reconstruction in oncologic surgeryLaurent Findji DMV, MS, MRCVS, Diplomate ECVSVRCC Veterinary Referrals, Essex, United Kingdom

It is essential for oncologic surgeons to have a deep knowledge of reconstruction technique. Indeed, limitations in the ability to reconstruct a wound should not lead to insufficiently wide resections. The greater the reconstruction abilities of the surgeon, the more comfortable he or she will be administering the appropriate dose of surgery in the face of a large or awkwardly located tumour.

Reconstructive surgery is an extensive subset of surgical science. It is presented exhaustively in a number of textbooks1-3. Only basic notions and particular points pertaining to oncologic surgery can be discussed here.

Vascular anatomy of the skin

In dogs and cats, the skin is vascularised by 3 plexuses: the subpapillary, cutaneous and subdermal plexuses. The two most superficial plexuses depend on the subdermal plexus, which is therefore the most important to preserve. This plexus lies in depth of the hypodermis. In regions of the body where a panniculus muscle is present (trunk, neck), the subdermal plexus runs immediately deeply and superficially to it. As a practical consequence, when the skin is undermined for primary closure or performance of a skin flap, it must be elevated in depth of the panniculus muscle. In areas where no such muscle is present, the skin must be elevated as close as possible from the underlying fascial or muscular plane.

Figure 1: Vascular anatomy of the skin(a: epidermis; b: dermis; c: panniculus muscle; d: squelettal muscle; 1: subpapillary plexus; 2: cutaneous plexus; 3: subdermal plexus; 4: hypodermis; arrow: direct cutaneous artery)

Wound closure optionsSimple closure

Wound closure may be primary (immediate), delayed primary (before formation of granulation tissue) or secondary (after formation of granulation tissue). Delayed primary and secondary closures are recommended by some surgeons when margin status is uncertain after tumour removal4: the wound is managed as an open wound for a few days while pathology results and margin assessment are pending. When the margins are known to be free of tumour, the wound is closed surgically using any available technique (simple closure, skin flap, skin graft). Several techniques (tension-relieving sutures and incisions, plasties) are available to achieve wound closure when simple closure is not possible. Alternatively, the wound may be left to heal by second intention.

Skin flaps

Skin flaps are either subdermal (relying on the subdermal vascular plexus) or axial (relying on a direct cutaneous artery).

Subdermal flaps are sometimes referred to as “random” flaps, as they rely on the random subdermal plexus to vascularise the elevated skin. This means that these flaps can be harvested in any location and direction. However, the perfusion pressure of the elevated skin has to be estimated as an empirical statistical notion, as the potential presence and direction of direct cutaneous arteries supplying the elevated skin are unknown (Figure 2). As a consequence, these flaps can only be elevated on a limited length, and their base need to be at least as wide as their free end. As an empirical rule, subdermal flaps should only be 1.5 to 2 times longer than they are wide.

Figure 2: Vascularisation subdermal flaps

Subdermal flaps can either be local or distant.

Local flaps include advancement (Figure 3; Figure 4), rotation (Figure 5), transposition (Figure 6) and interpolation flaps (Figure 7). These flaps are elevated from skin adjacent to the wound.

Figure 3: Advancement flap

Figure 4: Double advancement flap

Figure 5: Rotation flap

Figure 6: Transposition flap

Figure 7: Interpolation flap

Distant flaps include hinge and pouch flaps, in which a monopedicular or bipedicular subdermal flap is elevated on the lateral aspect of the abdomen or thorax and used to cover a wound on the distal portion of a limb brought to the flap (Figure 8).

Figure 8: Principle of distant flaps

Axial pattern flaps are determined by the area of skin vascularised by a major direct cutaneous artery (angiosome), after which it is named (Figure 9a). Many direct cutaneous arteries which can be used to perform axial flaps have been described (Figure 10). Provided this artery is preserved, such flaps are more robust and survive on greater lengths compared to equivalent subdermal flaps. They can even be islanded, i.e. entirely cut out from the donor site apart from their vascular pedicle (Figure 9b). However, axial flaps cannot be elevated in any direction: their design has to follow the description of the cutaneous area vascularised by the chosen direct cutaneous artery. The most commonly used axial flaps include the caudal superficial epigastric, thoracodorsal, omocervical, deep circumflex iliac and caudal auricular flaps.

a b

Figure 9: Vascularisation of axial flaps (a). Island flap (b)

Figure 10: Main direct cutaneous arteries of the dog

Skin flaps, either subdermal or axial, are transposed with their own vascularisation and can survive on poorly vascular beds or over cavities.

