Skin Substitutes
Skin substitutes combine living cells such as neonatal foreskin (Apligraf, Dermagraft) with dermal equivalent materials such as type I bovine collagen to mimic natural skin that supports normal healing. Skin substitutes must be surgically applied and several applications needed to achieve natural healing. They will only attach to a clean wound bed so an infection can result in losing the graft. They can also attach to a secondary dressing protecting the graft site from injury.

Skin Flaps
A flap, like a skin graft, is an auto transplantation of tissue. The main difference between the two, however, is that a flap takes its original blood supply with it, whereas a graft is completely stripped of its blood supply during transfer. Because of this, flaps can be made thicker, and can do a lot more than skin grafts. Flaps are used when a skin graft is unsuitable or would leave the wound with inadequate bulk. Flaps are more resistant to infection than grafts, and they permit return to the wound for second stage repair.

Negative Pressure Wound Therapy (NPWT)
NPWT applies suction to the wound bed via a unit attached to a dressing so the patient is attached to the pump for continuous therapy. The suction effect removes excess fluid from the wound bed via a tubing system attached to a canister so while it does not provide a biological solution for the underlying deficiency, it can improve the wound environment. Multiple dressing changes are required each week, most commonly between every 48-72 hours. Untreated infected wounds should have the dressing changed more frequently (every 12 hours). Air leaks in the suction can occur that are signaled by an alarm and require a repair visit to restart the treatment session.

Electrical Stimulation (ES)
Electrical Stimulation uses an electrical current to transfer energy to the tissue to stimulate specific cellular processes that are important for wound healing. They can stimulate fibroblasts to make more collagen, increase the number of receptor sites for growth factors, improve tissue perfusion and decrease edema. High voltage pulsed current (HVPC) is most commonly used. Only trained clinicians should use ES and they need to understand how and when to change dosage, polarity and electrode placement. The duration of treatment is usually 45-60 minutes, 5-7 times per week.

Ultrasound
Like electrical stimulation, ultrasound delivers energy to the tissue to stimulate cellular processes. High frequency ultrasound devices create energy through mechanical vibrations by running electricity through a crystal causing it to vibrate. The vibrations are passed through a sound head to the tissue causing them to vibrate and creating a local thermal effect. The mechanical energy from an ultrasound wave is absorbed by individual protein molecules and may result in the stimulation of cellular effects important for wound healing. The ultrasound probe must be in direct contact with the wound surface, requires specific equipment to generate high and low frequency energy and promotes wound healing through cleansing and debridement.

Growth Factors
Extensive research has demonstrated that wound fluid is rich in growth factors. Growth factors are naturally occurring proteins found primarily in platelets and macrophages. They are needed for normal wound healing to promote growth and migration of fibroblasts, endothelial cells and keratinocytes. There are two types of therapeutic growth factors: single growth factors manufactured using recombinant DNA technology and a physiologic array of growth factors derived from human platelet rich plasma (PRP).

Recombinant Growth Factors
Various recombinant growth factors have been researched for the treatment of chronic wound healing: epidermal growth factors, platelet-derived growth factor (PDGF), and fibroblast growth factors, just to name a few. Recombinant growth factors are designed to amplify single growth factors only. REGRANEX Gel is a topical gel, containing the active ingredient becaplermin. It has activity similar to that of human platelet derived growth factor (PDGF). rhPDGF-BB (Becaplermin) is produced by recombinant DNA technology by insertion of the gene for the B chain of platelet-derived growth factor (PDGF) into the yeast, Saccharomyces cerevisiae. As a healing wound depends on a cascade of growth factors, cytokines and chemokines (table 1), the use of single growth factors cannot restore this delicate balance that is missing in chronic wounds, instead they are designed to amplify the effects of single wound repair proteins. This complexity may explain why single growth factors and growth factor concentrates are incomplete solutions in the management of chronic wounds.

Plasma Derived Growth Factors

Platelet Rich Plasma (PRP)
One therapeutic agent that directly addresses the underlying biological problem in chronic wounds, is autologous platelet derived releasate or platelet-rich plasma (PRP) applied direct to the prepared wound bed. Unlike recombinant growth factors, PRP contains an array of growth factors, cytokines and chemokines and is prepared at the point of care for the patient. Blood taken from the patient is mixed with a small amount of anticoagulant and anti-inflammatory agents then the solution is centrifuged to separate the platelets and serum. The concentrated platelets are then placed into the specially provided syringe that mixes the releasate then it is applied to the prepared wound bed as a gel.

Technology