Foot Orthotics

Orthotics:

Orthotics refers to both field of study and external devices used to support or correct musculoskeletal deformities and /or abnormalities. These also helps to improve the function of movable parts of the body. Orthotics combines biomechanics, anatomy and material science to provide therapeutic support and improve patient quality of life through external devices. These include Braces, splints and supports for the back, knee, arm, wrist, foot …etc.

Foot orthotics, also called orthoses or shoe inserts, are devices worn inside shoes to provide support and improve foot function. These modifications can be customized in footwears as well to give preventive and therapeutic benefits. Foot orthotics aim to support the foot, redistribute pressure, and improve biomechanics. They can help correct structural problems like high arches or flat feet. Orthotics can reduce pain, improve foot alignment, and help prevent or delay the need for surgery.

Before diving deep into the modifications it’s good to know the parts of a shoe, The basic anatomy of a shoe.

Orthotics are also made up of variety of materials like Polyurethane, EVA – (MCR – Micro Cellular Rubber & MCP – Micro Cellular Polymer), Silicon, Plastic, Plastazote (Foam)… Every individual need is different and so is the orthotic material need. When considering the material to be used the factors to be taken into account include

• Patient Weight: Heavier the patient the denser or harder the material to be. Hardness of the material (Esp the ones used in footwears) is measured with an instrument called durometer and Its unit is called Shore A Hardness. The values are in the range of 0 to 100 with 0 being very Soft to 100 being hard. For footwear insoles, studies have shown a Shore value of 15 to 25 is ideal. This hardness helps to dissipate pressure, relieve pain and suits diabetic patients. MCP made of this shore value is called Medical Grade MCP. At Rx Surgicals only medical grade MCP are used. When the shore value is lower than this the material becomes very soft, which only causes a compression at the point of contact and pressure dissipation is limited. When the shore value is higher than 25 the material becomes harder and that too does not help to relieve the pain as it exerts a counter pressure on your foot.
• Biomechanical need: If the purpose is correction more rigid materials are needed. Esp for correction of Arch and Plantar fasciitis. But if the patient needs more comfort because of pain softer materials or semi rigid materials that accommodate pressure is to be used. Softer materials like Eva, Silicon and Plastazote are used for patients with Diabetes, Callus and Corns.

Generally, for footwears modifications the materials are selected as per the individuals need. However, the most commonly used material for customization is MCP and MCR.

What’s the difference between MCP and MCR

Microcellular Rubber (MCR) and Microcellular Polymer (MCP) are both materials used to manufacture footwears. They have micropores which allows pressure dissipation.

• MCR is made from natural or synthetic rubber. MCP is made from a variety of materials, including polyurethane or EVA (ethylene-vinyl acetate).
• MCR is denser than MCP, and so heavier than MCP. MCP is more flexible than MCR, and make it more comfortable
• MCR produces heat over long standing, MCP produces significantly less heat.
• MCR being rubber tends to become more brittle.

All through we have mostly talked about the insole. Let’s touch upon the other components as well

Since these footwear modifications are needed for elderly patients as well the grip on outer sole is an important criterion to be looked into. The treads on the outer sole have to well designed for firm grip and traction. Also, if the patient is having diabetic neuropathy the outer sole has to be rigid and preferably a Rocker bottom. I will explain more on it when coming to Diabetic footwears.

If the patient has a forefoot issue its always better to avoid slip-ons and footwear with a toe stick. This is because when the person walks the footwear tends to come off and to hold the footwear in place, the person holds on firmly to the toe stick for grip which in turn exerts increased pressure in the forefoot region leading to callus, corns, Bunion …In this case, If you notice the footwear tends to have pressure impressions on the 1st metatarsal head and the digits.

Since this footwear modification are also to be done for diabetic patient’s utmost care to be given for the inner lining of the footwear. It has to be soft and preferably seamless. Materials like poly cotton or MCP lining helps as a suitable inner liner.

Now we know in general what to look for in foot orthotics, let’s go into specifics Which conditions require specific orthotics and what kind of orthotics

You require orthotics for any of the following foot and ankle conditions:

Flat Feet

As discussed earlier its important to address the flat feet issues with Medial Arch Footwear. This helps to restore the balance and prevent pronation. If the deformity is very prominent you may require additionally a medial wedge along with arch to compensate the pronation.

Pronation /Supination

Generally, person with high Arch the foot tends to shift laterally and in order to balance it a lateral wedge correction will be helpful. Also, if you note when the arch is collapsed and the foot pronated it also leads to knock knee leading to increased friction of the knee joint laterally.

This may lead to development of Osteo Arthritis. The other way round with high arch and foot supinated it leads to bow leg pattern and the friction in the knee is more medial. The wedge height is determined with the angle of pronation or supination. In some case you may also note the hind foot is Supinated while the forefoot is pronated. With proper plantar analysis its important to have the wedges accordingly compensating the hind foot and fore foot pressure. Heel can also be supported with a cup shaped elevation (Gobra Heel) for better comfort and fit.

Metatarsalgia

In case of forefoot pain or callus, the pain can be reduced by offloading the metatarsal region. In the initial stages a simple metatarsal bar or pad will help to relieve the pressure in the forefoot. This can be incorporated in the footwear or can be done as insoles for the shoe. Its preferable to have footwear without toe sticks to reduce the forefoot pressure.

Bunion (Hallux Valgus)

Toe separators incorporated in the footwear or separately made of silicone helps to prevent further deterioration. Silicon toe separators also come with Bunion shield this help especially while wearing shoes, preventing chaffing. Bunion splints are apt as night splints. These exert 3 way force – pulls the toe outwards, pushes the bunion inwards and also the splint incorporates transverse arch which gives further support at the metatarsal region.

In certain cases, foot alignment socks also help as toe separator for all five fingers.

Corns and Calluses

Off loading corns and calluses involves multiple approaches depending on the region and aggressiveness.

Depending on region, If the corn or callus is in the forefoot as said earlier footwear with toe sticks is to be avoided. The foot has to rest completely in the footwear. For a shoe it has to have wides and higher toe box so that the foot does not rub with any material.

If the corn or callus is mild addition of 5 mm latex or silicon layer will help to distribute the pressure. If the corn is painful, offloading that region is important. Scooping can be done for small corns provided the surrounding tissue is healthy and viable. For corn in the digits a metatarsal bar will be helpful to reduce the pressure in the forefoot. Please note heel footwear to be avoided for persons with corn in the forefoot region. If the corn is on the lateral or medial aspect a suitable wedge can be added after analysing the walking pattern. A small corn in the heel can be addressed by adding a 15mm heel to the footwear, where in the pressure gets bio mechanically shifted.