Inside Insights On Evidence-Based Orthotic Therapy
A: Based on the literature, over the last few years, Dr. Huppin has encouraged his orthotic lab’s clientele to change their orthosis prescriptions for several pathologies. For example, for plantar fasciitis, he cites Kogler’s research showing that valgus wedging decreases plantar fascial strain while varus wedging increases strain.1 The study has prompted Dr. Huppin and his colleagues to be “much more aggressive” in advising clients to avoid forefoot varus posts, varus correction or varus wedges of any type for patients with plantar fasciitis.
Research by Kogler, et. al., demonstrated to Dr. Richie the importance of everting the forefoot on the rearfoot in treating plantar fasciitis. He also cites the importance of the casting procedure of locking and fully pronating the midtarsal joint, as well as positioning the first ray plantarflexed to optimize the effects of the functional foot orthosis on the foot’s truss mechanism.1,2
Furthermore, Dr. Huppin cites recent studies demonstrating that orthoses made from foam box casts are less effective than those made from non-weightbearing casts.3,4 Through client education, the percentage of foam box casts in his lab has decreased from about 10 percent to less than 2 percent.
Dr. Choate has been focusing on biomechanics from the perspective of physics as well as studying biomechanics textbooks and trying to improve her knowledge and application of Newton’s Laws.
“I foresee that future generations of podiatrists will make their orthotic therapy decisions based on a combination of clinical experience, research findings and principles of physics,” asserts Dr. Choate.
Q: Can you name a specific pathology you treat with orthotic therapy and note how evidence found in the literature has affected your orthotic prescriptions for that pathology?
A: Over the past year, Dr. Choate has changed her approach to treating tarsal tunnel syndrome after reading three separate articles, clinical and non-clinical, that persuaded her to consider the functional changes when a foot/ankle complex has too much stress secondary to increased pronatory forces.
In the first study, a group from Japan performed a simple clinical examination test by putting the ankle in maximal eversion/dorsiflexion while holding the metatarsal phalangeal joints in maximal dorsiflexion for 5 to 10 seconds. Researchers were able to replicate tarsal tunnel symptoms when they held the foot/ankle in a maximally dorsiflexed/ everted position (pronation).5
In the second study, Labib evaluated 286 patients with chronic heel pain over a three-year period. Fourteen patients had a triad of symptoms including plantar fasciitis, posterior tibial tendonitis and tarsal tunnel syndrome. Dr. Choate says one of the study’s conclusions was that “lack of muscular support of the longitudinal arch produced traction injury to the tibial nerve and resulted in tarsal tunnel syndrome.” This same study postulated that “failure of the static arch (plantar fascia) and dynamic arch (posterior tibialis tendon) may result in a variable degree of arch collapse leading the tarsal tunnel syndrome.”6
The third study of the biomechanics of tarsal tunnel syndrome involved a cadaver study in which researchers measured the pressure in the tarsal tunnel while holding the foot in three different positions. They concluded that there was significantly increased pressure in the tarsal tunnel when the foot was in a pronated position and decreased pressure when the foot was in a supinated position, according to Dr. Choate.7
As Dr. Choate notes, these publications each led to a similar conclusion: a pronated position leads to increased pressure in the tarsal tunnel and increased tension on the structures within the tarsal tunnel. She speculates if there may be a treatment option to fill the gap in the care of tarsal tunnel. Dr. Choate is increasing her use of functional orthotics that control subtalar joint pronation. She hopes with time, she will discover which orthotic modifications used for pronation control (such as medial skives, deep heel cups, Blake inversions or firm posting) are the best combination for improving tarsal tunnel symptoms.