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Orthotics and Pes Cavus... Indications?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Guy Del Prince DPM, Mar 3, 2011.

  1. Guy Del Prince DPM

    Guy Del Prince DPM Welcome New Poster


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    What biomechanical control are we trying to accomplish when orthotics are prescribed for the pes cavus foot with heel spur syndrome? The calcaneus is already inverted, and many beyond the comfortable range for normal "shock reducing" pronation.

    We are so used to using functional orthotics to address the overly pronated foot... what type of orthotic (if any) should be prescribed for pes cavus plantar fasciitis? What are the biomechanics behind your choice?

    Thank you

    Guy Del Prince, DPM
     
  2. efuller

    efuller MVP

    Pronation doesn't hurt. Tension in the plantar fascia hurts. You can reduce tension in the fascia while keeping the STJ pronated. Load on the first metatarsal will increase tension on the medial slip of the plantar fascia. You can reduce load on the medial slip by increasing load on the lateral forefoot. Load = body weight. If you reduce load in one location you have to increase it in another. A forefoot valgus wedge/ intrinsic post can reduce tension in the plantar fascia.

    This is the difference between biomechanics based on positoin and motion (kinematics) as opposed to biomechanical treatment based on forces and moments (kinetics). There are many threads here on the arena discussing tissue stress biomechanics. Pain is often related to the stress on anatomical tissues.

    Eric
     
  3. Lab Guy

    Lab Guy Well-Known Member

    I agree with Eric. I have a fairly rigid forefoot cavus feet and tight medial band. I wear functional orthotics prescribed with 5 degrees of intrinsic ff posting, lateral column flattening, fascia groove, and 4 degrees of valgus posting with no motion at all. The device is flexible enough to provide shock absorption during midstance of gait.

    I also have a pair of eva custom inserts with a 3 mm build up along the lateral column that is very effective, especially when I have to stand all day when exhibiting at trade shows.

    With cavus feet were dealing with a laterally deviated stj axis and were trying to increase the pronation movement from the orthotic and decrease the supination movement from the Posterior tibial tendons.

    steven
     
  4. davidh

    davidh Podiatry Arena Veteran

    Good question GDP, nicely explained by Eric.

    Two conditions I commonly see which are associated with a rigid cavus foot are chronic inversion sprains of the ankle, and PF.

    A custom orthotic which incorporates a small heel-raise and neutral heel, and an extrinsic forefoot valgus post of perhaps 2 degrees will offer cboth ontrol and comfort, often to the point where no other treatment is necesary.
     
  5. efuller

    efuller MVP

    I might agree that most commonly the cavus feet have laterally positioned STJ axes, but there are exceptions. So, you do still have to look at STJ axis position and remember the Coleman block test.

    Eric
     
  6. Guy:

    It is my belief that much of the plantar heel pain we see and label as "plantar fasciitis" in the pes cavus deformity is not primarily due to excessive tensile forces within the plantar fascia but, rather, is due to excessive magnitudes of compression and impact forces acting on the plantar calcaneus. We can see evidence of this "bone bruising" from excessive plantar calcaneal compression forces in MRI which may show subcortical marrow edema in the plantar calcaneus. It just so happens, also, that the fibers of the plantar fascia originate from this area of the plantar calcaneus, so we call it "plantar fasciitis" regardless of the true etiology. Foot orthoses that are designed to reduce the magnitude of compression and impact forces on the plantar calcaneus generally work quite well at relieving plantar heel pain in the pes cavus deformity.
     
  7. DrTheodoulou

    DrTheodoulou Welcome New Poster

    I believe assessing for hind foot flexibility in the cavus foot is essential in determining whether functional control is indicated. The Coleman block test is critical. If the hindfoot varus is fixed then a neutral device geared toward shock absorbancy is indicated. One can incorporate a first ray cut out. If the varus is reducible, then a forefoot valgus post would be beneficial to reduce need for hindfoot compensation. Do not forget the role of the triceps surae and its potential influence with reduced ankle jont dorsiflexion and loading of the fascia. Many require aggressive stretching of the posterior muscle group or slight heel lift in device. Finally, many of these presentations do represent underlying neuromuscular component and many not be a static condition and warrants observation and modification of treatment accordingly.
     
  8. PodAus

    PodAus Active Member

    Sagittal plane facilitation in tandem with impact / compressive attenuation;
    spreading the load and making movement easier is the focus on the orthotic design parameters;
    shell flexibility - weight of pt? Activity type?
    Windlass mechanism - Jack's test? FF valgus padding / 1st ray co / cluffy wedge?
    Heel Lift (B) - lunge test easier? / consider weight & density?

    :morning:
     
  9. TDC

    TDC Member

    My thinking on this is that pes cavus pt’s with plantar fasciitis generally need sagittal plane control from their orthoses and as such, minimal arch fill on the positive cast should provide the pt with good MLA and LLA contact, reducing forefoot dorsiflexion moment, calcaneal plantarflexion moment and ground reaction force (GRF) on the medial calcaneal tubercle due to redistribution of plantar pressures into the midfoot. A plantar fascial groove would likely be necessary and a temporary heel raise can provide some relief in conjunction with a triceps surae stretching program.
    Does anyone routinely palpate the plantar fascia on pt’s with pes cavus feet in relaxed stance position?
    This may be one way to determine if the plantar heel pain is due to tensile or compressive forces. I have seen extremely prominent and on palpation, rock solid plantar fascia’s in such pt’s. Therefore, I would assume the pathological force creating symptoms is tensile.
     
  10. DrTheodoulou

    DrTheodoulou Welcome New Poster

    For those of us who do surgical reconstruction of the cavus foot, a common ancillary procedure is release of the plantar fascia or Steindler stripping. I typically simply release the fascia and do not strip the structure. This allows for the lowering of the medial arch and elongation of the foot following our various forefoot, midfoot or calcaneal osteotomies. This would suggest that a contracted fascia is a significant issue in this condition. Any attempts of elongation of the foot during stance, particularly midstance would be met with soft tissue resistance by this extremely dense structure. Repetitive stress loading follows and the fascia strain occurs. Biomechanically, if we can reduce the lowering of the instep (elongation of the foot), accommodate for the prominent contracted fascia, this should address the clinical symptoms.
     
  11. Lab Guy

    Lab Guy Well-Known Member

    For those of us who do surgical reconstruction of the cavus foot, a common ancillary procedure is release of the plantar fascia or Steindler stripping. I typically simply release the fascia and do not strip the structure. This allows for the lowering of the medial arch and elongation of the foot following our various forefoot, midfoot or calcaneal osteotomies.

    Good posts Dr. T. I had many patients that had a flexible cavus feet whereby the inverted heel would come back to neutral when the forefoot was completely unloaded. In these cases I had considerable success with a DWO of the base of the first met, Dwyer osteotomy and release of the plantar fascia with care taken to preserve the lateral band for lateral column stability. Long term, the patients were very happy and the procedures were done when orthotics by themselves could not get the job done.

    I also think when orthotics for cavus feet should have a lateral Kirby skive or posted with a 3-4 degree valgus RF Post to transfer the CoP medially in addition to good support for MLA and FF Valgus posting.

    Steven
     
  12. DrTheodoulou

    DrTheodoulou Welcome New Poster

    Steven -

    I agree 100% with your approach and recommendations. This has also been my experience.

    Dr. T
     
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