Complex diabetic foot ulcers often require multiple treatment interventions to achieve healing. Accordingly, these authors discuss key indications, perioperative considerations and technique pearls for split-thickness skin grafts.
Lower extremity ulcerations continue to be costly and serious complications in patients with diabetes. The prevalence of diabetes has increased for over 50 years and an estimated 350 million people will suffer from diabetes by 2030 according to the World Health Organization.1 The Centers for Disease Control and Prevention (CDC) estimate about 30.3 million Americans, or 9.4 percent of the U.S. population, were diagnosed with diabetes in 2015.2 The costs of treatment, increased disability, mortality and complications related to diabetes continues to be among the largest health care burdens.3
Approximately half of diabetic foot ulcerations will develop a serious infection.1,4 When a serious infection takes place, many surgeons opt for an amputation. In fact, roughly 83 percent of all non-traumatic lower-extremity amputations are associated with diabetes in the United States.3 The cost of a lower extremity amputation may range from $70,000 to $120,000 total, including initial hospital costs and follow-up care in the subsequent three to five years post-surgery.3,5
A multitude of factors contribute to delayed wound healing in the lower extremity. These factors include improper offloading, poor glycemic control, inadequate vascular supply and deficient wound care. One should treat wounds promptly and aggressively to help facilitate timely healing. This is especially important to prevent complications associated with chronic wounds that commonly lead to amputation. Once one identifies and treats the causative source that is impeding wound healing, an advanced biologic, graft or flap is useful in accelerating the progression of healing and reducing the risk of further amputation or tissue loss.
Although cellular or tissue-based advanced skin substitutes are readily available, there are an increasing number of barriers to their use including complicated billing and reimbursement issues.6 Recent changes to private insurance policies have limited the utilization of hundreds of skin substitutes.
Understanding The Role Of Skin Grafts And Flaps For Diabetic Foot Wounds
Another option is an autologous skin graft or flap. The most suitable skin graft or flap for the patient with diabetes is dependent on his or her medical comorbidities, circulation, the presence of infection, anatomical location of the wound and donor site availability.7 The restoration of healthy intact skin to protect and serve as a barrier is crucial for these patients, especially after significant tissue loss, to prevent further infection.8
One type of graft that has relatively low donor site morbidity and high reliability is an autologous split-thickness skin graft (STSG). Although skin grafting provides faster time to closure with a single treatment in comparison to other topical wound modalities, there are risks including donor site morbidity and failed take of the graft.9
In patients with diabetes, the decision to use STSG is controversial. Poor patient selection and inadequate wound preparation can lead to graft failures. One must also consider factors such as neuropathy, microvascular disease and increased susceptibility to infection in this patient population.9 In patients with other comorbidities such as end-stage renal disease, donor site and wound infection, rates increase.10
Split-thickness skin grafts are also contraindicated in wounds with exposed bone, tendon and joints where the vascularity may not be sufficient to promote granulation tissue.11 In these areas, one must prepare wound beds with a dermoconductive product to create a granular bed prior to applying a STSG.8 Increased shear and pressure also reduce the viability of a STSG. It is not only essential to optimize the patient and prepare the wound bed, but one should also evaluate the planned location for the graft and avoid direct weightbearing areas.
Despite these risks, STSG can be a useful and effective technique for the closure of diabetic wounds. Split-thickness skin grafts are especially useful for open amputation sites, partially closed wounds and donor sites.7 In larger wounds, STSG offers more durable coverage than the scar that results from secondary closure and allows for more rapid closure in comparison to standard local wound care dressings.8 When clinicians employ STSGs for primary closure on optimized diabetic foot ulcerations, these modalities reportedly have a 78 percent success rate of closing 90 percent of the wound by eight weeks.9
Pertinent Pearls In Technique For Harvesting Split-Thickness Skin Grafts
The technique of autologous skin grafting reportedly dates back to 3000 BC when physicians used the grafts to cover facial wounds in India.12 When one obtains STSGs from a donor site, the grafts should contain both the epidermis and a partial layer of the dermis. The donor site then heals through reepithelization. With lower extremity ulcerations, one performs aggressive debridement to remove biofilm and create a clean, well-vascularized granular bed. If there is exposed bone or tendon, negative pressure wound therapy (NPWT) may help in conjunction with a dermoconductive matrix to create granulation tissue and cover these avascular structures. It may take several weeks to form an adequate tissue bed for application of the STSG. If there is any concern regarding residual infection after debridement, topical antibiotic powder is a viable option.
