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Surgery and Surgical Procedure

WOUND TISSUE REPAIR and SCARS

Wounds
Wounds and their management are fundamental to the practice of surgery. Any elective surgical intervention will result in a wound in order to gain access to and deal with the underlying pathology. In the surgery of trauma the wound is the primary pathology In both situations the surgeon’s task is to minimise the adverse effects of the wound, remove or repair damaged structures and harness the processes of wound healing to restore function.

Wound Healing
In human regeneration is limited to epithelium and the liver; most tissues heal by repair resulting in scarring. Wound healing is the summation of a number of processes which follow injury including coagulation, inflammation, matrix synthesis and deposition, angiogenesis, fibroplasia, epithelialisation, contraction, remodelling and scar maturation (Fig. 3.1). Where wound edges are apposed healing proceeds rapidly to closure; this is known as healing by first intention or primary healing (Figs 3.2 and Fig 3.3). Where the wound edges are apart, such as when there has been tissue loss, the same biological processes occur, but rapid closure is not possible. Angiogenesis and fibroblast proliferation result in the formation of granulation tissue. This contracts to reduce wound area and allows epithelialisation across its surface to achieve wound closure. This is known as healing by second intention (Fig 3.4). This process is slower, the contraction involved may cause contracture and functional restriction (Fig. 3.5),and the resultant healed surface is a thin layer of epithelium on scar tissue that may not prove durable in the long term. In general, healing by second intention will give a worse aesthetic outcome. It is because of the poor functional and aesthetic results of healing by second intention that surgical endeavour is usually directed towards achieving primary wound healing.

Classification of wound
A wound can be caused by almost any injurious agent and can involve almost any tissue or structure. The most useful classification of wounds from a practical point of view is that of Rank and Wakefield into tidy and untidy wounds.
Tidy wounds
Tidy wounds are inflicted by sharp instruments and contain no devitalised tissue (Fig. 3.6); such wounds can be closed primarily with the expectation of quiet primary healing. Examples are surgical incisions, cuts from glass and knife wounds. Skin wounds will usually be single and clean cut. Tendons, arteries and nerves will commonly be injured in tidy wounds, but repair of these structures is usually possible (Fig. 3.7). Fractures are uncommon in tidy wounds.
Untidy wounds
Untidy wounds result from crushing, tearing, avulsion, vascular injury or burns, and contain devitalised tissue (Fig. 3.8). Skin wounds will often be multiple and irregular. Tendons, arteries and nerves may be exposed, and might be injured in continuity, but will usually not be divided. Fractures are common and may be multifragmentary. Such wounds must not be closed primarily; if they are closed wound healing is unlikely to occur without complications. At best there may be wound dehiscence, infection and delayed healing, at worst gas gangrene and death may result. The correct management of untidy wounds is wound excision, by this is meant excision of all devitalised tissue to create a tidy wound. Once the untidy wound has been converted to a tidy wound by the process of wound excision it can be safely closed (Fig. 3.9) (or allowed to heal by second intention).
Wound excision
The most important step in the management of any untidy wound is wound excision. This process is sometimes called ‘wound toilet’ or ‘debridement’. The former implies washing and the latter laying open or fasciotomy, all of which may be important in wound management but do not describe excision of devitalised tissue which is the most important process. For this reason the term ‘wound excision’ is preferred. In order to excise a wound adequate anaesthesia — local, regional or general  must be provided. Where possible a bloodless field also aids identification of structures. For superficial wounds the use of local anaesthetic with 1 in 200 000 adrenaline gives good haemostasis of skin edges. In the limbs a pneumatic tourniquet is used. It is helpful to use a skin marking pen to plan the skin excision and any wound extensions. Excision should proceed in a systematic fashion dealing with each tissue layer in turn, usually starting superficial and moving deep. Longitudinal structures such as blood vessels, nerves and tendons are identified and exposed, but left incontinuity. With experience the surgeon learns to recognise dead tissues. Devitalised dermis is pink rather than white; devitalised fat is pink rather than yellow; devitalised muscle is a dark colour, has lost its usual sheen and turgor, and does not twitch when picked up with forceps. Bone fragments with no soft-tissue attachment or nonvital soft tissue attachments are also discarded. This approach to radical wound excision is sometimes called a ‘pseudotumour’ approach, because the entire wound is excised with an appropriate margin back to healthy tissue (Fig 3.8 and Fig 3.9). At the end of wound excision the wound should resemble an anatomical dissection. Normal bleeding should be observed from each layer. Occasionally in very extensive wounds this radical approach must be modified. Where radical wound excision would threaten the via­bility or function of the limb it is reasonable to excise what is definitely nonviable, carry out fasciotomy as appropriate and dress the wound, with a view to returning 48 hours later for a second look, and thereafter further serial wound excisions until a tidy wound is achieved.