Skin grafts

Skin grafts consist of transposing free portions of partial-thickness or full-thickness skin to a wound. The transposed skin is therefore no longer perfused and relies on the development of a neovascularisation from the receiving bed for survival. The receiving bed must therefore be healthy and well-vascularised, so that sufficient neovascularisation can develop from it. In veterinary surgery full-thickness grafts, harvested from the ventrolateral portions of the trunk, are most commonly used. Different forms of grafts exist: meshed, unmeshed, pinch, punch and strip grafts. Meshed and unmeshed grafts use a single skin portion to cover the recipient bed. Numerous slit incisions are made in meshed grafts. These incisions allow postoperative drainage which favours graft adhesion and survival. In addition, meshed grafts can be expanded more easily than unmeshed grafts. Pinch and punch grafts consist of a number of few-millimetre-wide portions of skin placed evenly apart in the recipient bed. Pinch grafts are harvested with a scalpel, whereas punch grafts are harvested with a biopsy punch. Matching-size holes or pockets are created in the granulation tissue of the recipient bed to accommodate the grafts. The main advantages of these grafts are that they are easy to perform, allow very good drainage of the wound and withstand infection better than other types of graft. However, the resulting cosmetic aspect is rather poor.Strip grafts consist of several strips of skin placed parallel in the recipient bed. Matching-size strips of granulation tissue are excised to accommodate the grafts. Like pinch and punch grafts, these grafts allow good drainage but often lead to poor cosmetic results.

Wound closure decision making

Wound closure options depend on the location, age, type, severity and contamination of the wound. In small animals, the great skin elasticity allows primary or secondary closure of many wounds. If not, the wound can either be left to heal by second intention or more advanced reconstructive techniques be used to achieve wound closure. Second intention healing may seem financially attractive at first, but it is often long to complete, requires numerous dressing/bandages and regular follow-up, which may eventually cost more than a reconstructive surgery. In addition, it often leaves an epithelium of poor quality and cosmetics, and occasionally results in skin contractures.Skin flaps and grafts can be used to avoid these drawbacks.

In all cases, the surgeon must opt for the technique which, in his hands, is the safest, simplest and cheapest. The technique with the greatest chances of success must be chosen in priority. If several techniques have equal chances of success, the simplest must be preferred. Lastly, the financial aspect may also be accounted for and the cheapest method among the most likely to be successful may also be chosen.

Thoracic and abdominal wall reconstruction

It is not uncommon in oncologic surgery that full-thickness resection of body walls be necessary. When resulting defects are small enough, they can generally be reconstructed without any foreign material, by a combination of muscle advancement and transposition. When the defects are too large or surrounding muscles are insufficient (either because of their normal scarcity in the region or as a result of their excision during the oncological resection), reconstruction using foreign material such as meshes can be necessary. In addition, when a large portion of the thoracic wall is resected (i.e. more than 5 or 6 ribs), it may be necessary to use a mechanically resistant reconstruction to avoid physiological disturbances resulting from impaired expansion of the thorax during inspiration.

Defects in the abdominal wall can often be closed by simple advancement of the remaining abdominal muscles. However, when this is not possible without excessive tension, or when it is feared that the reduction in the volume of the abdominal cavity may expose to the risk of abdominal compartment syndrome, meshes can be used to fill defects in the abdominal wall.

Defects in the thoracic wall may be closed by muscle transposition (e.g. latissimus dorsi transposition) or by implantation of prosthetic material, such as meshes5. When the defect involves the few most caudal ribs, the thoracic cavity may be reconstructed by diaphragmatic advancement. With this technique, the remaining thoracic wall is rigid and the defect is transposed from the thoracic wall to the abdominal wall, which is reconstructed by either muscle transposition or implantation of prosthetic material. When the distance over which the diaphragm is advanced is long enough to prevent the ipsilateral caudal lung lobe from expanding sufficiently, it may be necessary to resect this lung lobe to prevent shunting and postoperative oxygenation problems.

References

1.Pavletic MM. Atlas of small animal wound management and reconstructive surgery. Oxford: Wiley-Blackwell, 2010.

2.Williams J, Moores A. BSAVA manual of canine and feline wound management and reconstruction. Quedgeley: British Small Animal Veterinary Association, 2009.

3.Slatter DH. Textbook of small animal surgery. Philadelphia, PA ; [Great Britain]: Saunders, 2003.

4.Liptak J. The Principles of Surgical Oncology: Surgery and Multimodality Therapy. Compendium Continuing Education for Veterinarians. 2009;31: 14 p.

