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Advise for difficult prescription please

Discussion in 'Biomechanics, Sports and Foot orthoses' started by David Smith, Nov 17, 2006.

  1. David Smith

    David Smith Well-Known Member

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    Dear all

    Have a patient, Young woman 27yrs old, PE teacher. Been off school for several weeks due to plantar digital neuritis (2nd 3rd interspace) and transverse met ligament strain 1st - 2nd. Right foot only.
    Seen GP and ortho. advised try orthoses.

    She has a symmetrical knock knee stance due to internal rotation of knee and high Q angle but not tibial valgum. No lld or hip misaligment but pelvis is anteriorly tilted. GMax seem full and even but weak (has difficulty posteriorly rotating pelvis, cannot clench buttocks)
    The STJ bi lateraly has wide RoM especially the r/f which is 40dg inv - 12 dgs eversion. RCSP 10 dgs eversion bilateral. ankle RoM was tight r/f -2dgs l/f 0dgs d/flex but after mobs = r/f 12 dgs and l/f 10dgs d/flex.
    She generally has a very symmetrical gait but the r/f heel strikes sightly to the medial side (genu valgum type) and pressure mat show little to no pressure on lateral f/foot from 3rd to 5th ray. Very high pressure on 1st mpj and hallux. Toe out r/f, straight ahead l/f. suspect internal femoral torsion ( internal hip rotation 60dgs external hip rotation 15dgs. No mall torsion.
    This results in functional hallux limitus. The right forefoot has a flexible supinatus and the 1st ray is very compliant to GRF. Therefore pronation continues thru gait and is maximum at late stance phase with only little resupination in propulsion.
    STJ location is (on a scale of 1-3) laterally deviated 1. not rotationaly deviated.

    Left foot - the 1st and 5t rays are compliant to GRF and high pressure area is on the 2nd 3rd MPJs but not symptomology this side.

    My problem is: The supinatus f/foot needs posting until the supinatus drops out. However this may still aggravate FncHL.

    I could valgus post the F/foot with 1st ray c/o but at present I feel this will just aggravate late pronation until the 1st ray is able to p/flex.

    Rearfoot posting: Medial reafoot strike and medial weight bearing may indicate valgus post but this may increase pronation which is already 10dgs plus.

    Medial rearfoot post should reduce pronation, improve supination and f/foot loading but will exaggerate the f/foot supinatus and if I post the supinatus I am back to my first query.

    Can any one help here?

    Thanks in advance, Dave Smith.
  2. pgcarter

    pgcarter Well-Known Member

    When you say "valgus post the forefoot" do you mean raise the lateral side of the forefoot by wedging? and if so...why would you say this will aggravate pronation?..and do you mean pronation of subtalar joint?......can you explain further with a more detailed biomechanical description?
    regards Phill Carter
  3. Peter

    Peter Well-Known Member

    I put them into a laced shoe, with a forefoot rocker, then stiffen the midsole. Helps propulsion. might incorporate met dome/bar if necessary.
  4. Dikoson

    Dikoson Active Member

    Does the patient have an abductory twist secondary to functional hallux limitus?

    Have you thought of plantarflexing the first ray during casting??
  5. David Smith

    David Smith Well-Known Member

    Point 1 = yes. Point 2 because it will reduce supination moments by the f/foot about the STJ axis. since the STJ axis is Lateral (asssume lateral since there is resupination at propulsive stage) to the assumed CoP on the f/foot adding a forefoot lateral wedge will move the CoP laterally and reduce GRF applied supination moments.

    Yes forgot to mention that she does have abductory twist at heel off.

    I often or even usually plantarfles the 1st when casting but in this case the 1st ray is elevated in gait and is not able to plantarflex.
    I usually find in these cases it is best to varus post the f/foot (medial f/foot wedge) and review frequently. Ususally the supinatus drops out then one can reduce or c/o the 1sy ray. I also do activation/strengthtening exerscises fot the extrinsic muscles. This involves supinating (inverting) the foot, d/flex hallux and p/flex digits, then pronate (evert) foot, p/flex the hallux and d/flex the digits. Do this Non w/b then when proficient do it w/b. TRY it - it needs some practice usually.