Wound closure
Wound closure can be achieved by number of differing techniques. Most tidy wounds that do not involve loss of tissue can be closed directly. Where there is tissue loss a technique to import appropriate tissue is needed. Reconstructive plastic surgical techniques can range from simple skin grafts to complex composite free tissue transfers (Table 3.1). This list used to be described as a ‘reconstructive ladder’; unfortunately this implies that the correct approach is to use the simplest technique and only when it fails move to a more complex technique. This approach is not appropriate in modern surgical practice. The available techniques should be regarded as a ‘toolbox’ from which to select the technique that provides most rapid healing, earliest return to function and superior aesthetic outcome.

Types of wound
Bruise, contusion and haematoma

A closed blunt injury may result in a bruise or contusion. There is bleeding into the tissues and visible discoloration. Where the amount of bleeding is sufficient to create a localised collection in the tissues, this is described as a haematoma. Initially this will be fluid, but it will clot within minutes or hours. Later, after a few days, the haematoma will again liquefy. There is a danger of secondary infection. Bruises require no specific management, and no treatment is of proven value. The patient should be advised that the time required for bruising to clear is extremely variable and in some individuals, in some sites, discoloration may persist for months. A haematoma should be evacuated by open surgery if large or causing pressure effects (such as intracranially), or aspirated by a large-bore needle if smaller or in a cosmetically sensitive site. It may be necessary to await liquefaction (which may take several days) and to perform repeated aspirations, with appropriate antiseptic precautions. A haematoma will generally reabsorb without scarring, but on occasions there may be persistent tethering of the skin. Blunt injuries may cause a variety of fat injuries. A blunt injury to the breast may result in an area of fat necrosis that can masquerade as a breast lump. Blunt injuries to the face may result in lumpy subcutaneous collections due to haematoma in subcutaneous fat that may persist for several months. A fat ‘fracture’ in the buttocks may result from a fall or sharp blow. This can result in separation of subcutaneous fat with an indentation that may not become apparent immediately due to haematoma.
Puncture wounds and bites
A puncture wound is an open injury in which foreign material and organisms are likely to be carried deeply into the underlying tissues. Common causes are standing on a nail or other sharp object. There may be little to see on the surface. Radiological examination may detect metal fragments or glass. Treatment is essentially by wound irrigation, antibiotic treatment and tetanus prophylaxis. Large foreign bodies should be removed, but small particles may be surprisingly difficult to find without a destructive dissection and are better left undisturbed. When a foreign body is visualised ona radiograph a surface marker should be taped to the skin to aid localisation. A metal detector may be helpful during exploration. The danger of puncture injuries is that they may give rise to an abscess deep within the tissues and on such occasions drainage may be required. It is likely that it will take 24—48 hours for an abscess to declare itself and arrangement should be made for review. Needle-stick injuries are a particular cause for concern. Although these are a particular hazard for hospital staff, discarded needles from drug abuse are becoming increasingly a cause of accidental injury in the community. Medical, nursing and ancillary staff should have hepatitis B immunisation. The chance of HIV infection from a needle-stick injury seems to be low but all such injuries should be recorded and, if dealing with a high-risk patient, HIV tests should be performed at 3 and 6 months after the episode. Bites are a particular type of puncture wound associated with a high incidence of infection, presumably from mouth organisms. Animal bites may result in small, sharp, incised wounds or in severe tissue crushing as in horse bites. Dog bites may also be associated with a degree of tissue avulsion (Fig. 3.10), and often there are puncture wounds from upper and lower teeth and contusion of the intervening tissue. Human bites may be associated with avulsion of pieces of the nose or ear. An accidental type of ‘bite’ injury may result from an attacker striking the victim’s incisor teeth with the knuckles. This is a frequent injury that presents with a puncture wound over the metacarpophalangeal (MP) joints. It is important to recognise the nature of the injury as the history is often less than truthful. Radiological examination may demonstrate parts of a tooth within the MP joints. As all of the layers over the joints glide over one another on making a fist, the through-and-through nature of the puncture wound is often not appreciated with the hand extended. If there has been sufficient force to penetrate the skin, it must be assumed that the MP joint has been penetrated. Such wounds are best treated by open surgical exploration excision of skin margins, irrigation of the joint and antibiotic therapy.
Abrasions and friction burns
An abrasion is a shearing injury of skin in which the surface is rubbed off. Most are superficial and will heal by epithelialisation, but some may result in full-thickness skin loss. Abrasions may be dirt ingrained and if this dirt is not removed at the time of primary treatment permanent tattooing of the skin will result. Treatment is by cleaning with a scrubbing brush, gently brushing along the grain of the scratch lines. A friction burn is similar, but there will be an element of thermal damage as well as abrasion. Treatment is as for other types of burn.
Laceration
