Dr.Almoutaz Alkhier Ahmed
Saudi Arabia/ Gurayat north
Diabetic Center
P.O.Box 672
Email : khier2@yahoo.com

INTRODUCTION

Diabetic foot lesions may face diabetic patients at any time in their diabetes life. It is estimated that approximately 15% of all people with diabetes will be affected by a foot ulcer during their lifetime⁽¹⁾.
Foot problems are very expensive, common and life threatening. In developed countries, up to 5% of people with diabetes have foot problems (1). They use between 12 - 15% of health care resources⁽¹⁾. In developing countries diabetic foot lesions may face up to 40%⁽¹⁾.

In a study done at King Khalid University hospital in Saudi Arabia the prevalence of diabetic foot lesions was 10.4% among the Saudi population⁽²⁾.

Another study done in Gurayat province showed the prevalence of diabetic foot ulcer was 5.5%⁽³⁾. In Taiwan the prevalence of diabetic foot ulcers was 2.9%⁽⁴⁾. This variation related to multiple factors such as availability of a national registry, and ethnicity or abundancy of other risk factors to develop diabetic foot ulcer (4).

Offloading devices are devices used to decrease the pressure over a wound and protect wounds, thereby giving the wound a good chance of healing.
Although many offloading modalities are currently utilized, only small numbers of case series exist describing the frequency and rate of wound healing associated with these devices.

In the following review I will describe the most commonly used modalities and the evidence that supports their employment.

Total Contact Casts (TCCs):
This is the most common modality for offloading used by diabetic foot specialists⁽⁵⁾. This type of offloading was first described by Milroy Paul in treating cases of neuropathic foot wounds and became more popular by Dr.Paul Brand at the Hansen's disease Center in Carville, Louisiana⁽⁶⁾.
This modality of offloading is known as total contact cast (TCC) due to the technique used to make it. It employs a well-moulded, minimally padded cast that maintains contact with the entire planter aspect of the foot and lower leg.

TCCs have been shown to reduce pressure at the site of ulceration by 84 - 92%⁽⁷⁾. It is also effective in treating a majority of non-infected, non-ischemic plantar diabetic foot wounds, with healing rates ranging from 72% - 100% over a course of 5 - 7% weeks⁽⁸⁾.

Total contact cast is beneficial because it reduces the pressure that occurs in the forefoot of the TCC through transmitting this pressure along the cast wall or to the rear foot^(9,10). It is very effective in treating ulcers in the forefoot and may not be appropriate for heel ulcers because it may apply extra pressure on the posterior foot (10).

The TCCs have other advantages than offloading as shown in Table 1.

Although, this modality had success in gaining the attraction of people working in diabetic foot care, it has some disadvantages which make its use by unskilled persons a dangerous practice. Table 2 show some disadvantages of the TCCs (11).

TCCs are contraindicated in certain conditions where its application could harm the wound (Table 3) (13).

In two randomized controlled trials comparing the proportion of healed ulcers treated with the TCC compared with other popular modalities (RCWs, half shoes and therapeutic depth inlay shoes), TCC healed a higher proportion of wound compared to other modalities⁽¹³⁾.

Removable cast walkers and the "instant" total contact cast:
The removable cast walker was designed to avoid the disadvantages of the TCCs. As their names implies; they are removable casts, easily removed. Table 4 shows the advantages of the removable walkers.

