformation of the arch of the foot to simulate running. The researchers found that with serial sectioning of the plantar fascia and plantar ligaments that the slope of the load-deformation curve decreased (longitudinal arch stiffness decreased) with each ligament that was sectioned (Ker RF, Bennett MB, Bibby SR, Kester RC, Alexander RM: The spring in the arch of the human foot. Nature, 325: 147-149, 1987). In addition, they found that the plantar fascia and plantar ligaments were estimated to be able to store and release 17 Joules of kinetic energy with each footstrike in a 70 kg man running at 4.5 m/s (5:58 mile pace).

    The plantar fascia and plantar ligaments do stretch!!!
  13. David Smith

    David Smith Well-Known Member

    Dear Kevin

    You wrote

    I am aware that all materials deform under stress, I wasn’t aware of the exact elastic modulus of the plantar fascia (and imagined it to be much higher than it apparently is). After some literature research, and some analysis of my own, I now am.
    1)Wright DG, Rennels DC: A study of the elastic properties of plantar fascia,
    2)Gefen A in vivo elastic properties of plantar fascia during the contact phase of walking foot and ankle int.2003.
    3)Maruoaka T et al elastic properties of human achilles tendon are correlated to muscle strength Journal applied physiology 2005
    4) D’Ambrogi et al, Contribution of Plantar Fascia to the Increased Forefoot Pressures in Diabetic Patients, diabetes care 2003.
    5) Gefen A Stress analysis of the standing foot following surgical plantar fascia release, Journal of biomechanics 1995

    6) Jacob S, Three-dimensional Foot Modeling and Analysis of Stresses in Normal and Early Stage Hansen's Disease with Muscle Paralysis, Journal of rehabilitation research and development, 1999

    7) Plantar Fasciitis and Fascial Rupture: MR Imaging Findings in 26 Patients Supplemented with Anatomic Data in Cadavers Theodorou D J 2000

    So the plantar fascia can stretch quite a bit under tensile stresses applied to it during ambulation. Maximum stress of 3.5kN- 4kN (my calculations, which seem to be the maximums applied by Kerr for 10mm extension but I expect that he was using cadaver specimens, which are stiffer, Geffen A #2) seems typical for an 80kg person in normal walking. However in resting stance with the foot in a neutral position (vertical calcaneal) the PF tension is very low at only half the applied weight I.E. 80kg man = 40kg each foot so only 20kg or 200N tension which at stiffness stated below would only = deformation of 1mm so why, I thought, would the arch flatten and pronate in resting stance? *-* (goto your JHU site Kevin http://www.jhu.edu/virtlab/bridge/truss.htm set the calcaneal inclination at 55dgs and it is very useful in showing this at the click of the mouse)
    In my analysis of the plantar fascia tension I took several different approaches but the most convenient was to use a Truss model, as used by most modern biomechanists (jacob being an exception), the apex being the transverse axis of the TC joint. I assumed a slightly cavus compliant foot for maximum range of deformation and stress values. Using data on file of typical plantar forces (GRF) as measured on a Kistler force plate with max GRF of 120%-125% b/w in normal ambulation.
    I analysed in 4 different situations I.E.
    a) resting stance with neutral/vertical calcaneal,
    b) rcsp pronated position with arch lowered by 26mm,
    c) propulsive stance at heel lift (max GRF) calcaneal in neutral/vertical and
    d) propulsive stance arch lowered 26mm. This resulted in an elongation of the arch of 25mm. These values are twice that of the study by Gefen A 2003 #2 so max stress is much higher but the important thing is the graph curves of strain to stress (stiffness) are similar.

    The only problem with this is that although I know that people can and do maximally pronate at rcsp, how can body weight alone produce enough force to elongate the PF to full extension if Hooke's law of a proportional stress / strain relationship applies. Is maximal pronation different in the RSCP foot compared to the more greatly loaded foot. Is there more F/foot abduction / lateral bending of the foot that allows the PF to remain short.

    In Geffens #2 Study the max values of tension were only 1000N-1200N which seems low. But the subjects were light at 58-60kg. The foot contact time seemed a little short at 450milli/sec even if you add 25%-30% for heel strike not measured still 600milli/sec stance phase might suggest short steps which would equal low GRF and therefore low stress in PF.

    Suprisingly (or not) the results I got were very close to the conclusions drawn by the above research both in max stress, deformation ratio/stiffness (mine 155N/mm V’s 175-+ 40N/mm Gefen A. #2 ) and elastic modulus 80 -90MPa (Smith JW concluded that it could be as high as 345MPa but he used in vitro specimens which typically give higher stiffness results.) Compare this to the stiffness of ligaments estimated at 1500 N/mm Jacob S #6.

