The Effects of Skin Graft Thickness on Graft Viability and Change in Original Graft Area in Dogs

The viability and change in original graft area of full thickness grafts (FTG) and split thickness skin grafts (STG) placed on fresh and granulating recipient beds were evaluated. Two 6 × 6 cm skin grafts were placed on each side of the trunk in ten dogs. Grafting procedures included FTG and STG on fresh and granulating wounds. Graft viability was determined on the 10th postoperative day by visual inspection. The change in original graft area was evaluated by comparing the original surface area of the grafts with the surface areas of the grafts at 10, 30, 60, and 90 days after surgery. The means graft viability for FTG and STG on fresh beds was 81% and 55%, respectively. FTG and STG on granulating beds had a mean graft viability of 58% and 47%, respectively. The mean percentage of original graft area at 90 days for FTG and STG on fresh beds was 82% and 97%, respectively. FTG and STG on granulating beds had an overall percentage of original graft area of 105% and 130%, respectively. There were no statistical differences found when comparing FTG with STG placed on fresh beds or granulating beds. However, the general trend indicated that FTG had a greater percentage of viability and contracted more than STG in dogs. This is contrary to previous findings.     

Effects of split-thickness and full-thickness skin grafts on secondary graft contraction in horses.

Full-thickness, circular (4-cm diameter) cutaneous wounds were created on the metacarpi and metatarsi of 6 horses. Immediately after wounding, 1 wound on each horse received a meshed, split-thickness skin graft (0.64 mm) obtained from the ventrolateral aspect of the horse's thorax by use of a pneumatic dermatome, whereas a second wound received a meshed, full-thickness skin graft obtained from the pectoral area. In addition, sections of split-thickness and full-thickness grafts were refrigerated in a solution of McCoy's 5A medium, to which equine serum (10%) and gentamicin sulfate solution (16 mg/dl) were added. Ten days after wounding, 1 granulating wound on each horse was grafted with a stored, meshed, split-thickness graft, and 1 granulating wound on each horse was grafted with a stored, meshed, full-thickness graft. Areas of wounds were calculated from photographs taken of wounds on days 1, 5, 10, 15, 20, 25, and 30 after wounding. Time course of contraction was determined by use of a first-order mathematic model of changes in area through time. Rate constants of contraction for fresh or granulating wounds receiving full-thickness grafts did not differ significantly from those for fresh or granulating wounds receiving split-thickness grafts. Rate constants of contraction for grafted fresh wounds, however, were significantly less than those of grafted granulating wounds, regardless of whether a split-thickness or full-thickness graft was applied.     

Wound Drainage from Under Full-thickness Skin Grafts in Dogs Part I. Quantitative Evaluation of Four Techniques

The formation of hematomas or seromas under skin grafts is reported to be the most common cause of graft failure. Several techniques have been developed to prevent fluid accumulation by increasing drainage, but their effectiveness has not been evaluated. In this study, four full-thickness skin grafting procedures were performed on both sides of the chests of 12 dogs, and the amount of wound drainage was quantitated for the first 10 postoperative days. The techniques evaluated were a sheet graft (control), continuous low level suction, piecrust incisions, and nonexpanded mesh graft. Significantly more drainage fluid was removed by continuous low level suction than the other techniques evaluated. Meshing allowed significantly more drainage than the piecrust or sheet grafts but was not as effective as continuous low level suction. Piecrust incisions had no significant effect on wound drainage.     

Treatment of large distal extremity skin wounds with autogenous full-thickness mesh skin grafts in 5 cats

Five cats with large, distal extremity abrasion wounds were treated with an autogenous, full-thickness, mesh skin graft. Survival of the mesh grafts in all five cats was considered between 90 and 100%. Successful grafting requires asepsis, an adequately prepared recipient bed consisting of healthy granulation tissue, proper harvesting and preparation of the graft, meticulous surgical technique and strict postoperative care. Factors that are essential for the survival of skin grafts include good contact between the graft and the recipient bed, normal tension on the sutured graft, strict immobilization after grafting and prevention of accumulation of blood or serum under the graft. Meshing the graft provides more graft flexibility over uneven surfaces and allows adequate drainage. In contrast to previous proposals, the authors recommend no bandage change before the fourth day after grafting. Full-thickness mesh skin grafting can be used to successfully treat large distal skin wounds in cats.     

