Pertinent Insights On Plastic Surgery And The Diabetic Foot

Given the challenges of healing complicated wounds in patients with diabetes, these authors discuss the use of plastic surgery techniques ranging from split-thickness skin grafts and local random flaps to muscle flaps and pedicle flaps.

The prevalence of diabetes mellitus has been increasing exponentially with more than 220 million people affected. The World Health Organization projects that this number will double between 2005 and 2030. Up to 6 percent of patients with diabetes may develop a diabetic foot ulcer (DFU) with over 15 percent requiring an amputation.1 For those wounds that become non-salvageable and require major lower limb amputation, the long-term prognosis is dire with 50 percent of these patients deceased at five years.2

   The global impact of the diabetic foot has made abundantly clear the need for durable, sound surgical options to facilitate the expedited closure of wounds.

   The treatment of the diabetic foot wound challenges the surgeon with multiple obstacles on the road to eventual wound closure. Numerous options are available and one must be familiar with each modality in order to select the best treatment for the patient. Surgeons must also ensure a thorough diagnostic workup and carefully consider a host of factors (patient age, vascular status, comorbidities, adherence, etc.) in determining the best course of treatment. (See “Essential Insights To Ensuring Proper Patient And Procedure Selection” at right.)

   Plastic surgery techniques for soft tissue reconstruction have demonstrated success for long-term healing and stabilization. Expedited healing of these complicated wounds not only improves the patient’s quality of life but can also significantly decrease health care costs associated with extended wound care. These techniques require meticulous perioperative planning (see “Keys To Perioperative Care” at right) and carry with them potential complications that the surgeon must be equipped to handle.

   The fundamental goals of plastic surgery techniques in wound closure have not changed since ancient times: preservation of form and function. A thorough understanding of the stepwise approach to the use of such procedures is imperative for successful outcomes.

   Regardless of the approach you use, the main objective is achieving a healthy, non-infected wound with adequate perfusion and biomechanical stability. Ultimately, you are striving for a plantigrade, functional foot without residual and recurrent ulcerative lesions.

   Surgeons may perform concomitant osseous reconstructive procedures to correct underlying deformity and further promote stabilization of the foot for soft tissue reconstruction.8 Furthermore, adequate offloading techniques, such as thorough casting, splinting or external fixation with assistive devices, are vital to the durability of the soft tissue reconstruction of the soft tissue reconstruction. However, the detailed discussion of these offloading techniques is beyond the scope of this article.

   Let us now take a closer look at soft tissue coverage through a logical progression along the well established plastic surgery reconstructive approach.9

A Few Thoughts About Delayed Primary Closure

Based on the eradication of infection, adequate soft tissue and/or bone resection, delayed primary closure may be a viable option. One may accomplish delayed primary closure through a properly modified form of skin plasty for the excision of redundant epidermis and dermis.

   Subsequently, this approach can facilitate minimal rotation and/or advancement for a cosmetically appealing incision line. In many cases, delayed primary closure is not an immediate option due to extensive defects remaining after surgical debridement.

When NPWT And Orthobiologics Can Be Beneficial

Negative pressure wound therapy (NPWT) involves the creation of subatmospheric pressure in the local wound environment to promote tissue granulation. There are various NPWT devices and one may incorporate NPWT to help facilitate healing in acute or chronic diabetic foot wounds in which there is significant tissue loss, precluding anatomic delayed primary closure or execution of a skin flap. Once you have established a completely granular wound base with NPWT, you may employ other plastic surgery techniques such as skin grafting.

   Podiatric surgeons may also utilize bioengineered skin substitute tissues following adequate tissue resection in a patient who has proper wound granulation and perfusion.10 If the wound is located in an area that is unsuitable for a skin flap or the adjacent skin is not viable enough for closure assistance, these products provide an efficient means for closure. They provide coverage of any exposed neurovascular structures and tendons to prevent desiccation.

   Acellular matrices are normally not rejected by the body since they are rendered immunologically inert during processing. Instead, the body remodels and replaces the acellular matrix with a native dermal substitute.

   Some examples of bioengineered skin substitute tissues include and are not limited to: Apligraf® (Organogenesis) and Dermagraft® (Advanced Biohealing). Examples of acellular scaffold products include GraftJacket® (KCI), Integra® Bilayer Matrix Wound Dressing (Integra Life Sciences) and Oasis® (Healthpoint). A systematic review by Barber and colleagues showed that bioengineered skin substitutes with a dermal component may improve healing of DFUs.11

Can Split-Thickness Skin Grafts Be Effective?

