Why Some Wounds Take Long to Heal

Wound occurs from an injury to the tissue.  The extent of the wound depends largely on the severity of the injury and the body’s local or systemic response to the injurious agent. Every individual is most likely to encounter one form of wound or the other as they engage in their day to day activities. The causes of tissue injuries vary and they include

  • Mechanical agents : cause most wounds sustained at work, home, road, or as a result of assault.
  • Chemical agents : usually strong acids, alkali or other caustic and corrosive chemicals which accidentally or by intentional assault, come in contact with the tissues. Wounds from snake or insect bite belong to this group.
  • Radiant energy : radiations like X-ray, high voltage electricity, heat and intense cold can produce extensive wounds.
  • Pathogenic microbes : Pathogenic organisms themselves seldom cause wounds because of the body’s natural ability to resist them. More often, they are secondary invaders of wounds produced by other primary agents. They are able to cause extensive damage through the Chemical substance they produce (exotoxins) and through hypersensitivity reactions of the local tissues to the organisms.

 

What are the types of wounds? 

Wounds are generally classified as either closed or open.

 

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A contusion or bruise on the right thigh

 

Closed wounds are also called contusions or bruise, and results from injury of the tissues subjacent to the surface epithelia  (subcutaneous or submucosal tissues) and usually due to blunt trauma. There is disruption of connective tissue with extravasation of blood which causes bruising or ecchymosis (spread of redness under skin) or petechia (droplets of haemorrhaging under skin). The epithelium remains intact and protects the damaged tissues from microbial assault. If this is successful then healing, though often slow, can be expected.

Open wounds may be a mere loss of superficial layers of the epithelium, in which case it is referred to as abrasion. Open wounds may be much deeper and penetrate the full thickness of the skin. When this happens and the wound entry is small, from a pointed agent like nail or knife, it is called a puncture wound. If the wound entry is relatively wider, it is called a laceration. If the wound enters the body cavities such as chest or abdomen, it is called a penetrating wound and if the wound entry passes through an organ or cavity as seen in firearms missile injuries, it is referred to as a perforating wound.

 

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Occasionally, portions of the body parts may be torn or wrenched away. When this occurs, it is called  an avulsion wound. A complete avulsion is where there is no more connection between the detached part and it’s original site (amputation). Partial avulsion is when strands of tissues still connect the injured part with its original site. Surgical or incisional wounds are also regarded as open wounds.

Secondary bacteria infection is the problem of all open wounds which makes healing difficult. With the exception of surgical wounds, all opened wounds must be regarded as contaminated.

 

Factors that delay wound healing 

 

General factors are

  1. Age : wound healing delays in old people as compared to young people. This is due to deficient blood supply as a result of atherosclerosis which is more predominant in the elderly.
  2. Severe constitutional diseases : Patients with diabetes, chronic nephritis, congestive heart failure, and  chronic liver disease heal less rapidly. Cancer patients in general have a very poor wound healing.
  3. Nutrition : Nutritional factors that affect wound healing include vitamin c deficiency, protein deficiency, and deficient  trace elements like zinc delay wound healing.
  4. Drugs : cytotoxic (cancer) drugs and radiation therapy delay wound healing. It is advisable to allow patient’s wound to heal first before commencing treatment.

 

The local factors that affect normal wound healing include

  1. Oxygen supply : Oxygen is the most important wound nutrient. If it’s delivery to the wound site is impaired, healing can be delayed. Tissue trauma and tight suturing techniques can hinder oxygen supply to the wound site.
  2. General blood supply : wounds in vascular areas heal very quickly but even small wounds in the ischemic legs of atherosclerotic patients heal very slowly. A wound on the face will heal very fast because of the rich blood supply to the face.
  3. Infection : Invasion of the healing wound by pathogenic bacteria will invariably delay the healing process. Infections impair blood flow and raises local need for oxygen. In very severe infections especially with anaerobes, tissue destruction may be great and healing delayed for weeks or months.
  4. Mobilisation and trauma : Inadequate immobilisation such as persistent coughing after abdominal surgery may lead to separation of wound edges with subsequent infection. Repeated movement and trauma to wound site has the effect of disrupting the newly generated capillaries and collagen laid down.
  5. Foreign bodies : Any kind of foreign material retained in the wound will delay healing and bring about infection in addition. The wound may remain unhealed until that foreign body is removed. Dead body tissues such as bone, teeth, nail, hair etc can behave as foreign materials if present in a wound.
  6. Surgical technique : with surgical wounds, wound healing delays if wound edges are not correctly apposed together. Rough handling of tissues and excessive trauma also delay healing too. Excessive tension from suturing can also delay wound healing.

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