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Accommodative Orthotics

These encompass a wide range of devices, from semi-rigid devices with modest control and cushioning, to soft devices which distribute weight evenly via the principle of total contact. The latter, widely used for diabetic and rheumatoid feet, utilize materials that conform to the foot, such as closed cell foams. The advantage is that more weight is borne by the arch, and less weight is borne by the metatarsal heads and other normal weight bearing areas. The disadvantage is that these devices lack the durability of other orthotics, and frequently bottom out. A diminished fat pad in a geriatric patient is managed in a similar way, distributing weight to normally non-weight bearing areas.

Semi-rigid devices can be used to relieve the pressure of a plantarflexed metatarsal by a cutout under the metatarsal head, or to redistribute weight away from any bony prominence. They can utilize a toe crest to support and relieve pressure from hammertoes, mallet toes and claw toes. They can also be used to redistribute weight away from the central portion of the heel in plantar fasciitis. In addition, Semi-rigid devices provide a combination of cushioning and mild functional support for arthritic feet in geriatric patients.

Materials for Fillers and Accommodative Devices

Open Cell Foams: Offer good evaporation and heat dissipation characteristics.

Polyurethane Foam: Includes PPT/Poron, Ovaflex, Corlyte, and Vylite. Relatively durable. Good shock absorption. Used in forefoot extensions, top covers, and arch fill.

Spenco: This neoprene sponge bonded to a multi-stretch nylon fabric is capable of absorbing side-to-side forces (anti-sheer), as well as vertical pressure. Suitable for abrupt stopping and starting (sports.) Not heat moldable.

EVA: Ethyl vinyl acetate foam. Durometer of 40.

Closed Cell Foams: Offer good insulation and conforming properties.

Plastizote: Closed cell polyethylene. Comes in three densities, with durometers of 15, 23 and 40. Soft plastizote compressed as much as 20-30% without rebound, but with good force distribution. Low and medium densities are used as top covers to protect neuropathic feet or to accommodate plantar lesions. Aliplast and Pelite are in the same family. Pelite is non-allergenic. These materials eventually bottom out.

Corks: These highly shock absorbing and flexible materials are available in heat moldable and non-heat moldable forms. Examples of heat moldable corks are Thermocork, Birkocork and Ucocork. Non-heat moldable include Korex and Orthocork. Corks are used primarily for posting, arch fill and forefoot expensions. Heat moldables can also be used for accommodative shells.

Laminates: Laminated combinations of two or more materials combine the best qualities of those materials. One commercially available material, known as Diab-a-sheet, combines a bottom layer of energy absorbing PPT with a top layer of moldable plastizote. Another example is Tri-lam.

Corrections and Accommodations
There are many corrections and accommodations that can be specified by the Podiatrist. Some of the more common ones are:

Metatarsal Bar Pad: To transfer weight from the metatarsal heads proximally.

Dancers Pad: Metatarsal pad with a first ray cutout, to enable the first ray to seek its own level.

2-4 Met Pad: To redistribute weight away from the heads of plantarflexed metatarsals 2-4.

Heel Spur Pad: A ÒUÓ shaped pad to relieve pressure from the area of calcaneal insertion of the plantar fascia.

Heel Cushion: For those patients with a decreased heel fat pad.

MortonÕs Extension: Employed to limit ROM at the 1st MPJ when there is a short 1st Metatarsal, or Hallus Limitus or Rigidus with pain upon ambulation.

Toe Crest Pad: For those patients with hammertoes who have experienced greater foot comfort with a a crest pad supporting digitally contracted digits.

Neuroma Pad: A raise just distal to the metatarsal heads of the affected interspace, to spread the metatarsal heads and relieve the symptoms of the neuroma.

Neuroma Plug: Similar to a neuroma pad, but smaller and placed directly under the interspace between the metatarsal heads.

Schaphoid Pad: A raise under the medial arch, to allow for more cushioned pronation in a rigid device.

Individual lesions under the metatarsal heads can be accommodated but cutouts, providing the orthotic has sulcus for full length extension.

Cover Materials
Materials frequently used as top covers for their unique properties include Poron, Pelite, Spenco, and Plastizote. Naugahyde, a vinyl material with an appearance similar to leather, is frequently used because of its durability and cosmetic appearance. Naugahyde is available in many colors, can be readily cleaned, and maintains its original appearance for a long time. Cowhide breathes, but is susceptible to sweat and wear. Sweat resistant cowhide is available. It will discolor, but not breakdown with excessive perspiration. Horsehide, a more durable leather, is available. Also, for those applications where slip resistance is needed in a thin appliance, suede brown leather is available. Suede brown is less than half the thickness of conventional cowhide. Considerations must be made for allergies when selecting a topcover material. Suede is frequently used as a bottom cover for accommodative devices for cosmetic purposes. While it gives the orthotic a nice, finished appearance, it can also complicate adjustments.

