Terms and Definitions

Orthosis A device utilized to assist, resist, facilitate, stabilize or improve range of motion and functional capacity of various joints in the body.
Functional Foot Orthosis A custom or prefabricated device utilized to treat mechanical pathologies of the foot that may be structural or functional in nature.
Accommodative Foot Orthosis An orthotic device that supports the foot but does not attempt to align the joints of the foot during stance or gait.
Custom Foot Orthosis A device derived from a three-dimensional mold of the patient's foot. This device may be functional or accommodative and is based on a prescription.
Rigid Functional Orthosis A functional foot orthosis made to maximally prevent abnormal motion or abnormal position of the foot and leg during gait. The device should be made with a rigid material that displays minimal flexibility during use. Material rigidity is a function of material thickness, intrinsic rigidity of the material, orthotic plate size, patient weight, and the degree of instability of the foot.
Semirigid Functional Orthosis A functional foot orthosis used to partially control abnormal motion or abnormal position of the foot and leg during gait. This device is made from a material that displays moderate flexibility during use. Material rigidity is a function of material thickness, intrinsic rigidity of the material, orthotic plate size, patient weight, and the degree of instability of the foot.
Flexible Functional Orthosis A functional foot orthosis is used to partially control abnormal motion or abnormal position of the foot and leg during gait. This device is made from a material that displays significant flexibility during use. Material rigidity is a function of material thickness, intrinsic rigidity of the material, orthotic plate size, patient weight, and the degree of instability of the foot.
Orthotic Prescription A doctor’s order to an orthotic laboratory based on a thorough structural and functional assessment of the patient, as well as an evaluation in stance and in gait. The prescription describes materials, corrections and the corrective functions of a custom foot orthoses
Pathology Specific Custom Foot Orthosis™ A functional foot orthosis that is prescribed using evidence found in the medical literature to treat specific lower extremity pathology.
Insole Generic term for any device placed inside the shoe to support or cushion the foot.
Prefabricated Foot Orthosis A mass-produced foot orthosis made in various sizes and fit to a patient based on the size of their foot. A variety of materials and options are available.
Functional Prefabricated Foot Orthosis A prefabricated orthosis that is designed to alter foot function and to align the joints of the foot. Includes many features commonly found on custom orthoses including valgus forefoot support, rearfoot posts, and medial skives.
Kiddythotics™ Prefabricated Foot Orthosis A prefabricated orthosis used to treat pediatric flatfoot. The device has a rearfoot post, medial skive, medial flange, and a deep heel cup.
Accommodative Prefabricated Orthosis A device that supports the foot but does not attempt to align the joints of the foot during stance or gait. It is premade in various sizes and fit to the patient based on the size of their foot.
Customized Orthosis A prefabricated orthosis that has been modified with pads or wedges to meet the needs of a particular patient.
Dress Shoe Orthosis Any device specifically designed to fit the shank of the fashion or dress shoe and alter foot function. These devices can be fabricated from rigid, semirigid, or soft materials.
Cobra Orthosis A dress shoe device designed for high heel shoes to limit foot motion and relieve forefoot pressure. The lateral aspect of the orthosis and center of heel are cut away to decrease bulk in the shoe.
Diabetic Orthosis A device that provides total foot contact to disperse weight as evenly as possible throughout the plantar aspect of the foot and to reduce pressure from pre-ulcerative or ulcerative areas.

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CASTS

A plaster or digital molding of the patient’s foot in a particular position. This is sent to an orthotic laboratory for use in manufacturing custom orthoses. A foam impression is occasionally used for this purpose but only to fabricate custom accommodative orthoses.

Cast Corrections

Modifications to the mold of the patient’s foot based on the orthotic prescription. These modifications change the shape of the positive mold in order to change the function of the foot once an orthoses is made from this mold. They include arch fill, heel expansions, balance platforms, and lateral expansion.

CAD / CAM Cast Correction

The use of computer-aided design to perform the same corrections on computer that would be done on a plaster positive cast. Once the computer-generated positive cast is completed, a physical positive cast can be milled out of a block of wood, or the orthosis can be milled directly out of a block of polypropylene from a “virtual” positive.

