Foot Orthotics - Basic Types of Foot Orthoses - Essay Example

Foot Orthotics [The of the appears here] [The of appears here] Introduction By definition, an orthosis is a device that is used to protect, support, or improve function of parts of the body that move. In the field of podiatric orthopedics, the terms orthoses and orthotics are used to describe a wide range of devices that are placed inside the shoe. "Foot Orthotics re-aligns the foot and ankle bones to their neutral position, thereby restoring natural foot function. In turn this helps alleviate problems in other parts of the body" (http://www.foot-orthotics.co.uk). Other terms used for orthoses include inserts, insoles, inlays, supports, and cushions. The three basic types of foot orthoses are pre-fabricated, customized, and custom-molded. A pre-fabricated orthosis is one that is mass-produced and is intended to be dispensed to the user without modification. Pre-fabricated orthoses are usually designed to provide either increased support or shock absorption for a specific area of the foot, such as an arch support or heel cushion. They may also provide cushioning to the entire foot, as is the case with the use of a full insole. A customized orthosis usually consists of a pre-fabricated base component that is modified in some way, such as adding a metatarsal pad or heel lift. A custom-molded orthosis is one made from a model of the patient's foot made from some form of three-dimensional impression-taking procedure. These devices are used for patients with more severe or complicated foot problems. They are commonly composed of a shell, the layer of material next to the foot and in total contact with the foot, and posting material, filling the space between the shell and the shoe. Custom orthoses can be further modified by adding materials to the top of the shell to either redistribute pressure or provide cushioning. Foot orthoses are often described as being either accommodative or functional. An accommodative orthosis is designed primarily to accommodate a rigid foot or foot deformity, or one that is a risk, while a functional orthosis is designed to realign a more flexible foot by providing joint stability and support. In reality, most orthoses offer some degree of both accommodative and functional properties. In general, foot orthoses are designed to accomplish one or more of the following: 1) Reduce shock, 2) Reduce shear, 3) Relieve areas of excessive plantar pressure, 4) Stabilize and support the joints of the foot, 5) Limit motion of joints. (Caselli, 2004). Orthoses or orthotic devices are medically-prescribed shoe inserts that are designed to improve foot function and reduce mechanical stress. The American Podiatric Medical Association categorizes them as follows: those that intend to change foot function, those that are protective in nature and those that combine functional control and protection. Some of the materials used in these devices offer excellent shock absorption and compression set resistance, while others are noted for support and moldability. Whatever the offering, these materials are often used in combination for a better functioning orthosis. Depending on the condition of the foot, they can be constructed of one or more layers with two- or three-layer constructions most often selected by medical practitioners. These materials are offered in a wide range of formulations, densities, thicknesses, colors and weights. Some are measured in durometer, a guide to determine a material's softness in relation to other materials. Distributors buy these specialty materials from manufacturers like Rogers Corp, Rogers, CT, and, in turn, sell them to fabricators which include podiatric laboratories, podiatrists, orthotists, pedorthists and physical therapists, among others Certain biomechanical foot deformities such as ligamentous laxity, neurologic deficits or supinated foot types which function with an inverted heel, make some people more susceptible to inversion sprains. Valmassy (1996) also states that those with an uncompensated rearfoot varus, partially compensated rearfoot varus, flexible forefoot valgus or a rigid forefoot valgus can also cause lateral ankle instability. (Valmassy, R.L., 1996, p75) It is important that you wear your foot orthoses for short periods only when you first receive them. The following wear pattern is suggested: DAY ONE - 1/2 hour DAY TWO - 1 hour DAY THREE - 2 hours And then increase by ONE HOUR each day until you are comfortable wearing the foot orthoses all day. During this period you may experience the following: Heel slipping from the shoe, Pressure in the arch of the foot, Feeling of being tilted forwards and/or Aches and discomfort in the calf / lower back / hips / hamstrings. http://www.rmpd.org.uk/abstracts/bioengineering/fixed_ankle_foot_orthoses.htm Soft, semi-rigid and rigid orthotics In soft orthotic applications, fabricators possibly will ask for high-performance elastomer materials for instance Rogers' PORON Medical-brand cellular urethanes to absorb shock, aid balance, as well as provide comfort to the wearer. Utilized as soft tissue supplements for custom-molded plus multi-density orthoses, these open-cell materials breathe and work as soft cushions. A cushioning material must be