What are Orthotics?

Orthotics are shoe inserts that are intended to correct an abnormal, or irregular, walking pattern. Orthotics are not truly or solely “arch supports,” although some people use those words to describe them, and they perhaps can best be understood with those words in mind. They perform functions that make standing, walking, and running more comfortable and efficient, by altering slightly the angles at which the foot strikes a walking or running surface.

Doctors of podiatric medicine prescribe orthotics as a conservative approach to many foot problems or as a method of control after certain types of foot surgery; their use is a highly successful, practical treatment form.

Orthotics take various forms and are constructed of various materials. All are concerned with improving foot function and minimizing stress forces that could ultimately cause foot deformity and pain.

Foot orthotics fall into three broad categories: those that produce structure changes (PCO), those that primarily attempt to change foot function, those that are primarily protective in nature, and those that combine functional control and protection.

Postural Control Orthotics

Rigid Orthotics

The so-called rigid orthotic device, designed to control function, may be made of a firm material such as plastic or carbon fiber, and is used primarily for walking or dress shoes. It is generally fabricated from a plaster of paris mold of the individual foot. The finished device normally extends along the sole of the heel to the ball or toes of the foot. It is worn mostly in closed shoes with a heel height under two inches. Because of the nature of the materials involved, very little alteration in shoe size is necessary.

Rigid orthotics are chiefly designed to control motion in two major foot joints, which lie directly below the ankle joint. These devices are long lasting, do not change shape, and are usually difficult to break. Strains, aches, and pains in the legs, thighs, and lower back may be due to abnormal function of the foot, or a slight difference in the length of the legs. In such cases, orthotics may improve or eliminate these symptoms, which may seem only remotely connected to foot function.

Soft Orthotics

The second, or soft, orthotic device helps to absorb shock, increase balance, and take pres- sure off uncomfortable or sore spots. It is usually constructed of soft, compressible materials, and may be molded by the action of the foot in walking or fashioned over a plaster impression of the foot. Also worn against the sole of the foot, it usually extends from the heel past the ball of the foot to include the toes.

The advantage of any soft orthotic device is that it may be easily adjusted to changing weight-bearing forces. The disadvantage is that it must be periodically replaced or refurbished. It is particularly effective for arthritic and grossly deformed feet where there is a loss of protective fatty tissue on the side of the foot. It is also widely used in the care of the diabetic foot. Because it is compressible, the soft orthotic is usually bulkier and may well require extra room in shoes, or prescription footwear.

Semirigid Orthotics

The third type of orthotic device (semirigid) provides for dynamic balance of the foot while walking or participating in sports. This orthotic is not a crutch, but an aid to the athlete. Each sport has its own demand and each sport orthotic needs to be constructed appropriately with the sport and the athlete taken into consideration. This functional dynamic orthotic helps guide the foot through proper functions, allowing the muscles and tendons to perform more efficiently. The classic, semirigid orthotic is constructed of layers of soft material, reinforced with more rigid materials.

Orthotics for Children

Orthotic devices are effective in the treatment of children with foot deformities. Most podi- atric physicians recommend that children with such deformities be placed in orthotics soon after they start walking, to stabilize the foot. The devices can be placed directly into a standard shoe, or an athletic shoe.

Usually, the orthotics need to be replaced when the child’s foot has grown two sizes. Different types of orthotics may be needed as the child’s foot develops, and changes shape.

The length of time a child needs orthotics varies considerably, depending on the seriousness of the deformity and how soon correction is addressed.

Other Types

Various other orthotics may be used for multidirectional sports or edge-control sports by cast- ing the foot within the ski boot, ice skate boot, or inline skate boot. Combinations of semiflexible material and soft material to accommodate painful areas are utilized for specific problems.

Research has shown that back problems frequently can be traced to a foot imbalance. It’s important for your podiatric physician to evaluate the lower extremity as a whole to provide for appropriate orthotic control for foot problems.

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Why Arch Support?

A concept, which has been present for perhaps hundreds of years, is that of arch support.

Early research in foot function identified three arches in the human foot. These arches were known as the medial longitudinal arch, the lateral longitudinal arch and the transverse metatarsal arch.

Early researchers recognized the significance in maintaining these arches as a requirement for asymptotic (pain free) foot function. They further recognized the destructive changes that occur in the arches when foot deformity and pain is present.

