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Cavus Foot that pronates?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by David Wedemeyer, Oct 16, 2008.

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  1. David Wedemeyer

    David Wedemeyer Well-Known Member


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    I am wondering how often any of you encounter a patient with a somewhat rigid cavus foot that is a pronator?

    I evaluated a woman who has cavus feet and a good degree of rigidty in the midfoot the other day. She was referred by her foot & ankle orthopedist for orthoses. She has a history of bunionectomy on the right foot and now the 2nd MTP joint of that foot is painful but not tender. The second met is slightly elevated.

    She also has a past history of plantar fasciitis and now reveals first step pain on the left and medial band tenderness at the plantar fascial origin calcaneus.

    The right MTP is 10 degrees of dorsiflexion and the left is 40, so Hallux Rigidus/Limitus is an issue. Her heel is not in varus as I would expect as she does have a mild bilateral forefoot valgus. The calcaneus appears uncompensated to her forefoot valgus.

    The odd thing about her presentation is that during midstance she has a remarkable level of pronation moment and her STJ axis is medially deviated. There is no significant tibial varum or femoral internal rotation or limitations.

    I opted to afford her my standard PT regimen for acute PF; interferential muscle stim via a garment sock, subaqeous ultrasound diathermy and myofascial release and she reported a significant reduction in symptoms post treatment. I am asking her ortho to consider a script for PT and to suggest an OTC or heat moldable insert with a cookie under the second met initially along with the appropriate running shoes. She may need a Morton's extension but I haven't casted her yet or considered custom orthoses until I've thought this out further.

    She is an avid runner and I (as did her ortho) asked her to curtail running for now.

    Any thoughts, comments or ideas are appreciated.
     
  2. efuller

    efuller MVP

    Re: Cavus Foot


    Hi David,

    The high arched medially deviated STJ axis foot is less rare than the flat flexible foot with the laterally deviated STJ axis. You will see both if you look for them. Now that you found it, treat it as if it has a medially deviated STJ axis.

    OTC devices for a foot with a high arch in stance may not be too helpful. I find that OTC devices have a slightly below average arch height (not scientifically measured) so the chance of arch contact with the device is low. You could spend some time adding cookies and adhesive felt to make a higher arched device, but it may not be worth your time.

    One of the major causes of pain in high arched feet is the lack of any weight bearing of the midfoot. Area of contact is smaller so pressures are higher in the areas that do contact. This is one of the foot types I would bet custom devices do better than OTC devices.

    Cheers,

    Eric Fuller
     
  3. Admin2

    Admin2 Administrator Staff Member

  4. David Wedemeyer

    David Wedemeyer Well-Known Member

    Re: Cavus Foot

    Eric,

    Thank you for responding. I am in a quandary as to what to do with this patient to be honest. Reading the old posts that Admin supplied on the cavus foot has been a great deal of help though (thank you Kevin).

    I agree after stepping away from her findings for a couple days, reading your post and and reevaluating my findings that she will possibly need a more flexible functional custom device with a medial skive etc. and that an OTC may be a waste of time.

    I plan on posting my findings in full and typing out loud here so that I can have the added benefit of all of your experience as I go through the process of casting and fitting her. Its a really good opportunity to use the experts as a sounding board and to reason out and rationalize the methodology and goals for this patient.

    Regards,
     
  5. Adrian Misseri

    Adrian Misseri Active Member

    I evaluated a woman who has cavus feet and a good degree of rigidty in the midfoot the other day. She was referred by her foot & ankle orthopedist for orthoses. She has a history of bunionectomy on the right foot and now the 2nd MTP joint of that foot is painful but not tender. The second met is slightly elevated.
    The right MTP is 10 degrees of dorsiflexion and the left is 40, so Hallux Rigidus/Limitus is an issue. Her heel is not in varus as I would expect as she does have a mild bilateral forefoot valgus. The calcaneus appears uncompensated to her forefoot valgus.

    G'Day David,

    Interesting case, nice one to post up here!

    From what you've suggested, it would seem that the issue seems to be a re-enforcing saggittal plane block cycle. There is a medially deviated STJ axis, which is causing an excessive pronatory moment at midstance, which potentially is causing elevation of the first ray, potentially jamming the 1st MTPJ, thus potentially contributing to the hallux limitus, which then potentially contributes to the pronatory moment as propulsion is affected, and all the while the windlass mechanism is failing and the plantar fascia is coping the bad end of the stick and getting strained. Potentially....... :eek:

    The fact that you are dealing with a cavoid foot I'd imagine is making teeh situation more difficult. As there is reduced motion at the midtarsal complex, smaller movements at these joints can equate to larger magnitude forces, as it takes a shorter time to get to a position of excessive pronation, thus possibly more time in the excessively pronated position, shorter time of shock attenuation therefore higher magnitude of forces (impulse = (force x area)/time) etc. etc.

    As suggested, I'd be treating it as a medially deviated STJ axis, and just considering that the supinated foot is just the foot's 'normal' position, manage the foot as a restricted ROM type foot, and go with custom devices.

    Good Luck!
     
  6. deco

    deco Active Member

    Hi David,

    Can you post a picture of her feet?

    Thanks

    Declan
     
  7. David:

    As Eric mentioned, a cavus foot can have a medially deviated subtalar joint (STJ) axis, but it is relatively uncommon. One characteristic of the foot with a high medial longitudinal arch is that these feet will also have a higher pitched STJ axis within the sagittal plane so that the distance from the ground superiorly to the STJ axis is greater (at the level of the metatarsal heads) than what would be present in the lower arched foot that has a lower pitched STJ axis.