The modified Meek technique as a novel method for skin grafting in horses: evaluation of acceptance, wound contraction and closure in chronic wounds

REASONS FOR PERFORMING STUDY: The acceptance of skin grafts in horses is unpredictable and the final cosmetic result can be disappointing. Besides movement and infection, graft failure is often caused by chronic inflammation, inherently present during second intention healing of limb wounds in horses. In human burns affected by infection and inflammation, the acceptance of the island skin grafts of the modified Meek technique appeared to be better than meshed sheet skin grafts. HYPOTHESIS: The percentage take of Meek micrografts is higher than of other techniques; and rates of both wound contraction and epithelialisation are increased. METHODS: Large traumatic limb wounds of 13 horses healing by second intention were grafted using the modified Meek technique. Photographs of the wounds were taken at set intervals. Wound areas, and areas of acceptance and rejection were determined using a digital image post processor (Scion Image). The percentages of take, wound contraction and epithelialisation were calculated. RESULTS: The initial mean wound area was 7500 mm2. Graft acceptance was mean +/- s.d. 93.7 +/- 5.9%. Wound closure was due to contraction (55.2 +/- 11.1%) and epithelialisation (44.8 +/- 11.1%) and resulted in a 96.7 +/- 3.6% reduction of the initial wound area 29.1 +/- 6 days after grafting. All wounds showed functional and cosmetic healing. CONCLUSIONS: The method for skin grafting in horses achieved higher percentages of take than reported previously and consistent cosmetic and functional results. The grafts increased not only the rate of epithelialisation but also had a strong positive effect on wound contraction, resulting in rapid closure and smaller scars. POTENTIAL RELEVANCE: The modified Meek technique proved to be a novel technique for skin grafting equine wounds in clinical practice, which can be performed easily. The molecular background of the increase of wound contraction by the grafts may provide a clue in the search for medicinal stimulation of wound contraction during second intention healing.     

Tunnel grafting for wound repair in horses: a novel technique in graft production and placement

There are several skin grafting methods described in the human and animal literature. Currently, there are five types of free grafts used in horses: pinch and punch grafts, split and full-thickness sheet or mesh grafts and tunnel grafts. Published methods of tunnel grafting describe the use of alligator forceps. The alligator forceps create a poor tunnel and are excessively traumatic to the granulation bed. This technique utilised a 13G Jamshidi needle that was placed across the granulation bed and created a uniform tunnel. The Jamshidi needle was atraumatic to the granulation bed increasing the opportunity for graft survival. A twin bladed scalpel allowed for the quick creation of uniform width grafts. Removal of the overlying tunnel ‘roof’ took place 5–14 days later to allow graft expansion. This case series included five horses with distal limb wounds and one with a wither injury. Four horses required general anaesthesia for graft placement and three required general anaesthesia for the removal of the tunnel roof. The acceptance of the grafts varied from 70% to 100%. Graft expansion to cover the granulation tissue took 2–5 months. This case series demonstrates that this technique of graft production and placement is an easy method for achieving successful skin grafting. Compared to other graft types, tunnel grafts are more readily accepted. Cosmetic and functional results achieved are better than those with pinch and punch grafts. Tunnel grafting does not require expensive equipment or advanced training, and in some cases can be performed under standing sedation.     