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ORTHOTIC MATERIALS

Vacuum-Formed Polypropylene Used for custom functional orthosis. The shell is made from a sheet of polypropylene, heat formed over a corrected positive mold of the foot. This positive can be made of plaster or milled from a block of wood.
Direct-Milled Polypropylene Used for custom functional orthosis. The shell is milled directly out of a block of polypropylene based on the corrected “virtual” positive mold. Direct-milled polypropylene is more rigid compared to the same thickness of vacuum-formed polypropylene.
Graphite (Carbon Fiber) Used for custom functional orthoses. The shell is made from an extremely thin and lightweight material containing carbon fibers for strength. The material is formed over a corrected positive mold and is intended to fit in low volume footwear such as ice skates, ski boots and dress shoes.
EVA (Ethyl Vinyl Acetate) A closed-cell foam available in a medium (40 durometer) or firm (70 durometer) density. Used as an orthotic shell material for accommodative or functional custom orthoses, or as a topcover.
Plastazote® A lightweight, cross-linked foam used in the manufacturing of foot orthoses. Available in firm (black), medium (white), and soft (pink). Firm Plastazote is used as the shell material for custom diabetic foot orthoses.
P-Cell® P-Cell is a closed-cell EVA foam used as a topcover material for foot orthoses.

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REARFOOT POST

Standard Extrinsic Rearfoot Post Material added to the inferior surface of the heel of the orthotic shell to increase the contact area and to stabilize or invert the orthosis at heel contact.
Spot Grind The inferior surface of the heel of orthotic shell is ground to increase the contact area and to stabilize or invert the orthosis at heel contact without adding an extrinsic rearfoot post. Also known as an intrinsic rearfoot post.
Strip Post A rearfoot post in which only the distal half of the post is applied. This leaves the proximal heel of the orthosis free of posting and facilitates fit in dress shoes.
Hole Grind A spot grind that goes all the way through the polypropylene, creating a hole in the heel of the orthosis. Allows the orthosis to sit very low in the shoe.
Rearfoot Post Motion The rearfoot post can be ground flat or with motion. How it is ground is denoted by a number such as 0/0 or 4/4 where the first number denotes the amount of inversion of the lateral aspect of the post and the second number denotes how much motion is allowed. So a 4/4 post is inverted 4 degrees on the lateral aspect and allows 4 degrees of eversion to bring the medial side of the post to the ground. In this case the medial side of the post is ground so that it is parallel with the front edge of the orthosis. For a 0/0 post, the rearfoot post is ground parallel to the front edge of the orthosis.
No Post Bevel Typically, the sides of the rearfoot post are beveled at a 20 degree angle to facilitate shoe fit. No post bevel means that the medial and/or lateral aspect of the post will be left at 90 degrees to the supporting surface. This will increase either the supinatory torque (no medial bevel) or pronatory torque (no lateral bevel), and increase the surface contact area at the heel.

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ORTHOTIC SIZE

Heel Cup Depth (height) The vertical distance between the heel contact point of the positive and the circumscription line of the heel cup on the positive representation of the foot.
Orthotic Width The width of the distal edge of the orthosis. The lateral aspect of the orthosis is always flush with the lateral border of the foot, whereas the medial aspect varies based on the prescription.
Narrow Width Distal medial edge of orthosis extends medially to the lateral aspect of the lateral sesamoid.
Standard Width Distal medial edge of the orthosis extends medially to a bisection of the sesamoids.
Wide Width Distal medial edge of orthosis extends medially to the medial aspect of the medial sesamoid.

