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successful and the surgeon should manually assess theskin tension and pliability by pushing neighbouringskin towards the centre of the wound beforeplanning the closure.

Regardless of the type of closure selected, it isimperative when performing reconstructive surgerythat Halstead’s principles are adhered to (Table 1).

The single, most important consideration in woundreconstruction is the avoidance of wound tension.Surgeons may minimise this by suturing the woundperpendicular to the lines of skin tension,undermining of surrounding tissues, making a Z orV-Y-plasty, or releasing incisions parallel to the linesof skin tension (take care to consider the local bloodsupply before doing this). Skin sutures should beplaced 5 mm apart and 5 mm from the wound edgesto spread tension evenly and to interfere minimallywith blood supply. The authors prefer to use a simpleinterrupted pattern using a non-absorbablemonofilament nylon (or skin staples) and use tensionrelieving sutures judiciously because they can readily overtighten.

If tension is still too great, wound closure can befacilitated further by the use of tension sutures, pre-suturing wounds 48 hours prior to closure, or usingskin stretchers. Skin stretchers rely on aphenomenon called mechanical creep, where skin iscapable of extension beyond its inherent elasticityover time when stretching or a tension force isapplied over time. Stress relaxation is simultaneouslyseen, whereby a progressively reduced force can stillmaintain the stretched dermal collagen fibres at aspecific length. Skin stretchers have been used to aidskin closure in large wounds involving the trunk, buthave also been described for wounds on the flank,pelvic region and distal limbs. Adhesive pads areapplied on either side of the wound and connectedunder moderate tension using elastic cables. Every 6-8 hours, the tension is increased slightly andmaximal skin stretching will be achieved after 72 hours (Pavletic, 2000). This will allow skin healing

Before considering wound closure, the wound bedshould be clean and free from necrotic tissue andinfection (see previous article UK Vet Vol 16 No 4).Once this has been achieved, healing can becompleted by:� primary closure, which is appropriate if the

wound has occurred recently and is clean orclean-contaminated. Appropriate cleaning andcopious lavage should be performed before suturing

� delayed primary closure, which is performedthree to five days after the wound occurs andallows time for elimination of contamination andevidence of ischaemia. Closure is performedbefore a granulation bed forms

� secondary closure occurs after the formation ofa granulation bed and follows open woundmanagement for more than five days. This wouldbe desirable for an infected wound

� second intention healing is wound healing bycontraction and epithelialisation.

When selecting an appropriate method for closure,early wound reconstruction is advised if vitalstructures (e.g. tendons, nerves) are exposed, if tissuereconstruction is required for support (e.g. afootpad), or if a scar may limit function (e.g. eyelid,or an extensive wound located over the flexorsurface of a joint). Second intention healing isappropriate where the wound is on an extremity andis small, or in an area surrounded by abundant skin(e.g. flank). It is advisable to remember that thesimplest method of closure is often the most

Kelly Bowlt BVM&S MRCVS DEPARTMENT OF CLINICAL VETERINARY STUDIES, UNIVERSITY OF BRISTOL, LANGFORD HOUSE, LOWER LANGFORD, BRISTOL, NORTH SOMERSET. BS40 5DU

Ed Friend BVetMed Cert SAS DECVS MRCVSLANGFORD VETERINARY SERVICES, LANGFORD HOUSE, LOWER LANGFORD, BRISTOL, NORTH SOMERSET. BS40 5DU

Small animal wound management: Options for wound closure

Table 1: Halstead’s surgical principles

Strict asepsis

Meticulous haemostasis

Minimal wound tension

Atraumatic tissue handling

Accurate tissue apposition

Minimise dead space

Preservation of local blood supply

ABSTRACT: This article looks at wound closure once a healthy wound bed has been achieved. It discusses simpletechniques for the avoidance of skin tension and includes skin stretching and vacuum assisted wound closure. Finally, techniques and recommendations for free skin grafts and skin flaps are presented. DOI: 10.1111/j.2044-3862.2011.00067.x

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after primary closure where tension allows, or willreduce skin tension and the size of any flap or graftused (Fig. 1). Skin stretchers can also be maintainedpostoperatively to reduce tension on the repair.

Vacuum assisted wound closure (VAC) is anothertechnique recently described in which local negativepressure is applied to a wound in order to promoteremoval of exudates/bacteria, increased localcirculation, rapid formation of granulation tissue andmore rapid wound contraction. Before beginningVAC, it is imperative that the wound is properlylavaged and debrided. A sterile open pore foam(400-600 mm) is then cut to the shape of the woundand applied directly onto the wound. The suctiontubing is passed into the foam and the foam andtubing sealed over the wound using an adhesive film(Fig. 2). A continuous negative pressure of -125 mmHgis typically recommended during VAC of an openwound and bandages should be changed at leastevery 24 hours initially. VAC should not be usedwhere suction of underlying structures is undesirable(e.g. exposed blood vessels), where neoplasia issuspected, or in animals with coagulopathies.

Where primary closure cannot be achieved withminimal tension using the above techniques, skingrafts or flaps may be considered.

