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Orthotic prescriptions for offloading Right 5th MPJ?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by JonathanH, Nov 2, 2011.

  1. JonathanH

    JonathanH Member

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    Hi Everyone,

    I have been very thankful for all the information contributed by all in the forum, and would appreciate any thoughts on my current case.

    Male patient with a 8 month history of a recurring ulcer on his 5th MPJ. The site has healed but orthotics have been prescribed with aims to offload the site. He stands 8+ hours a day in mining boots.

    Significant clinical findings in the assessment includes:
    - restricted right rearfoot eversion ROM available during NWB exam
    - hypermobile 1st ray/reduced 1st MPJ stiffness when the right foot is loaded in NWB
    - low supination resistance of right foot compared to left
    - gait analysis shows excessive right foot supination during heel contact, midstance and at propulsion (so low-gear propulsion off the right 5th at propulsion).

    My initial plan with an orthotic device with:
    1. 0 degrees rearfoot posting
    (wouldn't a lateral wedge cause more irritation due to the restricted rearfoot eversion available?)
    2. 4-6mm EVA lateral arch support from styloid process of 5th to base of 5th MPJ
    3. forefoot - 1st to 4th MPJ with eva to accommodate the 5th?
    4. topcover - 3mm poron/cambrelle for additional cushioning

    What other strategies could be employed to offload the 5th MPJ?

    It's all from the top of my head but i will try to update with more clinical details asap! Thanks all for your time :)
  2. Jonathan your device sounds about right. I would probably look at a small lateral skive and the 4-6 mm lateral arch determine if this can be higher or not.

    The forefoot posting again as I would.

    You may want to investigate the covering material though - Shear and friction have been noted as a predisposing factor in diabetic ulcers . your cambrelle topcover may add to this.

    hope that this helps
  3. RobinP

    RobinP Well-Known Member

    I presume the ulcer is on the right 5th MPJ?

    I'd agree with Mike on this one. Sometimes having a cover like EVA with relatively high friction for the majority of the device and a very low friction cover over the localised area has reduced the recurrence of ulcers in some of my cases.

    If the contour of the device is relatively flat in the problematic area, a material like shearban


    can sometimes help to reduce friction enough.

    Good luck
  4. efuller

    efuller MVP

    It's good that you looked at eversion range of motion non weightbearing. However, you need to look at it weight bearing as well. Have the patient stand and ask them to evert. (see the maximum eversion height thread ).

    http://www.podiatry-arena.com/podia...php?t=69635&highlight=maximum eversion height

    There are two very different kinds of feet that will have high loads fifth met. There is the laterally deviated STJ axis foot that will have an easy supination resistance. This foot may have a large eversion range of motion, but sits inverted from maximally pronated. Then there is the partially compensated rearfoot varus foot. This foot will have no eversion range of motion. From your description I would lean toward the uncompensated varus foot, but you cannot be sure unless you look at the foot in stance.

    In the laterally deviated STJ axis foot a valgus wedge would be good, but not higher than the maximum eversion height. The wedge could end proximal to the 5th met head.

    In the partially compensated rearfoot varus foot: In stance try and place your fingers under the first and fifth metatarsal heads. In this foot the fingers under the 5th met head will get crushed and there may be very little force under the first met head. So, to reduce force under the ulcerated 5th met head, you have to put it somewhere else. A forefoot varus wedge may place more force under the medial forefoot. You could also get a nearly fully weight bearing foam box cast to capture the weight bearing plantar countour as accurately as possible and then fabricate a device that has an extra layer of thickness everywhere but the fifth met head.
    With that device you might need an extra depth shoe.

    Before you choose your prescription variables you need to know what kind of foot this is.

  5. Boots n all

    Boots n all Well-Known Member

    "recurring ulcer on his 5th MPJ."
    We are right in guessing you mean under and not on top of?

    For me besides the orthosis off loading, l would place on the lateral side of his boots sole a lateral flare from just proximal of the 5th mpj back to the heel.

    This will reduce/stop that supination moment by increasing the suprination resistance of the boot and moving some of that pressure further back a long the boot rather than the foot, this will especially be noticed when your client is pushing.

    Depending on how bad the problem is, you may even consider the lateral flare going up 1cm above the feather edge of the boot once you get past the styloid process of the 5th
  6. JonathanH

    JonathanH Member

    Thanks for the link to the thread. While the forefoot varus wedge may be helpful in placing more force on the medial forefoot, could this also:
    1. Supinate the forefoot and cause more WB on the 5th?
    (especially if there was a laterally deviated STJ axis?)

    2. disrupt the 'windlass effect' + Bojsen-Moller's "high-gear" with additional GRF on the right 1st MPJ?
    (i was also thinking of a 'met pad-like forefoot extension which supports the plantar aspects of the right 2-4 MPJs to allow 1st MPJ plantarflexion + 1st MPJ loading as well..?)

    sorry if it's not making much sense...the more i think about it the more i am confused!
  7. JonathanH

    JonathanH Member

    The ulcer was on the plantar aspect of the right 5th MPJ.

    Thanks for sharing your experience with Shearban.
    Would you also be aware of any information about the different friction levels of different top covers?
  8. Peter

    Peter Well-Known Member

  9. RobinP

    RobinP Well-Known Member

    I don't, but I believe Dr Spooner amy have just been doing a little work on the effects of top covers on friction. Perhaps he will come along and give you some information?

    The addition of a lateral float is a good suggestion for reducing the external supination moments
  10. efuller

    efuller MVP

    Think about force not position. If you get more force on the 1st met there has to be less force somewhere else. Total force = body weight) In a foot with an average or medial STJ axis position, I would not worry about this at all. In an extreme lateral position of the axis you may have the situation where the wedge might apply a small amount of force medial to the STJ axis to cause it to invert further. My sense it that the increase in lateral force with a varus forefoot wedge is theoretically possible, but highly unlikely.

    The pathology is under the 5th met head. Treat that. The evidence is that we have too much force under the lateral forefoot. We probably don't need to worry about overloading the windlass by increasing the force there.

    Do you mean 1st ray plantar flexion as opposed to 1st MPJ plantar flexion? The load is not really on the MPJ, but on the metatarsal head or the phalanx or both. In feet with a not fully compensated varus you may see the patient attempt to increase medial load by plantarflexing the MPJ to increase load on the hallux. However, this is usually form long and short flexor contraction.

  11. efuller

    efuller MVP

    I can see a flare working great for a foot with a laterally positioned STJ axis. The flare will position the center of pressure more lateral and will increase the pronation moment from the ground. This effect will be greater at heel contact when the foot is inverted and less pronounced, but still effective in stance.

    For the foot that lacks eversion (partially compensated varus), the lateral flare modification, will increase pronation moment, but the problem is lack of eversion range of motion. Increased moment will not get the foot to evert farther. It may even increase the duration of high pressure under the fifth met.

    There are feet that have lateral position of the STJ axis and lack of eversion range of motion. The lateral flare may help in that case. We need to know where the STJ axis is in this foot before we can be confident in our recommendations.

  12. Boots n all

    Boots n all Well-Known Member

    l agree it wont change eversion range of motion, didnt say it would, but l am not sure l see how it could increase the duration of high pressure under the fifth met either?

    Remember our colleague here has already off loaded to the best he can the 5th with his orthosis.

    But if you felt the duration of high pressure under the 5th was still an issue you can still off load the 5th even more, with the correct fulcrum of a rocker sole if need be.

    This is a client that l would fit up with the Fscan in-shoe system to see just what is happening with the pressure and line of trajectory, great little case study

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