Material and Method: The study included diabetic patients with foot dorsum defects with exposed tendons and bones who were treated with NPT between 2013 and 2016.

Results: In that period 18 diabetic patients with foot dorsum defects with exposed tendons and bones who were treated with NPT. On average, patients’ wounds were 25.28 cm² and they underwent 5.9 NBT sessions during 28.7 hospital days. The defects of all patients were reconstructed with grafts. In the one-year postoperative follow-ups, there were no problems; all patients were mobile and could wear comfortable shoes.

Conclusion: Graft reconstruction after NBT is a reliable treatment option for foot dorsum defects in diabetic patients.

The treatment of diabetic foot ulcers starts with a good glucose control. Next, debridement is done to clean all callus, necrotic, fibrous, and infected tissues to treat infection and provide vascularization in the extremity ^2-4. Foot defects that occur after debridement usually require graft reconstruction with local or free flaps ⁴. The aim is to close wounds with a soft tissue of appro-priate width and thickness that lets patients walk ⁵.

Free flaps are the most appropriate method since they provide appropriately-thick tissue for plantar defects. Foot dorsum skin is considerably thinner than plantar skin, so for free-flap reconstructions, flap thickness is usually thicker than the defect. This prevents patients from wearing appropriate shoes and restricts walking ⁵. Tissue reconstruction of appropriate fineness in the foot dorsum can be ensured with grafts. However, since tendon and bony tissues are usually exposed in foot dorsum defects, it is not possible to reconstruct them with a skin graft ⁶.

Negative pressure therapy (NPT) is a non-surgical wound treatment that increases the formation of granulation tissue ^6-8. It was developed for closing large, chronic, and infected wounds but recently it has also been used for traumatic wounds. This makes it possible to close the wounds, and if required, wounds can be closed with simpler surgical techniques than would otherwise be required. In this study, we present patients who have undergone successful NPT that resulted in completely covering exposed tendons and bone with granulation tissue. This made it possible to perform extremely fine graft reconstruction, leading to a satisfactory result that let diabetic patients walk even after having large foot dorsum wounds.

Necrotic tissues were removed from wounds surgical debridement in the operating room environment. All patients were under anesthesia. Debridement was repeated every two days if it was insufficient the first time. All dead tissue was removed from the wounds and NPT was initiated with a vacuum assistant closure system (Kinetic Concepts, Inc, San Antonio, Texas, USA). Polyurethane sponges were cut to size and placed over the wounds, so they were completely covered the wounds but did not cover surrounding skin. Next, the sponge was covered with an adhesive to create an air-tight seal. A small hole was made in the sponge and a hose was attached between the sponge and a collecting vessel.

NPT was repeated with clean sponges three times a week on Mondays, Wednesdays, and Fridays when patients were in bed. A negative pressure of 125 mm/Hg was applied to all patients. NPT was applied continuously during the first three days then intermittently: 5 minutes actives and 2 minutes passive ⁶.

NPT was repeated until exposed bones and tendons were completely covered with granulation tissue. Next, defects were reconstructed with 2.0-cm thick Split thickness skin graft (STDG ) from the thigh. The patients were followed-up at least for one year in the postoperative period.

Case 1
A 65-year-old male patient was admitted with necrosis on the dorsa of the left foot and toes. Debridement of all necrotic tissues and amputation of the finger revealed a 7×4 cm defect with exposed tendons on left foot dorsum. After 6 NPT sessions, the surface of the defect was completely covered by granulation tissue. The defect was reconstructed with skin grafts and there were no complications after one year (Figure 1a-d).

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Figure 1a: View of 65 years old male patient’s foot with necrosis on the dorsum of the foot and fingers.

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Figure 1b: View of the 7 x 4 cm defect with exposed tendon on the base of the wound after debridement and amputation of the finger.

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Figure 1c: With 6 sessions of NPT treatment, the surface of the defect were completly covered by granulation tissue and the defect was reconstructed with skin grafts.

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Figure 1d: View of the defect in the 3 months postoperative. There were no complication.

Case 2
A 53-year-old male patient was admitted with necrosis on the left foot dorsum. Debridement of all necrotic tissues revealed a 6×4 cm defect with exposed tendons. After 5 NPT sessions, the defect surface was completely covered by granulation tissue. It was reconstructed with skin grafts and there were no complications after one year (Figure 2a-d).