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CASTWORK

Cast Fill Plaster added to the medial arch of the positive cast. The less cast fill that is added, the tighter the orthosis will conform to the arch of the foot. More cast fill results in a greater gap between the orthosis and the arch of the foot. ProLab offers the following casts fills: Very minimum - No plaster is added (highest arch) Minimum Standard Maximum (lowest arch)
Lateral Heel Skive The plantar lateral heel area of the positive cast is "flattened" to create a valgus wedge effect within the heel cup. This causes the center of the force that the orthosis is applying to the heel to shift laterally, increases pronatory torque, and acts to limit inversion or encourage eversion of the rearfoot on the orthosis. This modification is useful when treating pathologies caused by excessive supination such as lateral ankle instability, pes cavus and medial knee osteoarthritis.
Medial Heel Skive The plantar medial heel area of the positive cast is flattened to create a varus wedge effect within the heel cup. This causes the center of force that the orthosis is applying to the heel to shift medially, increases supinatory torque, and stabilizes or inverts the rearfoot on the orthosis. This technique is also known as a “Kirby skive”.
Inversion A cast correction technique used to artificially increase the medial arch of the device, move the apex distally, and shift the center of the heel cup laterally. The positive cast is balanced with the heel in an inverted position relative to the supporting surface. The clinician can prescribe from 1 - 10 degrees of inversion without having to use a Blake inverted technique.
Blake Inversion Blake inversion refers to balancing the positive cast more than 10 degrees inverted. Additional modifications are performed to make the arch height tolerable. This technique is available only in plaster. ProLab clients can contact a Medical Consultant to discuss alternative techniques.
Medial Flange An increase in the height of the orthosis on the medial side of the device starting just distal to the heel and extending to the distal edge with the apex near the navicular. The height of the flange area of the medial arch varies with the foot shape. This modification also makes the orthosis slightly wider at the area of the medial arch.
Plantar Fascial Groove A groove pressed into the orthosis to accommodate a prominent plantar fascia. This can only be fabricated on a vacuum-formed cast.
1^st Metatarsal Cut-out The medial corner of the orthosis plate is removed starting distally from the 1st intermetatarsal space and extending proximally to the 1st metatarsal neck. The intent is to further plantarflex the 1^st ray. Caution: this technique also narrows the distal edge.
1^st Ray Cut-out The medial corner of the orthosis plate is removed starting distally from the 1st intermetatarsal space and extending proximally to the 1st metatarsal base. The intent is to further plantarflex the 1^st ray. Caution: this technique also narrows the distal edge.
Sweet Spot A pocket pressed into an orthotic shell and filled with Poron to accommodate a plantar prominence. It is commonly used to accommodate a prominent navicular tuberosity. Only available on vacuum-formed devices.

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TOPCOVERS

Topcover Any material used to act as an interface between the device and the foot. It is intended to cushion, finish or give the orthosis better wear resistance.
Topcover Materials Soft EVA Description: Closed-foam single layer material (40 durometer) Advantages: Long-lasting, initially provides good cushion, mildly rigid so it slides into shoes quite easily, conforms easily to curvatures such as deep heel cups, resistant to tearing, excellent for in-office use. Disadvantages: Compresses with use, some patients find it hot with increased friction compared to other materials. Firm EVA Description: Closed-foam single layer material. (70 durometer) Advantages: Long-lasting, resistant to tearing, very rigid so it slides into shoes very easily, works well as a heel lift, aperture or when a rigid forefoot extension is necessary Disadvantages: Very little cushion, some patients find it hot with increased friction compared to other materials. Overall, it is an excellent material for creating accommodations, but is not a particularly comfortable topcover. Leather Description: Cowhide Advantages: Long-lasting, thin, resistant to tearing, absorbs moisture, minimal friction, excellent topcover in combination with other cushioning layers Disadvantages: No cushion (requires additional layers if cushion is desired), absorbs moisture and remains damp, and stains. Vinyl Description: Synthetic leather-type material Advantages: Very tough, long-lasting, extremely thin, resistant to tearing, does not absorb moisture, minimal friction, excellent topcover in combination with other cushioning layers Disadvantages: No cushion (requires additional layers if cushion is desired), some patients find it hot. Nylene Description: Two-layer material composed of a closed-cell neoprene bottom layer glued to a nylon top layer Advantages: Excellent cushion, cushion does not tend to compress much over time, nylon top layer has low coefficient of friction, resistant to tearing Disadvantages: Very flexible making it somewhat difficult to slide into shoe, difficult to conform to very deep heel cups. Sport Description: A two-layer 3mm topcover with a bottom layer of high-rebound EVA and top layer of synthetic suede Advantages: Top layer has low coefficient of friction, resistant to tearing, good cushion, relatively rigid to facilitate ease of sliding into shoe, and a pleasant “feel”, making it an excellent topcover choice Disadvantages: Slightly higher cost than single layer covers Diabetic Description: Three-layer material with leather top, P-cell middle layer and Poron bottom layer Advantages: Leather offers low friction and absorbs moisture, P-cell compresses to accommodate prominences. Poron offers cushion Disadvantages: Leather can stain. This type of cover should be replaced regularly to meet the needs of the high-risk foot type
Poron Underlayer A layer of Poron can be glued to the bottom of any of the covers listed above for additional cushion. Available in 1.5mm or 3mm. Poron is an open-cell foam that maintains cushion for long periods without compressing. Poron is not usually used as topcover alone because it easily wears if in contact with the skin.
Bottom Cover Material added to the bottom of the orthotic shell to finish the orthosis and protect it from wear. Common materials are leather, suede, vinyl, and firm EVA.
Length Denotes the distal length of the topcover. The following lengths are available at ProLab: To Mets: Cover ends at distal end of orthotic plate To Sulcus: Cover extends under the metatarsal heads To Toes: Cover extends to the end of the shoe
Topcover Gluing Options Partial Glue: ProLab offers the option of gluing the topcover in the heel only or posterior half only. This option allows accommodations or modifications to be added later in the doctor’s office. Glue All: The topover is completely glued on to the orthotic device.

