Q. A friend of a friend who is a T6 para gets swelling in her lower legs. Somehow she developed a sore on the outside of her lower right calf, but she doesn’t remember any pressure or trauma to the area. The sore wouldn’t heal even though she spent months with it elevated. She finally went to a wound care clinic and they put something called an Unna Boot on her lower leg — it looks sort of like a soft cast. This enabled her to spend time upright in her chair while still taking breaks to elevate her leg. Amazingly, the entire wound healed in about one and a half months! What exactly is an Unna Boot? And how does it help heal so fast?
A. Stacy, your friend’s story is a good reminder that when any type of skin breakdown or burn doesn’t heal right away, it’s time to visit a doctor to get a referral to a wound care clinic. It is important to understand that different types of sores (also known as skin ulcers) require different treatments. Also, different stages of healing require different treatments. Clinicians at a wound care clinic have the specialized training to address this and give you the best shot at healing as quickly as possible.
To explain how an Unna boot works, it is important to understand what it is used to treat. Dr. Bruce Ruben, founder of Encompass Healthcare, a state-of-the-art wound care clinic in West Bloomfield, Mich. (see “New Model for Wound Care,” NM April 2013) explains that there are five main reasons why a wound doesn’t heal:
• Impaired circulation
• Poor nutrition
The main healing problem an Unna Boot addresses is edema (swelling due to blood and fluid pooling in lower extremities). The “boot” is a type of compression wrapping for treating ulcers caused by edema due to venous insufficiency, meaning there is an inadequate return of blood flow from the legs to the heart.
To understand how venous insufficiency can occur in people with SCI, we need to start with a primer on blood flow. The heart drives blood throughout the body via the arteries, and blood returns through the veins. Muscles in the legs act as a “second heart” when they flex and help pump blood back to the heart via the lungs, where it gets oxygenated. When leg muscles aren’t flexing due to SCI or other neurological problems, blood and fluid can start to pool in the veins and tissues of the lower leg and cause edema.
Edema puts stress on the veins and can cause permanent damage to the one-way valves in the veins, called venous valves, which prevent blood from flowing back down the legs in between heartbeats (venous insufficiency). Ruben explains that when backflow from failed valves pools in veins, fluid leaks from the veins into the soft tissues of the legs and feet, causing edema that often has a red color, which is a prominent marker of venous insufficiency.
Any sudden swelling or redness in a leg could be a sign of fracture, cellulitis, or blood clot and should be seen by a doctor immediately.
Kathleen Dunn, RN, clinical nurse specialist and rehab case manager at VA San Diego, explains that not everybody with SCI develops venous insufficiency, even after decades of paralysis. She says it is more common in people with edema that is left unmanaged. Caught in its early stages, edema can usually be managed daily with options like elevating your limbs, wearing compression stockings, and reducing salt intake (see “Managing Edema,” NM July 2011).
Other factors that can cause venous insufficiency include being overweight, having diabetes, and peripheral artery disease. Risk factors for PAD include eating a high-fat diet, smoking, and blood clots, or it can be genetic in nature.
Venous insufficiency can cause ulcers in several ways: The edema stresses the skin to the point where even a minor scratch or bit of pressure can cause an ulcer. Edema can get so bad that fluid starts to weep through the skin, causing maceration (soggy skin) to the point where an ulcer opens up. If an ulcer does develop, edema decreases blood flow to the wound, making it difficult to heal.
An Unna Boot consists of a 4-inch wide commercially prepared gauze bandage impregnated with zinc oxide and (sometimes) calamine. It is wrapped without compression around the lower leg starting about an inch above the toes and ending just below the knee and then flattened and contoured to the leg and foot, like a cast. This is covered by a flexible protective dressing wrap, such as Kerlix, and finally a compression layer, either Coban — an elasticized wrap applied with 50 percent compression, or a medical compression stocking of some type. The Unna Boot is changed every three to seven days.
In order for a wound to heal, edema in the lower leg needs to be reduced greatly, and if possible, eliminated, explains Ruben. The Unna Boot does this by compression therapy, which pushes fluid back into veins and up into circulation. This results in increased blood flow to the ulcer, which carries with it essential healing nutrients. Once the wound is healed, the edema must be managed on a daily basis through use of compression stockings, compression wraps, etc.
Ruben says the zinc oxide-impregnated bandage is also an important healing factor of the Unna Boot. Zinc is a metallic ion that is integral to the biochemistry for growth of new skin cells. “Zinc is easily absorbed into the skin via zinc oxide, and it is utilized by the skin and wound tissue,” he says. “Zinc oxide helps break down dead tissue on the surface of a wound and makes the tissue of a wound more flexible, which decreases pressure on the wound. It is a really good and inexpensive product for wound treatment.”
Before applying an Unna Boot or any type of compression for an ulcer, it is important to make sure the ulcer is due to venous insufficiency and not caused by arterial insufficiency (an ischemic ulcer), due to narrowed arteries (atherosclerosis, i.e., plaque buildup). “You absolutely do not want to use an Unna Boot or any type of compression therapy with arterial insufficiency, because it will further reduce the blood flow and make matters worse,” he says. Prior to applying a compression wrap, a wound care clinician or doctor will check arterial blood flow by measuring blood pressure at the arm and ankle, or by an ultrasound exam — another reason why knowledgeable clinicians are important.
I hope this information helps, Stacy, and I hope you never need it!
• A New Model For Wound Care: www.newmobility.com/2013/04/a-new-model-for-wound-care/
• Compression Therapies: www.encompasshealthcare.com/wound-care/compression-therapies/
• Encompass HealthCare: www.encompasshealthcare.com
• Managing Edema: www.newmobility.com/2011/07/managing-edema/
• Video of Unna Boot application: Go to YouTube and type “Unna Boot Application” into the search box. Several videos are available.
Advice in this column is supported by Craig Hospital’s SCI Nurse Advice Line, a toll-free hotline for people living with SCI, a community service partially funded by grants from the PVA Education Foundation, Craig H. Nielsen Foundation and Caring for Colorado Foundation. For non-emergency nursing information about SCI health, call 800/247-0257 between 9 a.m. and 4 p.m. Mountain time. If you have a health question, contact Bob Vogel at firstname.lastname@example.org.