Wound


A wound is any disruption of or damage to living tissue, such as skin, mucous membranes, or organs. Wounds can either be the sudden result of direct trauma, or can develop slowly over time due to underlying disease processes such as diabetes mellitus, venous/arterial insufficiency, or immunologic disease. Wounds can vary greatly in their appearance depending on wound location, injury mechanism, depth of injury, timing of onset, and wound sterility, among other factors. Treatment strategies for wounds will vary based on the classification of the wound, therefore it is essential that wounds be thoroughly evaluated by a healthcare professional for proper management. In normal physiology, all wounds will undergo a series of steps collectively known as the wound healing process, which include hemostasis, inflammation, proliferation, and tissue remodeling. Age, tissue oxygenation, stress, underlying medical conditions, and certain medications are just a few of the many factors known to affect the rate of wound healing.

Classification

Wounds can be broadly classified as either acute or chronic based on time from initial injury and progression through normal stages of wound healing. Both wound types can further be categorized by cause of injury, wound severity/depth, and sterility of the wound bed. Several classification systems have been developed to describe wounds and guide their management. Some notable classification systems include the CDC's Surgical Wound Classification, the International Red Cross Wound Classification, the Tscherne classification, the Gustilo-Anderson classification of open fractures, and the AO soft tissue grading system.

Acute wounds

An acute wound is any wound which results from direct trauma and progresses through the four stages of wound healing along an expected timeline. The first stage, hemostasis, lasts from minutes to hours after initial injury. This stage is followed by the inflammatory phase which typically lasts 1 to 3 days. Proliferation is the third stage of wound healing and lasts from a few days up to a month. The fourth and final phase of wound healing, remodeling/scar formation, typically lasts 12 months but can continue as long as 2 years after the initial injury. Acute wounds can further be classified as either open or closed. An open wound is any injury whereby the integrity of the skin has been disrupted and the underlying tissue is exposed. A closed wound, on the other hand, is any injury in which underlying tissue has been damaged but the overlying skin is still intact.

Open wounds

  • Incisions or incised wounds – caused by a clean, sharp-edged object such as a knife, razor, or glass splinter.
  • – irregular tear-like wounds caused by some blunt trauma. Lacerations and incisions may appear linear or stellate. The term laceration is commonly misused in reference to incisions.
  • Abrasions – superficial wounds in which the topmost layer of the skin is scraped off. Abrasions are often caused by a sliding fall onto a rough surface such as asphalt, tree bark or concrete.
  • Avulsions – injuries in which a body structure is forcibly detached from its normal point of insertion; a type of amputation where the extremity is pulled off rather than cut off. When used in reference to skin avulsions, the term 'degloving' is also sometimes used as a synonym.
  • Puncture wounds – caused by an object puncturing the skin, such as a splinter, nail, knife or sharp tooth.
  • Penetration wounds – caused by an object such as a knife entering and coming out from the skin.
  • Gunshot wounds – caused by a bullet or similar projectile driving into or through the body. There may be two wounds, one at the site of entry and one at the site of exit, generally referred to as a "through-and-through."
  • Critical wounds – Including large burns that have been split. These wounds can cause serious hydroelectrolytic and metabolic alterations including fluid loss, electrolyte imbalances, and increased catabolism.

    Closed wounds

  • Hematomas – caused by damage to a blood vessel that in turn causes blood to collect under the skin.
  • * Hematomas that originate from internal blood vessel pathology are petechiae, purpura, and ecchymosis. The different classifications are based on size.
  • * Hematomas that originate from an external source of trauma are contusions, also commonly called bruises.
  • Crush injury – caused by a great or extreme amount of force applied over a long period of time.

    Fractures

can be classified as either open or closed, depending on whether the integrity of the overlying skin has been disrupted or preserved, respectively. Several classification systems have been developed to further characterize soft tissue injuries in the setting of an underlying fracture:
  • Tscherne classification – Used to describe external appearance of wounds in both open and closed fractures.
  • Gustilo-Anderson classification – Classifies open fractures based on wound size, extent of soft tissue loss, and degree of contamination.
  • Hannover Fracture scale – Used in open fractures as an extremity salvage assessment.
  • AO Classification – adapted from the Tscherne classification, provides separate grading system for skin, muscles/tendons, and neurovascular structures.

