IDS ::: Orthotics ::: FFO's: Insoles

Functional Foot Orthoses (FFO's) are effectively a type of corrective orthotic insoles. In very basic terms these orthoses can have two functions:

To improve the bio mechanics of the foot and ankle by altering the position or internal alignment in the stance phase of the gait cycle e.g. by using an orthosis to prevent hyperpronation. Corrective Insoles
To protect the foot from potentially damaging forces or pressures.
e.g. by using a total contact insole to avoid peaks of pressure on a sole which would be vulnerable to ulceration. Accommodative Insoles

Note: occasionally a combination of both functions can be applied.

Corrective insoles.

These are designed to biomechanically improve the position and function of the foot and ankle. One of the most common conditions where they are used is for hyperpronated foot. In this situation the foot is considered to be excessively pronated. Pronation naturally occurs during the gait cycle but excessive pronation can cause a range of debilitating conditions. Insoles designed to prevent this are available both ‘off the shelf’ (OTS) and custom made. Supporting the longitudinal arch of the foot and by wedging (known as posting) the range of pronation is reduced. These insoles are used for a very wide range of patients from paediatric to geriatric including international athletes. They are made from a variety of vacuum formed foams available in different densities and from stiff plastics and laminates such as carbon fibre.

Accommodative insoles

These are used in situations where re-distribution of contact pressures and/or mechanical protection is required. Two common conditions where insoles of this type are used are for diabetic and for rheumatoid patients. Some of the complications which can occur with IDDM include peripheral neuropathy and reduced vascular efficiency. These can lead to ulceration. To reduce the risk of this or to encourage the healing of minor ulceration, an insole can be used which reduces the peaks of pressure which, often occur over bony prominences. This is done by shaping the insoles to achieve total contact. Mechanical protection can be achieved by constructing the insole from a variety of soft materials such as PPT and EVA.

The same principles can be applied to some RA patients whose feet can be painful and at risk of ulceration because of the deformation and reduced flexibility which RA often causes.

For feet in these categories it is generally not advisable to try to correct the position of the feet significantly. This is especially true with diabetics where correction forces would actually create the peaks of pressure which the insole is designed to reduce.

Functional Foot Orthoses (FFO's) are effectively a type of corrective orthotic insole. They are of a slim design, incorporating posting (accurate wedging) into or onto a relatively rigid shaped shell. These orthoses are never used for accommodative purposes. The term "functional" might be considered to be unhelpful as the possible inference is that other orthotic insoles are "non-functional".

Functional Foot Orthoses (FFOs)

Accommodative insole showing layers of protective / supportive materials.

A cavus foot. Cavus feet are usually stiff feet. Little change to position can be achieved but such stiff feet may require biomechanical protection, especially around the metatarsal heads.

A planus foot

A very hyper-pronated foot. If the pronation is mobile the position can be improved while being supported by a corrective insole.

A typical hyperpronation callus pattern on an elderly foot, showing callus on 2nd and 3rd metatarsal heads and on the hallux but not on the 1st metatarsal head.

The windlass test indicates that the windlass effect restores (briefly) the longtitudial arch and that any calcaneo valgum is mobile and correctable.

Diabetes can cause vascular and neurological degeneration which increase the risk of ulceration. This risk can be further increased by any biomechanical problems which create pressure peaks. A combination of total contact insoles and correctly fitting diabetic specification footwear can provide protection against ulceration. Diabetic ulcers can be difficult to heal. Many lower limb amputations are the end result of a process which began as a foot ulcer.

A diabetic foot showing the early signs of deterioration

Showing a diabetic ulcer which although not an open wound, is well established under the skin. This patient has already lost toes to ulceration.

A very deep ulcer. This ulcer is too severe to be treated by total contact insoles. A pressurised “boot” such as an Aircast may be appropriate.

This patient had lost an entire ray as a result of ulceration. The “sandal” which he was wearing was not ideal. The total contact insole and diabetic shoe (shown on either side) provided much more protection both from biomechanical forces and the elements.

Showing a Charcot foot

Finding subtalar neutral at assessment or casting for an insole or FFO

Identifying anatomical landmarks prior to casting for a insole or FFO.

Taking a plaster of paris cast for an insole or FFO

Fracture Braces

Some specially designed AFO's are used as fracture braces. These are covered under the Fracture Brace section. Click here to return to Orthotic Categories.

Neuropathic Foot

A powerpoint presentation on this topic, which was given to the Diabetic Federation of Ireland is available here for viewing. Click here to find out more

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