    **Why can the arch flatten at low tension stress in the PF – well the make up of the PF is such that stiffness ratio is not linear IE it deforms more (N/mm) at low stress values and less at high stress values. The actual structure consists of stiff collagen fibres wrapped in wavy or coiled elastic fibres so that in early stance the stress load is on the elastic fibres until they stretch enough for the collagen fibres to take the load. Gefen A #3.

    “The plantar fascia and plantar ligaments do stretch!!!” Agreed!

    Even so do you think that it may be that pronation and f/foot abduction as well as initially increasing PF tension, by lowering the arch, increasing angles and moment arms, also eventually inhibits PF tension from rising to values that may cause rupture.
    If the calcaneous and mets just continued to extend/dorsiflex only in the saggital plane then PF stress would increase to levels where rupture may occur, by rotating and curving in the transverse plane the PF does not become any longer as the arch flattens. Hooke’s law, - The general law of mechanics that stress is directly proportional to strain, so no relative increase in strain = no relative increase in stress.

    Also if as the CoM moves over the ankle the GRF drops to 50% of max then wouldn't it be reasonable to expect that the arch would be raised by the elastic energy stored in the stretched PF and therefore the PF shorten and the stress reduce. This is not reported by Geffen but his graphs of stress to strain / tension to elongation do show a flattening of the curve at this time.

    Could it be that, in reality, the PF elastic tension is not strong enough to resupinate from the pronated position which tends to be in a mechanically disadvantaged position. Might this indicate that a correct position of the foot at the right time might be advantageous to resupination.

    KK you wrote
    The problem with using any arch as a model for analysis of internal foot stresses is that there are very inconvenient moments occurring which have to be accounted for to achieve equilibrium which then gets into the area of reciprocal antagonism which isn’t very nice to work with. Also unless the arch is Catenary (see - http://www.cpo.com/Weblabs/chap3/archf.htm) then the force vectors of tension and compresion fly out of the structure and lead to instability that again needs to be stabilised with other forces for equilibrium and you have to work out how it could all stay together.

    What about DPF? If at resting stance the PF tension is 200N then divided by 5 and with an average moment arm of 6mm then a moment of 0.32N/m is indicated. This equals about 9N GRF on each digit. At max tension this may be around 120N GRF per digit, a little to high I would guess. This might indicate that, as would be expected, some of the total PF tension is shared by other structures which do not plantarflex the toes.
    Does anyone have plantar pressure figures for the digits at heel off?

    One more thing I noticed, Some have said that children with flat feet can out perform their peers, with ‘normal’ feet, at jumping activities. Might this be that since the PF has higher tension then so must the Ach tendon and so is able to store higher elastic potential energy. Muraoka et al #3 showed how increased tricep surae strength equaled increased stiffness of the Achilles tendon and therefore increased capacity to store elastic energy.

    Hope I didn’t go on to much in this answer Kevin, just my conclusions after I spent some time on it. Some of this stuff is new to me so I don't know if it will hold up to scutiny but there it is anyway.

    Cheers Dave Smith
  14. David:

    Let me say that this is a very impressive posting, David. You have done your homework and, as I have said before, need to start publishing some of your thoughts.

    Unfortunately, I don't quite have the time and energy now to answer all your questions since I'm currently writing a paper on foot orthosis theory and research. However, let me try to answer a few of your questions.

    Glad to see we agree that the plantar fascia is elastic, not inelastic.

    Unfortunately, you will find it very difficult to accurately calculate plantar fascial tension in live subjects and will probably always overestimate tensile forces of the plantar fascia using simple geometric methods for the following reasons:

    1. The plantar ligaments of the foot are under tension causing a forefoot plantarflexion moment.
    2. The plantar intrinsic muscles may be actively contracting especially during the latter half of stance phase that also cause a forefoot plantarflexion moment.
    3. The peroneus longus, flexor digitorum longus, posterior tibial and flexor hallucis longus all are active throughout stance phase that will likewise cause a forefoot plantarflexion moment.

    All of these passive and active tensile forces acting on the forefoot would tend to lessen the actual plantar fascial tensile force in vivo versus what would be calculated from geometrical models alone (where these forces may not be accounted for). Therefore, one must take all of these factors into account when one is reading any of the papers you listed in your posting.

    Plantar fascial tension will definitely be increased with lower longitudinal arch height which I don't know if you have accounted for in your discussion.

    Plantar fascial tension should be able to be approximated by determining the magnitude and position of the center of pressure (CoP) relative to the ankle joint axis during gait since this will determine the ankle joint dorsiflexion moments, Achilles tendon plantarflexion moments and forefoot dorsiflexion moments, but with the same errors as I mentioned above for geometrical models.