Treatment of equine leg wounds using skin grafts: Thirty-five cases, 1975-1988

A retrospective study was conducted on 35 equine patients with lower leg wounds that were managed utilizing skin graft procedures. Two pinch graft, five punch graft, seven tunnel graft, eight split-thickness mesh graft and thirteen full-thickness mesh expansion graft procedures were performed in the initial treatment. The average wound size was 188 cm². Twentyfour cases had pregrafting complications: 10 wounds developed sequestra; three wounds were grossly contaminated and infected; and 11 cases developed granulation tissue complications prior to grafting. Graft failure following the initial procedure was seen in 12 cases and occurred with all techniques except pinch grafting. Graft failure was often attributable to poor quality of granulation tissue as well as anatomic site, especially the dorsal surface of the tarsus. An average of two additional grafting procedures was required to successfully treat initial failures. Pinch grafts took the longest time to epithelialize (70 days), followed by punch grafts (47 days). Both were similar in terms of being the least durable and least cosmetically acceptable of all techniques used. Split-thickness and full-thickness mesh expansion grafts were technically the most difficult, but showed the most rapid epithelialization (28 days), greatest durability, and the best cosmetic appearance. Tunnel grafts provided a practical technique for grafting cases which were either not suited for, or which had failed with, mesh expansion grafts.     

Wound Drainage from Under Full-thickness Skin Grafts in Dogs Part II. Effect on Cosmetic Appearance

Four skin grafting procedures were performed on both sides of the chests of 12 dogs to evaluate the effect of wound drainage on the survival and cosmetic appearance of the grafts. The techniques evaluated were a sheet graft, (control), continuous low level suction, piecrust incisions, and nonexpanded mesh graft. Graft viability was assessed on the 10th postoperative day by visual inspection. The mean survival rate for all grafts was 90%. No significant difference between graft types was observed.
Hair growth on each graft was assessed 3 months postoperatively as "normal" (resembled that on the surrounding skin), "moderate" (thickness of hair growth was less than normal but would nearly conceal the underlying skin), "sparse" (a few hairs were present and the skin below was easily visible), and "none" (no hair growth). No statistical differences in categories of hair growth were detected within types or between types of grafts. Hair growth also was assessed as "acceptable" (those areas having normal and moderate hair growth) and "nonacceptable" (hair growth sparse or none). No difference between graft types was noted. All types exhibited a significantly greater area of acceptable than nonacceptable hair growth.     

Mesh skin grafting

Mesh grafts are split-thickness or full-thickness skin grafts in which parallel rows of staggered slits have been cut. The mesh incisions allow the graft to be expanded to cover large defects, provide a route for drainage of blood or serum from under the graft, and increase the flexibility of the graft so that it can conform to uneven recipient beds. Meshing can be accomplished using a no. 11 scalpel blade or a special meshing machine. The use of unexpanded full-thickness mesh grafts is recommended because their cosmetic appearance equals that of sheet grafts, but the mesh incisions still allow drainage of blood and/or serum from under the graft. This technique has been very successful, with 90 to 100 per cent "take" when the grafts have been applied on healthy granulation beds.     

Free skin grafting for treatment of distal limb skin defects in cats

The technique and results of free skin grafts have been described in dogs, horses, rabbits, goats and mice. The procedure in cats is, however, described only indirectly in papers relating to dogs. A standard technique has been developed by the authors for use in cats, and is reported for 17 grafts in 16 cats with traumatic injury to the legs resulting in large areas of skin loss. This paper describes the preparation of the wound for grafting, the harvesting of the graft, graft placement, postoperative care and the results of the application of this technique. The success rate in this series of cases was high. This was attributed to proper preparation of the recipient site, collection of the graft and postoperative bandaging. The results suggest that the success rate of free skin grafts in cats is considerably higher than that achieved by the present authors in dogs, and reported for dogs by other surgeons in the literature.     