The donor site is typically the ipsilateral thigh. Anesthesia for this procedure would consist of a local subcutaneous infiltration of 1% lidocaine with epinephrine. It is essential to prepare the donor site and the dermatome with mineral oil to reduce friction. One uses a dermatome to harvest the graft at full power at a 45-degree angle. The physician must measure the donor site prior to harvest to obtain an adequate width and length to cover the wound. One can take additional grafts if necessary.
The surgeon infiltrates the donor site with a combination of topical lidocaine and epinephrine to help with pain and hemostasis. The dressing consists of xeroform or non-adherent gauze with an overlying Tegaderm dressing (3M), and subsequent dressing change at five days post-op. Using a Brennen Skin Graft Mesher, the surgeon meshes the STSG in a 1:1.5 ratio and secures the graft with 4-0 chromic gut or skin staples. One can cut grafts to fit the irregular shape of the ulceration to allow for complete coverage.
To help with graft incorporation, it is important to ensure complete contact between the graft and recipient site. Negative pressure wound therapy is extremely useful in the success of STSGs. In a 2019 study, Turissini and colleagues assessed the use of NPWT to secure STSGs in complex lower extremity wounds including diabetic ulcerations and amputation sites, and noted a mean graft survival rate of 93 percent.13 These study authors also found that the odds of STSG failure in patients who had NPWT were approximately 80 percent less than those who had bolster dressings as their post-surgical dressing.
When applying NPWT, one places a non-adherent layer under the foam, sets the system at 75 mmHg and leaves the NPWT intact for five days. Immobilization and offloading with a cast or posterior splint to limit motion further improves the incorporation of the graft during the healing phase.
Salient Insights On Other Important Aspects Of STSG Use In Patients With Diabetes
Split-thickness skin grafts do not appear to be adversely affected by hemoglobin A1c (HbA1c) levels.13 Studies show that while other factors such as congestive heart failure (CHF), edema and infection play a role, there is no statistically significant relationship between STSG failure and HbA1c level.14
Infection is one of the leading causes of graft failure, highlighting the importance of reducing biofilm and managing any underlying infection.13 Surgeons must place STSGs on a well-vascularized wound bed with low bacterial counts to prevent infection. Although there is not a direct correlation of HbA1c to STSG failure, comorbidities such as peripheral vascular disease and end-stage renal disease (ESRD) negatively impact the viability of a STSG.13,14
Offloading is incredibly important to prevent the recurrence of ulcerations. With STSG, offloading can also reduce shearing, seroma and hematoma formation beneath the graft. Proper offloading will allow the graft to incorporate by diffusing nutrition from the recipient site via “plasmatic imbibition.”15
Split-thickness skin grafts are versatile. One can employ STSG as a primary modality on the diabetic wound, a secondary treatment, an adjunct to a partially accepted/failed treatment or to help facilitate healing of the donor site of another plastic surgery intervention. In burns, STSGs can be very effective. When clinicians use STSG for primary closure on optimized diabetic foot ulcerations, it can also be very effective and potentially more cost-effective than other comparable options.
In a 2019 meta-analysis looking at the use of STSG for diabetic ulcerations, Yammine and Assi noted that 85.5 percent healed over a mean time of five weeks with a recurrence rate of 4.2 percent, infection rate of 4.4 percent and a re-grafting rate of 12.1 percent.16 The researchers also found that donor site morbidity was only 1.75 percent.
Much of the current literature on STSGs for diabetic ulcerations is comprised of retrospective reviews or anecdotal evidence. Accordingly, further prospective investigations are necessary to show the utility of these grafts.
What A Recent Case Study Revealed About STSG
A 70-year-old woman with a history of diabetes and peripheral vascular disease had a hallux amputation that necrosed and dehisced within one month of her initial surgery. She presented to our institution for revascularization with angioplasty and bypass. Ultimately, she had an open transmetatarsal amputation. We utilized NPWT to help optimize the wound bed. After three weeks of NPWT, we harvested and applied a STSG. The wound was healed four weeks later.
It is our hope that the use of STSG can facilitate improved healing of diabetic ulcerations in high-risk patients who otherwise may experience significantly prolonged or complicated courses of treatment. As we have noted above, there is a need for prospective studies to further illuminate the potential and efficacy of this modality.
Dr. Lucas is a new graduate of the Midwestern University School of Podiatric Medicine and is scheduled to begin his residency at Henry Ford Macomb Hospital in Clinton Township, Mich.
Dr. Shin is an Assistant Professor of Clinical Surgery at the Keck School of Medicine at the University of Southern California.
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