INTRODUCTION
The successful management of venous leg ulcers represents a significant clinical problem and a major drain on limited financial resources. Research has shown that majority of the ulcers can be induced to heal by the application of adequate levels of sustained graduated compression, although this technique is contraindicated for the treatment of ischaemic ulcers.

Bandages vary greatly in their ability to provide sustained compression due to differences in their structure and the content of elastomeric yarns. Other factors such as limb circumference and shape will also have an important influence on the pressure produced beneath the compression bandage.

EPIDEMIOLOGY
Leg ulcers are a chronic condition and these incur a significant financial implication on the patients. These ulcers can be caused by number of physiological or biochemical disorders either individually in combination, but the majority, approximately 70% are associated with venous disease.

The prevalence of active venous ulcers in the United Kingdom is around 1.5/10,000 of the adult population, although the number of people who develop at least one episode of ulceration may be 3-4 times greater than this. The prevalence of venous ulcerations increases with age and is more common in women than in men.

HISTORY

Bandages have a history stretching back thousand of years to the time of the ancient Egyptians, who used simple woven fabrics, often coated with adhesives, resins, and other medicaments as dressing for a wound healing. Like some of the bandages used today, these were made from non-extensible fabric and probably required considerable skill on the part of the user to ensure correct application.

In the 17th century, Pierre Dionis who was surgeon-in-ordinary to the queen of France and to the Empress Maria Theresa of Austria recommended the use of rigid lace-up stockings made from coarse linen or dog skin to apply compression in the treatment of leg ulcers. The bandages available at that time were not suitable for the application of sustained, controlled compression because of their inelastic nature. It was not until the middle of 19th century that the first elasticated bandages containing natural rubber were manufactured. In 1878, Calendar published a letter in the Lancet, which described the use of these materials in the management of varicose veins.

ANATOMY AND PHYSIOLOGY OF VENOUS SYSTEM OF THE LEG

The veins of the leg are divided into superficial and deep systems. The deep veins, which come together to form the popliteal and femoral veins lie within the fascia and are responsible for the venous return from the leg muscle. Also within the fascia, the soleus and gastrocnemius muscles have dilated valveless sinusoids, which fill with blood when the leg is at rest. Together these deep vascular structures, have a combined volume of about 100 to140 ml comparable to that of one of the ventricles of the heart.

The long saphenous vein which runs along the medial side of the vein from foot to groin and the short saphenous vein which runs at the back of the calf, from foot to knee are the major vessels of the superficial venous system. These vessels lie outside the fascia and are responsible for the venous return from the skin and subcutaneous fat.

The two systems are joined by communicating veins, sometimes called perforators as they perforate the deep fascia. The perforators, like the other veins in the leg, contain valves that permit the flow of blood in one direction only, from the outer or superficial system inwards to the deep veins. The venous pressure at the ankle of the subject who is lying supine is around 10 mm Hg, but on standing this will rise by about 80 mm Hg, due to an increase in hydrostatic pressure.

During walking, as the foot is dorsiflexed, the contraction of the calf muscle compresses the deep veins and soleal sinuses to the point at which they become almost totally collapsed, producing pressures of upto 250 mm Hg and emptying them of blood. As the foot is plantar flexed, the pressure in the veins falls, the proximal valves close, and the veins are refilled by blood passing through the perforators from the superficial system. During this cycle, in a normal leg, the distal valves of the deep veins and the valves of the perforators will ensure that the expelled blood can go only in one direction i.e. upwards, back to the heart.

The pumping action of the calf muscle causes the hydrostatic venous pressure in the ankle region to gradually fall until it reaches a steady state, usually about 30 mm Hg in the deep veins and 40 mm Hg in the superficial veins. If the subject then stands still, the pressure in both systems will slowly return to a stable value of about 90 mm Hg, a process that usually takes about 20-30 seconds.

