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Is it important to position foot in subtalar joint neutral position during non-weight-bearing molding for foot orthoses?
Lee WC, Lee CK, Leung AK, Hutchins SW. J Rehabil Res Dev. 2012 May;49(3):459-66.
Quote:
When taking molds for foot orthoses, it is accepted practice to position the subtalar joint in its neutral position. However, foot orthoses have no contact with the talus, and this leads to a hypothesis that as long as there is correction available to appropriately align the forefoot relative to the hindfoot when taking a mold, changes in subtalar joint angles do not lead to significant alterations in the plantar surface shapes of the molds taken. This study tested this presumption with 20 subjects between 22 and 46 years old. During non-weight-bearing casting, the subtalar joints were aligned at positions of 4° of eversion, 2° of eversion, 2° of inversion, and in neutral. At each orientation, forces were applied over the forefoot such that the metatarsal heads were aligned with the rearfoot. Digital scanning was used to analyze the shape of each negative mold. There were significant changes in projection volume in different subtalar joint orientations. However, the changes in arch heights, navicular height, and protrusion were insignificant and very small. It is therefore suggested that as long as the forefoot and hindfoot are appropriately aligned, variations in the orientation of the subtalar joint would be acceptable.
Re: Is it important to position foot in subtalar joint neutral position during non-weight-bearing molding for foot orthoses?
I used to make birky cork orthotics for skiing under the Superfeet brand during the 80's and 90's which was an unweighted vacuum casting technique using hot cork, a plastic bag over the foot and a vacuum to pull the air out of the bag against the foot, resulting in atmospheric pressure molding the cork against the sole of the foot. The cork blank sat on a plastic former during the process. The idea was to get the foot into sub-talar neutral during the forming time because if you did not do this the resulting shape could be twisted in the transverse and frontal planes making the result less tolerable and less stable inside a boot. This was before I was trained as a pod so we did not always understand the full implications of what we were doing but we certainly had to deal with recurring problems if they happenned. We did sometimes alter the result(medial or lateral wedging) to give what we thought was better skiing function.....not gait function
regards Phill Carter
Re: Is it important to position foot in subtalar joint neutral position during non-weight-bearing molding for foot orthoses?
Quote:
Originally Posted by pgcarter
I used to make birky cork orthotics for skiing under the Superfeet brand during the 80's and 90's which was an unweighted vacuum casting technique using hot cork, a plastic bag over the foot and a vacuum to pull the air out of the bag against the foot, resulting in atmospheric pressure molding the cork against the sole of the foot. The cork blank sat on a plastic former during the process.
For those that may be interested in the history of these techniques, the individual that invented that casting method and the Superfeet brand of insoles and alpine ski insole system was one of my (and Eric Fuller's) biomechanics professors at CCPM, Dr. Christopher Smith. We learned the plastic-bag-over-the-foot-casting-technique in 1981 from Dr. Smith.
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Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Is it important to position foot in subtalar joint neutral position during non-weight-bearing molding for foot orthoses?
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