Negative Pressure Wound Therapy for the Treatment of Infected Wounds with Exposed Knee Joint After Patellar Fracture

Case Report

A 50-year-old man with diabetes presented with an ulceration of his left knee with exposed joint. He had sustained a closed transverse patella fracture to his left knee in a bicycle accident 5 months previously. At that time, he was treated with open reduction and internal fixation with tension band wiring. As displacement gradually occurred, he underwent revision surgery with tension band wiring and cerclage 4 weeks after the initial surgery. Five weeks after the revision, however, displacement occurred again, so re-revision surgery was performed with tension band wire technique using cannulated screws combined with cerclage wiring.

One day postoperatively, the patient’s temperature rose to 40°C. He reported progressive swelling, increasing pain, and erythema in the region of the patella. Gradually, soft tissue necrosis around the patella developed. Eleven weeks after the re-revision surgery, his wound was opened and debrided thoroughly, and all wires and screws were removed. Pus was found and the culture showed methicillin-resistant Staphylococcus aureus. He was given a dose of intravenous teicoplanin (400 mg/day).

For further treatment, he was admitted. The exposed knee joint 5 cm in length and soft tissue defect 15×10 cm were observed (Figure ). Laboratory evaluation at presentation demonstrated a white blood cell count of 4.6 and a C-reactive protein level of 5.04. After admission, a free latissimus dorsi muscle free muscle flap with a skin paddle was initially planned for soft tissue coverage. However, angiography showed inflammatory change of the lateral superior and lateral inferior genicular artery in the left knee. In addition, venography showed stenosis of the great saphenous vein at the level of the left knee joint. Furthermore, 1 week after admission, the patient had a high fever with a continuous temperature of 40°C. Two weeks after admission, disseminated intravascular coagulation developed. Laboratory evaluation at that time showed a platelet count of 2.5 and a C-reactive protein level of 16.30. Since his condition was becoming critical, we were unable to perform a free muscle flap. After treatment of disseminated intravascular coagulation and intravenous administration of multiple combinations of antibiotics, negative pressure wound therapy was introduced. At this stage, more necrotic tissue had to be debrided and the patella was completely removed (Figure ). Culture demonstrated the absence of sepsis in the knee joint.

Figure 1:. A Soft Tissue Defect Around the Left Knee with Exposed Femur and Patella, and Open Joint at Admission, Which Had Been Present for More than 11 Days.

Figure 2:. After Serial Debridement, the Patella Was Completely Removed (A). The Substitute Negative Pressure Wound Dressing Was Applied to the Soft Tissue Defect with Exposed Knee Joint (B).

On the 25th day after admission, a negative pressure wound dressing and continuous subatomospheric pressure of 125 mm Hg was applied to the soft tissue defect area and the exposed joint (Figure ). Since the VAC system (Kinetic Concepts Inc, San Antonio, Texas) was not commercially available at that time in Japan, we used a substitute VAC system, which was based on the same principle. Materials used in this system were open porous hydrocellular polyurethane foam (Allevyn non-adhesive, Smith & Nephew, Largo, Florida), transparent polyurethane adhesive drape (Ioban 2 Antimicrobial Incise Drape; 3M, St Paul, Minnesota), and a vacuum system consisting of a J-VAC reservoir (Ethicon Inc, Somerville, New Jersey), suction drainage tubes, and a wall suction vacuum outlet.

Repeated vacuum dressing changes (twice per week) and minor debridement for 20 days led to a granulated wound bed, which covered the exposed bones and joint (Figure ). Split-thickness skin grafts were applied on the 21st day (Figure ). Wound healing was completed 49 days after the skin grafts (94 days post-admission), and the patient was discharged (Figure ). At 5-year follow-up, the patient had a knee range of motion 0° to 30° and was ambulatory without assistance.

Figure 3:. Formation of Granulation Tissue on the Exposed Joint After 20 Days of Negative Pressure Wound Therapy (A). Split-Thickness Skin Grafts Were Applied After 21 Days of Therapy (B). Wound After 70 Days of Therapy. The Skin Was Completely Healed Without Evidence of Recurrent Ulcerations (C).

Discussion

A complex soft tissue defect with joint exposure remains a challenging management problem in any patient. Such a wound may result from trauma, peripheral vascular disease, diabetes, and postoperative complications. An exposed knee joint can lead to septic arthritis of the joint. To close the wound and joint and to salvage the affected extremity, a local flap or free vascularized flaps using a microsurgical technique have been commonly applied. ^1–4 However, associated trauma, previous surgical treatment, or peripheral vascular disease may contra-indicate coverage with local or free flaps. In addition, these flaps may cause some morbidity at the donor site.

Recent literature has addressed the use of negative pressure wound therapy for orthopedic and extremity wounds with good results. ¹⁵ Negative pressure wound therapy has been reported to be effective in exposed vital structures such as bone, tendon, nerve, and orthopedic implants. ^7–14 Previous studies have shown that an applied negative pressure allowed arterioles to dilate and increased blood flow to the area, producing a proliferation of wound granulation tissues. This has been demonstrated to result from a decrease in the capillary after-load, which then promotes capillary circulation and inflow. ^6,17 Granulation tissue formation then increases, and the bacterial count decreases significantly. Negative pressure wound therapy may also stimulate wound healing through the promotion of cell division, angiogenesis, and local proliferation of growth factors. ¹⁸

To our knowledge, this is the first report of negative pressure wound therapy used in a patient with a large soft tissue defect with exposed knee joint. Despite the chronic wound secondary to infection, healing was achieved through the use of negative pressure wound therapy, thus promoting granulation tissue formation and closing the joint. Once adequate granulation and joint closure had occurred, the wound was then suitable for split-thickness skin grafts.

We suggest negative pressure wound therapy as an alternative option for patients with lower limb wounds containing exposed bones and joints, when free flap transfer is contraindicated. Our result add to the growing evidence that negative pressure wound therapy is a useful adjunctive treatment for open wounds around the knee joint.