Soft Tissue Injuries and Burns

Stages of Wound Healing

Injured tissue goes through four stages on its path to healing: haemostasis , inflammation , proliferation and remodelling . There is some overlap between stages and healing may be impaired or interrupted, resulting in a poorer outcome. Several cytokines coordinate wound healing.

Haemostasis involves coagulation and vasoconstriction. Inflammation begins over the 4 days following injury. Early inflammation involves complement activation and neutrophil ingress by diapedesis. Later, macrophages become the predominant cell type. These perform phagocytosis and release cytokines and growth factors. Proliferation occurs from about day 4 to week 4. Epithelial-only injuries with an intact basement membrane restore continuity over days. Deeper injuries involve migration and proliferation of epithelial cells from the wound edge under the control of transforming growth factor (TGF-α) and epidermal growth factor (EGF). Disorganised connective tissue is initially formed in the cavity by fibroblasts migrating and proliferating in the granulation tissue, directed by platelet-derived growth factor, EGF and TGF-β. Angiogenesis occurs within this new tissue under the control of tumour necrosis factor (TNF)-α. Remodelling occurs over several months. The initial disorganised collagen is reorganised along lines of stress, leading to wound maturation. There is also a change from type III to type I collagen, and myofibroblasts in the wound contract its extent. The wound does not fully return to normal organisation but instead forms a scar. The wound is weak for the first 2 to 3 weeks; at around 8 months the wound reaches around 80% of its original strength.

The management of a soft tissue injury depends upon the following factors:

• the mechanism of injury (e.g., penetrating knife wounds, lacerations in road crashes, blast injuries, gunshot and missile injuries, burns, bites);

• the site of injury;

• the extent and depth of wounds;

• the types of tissue involved including nerves and blood vessels;

• the extent of tissue devitalisation;

• any contamination (e.g., with road dirt, soil or potential bacterial inoculation with animal or human bites);

• the possibility of retained foreign bodies.

Minor Soft Tissue Injuries

Most minor wounds can be cleaned and sutured immediately or closed with tissue glue. Local anaesthesia is usually required. Tetanus must be considered in any wound that is more than purely superficial, and tetanus toxoid given if immunisation is lacking or uncertain. Grazes may need cleaning of road dirt but generally just require dressing with perforated nonadherent dressings, such as Mepitel.

Intermediate Soft Tissue Injuries

Traumatic wounds are inevitably contaminated by bacteria from skin flora, but there is also potential deeper inoculation resulting from the injury. Colonisation may progress to infection that needs treatment. If there is evident nonviable tissue, debridement must be performed to permit assessment and to reduce the risk of infection. Deciding the extent of debridement requires experience. Deep, soil-contaminated wounds (however small) in a nonimmunised patient also warrant prophylactic penicillin, effective against clostridia, and should not be closed until a few days later (delayed primary closure).

Foreign Bodies

Detailed history about the injury helps determine whether foreign bodies are likely to be retained in the wound. The main types of foreign bodies are agricultural and road dirt, wood splinters, and glass and metal fragments. Plain radiology reveals metal and usually glass ( Fig. 17.1 ) but a negative x-ray does not exclude its presence. Remember that a foreign body unrecognised at the time may result in litigation later.

As a principle, foreign bodies should be removed, especially if organic (e.g., wood) or likely to be contaminated. Badly contaminated wounds need debridement and even scrubbing under general anaesthesia (GA). However, glass and metal fragments are often small, multiple and deeply embedded and may be difficult to locate at operation despite x-ray or ultrasound guidance. In these, it is best not to embark on exploratory surgery but to leave the fragments in situ, where they rarely cause complications. The patient must be informed about what has been left and warned that fragments often work their way to the surface and are shed, and to return if problems occur . This must be recorded in the patient’s notes in case of future legal action.

Case HistorIES

Site of Injury

This influences how the wound is managed and its healing. All soft tissue injuries should be assessed early on for potential injury to deep or vital structures and certainly before using local anaesthesia. In the limbs, distal perfusion should be assessed and action taken if inadequate. When bleeding is difficult to control, focused pressure on the wound with swabs usually arrests it pending exploration. Neurological injury should be assessed in terms of sensory change and motor function. Lastly, the integrity of underlying muscles and tendons should be considered. If necessary, the wound is explored and relevant structures repaired.