    This higher pitched STJ axis will have a very significant effect on producing increased magnitudes of STJ pronation moment (or STJ supination moment) when acted upon by medial-lateral shearing forces due to the longer moment arm from the plantar forefoot to the STJ axis for ground reaction force (GRF). For example, a laterally directed shearing GRF acting on the plantar forefoot of a foot with a cavus foot (high-pitched STJ axis) will produce more STJ pronation moment than the same laterally directed shearing GRF acting on the forefoot of a planus foot (low-pitched STJ axis).

    Due to the characteristic kinematics of pronation motion in a cavus foot, it is imperative, if STJ pronation moments are determined to be the cause of the patient's pathology, that an anti-pronation foot orthosis for a cavus foot be constructed with a well-formed medial longitudinal arch contour. Since these feet also tend to have a very prominent medial band of the plantar fascia (MBPF) during weightbearing, then one can not simply make a "Spike-thotic" (ala Sole Supports) with a minimal arch fill on the positive cast, or the patient will invariably develop irritation to the MBPF from the orthosis.

    Therefore, to make a comfortable and therapeutically effective orthosis for a cavus foot that has symptoms related to increased STJ pronation moments, I will design the orthosis as follows:

    1. Balance the positive cast 2-5 degrees inverted.

    2. Add a 3-4 mm plantar fascial accommodation into the positive cast.

    3. Use minimal medial expansion plaster thickness.

    4. Use 2-3 mm medial heel skive.

    5. Use 3/16" polypropylene with 4/4 degree rearfoot post, 16-18 mm heel cups and will use a full length topcover if patient is involved in sports.

    I would avoid a Morton's extension unless the patient had a anatomically shortened or elevated first metatarsal head and had clinical evidence of increased GRF plantar to the 2nd metatarsal head.

    Hope this helps.
     
  8. PodAus

    PodAus Active Member

    Any other symptoms of Charcot Marie Tooth Disease?
     
  9. Re: Cavus Foot

    The high arched interpod OTC is reasonably high and has a plantar fascial accommodation.
     
  10. David Wedemeyer

    David Wedemeyer Well-Known Member

    Kevin,

    Indeed this does help and a great deal. Thank you. After rereading the posts on the cavus foot I had come to a similar plan for her orthoses. I actually feel as though I have learned some things by participating in the Arena!

    I will try and post some pictures of her feet soon.

    She does not have any clinical indications of CMT PodAus. She is an otherwise very healthy individual.

    Adrian thank you, yours and Eric's posts got me thinking about "moments" and tissue stress not just the arch height. Kevin's confirmed my thought process was on the right track.

    No we will not be using an Ed Glaser device on this patient ;). I have actually set up a small lab in my garage and hope in time to be making all of these devices on my own. I've found that I have more control over the process and that true to my Germanic heritage am a mad tinkerer.

    Simon is the Interpod heat moldable? Do you have a link for future reference?

    Regards everyone and thank you for your great help and interest,
     
  11. Jeremy Long

    Jeremy Long Active Member

    I tend to follow Kevin's device path when I come this type of patient. The only real difference is the shell material. Particularly with athletes I find greater favor in using TPE (thermoldable polyethylene). This has a dynamic quality to it that poly-pro doesn't do quite as well, and it can be further tweaked through thoughtful external fill to the shell with a variety of moldable foams. I don't use this technique as often with runners as often as I do with athletes engaged in sports requiring more medial-lateral motion.
     
  12. David Wedemeyer

    David Wedemeyer Well-Known Member

    Jeremy,

    Good to see you posting on here. I hope to see more posts from you as your experience and acumen in orthoses and footwear is exceptional.

    I should be seeing this patient within the week and will try to post her history and either pictures or a clip of her gait for comments.
     
  13. David Wedemeyer

    David Wedemeyer Well-Known Member

    I was contacted yesterday by this patient to inform me that she is going against her ortho's opinion and my recommended treatment. Apparently she met a colleague of mine at the gym who informed her that this is all due to her low back being out of alignment :bash:

    This is in spite of the fact that she has no low back pain, no subjective symptoms that would lead either her ortho or myself to believe that this is a more proximal etiology. She also denies any previous low back history, numbness, tingling or shooting pain in a dermatomal pattern into the foot. There are NO objective findings that this is spinal related whatsoever.

    Personally I feel that the poor economy has reared its ugly head and she found a provider in-network with her PPO who told her what she wanted to hear, who is closer to her by 5 miles and who probably will also offer her a Foot Leveler to 'align' her feet and spine at a reduced rate. I bet on it.
     
  14. Jeremy Long

    Jeremy Long Active Member

    Okay David, just because I know you're also too nice to bring it up, I'll offer the other, unmentioned reason: the predatory efforts of some within your particular arm of the allied health fields. Then again, with numerous examples among the various arch support shopping mall brothels, my profession has not exactly been a benchmark for ethical teamwork. So sad, and and unnecessary.
     
  15. David Wedemeyer

    David Wedemeyer Well-Known Member

    Jeremy are you suggesting covert predation using specious and fallacious claims for financial gain by some musculoskeletal Rasputin?

    I cannot add to your description of retail spudorthics. Simply lexicographically surfeit in its elocution!
     
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