A foot orthosis is a device that is
applied to the foot. The possible functions may be follows, evenly distribute
weight bearing forces over plantar surface, relieved pain from painful
sensitive areas, support arches of foot, decrease amount or rate of
hyperpronation in walking or running, accommodate congenital foot deformity,
compensate for leg length discrepancy, decrease some weight bearing stresses at
specific joints. Pathologies that we will make a foot orthosis for patient such
as pes planus, pes cavus, metatarsalgia, painful heel.
A
second option is the foam impression method to get an impression of the foot in
a partial weight bearing position. A semi-weight bearing may often better
capture the location of a bony prominence, callus, or fibrous tissue mass. So
the foam impression technique tends to have more soft tissue deformation on the
plantar surface, which simulates the soft tissue changes taking place in weight
bearing and this reduces the amount of modification needed to account for this.
The one disadvantage of this method is that more proximal contours (e.g.
calcaneus) are not captured as well.
The orthotic intervention needs a clear
understanding of pathology, daily activities and materials and techniques for
making.
Insole is one orthotic solution for the
foot, this design is simple to manufacture and fit, can be made to fill the
entire length of the shoe or be ¾ in length. Usually for provide support of
longitudinal and transverse arches. Rigid, semi-rigid, flexible materials can
be used. It is indicated for mild arch instability, mild sub-talar instability,
and insensate foot. But it is contraindications for moderate or severe arch
instability and moderate or severe sub-talar instability.
Casting is one of the processes to make
insole. The purpose of the casting
procedure is to obtain the accurate alignment and shape of the patient’s feet
that for capture the foot in most functional position, subtalar neutral is the
main objective, secondly is forefoot neutral.
There are a variety of methods for taking an impression of the foot to
send to a laboratory for fabrication of orthosis. The most popular, and
probably the most accurate, method remains the plaster cast. The application of
the plaster bandage to the foot can be done in variety of ways, such as
circumferential wrap or slab casting. Plaster casting is the optimum method of capturing the foot in subtalar joint neutral. it have most ability to capture the needed areas more proximally, such as for heel-foot type
of devices. Plaster bandage techniques can do either non-weight bearing with
the patient lying in supine or prone position and partial weight bearing with
patient sitting. But patient may need to use plastic wrap to cover their skin
and orthotist may need to use glove to prevent dirty from plaster using.
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| negative cast from plaster casting |
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| negative cast from foam impression casting |
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| positive cast |
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