Pertinent Insights On OTC Orthoses And Orthotic Modifications
- Volume 23 - Issue 12 - December 2010
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When prescribing the orthotic device, Dr. Valmassy chooses the material based on the patient’s weight, activity, shoes and foot function. He determines whether he wants to create an inversion force or an eversion force to the patient’s foot. In most instances, he notes functional foot orthoses attempt to decrease abnormal pronation with a combination of materials that have rigidity with increased rearfoot control. Typically, he will prescribe an inverted type of orthotic in the range of 5 to 15 degrees inverted, depending on the patient’s age and foot mechanics.
Dr. Valmassy also usually makes a 2- to 6-mm Kirby modification to the medial heel cup. For patients with the most severe pediatric flatfoot, he will typically prescribe an orthotic device that is inverted by 10 degrees to 15 degrees via the Root technique with an additional 6 mm of Kirby skive.
In contrast, if Dr. Valmassy wants to pronate or evert the foot to promote lateral stability, or decrease compression to the medial joint line of the knee, he typically has the laboratory introduce forefoot valgus correction into the cast. Usually, he will maximally pronate the foot in an attempt to create forefoot valgus and then prescribe a lateral Kirby skive of 2 to 6 mm with a higher lateral heel cup. In most instances, Dr. Valmassy will generally ask for a flat rearfoot post in both instances in order to create stability and gait.
However, there are specific cases such as treatment of a retrocalcaneal exostosis in which Dr. Valmassy normally uses a 4-degree rearfoot post with 4 degrees of motion. As he advises, heel cup height should always be as deep as possible, depending on the type of shoe the patient wears.
Dr. Valmassy emphasizes that an orthotic device will often exacerbate the initial symptomatology due to the contour of the medial portion of the heel cup and the amount of correction provided in an orthotic. For that reason, he advises applying a softer top cover to these devices or having a specific heel accommodation added to the device.
When it comes to limb length and equality, Dr. Valmassy will add heel lifts to the rearfoot post when possible as normally up to ¼ inch can fit into most shoes. He uses a heel lift as a separate piece during the initial phases of treatment with an orthotic device, only after he is convinced that the patient can tolerate these specific heel lifts. Dr. Valmassy advises DPMs to always be aware of the fact that asymmetrical foot function will typically lead to some degree of functional limb length inequality. He adds that often controlling each foot independently with a properly designed orthotic device will eliminate the need for any additional lift.
One might also want to consider tracing the plantar fascia with a non-permanent marker that will transfer into the negative cast, suggests Dr. Fritz. This marking transfers to the positive final mold that the technician uses to make the orthotic. He says the positive mold can be slightly built up along this marking and this will be reflected when the lab heats and presses the shell of the orthotic. Dr. Fritz notes that one can add viscoelastic polymer into the groove for extra protection.
Dr. Fritz says one can also mark prominent metatarsal heads. He notes that these marked metatarsal heads as well as any marks for pads will be most specific and transfer from the foot to the positive mold and the final product. Dr. Fritz also suggests that DPMs mark sweet spots on any prominent area or difficult Charcot deformities. Exact molding of these areas in combination with any pad or gel additions can help create a comfortable orthotic, according to Dr. Fritz.
Dr. Fritz is in private practice at Allentown Family Foot Care in Allentown, Pa. He is a Fellow of the American College of Foot and Ankle Surgeons.
Dr. Huppin is the Medical Director for ProLab Orthotics/USA and is in private practice in Seattle.
Dr. Valmassy is a Past Professor and Past Chairman of the Department of Podiatric Biomechanics at the California College of Podiatric Medicine. He is a staff podiatrist at the Center for Sports Medicine at St. Francis Memorial Hospital in San Francisco.