Effects of hyperbaric oxygen on full-thickness meshed sheet skin grafts applied to fresh and granulating wounds in horses

OBJECTIVE: To determine the effects of hyperbaric oxygen therapy (HBOT) on full-thickness skin grafts applied to fresh and granulating wounds of horses. ANIMALS: 6 horses. PROCEDURES: On day 0, two 4-cm-diameter circular sections of full-thickness skin were removed from each of 2 randomly selected limbs of each horse, and two 4-cm-diameter circular skin grafts were harvested from the pectoral region. A skin graft was applied to 1 randomly selected wound on each limb, leaving the 2 nongrafted wounds to heal by second intention. On day 7, 2 grafts were harvested from the pectoral region and applied to the granulating wounds, and wounds grafted on day 0 were biopsied. On day 14, 1 wound was created on each of the 2 unwounded limbs, and the wounds that were grafted on day 7 were biopsied. All 4 ungrafted wounds (ie, 2 fresh wounds and 2 wounds with 1-week-old granulation beds) were grafted. The horses then received HBOT for 1 hour daily at 23 PSI for 7 days. On day 21, the grafts applied on day 14 were biopsied. RESULTS: Histologic examination of biopsy specimens revealed that grafts treated with HBOT developed less granulation tissue, edema, and neovascularization, but more inflammation. The superficial portion of the graft was also less viable than the superficial portion of those not treated with HBOT. CONCLUSIONS AND CLINICAL RELEVANCE: The use of HBOT after full-thickness skin grafting of uncompromised fresh and granulating wounds of horses is not indicated.     

Autologous, split skin transplantation on the lower limbs of horses.

The skin grafting experiments were carried out on the cannon regions of horses to throw light on four matters relating to split skin transplantation. They were: The thickness of donor split skin that would provide good wound cover and still leave adequate tissue to permit uneventful healing at the donor site; whether split skin grafts were more readily accepted on fresh than on granulating wounds; the size of wounds that would benefit from grafting; and the maximum size of graft that would be readily accepted. The findings were: Split skin grafts 0.76 mm thickness gave the best results although grafts 0.63 mm thickness were satisfactory; split skin grafts were accepted more readily on fresh wounds than on granulating tissue; wounds which exceeded 1/10th of the skin area on the cannon region justified grafting; the upper limit in size was not established as the largest grafts used were more readily accepted than smaller grafts.     

Comparison of full- and partial-thickness autogenous skin transplantation in dogs: a pilot study.

Thin partial-thickness (0.063 cm), medium (0.127 cm) partial-thickness, and full-thickness skin autografts were transplanted to surgically created granulating foreleg wounds of dogs. Thin partial-thickness grafts had an 89% survival, medium partial-thickness grafts had 47% survival, and full-thickness grafts had a 58% survival. Of the successful grafts, only the thin partial-thickness grafts did not grow adequate hair after transplantation.     

Regeneration of wool follicles in autografts of sheep skin.

Three experiments involving six sheep were carried out at three different times in the annual wool growth cycle. Forty-eight full-thickness fitted autografts were sampled 2 h, 6 h, 24 h, 48 h, 3, 4, 5, 7, 9, 11, 14, 21 and 28 days after grafting. The histopathology of the grafts is described. Individual variation in 'take' was probably related to the speed with which vascular integrity was reestablished between graft and bed. Delayed acceptance caused the death of pilosebaceous units. In a successful graft, wool follicle regeneration appears to occur in three main ways: (1) an inactive follicle regenerates from the dormant bulb at about seven days, (2) follicles that were active at the time of grafting have first to form a papilla stalk, and such follicles did not become active until 11 days, (3) sometimes one or more outgrowths appeared at higher levels suggesting follicle regeneration by branching. In addition there were a few instances of de novo downgrowth of follicle plugs from the epidermis. Wool growth on the graft therefore arises almost entirely from the reorganisation of preexisting follicles.     

Microvascular transplantation of a free omental graft to the distal extremity in dogs

