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Footwear Adaptions

Footwear Adaptions

Footwear adaptions or modifications are commonly utilised by orthotist to influence the biomechanics of someone’s gait often by manipulating the ground reaction force (GRF).

The aim of these modifications could be to increase stability or make a certain motion less likely. Clinicians will often use such modifications when other force application methods are impractical. One example would be wedging on insoles. There is generally a limit to how much can be placed inside of a shoe.

Flares

Flares or Floats are a standard orthotic intervention. The adaption increases either the medial or lateral side of the sole unit. While most effective as a heel flare, forefoot flares can also be done.

The mechanical aim is to increase the lever arm of the ground reaction force on the subtalar joint. 

It is often used in supinating feet as the increased lateral position at initial contact will create a larger pronatory moment at heel strike. It can also speed up the rate of pronation, so it may cause pronation related complaints if misused. In fact, it was a common sole feature of some running shoes to have a lateral heel skive to try and reduce the length of the lateral lever arm at heel strike

 This manipulation of the GRF is a feature of a number of adaptions that can be used to improve patients' mobility. 

Posterior heel flare

 This is added to pull the GRF back to increase the lever arm at heel strike, causing an increased plantarflexion moment at heel strike.

When used in conjunction with a fixed ankle foot orthosis it can cause a rapid plantar flexion and associated knee flexion due to the loss of ankle motion. This can be helpful or cause issues depending on the knee control of the patient. 

Elaine Owen states that she finds this to be a helpful adaption when tuning AFOs in her some of her published works

Negative heel flare/skive

This is the opposite of a posterior heel flare and influences the GRF at heel strike by moving it closer to the ankle joint axis, decreasing the lever arm acting on the joint.

This can be helpful in people with a foot slap as the decreased lever arm will reduce the requirement of the dorsiflexor muscles to ‘lower’ the forefoot to the ground.

In patients with a fixed ankle foot orthosis and poor knee control, the use of a negative heel flare can help decrease the effect of a fixed ankle AFO causing a knee flexion moment from heel strike to foot flat.

SACH heel

A SACH heel is when a softer material is added in a wedge at the back of the heel. Similar to the negative heel flare, it decreases the plantarflexion moment at heel strike and provides increased heel cushioning. 

Where the SACH heel is good is when a fully cushioned heel is not desirable. Especially in patients wearing fixed AFOs, if the heel is too soft, it can cause a delayed loading response.

Thomas, Oblique and full Heel

These adaptions are often confused with each other,  however, the aim is generally the same. To provide extra support under the side it is on. It can be used either medially or laterally.

Heel Wedge

Used similarly to wedging on functional foot orthoses and can be used either medially or laterally. The wedge's external nature allows an increased wedge thickness over what could be added to an insole. It will also allow a better fit of the sure and not potentially lift the heel away from any heel stiffeners.

Forefoot Wedge

Similar to the heel wedge, this adaption is added to the forefoot of the footwear.

These can be especially useful when used laterally for supination related issues due to the long lever arms it can provide.

Metatarsal Bar

Not a commonly used adaption, but it can be very effective in decreasing forefoot pressures. It has probably been replaced with rocker soles due to its more cosmetic appearance.

There are various options and positions that can be used depending on the clinical need.

Rocker Soles

This adaption is aimed to provide a smooth transition through the rockers of gait. They are also used to help in the unloading of pressure areas in diabetic footwear

Schaff and Cavanagh proposed the mechanism of unloading of rocker soles shoes as the following

  • Redistribution of load over a larger area
  • Increase in the loading time for the regions of the foot in contact with the rigid sole
  • A Change in the function of the foot due to the restriction of motion, in particular at the MTPjs
  • A reduction in shear pressure on the plantar surface.

Rocker apex is a commonly researched topic and it is generally it is felt that a rocker at 55-60% of the shoe length is best to offload the met heads. A rocker of 65% of shoe length to offload the hallux.

Heel retaining strap

Heel retaining strap to stop heel slip in shoes

Torque Heel

Torq heels are designed to provide a torque at heel strike to rotate the foot and hopefully the leg at heel strike. When use correctly they can promote internal or external rotation.

Raises

A commonly used adaption to equalise leg lengths due to a leg shortening