Skin grafting involves transplantation of skin to a well vascularized, granular wound bed. Split-thickness skin grafts (STSGs) consist of epidermis and variable amounts of dermis while full-thickness skin grafts include the epidermis and all the dermis. It is more common to utilize STSG over full-thickness skin grafting since STSGs have a much broader range of application for defects about the foot and ankle. Split-thickness skin grafts are generally categorized as thin (0.006 to 0.012 inch), intermediate (0.012 to 0.018 inch) or thick (0.018 to 0.030 inch), depending on the thickness.

   There is a variety of harvesting techniques. However, the most commonly used technique involves using a dermatome, which provides rapid and consistent harvesting through an oscillating blade. Dermatomes are typically air powered or electric. One can adjust the width in 1- to 2-inch increments by applying specific blade guards. You can mesh the STSG after it is harvested. Common harvest sites for STSGs include the thigh, lower leg and medial arch of the foot.

   When you are ready to place the graft, ensure that the dermal side is in direct contact to the recipient wound. Exercise caution to avoid wrinkling or excessive stretching. Anchoring the graft to the recipient bed via sutures or staples provides stability during initial adherence and healing. One then applies a stent-type bolster or NPWT dressing, incorporating uniform pressure over the entire grafted area through a non-adherent, semi-occlusive, absorbent material. When surgeons apply STSG correctly with appropriate postoperative care, researchers have shown that STSG is effective for definitive closure of DFUs in patients with multiple comorbidities.12

What You Should Know About Local Random Flaps

When weighing the use of local random flaps, surgeons should consider the source and pattern of blood supply, the varying degree of anatomical structures included in the flap, and the donor site location. These flaps are ideal for small to moderately sized defects and surgeons can use them for closure of wounds both on the dorsal and plantar aspects of the foot.13

   The reconstructive surgeon must have a working knowledge of blood supply to the respective area.14 One would utilize local flaps for defects lying adjacent to the donor site. A local flap may have varying levels of anatomy including: epidermis, dermis, subcutaneous tissue and, less commonly, the deep fascia and underlying muscle.

   Random refers to the blood supply source originating from the intradermal or subdermal plexus traversing through the pedicle. These flaps typically require no greater than a 1:1 length to width ratio for conservation of blood supply derived from either a cutaneous, musculocutaneous or a septocutaneous perforating artery, usually perforating from fixed areas to more mobile positions.

   Flaps calling for rotational, transpositional and interpolation disposition rotate about a pivot point. A transposition flap, typically designed as a rectangle, moves laterally about a pivot point into an adjacent defect. An advancement flap involves moving the skin directly forward. One can excise a triangle of skin from the base of the flap to aid in closure. A rotational flap is a semicircular flap that rotates about a pivot point into an adjacent defect with the arc designed as large as possible. The interpolation flap rotates about a pivot point into a nearby but not adjacent defect with the pedicle passing above or below a skin bridge.

   An axial pattern flap varies in that its blood supply source is through a discernible arteriovenous system. Axial pattern flaps can be further divided into subtypes based off the feeding vascular supply. The fasciocutaneous flap consists of the skin, subcutaneous layer and fascia, and can be efficacious for coverage of a large defect. The senior author favors this flap over a muscle or musculocutaneous flap when applicable for its ease of procuring while involving less bulk with no functional damage.

   For any of the local flaps, atraumatic surgical technique is required to avoid compromising viability of the flap and surrounding tissues. Incision design is dependent on the wound itself, anatomical location and regional blood supply. Meticulous hemostasis before insetting of the flap to the donor site reduces the risk of hematoma formation. Most commonly, suture of lower strength is ideal for reapproximation of the flap and surgeons may allow these sutures to be left intact for prolonged periods in patients with diabetes to prevent dehiscence. Small studies regarding local flaps in the foot have demonstrated that careful preoperative planning for patient selection and flap design directly impact clinical outcomes.15

Pertinent Insights On Muscle Flaps

Frequently, local random flaps are less ideal than muscle flaps due to limited mobility of adjacent tissue for larger defects located at difficult surfaces of the foot and ankle. Muscle flaps can provide local blood supply to devascularized bone. Not only do these flaps enhance the delivery of antibiotics, they also provide a healthy surface for skin grafting. Muscle flaps have a dominant vascular pedicle that supplies the named muscle and the overlying skin secondary to perforating branches. While muscle flaps are classified based on five different vascular patterns overall, all flaps within the foot are classified as type II intrinsic muscles due to the presence of one dominant vessel at its origin and several minor vessels entering distally.16

   The most widely used intrinsic muscle flaps for soft tissue reconstruction are the abductor hallucis, extensor digitorum brevis, flexor digitorum brevis and abductor digiti minimi. The abductor hallucis flap is preferred for plantar and medial wounds, such as those involving the first and central metatarsals, and one may also use these in conjunction with Charcot midfoot reconstructions.16 Surgeons may employ the extensor digitorum brevis flap for small ankle defects, the lateral calcaneus and lower tibial wounds. It is a relatively small muscle and the donor site carries a risk of non-healing due to sacrificing of perforators to this area during harvesting.