More recent researchers in the field of foot function have demonstrated the effect these arches have on the structures about them, i.e. ankle, tibia, and fibula, knee, femur, hip, pelvis, and vertebrae (back). They also identified medical

Problems, which exist in these structures that, were either aggravated by or caused by the malfunction of the arches in the foot.

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Historical Review

Records from the United States patent office use many different names to describe those inventions intended to improve foot and or arch function the "Orthotic". Detailed review of over 70 different registered inventions describes only two basic design techniques for orthotics. One technique builds a device by placing mass or substance in the arches of the foot; the other fabricates a plate-contoured to the plantar surface of the foot.

Many orthotic devices currently used today and first presented almost 100 years earlier strategically place mass so as to generate support to the medial longitudinal, lateral longitudinal and transverse metatarsal arches. Earlier orthotic inventions used the patients foot, then individual foot impressions and later shoe size formulas to generate the design of their arch supporting orthotic devices. Foot and or arch supports (orthotics) constructed in this fashion were recorded in both early and more recent patent literature.

Other inventions describe fabrication of a plate contoured to the plantar surface of the foot, using milling and bending techniques to contour the material to foot impressions or scanned coordinates. This contoured plate was further stabilized with a heel post designed to control the position of the plate during weight bearing or stance phase of the gait cycle. Additional varus wedging to the contoured plate, up to 10 degrees, has been described. Both extrinsic posts and intrinsic posts (changes in the contour of the plate from its original configuration) are described. Numerous variations in plate width and material used for construction are recorded. Review of the patent literature identified designs as early as 1924 that contoured metal, rubber and wood to cast impressions taken from individual feet. Many orthotic laboratories, using a variety of plastics and even a scanned digital image as the foot impression currently use this contoured plate method of fabrication.

Many types and combinations of material both natural and synthetic have been used to construct the orthotic devices reviewed. Some use materials that are soft and said to "cushion the foot". Others use material that is highly resistant to deformation, with expressed intent to support or stabilize. Many incorporate materials that both support and cushion foot function.

Orthotics constructed of steel, wood, plastics and hard rubber have all been used to generate relatively rigid plates. Foam rubber, water, air and a variety of compressible materials have been used as cushions for the foot.

In general inventions designed to fill the arches used softer materials, than those who contoured a plate did. Function of a foot control devise is increased with a material less deformed during stance phase of gait. The term functional orthotic, currently used to describe semi-rigid to rigid contoured plate orthotics may be generally applied, however all foot control devices alter the function of the foot.

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Quantifying an Orthotic Design

Quantification of orthotics  beyond current standards is necessary so as to produce devices that can be evaluated scientifically.

Parameters for Quantification

Following is a review of orthotic design those characteristics related to the ability of a device to control foot function were identified and defined in mathematical terms.

The potential advantage of a material that can reduce shock is clear, if that were the primary intent here a flat piece of material with physical properties demonstrating the highest elastic modulus would suffice. It is the intent here to quantify those physical characteristics of an orthotic that alter foot position during function. It is accepted that a device designed to control position of foot function may benefit from the addition of shock absorption characteristics.

The ability of a material to resist deformation must be considered in any measurement or quantifying process. When the material used for construction does not compress during function the physical support is equal to a non-weight bearing measurement. If the material compresses then physical support characteristics of the device would be reduced accordingly during stance phase of gait. Any quantifying process must consider the compressibility of the material used for construction. Although it is generally accepted that foot control takes place primarily during stance, or weight bearing, phase of gait. It is not as well defined as to which portions of Stance Phase are of primary concern.

Biomechanical examination of the lower extremity may reveal as much as 20 degrees of varus positioning of the rear foot at heal contact. This suggests a strong need to begin foot control early during stance phase of gait. . In fact both medial and lateral wedging of the most proximal cupola of the orthotic has and is currently attempted. Several authors contend that the spherical design of the heel of the foot and the cupola of the orthotic obviate any benefit of extrinsic posting during early heal contact.