Children's Orthotics

Children have a set of orthotics designed for the special needs of a lower extremity still capable of remodeling to some extent. They are as follows:

Gait Plates:These are for adducted or abducted gait patterns in very young children. These affect a cosmetic alteration to an abnormal gait pattern, and are capable of placing a stretching motion on tight capsular, ligamentous and tendinous structures. Heel Stabilizers types D & E (see below) are gait plates with a deep heel cup and flange extending up one side, depending on whether in or out-toeing is to be corrected.

In-Toe Gait Plate: For out-toeing problems. The medial side extends to the sulcus, tapering to cut out the 4th and 5th MTHÕs.

Out-Toe Gait Plate: For in-toeing problems. The lateral side extends to the sulcus, tapering to cut out the 1st and 2nd MTHÕs.

Heel Stabilizers: There are 5 different variations of this rigid orthotic for very young children, all featuring a deep heel cup for control of rearfoot pathomechanics.

Type A: For moderate pronation and heel eversion. The lateral flange extends to the cuboid. The medial flange extends to the middle of the 1st ray.

Type B: For moderate to severe pronation with forefoot pathology. The anterior end extends to all the metatarsal heads.

Type C: For a pronated, flaccid foot with forefoot splay. The lateral flange extends to the base of the 5th metatarsal.

Type D: For moderate to severe rearfoot pronation with tibial or femoral torsion leading to in-toeing. This device will create more out-toeing. The lateral side extends to the sulcus, and the medial flange to the talo-navicular joint.

Type E: For moderate to severe rearfoot pronation with tibial or femoral torsion leading to in-toeing. This device will create more in-toeing. The lateral flange extends to the cuboid. The medial side extends to the sulcus.

Shaffer Plate: For control of pronation in both children and adults, this is especially indicated for talo-navicular subluxation. This rigid device features a deep heel seat with a high medial flange.

Whitman Roberts: For the very young child with severe STJ pronation. Features a deep heel cup, high medial flange and lateral clip.

Functional Orthotics

Into this broad category fits all devices intended primarily to control foot pathology. The traditional rigid orthotic is the pure embodiment of biomechanical control. By definition, this device does not offer any cushioning or shock absorption. The demands of active patients have lead to the popularity of less rigid devices which trade-off some control for a critical measure of shock absorption. In particular, sport devices substitute polyethylene or polypropylene for composites or acrylics, often adding a crepe or other shock absorbing post, and shock absorbing arch fill or top cover. The type of sport is a key consideration, such as in determining how much jumping, starting or stopping, or side to side motion is required. These considerations will impact the design of the orthotic.

Types of Materials

Shell Materials

Composites: Graphite (e.g. TL-61 or TL-2100) is a typical example. Ideal for a strong, lightweight, thin rigid orthotic. Composed of two layers of carbon graphite with an acrylic core. Difficult to form a deep heel cup with.

Acrylics: The material of the classic rigid orthotic. Examples include Rohadur (no longer being manufactured) and Polydur. Polymers of methyl methylacrylate. Easily molded and modified. Highly durable.

Polyolefins: A rigid family of materials, but more flexible and shock absorbing than acrylics or composites, making them well suited for sports applications. Includes polyethylene and polypropylene. Polypropylene is the more rigid of the two. Ortholene and subortholene are types of polyethylene. The trade-off of greater flexibility is less control.

Posting Materials: Extrinsic posts are frequently made out of methyl methylacrylate for rigid orthotics. Sports devises might use EVA or crepes in durometers of 40 to 60.

Posting: Rigid orthotics are routinely posted to accommodate the varus or valgus rearfoot and forefoot dispositions. Intrinsic posts are ground out of the shell of the orthotic, while extrinsic posts are added to the shell. In general, intrinsic posts are most practical up to and including 3 degrees of correction, and extrinsic posting up to and including 6 degrees of correction. Seldom is more than 6 degrees of posting employed in an orthotic as the patient will slip off the device. If you are uncertain about how to post the orthotic you are prescribing, you can leave it to the discretion of the lab.

Final Reminders

Orthotics must be broken in gradually. Many orthotic manufacturers include break-in instructions with their orthotics. Also, many orthotics require modification in terms of grinding down or building up part of the orthotic in order to achieve comfort or the desired function.

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