Wound closure and reconstruction should aim to return the patient to normal function as soon as possible. To achieve this aim, the key question in decisionmaking is when and how should a particular wound be closed. To answer this question, the veterinary surgeon must take into account a number of factors, such as the overall condition of the patient, how was the wound caused and the degree of trauma at the site of the wound. Failure to take such factors into account may lead to not only local wound complications and dehiscence, but with severe trauma, the consequences to the patient could be catastrophic.

Evaluating the Local Wound

The likelihood of success in deciding when to close a traumatic wound depends on a number of factors:

 The degree and type of bacterial contamination

 The degree of contamination with foreign material

 The degree of tissue ischaemia

 The time from trauma to presentation

 The type of wound

 The amount of local tissue loss

There are no absolute rules as to the timing of traumatic wound closure, as each wound is different. However, it is important to remember that contaminated wounds should not be closed primarily, and in such situations, appropriate open wound management should be used. If the veterinary surgeon has any doubt as to the degree of contamination, it is safer to deal with the wound as an open wound.

Contaminated wounds should never be closed primarily.

Timing of Wound Closure

The four options for closing a wound are:

1.  Primary closure

2.  Delayed primary closure (closed after 48–72 hours, before granulation tissue develops)

3.  Secondary closure (closed after granulation tissue develops, 5–7 days)

4.  Second intention healing (contraction and epithelialisation)

Closure options for traumatic wounds

Modified from BSAVA Manual of Canine and Feline Wound Management and Reconstruction. 1st ed.

The decision on which reconstructive closure technique to use should be based on aiming to obtain rapid wound closure with the simplest technique possible and with minimal compromise of function, patient morbidity and cost. This is a very well established principle in human surgery where plastic surgeons refer to the "reconstructive ladder". The more extensive or difficult a wound is, the higher up the ladder the surgeon has to climb to find an appropriate technique, such a ladder helps in the decision making process, but individual surgeons may have personal preferences as to technique, which will sway them more to one technique than another.

The reconstructive ladder

The surgeon must always remember that wound reconstruction is often an exciting surgical challenge, but the technique chosen should be for the benefit of the patient and not the surgeon.

Primary Closure

The cardinal rule of wound reconstruction is to avoid excessive wound tension. Wounds with adequate elastic surrounding skin can be closed using direct skin mobilization. Appositional suturing techniques should be used to minimize tension on the wound. Placement of skin sutures is important so that optimal healing will occur; sutures should be placed some 3–5 mm from wound edges and spaced at intervals of about 5 mm so that tension is spread evenly and there is minimal interference with local blood supply. In practice, the spacing between sutures will, however, vary with the length of wound and gauge of suture used. It is also useful to take a wider bite at the deep part of the wound; this helps to slightly evert the wound edges; this helps to create a flatter scar when the sutures are removed. The bite taken is important in creating accurate apposition; the suture can be adjusted to even out slight discrepancies in the wound edge apposition. Sutures should not be tied too tightly as, in addition to causing discomfort, they will disrupt local blood supply and lead to delayed healing. Skin sutures should allow for slight oedema of the skin, which will occur during healing. If a suture loop is tight initially, then the suture will cut into the skin and be irritating to the patient as well as potentially compromising the local circulation, as wound oedema occurs.

Delayed Primary Closure

Wound contraction is seen in healing open wounds in 5–9 days, and results in a centripetal reduction in the size of the wound. The process of wound contraction stops when wound margins contact each other or when tension from the skin adjacent to the wound is equal to, or greater than, the contractile forces generated by myofibroblasts within the granulation tissue. In dogs and cats, wound contraction is more rapid on the trunk than the extremities because of the larger amount of skin available and its inherent elasticity.

Wound contraction is facilitated by:

 A moist wound bed

 Adequate debridement

 Control of wound infection

Inadequate debridement is the most common reason for delayed wound healing and persistent wound infection. Wound contraction is delayed by:

 Wound infection

 Desiccation

 Exposed bone

 Exuberant granulation tissue

The normal process of wound contraction can be facilitated by:

 Presuturing lesions prior to excision

 Placement of tension sutures

 Using skin stretching devices across open wounds

Closure of large trunk wounds, or smaller wounds of the extremities, may be difficult without excessive tension. The elastic properties of skin can be used to advantage in these situations. Presuturing of wounds, by the placement of several mattress sutures adjacent to the area of excision, can be used to mobilize skin for subsequent wound reconstruction in planned excisions. In traumatic wounds, intradermal tension sutures can be placed along the wound edges. The continuous intradermal suture is tightened on a daily basis, facilitating contraction of the wound margins. This process of 'enhanced contraction' will greatly reduce the length of time required to achieve closure of large cutaneous deficits. Alternatively, an external skin stretching device can be used (Pavletic 2000).

