Adjustable, Skin-Stretching External Fixation Device and Negative Pressure Wound Therapy Application for Infected Full-Thickness Skin Defects: A Case Series Study

Soft tissue defects are a common problem and remain challenging to manage. These defects occur from a variety of mechanisms, including trauma, open fracture, Morel-Lavallée lesion, burns, extensive tumor resection, soft tissue infection, and pressure injury. Massive soft tissue defects often occur with infection. Several techniques for covering soft tissue defects have been described, including free flaps, muscle flaps, and engineered bilayered skin products. In recent years, flap coverage has been considered the criterion standard. In a multicenter retrospective review, Cho et al¹ reported a muscle flap thrombosis rate of 17%, loss rate of 13%, and salvage rate of 58% in patients with lower extremity trauma. In patients with infected defects, however, the efficiency and safety of free flap coverage, particularly for large defects, remains unclear. The complication rate increases with the size of the soft tissue defect, with defects 200 cm² or larger especially at risk for complications related to flap coverage.² The failure rate of free flaps is estimated to be between 1% and 21%,^3-6 with early complications in approximately 7% of patients and delayed complications in 33%.² Muscle flaps are also at risk for complications such as pain and musculoskeletal dysfunction at both the donor and graft sites.⁷ Engineered skin is costly and time-consuming to produce, and the results of its use are uncertain.

The stretching technique was first introduced by Ilizarov, and it can be used for bone, soft tissue, and skin.⁸ In this technique, soft tissue and skin are gradually stretched using an external fixation device to reduce the wound size and achieve complete coverage of the defect. The technique is easy to apply, and it avoids the need for a donor site as well as associated donor site complications. It can promote epithelial regeneration and wound granulation, lessen the inflammatory reaction, and control superficial soft tissue infections.⁹

In this case series, the authors reported the outcomes of using a modified technique with an adjustable, skin-stretching external fixation device and negative pressure wound therapy (NPWT) to repair full-thickness skin defects.

Demographic characteristics

From January 2014 through December 2017, 7 patients (3 males, 4 females) with full-thickness skin defects were treated with an adjustable, skin-stretching external fixation device and NPWT. The average patient age was 37.43 years ± 10.47 SD (range, 26–55 years). The average skin defect area was 226.29 cm² ± 236.18 (range, 9–532 cm²). These skin defects were caused by burns, infection, trauma, surgery, and necrosis (Table). 

Technique description

Debridement. All dead, damaged or infected tissue was removed. An abrasion technique was applied in which scalpels and curettes were used to scrape the wound tissue until fresh bleeding occurred. The biofilm and devitalized tissue were removed. The wound was washed out to remove any free tissue. Saline and povidone-iodine were repeatedly used for wound irrigation.

Skin stretching. Using a running suture technique, 2 parallel 2.5-mm– or 3.0-mm–diameter Kirschner wires (K-wires) were placed through the skin every 5 cm in a full-thickness fashion 3 cm from the distal and proximal aspects of the wound (Figure 1). Both sides of the skin edges were connected with an adjustable external fixator. Skin stretching was performed by shortening the external fixator and maintaining the skin tension. The skin was stretched at a rate of 1 mm per day. 

Negative pressure wound therapy. The NPWT device was first placed under the skin after debridement to promote the growth of granulation tissue and left in place for 1 to 3 weeks (depending on the control of the infection). After this, the NPWT device was moved to the superficial skin and left in place until wound closure was achieved. The negative pressure was set at 16.8 kPa (125 mm Hg), and the dressing was changed every 3 days to 5 days. If the infection was not under control, antibiotic cement beads could have been placed in the wound after 1 week of debridement. 

Standard care of wound. The wound was checked daily, making sure the tension of the stretched skin was maintained but not too strong. When ulcerations were found at the skin edge or the patient experienced too much pain, the skin stretching was slowed. When both sides of the wound made contact, suture surgery was performed, followed by standard dressing care. 

While undergoing skin stretching, patients were managed as inpatients; after wound closure, they were managed as outpatients.

Use of the skin-stretching external fixation device combined with NPWT resulted in coverage of giant soft tissue defects in 7 patients. All wounds healed, and 2 patients developed ulcers because of rapid stretching. The average healing time was 3.29 months ± 1.60 (range, 1–6 months). The average follow-up time was 7.72 months ± 2.93 (range, 6–12 months).

