Welcome to the Podiatry Arena forums

You are currently viewing our podiatry forum as a guest which gives you limited access to view all podiatry discussions and access our other features. By joining our free global community of Podiatrists and other interested foot health care professionals you will have access to post podiatry topics (answer and ask questions), communicate privately with other members, upload content, view attachments, receive a weekly email update of new discussions, access other special features. Registered users do not get displayed the advertisements in posted messages. Registration is fast, simple and absolutely free so please, join our global Podiatry community today!

  1. Everything that you are ever going to want to know about running shoes: Running Shoes Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
  2. Have you considered the Critical Thinking and Skeptical Boot Camp, for taking it to the next level? See here for more.
    Dismiss Notice
  3. Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
Dismiss Notice
Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
Dismiss Notice
Have you liked us on Facebook to get our updates? Please do. Click here for our Facebook page.
Dismiss Notice
Do you get the weekly newsletter that Podiatry Arena sends out to update everybody? If not, click here to organise this.

Acquired metatarsus adductus

Discussion in 'Biomechanics, Sports and Foot orthoses' started by David Smith, Nov 30, 2013.

  1. David Smith

    David Smith Well-Known Member


    Members do not see these Ads. Sign Up.
    Its only me!

    Hi Guys

    Reference the attached pictures: For this type of foot, which I call an acquired metatarsus adductus, (McGlamry's calls this Compensated Met Add) I often find it difficult to decide on what design to prescribe in an orthosis.

    [​IMG]

    In this case the guy complains of very painful 1st MPJ. He reports that the feet have changed shape over the last few years as the 1st MPJ pain has got worse.
    He is 46 years old, 100kg b/w 180cm tall. no significant med hist.

    He has no rearfoot to forefoot variations, STJ axes are central, good ankle dorsiflexion RoM, compliant frontal plane midfoot RoM, normal STJ RoM, slightly inverted STN. compliant 5th and 1st rays. Light to medium supination and jacks test. restricted hallux/1st MPJ dorsiflexion RoM (only about 10dgs till painfull)

    In stance the 1st MPJ bears little weight. In walking my iPhone video (http://www.coachseye.com/oydH) shows that the hallux is dorsiflexed in stance and the IPJ is dorsiflexed in propulsive phase, the lesser toes take a varus rotation to give more leverage to resist STJ pronation while off loading the 1st MPJ. I think this adduction technique is the reason for the acquired Met Add foot shape.

    My quandary is whether to accommodate the adducted forefoot position or to make and orthosis that abducts the forefoot while both would off load the 1st MPJ and reduce hallux dorsiflexion moments. I.E. The former with medial rear and forefoot posting would tend to increase the forefooot adduction and the latter with lateral forefoot posting would tend to abduct the forefoot but can this deformity be reversed?

    any opinions here?

    Regards Dave Smith

    [​IMG]

    [​IMG]
     
    Last edited: Nov 30, 2013
  2. Dave:

    Your patient definitely has a medially deviated subtalar joint (STJ) axis on the right foot. On the left foot, the STJ axis looks slightly medially deviated during relaxed bipedal stance. Unfortunately, you didn't tell us which side is symptomatic...right or left or bilateral?

    The foot you show here is what was often called a "Skewfoot" or "Z Foot" due to a pronated rearfoot coexisting along with a metatarsus adductus deformity. To call this foot's metatarsus adductus deformity "compensated" or "acquired" is, in my opinion, erroneous. It is best to say what the foot is, pronated at the rearfoot with a metatarsus adductus deformity, and not try to guess as to how the foot got that way.

    Your goal with foot orthosis therapy should be to:

    1.Reduce the ground reaction force (GRF) plantar to the 1st metatarsophalangeal joint (MPJ) to reduce the 1st ray dorsiflexion moments during the latter half of stance phase which will, in turn, reduce the 1st MPJ intra-articular compression forces which are the likely cause of the patients pain. [However, if the patient has pain at the end of 1st MPJ dorsiflexion in non-weightbearing exam, you may need to consider, instead, using the orthosis to immobilize the 1st MPJ (e.g. using a Morton's extension)].

    2. Improve the function of the patients gait.

    3. Prevent future foot and lower extremity pathologies from developing.

    From the information you have given us I would order an orthosis with a 5 mm polypropylene shell foot, a 16 mm heel cup, 2 mm medial heel skive, 2-3 mm heel contact point thickness, 1-2 degree inverted balancing position, and a 3 mm korex (or EVA) reverse Morton's extension for this patient. You must be careful, however, in making sure the orthosis doesn't over-invert the foot which the patient will report as lateral instability. Therefore, the above orthosis prescription may need to be modified with reduced medial arch height (use normal medial fill vs minimal medial fill in positive cast) or a vertical balancing position (versus an inverted balancing position).

