Reconstruction of Wounds on the Distal Limbs

Introduction

Wounds on distal limbs are often challenging for the advanced soft tissue surgeon because of limited supply of soft tissue in the area. Most wounds will be traumatic in origin and should be treated appropriately before the reconstruction technique is attempted. Because there is no major anatomic difference between the front and hind distal limbs, these are treated identically.

Small Wounds

Small wounds can be treated by primary closure, if there is not excessive wound tension. Tension should be checked in full range of motion of the foot. Simple tension-relieving techniques, as described, allow closure of moderately sized wounds, but for larger wounds additional techniques are necessary. The use of small suture material will decrease excessive scar formation associated with large sutures.

Large Wounds

Most large wounds will need additional reconstruction techniques to prevent excessive tension on the suture line. Many reconstruction techniques have been described of which the toe-fillet technique, the reversed saphenous and the mesh graft are a couple of examples.

Toe Fillet Technique

Footpad injuries can occur as a consequence of lacerations, degloving injuries, abrasion, avulsion, burns and tumours. Because of the weight-bearing function of the footpad, complications may develop during wound healing. Degloving or crushing injuries to the paw may cause the paw to become non-functional. Indoor cats and small dogs that walk only on carpet may function acceptably with skin grafts that do not include footpads. However, in most cases replacement of the metacarpal or metatarsal pad is necessary. Replacement of pad may be achieved by transposing adjacent pads or by microneurovascular free pad transfer. Pad transfer should not be performed in cases where pad injury is caused by tendon malfunction.

The toe fillet technique is indicated for the management of partial injuries to the metacarpal/metatarsal pad or as a replacement for the pad when it has been completely lost. The principle of this technique is the removal of the proximal, middle and distal phalanges in order to use the distal pad to fill a defect in the metacarpal/metatarsal pad. The bony phalanges can be removed via a plantar/palmar or via a dorsal incision.

Step by Step: Toe Fillet Flap (Palmar/Plantar Technique)

1.  Select the digit nearest the defect (usually the second or fifth digit)

2.  Remove the proximal, middle and distal phalanges by incising the joint capsule and ligament attachments to the bone. Use blunt dissection to remove the bone from the surrounding soft tissue, making sure the blood supply remains intact.

3.  The surface and edge of the pad defect are debrided.

4.  Fold back the digital fillet to fill the defect.

5.  Suture the edges of the pad to the edges of the defect using 3-0 monofilament nonabsorbable suture material.

Toe Fillet Flap (Dorsal Technique)

1.  Make a longitudinal incision on the dorsal aspect of the digit.

2.  Remove the phalanges of the digit as described in the palmar/plantar technique.

3.  Close the skin with simple interrupted sutures of 3-0 nonabsorbable monofilament sutures (leaving an opening for drainage where the nail was removed).

4.  Make an incision between the wound and the edge of the metacarpal/metatarsal pad and perform the rest of the flap transfer as described in the metacarpal/ metatarsal technique.

Figure 1. Toe fillet flap technique

Aftercare

Routinely a bandage is applied after reconstruction of distal limb wounds. The bandage consists of a padded material in combination with an elastic protective outer surface material (such as Vetrap). Sufficient pain medication can be combined with broad-spectrum antibiotic therapy if necessary. Penrose drains are routinely used in skin reconstruction techniques, such as the toe fillet technique. The normal size Penrose may be adapted to the size of the flap.

Mesh Grafts

Introduction

The mesh graft is a nonvascularised skin flap that uses skin from another part of the body, which is transferred to the recipient defect side. Because of the nonvascularised nature of the flap, extreme care should be taken in fast and atraumatic harvesting and attachment of the flap. This requires two surgical teams. One to prepare the wound bed and one harvesting the flap and closing the donor defect. Teamwork is of the essence.

Types of Mesh Grafts

There are two major types of mesh grafts, the full- and partial-thickness mesh graft. Partial-thickness mesh grafts are often obtained using electrically operated mechanical dermatomes. Full-thickness grafts are made using the scalpel blade as described here. Full-thickness grafts have the advantage of better cosmetic end results (especially hair growth) above partial-thickness grafts. Partial-thickness grafts have a better chance of taking and the donor sites do not need to be sutured after the harvest.

Wound Bed Preparation

The wound bed needs to be prepared adequately to be able to receive the mesh graft. Preparation includes:

• Removing wound fluid, crusts, dead tissue and possible foreign bodies
• Inspecting the epithelial borders and, if necessary, cleaning up the wound edges
• Coagulation of possible bleeders
• Removing the top layer of the granulation tissue (if necessary)

The recipient side should be covered with a saline-soaked sponge to prevent desiccation while the donor side is prepared.

Donor Side Preparation

The donor side should be carefully selected. It should have enough skin left over after the removal of the donor graft to close the defect. Also attention should be directed to the growth pattern and colour of the hairs to be able to achieve the most acceptable cosmetic results. Often, an impression is made of the recipient bed to estimate the size of the donor bed. The graft will expand significantly in correlation with the number of slits (or meshes) that are made in the graft. Using a non-meshed graft is discouraged. The mesh prevents fluid build-up under the graft. A seroma will significantly decrease the take (acceptance) of the graft.

Technique

It is important to keep the graft moistened during the complete procedure. The technique of a mesh graft is as follows:

• Prepare the site aseptically
• Use a skin marker to determine the margins of the graft
• Incise the skin along the drawn line
• Start at the bottom of the graft and elevate only the skin from the wound bed. The panniculus muscle is not incorporated into the graft.
• Suture the edges of the graft to a sterilised roll of bandage material (such as Vetwrap form 3M)
• Use the roll to put tension on the graft and lift it up from the donor bed.
• An eleven blade should be used to remove as much subcutis from the graft as possible (you should be able to see the hair follicles)
• Slowly roll the graft over the bandage material
• Attach the graft with a few sutures to the bandage material
• Remove the complete graft and free it from the subcutaneous fat
• Use an eleven blade to make the mesh (slits) in the graft. The distance of the slits should be less than a cm and not in an even row but alternate between rows (see picture)
• Remove the graft from the bandage roll
• Place the graft as soon as possible on the prepared recipient side.
• Suture or staple the edges of the graft to the recipient side. Sutures are not necessary inside the graft edges.

After Care

This is the most difficult part of the procedure. A well-padded, non-stick bandage that is able to absorb excess wound fluid should be applied and not removed for 3–5 days. Meanwhile, it needs to be kept as clean and dry as possible. In this period, plasmatic imbibition will take place and nurture the graft and vessels will be able to reconnect. After this, very careful bandage changes will be necessary. The graft will adhere in 7–14 days and epithelialisation of the slits will take place within a month.

Absolute cage rest is essential during the first 10 days. Casts and splints are only used when other means of immobilisation (such as a Robert Jones bandage) are not possible.

References

1.  Swaim SF, Henderson RA. Small Animal Wound Management. 2nd ed. Philadelphia: Williams & Wilkins; 1997:143–275.

2.  Pavletic MM. The integument. In: Slatter D, ed. Textbook of Small Animal Surgery. 3rd ed. Saunders; 2007.

3.  Kirpensteijn J, ter Haar G. Reconstructive Surgery and Wound Management in the Dog and Cat. Manson Publishing/The Veterinary Press; 2013 (ISBN: 978-1-84076-163-4).

4.  Pavletic MM, et al. Reverse saphenous conduit flap in the dog. J Am Vet Med Assoc. 1983;182(4):380–9.