    Cheers Dave
  6. Dikoson

    Dikoson Active Member


    A mortons extension may be of benefit in trying to get the 1st MTP functioning? Is it dorsiflexed or short and dorsiflexed?

  7. pgcarter

    pgcarter Well-Known Member

    One of the actions of a lateral forefoot wedge is to help plantarflex the first ray, as is the closed chain action of peroneus longus. The enhanced plantarflexion of the first met during stance usually corresponds with decreased pronation at the STJ. Oddly enough from my perspective this gap in comprehension seems to be English to some extent....we had an English chap out here as Dept head for a few years...he just would not or could not get past the simple single definition of either one side or the other of the STJ axis (too simplistic I think) and could not see the difference between open and closed chain function of peroneus longus. I frequently use lateral forefoot wedging to decrease pronation and to release functional hallux limitus...rather like a kinetic wedge but not always with the raise extending medially under the phalanges of the hallux.
    I definitely don't agree with medial forefoot wedging unless you have a static and permanent loss of function in either one or some joints....and are trying to stop consequent compensatory motion.....you prop up the first you are inviting loss of ability to dorsiflex the hallux...however you are "Johnny on the spot" for your patients and if what you do works for them then they'll be happy.
    regards Phill
  8. David Smith

    David Smith Well-Known Member


    Yes I agree with what you are saying ie that a lateral f/fpost can equal reduced midstance pronation. This is because the CoP is moved laterally and allow the the 1st ray to plantarflex earlier since there is reduced GRF on it.
    However in this case I was afraid that as there was no active plantarflexion available non-weight bearing ( the 1st ray can be passively p/flexed) then it would not p/flex in gait.
    I have now made the orthoses scanned w/bearing (Amfit) in the NCSP position and 1st ray p/flexed. 4mm reduction of medial arch, 4dgs med post rearfoot, 2dgs f/foot lateral post, lower 1st ray 4mm, met raise 2nd - 4th extended to cuboid (al a Kevin Miller). 3mm heel lift.

    This should reduce pronation at heel strike, resist over supination at mid stance ( genu valgum type gait) and of load the 1st ray which may be able p/flex earlier and remain stable to GRF.

    I'll let you know when fitted. Thanks for the input, Cheerio, Dave
  9. Mark2

    Mark2 Member


    Although you already have the orthoses in production, have you tried low dye strapping with felt paddding 2nd-5th MTPJ and felt lateral wedging? I tend to do this to see if these features reduce symptoms in an orthosis?
  10. efuller

    efuller MVP

    So, why does she have the neuritis?

    I can understand why you have pain sub mets 1 and 2. I'm not sure why you think it is the transverse ligament at the Mets though. But what do you think causes the neuritis?

    Your measurements show high pressure sub medial forefoot. This high pressure could directly cause increase stress on the plantar structures of the first and second metatarsal. However, I would think the structure involved would more likely be the sesamoids or plantar capsular attachments of the plantar fascia as opposed the transverrse metatarsal ligamements.

    Is the neruitis a typical localized (pair of ) neuromas or caused more proximally at the tarsal tunnel?

    How do your measurements above address the neruitis complaints.

    The valgus forefoot wedge: I believe there are couple mechanism by which this can reduce late stance phase pronation. The wedge eliminates late stance phase pronation by everting the foot further. If you are at the end range of motion of the joint there can be no further pronation. Or the wedge can increase the pronation moment by placing the center of pressure more lateral to the axis. This will make the joint more "stable" in regards to the liklihood of STJ inversion. I believe one cause of late stance phase pronation is the action of the peroneal muscles in response to inversion instability. This is a central nervouse system mediated response to foot mechanics.