THE EFFECT OF DAMAGE TO THE VENOUS SYSTEM

Blockage or damage to venous system will cause disruption to normal blood flow, which may manifest itself in a number of different ways according to the site and extent of the damage. If the valves in the superficial system are affected, venous return will be impaired and blood may accumulate in the veins causing them to become distended leading to the formation of varicosities (varicose veins).

If the function of the perforator valves is impaired the action of the calf muscle pump will tend to cause blood to flow in the reverse direction into the superficial system increasing the possibility of damage to the superficial vessels.

Following deep vein thrombosis that results in complete or partial obstruction of a deep vein, the unrelieved pressure produced by the calf muscle pump on the perforator valves may cause these to become incompetent. If this occurs, there will be a large rise in the pressure in the superficial system which may force proteins and red cells out of the capillaries and into the surrounding tissue, Here, the red cells break down releasing red pigments which causes staining of the skin called lipodermatosclerosis, an early indicator of ulcer formation.

DIAGNOSIS OF VENOUS ULCERATION

Ulcer characteristics - Its location is most often around the medial malleolus (gaiter area). The ulcer base is usually pink with healthy granulation tissue with an irregular border. There is usually a copious exudate from the ulcer. Pain is usually not present but may occur if the superficial nerves are exposed. The surrounding skin is pigmented with lipodermatosclerotic changes. The limb is usually swollen thereby making peripheral pulses difficult to palpate.

Investigation-

1. Hand held Doppler
2. Colour Doppler scan
3. Ankle-brachial index
4. Venous plethysmography
5. Venogram?

Treatment -

1. Compression Bandaging
2. Corrective Venous Surgery
3. Maintenance treatment

EXTERNAL COMPRESSION

For patients with venous disease, the application of graduated external compression can help to minimise or reverse the skin and vascular changes described previously, by forcing fluid from the interstitial spaces back into the vascular and lymphatic compartments. As the pressure within the veins of a standing subject is largely hydrostatic, it follows that the level of external pressure which is necessary to counteract this effect will reduce progressively up the leg, as the hydrostatic head is effectively reduced. For this reason it is usual to ensure that external compression is applied in a graduated fashion, with the highest pressure at the ankle.

FACTORS WHICH DETERMINE SUB-BANDAGE PRESSURE

The pressure developed beneath any bandage is governed by the tension in the fabric, the radius of curvature of the limb and the number of layers applied. Applying a bandage with a 50% overlap produces 2 layers of fabric which generates a pressure twice that produced by a single layer. Sub bandage pressure can be calculated using a simple formula derived from the Laplace equation as follows:

P = (TN x 4630)/CW where)

P = Pressure in mm Hg

T = Bandage tension in kgf

C = Circumference of the limb in cms.

W = Bandage width in cms

N = No. of layers applied

Sub-bandage pressure is therefore directly proportional to bandage tension but inversely proportion to the radius of curvature of the limb to which it is applied. This means, therefore, that a bandage applied with constant tension to a limb of normal proportions will automatically produce graduated compression with the highest pressure at the ankle. This pressure will gradually up the leg as the circumference increases.

Effects of compression

Graduated compression has shown to
1.Increase blood velocity in the deep veins
2.Reduce oedema and therefore reduce the pressure differential between the capillaries and the tissues.
3.Reduce distension of superficial veins and reverse venous hypertension
4.Improve the healing rate of chronic venous ulcers.

Sarin. S. in his recent research has indicated that external compression restores valve function in a proportion of superficial and deep veins by decreasing vein diameter and therefore improving overall venous function. The full physiological effect of compression is still not fully understood and required further research.

Stemmer demonstrated theoretically that 40 mm Hg pressure at the ankle was required to reverse chronic venous hypertension. The 4 layer bandage system was developed to apply 40 mm Hg pressure at the ankle graduated to 17 mm Hg pressure at the knee using bandages of different properties.

DRESSING
It is claimed that dressings influence ulcer healing. Following extensive randomised control studies, involving different dressing types usedconjunction with the 4 layer bandage, it was found that dressings had little influence on ulcer healing. Therefore, in the majority of ulcers a simple non-adherent dressing is used. Viz. Sofratule, Adaptic, lnadine, etc. It is very important to choose a dressing that will not aggravate the patient’s ulcer or surrounding skin.