OBJECTIVE: To assess the survival of a free omental graft applied to an experimentally created wound on the distal extremity in dogs. STUDY DESIGN: A free omental graft was evaluated as a primary method of treatment for dogs with distal extremity wounds in an experimental model. ANIMALS OR SAMPLE POPULATION: Five adult intact female mixed breed dogs weighing 21.8 kg to 25.0 kg. METHODS: A free omental graft was harvested from the abdomen and transferred to a wound bed overlying the medial aspect of the tibia. A microvascular anastomosis was performed between the graft vessels and vessels at the recipient site. Daily clinical assessment of graft viability was performed. Angiography and 99mTechnetium labeled macroaggregated albumin (99mTc MAA) scintigraphic perfusion scans were performed on either day 4, 5, or 7. Postmortem collection of tissues for histopathologic analysis was performed immediately after imaging. Total operative time and graft ischemia time were evaluated for effects on graft survival. RESULTS: Two of seven grafts survived to the end of the study, three of seven grafts failed because of ischemia, and two of seven grafts failed because of self-trauma. There was no clinically significant morbidity associated with the abdominal portion of the procedure. Because of the small number of surviving grafts, the effects of operative time and graft ischemia time could not be statistically evaluated. CONCLUSIONS: Microvascular transplantation of a free omental graft can result in a viable tissue covering of a distal extremity wound, however, the failure rate is unacceptably high. CLINICAL RELEVANCE: A free omental graft may not have sufficient durability to be an acceptable wound covering by itself. Further studies combining omentum with a skin graft or other tissues may result in a clinically useful technique.     

Skin grafts

Skin grafting is a method to reconstruct the skin covering on areas of the body where there are defects and insufficient surrounding skin for advancement or for creation of flaps. Grafts are classified according to their host-donor relationship and by their thickness. Autogenous grafts, taken from one area of the body and applied to another area, are the type of graft used most often clinically. Pieces of skin are taken from one area of the body, prepared and applied over a defect that has also been properly prepared to accept the graft. The defect to which a graft is applied must be a healthy bed of granulation tissue or tissue that is vascular enough to produce a bed of granulation tissue. In its new location, the graft will develop a new blood supply and attachment to underlying tissues. This is accomplished as the graft undergoes the processes of fibrinous adherence, plasmatic imbibition, inoculation, and new vessel ingrowth. The types of grafts described in this chapter are split-thickness, full-thickness, seed, strip, and stamp grafts. Each of these graft types must be prepared using certain techniques, and each one has its inherent advantages and disadvantages. Split-thickness grafts may require considerable skill and/or expensive equipment to perform. Although they "take" better than full-thickness grafts, they are usually less cosmetically attractive. Full-thickness grafts require no special skill or expensive equipment, and their cosmetic appearance is better than that of split-thickness grafts, but they do not take as well as split-thickness grafts. Seed and strip grafts are easily accomplished and require no special instruments; however, their cosmetic appearance is not good. Stamp grafts have some of the properties associated with split-thickness grafts as well as those of seed and strip grafts, since they combine features of both.     

Complications and outcome after thoracodorsal axial pattern flap reconstruction of forelimb skin defects in 10 dogs, 1989-2001

OBJECTIVE: To determine (1) the frequency and extent of complications associated with thoracodorsal axial pattern flap reconstruction of forelimb skin defects in dogs and (2) outcome after treatment of such complications. STUDY DESIGN: Retrospective clinical study. SAMPLE POPULATION: Ten dogs. METHODS: Medical records for 10 dogs that had a thoracodorsal axial pattern skin flap reconstruction of a forelimb skin defect were reviewed. RESULTS: Three dogs had complete flap survival. Partial necrosis of the distal flap, ranging from an estimated 2% to 53% (mean, 21%) of the flap surface area, occurred in 7 dogs. Six dogs required surgical management of the skin necrosis, resulting in successful resolution in 5 dogs, whereas, in 2 dogs, the wound healed by second intention. Positive bacterial cultures were obtained from 3 dogs with distal flap necrosis. Seroma formation was noted in 2 dogs; the entire flap survived in 1 dog, whereas the second dog developed distal flap necrosis. Edema and bruising of the distal portion of the flap were noted in 8 dogs; distal flap necrosis subsequently developed in 7 dogs. Partial incisional dehiscence, which healed by second intention, occurred in 2 dogs. Of 6 owners available for follow-up, all were satisfied with the functional outcome, but 1 owner was not satisfied with the cosmetic appearance. CONCLUSIONS: Partial flap necrosis was a frequent complication of thoracodorsal axial pattern flap reconstruction of forelimb skin defects and required additional wound care or surgical intervention to achieve healing. CLINICAL RELEVANCE: Thoracodorsal axial pattern flaps can provide full-thickness skin coverage of extensive skin defects of the forelimb, but owners should be aware of the likelihood of local wound complications.     