capable to bounce back or spring back to its original thickness after repetitive stresses like standing, walking, jumping or running. If foam bottoms out or compresses rapidly, it will drop its control to absorb stress, ensuing in a large amount inferior oftentimes dead product. Non-moldable material, sheet urethane foams are usually backed by moldable materials for example EVA or polyethylene foam. These materials are used for acquiring the shape of the foot. Not like their cushiony cousin, these materials are likely to compress rapidly, although mold very effortlessly to the wearer's foot. Plastazote, a trademarked name as well as the polyethylene foam of choice for many, is capable to modify to a patient's foot within a day. EVA, as well moldable, would be to a great extent denser material, offering greater support. As an instance, in building an insert requiring the advantages of all three materials, a three-layer construction can be put mutually with polyethylene foam on top, the soft urethane foam in the middle and EVA on the bottom. The patient at this instant has an orthotic that is supportive, molds to the foot rapidly and stays spongy for the life of the product. With every step, the ball and heel are without a doubt the most weight-bearing parts of the foot. A comfy interface between the ground and the wearer is founded by the choice of material. The perfect cushioning material distributes body weight forces more equally all through the sole of the foot, in that way dropping pressure. Innovative combinations like PORON Dual Layer urethane foam assures even pressure distribution and augmented constancy. The top layer conforms to the foot for modified comfort although a bottom layer absorbs shocks for cushioning support. A patent-pending technology is used to accumulate the two pieces with no adhesives. Cork and less rigid types of thermoplastic materials as well as EVA/SBR, can be used in semi-rigid orthotics. A number of types of cork are heat-moldable, though others are not. Heat-moldable cork is heated in the oven by means of the similar process is any plastic or acrylic composite material, that is it is formed over the positive cast of the patient's foot. After that, it is ground and trimmed to build an orthotic. This material is less rigid than acrylic. Usually, soft urethane foam is sited on top with some polyethylene foam below it, and after that covered. In designing rigid orthotics, materials for instance acrylic composites or thicker thermoplastics are employed. These devices are premeditated to manage motion in two most important foot joints. They are made-up from either a plaster of Paris mold otherwise a foam impression of the foot. In these applications, at times soft urethane foam is included to present desirable cushion. Orthotics also allows the patient to bath normally, wear normal shoe gear, avoid the protracted use of expensive anti-inflammatory agents and their gastrointestinal side effects, and avoid expensive surgical treatments such as plantar-fasciiotomy or extra corporeal shock wave therapy. There are various types of foot orthotics available to the podiatrist. They include out-of-the-box devices which allow for minimal if any customization, those which can be custom-heated or injection-molded and customized to the foot, and finally the most common type, the many fully-custom orthotics made from a positive model of the foot. The decision to fabricate a particular type of device should be based solely on clinical criteria, but is often driven by either patient economics or the insurance carrier. Prosthetists and orthotists provide treatment to people with neuromuscular and musculoskeletal disorders through the provision of prostheses (artificial limbs) or orthoses (orthopaedic appliances, braces). Prosthetists and Orthotists Prosthetists and orthotists are trained in the patient assessment, prescription and manufacture related to the provision of prostheses and orthoses. Training involves theoretical and practical work and clinical placement within prosthetic and orthotic facilities. Studies are taken in anatomy, physiology, biomechanics, materials technology, pathology, neurology, prosthetics and orthotics. An honours year and higher degrees are also available. Prosthetists and orthotists are not required to be registered. Prosthetists and orthotists work within the public hospital system, in private practice and to a more limited extent in research and education. They are a relatively new addition to the multidisciplinary team, yet prostheses and orthoses have been integral to patient management, particularly of amputees, for many years. Prosthetists and orthotists expect health professionals who refer patients for treatment to provide sufficient information regarding diagnosis and suggested functional outcome to enable relevant prostheses and orthoses to be provided. Prosthetists and orthotists have a professional responsibility to make their own assessment, ensure the prosthetic or orthotics design is appropriate for the individual patient, provide prostheses and orthoses which are structurally sound and educate the patient about appropriate use of the device. Ethical codes in the hospitals presume that all professional people are moral, honest and trustworthy at all