Inside Insights On Evidence-Based Orthotic Therapy

      Given the increased emphasis on evidence-based medicine, our expert panelists review the impact of literature findings upon their prescription of custom foot orthoses for different pathologies.       Q: Is there evidence in the literature to support the use of functional orthotic devices?       A: The only supporting evidence relative to orthotic treatment of posterior tibial tendon dysfunction (PTTD) are studies of ankle foot orthoses (AFOs), according to Doug Richie Jr., DPM. Regarding PTTD, he says the evidence is “quite impressive” as it reveals that over 50 percent of patients can obtain satisfactory relief of pain and can avoid surgery. These studies cited by Dr. Richie primarily utilize solid AFOs with leather gauntlet restraint closures.       Regarding functional foot orthoses, Dr. Richie says reports in the literature are anecdotal when it comes to rates of success and outcomes of treatment. He notes that overall, the success and specific prescription criteria for orthotic therapy for PTTD “remain open for debate.” Orthopedic literature usually recommends using a University of California Biomechanics Laboratory (UCBL)-type device as the typical orthotic intervention before surgery, says Dr. Richie. He adds that he is not aware of any studies of patients with PTTD using a podiatric functional foot orthosis.       Many labs offer a “PTTD” device that incorporates a deep heel cup, medial and lateral flanges, and a medial heel skive of 4 mm to 6 mm, according to Dr. Richie. Additionally, he notes some labs recommend a “sweet spot” to accommodate a subluxing talonavicular joint.       “These all appear to be valid foot orthosis prescription criteria to control the severe collapsing pes valgus foot,” notes Dr. Richie.       Since PTTD is primarily a transverse plane deformity, Dr. Richie notes a foot orthosis “has little ability to control the foot in this direction.” As he has discovered, transverse plane-internal rotation of the tibia in this pathology drives the talus into severe adduction and an AFO has better leverage to control tibial rotation than a foot orthosis.       “Evidence-based medicine will be the basis for how we treat our patients in the future,” says Larry Huppin, DPM. Given that, he notes significant evidence in the medical literature on using orthotic interventions to treat various pathologies. Dr. Huppin adds that most podiatrists will find they are not currently using the best available evidence in writing orthotic prescriptions. However, he notes there are evidence-based prescription recommendations for conditions including plantar fasciitis, hallux limitus, adult-acquired flatfoot, tibial fasciitis, patellofemoral dysfunction, metatarsalgia, tarsal tunnel syndrome, lateral ankle instability, peroneal tendonitis, posterior tibial tendonitis and sesamoiditis.       Dr. Huppin says in the Department of Applied Biomechanics at the California School of Podiatric Medicine, all the instruction in orthosis prescription writing is based on what the literature indicates is the most effective orthotic prescription for the given pathology.       “Using this pathology-specific orthosis approach to orthotic prescription writing would help most podiatrists improve their clinical outcomes and I would encourage all podiatrists who use orthoses in their practice to ensure they are aware of evidence-based orthotic prescription writing,” says Dr. Huppin. He recommends attendance at the International Conference on Foot Orthotic Therapy and Biomechanics, which is held every December.       Clinical and non-clinical biomechanics studies, conducted in a variety of disciplines, continue to produce results supporting the use of orthotics for many different foot and ankle problems, according to Cherri Choate, DPM. In evaluating these studies, she says one can appreciate the significantly different approaches to orthotic usage and definition.       “I have recently recognized the importance of each of these disciplines and their resultant conclusions as each piece helps us build a more clear evidence-based foundation for orthotic therapy,” says Dr. Choate.       Q: What recent literature has influenced how you write orthotic prescriptions?       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.       For subcalcaneal pain secondary to plantar fascia overload, Dr. Richie cites literature showing that a custom device addressing supination compensation around the midtarsal joint’s longitudinal axis will most effectively relieve pain and permit a successful treatment outcome.       “I am convinced now, more than ever, that a custom functional foot orthosis, fabricated from a proper neutral suspension cast, has the best opportunity to offload strain of the medial-central band of the plantar aponeurosis,” claims Dr. Richie.       Dr. Richie cites several studies for offloading the plantar fascia. He says all the studies validate the theory that an orthosis that provides an eversion moment to the longitudinal axis of the midtarsal joint will elevate the arch and reduce plantar fascia strain.       Many DPMs feel comfortable treating metatarsalgia with functional orthoses and Dr. Huppin says there have been a significant number of articles that help define exactly how DPMs should be writing orthotic prescriptions for the common condition. As he notes, Chalmers demonstrated in 2000 that for rheumatoid arthritis patients with metatarsalgia, semi-rigid orthoses are much more effective than soft orthoses.8 In a 2006 study, Mueller and Hastings demonstrated that a total contact insert with a metatarsal pad was the most effective technique of unloading a metatarsal head.9 A 2003 study said that one should place the highest point of a metatarsal pad between 6 mm and 10 mm behind the point of maximum pressure on the metatarsal head.10       Based on the literature, for metatarsalgia, Dr. Huppin recommends a semi-rigid polypropylene orthosis with a minimum cast fill, wide orthotic plate, a cushioned topcover left unglued on the front half of the orthosis and a metatarsal pad. The podiatrist should adjust the metatarsal pad in the office so the highest point is about 8 mm behind the painful metatarsal head, suggests Dr. Huppin.       Dr. Choate is an Adjunct Assistant Professor in the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt College. She practices at For Feet’s Sake in Berkeley, Calif.       Dr. Huppin is an Adjunct Associate Professor in the Department of Applied Biomechanics at the California School of Podiatric Medicine. He is also the Medical Director for ProLab Orthotics/USA.       Dr. Richie is an Adjunct Associate Clinical Professor in the Department of Applied Biomechanics at the California School of Podiatric Medicine. He is in private practice in Seal Beach, California. He can be reached at drichiejr@aol.com.
 

