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Forefoot varus post and Hallux Rigidus

Discussion in 'Biomechanics, Sports and Foot orthoses' started by JRAD, Apr 29, 2013.

  1. JRAD

    JRAD Member


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    I am hoping someone can offer they're experienced comments or suggestions for a patient I just saw today who is a young female runner (29 years old) that recieved some functional foot orthosis for the treatment of IT band syndrome about 5 years ago .
    The main correction that stands out in her current orthosis is a substancial forefoot varus posting, bilateral, of about 5 degrees which is extended from the distal edge of the orthosis to the toe.
    These have been effective for her.
    My question is that upon examination I noticed that she had some significant structural Hallux Rigidus which she claimed has developed recently.
    Has anyone had this experience of forefoot varus posting contributing to reduced ROM in the Hallux?
    I've really only used this type of posting for Posterior Tibial tendonitis and most of these patients already have Hallux Rigidus!
    Patient is very active and an M.D. and I'd like to avoid any further problems for her.
    Thanks for your suggestions.

    J.R. C. Ped.
     
  2. s.miles

    s.miles Welcome New Poster

    This posting sounds like its inhibiting plantar flexion of the 1st met. This is needed for the posterior dorsal shift of the transverse axis of the hallux. Without this shift the dorsal aspect of the proximal phalanx will collide with the met head and over time arthritic changes will occur leading to a loss of range of motion . An educated guess ?
     
  3. s.miles

    s.miles Welcome New Poster

  4. LuckyLisfranc

    LuckyLisfranc Well-Known Member

    I routinely use a forefoot varus post/wedge once osteoarthritis is significantly established within the 1st MTP joint (Grade 3+), and there are solid clinical signs of 1st MT elevatus and hallux equinus.

    Once those changes are well established and the OA is well advanced, then you have lost the battle with encouraging ROM, and the IP joint has now become the main contact point for the medial column, rather than the 1st MT head - which is now 'up in the air'. If you can also see x-ray evidence of sesamoid disuse atrophy (ghosting) then the joint is not functional anymore, IMHO.

    Hence, bring the ground up to meet the foot. But do it too soon (ie Grade 0,1,maybe 2), and you will certainly encourage more dorsal impingement.

    LL
     
  5. Lab Guy

    Lab Guy Well-Known Member



    For running, a forefoot varus post makes sense as the limb is in varus since the stance foot is under the CoM to maintain balance and forward progression. Her running limb varus will cause the CoP to be lateral to her STJ axis creating a pronation moment. A forefoot varus post will bring the ground to the medial forefoot to decrease the duration of the STJ pronation motion and prevent overuse symptoms as well as possible Iliotibial band syndrome.

    In Walking, the CoM is between the feet for balance so the forefoot varus post is not necessary. The varus post will cause a dorsiflexory moment to the first metatarsal which will resist the Plantarflexory moment of the medial fascia band as it tries to plantarflex the first metatarsal head. This will limit motion at the MPJ during propulsion much like a Morton's extension will.

    Lucky Lisfranc gave good advice, and varus posting or a Morton's extension is helpful if there is OA or pain on ROM. If she really has a functional hallux limitus and there is no pain on ROM or end ROM, you can take a cast with care to ensure the first metatarsal is not dorsiflexed negating the need for a first ray or first met cut-out. You want to keep the MLA intact to limit the STJ pronation to decrease the GRF acting plantar to the first MPJ especially if her first ray DF stiffness is low.

    Your patient is only 29 so if she has a severe structural hallux limitus (less than 10 degrees of dorsiflextion from the transverse plane of the heel and first MPJ) than she should pick another sport other than running. This problem also takes time to develop and she probably has a history of injuring her joint when she was younger.

    Find a Podiatrist with an interest in biomechanics and sports medicine that you can work with. She should have radiographs to see what is going on. If you do not have them, Kevin Kirby's biomechanics books are an excellent addition to your library.

    Steven
     
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