WOUNDS NONHEALING

CAUSES
Chronic or nonhealing wounds are open wounds that fail to epithelialize and close up in a reasonable amount of time. These wounds present as clinically unhealed ulcers without evidence of further healing. These wounds can be broadly classified as: Pressure sores, lower extremity ulcers, and radiation skin injury.

Pressure sores
Pressure sores develop over a subcutaneous point, usually in a bed ridden patient. These are frequently called “decubitus ulcers” or “bed sores”. The sacrum ischium, and greater trochanter are the most common location affected.

Pressure necrosis results from the amount or pressure on the tissue trapped between the bone and the bed and duration of continuous pressure. Microcirculation is when the tissue pressure is greater than 25 30 mmHg. this blocks capillary perfusion pressure. Necrosis can occur with as little as 2 hours of sustained pressure at this level.

Skin is more resistant to pressure necrosis than the underlying fat and muscle, which explains the common finding of a small area of skin ulceration overlying a large are of subcutaneous fat and muscle necrosis.

To begin treatment of these patients, efforts should be made to control the factors leading to increased pressure.

Paralyzed patients require periodic rotation and air mattress or other type of low pressure beds.

In other cases behavior and contractures may need to be addressed.

Tight fitting casrs should be removed and replaced by those with no excess pressure.

Other contributing factors should be identified and controlled, such as malnutrition infection and diabetes control. Necrotic tissue requires debridement.

With avoidance of pressure over the involved area, most pressure sores heal. However they beal with scar formation which is less resistant to trauma than intract skin. Thus a higher incidence or recurrence exists atter spontaneous closure of these wounds than if they are closed surgically with flaps of normal skin and muscle over the bony prominence.

Lower extremity ulcer
Leg ulcer generally arise either different vascular diseases. Arterial or venous insufficiency. Most (80% - 90%) result form venous valvular disese (venous in sufficiency)

Increased venous pressure in the dependent lower extremity lead to localize edema and tissue necrosis. Tissue edema is though to be a manor inhibitor of repair at the ulcer site, but the exact mechanism is not known. Oxygen delivery and diffusion are likely impaired. Postcapillary obstruction leads to an increased perfusion pressure and hypoxia. Protein and red blood cell extravasation occurs which further limits diffusion and oxygen delivery.

Arterial insufficiency to the lower extremity greatly impairs healing. Minor trauma resulting form scratches and abrasion that would otherwise heal quickly in a normal patient, can progress into large wounds and ultimately narcotizing, infection can cause death. Clinical sign of adequate arterial inflow is the simple presence of an pulse if a single is present in the foot then most wounds will heal.

A non healing wound in a ischaemic extremity is generally regarded as an indication for revascluration of the extremity.

External beam radiation through skin to treat deep pathology has both acute and chronic effects on skin. Acutely, a self limiting erythema may develop that spontaneously resolves.
Its late effects can be a more significant injury to fibroblasts, keratinocytes, and endothelial cells. DNA damage to these cells propagates over time and impairs the ability of these cells to divide successfully. Ultimately, a skin ulcer may occur spontaneously, but usually it occurs after repeated mild trauma such as abrasions.

If a surgical incision needs to be placed through an area of irradiated skin, then that incision is not likely to heal. Currently the only treatment modalities for these wounds are hyperbar oxygen therapy or coverage with vascularized tissue flaps
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