   The flexor digitorum brevis flap is favored for plantar central wounds. Use of this flap often allows one to use primary closure for the donor site.8 Surgeons can utilize the abductor digiti minimi flap for tissue loss about the lateral aspect of the mid- and rearfoot. Surgeons often use this flap to close plantar lateral ulcerations.

   In a retrospective study of 32 muscle flaps, Attinger and colleagues demonstrated that the presence of diabetes does not adversely affect the success of flap take. Therefore, one should consider muscle flaps for closure of small diabetic foot and ankle wounds with exposed tendon, joint and/or bone.17

Assessing The Viability Of Pedicle Flaps

A pedicle flap is a partially detached segment of skin and subcutaneous tissue. The flap’s circulation based viability is maintained by its base and the subsequent subdermal plexus. The main advantages of these flaps are a well defined surface, which is independent of a length to width ratio, and the preservation of the main vascular axis.

   One should not use these flaps in areas with movement or variable tension. A flap with a direct cutaneous artery included has a better chance of survival than flaps without that direct cutaneous artery. Increasing the length of the flap or failing to include sufficient vascularity to the flap will increase the chance of dehiscence. When it comes to further divisions into fasciocutaneous, adipofascial or musculocutaneous types, one can dissect these depending on the particular need.

   Common examples for reconstruction in the diabetic foot include the great toe fibular flap, medial plantar artery flap and reverse flow sural artery neurofasciocutaneous flap. The great toe fibular flap is useful when covering the plantar distal forefoot. It involves harvesting a large portion of full-thickness skin from the lateral aspect and incorporating the underlying pedicle, adipofascial and/or periosteum structures.18 Typically, one would close the donor site primarily or subsequently with a STSG or bioengineered skin substitute tissue.

   The medial plantar artery flap becomes very useful for defects located to the dorsal-medial or plantar-lateral regions of the midfoot and heel.19 It provides structurally similar tissue to the plantar foot, posterior heel and ankle defects with its thick glabrous plantar skin and shock absorbing, fibroadipose subcutaneous tissue.

   First introduced by Masquelet in 1992, the reverse flow sural artery neurofasciocutaneous flap is endorsed when one is attempting to cover extensive tissue loss around the heel, ankle and lower leg.20 The location and diameter of the lesser saphenous vein through preoperative vascular imaging with vein mapping are critical and necessary components in execution of this pedicle flap.7 The surgeon should also recognize the level of the most distal peroneal arterial perforator, which is usually 5 cm proximal to the distal tip of the lateral malleolus between the fibula and Achilles tendon. The potential disadvantages that remain are venous congestion and potential donor site complications.

What About Free Tissue Transfer?

Free tissue transfer refers to the vascular detachment of an isolated region, such as skin, fat, muscle or bone, and subsequent transfer of that tissue to another region with microsurgical anastomosis of the divided artery and vein to a separate artery and vein at the recipient site. This is in contrast to pedicle flaps that are left attached to their donor site. Distinct advantages for free flaps include stable wound coverage, improved aesthetic and functional outcomes, and minimal donor site morbidity.

   Defects on the dorsum of the foot call for flaps composed of skin, fat and even fascia, which provide an aesthetic and conforming take. Some of the more common free flaps include the following:

• a radial forearm flap (since it provides a durable vascular pedicle);
• a rectus abdominis muscle flap (for its ease of harvest and durable pedicle); and
• a latissimus dorsi muscle flap (for its large muscle belly surface area and long pedicle).

   Although free tissue transfers are reported to have high success rates and are relatively straightforward, they are also associated with longer operative times, longer hospital stays, and a possible need for recontouring when healed.17

Proactive Pointers To Reduce The Risk Of Complications

Regardless of the plastic surgery reconstruction one chooses, numerous complications are possible. Poor flap design is one of the most common causes of flap failure. Additionally, patient-related factors in the diabetic population contribute significantly to flap complications. Therefore, careful patient selection is of utmost importance.

