Use of Cadaveric Donor Skin to Predict Success of a Definitive Split-thickness Skin Graft in Complicated Wounds

Abstract:   Split-thickness skin grafts (STSG) are used for covering large wound beds. This procedure is sometimes postponed due to a positive culture swab. In those cases, prolonged antibiotic therapy is advised. The present study shows that if a temporary cadaveric donor skin has good take, antibiotic therapy is not necessary and a normal STSG can be performed directly with acceptable results. Methods. Cadaveric donor skin was applied in 35 consecutive patients. If the cadaveric donor skin had a good take (adherence) to the wound bed, the patient was scheduled for a STSG. In cases where the cadaveric donor skin failed to take, the definitive skin graft procedure was postponed. In six consecutive cases the cadaveric donor skin was evaluated for possible pathological changes. Results. In 25 out of 35 patients the cadaveric donor skin had full take. In 22 of these 25 patients a STSG was performed, which led to 91% complete graft take rate. These patients were not treated routinely with antibiotics and if they were treated, surgery was not postponed. Conclusion. Delaying STSG while waiting for swab culture results is not necessary if the cadaveric donor skin has good take 3 days after application; in such cases, the take (attachment) of a STSG in a complicated set of patients is > 90%. The cadaveric donor skin, with positive take, showed more granulocytic influx in the epidermal layer and more vitality than those with no adherence to the wound bed. Vascular in-growth was not noted in any of the cases.   The first time that skin transplantation and grafts were referred to was in the Billings Medical Dictionary from the 1890s.¹ The first written documentation from Gaspare Tagliazocci regarding skin transplantation is even older and dates back to the 1500s.² In the early 1930s and during World War II, split-thickness skin grafting progressed greatly under the influence of James Barrett Brown, a head and neck surgeon (1899–1971). He was the first to use the term split-thickness skin graft (STSG) the way it is used currently.³ Brown popularized the use of allograft skin when he used allogenic skin as a dressing.   Normally in the authors’ hospital if a wound needs STSG, is clinically infected, or if a culture swab shows growth of bacteria, the surgery will be postponed. Usually the patient will be treated with antibiotics and the wound will be given some form of local treatment. The STSG will typically be planned if the subsequent culture swabs showed no treatable bacterial load after administration of antibiotics. This procedure of giving antibiotics and waiting for culture results could easily take up to 2 weeks. When the operation eventually takes place, there is no guarantee that the skin graft will take. Furthermore, while waiting for the surgery to be performed there is always a chance that a new infection will occur. Obviously, the patient will also have to deal with an open wound for a longer period, which might require an even longer hospital stay. Unfortunately, there does not seem to be any other diagnostic tool to predict the success of STSG other than the good sense of the wound care specialist and a non-treatable culture result.   Human cadaveric donor skin can be used as temporary wound coverage. Studies have demonstrated that blood vessels can grow into the donor skin.¹ According to several studies, bacteria in the wound bed may have a negative influence on the take of the cadaveric donor skin or STSG, particularly group A beta-hemolytic streptococci.^4,5   In this study, human cadaveric donor skin used as temporary wound coverage was applied to the wound bed to predict readiness for STSG. The influence of bacteria on the cadaveric donor skin was taken into account. It was the authors’ hypothesis that if the cadaveric donor skin had good take on the wound, it would have subsequent STSG after removing the cadaveric donor skin, thus reducing the time between a “clinically graftable” wound and the definitive STSG without increasing the number of failed grafts. Additionally, the pathological changes of six cadaveric donor skin samples were studied in an effort to understand how the donor skin would interact with the recipient.