    Chronic wounds

Any wound which is arrested or delayed during any of the normal stages of wound healing is considered to be a chronic wound. Most commonly, these are wounds which develop due to an underlying disease process such as diabetes mellitus or arterial/venous insufficiency. However, it is important to note that any acute wound has the potential to become a chronic wound if any of the normal stages of wound healing are interrupted. Chronic wounds are most commonly a result of disruption of the inflammatory phase of wound healing, however errors in any phase can result in a chronic wound. The exact duration of time which distinguishes a chronic wound from an acute wound is not clearly defined, although many clinicians agree that wounds which have not progressed for over three months are considered chronic wounds.

Common causes of chronic wounds

  • Diabetes mellitus – Wound healing impairment in the setting of diabetes is multifactorial. Hyperglycemia, neuropathy, microvascular complications, impaired immune and inflammatory responses, and psychological factors have all been implicated in the formation and propagation of diabetic wounds. Feet are the most common location of diabetic wounds, although any type of wound can be negatively impacted by diabetes. It has been estimated that up to 25% of patients with diabetes mellitus will be affected by non-healing wounds in their lifetime.
  • Venous/Arterial insufficiency – Impaired blood outflow or inflow can both impair wound healing, thereby causing chronic wounds. Much like diabetes, venous/arterial insufficiency most commonly result in chronic wounds of the lower extremities. In chronic venous insufficiency, blood pooling impedes oxygen exchange and creates a chronic pro-inflammatory environment which both promote formation of venous ulcers. Peripheral artery disease, on the other hand, causes wounds due to poor blood inflow and typically affects the most distal extremities.
  • Immunologic disease – The immune system plays a critical role in the inflammatory process; therefore, any disease of the immune system has the potential to impair the inflammatory phase of wound healing, thereby leading to a chronic wound. Patients suffering from diseases such as rheumatoid arthritis and lupus have been found to have larger wounds and prolonged time to heal when compared to the general population.
  • Pressure ulcer – Also known as decubitus ulcers or bedsores, this type of wound is a result of chronic pressure to the skin over a prolonged period. While most individuals have intact sensation and motor function which allow for frequent positional change to prevent the formation of such ulcers, older individuals are particularly susceptible to this type of chronic injury due to impaired neurosensory responses. Pressure ulcers can occur in as little as two hours of immobility in a bedridden patient or person who is otherwise unconscious/sedated. In the United States, pressure ulcers are graded using the National Pressure Injury Advisory Panel system. In this system, ulcers are graded on wound depth with stage 1 being the least severe and stage 4 being full thickness damage through subcutaneous tissue down to muscle, tendon, or bone. Any ulcer that cannot be assessed due to overlying eschar is considered unstageable.

    Wound sterility

Wound sterility, or degree of contamination of a wound, is a critical consideration when evaluating a wound. In the United States, the CDC's Surgical Wound Classification System is most commonly used for classification of a wound's sterility, specifically within a surgical setting. According to this classification system, four different classes of wound exist, each with their own postoperative risk of surgical site infection:
  • Class 1 – clean wound: a wound that is not infected and without signs of inflammation. This type of wound is typically closed. By definition, this type of wound excludes any wounds of the respiratory, genital, alimentary, or urinary tract.
  • Class 2 – clean-contaminated wound: a wound with a low level of contamination. May involve entry into the respiratory, genital, alimentary, or urinary tract.
  • Class 3 – contaminated wound: an open, accidental wound resulting from trauma outside of a sterile setting is automatically considered a contaminated wound. Additionally, any surgical wound where there is a major break in sterile technique or obvious contamination from the gastrointestinal tract is considered a contaminated wound.
  • Class 4 – dirty/infected: a wound with evidence of an existing clinical infection. Class 4 wounds are usually found in old traumatic wounds which were not adequately treated and will show evidence of devitalized tissue or gross purulence.