For the sake of simplicity, the limbs can be divided into three zones.

 For the forelimb: the region proximal to the elbow, the central region between the elbow and carpus and the distal region from the carpus to the digits.

 For the hindlimb: the area proximal to the knee; the central zone between the knee and tarsal joint; the lower region from the tarsus to the digits.

The availability of regional loose, elastic skin adjacent to any skin defect will influence your closure options. The upper zone of the extremities is adjacent to the trunk, a potential donor area for challenging skin wounds. Depending on the magnitude of the wound, undermining/closure is more likely in this proximal zone because of the greater degree of skin laxity. Skin flaps and skin stretchers are especially useful for wounds proximal to the knee and elbow. That is not to say that local flaps cannot be used below these anatomical landmarks; rather, there is less skin for creating large local flaps. As will be discussed in the lecture, small flaps can be very effective in closing many problematic wounds of the lower extremities. Depending on the magnitude of wounds involving the middle to lower limb regions, skin grafts become increasingly important as you progress from the middle to lower zones of the extremities. Wounds involving the olecranon are among the most challenging to close. Local flaps, release incisions and axial pattern flap options have been used depending on the magnitude of the wound. The author has developed a simple protective device for the elbow using common pipe insulation used by plumbers. When dealing with mobile regions (knee, carpus, tarsus) immobilisation of the joint may be needed if there is a potential for motion to disrupt the closure site.

Common options for wound closure proximal to the elbow and knee:

 Second intention healing

 Undermining and closure

 Local flaps

 Axial pattern flaps

 Skin-stretching techniques

Possible options for wound closure between the elbow/carpus and stifle/tarsus:

 Second intention healing

 Undermining and closure

 Release incisions to supplement undermining and closure

 Local flaps

 Axial pattern flaps in selected patients

 Distant flaps

 Skin grafts

 Tissue expanders

Possible options for wound closure below the carpus/ tarsus:

 Second intention healing

 Undermining and closure

 Release incisions to supplement undermining and closure

 Local flaps

 Distant flaps

 Skin grafts

Brief Review of Techniques

Second Intention Healing

In the central and lower zones, wounds involving a quarter of the circumference or less are likely to heal by second intention. Wounds approaching or exceeding half the limb circumference are unlikely to heal by contraction and epithelialisation without surgical intervention. In some cases, the veterinarian may be able to take advantage of this healing process in order to reduce the magnitude of a wound, thereby permitting the surgeon to use a smaller flap or graft to close the wound more economically at a later date. It is important to remember that the magnitude of a wound is increased secondary to swelling and elastic retraction of the dermal collagen. Wounds may be 25% smaller than your initial assessment of the defect. With resolution of swelling several days later, it may be readily apparent that the wound can heal by second intention or simple closure.

Undermining/Closure

Undermining can mobilise skin as long as it is performed carefully to preserve the blood supply. Release incisions can be useful in facilitating closure if incisional tension is evident.

Note: Closure of lower extremity wounds under tension can create a biological tourniquet that may seriously restrict arterial circulation, venous return and lymphatic return. Massive swelling may occur below the closure, unless promptly addressed by cutting all the sutures. Left untreated, loss of the tissues below the biological tourniquet may occur. This can be prevented by avoiding closing wounds where a palpable skin tension band can be felt during closure. It would be safer to consider healing by second intention in these problematic closure cases. Release incisions also can be used to prevent this serious problem during wound closure.

Release Incisions

Single or multiple release incisions have been described to close wounds, allowing a wound to be sutured closed in exchange for creating a donor defect that may be better suited to heal by contraction and epithelialisation. This category would include Z-plasty variations.

Local Flaps

The transposition flap is the most useful of the local flap techniques available to close smaller problematic wounds. As you travel distally, smaller flaps may be developed parallel to the long axis of the extremity. Careful measurement is needed to ensure the donor area can be closed without creating excessive circumferential tension on the limb. It is important to note that, in smaller problematic wounds, a flap need not cover the entire defect. Rather, a flap can be used to cover the central area of the defect, leaving the remaining exposed wound margins to heal by second intention.

Skin Stretchers

There is a separate lecture on this subject at this meeting. Skin stretchers can facilitate closure of sizeable wounds, especially those involving the upper extremities and trunk region. Stretching is less effective for lower extremity defects. However, the intraoperative use of skin hooks may be used to stretch the skin using 1-minute stretch-relax cycles over several minutes to gain an additional centimetre of two to suture a smaller problematic wound closed.

Axial Pattern Flaps

The thoracodorsal, omocervical, lateral thoracic and brachial axial pattern flaps have potential use for closure of wounds involving the upper extremity, elbow, antecubital area and variable portions of the mid-forelimb area. The deep circumflex iliac, caudal superficial epigastric and genicular axial pattern flaps can be used for upper and mid-hindlimb defects. How far a given axial pattern flap can extend distally is largely dependent on the size of the wound, conformation of the patient and species/breed variations. Axial pattern flaps would be reserved for the most challenging wounds, in the event that simpler closure options (or combined techniques) are not feasible.

Tissue Expanders

Tissue expansion can be achieved by implantation of expandable silicone elastomeric devices beneath the skin. The reservoir is slowly expanded by injecting incremental doses of saline through an attached injection port on an alternate day basis. Flaps created from the expanded donor area can be used to close defects over the carpus and metatarsal/metacarpal regions. They are not routinely considered by veterinarians due to the high cost of purchasing these reusable implants. Nonetheless, this technique should be kept in mind when facing a challenging extremity wound.

Skin Grafts

Skin grafts remain an important means of closing large skin defects involving the limbs, particularly for the area of the carpus/tarsus distally. The full-thickness mesh graft is a preferred technique. Punch grafts may be considered to promote epithelialisation of problematic, slow-healing open wounds.

Distant Flap Techniques

Distant flaps have fallen out of favour largely due to the need to immobilise the affected limb to the body wall for 2–3 weeks followed by the incremental division of the pedicle to complete the transfer. They still remain a potentially useful option for selected challenging wounds.

Final Comments

Always consider the simpler closure techniques first, as long as they have a realistic chance of working. Consider combining simple closure options. Reserve mesh grafts, tissue expanders, distant flaps and axial pattern flaps for the larger challenging wounds.

References

1.  Pavletic MM. Atlas of Small Animal Wound Management and Reconstructive Surgery. 3rd ed. Ames, Iowa: Wiley-Blackwell. 2010.