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Figure 2a: View of 53 years old male patient’s foot with 6x4 cm defect on the dorsum of the foot with exposed tendon after debridement.

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Figure 2b: With 5 sessions of NPT treatment, the surface of the defect were completly covered by granulation tissue and the defect was reconstructed with skin grafts.

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Figure 2c: The defect was reconstructed with skin grafts.

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Figure 2d: View of the defect in the 3 months postoperative. There were no complication.

Graft reconstruction is an appropriate option for foot dorsum because they have a thinner and flatter structure, they do not make contact with the ground, and do not bear weight. However, skin graft reconstruction requires a well-vascularized bed and cannot be applied to exposed bone, cartilage, tendons, or surgical implants. This is not possible in foot dorsa because there is no subcutaneous muscle tissue and little adipose tissue, so tendons and bone are usually exposed ⁶. Free flaps are preferred in large foot dorsum defects in the plantar area, but free flaps are thick and can prevent patients from wearing appropriate shoes and restrict walking. To address this, free flaps must be debulked in almost half of patients after free flap reconstruction ^5,11. Alternatively, exposed tendons and bone can be covered with granulation tissue, which makes it possible to perform fine graft reconstruction ¹⁰.

NPT was principally developed to make large, chronic, and infected wounds suitable for reconstruction ¹². It was first used by Fleischmann in 1993 and after Morywas and Argenta suggested using polyurethane foam it became more popular ^12,13. Following surgical debridement, NPT increases the formation of granulation tissue and thus, a large wound can be reconstructed with less aggressive surgical procedures and small wounds can be closed without surgery ^12,14.

NPT removes excess exudate and edema from the wound site ¹² and can remove over 500 cc of fluid in the first 24 hours. NPT reduces edema and exudate surrounding the wound, blood vessels dilate, and blood flow increases. Increased blood flow causes granulation tissue to form more rapidly ⁶. Joseph et al. ¹⁵ showed that with NPT, granulation tissue forms much faster than wet dressings, in a randomized prospective study.

There are many studies on NPT’s effectiveness for treating wounds from high energy trauma with exposed bone and plates. For example, Mullner et al. ¹⁶ reported that granulation tissue completely covered this type of wound in lower extremities. The prospective study reported an average of 16 days of NPT treatment for 12 patients. DeFranzo et al. ⁸ also reported on these lower-extremity defects in 75 patients; 12 patients’ wounds closed primarily, skin grafts were used in 58 patients, and local flaps were used to reconstruct wounds in 5 patients. None required free flap surgery and there were no complications in six-month to six-year follow-ups. Lang et al. ¹⁷ reported on 96 patients with this type of wound. After an average six-weeks of NPT, granulation tissue completely covered wounds and 92 patients’ wounds could be closed with grafts or local flaps. In our clinic, sufficient granulation tissue developed in these wounds in 63 patients after an average of 27 days of NPT; graft reconstruction was performed in 58 patients. These studies consistently show that post-traumatic defects with exposed bone, tendon, and plaques in the ankle and foot can be covered with sufficient granulation tissue in 2-6 week (6-19 sessions) of NPT treatment ^7,8.

In this study, exposed bones and tendons were completely covered with granulation tissue after an average of 5.9 NPT sessions. This made it possible to do graft reconstructions of appropriate fineness on foot dorsum. There was no graft separation in the one-year follow-ups and the patients had no problems wearing comfortable shoes.

Although it is a very effective treatment, NPT has some potential complications. There may be pain while changing sponges and during NPT. The pain is intermittent and is mostly due to the negative pressure, so it can mostly be eliminated by reducing the pressure ¹⁸. In our study, none of the patients complained about pain. Theoretically, NPT can cause arterial injury and major bleeding, so it is contraindicated to apply spongstudy, none of the 75 patients had bleeding. However, in White et al. ¹⁹ study, there was a case with artery injury 22 days after NPT. Excessive granulation tissue may also cause bleeding, especially in children and young adults ²⁰. In our study, none of the patients had bleeding.

In conclusion the aim of diabetic foot treatment is to ensure that patients walk. It is indisputable that the most appropriate reconstruction option is free flaps for large plantar defects. However, NPT makes successful graft reconstructions possible for foot dorsum defects and lets patients walk comfortably without long-term complications.

Acknowlegment:
The author received no financial support for the research, author- ship, and/or publication of this article.

Conflicting Interests:
The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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