FRee SKIN GRaFTS

A free skin graft is a section of epidermis and dermisthat is completely removed and transferred to adistant recipient site. It is mandatory that therecipient bed is either uniform, healthy granulationtissue (Fig. 3) or a fresh, vascular surface which isinfection and debris free (e.g. following surgicalexcision of a wound bed).

Fig. 1a: This cat has sustained a wound to the ventralthorax.

Figs. 1b and 1c: Skin stretchers are applied usingadhesive pads glued to the skin surrounding thewound (i) and connected under tension with adhesivestrips (ii). The wound bed is protected using a foamdressing. After 48 hours, skin stretch is sufficient thatthe wound can be closed following appropriatedebridement and skin undermining.

Fig. 1c.

Fig. 3: Before considering free skin graft, it is imperative that the wound bed iscovered with healthy granulation tissue. (Image courtesy of Peter Delisser.)Fig. 1d: Healing progresses without incident.

Fig. 2: The application of VAC onto a wound on the lateral thigh of a cat.

Free skin grafts take by: 1. adherence: a tight fibrin seal forms between the

wound bed and the graft. This occurs within thefirst eight hours and is strongest at ten days.

2. Plasmatic imbibition: after harvesting, the bloodvessels within the graft undergo spasm and expelmost of their serum-like contents into thepotential space between the graft and the bed.The vessels then dilate after graft placement andcapillary action pulls the fluid into the graftvessels, providing nutrition and keeping themopen until revascularisation can occur. The graftat this stage (48-72 hours after placement) willappear oedematous and cyanotic.

3. Inosculation: anastomosis of the graft andrecipient blood vessels, which occurs between 48and 72 hours.

4. Ingrowth of new blood and lymph vessels.

The most common type of graft in veterinarymedicine is a full thickness free skin graft.

After the recipient site has been deemed suitable andperipheral epithelial tissue has been excised, a tracing

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of the wound should be achieved in order todetermine the size and shape of the donor tissueharvested. The skin edges of the graft should behandled with stay sutures (Fig. 4) to minimise traumaand the graft kept moist and stretched onceharvested (the authors fix the graft to a section ofcard using hypodermic needles to achieve this). Allthe subcutaneous tissue covering the graft isdiligently and thoroughly removed before parallelrows of full thickness staggered incisions are made(1-2 cm long and 1-2 cm apart). This meshing allowsdrainage of fluid from the site, allows smaller donortissue to cover a larger area and also permitsflexibility and conformity. The graft is immobilisedon the wound bed using simple interrupted suturesalong the edges and at the level of intermittent slitsif required (Fig. 5).

After graft placement, a sterile non-adherent dressing(e.g. foam dressing, Alleyvn) or petroleumimpregnated gauze (e.g. Jelonet) should cover thesite, followed by an absorbent secondary layer andporous tertiary layer. The authors do not change this

Fig. 6a: Skin graft (as in Fig. 5) 48 hours following completion of surgery. Notethe variation in colour along its length which is not yet indicating graftsuccess/failure at this stage.

Fig. 6b: Same graft 10 days following surgery.

Fig. 6c: The cosmetic result for this cat is excellent.(Image courtesy of Peter Delisser.)

Fig. 4: The graft used to cover the defect seen in Fig. 3 is harvested from thelateral thoracic wall and is handled with stay sutures to minimise trauma. (Image courtesy of Peter Delisser.)

Fig. 5: The graft is fenestrated and is secured over the defect using simpleinterrupted sutures. (Image courtesy of Peter Delisser.)

dressing for 48 hours following surgery to minimisedisplacement of the graft and for this reason,subsequent dressing changes are performed undergeneral anaesthesia for the first 10-14 days. It is

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imperative that the wound is not cleaned in the earlystages and that adequate site immobilisation occurs,particularly where the wound overlies a joint.Survival for this type of graft when performedcorrectly is over 90% (Fig. 6).

FlaPS

Skin flaps (pedicle grafts) should be consideredinstead of free skin grafts where the wound bedcannot support a free skin graft (e.g. it containstendon, bone etc), where there is insufficientvascularity, where the area is difficult to immobilise,or where a robust, padded repair is essential (e.g. overa bony prominence). A list of different types of flaps

Fig. 7: The avulsion injury on the ventral mandible of this catcan be repaired using a single pedicle advancement flap.

Fig. 8c: The thoracodorsal artery and vein originatesat caudal shoulder depression at a level parallel to thedorsal point of the acromion (star). The landmarksfor the incisions (white lines) are:Cranial: at the level of the scapula spineCaudal: parallel to the first incision, double thedistance from the first incision and the caudal borderof the scapula (green line) Dorsal: The length of the flap can be as far as thedorsal midline

Fig. 8d: After complete elevation, the flap is swungcaudally and ventrally to cover the defect.

Fig. 8e: The flap is secured in position with skinsutures or staples and the donor site closed primarily.Note the placement of the active suction drain.

Fig. 8a: Presenting wound on the ventral thorax of a small breed dog.

