How a PRAFO defeats heel pressure ulcers

Pressure ulcers remain a serious problem. A plethora of medical and “mechanical” risk factors combine, leading to more than 400,000 pressure ulcers in the UK each year. We have recognised for years that conditions such as diabetes can lead to a greater risk of pressure sores. Globally diabetic foot disease leads to an amputation every 30 seconds due this combination of medical and mechanical risk factors.

Areas of the body where there are bony prominences such as the heels are particularly vulnerable to pressure ulcers. Persons that are at medical risk and immobile are also subject to the laws of mechanics and this is why their is so much discussion over pressure and shear forces. In this article we can see why a PRAFO manages to prevent or treat heel pressure ulcers.

At an area such as the unprotected heel, we are likely to have a small area of the contact surface over which the weight of the limb must be applied. Although these effects may seem quite small, they can be sufficient in a medically compromised person to stop blood flow in the area and if this continues it causes the cells of the tissues to die - leading to an ulcer.

In our simplistic model here we can imagine we are looking at the heel area with bone surrounded by an amount of tissue (yellow).

When this area is loaded because of contact with a support surface there are both surface and deeper tissue effects. Although we cant “see” what is happening in the deeper tissues it is really here that the damage is really done.

Although we refer to “pressure ulcers” and this seems to imply the role of surface pressure, the reality is much more complex than that. Certainly pressure applied “normal” (at right angles) to the surface can occlude the small blood vessels but shear effects that arise through distortion fo the tissue are much more effective at stopping blood flow. Directly under the bony prominence the pressure in the tissue is highest and the pressure drops as you move away from that area. However, if we could measure the shear effects in the tissue these tend to increase as you move away from the loaded area as the tissues are stretched and deflected.

How do we protect the heel from mechanical effects? The best way is to ensure that the heel has no possibility of being affected by pressure or shear - and that means NO CONTACT between the heel tissues and the support surface.

The reason the PRAFO range of ankle foot orthoses are so effective is they suspend the heel and don’t allow any contact between the vulnerable area of tissue and a support surface. The heel area is suspended and the loads are distributed over a much larger contact area of the calf and foot so they cannot cause ulcers.

Some of the rival designs to the PRAFO use plastic structures to suspend the heel. However, the laws of mechanics cant be denied and there is a risk of the plastic devices flexing and distorting. This may even result in the heel area remaining protected but elevated loads elsewhere such as the sole of the foot or toes.

We could say that it’s not what you “put on” an at risk foot that provides protection - it’s what you take off - specifically pressure and shear. The PRAFO designs are effective means of doing just that.

Learn more about the PRAFO on this site and contact us for purchase enquiries or the details of your closest orthotic supplier.