Key Insights On Orthotic Casting And Function

Author(s): 
Guest Clinical Editor: Denise Freeman, DPM

   Dr. Freeman uses a variety of impression techniques, noting that if she wants to get a good representation of the foot, she will use plaster casting. One of the advantages of using plaster, she explains, is that plaster does not disrupt the soft tissues of the forefoot. She adds that plaster casting gives the best representation of the forefoot to rearfoot relationship. Finally, she says plaster also offers more flexibility when dealing with special situations such as taking a pronated cast.

   In regard to other casting methods, Dr. DeRose notes that foam impression techniques have improved. He recommends foam casting with the subtalar joint in neutral, the forefoot to rearfoot perpendicular and cast in the angle of gait.

   Dr. DeRose has worked with both laser scanners and digitizers at his lab. He says the biggest problem is positioning the foot well, noting there can be an awkwardness with positioning. Although digital techniques are getting to the point that they rival plaster in accuracy, Dr. Cocheba says the cost still seems prohibitive given the volume of orthoses that most practices prescribe.

Q:

What should you be looking for when a patient feels that the orthotic is not functioning correctly?

A:

When there is an issue with the orthosis shell, Dr. Freeman focuses on where on the shell is causing irritation. She frequently finds that medial arch irritation is the result of an orthosis fabricated from a negative cast that was supinated, thus creating an arch profile that is too high. Lateral heel cup irritation is mostly caused by not informing the lab that the patient had a large amount of soft tissue displacement on weightbearing, according to Dr. Freeman. She says posterior heel irritation usually results from asking for a heel cup that is too wide. Dr. Freeman cautions that the deeper the heel cup one orders, the wider the heel cup is and this can lead to shoe fit problems.

   Dr. Freeman adds that forefoot irritation, especially in the medial aspect of the forefoot, is frequently the result of too much varus posting in the orthotic. She says varus posting that is too high will not allow the first ray to plantarflex normally during the propulsive phase of gait. Dr. Freeman notes this is frequently the result of having supinated the negative cast.

   Dr. DeRose suggests first re-checking that the device fits well when the foot is in a casting position, regardless of the impression technique. After checking how the device sits in the shoe, he says one should then troubleshoot for specific problems such as heel slippage or irritation.

   If the problem is with comfort, Dr. Cocheba says the anatomic location of the discomfort usually points to inadequate matching of foot contour, which one must correct before the orthoses can effectively treat the pathology. If the issue is inadequate resolution of symptoms, he considers increasing the amount of correction in the orthoses or adding adjunctive details to optimize functional control. Dr. Cocheba adds that sometimes one must accept a scenario in which other forms of treatment — such as medical, surgical or physical therapy means — will be necessary additions to provide a satisfactory and lasting outcome.

   When troubleshooting orthosis issues, Dr. Freeman emphasizes the importance of listening closely to the patient’s complaints before recommending a plan of action. She says some complaints are related to issues of communication, such as if the patient did not follow the recommended break-in regimen, while other complaints stem from shoe accommodation issues. She stresses the point that the orthosis must work with the interface of the shoe.

   “The best functional device in the world will not function properly if placed in a floppy heeled or shallow heel countered shoe,” says Dr. Freeman.

   Dr. Cocheba is affiliated with Skagit Regional Clinics in Mt. Vernon, Wash. He is a Visiting Professor at Midwestern University and the University of Washington.

Comments

27 error points have been isolated in making orthotics. Neutral joint positioning is an art form and subject to significant error. Vertical balancing and arch fill add additional errors.

Three Dimensional Orthodynamics imaging does it through analysis of 3D mass, motion, balance, pressure, symmetry, gait, 3D geometry.

Advancements are being made to drive higher cyclic load bearing control.

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