Fig. 8b: After daily flushing and wet-to-dry dressings, the wound has developeda healthy granulation bed and the necrotic tissue has been removed.

is outside the scope of this article and further, morespecific details (including anatomical landmarks) arepresented by Pavletic (2010).

When planning a flap, the simplest method ofclosure is usually the most successful. Generalconsiderations during planning should include: � Avoid using donor sites under excessive motion

or tension� Use a flap with a base wider than the width � Limit the length to that needed to cover the

defect without excessive tension� Avoid back-cutting or excessively kinking the

graft, which could disturb the blood supply.

Most simple pedicle grafts in dogs and cats aresubdermal plexus flaps, which receive blood supplyfrom the subdermal plexus associated with thepanniculus muscle or the dermis (and it is thereforeimportant to incorporate these structures whenundermining skin). local pedicle grafts remain the simplest and most practical means of closingwounds where location allows and are suitable forregions such as the trunk or head. They are generallyeither rotating or advancement flaps. Examples of this include: � Transposition flap� Single pedicle advancement flap (Fig. 7)� Bipedicle advancement flap (H-plasty).

An axial pattern flap incorporates a direct cutaneousartery and vein, allowing the graft to be 50% largerthan that of subdermal plexus flaps and reducing therequirement for a delayed procedure. They areparticularly useful in distal limbs whereneighbouring skin is limited. The four major directcutaneous arteries are the cervical cutaneous branchof the omocervical artery, the thoracodorsal artery(Figs. 8a-8e), the deep circumflex iliac artery (dorsaland ventral branch) and the caudal superficialepigastric (Fig. 9a-9c). Further details and anatomicallandmarks can be found from Pavletic (2010).

Following the performance of flaps, the authors donot apply bandages to the surgical site in case thisrestricts blood flow to the flap. In addition toreducing dead space intra-operatively by usingsimple interrupted sutures, active suction drains arealso commonly applied to minimise the formation ofseromas or haematomas, although this is less crucialthan with a free skin graft because flaps rely on theirown blood supply for survival rather than theingrowth of new vessels from the recipient bed.

COMPlICaTIONS

Excessive wound tension is a common cause of flapfailure (Fig. 10) and all efforts should be made toavoid this.

Another common cause of flap and graft failure isinadequate blood supply and this can be minimisedby observing Halstead’s principles, ensuring flaps are

© 2011 Blackwell Publishing Ltd

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not excessively kinked and ensuring grafts are free ofall subcutaneous tissue before placement. The use ofmeticulous haemostasis, dressings and drains where

Companion Animal Vol 16 June 201118 © 2011 Blackwell Publishing Ltd

appropriate is also imperative to prevent theformation of seromas or haematomas, which maylead to failure of the repair. Whilst movement is lessof a concern in flaps, this is a major source of failurein grafts and sites should be immobilised for twoweeks. Infection can also cause flap or graft necrosisand death, so the surgeon must be sure that thewound bed is adequately prepared and that asepsis isstrictly observed intraoperatively and duringsubsequent dressing changes.

Wound dehiscence will become obvious from 3-5days post surgery and many attempt have been madeto develop methods of salvage (e.g. use ofvasodilators or steroids), with little success. Usuallyfailure is due to problems with surgery orpreparation of the wound bed rather than anintrinsic inability to heal. If there are small regions ofnecrosis (most usually in the corners or tips of a flap),the authors leave these defects to heal by secondintention. It is rare for an entire pedicle flap to failand if larger areas of flap dehisce, closure can beperformed by a second flap or via the use of free skingrafts once the wound bed has been prepared. Oncethe original flap has become established, it is alsopossible to use it as an advancement flap if indicated. Where free skin grafts fail entirely, the graft usuallyhas to be repeated after appropriate preparation ofthe wound bed. It is important that grafts are givensufficient time to reveal themselves because theiroedematous, cyanotic appearance around 2-3 daysafter placement can be misleading (Fig. 6).

FURTHER READING

PAVLETIC, M. M., (2000) Use of an external skin-stretching device for

wound closure in dogs and cats, Journal of the American Veterinary

Medical Association, Vol 217, No. 3, August 1st, 2000.

PAVLETIC, M. M., (2010) Atlas of Small Animal Wound Management and

Reconstructive Surgery, 3rd Ed. Wiley Blackwell.

Fig. 10: This cat underwent radical resection of an injection site sarcoma.Excessive tension on the suture line has resulted in wound break down.

Fig. 9a: Wide sharp excision of this mast cell tumour on the lateral aspect of adog’s proximal tibia leaves a defect which is not amenable to closure using localtechniques.

Fig. 9b: Elevation of a caudal superficial epigastric flap. The medial incision is theventral midline (black arrow). The lateral incision (green arrow) is parallel to thefirst and at a distance equal to the distance from the mammary teats to the midline.

Fig. 9c: The skin flap is swung caudally to cover the defect, ensuring that thebase is not kinked. The donor site is closed routinely. Note the active suctiondrain.