A laceration or cut is the result of contact with a sharp object (the surgical equivalent is an incised wound). Once the cutting implement has gonc deep to the dermis, there is less resistance in the subcutaneous tissues and the cut may therefore penetrate to a considerable depth. It is important to ascertain from the history the amount of force involved. The clinical examination must therefore assess the integrity of all structures in the area: arteries, nerves, muscles, tendons and ligaments (Fig. 3.6). The ideal form of management of an incised wound is surgical inspection, cleaning and closure. The wound must be thoroughly inspected to ensure that there is no damage to deep structures or, where encountered, these must be repaired (Fig. 3.7). As a general rule, the damage to nerves and tendons is generally greater than suspected preoperatively. Once all of the damaged layers have been identified, each structure must be repaired individually by the appropriate technique. Haemostasis must be ensured throughout the exploration. There are precise suture placement techniques for nerves, tendons and blood vessels. Muscles can be apposed in layers by mattress sutures and fascia, and subcutaneous fat should be opposed by interrupted absorbable sutures to allow a firm platform for skin closure in such a way that the skin margins do not invert. It is an important principle to prevent collections of blood or other fluids in a wound as they separate tissues and act as a nidus for infection. A corrugated or suction drain may be required. In a simple incised laceration, a method of wound closure should be selected which is appropriate for the needs of function and appearance. On the face, fine (5/0or 6/0) nylon sutures should be placed near to the wound margins, to be removed on the fifth day. Alternatively, subcuticular (intradermal) sutures avoid suture marks and can be left in place longer (2 weeks or more). An alternative to suturing is the application of adhesive tape strips. It is necessary to apply these with the same care as sutures ensuring that all bleeding has stopped and that the skin is dry. For limb and trunk wounds, a heavier suture is required but it is rarely necessary to use more than 4/0 or 3/0 sutures for skin closure. Monofilament sutures, such as nylon, are said to leave less obvious suture marks than braided material such as silk, but other factors contribute to stitch marks, such as inflammation (from infection or reaction to organic material such as silk),wound tension and late removal. All patients sustaining open wounds should have prophylaxis against tetanus, and antibiotics should be administered where there is significant contamination, commencing generally with a broad-spectrum antibiotic active against Gram positive organisms.
Traction and avulsion
Avulsion injuries are open injuries where there has been a severe degree of tissue damage. Such injuries occur when hands or limbs are trapped in moving machinery, such as in rollers, producing a degloving injury. Degloving is caused by shearing forces that separate tissue planes, rupturing their vascular interconnections and causing tissue ischaemia. This most frequently occurs between the subcutaneous fat and deep fascia. Degloving injuries can be open or closed. Degloving can be localised or circumferential. It can occur only in the single, subcutaneous plane, but where present in multiple planes, such as between muscles and fascia and between muscles and bone, is an indication of a severe high-energy injury with a limited potential for primary healing. Similar injuries occur as a result of runover road traffic accident injuries where friction from rubber tyres will avulse skin and subcutaneous tissue from the underlying deep fascia (Fig. 3.11). The history should raise the examiner’s suspicion and it is often possible to pinch the skin and lift it upwards revealing its detachment from the normal anchorage. The danger of degloving or avulsion injuries is that there is devascularisation of tissue and skin necrosis may become slowly apparent in the following few days. Even tissue that initially demonstrates venous bleeding may subsequently undergo necrosis if the circulation is insufficient. Treatment of such injuries is to identify the area of devitalised skin and to remove the skin, defat it and reapply it as a full-thickness skin graft. Avulsion injuries of hands or feet may require immediate flap cover using a one-stage microvascular tissue transfer of skin and/or muscle.
Crush
Crush injuries are a further variant of blunt injury and are often accompanied by degloving and compartment syndrome. Injury to tissues within a closed fascial compartment leads to bleeding, exudate and swelling of these tissues, and increased interstitial pressure. As the interstitial pressure rises above capillary perfusion pressure the blood supply’ to the viable tissues is reduced, resulting in further ischaemic tissue injury and swelling (Fig. 3.12). This cycle causes a worsening compartment syndrome with muscle ischaemia and nerve ischaemia progressing to muscle necrosis, skin necrosis and limb loss. Muscle necrosis may result in renal failure. This process can be arrested by early recognition and decompression of the affected compartment(s) by fasciotomy. The most reliable clinical sign of compartment syndrome is pain worsened by passive stretching of affected muscles. Where any doubt exists compartment pressure measurements can be carried out. Loss of peripheral pulses is not a sign of compartment syndrome, but indicates major vessel damage. Where compartment syndrome is suspected or confirmed fasciotomy is advised. Longitudinal incisions are made in the deep fascia and it may also be necessary to make extensive longitudinal releases in the skin. It is important to release the fascia over each individual compartment in a limb.

September 20, 2008 Posted by | WOUND TISSUE REPAIR and SCARS | , , | Leave a comment

   

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