    A foot orthosis has no ability to reduce this patients adducted forefoot position. This should not be one of your orthosis goals since foot orthoses have no mechanical advantage to abduct the forefoot on the rearfoot (i.e. exert an external forefoot abduction moment). The only thing that will reduce this patient's adducted forefoot position is foot surgery which no ethical foot surgeon would suggest doing for this patient. However, this patient may eventually need 1st MPJ surgery for their 1st MPJ pain which is likely being caused by progressive degenerative joint disease in the 1st MPJ.

    Hope this helps.:drinks
     
  3. Lab Guy

    Lab Guy Well-Known Member

     
  4. David Smith

    David Smith Well-Known Member

    Thanks for you replies Kevin and Steve, I'll will hold off replying until I've next seen this guy and can review his feet in terms of the queries you've raised.
    Kevin, Both feet have the same painful symptoms in 1st MPJ and the hallux extensor tendon (EHL) along the 1st ray (I missed that bit from my last post didn't I).
    Steve I'm confident that I can design an orthosis to reduce painful symptoms but I am exploring how to make the best orthoses for this patient.

    Many thanks Dave
     
  5. Dave:

    You may consider that the patient is using his extensors (including the EHL) to try and supinate the foot off of the 1st MPJ. This is not the normal compensation for 1st MPJ DJD but I have seen it before. A test that you may want to do is the Maximum Pronation Test to see how close the feet are to the maximally pronated position. Also try to assess if the patient is walking with the foot more supinated than normal in his attempt to unweight the painful 1st MPJs. This is a very common gait compensation for 1st MPJ DJD.

    Good luck.:drinks
     
  6. David Smith

    David Smith Well-Known Member

    Yes he does Kevin, this elevates the 1st ray and supinates the f/foot as you suggest and I would say that he does attempt to supinate (i.e. not max pronated thru stance phase) the STJ as long as possible in order to off load the 1st MPJ

    Cheers Dave
     
  7. David Smith

    David Smith Well-Known Member

    Steven You wrote

    Steven
    Thanks for your input, does this update change your thinking at all?

    Regards Dave Smith
     
  8. David Smith

    David Smith Well-Known Member

    Sorry tha link to that video clip is here http://www.coachseye.com/QCzt

    Admin can you delete or replace that link to webmail.foothouse on my last post, I've lost the option to edit that post now

    Cheers Dave
     
  9. Lab Guy

    Lab Guy Well-Known Member

    Hi David,

    Thanks for the update.

    I no longer think your patient has a Skew left foot. The left foot does indeed to appear pretty normal with the foot in NCSP. I would have expected the forefoot to be very adducted without MTJ and STJ pronation to bring the forefoot to a more rectus position.

    Your new video shows very good ROM in all three planes. I was surprised how much ROM in the direction of DF the first MPJ had. I had wrongly thought that your patient had structural hallux limitus rather than functional hallux limitus. It appears he has ligamentous laxity of his plantar ligaments with decreased DF stiffness of his 1st ray. Not much force is needed to load his forefoot on his rearfoot or load the first ray.

    In the Lunge test of the right foot, I would have expected his foot to be a greater distance from the wall with a higher angle between the lower leg and wall as the gastroc is off stretch. The right foot is certaintly pronated in the photo with loss of the MLA and MPE.

    You wrote that the first MPJ is painful bilateral and I am unclear as to why the right foot is more pronated than the left. He appears to be supinating more on the left foot to off-load the first mpj which corresponds to your pressure mat analysis.

    I do now think he has a chance of getting relief with orthotics but I am guarded. Kevin's orthotic prescription is on target as usual. His shoes seen in your photo are not supportive and Hoka One shoes may benefit him as they have a forefoot walker. They have helped me personally with my own DJD of my 1st MPJ.

    You do a great work-up and you know your patient best. In view of all the information, I think you have a good chance of helping this patient with orthotics in a good pair of shoes to prolong or avoid surgical intervention.

    Steven
     
  10. David Smith

    David Smith Well-Known Member

    Thanks Steve and Kevin

    Talking that case thru helped to sort the wood out from the trees. I think my prescription is going to be very similar to Kevin's suggestion except I'll use a milled EVA device.

    Merry Christmas Dave :santa:
     
  11. Lab Guy

    Lab Guy Well-Known Member

    "and Hoka One shoes may benefit him as they have a forefoot walker."

    Besides my other grammar mistakes, I meant to write forefoot rocker, not walker.

    David, I wish you a merry Christmas as well.

    Steven
     
  12. Please let us know how your patient does in a month or two. Followup reports on these patients is extremely helpful for all those following along.