Soft tissue limb injuries may be associated with an underlying fracture. Principles of wound management include early wound closure or soft tissue reconstruction, plus the need for fracture treatment. Antibiotics should be given because of the higher risk of infection. Guidelines, such as BOASTs (British Orthopaedic Association Standards for Trauma and Orthopaedics) for management of open lower limb fractures are available (see: https://www.boa.ac.uk/publications/boa-standards-trauma-boasts/ ).

Flap Lacerations

Relatively minor trauma to the tibia commonly produces a V-shaped flap laceration ( Fig. 17.2 ), particularly in older patients or those on long-term corticosteroids. If untreated, this injury consistently fails to heal because of poor blood supply to the flap and underlying tissue. Attempting to suture or tape a flap into place increases tension, causing ischaemia, tissue loss and ulceration. The most effective management is early excision and immediate split skin grafting (see Ch. 10 , p. 140). This can be performed under local anaesthesia and takes an average of 2 weeks to heal.

Major Soft Tissue Injuries

Major injuries of soft tissues alone requiring hospital treatment are uncommon and can be classified as in Box 17.1 . A primary survey (see Ch. 15 ) determines the order injuries are managed, with life-threatening injuries treated first. For other injuries, the urgency depends on the potential for deterioration (e.g., blood loss, ischaemia or loss of an eye), the risk of infection and availability of appropriate specialists. Contused or contaminated wounds need early cleansing and excision of all devitalised tissue (debridement), usually under GA. If substantially contaminated, wounds are often left unsutured to prevent wound infection and are then sutured a few days later by delayed primary closure . Less commonly, wounds are left open and are allowed to heal by secondary intention (see Ch. 3 , p. 34). Wounds involving skin loss may need early skin grafting (see Ch. 10 , p. 140).

Injuries to a Vital Part of the Body

Eye

Injuries greater than ‘sand in the eye’ are best managed by ophthalmic specialists who use a slit lamp and other equipment to assess the injury. Typical injuries include abrasions to the cornea, penetrating injuries (dart or pellets) and firework injuries.

Case History

Neck

Penetrating injuries to the neck must be treated with respect. Vital structures are concentrated here and may be injured. These include major arteries and veins (carotid, jugular, subclavian, vertebral), the brachial plexus, some cranial nerves, the cervical sympathetic chain (see Fig. 17.3 ), and lung and pleura.

Lacerations to the Limbs and Hands

(for Traumatic amputation , see p. 264)

Many of these are industrial injuries. The main considerations are:

• Possible nerve, tendon or vascular injury —assessment includes testing sensation, movement, peripheral pulses and tissue perfusion (i.e., pulses, warmth, colour, capillary refilling after blanching). Tendon and nerve injuries are covered later.

• Tissue viability —particularly important in crush injuries and flap lacerations. such as in the pretibial area (see earlier).

• Risk of infection —the fingers and hands are vulnerable to infection of pulp spaces and the deep palmar space. Wounds need antibiotic prophylaxis against Staphylococcus and Streptococcus (e.g., flucloxacillin plus amoxicillin). They also need meticulous cleansing and exploration, if possible by a specialist hand or plastic surgeon. Injuries from bites (especially by dogs, cats or humans) and bones (usually in meat workers) almost invariably become infected (see later).

Extensive Facial Lacerations

Facial injuries should be thoroughly cleaned and examined under local or GA to determine the extent of the damage before repair, ideally within 12 hours of injury. Facial wound edges need minimal trimming. Important anatomical boundaries should be aligned first; these include the vermilion border of the lip, the rim of the eyelid and the eyebrow. Tissue layers should then be approximated individually—mucosa, muscle, cartilage and skin. Parotid duct injury should be considered in deep lacerations of the cheek and the duct repaired if possible. Photographic documentation is useful to help the patient appreciate the extent of injury and to provide an accurate record of progress.

Facial nerve integrity should be determined before anaesthesia is given. Nerve branches should be repaired (usually by a plastic surgeon with microsurgical skills). Those caused by a laceration posterior to a vertical line from the lateral canthus of the eye do better than those anterior to this. Nerve repair should be performed no more than 72 hours after injury.