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FOREFOOT EXTENSIONS

Forefoot Extension Material added to the bottom of the topcover, just distal to the front of the orthosis. Used to provide additional cushion, control or accommodation.
Morton’s Extension Material added under the first metatarsalphalangeal joint from the distal end of the orthotic shell. Designed to limit first metatarsalphalangeal range of motion. Default material: Korex.
Reverse Morton’s Extension Material extends from the distal aspect of shell to the sulcus under 2-5 metatarsal heads to increase first ray range of motion. Default material: Korex.
Varus Extension Material extends from distal aspect of shell to level of sulcus and is thicker medially and tapers until there is no material under the 5th metatarsal head. Designed to support a varus forefoot. Default material: Firm EVA.
Valgus Extension Material extends from distal aspect of shell to level of sulcus and is thicker laterally and tapers until there is no material under the 1st metatarsal head. Designed to support a valgus forefoot. Default material: Firm EVA.
Slot Accommodation A forefoot extension designed to offweight specific metatatarsal heads by creating a rectangular aperture under the metatarsal head that is to be offweighted.
Punch Accommodation A forefoot extension designed to offweight specific metatatarsal heads by creating a circular aperture under the metatarsal head that is to be offweighted.

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ORTHOTIC ADDITIONS

Heel Lift Material added to the inferior surface of the orthotic heel post to elevate the heel relative to the supporting surface. Rearfoot post must be present to apply lift.
Extension Any non-rigid material added to the orthosis extending its length beyond the metatarsal heads. Topcover to the sulcus or toes must be present to apply the extension.
Eva Arch Fill Medium or firm density EVA added under the arch area of the orthotic plate. The EVA fill increases the rigidity of the orthosis by preventing arch collapse. It also creates a flat bottom surface of the orthosis which allows the addition of plantar wedges or lifts that extend the length of the orthosis.
Metatarsal Pad Tear-shaped modification added to the top of the orthosis under a topcover. Typically, it begins at midshaft of the metatarsals and terminates just proximal to the heads of the metatarsals. It is highest in the center and lower at the edges. It acts to shift pressure from the metatarsal heads to the metatarsal shafts (usually centered at 3^rdmetatarsal).
Metatarsal Bar A piece of Poron, usually 3mm thickness, added to the distal edge of the orthosis shell and covers the distal 15% of the orthotic shell. It is designed to transfer force off of the metatarsal heads and onto the metatarsal necks and shafts.
Neuroma Pad A dome-shaped pad placed in the metatarsal interspace between the metatarsal heads. It starts at the proximal third of the metatarsal shafts and ends at the metatarsal heads. The specific interspace must be noted.
Arch (Scaphoid) Pad A pad that is plantar and medial to the longitudinal arch and gives extra support and padding to medial arch area. The pad is applied to the dorsal surface of the orthotic shell.
Cuboid Pad A wedge-shaped pad that is placed plantar to the cuboid bone on the dorsal surface of the orthotic shell. This pad raises the medial border of the cuboid relative to the supporting surface and is intended to invert the cuboid.
Heel Pad Resilient material applied to the dorsal surface of the orthotic shell and covers the entire heel cup to cushion the heel. Default material: Poron.
Horseshoe Pad (Heel Spur Accommodation) An oval, concave, or horseshoe shaped pad that creates a depression in the heel area of the orthotic shell. It is positioned plantar to the medial tubercle of the calcaneus and is used to offweight this area and increase shock absorption.
Toe Filler An addition to the topcover of the orthosis that fills the space left after toe amputation. Shoes must be sent to the lab to make this accommodation.