    I did a presentation on peroneus longus function at PFOLA a few years back. In that presentation I showed a mechanical model that demonstrated the possible effects of peroneus longus with varying STJ axis position. With the more medially deviated STJ axis position the peroneus longus caused pronation of the STJ and the eversion of the STJ increased ground reactive force under the first met head and there was dorsiflexion of the first ray. With an average axis of the STJ there was eversion of the STJ and no motion of the first ray. With an extremely laterally deiviated STJ axis there was plantar flexion of the first met and supination of the STJ. The foot described above does not match a severly laterally deviated STJ axis foot. The laterally deiviated STJ axis foot is unlikely to have a supinatus. The lightest touch on the medial forefoot will cause the STJ to supinate and not medial forefoot dorsiflexion (aka LMTJ supination).

    So, one of my conclusions in that PFOLA talk is that position of the STJ axis is very important for determining foot function. Where is the axis in your patient?

    Back to the valgus wedge:
    It makes perfect sense in terms of the pressure mat readings. Bring the ground up to the foot so there can be some load on the lateral forefoot and decrease the load on the medial forefoot.

    Yes, this valgus wedge will increase the pronation moment on the STJ, but pronation moment is not causing the symptoms in this patient. High loads under the first and second mets are causing the symptoms.

    If you see resupination after using a forefoot valgus wedge it is more likely the result of the posterior tibial muscle activity (supination moments) than it is peroneus brevis muscle activity. So, a valgus wedge will cause the pronation moment, but there may be a net supination moment because of increased activity of the posterior tibial muscle. The resultant motion has to be explained by the net moment.

    Peroneus longus is one complex muscle.


    Eric Fuller
  11. David Smith

    David Smith Well-Known Member


    I understand your method but I usually fight shy of using temp orthoses or diagnostic padding. The reasons for this are two fold;

    1: if the temp appliance doesn't work the patient loses confidence in the ability of the orthoses to work. If they decide to go on to bespoke orthoses this can result in lack of compliance and a focusing on negative instead of positive aspects of the treatment as a whole.

    2: The temp appliance may be 'working positively' but may not change positional appearance of foot and may not reduce symtoms immediately.
    How long does one continue to use a temp appliance before deciding that it has not worked. Does this necessarily mean the bespoke orthoses will not work. No of course not but what then? If you use a temp device to prove the diagnosis and it doesn't can you then ethically fit a bespoke orthosis?


    Yes you raise some good points and they are exactly the reason why I find this a difficult prescription.

    1 Met pain:
    The signs of Mortons Neuroma in this pt. are tender to squeeze between 2nd 3rd interspace with jump response, also pain on lateral compression of mets.
    1st interspace pain is tender on palpation put not sharp pain and is made worse by separation of the joint but not compression. There is no pain on passive or active full RoM or diresct palpation of plantar aspect of 1st met, which might be expected with a capsular or sesamoid eitiology.

    The reason for neuroma may not be classic but may be lateral translation of the mets as the f/foot abducts on the rearfoot and the medio-lateral force applied by GRf at the 1st 2nd met heads.

    Intermetatarsal ligament strain may have occurred because of excessive separation of the met heads 1 and 2 because of the compliance of the 1st ray to GRF.

    2 Peroneal action:
    Eric I agree with your model and it makes perfect sense that the effect of peroneal action is altered in relation to STJ position.
    However in my pt. the STJ, non-w/b, is definitely translated lateral 1 (on a scale of 1 – 3 where 3 is most translated) There is no change in rotational position and the projection exits thru the 2nd interspace. W/b the rearfoot is pronated 10dgs and the f/foot bears little weight on the lateral rays 3-5. It is however easy to supinate the foot with pressure applied to the MLA and by d/flexing the hallux. I agree that the features seem mutually exclusive, but there it is anyway.
    It may be that the genu valgum and toe out type stance creates a posterio-lateral acting horizontal force (-x in terms of the local axis set) which may produce pronation moments about the STJ.
    The ligaments are lax and allow a large and compliant RoM of inversion and so the small pronation moments acting about the STJ may be sufficient to cause a large pronation motion.
    This may well be easily overcome by force applied medially and so supination is easily caused.