BANDAGES
All bandages used are 10 cms in width and should be applied from the base of the toes to the knee joint.
Layer 1 - Orthopaedic wool such as Velband or Softban. This is used to absorb exudate and redistribute pressure around the ankle, protecting the bony prominences from excessive pressure. It also fills in the troughs behind the malleoli where little pressure is exerted. The bandage is applied without tension in a loose spiral.

Layer 2 - Cotton crepe bandage. This is arguably the least effective layer in the combination. Its function is to increase absorbency and to smooth the orthopaedic wool layer, thereby preserving the elastic energy of the main compression layers. The cotton crepe bandage is also applied in a spiral.

Layer 3 - Elasticated crepe bandage. This is a highly elastic, conformable compression bandage. It is applied at mid stretch in a figure of 8 with a 50% overlap. This weaves a mean pressure of 17 mm Hg on ankles measuring 18-25 cms.

Layer 4 - Coban. This is a light weight, elastic, cohesive bandage. When applied at mid stretch with 50% overlap to an ankle measuring 15-25 mm, it gives an ankle pressure of 23 mm Hg. Coban maintains the 4 layers in place until removal and adds durability to the system.

The combined pressure of these bandages is 40 mm Hg at the ankle graduated to 17 mm Hg pressure at the knee. This system has been further developed to accommodate differing limb circumferences. As the limb circumferences is variable, and may decrease considerably in the first few weeks, owing to a reduction of oedema following application of compression, the measurement of ankle should be repeated at frequent intervals.

Each limb must be assessed carefully and individually before applying compression and the bandager must be aware of potential problems that each limb may present, In particular, very thin legs need extra padding to prevent excessive pressure over the bony prominences and the tendinous area over the dorsum of the foot, which may cause pressure necrosis. This extra padding can be achieved in a variety of ways, e.g., by pleating the orthopaedic wool layers, thus protecting the tibial crest.

Conversely, a large or oedematous limb will need a stronger elastic bandage to achieve adequate compression. In ankles measuring more than 25 cms, a stronger elasticated crepe bandage is used in place of dynaflex to achieve 40 mm Hg pressure.

Ulcer lying behind the malleoli may not receive adequate compression. A pressure pad is placed over the primary dressing to apply direct pressure to the ulcer bed. Many chronic leg ulcer patients who have been bandaged for long periods of time are immobile and loose a proportion of their calf muscle bulk. Effective graduated compression relies on the natural gradient of the leg, which is decreased in these patients. This is simply rectified by padding the calf area and thus redefining the shape of the leg.

HAZARDS OF COMPRESSION BANDAGING
* Arterial disease is a contra indication. Patient with an ABI of less than 0.8 should not receive full compression. Application of compression to a limb with poor circulation may lead to pressure necrosis and may even necessitate amputation.

* Compression can cause pressure necrosis in absence of arterial disease in patients with narrow ankles and thin calves. Excessive pressure may beapplied over bony prominences and the malleoli.

* Compression should be used with caution for patient with rheumatoid arthritis or diabetes mellitus, as these patients are susceptible to microvessel disease. Application of compression can cause further occlusion of these vessels and result in pressure necrosis.

* Patients with oedema secondary to heart failure should not receive compressions to reduce oedema as this may produce a sudden increase in venous return, which may further exacerbate the heart failure.

VENOUS SURGERY
Following healing of venous ulcer, the underlying cause should be corrected surgically if possible viz; varicose veins surgery, subfascial endoscopic perforator ligation, deep venous valve repair.

MAINTENANCE TREATMENT
This is the most important treatment modality that prevents recurrence of ulceration. A class II compression stockings should be worn life long.

CONCLUSION
Sustained compression of over 40 mm Hg achieved with a 4 layer bandage results in rapid healing of chronic venous ulcers that have failed to heal in many months of compression at lower pressures with more conventional bandages.

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