The next functional phase is that portion of time between heel contact and mid-stance when the foot is resting fully on the highest part of the devise. As the plantar surface of the foot becomes less spherical past mid heal on the orthotic, wedging applied after this point would have a much greater effect on foot function. Many of the inventions described placement of the varus wedging beginning in the middle and others at the end of the orthotic cupola. They all described a gradual increase in the slope of the wedge extending to a point in the middle of the arch near or at the Talo-Navicular Joint (TNJ). Contoured plate orthotics generate additional varus wedging to a point near the TNJ, at this point the plate is bent plantar grade so as to maintain the proximal part of the plate in the more varus position.

Clearly from middle to late heal contact through all of midstance those physical characteristics of an orthotic device associated with foot function are most important. Although important elements of foot function occur during propulsion most authors agree foot position at the end of mid-stance sets the stage for what will happen in propulsion. Some inventions reviewed added small amounts of mass beyond the metatarsals, many added cushion to the metatarsal head region. Contoured plate design terminated proximal to the metatarsals in all patents reviewed. Other than the transverse metatarsal arch reported in most designs, placed proximal to the metatarsal heads, few researchers attempted to alter foot function during propulsion. Shock absorption was the only frequent physical embodiment utilized during propulsive phase of gait.

In 1987 Dr. Nick Grumbine stated, "The level of therapy of a functional orthotic is directly proportional to the amount of control afforded to the supported foot.   Such control stems from the effectiveness of the orthotic in holding or supporting the foot, and all it’s component parts at specific angles." It is this level of therapy that we desire to quantify. Without a definition of a critical angle, measurement or quantification is not possible.

When viewed clinically, or even through the "eyes" of computer assisted technology, a predominant varus angulation is observed in a plate contoured to the plantar surface of a human foot. This varus angulation begins where the plate cups the heel, increases distally to an area corresponding with the TNJ, and then decreases to the metatarsal head. Points on the superior surface of the plate and the horizontal plane create this angle.

Regardless of the actual angle all plates progressively increase from 0 where the plate joins the cupola to a maximum angulation at a point in the center of the arch more specifically the TNJ of the foot, and then decreases to 0 again before the metatarsal heads. In fact measurement of this varus angulation at any given point from heal to metatarsal area is a function of the varus angulation measured at the TNJ or apex of the orthotic. Therefore, measurement of the varus angulation at the apex establishes and defines the varus angulation of the entire plate from heel to metatarsal area.

A Logical section for measurement of this angle, created by the superior surface of the contoured plate and the horizontal plane, is that portion of the plate measuring the greatest angulation more specifically, a part of the plate that consistently corresponds with the TNJ. A frontal plane section through the apex region of an orthotic can be identified and the superior surface of the plate can be related to the horizontal plane in terms of degrees.

Efforts to plot, or attempts to represent this angular relationship between the superior surface and the horizontal plane at the specified frontal section created immediate difficulty. Whereas the proximal portion of the plate is cupola in design, the portion of the plate corresponding with the apex is hyperbolic, having a portion of the curve that is more planer laterally and more inclined medially. The point to be the apex of the varus angle located on the horizontal plane was directly under the lowest lateral part of the curve. This point was approximately 25 % of the orthotic width from the most lateral part of the curve. A point on the most medial superior surface was identified and used to finish the angular measurement. It was quickly apparent that if the orthotic was narrowed significantly the angle changed dramatically. Three years of effort to relate orthotic function to this described angular measurement failed to produce a consistent statistical relationship.

When the most medial and vertical part of the hyperbolic curve is used the angular measurement is recorded much higher than if the central 50 percent of the curve is used. Basically when that part of the contoured plate and finished orthotic known as the medial phalange is used as part of the angular measurement, the measurement is 10 to 20 degrees higher.

The patent literature revealed considerable controversy concerning that part of orthotic design referred to as the medial flange. Some patents designed two options of their invention one with and one with out a medial flange. One current orthotic fabrication technique eliminated the medial flange in the finished orthotics by using a fill process on the positive mould before the contoured plate was formed. Points on the curve representing the medial flange were then eliminated from the angular measurement.

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Rigid Orthotics

The so called rigid orthotic device, designed to control function, may be made of a firm material such as plastic or carbon fiber, and is used primarily for walking or dress shoes. It is generally fabricated from a plaster of paris mold of the individual foot. The finished device normally extends along the sole of the heel to the ball or toes of the foot. It is worn mostly in closed shoes with a heel height under two inches. Because of the nature of the materials involved, very little alteration in shoe size is necessary.