    Merry Christmas!:santa::santa2::drinks
     
  13. Dananberg

    Dananberg Active Member

    Hi All,
    Sorry to be late in the discussion, but have seen this type of foot many times in the past and have had most satisfying result outcomes.

    Kevin, regarding orthotic Rx, wrote: From the information you have given us I would order an orthosis with a 5 mm polypropylene shell foot, a 16 mm heel cup, 2 mm medial heel skive, 2-3 mm heel contact point thickness, 1-2 degree inverted balancing position, and a 3 mm korex (or EVA) reverse Morton's extension for this patient. You must be careful, however, in making sure the orthosis doesn't over-invert the foot which the patient will report as lateral instability. Therefore, the above orthosis prescription may need to be modified with reduced medial arch height (use normal medial fill vs minimal medial fill in positive cast) or a vertical balancing position (versus an inverted balancing position).

    When one reviews the mat scan of this patient, the above Rx would be acceptable for the R foot, but the L exhibits almost complete lateralization of the weight flow. Further inverting this foot is bound to exacerbate symptoms (and Kevin correctly alludes to this in the end of the Rx suggestion). Starting with a far more neutral RF post, with long type 1st ray cutout would be far more helpful. I would also carefully examine for LLD and likely add a small amount on the L heel.

    The other part of treatment not mentioned is manipulation of the ankle. When fibula translation is restricted, both ankle equinus (knee extended) and peroneus longus (PL) inhibition occur. This promotes greater inversion and greater 1st MTP joint jamming. With ankle manipulation, facilitation returns to the PL and balance to forefoot inversion:eversion. Plantarflexion of the 1st met is also improved once the PL is normally active.
    Good luck with this patient and happy holidays.

    Howard
     
  14. David Smith

    David Smith Well-Known Member

    Howard thanks for your contribution

    As Steve pointed out earlier I have the advantage of having 'hands on' this patient.
    Talking this over has been very helpful but my thinking is this:

    The STJ axes upon reviewing are more medial than I noted before (as Kevin thought) and of course the closed chain foot posture indicates more medial rotation of the STJ axes on w/bearing.

    The forefoot becomes much less adducted when the rearfoot is closer to vertical / STN.

    My guess is that originally the rearfoot pronated and loaded the 1st Ray causing FncHL causing the 1st MPJ to become enlarged with articular osseous deformation and so have restricted RoM that is now painful past 10dgs d/flexion. This resulted in an antalgic response, which was to supinate and adduct the forefoot in order to off load the 1st MPJ and reduce hallux dorsiflexion moments. This happend more on the left than the right and can be seen in the greater forefoot adduction observed and the lack of sub 1st MPJ forces left.

    As Howard has pointed out the weight bearing progression tends to be lateral. This is especially so on the left and is clear in the attached scan, however this is also true on the right foot and can be observed on other characterisations of plantar force progression from the AM3 scans. Below is the 3D characterisation at about 50% of stance phase

    [​IMG]

    I replied in the affirmative to Kevin when he asked does the rearfoot pronate less in gait than it does in resting stance, which is significant because this would indicate to me that there is a voluntary / CNS activated attempt to resist pronation with muscular action. This, combined with a voluntary response to supinate and adduct the forefoot to off load the 1st ray and, as Steve pointed out, reduce pronation moments about the STJ by reducing the moment arm available to GRF acting on the forefoot.

    Therefore, and remembering that the forefoot becomes less adducted when the rearfoot is nearer to STN/vertical, placing medial posting and not reducing the medial arch too much (not to much arch fill) will increase supination moments from orthotic reaction force and so allow the CNS to reduce muscular actions mentioned earlier.
    With forefoot medial posting full width and no 1st ray/mpj cut out or grind out and with the orthotic cut out under the hallux to allow a drop of which will effectively increase the functional hallux RoM available, i.e. acting like a rocker for the 1st MPJ thereby lowering the dorsiflexion moments in magnitude and time applied.
    Then the CoPP will be more medial without causing lateral instability and allowing
    a less adducted foot shape and reduce / stop pain in the 1st MPJ and EHL tendon.

    So the prescription is and EVA milled device with a 2dg full length ramp, a 3mm medial rearfoot skive, a 2dg medial forefoot post 2-5 right and full width left with the posting extended to the met toe sulcus. 2mm met dome 2-5 extended to the cuboid on both.

    It maybe that the elevated 1st ray may drop out after using the orthoses for a few weeks and then I will grind out the 1st MPJ/ray. I will add heel lifts as needed at fitting.

    Howard I haven't mobilised the foot and ankle because I thought there were very compliant RoMs in all foot and ankle joints and superior tib-fib joint so I don't think this is an issue but I will recheck at the fitting appointment.

    Great stuff cheers Dave
     
Loading...

Share This Page