    Could there be weakness in the posterior tibialis? I will need to re-check this.

    3Valgus post:
    “Yes, this valgus wedge will increase the pronation moment on the STJ, but pronation moment is not causing the symptoms in this patient. High loads under the first and second mets are causing the symptoms”.

    I think you are quite right Eric. This is the conclusion I have come to and have designed the orthoses to address this problem.

    “The resultant motion has to be explained by the net moment.”

    Of course you are correct but the problem is defining how the net moment is produced and as in this case it is not always clear.

    Ah yes! Eric to get the right answer first we must ask the right question, which I think you have.

    Thanks a lot Dave
  12. efuller

    efuller MVP

    My working theory, and I'm not that proud of it, is that a neruoma can be made worse by the grinding the met heads into the ground with an abductory twist. Orthoses help by reducing the abductory twist. I am willing to discard the theory if someone comes up with a better one. Any takers.

    I'm still having a hard time with the idea of transverse intermetarsal ligament strain. I had this one patient, in my residency, who when standing and I attempted the Hubscher maneuver the first meteatarsal head became medially promement by about a cm. That was the patient who started me thinking about dynamic gait. She did not have sub firtst pain, she had medial bump pain. Every step her transverse ligament would be strained. You may be right, but I'm still skeptical.

    There are some rare feet that have very lax ligaments and who have a laterally deviated STJ axis. They have a floppy foot and tend toward ankle sprains and easy supination.

    You don't need to get into horixontal forces to explain what is happening. The horizontal forces are extremely small when compared to the vertical forces. In stance with the floppy foot the center of pressure may be very close to or beneath the STJ axis so the pronation moment from ground reaction force would be small and easily overcome by upward force in the arch or activation of the windlass.


  13. David Smith

    David Smith Well-Known Member


    Plantar digital Neurosis, Mortons Neuroma: I had a read up to see what the general consensus is but it appears that the pathophysiology of this condition is unclear. (compression by constictive footwear seems popular especially amongst orthopeadic surgeons.) The most agreed upon aetiology seems to be mechanical aggravation of the nerve. Reasons vary from bursa enlargement, entrapment by intrinsic muscles, pressure between ground and metatarsal due to loss of fat pad and / or compliance to GRF of 1st and 5th rays / collapse of the transverse arch. Translatory or shear forces between the metatarsals and many seem to conclude the transverse metatarsal ligament impinges on the nerve. It is apparent that enlargement of the nerve is not always indicative of symptomology and sometimes nerves with normal appearance are symptomatic.
    I think the causes may in fact be any or all of the above and certainly for most (in my experience) a simple met dome will have good results if not complete resolution. This might indicate that generally there is some impingement trauma. Some cases are not so simple and it may that to achieve resolution it be more important that the clinician has a good grasp of anatomy and the individual patient’s biomechanical variations so that it is possible to determine the pathophysiology for that individual.

    I would agree that if the pt. has neuroma 2nd 3rd interspace then usually one would see high pressure area sub 2nd 3rd mets, excessive late pronation and abductory twist. This pt. has the latter 2 but high pressure is sub 1st 2nd met heads. There will still be translatory motion and shear forces between the mets as the forefoot abducts and adducts on the rearfoot.
    There are no plantar callosities on either foot and perhaps it is entirely possible that the r/foot was like the left foot with compliant 1st and 5th and high pressure 2nd 3rd met heads. Now, as an antalgic response to the pain, pronates maximally to partially relieve the pain.
    The left foot is more typical of the mortons neuroma type foot but is asymptomatic.

    I need to spend some time to reply to your Horizontal forces statement since this needs careful consideration and explanation. I have done some research comparing force actions in terms of global and local axis and it is quite surprising how when considering local axis sets the outcomes are entirely different to intuitive assumptions.

    Thanks for your replies Eric

    Respectfully Dave Smith

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