Diabetic Foot Ulcers: Tip of the Iceberg
Diabetic Foot Ulcers: Tip of the Iceberg
J. Sheppard Mondy, III, M.D., R.V.T., R.P.V.I., F.A.C.S.
No topic could be less glamorous. The mere mention of diabetic foot care or ulcers is enough to turn most audiences off. But for patients with diabetes and their caregivers, foot care remains an important daily ritual, and represents the first line of defense in avoiding major complications.
WHAT’S THE BIG DEAL?
A foot ulcer is caused by a break in the skin barrier with subsequent destruction of the underlying tissues, sometimes including muscle and bone. Although heart and kidney manifestations of diabetes may appear to be more important concerns, the economic impact of foot ulcers cannot be overlooked. Foot ulcers account for 20-25 percent of all diabetes-related hospital admissions, and more hospital inpatient days are spent treating foot wounds than any other complication of diabetes. A new onset foot ulcer has been estimated to cost approximately $30,000 over two years. Three-quarters of that cost is attributable to inpatient care. Ulceration may be a pivotal event in eventual limb loss, serving as a site of entry for bacterial infection and subsequent gangrene often in patients with compromised circulation. Major amputation has even greater socioeconomic impact. In analysis of all admissions to California hospitals in 1991, the mean direct hospital charge for amputation in diabetic patients was approximately $28,000. This figure was higher for African-Americans. Applied to nationwide statistics, this translates to $1.7 billion and a hospital stay of 2614 years! It is obvious that treatment of established ulcers is quite expensive, and therefore prevention should be the major focus of our efforts in this population at risk.
WHAT CAUSES THE ULCER IN THE FIRST PLACE?
Neuropathy - Neuropathy is the medical term used to describe the nerve damage that occurs when blood sugar is poorly controlled for prolonged periods of time. Neuropathy is common in patients with diabetes of 20 years’ duration, and is present in over 80% of diabetic patients with foot ulcers. Damage to the nerves sensing pain and heat in the feet causes numbness, which is the most common cause of ulcer-ation. Involvement of these nerves results in loss of the normal protective sensation that we rely upon to avoid injury. Loss of the normal pain threshold may result in prolonged and repetitive trauma to the foot while walking and may blunt the response to acute trauma such as stepping on a nail or burning the feet by the fireplace. In addition neuropathy may affect the nerves controlling the small muscles within the foot itself, leading to changes in the shape of the foot and alteration in the pressure distribution with walking or activity. Wasting of these muscles may ultimately cause collapse of the arch and loss of stability (the 'rocker bottom' or Charcot deformity). Overcompensation by other muscles can lead to other foot deformities including 'hammer' or 'claw' toes. These abnormalities lead to pressure points that are then at great risk for ulceration. Even the dry, brittle skin caused by diminished sweating is due to neuropathy affecting specialized nerves within the skin. This makes the skin prone to cracking and fissuring, thus allowing entry of bacteria even in the absence of a large sore. Subsequent infection and abscess formation may damage far more tissue than is apparent from the overlying ulcer.
Poor Circulation - Decreased circulation is a contributing factor in approximately 60 percent of patients with a diabetic foot ulcer and approximately 50 percent of those undergoing major amputation. Arteriosclerosis ("hardening of the arteries") is more common in diabetic patients and affects diabetic patients a decade earlier than in the non-diabetic population. Assessment of the adequacy of the circulation must be considered during the initial evaluation of the diabetic patient especially if a foot ulcer has developed. Feeling the pulse on the foot and at the ankle is the first step in evaluating the circulation. If a pulse cannot be felt, other tests may be necessary to evaluate the status of the blood vessels and to determine if the circulation is adequate to achieve healing. Restoring normal circulation plays a major role in getting established diabetic ulcers to heal.
Infection - Foot infections are the most common soft tissue infection in diabetic patients and may lead to infection in the bones of the foot, amputation and even death. Many aspects of the normal immune defenses may be altered by diabetes, thus increasing the risk of infection in foot ulcers. These immunity functions may be improved by better blood sugar control. The mainstay of treatment for foot infections is surgical drainage of pus and removal of all dead tissue. Antibiotic therapy also plays an important role. Whereas mild infections may be treated on an outpatient basis with antibiotics given by mouth, deep and limb-threatening infections require potent intravenous antibiotics and a hospital stay.
CAN ULCERS BE EFFECTIVELY TREATED?
Because of progress in surgical techniques to restore normal blood flow and the development of effective antibiotic agents, most infections can be controlled and eventually healed. Protection of ulcerations from further trauma by bed rest, padded footwear or even placing the foot in a special cast may allow healing of simple ulcers.
Diabetic foot care is the best proof of the old adage, "an ounce of prevention is worth a pound of cure," because simple preventive techniques help to avoid very costly efforts to heal once a problem has developed. Prevention therefore is the real key and must be foremost in our efforts. Adequate prevention must include aggressive patient education in order to enlist the patient and the family to help in their own health maintenance. The feet should be washed in warm water using a mild soap and inspected daily, using a mirror if necessary to see all skin surfaces. Those with poor eyesight will have to enlist the help of a family member to aid with this task. Another important preventative measure is identifying those patients at greatest risk, especially those with sensory neuropathy and loss of the normal protective sensation. These patients need heightened surveillance, and will likely need to be examined on a regular basis by a health care practitioner familiar with the diabetic foot disorders. All diabetic patients should obtain appropriate protective footwear. Appropriate shoe characteristics include a wide toe box with sufficient height to accommodate any toe deformity, a sturdy insole to provide stability, and an outsole that provides traction and resists penetration by sharp objects such as tacks or nails. For many patients without significant neuropathy custom-fitted shoes are not necessary; however, for patients with any degree of neuropathy, custom shoes are mandatory. In addition, I encourage all such patients to wear only white socks, preferably made from a wool blend or synthetic moisture-wicking material in order to keep the feet dry and to help identify any injury indicated by tell-tale blood or drainage on the socks. Protective footwear is also appropriate for those patients who have a significant abnormality of gait or bony deformity causing pressure points. Frequently, bony abnormalities can be corrected by surgical means in order to eliminate bony prominences and add stability to the foot.
THE TAKE-HOME MESSAGE
Prevention of diabetic foot ulcers is no easy task, but compared with treatment, it seems like a walk in the park. Although strict blood sugar control is of paramount importance in delaying the onset of severe complications of diabetes, additional expertise must come to bear on these patients to improve their quality of life. A multidisciplinary team approach should include primary care for blood sugar control and risk assessment, vascular specialists for maintaining adequate circulation, and orthopedists and podiatrists for assessment of bony structure and protective appliances. In addition, the patient should assume the role of team leader, learning as much as possible about the care of diabetes and its complications.
Dr. Mondy is a board-certified vascular surgeon, specializing in general surgery and critical care at Savannah Vascular and Cardiac Institute and can be reached at (912) 352-VEIN or firstname.lastname@example.org.