   To decrease the chances of flap ischemia and necrosis, surgeons must avoid technical errors, such as blood supply injury, excessive tension on the flap, or twisting or kinking the flap pedicle. The use of loupe magnification in combination with meticulous dissection techniques and minimal retraction can help minimize these complications.

Keys To Effective Post-Op Management

Physicians should monitor the patient closely in the postoperative setting so they can recognize complications early and treat them accordingly. Frequently, local wound care, adequate offloading and continuance of antibiotic therapy might be necessary during the patient’s recovery period.

   Postoperative care and recovery vary widely depending upon the procedure(s) one has performed. In the immediate post-op period, the multidisciplinary team involvement is just as crucial in maintaining patient stabilization to maximize wound healing. One should also be mindful of intraoperative culture and sensitivities to help ensure appropriate antibacterial coverage.

   It is also important to inform the patient of the timeframe regarding dressing changes, associated wound care if necessary, bathing restrictions and appropriate emphasis on limb positioning and non-weightbearing status when applicable. Due to a majority of these patients being unable to maintain a non-weightbearing status, it is common to request physical therapy for assisted ambulation training and/or device recommendations.

   For further weightbearing relief to the surgical location, the reconstructive surgeon may incorporate surgical offloading via external fixation devices for immobilization and protection of the repaired wound.

In Conclusion

Several factors play key roles in determining the success or failure of skin flaps or grafting procedures. These factors include: stabilization and viability of the recipient and donor sites; vigilant clinical observation for monitoring viability; the presence of comorbidities and medical conditions; the elasticity and vascularity involved; and leaving the limb in a stable, mechanically sound position.

   The importance of acknowledging the timing of surgery, staging of procedures warranted, and the principles behind plastic surgery techniques as they pertain to the patient with a diabetic foot wound are instrumental for a successful outcome.

   Dr. Facaros is a Fellow in Reconstructive Foot and Ankle Surgery, and is a Clinical Instructor in the Division of Podiatric Medicine and Surgery within the Department of Orthopaedics at the University of Texas Health Science Center at San Antonio.

   Dr. Ramanujam is a Fellow in Postgraduate Research and is a Clinical Instructor in the Division of Podiatric Medicine and Surgery within the Department of Orthopaedics at the University of Texas Health Science Center at San Antonio.

   Dr. Stapleton is an Associate in Foot and Ankle Surgery at VSAS Orthopaedics in Allentown, Pa. He is a Clinical Assistant Professor of Surgery at the Penn State College of Medicine in Hershey, Pa.

   Dr. Zgonis is an Associate Professor, Fellowship Director and Chief of the Division of Podiatric Medicine and Surgery within the Department of Orthopaedics at the University of Texas Health Science Center at San Antonio. He is the Founder and Co-Chairman of the International External Fixation Symposium (IEFS), which is held annually in December in San Antonio.

References

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4. Frykberg RG, Zgonis T, Armstrong DG, et al. American College of Foot and Ankle Surgeons. Diabetic foot disorders. A clinical practice guideline (2006 revision). J Foot Ankle Surg 2006;45(5 Suppl):S1-66.
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13. McCraw JB. Selection of alternative local flaps in the leg and foot. Clin Plast Surg 1979; 6(2):227-46.
14. Clemens MW, Attinger CE. Angiosomes and wound care in the diabetic foot. Foot Ankle Clin 2010;15(3):439-64.
15. Shaw WW, Hidalgo DA. Anatomic basis of plantar flap design: clinical applications. Plast Reconstr Surg 1986;78(5):637-49.
16. Capobianco CM, Zgonis T. Abductor hallucis muscle flap and staged medial column arthrodesis for the chronic ulcerated charcot foot with concomitant osteomyelitis. Foot Ankle Spec 2010;3(5):269-73.
17. Attinger CE, Ducic I, Cooper P, et al. The role of intrinsic muscle flaps of the foot for bone coverage in foot and ankle defects in diabetic and nondiabetic patients. Plast Reconstr Surg 2002;110(4):1047-57.
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   Editor’s note: For related articles, see “Emerging Concepts In Fixation For Charcot Midfoot Reconstruction” in the February 2011 issue of Podiatry Today, “Conquering Plastic Surgery Complications In Wound Care” in the July 2005 issue, “A Closer Look At Plastic Surgery Techniques” in the March 2003 issue, “Is Rocker Bottom Reconstruction A Viable Option For Limb Preservation?” in the December 2004 issue or “Managing Ulcers On The Charcot Foot” in the July 2003 issue.