Methods

  All patients were treated at the Rijnland Wound Care Centre, which is a department within Rijnland Hospital (Leiderdorp, The Netherlands). This department treats a wide variety of wounds. Patients in this study had wounds as a result of trauma, diabetes, postsurgical infections, and arterial/venous pathology.   The study lasted for 2 years (May 2006–May 2008). Thirty-five (35) consecutive patients who required a STSG were selected. All patients were informed about the procedure and gave written consent. A culture swab was taken from each patient and a human cadaveric donor skin (Euro Skin Bank) was applied and attached to the wound bed with glue (Dermabond®, Ethicon, Somerville, NJ). The cadaveric donor skin was delivered in samples with preservation fluid (glycerol 85%). Preservation of skin in 85% glycerol reduces the risk of bacterial transfer to the recipient and allows an increase in yield of cadaver skin of approximately 10%.⁶ The skin was washed in sterile water to ensure that all preservation fluid had been removed prior to use.   After 3 to 4 days the patients returned for follow up so the authors could evaluate if the cadaveric donor skin was adhering to the underlying wound bed. Adherence was evaluated by removing the donor skin—if the donor skin was removed without any resistance it was recorded as “no take,” meaning it was not attached to the underlying wound. For these patients, another donor skin was applied 2 weeks later if the first culture swab returned negative (no treatable bacterial load). In those cases without take where the culture swab was positive, the patients were treated with antibiotics for 1 week. The process of applying cadaveric donor skin was then repeated until full take was achieved or until there was no treatable bacterial load. In the meantime, patients received local treatment. When full, definitive take was not reached and the culture swab showed no treatable bacterial load, the patients received only local treatment on the wound bed itself and a STSG was not applied. If the donor skin did take, which means that the cadaveric donor skin “stuck” to the wound, the patient was scheduled for a STSG. In all cases where the culture swab tested positive for bacteria, the patient was then treated with antibiotics for 1 week in expectation of the following treatment: a STSG or an other cadaveric donor skin; however, surgery was not delayed regardless of the culture swab result.   When a STSG was performed, continuous negative pressure wound therapy (V.A.C.®, KCI, San Antonio, TX) was applied at -75 mmHg on top of the graft for 3 days with the polyvinyl alcohol dressing (WhiteFoam™, KCI, San Antonio, TX) used as an interface. Use of the vacuum assisted closure device (VAC) for securing STSGs is associated with improved wound outcomes compared with bolster dressings.⁷ After 3 days the VAC was removed and the percentage of ingrowth was recorded. The definitive STSG was regarded as successful if there was at least 90% take (adherence) to the wound.

Results

  Cadaveric donor skin was applied in 35 consecutive patients (Table 1). In 25 out of 35 cases (71%) the cadaveric donor skin had a take rate of more than 90%. In all but three of these 25 cases was a grafting procedure performed subsequently in the operation theatre. Three patients were not grafted because of various reasons—two patients did not undergo grafting due to personal reasons and the anesthesiologist deemed one patient unfit for surgery.   In 20 out of 22 cases (91%) the STSG was successful after 3 to 4 days (Table 1). Unfortunately, despite a good take of the initial cadaveric donor skin in two cases the definitive STSG failed, because of problems involving the wound bed itself, such as calcification. No significant or treatable bacteria were isolated in culture swab afterwards.   Of all 35 wounds a culture swab was taken prior to applying a cadaveric donor skin. The most common species found were Staphylococcus aureus, Pseudomonas aeruginosa, and contaminated cultures (Table 2). In this case, contaminated culture means that the culture had acquired unwanted foreign microorganisms, mostly from the skin, which normally has no influence on the healing of the wound. The wounds with contaminated outcomes were not treated with antibiotics unless the wound looked clinically infected. Some wounds harbored more than one unwanted bacteria species. These were treated with antibiotics for one week, despite the outcome of the take of the cadaveric donor skin. None of the deleterious group A beta-hemolytic streptococci were isolated.   Cadaveric donor skin was histologically analyzed before and after use in six consecutive patients. In two cases there was good cadaveric donor skin take. New vascular ingrowth was not recorded in any of the cadaveric donor skin. In all cadaveric donor skin there was an evident influx of granulocytes in the epidermal layer of the donor skin with necrosis (Figures 1 and 2). However, in the specimens with a full take the epidermal layer was vital unlike the specimens with no take at all. The original skin before use showed in all cases vital skin, without necrosis or influx of granulocytes (Figure 3). This is indicative that all the histological changes in the cadaveric donor skin took place while it was attached to the wound bed.