times, a presumption which is clearly false. Doctors who breach ethical principles are open to action on several levels according to the seriousness of the breach. Disciplinary action may be taken by colleagues, employers or professional associations but generally does not carry legal or statutory sanctions. Medical boards' sanctions range from reprimand to deregistration; the allegations faced by the doctor will be specific instances of unprofessional conduct rather than breaches of ethical codes. Some breaches may also lead to criminal charges being heard in the courts, while other allegations may result in action in the civil court. Speaking generally, the criminal law fixes the negative limits and prescribes what must not be done, while the civil law, through torts of battery and negligence, fixes the positive limits that are what the doctor ought to do as a minimum. In like manner, medical boards and tribunals protect the community by setting limits beneath which professional standards should not fall. It is the medical profession itself which, by its undergraduate, postgraduate and continuing education and quality assurance programs, sets the standard of professional excellence. Medical ethical codes provide guidelines to help deal with the moral dimensions of medical practice. These codes do not in any way override the personally held ethical and religious beliefs of doctors on difficult moral issues such as abortion, sterilization and euthanasia. Functional Orthotics The functional orthotics is necessary prostheses designed to control or eliminate many patho-mechanical problems arising from foot or leg deformities. They may also be used to control muscular aberrations or congenital factors. These devices are fabricated from plaster of Paris casts of the feet. They are made of thermoplastic acrylic glass, and monomer or polymer acrylic posting materials, using the neutral position of the feet. The functional orthotics does this by altering the vectors of biomechanical stresses in the feet, legs and ankles and by correcting the angular relationship of the osseous structures of the feet. This will change the direction, degree, and duration of such stresses during gait cycle, and allow for a more normal gait. By establishing a normal gait cycle, the stress on the plantar fascia will be reduced. These orthotics services as stated should in no way be construed as cosmetic in any manner, and are necessary to maintain the functional results achieved with the current treatment of foot strapping and night braces. When prescribing a functional foot orthotic for hallux limitus, one must consider the weight of the patient, the position of the first metatarsal, the foot type, and the types of shoes he/she wears. When a patient presents with a pes planus foot type and first MTP joint pain, a physician should consider using a semi-rigid polypropylene device, with standard arch fill and a 0/0 degree rear-foot post. In a patient with advanced-stage hallux limitus, one should consider a Morton's extension with 1/4" Korex. The purpose of this is to support and prevent motion at the first MTP joint. These patients have such severe DJD that any motion of the joint will aggravate their symptoms. In these patients it is vital that you explain to them that their arthritis may get worse even with the orthotics, but the modification may help delay or prevent the need for a fusion or joint replacement in the future. Other common post-operative complications that occur after a first metatarsal osteotomy is sub second metatarsalgia, and possibly an elevated hallux. This is due to excessive shortening of the first metatarsal. This often occurs after a metatarsal head osteotomy and particularly a Lapidus arthrodesis. Custom-made orthotics is the primary method of treatment. A patient presenting with a pes planus or a pes cavus foot type and a short first metatarsal would benefit from a semi-rigid device with a Morton's extension applied to the top cover. The Morton's extension is applied underneath the first metatarsal head and distally to the end of the top covers. The Morton's extension prevents excessive motion at the first MTP joint and shifts pressure off the second metatarsal head. It also brings the "ground" up to the hallux, making it more comfortable for the patient with a lack of purchase of the great toe. First Metatarsal Primus Elevatus The surgical management of severe bunion deformities sometimes results in first metatarsal elevatus relative to the 2nd metatarsal. This is common after a closing base wedge osteotomy. Even after 6-8 weeks, when the bone appears healed on x-ray, it is common that the bone seems to elevate when returning the patient to weight bearing. In addition, a Lapidus arthrodesis sometimes results in elevation of the first metatarsal head. This may be due to poor positioning at the fusion site. It is interesting that not all patients with first metatarsal elevatus have restricted dorsiflexion of the great toe, but most patients do. One reason for this may be that the hypermobile patient is still able to compensate for this elevatus and maintain adequate dorsiflexion. Orthotic management is similar to treating a short first metatarsal and is the mainstay for conservative management of this