Case 1

A 30-year-old male experienced a blast injury, resulting in a closed pelvic fracture and massive Morel-Lavallée injury involving the lower back, with preserved soft tissue in front (Figure 2).

Repeated debridement of the necrotic subcutaneous soft tissue, muscle, and fascia resulted in a large, full-thickness skin defect measuring 25 cm² × 15 cm² involving the entire lower back to the hip. The posterior iliac spine was exposed, with no soft tissue coverage. The posterior aspect of the ilium and sacrum were exposed after debridement. Wound cultures were obtained from the soft tissue and bone surface. The soft tissue cultures were positive, and no bone infection was found. Wound cultures were positive for Acinetobacter baumannii. Antibiotics were administered to manage the infection according to results of drug sensitivity testing. 

Open reduction and internal fixation of the pelvic fracture was considered too high risk; thus, closed reduction and percutaneous fixation for pelvic stabilization were performed. Grafting options, including skin and muscle grafts, were discussed with the patient, but he declined such treatment. The skin-stretching technique was proposed, and the patient was amenable to this option.

After complete debridement of the wound, the skin-stretching external fixator and NPWT device were applied. The skin-stretching external fixator was assembled using two 3.0-mm K-wires and a compression fixator. The 2 parallel K-wires were run in and out of the skin every 5 cm in a full-thickness fashion 3 cm from the distal and proximal aspects of the wound. The NPWT sponges were then placed under the skin edges, and negative pressure was applied. On postoperative day 1, skin stretching at a rate of 1 mm per day had begun, per the Ilizarov method.⁸ Antibiotics were tailored according to the sensitivity and serology tests on day 3.

Gradual skin stretching and NPWT were continued for 3 weeks. By the end of 3 weeks, the skin had stretched significantly, wound secretions were minimal, and ingrowth of granulation tissue into the wound bed had occurred. The white blood cell count, C-reactive protein level, and erythrocyte sedimentation rate had normalized. Once the skin edges had been sufficiently stretched to approximate closure, the wound was closed using relaxation sutures, and the NPWT process was continued for an additional 2 weeks. Subsequent wound healing was uneventful.

At the 6-month follow-up, the skin and soft tissue were completely healed, with some scar tissue present. Ultrasonography demonstrated no evidence of a degloving injury.

Case 2

A 30-year-old female experienced a crush injury with an open pelvic fracture (Figure 3). A skin-stretching external fixator was applied in a fashion similar to that described in case 1. The full-thickness skin defect was 28 cm² × 19 cm² in size. After complete debridement of the wound, the aforementioned technique was employed. Gradual skin stretching and NPWT were continued for 3 weeks. Some wound ulceration occurred. The wound was sutured, and a skin graft was used to cover the ulceration. By the follow-up visit 6 months after skin stretching, the wound had healed, with some scarring evident. 

Case 3

A 33-year-old female incurred an open pelvic soft tissue injury (Figure 4). A skin-stretching external fixator was applied in a fashion similar to that described previously. The full-thickness skin defect measured 30 cm² × 17 cm². After complete debridement of the wound, the standard techniques were applied. Gradual skin stretching and NPWT were continued for 3 weeks. After traction was applied, tension-reduced sutures were used to close the wound. Some wound ulceration was present, and dermatoplasty was used to achieve wound coverage. At the follow-up visit 6 months after skin stretching, the wound had healed, with considerable scar tissue because of a predisposition to scarring.

Case 4

A 37-year-old female incurred an open pelvic fracture (Figure 5). The full-thickness skin defect in the anterior pelvis measured 7 cm² × 10 cm², and iliac bone was exposed. The skin-stretching external fixator was applied in a fashion similar to that previously described. After complete debridement of the wound, the standard techniques were applied. Gradual skin stretching and NPWT were continued for 2 weeks. After traction was applied, the wound was directly sutured. At 3-month follow-up after skin stretching, the wound had healed well.

