How To Maximize The Efficacy Of Orthotic Prescriptions

Guest Clinical Editor: Scott Spencer, DPM
“You can buy glasses at a pharmacy but are they of any benefit to you?” As he emphasizes, orthotics are not arch supports but are specifically designed devices to control the joints and architecture of the lower extremity rather than just the foot.      Q: When prescribing foot orthotic devices in general, do you lean more toward accommodation or control?      A: Dr. Kirby says all of the prescription foot orthoses he makes for his patients are functional in that he designs them to reduce the magnitude of pathological internal loading forces within the foot and lower extremity. He emphasizes these orthoses also improve the patient’s abnormal gait function and accordingly relieve symptoms and restore more normal gait function. If one requires accommodation to reduce the magnitude of pathological external loading forces acting on isolated plantar areas, Dr. Kirby says one may easily modify the functional orthoses to improve their therapeutic benefit for the patient.      If the patient has an adequate range of motion in the joints one is attempting to control, Dr. Wernick notes you can influence the joints with a functional device. He does emphasize caution when it comes to determining the direction and amplitude of motion. If a patient’s deformity cannot tolerate functional control, one should use an accommodative device, according to Dr. Wernick.      When prescribing orthotic devices, Dr. Spencer tends to emphasize motion and function control rather than accommodation. As far as control goes, he does lean toward decreased control, particularly in those who have never worn orthoses. With the vast majority of his prescribed orthoses, Dr. Spencer still uses a shell of variable rigidity. He does not use an accommodative device unless his goal is even distribution of pressure across the plantar aspect of the foot as would be the case for diabetic patients with peripheral neuropathy and a gait that is primarily apropulsive.      Q: Are there any “tricks” you have found that enhance the effectiveness of your prescription orthoses?      A: For 16 years, Dr. Kirby has used a medial heel skive to selectively increase the subtalar joint supination moment from foot orthoses for more effective treatment of those with symptoms and pathologies caused by excessive subtalar joint pronation moments. He also commonly uses a lateral heel skive to treat symptoms such as peroneal tendonitis and chronic lateral ankle instability, as well as lateral midfoot and forefoot symptoms caused by excessive subtalar joint supination moments. Dr. Kirby notes that adding 3 to 6 mm heel lifts to orthoses frequently abates plantar arch irritation from orthoses and permits resupination of the foot to occur earlier during gait.      Dr. Kirby also says having the anterior edge of the orthosis 5 to 6 mm thick, as opposed to skived thin, frequently leads to great improvements with metatarsalgia and other metatarsal head symptoms. Not only do plantar fascial accommodations make orthoses more comfortable but Dr. Kirby emphasizes the accommodations’ importance in improving the orthoses’ therapeutic effectiveness for various pathologies.      Dr. Wernick cites the “trick” of viewing the position of the hallux in relation to the first metatarsal shaft. He says the normal resting position should be 15 degrees of dorsiflexion of the hallux. If the angle is diminished or the toe is directly aligned with the metatarsal, this indicates that the first metatarsal is dorsally dislocated, according to Dr. Wernick.      When casting the orthotic devices, Dr. Wernick advises one to dorsiflex the hallux to approximately 15 degrees. He says one can do this by dorsiflexing the toe while plantarflexing the metatarsal.      Dr. Spencer is interested in some of the different ways one can assess patient function and prescribe a foot orthotic device. He is “especially intrigued” by using the F-Scan to assess and prescribe foot orthotics by looking at the distribution of pressure and progression of the center of mass. By modifying an orthotic shell to create a more symmetrical presentation of those two factors, one can alleviate pathology. As Dr. Spencer says, the F-Scan method eliminates “much of what we do now in orthotic assessment but it is more time consuming.” Dr. Kirby is an Adjunct Associate Professor in the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt College.

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