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Insole modifications for apical lesions

Discussion in 'Biomechanics, Sports and Foot orthoses' started by gaz_marshall, Mar 6, 2024.

  1. gaz_marshall

    gaz_marshall Member


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    Hello all.

    I've been trying to find papers that specifically look at offloading apical lesions via the use of orthotics but have come up blank.

    Any help appreciated.

    Many thanks

    Gareth
     
  2. efuller

    efuller MVP

    Apex of...... the toes?
     
  3. gaz_marshall

    gaz_marshall Member

    Yes indeed.
     
  4. efuller

    efuller MVP

    I don't recall any papers. I have seen discussion of removable pads in some of the old podiatry textbooks. I'm having a hard time coming up with a mechanism of how orthotic would decrease pressure on the tips of toes.

    This does bring up the question of why would people have pressure on the tips of their toes. Why do hammertoes develop and why would there still be plantar flexion moments at the various joints of the toe that would tend to elevate the pressure at the tip. A couple of theories. One is "flexor stabilization" which is the additional contraction of Flexor Digitorum Longus (FDL) to increase supination moment to augment the supination moment from the posterior tibial muscle. (The FDL has the second longest lever arm at the STJ and it is a close second to the PT tendon.) Another theory is the absence of extension moment at the PIPJ and DIPJ. The long extensor's distal attachment is the sling and wing which do not really contribute to the PIPJ and DIPJ dorsiflexion. The lumbrical muscles are the only muscles that extend the DIPJ and PIPJ. When the short and long flexors are unopposed you will get plantar flexion of the dipj and pipj. That motion/position will force the tip of the toe into the ground and could create callus or nail damage. A third theory is shoes that are too short.

    You will see people who have worn holes in the sock liner of their shoes at the tip of one or more toes. Most often the 2nd. So some people can generate a lot of pressure at the tip of their toe. In my own foot I was getting some tip of 2nd toe pain and working out my lumbricals seems to relieve the pain.
     
  5. gaz_marshall

    gaz_marshall Member

    T

    Thanks for your detailed and thoughtful reply.

    I'm considering fixed toe deformities. My main focus is the use of an aperture within an insole at the point of apical pressure. Does this actually reduce pressure? I personally suspect not but haven't had the chance to run an appropriate patient through the F Scan. Is there a better way? I maintain silicone props, if tolerated are a better choice.

    Looking around I can't see anything published on the topic specifically.
     
  6. efuller

    efuller MVP

    I agree and have not seen any literature. The reason that I think an aperture would not work is that there is usually plantar flexion range of motion at the MPJ and the toe would plantar flex into the hole until it met resistance. The commercial "props" often are not big enough to apply force under the intermediate phalanx (or some other part of the toe) to lift the tip of the toe off of the surface.
     
  7. Dan T

    Dan T Active Member

    Eric, I mainly see lesser toe retraction in a cavus foot type/those with a laterally deviated STJ axis I had always made the assumption that EDL was contracting hard to assist peroneals in eversion... thus causing toe contracture as it overpowers FDL. Do you think this a similar manifestation to the lesser toes dependant on the axis location? For example in a medially deviated axis the FHL contracts harder to supinate thus overpowering EDL and resulting in contracture.
    The toes have always struck me as the neck of a bow influenced by the tension on either side to a greater/lesser degree

    Gaz, anecdotally, I have had generalised success in reducing apical toe pressure in the higher arched group with a lateral forefoot post of 4-6 degrees. I assume for the reasons above. I would also assume this would work in reverse with a medial heel post as appropriate, to temper the work requirements of FDL in assisting supination.

    Depends, I believe, on the extent of the contracture and whether it is now arthritic etc. Liz Bayley (physio) has a great video on YouTube for intrinsic work which is always great (over the longer term) for bringing some life back into knackered contracted toes. Furthermore strengthening the weakness is a wise strategy to add in alongside the orthoses e.g. anterior compartment work in those with laterally deviated STJ/higher arches and flexed knee calf work to hit the deep posterior compartment in the medially deviated/flatter feet.
    Anterior compartment work (targeting tib ant) is also great for counteracting the pull of the 1st met by p.longus in the higher arched feet so you will also see a good reduction in pressure and callus at the 1st MPJ. Google 'tib bars', can progressively overload this like any other exercises.
     
  8. efuller

    efuller MVP

    Interesting theory on EDL causing eversion. My sense is that the EDL is not far enough lateral to have significant lever arm to cause pronation of the STJ. Especially when the axis starts lateral. In support of your idea is that I think that FDL will assist the posterior tibial muscle in medial axis feet. I'm more of the opinion that FDL and FDB cause flexion of the toes because the resultant movement weight bearing is different than non weight bearing. When the DIPJ or PIPJ plantar flexions from contraction of the flexors, upward ground reaction force, at the tip of the toe, has more leverage to dorsiflex the MPJ than the flexors have to plantar flex the MPJ.
     
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