Interestingly, data suggests that the amount of pressure reduction for certain RCW is equivalent to TCCs⁽³⁾. Although data⁽⁷⁾ showed that some RCWs reduce the pressure as well as TCCs other⁽⁹⁾ data showed that healing with TCCs is more readily achieved than healing with other modalities.
The fact that stands behind this controversy is how the patient behaves towards the removable casts. Because patients can remove RCWs easily, the best feature of this device is potentially the most hazardous point.
In a recently conducted study, Armstrong et al⁽¹⁴⁾ evaluated the activity of patients with diabetic foot ulcers and their adherence to their offloading regime. This study suggests that it is less than 30% of their total daily activity.
Due to the disadvantages of the TCCs, Armstrong et al have suggested an alternative which might make the RCWs difficult to remove.
This alternative called instant total contact cast (iTCC)⁽¹⁵⁾. Wrapping the RCW with either a layer of cohesive bandage or plaster / fiberglass, making it more difficult for patients to remove.
The great advantage of iTCC is that it binds the benefit of offloading plus the benefit of forced compliance. Two recent randomized controlled trials support this advantage. In the first study, the iTCC appeared to heal as readily at 12 weeks as patients given a standard TCC (80% iTCC versus 74% TCC)⁽¹⁶⁾. The second study compared the iTCC with a standard RCW. This study suggest substantial differences in healing at 12 weeks between the irremovable and removable devices (83% versus 52%)⁽¹⁷⁾.

Scotchcast boot:
It was developed when fiberglass materials were introduced. Its development was to alternate with the plaster of Paris casts. The boot is made to fit each individual foot and a window cut at the site of ulceration
The Scotchcast boot has some advantages as Table 5 shows, suggesting its use⁽¹⁸⁾.

Scotchcast can be made removable or non removable by cutting away the cast over the dorsum of the foot and making a closure of padding and tape with Velcro straps. Windows are cut over the ulcers as needed. The foot is worn with a cast sandal to increase patient mobility while protecting the ulcer from any pressure.
View data are available to assess the efficacy of this modality, but preliminary data of healing rates ranging from 61 - 88% with mean healing time of 10 - 13 weeks have been reported⁽¹⁸⁾.

Half shoes:
This modality of offloading was designed to decrease the pressure on the forefoot postoperatively (19). It became popular for treating wounds in people with diabetes, due to some advantages (Table 6).

Chantelau in his paper⁽¹⁹⁾ compared this modality with routine wound care and crutch - assisted gait, suggested that more patients healed faster when using the half shoe and also develop less infections requiring hospitalization. As one of the removable modalities, this benefit could be one of its disadvantages and reduce its efficacy.

Healing sandals:
This is a specially designed sandal with a rigid rocker. This modality may theoretically limit dosrsiflexion of the metatarsophalengeal joints. It provides a greater distribution of metatarsal head pressures⁽²⁰⁾.
This modality has some advantages that support its use (Table 7).

Also, this modality has some disadvantages as shown in Table 8.

Recently, a hybrid between healing sandals and removable cast walkers has been introduced. This new device is known as the MABAL shoe. In a study by Hissink et al , this device showed a similar time to healing when compared with TCC⁽²¹⁾. Although this device looks excellent, it has some disadvantages like the healing sandal (Table 8).

Felted foot wear:
This is another modality for offloading⁽²²⁾. It is one of the commonly used offloading devices (18). It is done by fixing a bilateral felt - foam pad over the planter aspect of the foot with an aperture corresponding to the ulcer site.
Although this technique was used by some centers a debate has been raised on it, particularly on the pressure created around the edges of the aperture⁽¹⁹⁾ but some reports from othercenters advocate its use and showed it to be successful⁽²⁴⁾.

Crutches, walkers and wheelchairs:
These modalities can offer complete offloading of wounds but they needs upper body strength and endurance. One of the disadvantages of these devices is that they may place the contralateral limb at risk of ulceration by increasing pressure on the unaffected side⁽²⁵⁾.

Therapeutic footwear:
One of the common practices in diabetic foot clinics is the prescription of therapeutic shoes in an effort to assist in reducing pressure and facilitate wound healing, but is this an evidence based practice?
Unfortunately, the gait laboratory studies suggest that therapeutic shoes allow up to 900% more pressure in areas of the forefoot compared to TCCs and some RCWs.
Theymay help in facilitating healing of superficial ulcers and not offloading an active ulceration (26).

The key to successful pressure reduction lies more in patient adherence than in prescribed offloading devices. Combining an effective, easy to use offloading device that ensures patient compliance will carry high success rate on reducing the pressure and healing rate.

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