complication. Second Metatarsal Stress Syndrome Following a first ray procedure, the second metatarsal head and joint are often inflamed or irritated. The second metatarsal stress syndrome can be due to capsulitis of the 2nd MTP joint, flexor tendonitis or synovitis of the joint. Treatment will often begin with NSAID's, corticosteroid injections with dexamethasone, and physical therapy. Custom orthotics play an integral role in the management of this complication, but it is necessary to reduce the inflammation of the joint initially in order to improve the outcome of an orthotic. When prescribing an orthotic for second MTP stress syndrome, one should utilize an extension at the inferior surface of the top cover to accommodate and off-weight bear the second ray. A "slot" accommodation in a shape of a "U" directly underneath the involved metatarsal head is often recommended. The pes planus foot type will benefit from a semi-rigid device, with minimal cast arch fill, a 4 mm intrinsic medial cast skive, 4/4 rearfoot post, and a top cover with a slot accommodation beneath the second metatarsal head. The forefoot accommodation is usually made from a durable material, such as Korex, Nickleplast, or EVA. (Mooney, M., Maffey-Ward, L, 1994, 220-226) Lesser Metatarsalgia One of the most frustrating post-op complications in forefoot surgery occurs after performing a lesser metatarsal osteotomy. This is often performed to treat a plantarflexed or prominent metatarsal head. Post-operatively the symptoms may be transferred to an adjacent metatarsal or there may be capsulitis or scar tissue at the surgical site. This can be minimized by simply shortening the metatarsal, rather than dorsiflexing it. Because of the shape of the metatarsal, the head of the bone will elevate as it is shortened. Management often begins with physical therapy, including phonophoresis with hydrocortisone cream, manual range of motion exercises and massage. Sometimes a corticosteroid injection is necessary to help break up adhesions and reduce inflammation. Orthotic management usually includes a "slot accommodation" for metatarsals 2, 3 or 4. In patients with post-op fifth metatarsalgia, one should use a forefoot modification with Korex or EVA under metatarsals 1 through 4 only, to off-weight bear the 5th metatarsal. Rearfoot Complications Posterior Tibial Tendon Dysfunction One common type of rearfoot complication after foot surgery is posterior tibial tendon dysfunction. This may occur after a tenosynovectomy of the tibialis posterior, after a subtalar fusion if the heel is in valgus, after a midtarsal arthrodesis if the foot is too abducted, and in a flexible flatfoot after any type of surgery due to abnormal gait. In a patient with flatfoot surgery, whether an osseous or soft tissue repair was performed, the recovery for the patient is long. Functional ankle-foot orthoses (AFO's) may be used post-operatively to assist the patient in transitioning from cast immobilization to shoes. It is recommended that when the patient is ready for weight bearing, a stable shoe with the added stability of an AFO be used to enhance recovery and assist with a proper healing position of the foot. The AFO should have a deep heel cup (18-20mm) and a wide-width orthotic plate. The hinge of the AFO should be a flexible (dynamic) pivot hinge which allows for adequate ranges of motion as long as the ankle joint is not arthritic. Although the medial arch was reconstructed surgically, it is recommended to incorporate a 2-to-4 mm skive along with 2-to-4 degrees of rearfoot inversion in the cast work of the functional AFO. The amount of medial skives and the combination of rearfoot inversion depends on the severity of rearfoot eversion prior to the surgical correction. Therefore, following the post-operative regimen of a non-weight bearing cast, followed by a weight bearing cast, a functional AFO will allow for an easier transition into a stable shoe. The combination of a stable shoe and an AFO increases mechanical control of the foot as well as aids in post-operative recovery and assisting in the return to proper range of motion of the foot and ankle. Once the patient has returned to full activities, one may consider a custom orthotic to help prevent recurrence of the posterior tibial (PT) tenosynovitis. The recommended device for PT dysfunction is a polypropylene device with 4-10 degrees of inversion depending upon the severity of the calcaneal valgus and a 4mm medial skive. This typically works well for mild to moderate dysfunction and tenosynovitis, but in a more advanced stage where degenerative joint disease is present a dynamic-hinge custom orthosis is more effective for long term use. This device should be inverted with a medial skive but will also have a 20 mm heel cup and ankle stirrups to better control the motion at the ankle and rearfoot. In addition, a spring or flexible-hinge will allow for flexibility at the ankle. Sinus Tarsi Syndrome This complication can occur after any type of foot or ankle surgery. It is often the result of walking with an abnormal gait. This is common after being immobilized in a cast for more than a month or if the patient is afraid to walk in a normal heel to toe gait immediately after forefoot surgery. Initial treatment often