    The plantar fascia will only deform plastically if it has deformed past its yield point on the stress-strain curve. This excesssive magnitude of tensile stress in the plantar fascia that will cause permanent elongation or rupture will only occur if the plantar forefoot forces are extremely high (e.g. fall from height), if the plantar ligaments have failed or have a low elastic modulus (e.g. Ehler-Danlos syndrome or spontaneous rupture of spring ligament complex), or if the plantar extrinsic (e.g. PT, PL, FDL, FHL) muscles or intrinsic muscles are weak or torn (e.g. PT dysfunction).

    All of these structures generate tensile forces that together are designed to form a redundant arch support system in the human foot. In other words, the plantar fascia, plantar ligaments, plantar extrinsics and intrinsics all work simultaneously together to generate forefoot plantarflexion moments during weightbearing activities so that no one structure must act by itself to generate these arch raising moments and the arch will be partially protected from complete collapse if one of these structures fails.

    I am attaching photo of the foot model I used during my two workshops at the PFOLA meeting in Vancouver. It includes a rearfoot, 5 metatarsal rays, 5 separate plantar ligaments, and 5 plantar fascial strands-one to each metatarsal ray. It is amazing how much more arch flattening occurs in the model at a given vertical load as the geometry of the arch is flattened versus when the arch is higher.
  15. kitaki

    kitaki Welcome New Poster

    Hello all. I have some questions regarding plantar facia lenthening that I hope you can give me some answers to. Please bear with me a bit, because this will require a bit of background information as to why it is being considered.

    My son, who is almost 3, was born with what is now called complex or atypical clubfoot, meaning that it had some very major differences from a "normal" clubfoot. He has been treated by some of the best (Ponseti) clubfoot doctors in the country, including Dr Ponseti himself. The biggest issue we are facing - and have from the beginning - is that his plantar facia is far too short and will not permanently respond to manipulation and casting. Even wearing a custom made DBB/shoe designed specifically for this purpose and successful with other feet like his, the plantar facia will not maintain stretch and every 6 months he requires recasting to bring the arch back down to a more normal position. By this, I mean that about every 6 months, his arch becomes too high to be able to wear shoes and begins to cause him pain from bearing weight on his forefoot.

    All other aspects of the clubfoot are fully corrected and have been for a very long time. There is never any relapse to anything but plantarflexion of the forefoot and slight adduction of the large toe. Structurally, the outside of his foot sits normally - that is, the last two metatarsals maintain a normal position in relation to the cuboid and that joint is on a plane. The first and second metatarsals join the cuneforms at 145 - 165 degree angle, depending on where in the cycle we are. The third metatarsal falls somewhere between the two.

    We have determined that an ATTT - which is what is normally done for a frequently relapsing clubfoot - will not help this sittuation and is unnecessary. What is left is to release or lengthen the plantar facia.

    Now, my questions. First, given this information, does it seem like this would be effective in bringing the foot into more normal alignment? Second, what would be the possible long-term effects of this surgery?

    I would like to add that I know that you can't give real/reliable medical advice without ever having seen the patient; I am not asking for anything official here, just opinions. Call it information gathering; I am working with pediatric orthopeds and would like to see if there would be a differnt light on this looking at it from a podiatry stance.

    ADDED: Forgot to mention that my son is capable of bending his foot at the Lisfranc Joint at will, that is, he can actually pull his arch into a steeper angle.
  16. A surgical release of the plantar fasca certainly can be effectively used to lower the arch of the foot during weightbearing activities. I would tend to perform this surgery earlier, rather than later, in this type of foot to minimize the risk of permanent foot deformity and dysfunction. I highly suggest that any consideration for a plantar fascial release be left to the consultant surgeon. However, you might find it worthwhile to seek the opinion of a podiatric surgeon that does these types of procedures before you proceed further with your son's treatment.
  17. All,

    I have enjoyed this stimulating discussion. I have one question though: The analyses and discussions have focused on passive structures, what effect do the contractile structures have in all of this? Surely, the length/ tension relationships of the long flexors and intrinsic muscles inserting into the digits may influence digital purchase force and add to redundancy?

    Best wishes,
  18. Sorry Kevin did mention the extrinsics
  19. David Smith

    David Smith Well-Known Member

    Dear All

    I wondered if anyone regularly or has had occasion to record data of plantar hallux peak pressures/force or force time curves during the stance phase of gait in subjects with a 'normal' gait. IE does not excessively pronate and does not exhibit FncHL. If you do they would be very useful to me at present.

    Thanks Dave

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