Use of an ipsilateral vascularized ulnar transposition autograft for limb-sparing surgery of the distal radius in dogs: an anatomic and clinical study

OBJECTIVE: To develop a surgical technique for using the distal aspect of the ulna as a transposition autograft in a distal radial defect and to assess patency of vascular supply and viability of the distal ulna in a heterotopic position. STUDY DESIGN: Cadaveric study and clinical cases. ANIMALS: Twenty-two normal canine thoracic limbs; 3 dogs with distal radial osteosarcoma. METHODS: The arteries and veins of 12 limbs were injected with latex. Barium sulfate suspension was injected into the brachial artery of 10 other limbs after removal of the distal radius only (n = 2), ulna transposition (UT) (n = 6), or no procedure (n = 2). The distal ulna grafts were then harvested and decalcified in formic acid. The grafts were cut into 3-5 mm transverse sections and radiographed with a nonscreen film system to determine filling of intramedullary vessels with barium suspension. UT was performed in 3 dogs with distal radial osteosarcoma. Bone scintigraphy was performed 2-7 days after surgery to assess viability of the transposed ulna graft. RESULTS: Angiography confirmed patency of the caudal interosseous artery in all but 2 limbs in which the UT technique was performed; however, barium-filled vessels were identified in the medullary cavity of all ulnar grafts. Scintigraphy confirmed graft viability in the 3 dogs, all of which had good to excellent limb function. CONCLUSIONS: The distal aspect of the canine ulna can be used as a vascularized transposition autograft to replace distal radial defects, and viability can be maintained. CLINICAL RELEVANCE: The UT technique appears to be an acceptable limb-sparing technique for dogs with tumors of the distal aspect of the radius.     

Skin grafts and skin flaps in the horse.

Although most equine wounds can be easily treated and heal without consequence, there are many that present special challenges. Skin grafts area valuable part of the veterinarian's armamentarium for treatment of complicated wounds, particularly limb wounds. Attention to preparation of the recipient site and proper aftercare are critical to successful grafting. With better understanding of equine wound and graft physiology and the promise foretold by advances in human skin grafting, the outcome of treatments of difficult equine wounds should continue to improve in the future.     

Evaluation of a free vascularized medial tibial bone graft in dogs

OBJECTIVE: To develop a free vascularized tibial bone graft based on the periosteal saphenous blood supply. STUDY DESIGN: Preliminary anatomic study of medial tibial blood supply. In vivo comparison of a vascularized and avascular tibial bone graft. ANIMALS: Nine canine cadavers; 14 healthy adult dogs that weighed 25 to 32 kg. METHODS: An anatomic study of the vascular supply of the medial aspect of the tibia was performed using the Spalteholz technique. A bone graft consisting of the medial aspect of the tibia was transferred to a mandibular defect as a vascularized graft in 7 dogs and as an avascular graft in 7 dogs. Bone scans were performed to evaluate graft perfusion. Radiographic evaluation of the mandibles and tibias was performed. The dogs were killed after 60 days, five mandibles from each group were examined histologically, and two from each group were evaluated using the Spalteholz technique. RESULTS: The saphenous vascular pedicle provides vascular perfusion to the medial tibial cortex. Bone scans and radiographic evaluations were consistent with viable bone in the vascularized grafts, and nonviable bone in the avascular grafts. Histological examination revealed live, healing bone in vascular grafts and necrotic bone in avascular grafts. Spalteholz evaluation revealed many small arborizing vessels in the vascular grafts and no organized vasculature in the avascular grafts. CONCLUSIONS: The vascularized medial tibial cortical bone graft survived and proceeded to bony union in the mandibular body defect more readily than the avascular graft in this experimental model. CLINICAL RELEVANCE: A vascularized medial tibial bone graft is a suitable free graft for use in reconstructing bone defects in dogs.