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Orthotic prescription for hallux limitus

Discussion in 'Biomechanics, Sports and Foot orthoses' started by AdamB, Jun 9, 2013.

  1. AdamB

    AdamB Active Member


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    Hello,

    I have a question regarding orthotic prescription variables / modifications for management of structural hallux limitus.

    The patient is a healthy, fit and active 61 year old female with pain in the 1st MTP jt experienced during brisk walking (walks 2kms daily). Pain has slowly worsened in the past 2 years, but does not stop or limit activity.

    Exam reveals no significant biomechanical abnormalities aside from a slight reduction in 1st ray dorsiflexion stiffness and a reduced total ROM at the 1st MTP jt (approximately around 35* - 40* from memory). And a degree of functional hallux limitus determined by the Hubscher maneuver.

    Plain films reveal moderate joint space narrowing with subchondral sclerosis and dorsal osteophyte formation in keeping with moderate to marked osteoarthritic change. The other thing I noted on the lateral view was a relatively dorsiflexed 1st metatarsal with the base of the prox phalanx sitting slightly lower and not articulating in a totally congruent way.

    My treatment plan (lets call it treatment plan A) involved orthotic therapy with a Morton's extension under the 1st MTP jt to dorsiflex the met head and plantarflex the hallux and therefore reduce dorsal jamming of the joint during gait....

    However, I am now thinking that maybe I should have done the opposite (Lets call it treatment plan B) - an orthotic with a first ray cut out and a reverse Morton's extension to encourage plantarflexion of the 1st met head and facilitate better joint function and activation of the windlass mechanism?

    At what point of structural joint limitation do you stop trying to do treatment plan B and decide on treatment plan A??

    Thanks for any thoughts
     
  2. Re: orthotic precription for hallux limitus

    When plan B doesn't work ;)
     
  3. efuller

    efuller MVP

    Re: orthotic precription for hallux limitus

    One way to think about is: why does it hurt. One possibility is the compression of the 1st mpj from tension in the plantar fascia. So, even if there very little motion the compression of the joint can be reduced if the STJ is supinated and the load on the first ray is decreased. You could even put an orthotic with a reverse Morton's extension into a rigid rocker bottom shoe.

    I'm not sure of the logic behind putting a Morton's extension under a foot with 1st MPJ pain. Is this trying to create a rocker effect within the shoe? I can see putting a Morton's extension for 2nd ray pain in the presence of a low stiffness (dorsiflexed) 1st ray.


    Eric
     
  4. AdamB

    AdamB Active Member

    Re: orthotic precription for hallux limitus

    Thanks Simon, logical answer. :D
     
  5. AdamB

    AdamB Active Member

    Re: orthotic precription for hallux limitus

    Hi Eric, thanks for your response. Could you please explain a little further how tension in the plantar fascia could be causing compression of the joint?

    Yes, the logic I had in putting a Mortons extension under the 1st was to plantarflex the hallux so that when it did dorsiflex during gait it did so from a more plantarflexed position and therefore reducing the total dorsiflexion angle and dorsal jamming of the joint.

    Please correct me if I am wrong here.
     
  6. efuller

    efuller MVP

    Re: orthotic precription for hallux limitus

    Fuller, E.A. The Windlass Mechanism Of The Foot: A Mechanical Model To Explain Pathology J Am Podiatr Med Assoc 2000 Jan; 90(1) p 35-46

    The paper has some pictures of what I'll do quickly in words. The plantar fascia attaches to the base of the proximal phalanx and the tubercle of the calcaneus. Weight bearing will tend to increase the distance between those to points and this will make the plantar fascia tighter. When tight the plantar fascia will pull the proximal phalanx toward the metatarsal head causing compression of the joint. The tighter the fascia the more the compression.

    The more force under the first ray, the tighter the fascia will become. When the fascia is tight it will resist dorsiflexion of the hallux. So, a Morton's extension will tend to plantar flex the toe, but it will increase the resistance to dorsiflexion. You can see this easily when someone is standing by attempting to dorsiflex their hallux with and without a 3mm piece of cork under the metatarsal head.

    Eric
     
  7. Lab Guy

    Lab Guy Well-Known Member

    Re: orthotic precription for hallux limitus

    The more force under the first ray, the tighter the fascia will become. When the fascia is tight it will resist dorsiflexion of the hallux. So, a Morton's extension will tend to plantar flex the toe, but it will increase the resistance to dorsiflexion. You can see this easily when someone is standing by attempting to dorsiflex their hallux with and without a 3mm piece of cork under the metatarsal head.


    Eric, I agree with the above and please let me know if my thoughts are incorrect.

    Perhaps the Morton's extension is still causing high interosseous compression but it is also limiting joint motion. The limitation of motion is causing less jamming against the dorsal osteophyte (with possible fracture) and less inflammation in and around the joint secondary to an osteochondral fragment.

    I also agree that you want to keep the medial longitudinal arch high to take decrease the tension off the plantar fascia. Cast the patient with the MLA high and make sure the first metatarsal is not dorsiflexed even if you have to mildly dorsiflex the great toe.

    With a higher inclination angle of the first metatarsal, the medial band of the fascia has a longer moment arm (verticle distance from center of first MPJ to distance from center of first metatarsal cuneiform joint) to plantarflex the first metatarsal by producing a posterior force from the base of the proximal phalanx against the first met head. The windlass action of Hicks will be activated easier.

    With a lower inclination angle of the first met, the moment arm will be shorter, and there will be greater tension on the hallux, but the first met will dorsiflex much easier causing delay to absent windlass action of Hicks, jamming of first MPJ, Hallux limitus.

    That being said, taking a good cast is important. You want to control the MLA the best you can so that the GRF has a more difficult time to dorsiflex the first ray in stance.
    Therefore, some orthotic variables would be a wide shell, minimal cast fill, inverted cast pour, medial Kirby heel skive, and do NOT use a first ray cut-out.

    You do not want to sacrifice the MLA of the orthotic shell with a first ray cut-out as your goal is obtain maximum control. If you take a good impression, the shell will not be in the way of the first metatarsal head if it indeed plantarflexed.

    As Eric wrote, your goal is to use the orthotic to create an external supination moment or to reduce the pronation moment which would decrease the interosseous compression of the first MPJ. Your patient likely has an osteochondral defect, possible fracture of her dorsal osteophyte, and arthritis of her sesmoids/cristae which is not allowing full motion.

    To buy time, you may also wish to put her in Hoka running shoes. I have symptomatic Hallux limitus but my Hoka shoes have been the best shoes for running my 2-3 miles a day. The Hoka shoes have a forefoot rocker and wider outsole for stability. The midsole and outsole is airblown EVA and provides a lot of shock absorption. The apex of the forefoot rocker ends behind the First MPJ and the shoe is stiff when the forefoot of the shoe is dorsiflexed.

    Good luck,

    Steven
     
  8. AdamB

    AdamB Active Member

    Re: orthotic precription for hallux limitus

    Thanks Eric, that makes sense. But now I am confused because my patient has reported back to me saying that she no longer has any pain in the joint during her walking exercise with the Morton's ext under the 1st MTP jt.... does this mean that using the Morton's extension was the right treatment? Or should I have tried the reverse morton's to begin with to facilitate better joint function and reduce plantar fascia tension and reduce compression of the joint???

    Thanks,
    Adam
     
  9. AdamB

    AdamB Active Member

    Re: orthotic precription for hallux limitus

    Thanks Steven, your comment above reflects my train of thought. Perhaps that's why it worked and the patient no longer experiences pain in the joint when exercising.
     
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