Anatomical Concepts (UK)
Masters of Rehabilitation Engineering


Opinions, Ideas & News from Anatomical Concepts (UK) Ltd

Preventing heel ulceration with a PRAFO ankle foot orthosis

Back In 1995 I was a Visiting Professor to the Cleveland Clinic and the USA and saw what I thought was a great product - the one and only Pressure Relief Ankle Foot Orthosis (PRAFO). We basically created our business from the first generation of this product which offered zero pressure and shear force at the “at risk” heels of both ambulant and recumbent patients.

the “original” 650SKG PRAFO with Kodel liner

the “original” 650SKG PRAFO with Kodel liner

At this time heel ulcers or so-called pressure sores and diabetic foot ulcers were a huge problem for the NHS. Actually they are still a massive problem for the NHS!

Extremely severe heel ulcer

Extremely severe heel ulcer

A pressure ulcer is an area of damage to the skin and underlying deeper tissues that is caused by un-relieved pressure, friction and/or shear forces. We have known for decades the areas at risk and the medical factors that lead to risk but we havent eliminated the problem.

A major key to prevention is to relieve or ideally eliminate pressure and shear effects. The biomechanics of tissue are complex and this means that it is easier to aim to eliminate pressure and shear rather than use a method which assumes that a particular level of pressure is “safe”.

The reason the PRAFO is so effective is that it cradles and positions the foot and ankle so that there is no possibility of pressure or shear force at the heel.

The ulcer above - almost healed. This would not be possible without pressure relief

The ulcer above - almost healed. This would not be possible without pressure relief

Zero pressure and shear force on the tissues at risk is absolutely essential for prevention or wound healing. There is a very true saying that it is not what you put on an ulcer that heals it or prevents it (lotions and potions) it is what you take off (the pressure, shear and other mechanical effects).

A severe ulcer is susceptible to infection and may be life-threatening. Estimates suggest that one in five hospital inpatients has a pressure ulcer and this means that at least 20,000 hospital patients are affected at any one time. As many more individuals are cared for at home or in residential/nursing homes we suspect that the incidence in these locations is higher still. In the UK we expect pressure ulcers to produce economic costs in billions each year.

The risk factors for pressure ulcers are well known and have been for decades. They include:

  • Reduced mobility or immobility— pain in nomral circumstances can be a warning signal that pressure has been exerted for too long. Pain normally triggers movement so that pressure is relieved. Patients who are unable to move for whatever reason will require the help of someone else in order to do so or will require a method of preventing pressure on areas at risk. Areas at risk are typically bony prominences such as the calcaneal area of the heal, the sacrum, elbows etc

  • Lack of sensation—if pain signals are absent, patients may not be aware that damage is occurring and will not realise that they should move. This includes anything which may impair sensation including unconsciousness, analgesia, neuropathy or alcohol/substance abuse.

  • Nutritional status— undernourished or nutritionally compromised people are at increased risk of pressure ulcer development.

  • Compromised vascular supply—skin with compromised vascular supply is at risk. Patients with peripheral arterial disease, or patients who experience events such as cardiac arrest may be at increased risk. We have long known that various combinations of pressure and duration of exposure to pressure (time of pressure application) can be damaging. Individuals with compromised circulation will only tolerate relatively low pressure levels and for shorter periods of time compared with “normals”

  • Moisture—skin that is constantly or often moist is at increased risk of pressure ulcer.

  • Friction and shear— There is no such thing as a universally safe level of pressure. We should try to eliminate pressure on areas of risk as far as possible. The fact is, objects that contact tissue and generate pressure at the tissue surface also tend to do something else - they often generate shear forces within the tissue and subject the tissues to friction. We find that clinicians generally have a poor understanding of pressure, friction and shear. Contact between an object and tissue that tends to deflect and distort the surface tissues causes deeper effects that can be very damaging. These effects are very efficient at further hampering blood flow by stretching and contorting small blood vessels - this is the consequence of shear force. This is most commonly seen in the sacrum and heels.

the 653PKG - Dual Action PRAFO with Pad and Strap kit option

In addition to the risk factors described above, a variety of conditions may also increase the risk of developing a pressure ulcer:

diabetes, dementia, significant cognitive impairment, tremors, leg spasms, leg oedema, critical illness, low or high body mass index (BMI), terminal illness, extremes of age, previous history of pressure damage and long theatre times.

Various clinical risk assessment tools exist and are recommended by NICE to be used alongside clinical judgement to determine whether a person is at increased risk.

The original PRAFO ankle foot orthosis (650SKG) offered a simple to use orthosis that could be used with at risk patients for prevention of heel ulceration. The design incorporates a variety of replaceable liners and an intrinsic walking base so that the patient could be mobilised and remain protected.

A very important feature of the PRAFO design that positions it differently from competitor products is the incorporation of a metal upright. The 650SKG, the 652SKG and the 653SKG all utilise a metal upright which resists undue flexion of the structure which could give rise to unwanted pressure on the patient’s tissues.

We have seen, for example, stroke patients fitted with inexpensive plastic and foam designs generating high plantarflexion forces which are sufficient to distort the orthosis and generate metatarsal ulceration. The stiffness of the PRAFO designs in the same situation would prevent this distortion and of course help the patient achieve protected ambulation when indicated. The PRAFO has evolved from its origins in the 1990’s to offer a great range of products for the widest range of applications.