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Flexor stabilization

Discussion in 'Biomechanics, Sports and Foot orthoses' started by 56Furman, Dec 11, 2013.

  1. 56Furman

    56Furman Member

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    A long time patient of mine returned to my practice complaining of red creases on her lesser toes (see attached photo). She had sought the care of a dermatologist prior to consulting who prescribed various cream which were no help. The creases are mildly uncomfortable and have only been present about 1 1/2 years.
    My patient has structural hallux limits. I have her wearing a rocker sole shoe with a functional foot orthotic that has a rear foot post and 4 degree medial skive, a reverse Morton's 2-5, and a 1st ray cut out since she has sesamoiditis. Presently she has no 1st MPT pain when ambulating only the mild less toe pain, which has improved slightly since she she started wearing the new orthotics and rocker shoe.
    Any ideas on how to manage what I think DIPJ irritation from excess flexor stabilization?

    Attached Files:

  2. Sicknote

    Sicknote Active Member

    Looks like an inflammatory/autoimmune disorder issue to me which notoriously affect the joints of the toes, especially when the temperature drops.
  3. efuller

    efuller MVP

    My theory on flexor stabilization is that the FDL muscle is a close second to posterior tib as best supinator. So, when a foot needs additional supination moment it will be recruited. Someone with hallux limitus pain can choose to supinate their STJ to "roll away" from the painful MPJ. So, that certainly is a situation where you might see additional supination recruitment.

    So, check post tib strength. Strengthen as needed. Check STJ axis location. If extremely medially deviated add varus wedge under rearfoot post to increase supination moment. It sounds like you are on the right track. It just might be that you have the optimum orthotic and it will take more time for the pain to resolve. The orthotic is not completely removing the stress on the effected tissues, it is just reducing it.

  4. 56Furman

    56Furman Member

    More history: The patient is a 67 y/o female. The flexor overactivity began after being treated for an ankle sprain by a foot orthopedist about 2 years ago. He sent her to his PT. They dispensed shoes that were too wide with only a single velcro strap closure, in my mind added to her sense of instability. The PT had her doing toe raises which the patient related caused pain, she continued to do them at home as instructed until I told her to D/C.
    Muscle strength 5/5 in, ev, pl and dorsi,
    I did add a 3 degree varus post along with the medial skive and 16mm heel cup.
  5. Lab Guy

    Lab Guy Well-Known Member

    It is rare to see extension of the distal interphalangeal joint (DIPJT) with flexor substitution. Usually you see flexion of the DIPJT as the FDL is plantarflexing the distal phalanx.

    Perhaps when your patient did those toe raises, she inadvertently tore the volar/plantar plate of the DIPJT creating loss of plantar stability explaining the dorsiflexion of the distal phalanx on the middle phalanx of digits 2,3 and 4.

    On clinical exam, why is the plantar distal phalanx of the 2nd, third and 4th toes not purchasing the ground? NWB in open kinetic chain, can the patient actively flex her toes so the distal phalanx is not dorsiflexed? Palpate the plantar aspect of the DIPJTS, is there tenderness?Does she have very elastic ligaments and tendons? I suspect something else is going on that needs to be identified.

  6. efuller

    efuller MVP

    I disagree with extension of the DIPJ comment. I can place my foot on the ground and contract my muscles and make my toes look just like the picture. I've made a toe model with tendons and with model on the ground I can make the PIPJ flex and raise the base of the intermediate phalanx which makes the distal phalanx dorsiflex relative to the intermediate phalanx.

    I'm looking at that picture and it appears that the 2-4 distal phalanges are purchasing the ground.

  7. Lab Guy

    Lab Guy Well-Known Member

    Eric, looking at the photo again and thinking about it, I agree with you. The foot has the signs of flexor substitution with adductovarus of 4 and 5, hammertoes and MPE. I was thrown off by the photo as it appears to me that the distal phalanx is much more dorsiflexed than normal causing the crease. However, looking at it, there is gripping of the digits at the level of the DIPJTS although to my old eyes, the distal end of the toes appear extended. But, it matters not as it can still be flexor substitution. I am just used to seeing the digits lie fully plantigrade distal to the DIPJT and not seeing creases on the dorsal DIPJTs.

  8. Furman:

    I can't agree that the positioning of the digits in your patient is caused by flexor digitorum longus (FDL) contractile activity since the FDL inserts on the distal phalanges and creates a plantarflexion moment at the metatarsophalangeal joint (MPJ), proximal interphalangeal joint (PIPJ) and distal interphalageal joint (DIPJ). Therefore, increased FDL contractile activity would tend to cause flexion at both the PIPJ and the DIPJ, not just the PIPJ.

    The central component of the plantar aponeurosis and plantar plates all insert onto the bases of the proximal phalanges so their passive tensile force causes a plantarflexion moment at the MPJ but no direct moments at the PIPJ or DIPJ of the lesser digits.

    The plantar and dorsal interossei and the lumbrical will cause a plantarflexion moment at the MPJ and dorsiflexion moment at the PIPJ due to their plantar orientation to the MPJ and and dorsal orientation to the PIPJ medial-lateral axis.

    The flexor digitorum brevis (FDB) however, causes a plantarflexion moment at the lesser MPJ and a plantarflexion moment at the lesser digit PIPJ since it's tendon inserts on the intermediate phalanx. (Kelikian AS (ed): Sarrafian's Anatomy of the Foot and Ankle: Descriptive, Topographic Functional. 3rd ed. Lippincott Willaims & Wilkins, Philadephias, 2011, pp. 586-593.)

    Therefore, when one considers all the structures which cause lesser digit plantarflexion moments at the MPJ and PIPJ, the only structure that can cause such a deformity as you illustrate in your photo (i.e. PIPJ plantarflexion and DIPJ dorsifexion) is the FDB since it is the only muscle that can plantarflex the PIPJ without also simultaneously plantarflexing the DIPJ. The FDL cannot cause such a deformity. My guess is that the dorsiflexion of the DIPJ is being caused by ground reaction force acting on overly dorsiflexion-compliant DIPJs of the lesser digits.

    Why don't you try a Low-Dye strapping on the patient to see what happens to the digits? My guess is that may decrease the pull of the FDB and help flatten out the toes. Many women in this age group tend to have gradual flattening of the longitudinal arches probably due to post-menopausal hormonal changes which could theoretically lead to increased activity of the arch stabilizing muscles such as the FDB.

    Hope this helps.:drinks
  9. Sicknote

    Sicknote Active Member

  10. efuller

    efuller MVP

    Kevin, good point about the FDB. However, it is still possible that FDL could cause extension of the DIPJ when weight bearing. The plantar flexion moment at the MPJ and PIPJ will cause tip of the toe to be forced into the ground. Then ground reaction force will cause a dorsiflexion moment at the PIPJ. The dorsiflexion moment from the ground acting on the distal phalanx can be greater than greater than the plantar flexion moment from the tendon. I've played with some foot models and seen this effect.
  11. 56Furman

    56Furman Member

    Maybe I was not clear in my post. I just mentioned flexor stabilization is what I think is going on in my patient's foot. I don't believe I mentioned only FDL activity. I think both FDL and FDB are causing the toe contraction and lateral shift of the COF
    Your recommendation of a low Dye strapping, in addition to the CFO and Rocker sole shoe?
    You mentioned that you post-menapausal have a gradual flatten of the arch. I find this interesting, because I may notice the same thing. But I have never read any studies on this. I have often associated the arch flattening in older women to their ankle equinus from years of wearing heels. Now that they are older they are wearing flats. The arch flatten is compensatory for the equines.
  12. davsur08

    davsur08 Active Member


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