Rigid orthotics are chiefly designed to control motion in two major foot joints, which lie directly below the ankle joint. These devices are long lasting, do not change shape, and are usually difficult to break. Strains, aches, and pains in the legs, thighs, and lower back may be due to abnormal function of the foot, or a slight difference in the length of the legs. In such cases, orthotics may improve or eliminate these symptoms, which may seem only remotely connected to foot function.

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The Postural Control Orthotic

Problems arise from abnormal arch function, therefore, one would expect that the benefit of orthotics (arch supports) would be related to the ability of the orthotic to restore "normal arch function." If the orthotic were capable of restoring only 10% improvement in arch function, a relatively small improvement in pain or deformity would be expected. On the other hand, if an orthotic restored 90% or more of "normal arch function", a significant improvement in pain and deformity in all joints, muscles and nerves of the body would be expected.

In our estimation the following types of arch supports offer these levels of restoration or "normal arch function":

• Foot levelers (as dispensed by many chiropractors) 10-15%
• Geriatric Orthotics (as dispensed by many podiatrists) 15-20%
• Orthotics (as dispensed by local a certified prosthesis Orthotist)15-25%
• Functional Orthotics (as dispensed by many podiatrists) 10-35%
• PCO Orthotics ( from Postural Control Laboratories ) 65-95

In addition to the ability of the Orthotics to control arch function, it is also important that the Orthotics work in shoe gear, as the orthotic must be worn whenever you are on your feet in order to see maximum benefit.

Interestingly, when you control the arches upward of 80% of normal, the foot actually decreases in size both length and width, and a smaller shoe is often required. When the orthotics are functioning properly, they work in most all shoe types.

Orthotics, when functioning in a range of 70-100 % will relieve pain in feet, ankle, knee, hip, low and upper back to a degree that is often described to me as "unbelievable."

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Semi-rigid Orthotics

The semi rigid device provides for dynamic balance of the foot while walking or participating in sports. This orthotic is not a crutch, but an aid to the athlete. Each sport has its own demand and each sport orthotic needs to be constructed appropriately with the sport and the athlete taken into consideration. This functional dynamic orthotic helps guide the foot through proper functions, allowing the muscles and tendons to perform more efficiently. The classic, semi rigid orthotic is constructed of layers of soft material, reinforced with more rigid materials.

Back to Top

Soft Orthotics

Soft, orthotic device helps to absorb shock, increase balance, and take pres- sure off uncomfortable or sore spots. It is usually constructed of soft, compressible materials, and may be molded by the action of the foot in walking or fashioned over a plaster impression of the foot. Also worn against the sole of the foot, it usually extends from the heel past the ball of the foot to include the toes.

The advantage of any soft orthotic device is that it may be easily adjusted to changing weight-bearing forces. The disadvantage is that it must be periodically replaced or refurbished. It is particularly effective for arthritic and grossly deformed feet where there is a loss of protective fatty tissue on the side of the foot. It is also widely used in the care of the diabetic foot. Because it is compressible, the soft orthotic is usually bulkier and may well require extra room in shoes, or prescription footwear.

Back to Top

Orthotics for Children

Orthotic devices are effective in the treatment of children with foot deformities. Most podiatric physicians recommend that children with such deformities be placed in orthotics soon after they start walking, to stabilize the foot. The devices can be placed directly into a standard shoe, or an athletic shoe.

Usually, the orthotics need to be replaced when the child’s foot has grown two sizes. Different types of orthotics may be needed as the child’s foot develops, and changes shape.

The length of time a child needs orthotics varies considerably, depending on the seriousness of the deformity and how soon correction is addressed.

Back to Top

Other Types of Orthotics

Various other orthotics may be used for multidirectional sports or edge control sports by casting the foot within the ski boot, ice skate boot, or inline skate boot. Combinations of semi flexible material and soft material to accommodate painful areas are utilized for specific problems.

Research has shown that back problems frequently can be traced to a foot imbalance. It’s important for your podiatric physician to evaluate the lower extremity as a whole to provide for appropriate orthotic control for foot problems.

The Postural Control Orthotic (PCO) will fit these special requirement much better, with more control than devices that have to be casted with the foot inside the boot.  Another benefit of the PCO is, unlike the ridged type Orthotic, they will not tear or break down the inside of the boot.

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