Discussion

  This study demonstrated that cadaveric donor skin can function as a predictor for autologous STSG take, thereby determining the readiness of a wound to receive a STSG. If the donor skin took, subsequent success of the STSG was 91%. The authors believe this rate is high considering that all patients were grafted without any delay, even those patients who had a positive culture. Swab cultures were not taken after treatment with antibiotics to evaluate whether the bacterial load had diminished if the patient was already scheduled for surgery. The literature does not report exact percentages for successful skin transplantations, but the expert opinion is that it should be approximately 80% to 90%. However, this mostly concerns patients without any comorbidities and wounds of minimal duration.   This study has shown that cadaveric donor skin can function as a predictor for a definitive STSG take; however, the reason behind this is not known. The use of vacuum-assisted closure therapy after every STSG could have improved the adherence of the skin to the wound bed, as Scherer et al⁷ have reported.   In all but one case culture swabs were positive for bacteria. The presence of bacteria in the wound, such as S aureus and P aeruginosa, could be the reason that 10 out of 35 cadaveric donor skins did not take. The condition of the wound could play a role as well, and only those wounds that clinically seemed fit for an STSG were included in the present study. At the time cadaveric donor skin was applied the patients had not received any antibiotics because swab results were not yet available. However, when the patients received the STSG, they were already treated with antibiotics when the culture swab tested positive. This could have influenced the results in a positive way. The group A beta-hemolytic streptococci was not isolated in any of the wounds and therefore no statement can be made if this bacteria plays an important role in the failure of STSG as suggested by other articles. The two cases of STSG failure were due to problems with the wound bed itself (ie, calcification) and not bacterial presence. According to the literature, a recipient bed that contains a bacteria concentration > 105 organisms per gram of tissue will not support a skin graft. When the wound was heavily contaminated with 107 organisms, infection developed under most grafts.⁸ In the present study bacteria counts were not done—visual inspection determined whether or not to perform a cadaveric donor skin procedure on a clinically suitable wound bed. A relationship was not found between the type of bacteria and the take of the cadaveric donor skin and STSG.   Evidence indicating vascular ingrowth into the cadaveric donor skin was not apparent, thereby improving the definitive take. Most of the cadaveric donor skin had inflammation or necrosis as a reaction. Capla et al’s⁹ report using mice observed vascular regression in the graft at the periphery beginning on day 3 and moved centrally through day 21, sparing graft vessels in the center of the graft. At the same time, vascular ingrowth in the wound bed replaced the regressing vessels. Furthermore, bone marrow-derived endothelial progenitor cells contributed to these new vessels starting as early as day 7.⁹ If the start of vascular regression takes place on day 3, histological changes could have been seen in the cadaveric donor skin samples after 4 days; none of this was seen in the present study.   Granulocytic influx was seen in the epidermal layer in cadaveric donor skin that adhered to the wound bed. Granulocytic influx was not seen in the cadaveric donor skin that did not take. The samples with complete take were all vital. One could imply that since no vascular changes were found that the graft recipient’s immune system plays a role in accepting the skin as a second layer even if a swab culture is positive. However, a direct relationship has yet to be confirmed. It has been suggested that there are two modes of adherence: 1) direct chemical bonding between fibrin in the wound and the dressing material and 2) entrapment of fibrin. Thus, nonviable allograft will adhere to the wound as collagen prosthesis, but will not undergo true chemical bonding.¹

Conclusion

  Cadaveric donor skin has the potential to function as predictor for take of autologous STSG and thereby could determine the readiness of a wound for receiving a STSG. In 10 out of 35 wounds treated with cadaveric donor skin the wound did not accept the applied donor skin, which was probably due to the presence of bacteria or the condition of the wound. The high percentage (91%) of definitive STSG take in those cases with a positive culture result after donor skin application could be a by-product of antibiotic treatment. A direct relationship was not found between the type of bacteria and the take of the cadaveric donor skin and STSG. Granulocytic influx is seen in the epidermal layer, which could be caused by the immune system as reaction on the graft and perhaps on the present bacteria. No direct vascular changes have been recorded in the cadaveric donor skin. Expenses will be minimized if cadaveric donor skin is used as a predictor for STSG take because wounds with no take, and thus a high chance of failure, will not be operated. Furthermore, the time between “ready for STSG” and the definitive surgical operation can be diminished because there will not be a need to wait for culture results, nor would there be any need for prolonged antibiotic therapy when cadaveric donor skin take is successful.

References

1. Burd A, Lam PK, Lau H. Allogenic skin: transplant or dressing? Burns. 2002;28(4):358–366. 2. Andreassi A, Bilenchi R, Biagioli M, D’Aniello C. Classification and pathophysiology of skin grafts. Clin Dermatol. 2005;23(4):332–337. 3. Shedd DP, Pratt LW. James Barrett Brown (1899–1971), head and neck surgeon of a half century ago. Arch Otolaryngol Head Neck Surg. 2002;128(3):233–235. 4. Liedberg NC, Reiss E, Artz CP. The effect of bacteria on the take of split-thickness skin grafts in rabbits. Ann Surg. 1955;142(1):92–96. 5. Wilson GR, French GW, Sully L. Loss of split thickness skin grafts due to non-group A beta-haemolytic streptococci. Ann R Coll Surg Engl. 1988;70(4):217–219. 6. van Baare J, Ligtvoet EE, Middelkoop E. Microbiological evaluation of glycerolized cadaveric donor skin. Transplantation. 1998;65(7):966–970. 7. Scherer LA, Shiver S, Chang M, Meredith JW, Owings JT. The vacuum assisted closure device: a method of securing skin grafts and improving graft survival. Arch Surg. 2002;137(8):930–933. 8. Bacchetta CA, Magee W, Rodeheaver G, Edgerton MT, Edlich RF. Biology of infections of split thickness skin grafts. Am J Surg. 1975;130(1):63–67. 9. Capla JM, Ceradini DJ, Tepper OM, et al. Skin graft vascularization involves precisely regulated regression and replacement of endothelial cells through both angiogenesis and vasculogenesis. Plast Reconstr Surg. 2006;117(3):836–844.

Address correspondence to:

Sylvia A. Stegeman, MD Leiden University Medical Centre Department of Surgery Albinusdreef 2 2333 AZ Leiden The Netherlands Email: s.a.stegeman@lumc.nl