Giant, infected full-thickness skin defects are a difficult problem, especially in conjunction with pelvic fractures and Morel-Lavallée injuries. Extensive fascial and muscle debridement complicates fracture management and eventual soft tissue coverage. Open reduction and internal fixation is the optimal treatment for most pelvic fractures; however, in cases involving large open wounds and soft tissue defects, these methods are not appropriate owing to the risk of infection.^10-11 Additionally, for giant wounds, full-thickness skin grafts and muscle flaps can be problematic, because they are technically demanding, require a large donor site, and are prone to morbidity as well as complications around the graft area.^10,11 

The indications for use of an adjustable, skin-stretching external fixation device and NPWT are as follows: (1) an infected skin defect; (2) large size of full-thickness skin defect (> 5 cm²) and no desire by the patient for skin flap or muscle flap; (3) lack of a good blood supply to the wound area or a donor site defect not fit for using a skin or muscle flap; or (4) a surgeon who is incapable of performing skin or muscle flap techniques. The skin-stretching technique is safe, effective, and simple to apply and previously has been described in a variety of clinical situations.^12-19 However, few studies have reported its use in the management of giant, infected defects in the lower back and hips. The present authors’ experience demonstrates that the adjustable external fixation device can be used safely and effectively in these cases. The device can be assembled using 2 K-wires and 2 pressure bars, and the force and speed of the skin stretching is easily adjusted. This method has several advantages over traditional flap coverage, especially in the management of massive defects. First, the procedure can be performed under local anesthesia. Second, it avoids secondary injuries related to distant donor sites. Third, it can be combined with NPWT to control superficial infection and promote granulation tissue formation and wound healing. Also, there is no size limitation, but larger defects require more time to achieve coverage. Finally, functional outcomes may be better than those achieved with grafts or flaps due to to less scar tissue formation.

The standard of care is quite important for this skin-stretching technique. Before the wound is sutured, it must be checked frequently for complications. The NPWT dressing should be changed every 3 to 5 days. In the present cases, the negative pressure drainage was usually blocked by infected secretions in general and the dressing change was needed. After the wound is sutured, standard care for dressing the wound can be used.

In the present series, the average time to healing was 3.29 months (range, 1–6 months). This finding was similar to that of split-thickness skin grafts (1–2 months) and local flaps (3 months) The traction time mostly depended on the size of the defect.^20,21 Complications associated with the skin-stretching technique include necrosis of the skin edge, pin site infection, wound dehiscence, wound infection, and pain.¹¹ This process is also time-consuming, because the skin must be stretched gradually over a period of weeks. With appropriate medical care and monitoring, however, in certain cases stretching can be done at home (ie, on an outpatient basis). 

Although scarring sometimes looks quite significant, the reasons for it are usually owing to a predisposition to scarring and a form of ulceration. The ulceration relates to the speed of traction and the thickness of the skin. The patient shown in Figure 5 has very few scars compared with the patients discussed in cases 1, 2, and 3. A lower speed of traction (0.7 mm/day) could be used in thin skin, and silicone gel with vitamin C (Dermatix Ultra) and laser treatment could be used for such patients to decrease the scar burden.

There are some limitations to this study. This was a single-center, retrospective case series, and the number of cases was small. There were no comparisons to the traditional methods, such as free flap or musculocutaneous flap treatment. The follow-up time was not long enough to observe the scar appearance or functional recovery. Multicenter, randomized controlled trails are necessary for further clinical assessment of this method.

The skin-stretching technique with NPWT appears to be an excellent option for the reconstruction of giant, full-thickness skin defects as seen in this case series. This combination can control superficial infections and avoid complications related to flaps. The method reported herein is a simple, cost-efficient, and safe means of managing giant, full-thickness skin defects and should be considered in the management of these wounds.

Authors: Ye Peng, MD¹; Wei Zhang, MD¹; Faran Bokhari, MD²; Zuo Cao, MD¹; Gongzi Zhang, MD¹; Shuwei Zhang, MD¹; and Lihai Zhang, MD¹

Affiliations: ¹The First Medical Center of General Hospital of the People’s Liberation Army, Beijing, China; ²Cook County Health and Hospital System, Chicago, IL

Correspondence: Lihai Zhang, MD, General Hospital of the People’s Liberation Army, Orthopedics, No. 28 Fuxing Road, Beiing, Beijing, China, 100853; zhanglihai74@qq.com 

Disclosure: The authors disclose no financial or other conflicts of interest.