5.Liptak JM, Dernell WS, Rizzo SA, Monteith GJ, Kamstock DA, Withrow SJ. Reconstruction of chest wall defects after rib tumor resection: a comparison of autogenous, prosthetic, and composite techniques in 44 dogs. Veterinary Surgery. 2008;37: 479-487.

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RECONSTRUCTI

O

N IN ONCOLOGIC

SURGERY

Laurent Findji DMV, MS, MRCVS, Diplomate ECV

S

VRCC Veterinary Referrals, Ess

ex, United Kingdom

It is essential for oncologic surgeons to have a deep knowledge of reconstruction technique.

Indeed

, limitations

in the ability to reconstruct a wound should not lead to insufficiently wide resections. The greater the

reconstruction abilities of the surgeo

n, the more comfortable he or she will be administering the appropriate

dose of surgery in the face of a large or awkwardly located tumour.

Reconstructive surgery is an extensive subset of

surgical science.

It is present

ed exhaustively

in a

number of

textbooks

1

-

3

.

Only basic notions

and particular points pertaining to oncologi

c surgery can

be discussed here.

Vascular anatomy of the skin

In dogs and cats, the skin is vascularised by 3 plexuses: the

subpapillary, cutaneous and subdermal plexuses.

The two most superficial plexuses depend on the subdermal plexus, which is the

refore the most important to

preserve. This plexus lies in depth of the hypodermis. In regions of the body where a panniculus muscle is

present (trunk, neck), the subdermal plexus runs immediately deeply and superficially to it. As a practical

consequence,

when the skin is undermined for primary closure or performance of a skin flap, it must be

elevated in depth of the panniculus muscle. In areas where no such muscle is present, the skin must be

elevated as close as possible from the underlying fascial or m

uscular plane.

Figure

1

: Vascular anatomy of the skin

(a: epidermis; b: dermis; c: panniculus muscle; d: squelettal muscle; 1: subpapillary plexus;

2: cutaneous plexus; 3: subdermal plexus; 4: hypodermis; arrow: direct cutaneous

artery)

Wound closure options

Simple closure

Wound closure may be primary (immediate), delayed primary (before formation of granulation tissue) or

secondary (after formation of granulation tissue).

Delayed primary and secondary closures are recommended

by

some surgeons when margin status is uncertain after tumour removal

4

: the wound is managed as an open

wound for a few days while pathology results and margin assessment are pending. When the margins are

L. Findji – Reconstruction in oncologic surgery - AMVAC 2013 1/1

RECONSTRUCTION IN ONCOLOGIC SURGERY

Laurent Findji DMV, MS, MRCVS, Diplomate ECVS

VRCC Veterinary Referrals, Essex, United Kingdom

It is essential for oncologic surgeons to have a deep knowledge of reconstruction technique. Indeed, limitations

in the ability to reconstruct a wound should not lead to insufficiently wide resections. The greater the

reconstruction abilities of the surgeon, the more comfortable he or she will be administering the appropriate

dose of surgery in the face of a large or awkwardly located tumour.

Reconstructive surgery is an extensive subset of surgical science. It is presented exhaustively in a number of

textbooks

1-3

. Only basic notions and particular points pertaining to oncologic surgery can be discussed here.

Vascular anatomy of the skin

In dogs and cats, the skin is vascularised by 3 plexuses: the subpapillary, cutaneous and subdermal plexuses.

The two most superficial plexuses depend on the subdermal plexus, which is therefore the most important to

preserve. This plexus lies in depth of the hypodermis. In regions of the body where a panniculus muscle is

present (trunk, neck), the subdermal plexus runs immediately deeply and superficially to it. As a practical

consequence, when the skin is undermined for primary closure or performance of a skin flap, it must be

elevated in depth of the panniculus muscle. In areas where no such muscle is present, the skin must be

elevated as close as possible from the underlying fascial or muscular plane.

Figure 1: Vascular anatomy of the skin

(a: epidermis; b: dermis; c: panniculus muscle; d: squelettal muscle; 1: subpapillary plexus;

2: cutaneous plexus; 3: subdermal plexus; 4: hypodermis; arrow: direct cutaneous artery)

Wound closure options

Simple closure

Wound closure may be primary (immediate), delayed primary (before formation of granulation tissue) or

secondary (after formation of granulation tissue). Delayed primary and secondary closures are recommended

by some surgeons when margin status is uncertain after tumour removal

4

: the wound is managed as an open

wound for a few days while pathology results and margin assessment are pending. When the margins are