References:

1. Kogler G, Veer FB, Solomonidis, SE. The influence of medial and lateral placement of orthotic wedges on loading of the plantar aponeurosis. J Bone Joint Surg; 1999;81A:1403-1413.
2. Kogler GF, Solomonidis SE, Paul JP: Biomechanics of longitudinal arch support mechanisms in foot orthoses and their effect on plantar aponeurosis strain. Clin Biomech 11:243-251, 1996.
3. McClay-Davis I, Laughton C, Williams, DS. A comparison of four methods of obtaining a negative impression of the foot. J Am Podiatr Med Assoc. 2002 May;92(5):261-8.
4. McPoil TG, Schmit D. Forefoot to Rearfoot Angle–A Comparison of Orthotic Casting Techniques. Phys Ther. 1989 Jun;69(6):448-52.
5. Kinoshita M, et al. The Dorsiflexion-Eversion Test for Diagnosis of Tarsal Tunnel Syndrome. JBJS 83:1835-39, 2001.
6. Labib J, et al. Heel Pain Triad: The Combination of Plantar Fasciitis, Posterior Tibial Tendon Dysfunction and Tarsal Tunnel Syndrome. Foot and Ankle Intl 23(3):212-219, 2002.
7. Trepman M, et al. Effect of Foot and Ankle Position on Tarsal Tunnel Compartment Pressure. Foot and Ankle Intl 20(11):221-26, 1999.
8. Chalmers AC, Busby C. Metatarsalgia and rheumatoid arthritis--a randomized, single blind, sequential trial comparing 2 types of foot orthoses and supportive shoes. J Rheumatol. 2000 Jul;27(7):1643-7.
9. Mueller MJ, Lott DJ, Hastings M. Efficacy and mechanism of orthotic devices to unload metatarsal heads in people with diabetes and a history of plantar ulcers. Phys Ther. 2006 Jun;86(6):833-42.
10. Hastings MK, Commean PK. Aligning anatomical structure from spiral X-ray computed tomography with plantar pressure data. Clin Biomech 2003 Nov;18(9):877-82.
Additional References
11. Scherer PR: Heel spur syndrome. Pathomechanics and nonsurgical treatment. J Am Pod Med Assoc 81:68-72, 1991.
12. Sarafian SK: Functional characteristics of the foot and plantar aponeurosis under tibiotalar loading. Foot Ankle 8:4-17, 1987.