includes NSAID's, OTC orthotics and corticosteroid injections. If symptoms are persistent, then a custom orthotic plays a vital role in alleviating pain. Two different foot types present with sinus tarsi pain: 1) A pes planovalgus foot type, which pronates at the subtalar joint and unlocks the midtarsal joint. This repeated stress on the lateral aspect of the rearfoot jams the nerve and ligament in the sinus tarsi canal. For the patient who has a flexible flat foot deformity, consider a polypropylene device which is semi-rigid. It should have a deep heel cup, and the orthotic width should be wide-to increase the surface area under this hypermobile foot. The cast fill should be minimal to allow a tight control over the medial arch. Most of these patients have an abnormally medially deviated subtalar joint axis and it is recommended to incorporate 2-4 mm of a medial skive to help compensate for this. 2) A pes cavus foot type is supinated through most of the gait cycle, therefore repeatedly stressing the lateral aspect of the rearfoot and stretching the nerve and ligament in the sinus tarsi canal. The rigid pes cavus foot type is also prone to lateral ankle instability, which contributes to the sinus tarsi irritation as well. For the patient who has a rigid cavus foot deformity, consider a polypropylene device which is flexible. It should have a deep heel cup, and the orthotic width should be normal. The cast fill should be normal to prevent irritation of the plantar fascia. The rearfoot post should be extended laterally only by 1/2 cm. If the shoe style does not allow a big rearfoot post, consider instructing the lab not to bevel the lateral aspect of the rearfoot post. Both modifications of the rearfoot post will shift stress off the lateral column of the foot. Cuboid syndrome is a challenging complication after foot surgery. This may occur due to inverting the foot excessively when applying an Esmarch bandage, walking with an abnormal gait after forefoot surgery, or after a plantar fascial release. Conservative management should be done in a step-wise approach. Typically, if an injection is necessary, then the patient requires immobilization in a Cam walker or below knee cast for 3-6 weeks. (Mooney, M., Maffey-Ward, L, 1994) Subtalar Joint Arthritis Subtalar joint arthritis is also common after a repair of an intra-articular calcaneal fracture, after an isolated ankle fusion, after a talo-navicular fusion or a calcaneo-cuboid fusion. Initial treatment may include corticosteroid injections and NSAID's but orthotics and braces may be very helpful. Patients with pain in the subtalar joint often respond well with a softer orthotic made of black Plastazote, EVA or Cork, with a deep heel cup 18-20mm and a zero degree rearfoot post. An alternative would be a thin polypropylene device with an EVA arch fill. If the pain is more severe, then a dynamic hinged custom orthosis may alleviate pain. This should include a deep heel cup, and a zero degree or flat rearfoot post. Conclusion As we face the challenges of post-operative complications we must always try to learn from our mistakes and the mistakes of others. You need to learn from other people's mistakes because you don't have enough time in your own career to make them all yourself. Always take the time to evaluate and discuss complications with your peers and learn from each case. This will help us to learn new and better techniques for foot and ankle surgery and continue to achieve better surgical outcomes in the future. There have been many advances in the fabrication of custom orthotics and ankle foot orthoses over the past decade. All devices are not created the same. There are tremendous advances in the modifications to orthotics, including the medial skive technique and the inverted orthotic. In addition, there have been significant improvements in the precision of the devices and the materials utilized (Kirby, K.A, 1994) . Previously the use of an AFO after foot or ankle surgery was limited due to comfort, restriction of motion of the rearfoot and ankle, and the inability to support the arch well. In recent years, the fixed-hinge custom orthotic has been introduced into the armamentarium of the podiatric surgeon. Its ability to control the foot and ankle is unprecedented. Spring or dynamic hinge can continue maintaining ankle motion yet control rotation of the tibia and abnormal pressures in the foot. These devices play a vital role in the management of surgical complications. With the passage of time and with more and more developments plus the new advances made in the fabrication of these devices the outcomes of patients will improve. Reference: http://www.rmpd.org.uk/abstracts/bioengineering/fixed_ankle_foot_orthoses.htm http://www.foot-orthotics.co.uk Caselli, Mark A., 2004. Orthoses, materials, and foot function: different uses require the unique properties inherent in the various types of devices available. Podiatry Management. Kirby, K.A, 1994. The Medial Heel Skive Technique, Precision Labs Newsletter, July-August, 1992. Mooney, M., Maffey-Ward, L, 1994. Cuboid Plantar and Dorsal Subluxations: Assessment and Treatment, JOSPT 20:220-226 Valmassy, R.L., 1996. Clinical Biomechanics of the Lower Extremities, St. Louis, Mosby, p.70, 75. Read More