Reconstructive Skin Techniques

If simple tension relieving techniques do not result in closure or appear to place undue tension on the wound, more advanced reconstructive techniques, such as subdermal plexus flaps, axial pattern skin flaps or free skin grafts, should be considered. Once debridement and preparation are complete, surgical reconstruction can be planned. Reconstructive techniques should be used so as to achieve early coverage of vital structures, promoting an early return to function. The various reconstructive techniques described will be discussed in greater depth during the lecture.

Sub Dermal Plexus Flaps

Pedicle flaps refer to elevation of an area of skin that remains attached to its vascular bed. Local subdermal plexus flaps are by definition flaps that have a vascular supply provided by the subdermal plexus from the flap base without the known inclusion of a direct cutaneous artery and vein.

They are mostly harvested from skin adjacent to the primary defect and are one of the most frequently used flap types due to their simplicity and versatility. Certain guidelines need to be followed to ensure optimal results.

Blood Supply to Local Flaps

Local flaps possess a less reliable blood supply than axial pattern flaps as they are dependent upon the subdermal plexus alone. The dimensions of a flap are critical in determining flap survival and depend to a large extent on vascular supply, although factors such as tension, motion and trauma also play significant roles.

No linear relationship exists between flap dimensions and flap survival. Therefore, it is difficult to give accurate guidelines that surgeons can use when elevating flaps.

1.  Create flaps that are just large enough to cover the primary defect, and avoid flaps that are very long.

2.  Maximise the width of the base of the flap as much as possible. A 2:1 flap length:base width ratio is a good guideline.

In general, a greater base width to flap length ratio will not guarantee flap survival if the flap is too long, but will maximise the chances of inadvertently including larger cutaneous vessels.

Flap Elevation

The elevation of local flaps can be done in several ways. The preferred technique is to sharply incise skin with a scalpel blade. Once the skin has been incised, elevation of the flap proceeds by undermining deep to the subdermal plexus. Once the flap has been elevated, careful handling is essential. With any defect, there is always a choice of harvest sites for local flap creation. Selection of flap type will be based upon several factors, but in all cases the simplest flap type that is likely to be successful should be chosen. Flaps can be created by advancing skin in a straight direction (advancement flap), a rotational pattern (rotation flap) or skin can be transposed into position by pivoting it 30°–120° from its base (transposition flap). When flaps are created, there remains a donor bed that is usually closed primarily. The defect created must not expose vital structures. It must not be in a high motion area and, ideally, it should not be difficult to close. There must be adequate elasticity and motion of the flap, or movement into the primary defect will not be possible. Areas with extensive scarring are not good potential flap beds.

Axial Pattern Skin Flaps

Axial pattern flap circulation depends on preserving a direct cutaneous artery to the area of skin in question. The flap will survive based only on the vascular attachment. These flaps can be created to be longer than subdermal plexus flaps; therefore, their range of use and their ability to manage large defects particularly of the extremities by immediate closure is a great advantage. In addition, axial flaps provide full thickness skin and can be combined in some regions with muscle, resulting in musculocutaneous composite flaps. The major disadvantage of axial flaps is that flap designs are restricted to the sites with a well-defined and robust direct cutaneous artery.

Skin Grafts

Free skin grafts in dogs and cats are usually full thickness. They may be applied immediately to sterile wound beds with a good blood supply, such as regions of the face or on muscular surfaces, or to mature granulation tissue. Variations of free skin grafts include sieve, punch, meshed and strip grafts.

References

1.  Pavletic MM. Use of an external skin-stretching device for wound closure in dogs and cats. J Am Vet Med Assoc. 2000;217:350–354.

2.  Williams J, Moores A. BSAVA Manual of Canine and Feline Wound Management and Reconstruction. 2nd ed. Gloucester, UK: BSAVA; 2009.