Poorly controlled diabetes can damage the nerves, blood vessels and immune system. Damage to nerves greatly increases the chances of skin breakdown in the feet. Poor circulation from blood vessel damage makes these breakdowns more likely to heal slowly and develop into chronic ulcers, and a depressed immune system increases the chances of these ulcers becoming infected. Infections from diabetic foot ulcers can become so tenacious that amputation is the only way to prevent them from spreading.
Loss of Proprioception
When poorly controlled diabetes damages nerves, one of the earliest functions affected is proprioception, which is the ability to sense where body parts such as feet and hands are in space. Loss of proprioception changes gait while walking and weight distribution on the feet while standing, which can result in unusual pressure points in the feet that place increased stress on the skin. Loss of proprioception also increases the chances of striking the feet against objects while moving and damaging the skin.
Loss of Pain and Pressure Sensation
Loss of pain and pressure sensation is another consequence of diabetic nerve damage. Pain and pressure sensations serve an essential warning function for ongoing skin damage. Diabetic patients with poor pain and pressure sensation cannot tell when the increased stress on the skin from loss of proprioception is leading to skin breakdown. As a result, skin stress that people with normal sensation would notice and correct is more likely to progress to skin destruction in diabetic patients.
Poor Wound Healing
Another consequence of poorly controlled diabetes is damage to small blood vessels that causes poor circulation, particularly in the feet. Because effective wound healing requires a good blood supply, foot injuries often heal slowly in diabetic patients. Even fairly minor injuries from changes in gait and pressure distribution can lead to serious chronic ulcers due to poor healing.
Decreased Immune Response
Patients with poorly controlled diabetes also have less effective immune systems. Because diabetics are more likely to have open ulcers for extended periods, they are more likely to have their wounds exposed to bacteria and less able to fight off the bacteria that enter. As a result, diabetic foot ulcers often become infected.
Chronic Infections
Good circulation is also important for helping the body fight infection. As a result, diabetic foot ulcers often become chronically infected, and even extensive antibiotic treatment is ineffective in clearing them up. If the infection spreads away from the original wound site, it can result in widespread tissue death, which is known as gangrene. At this point, amputation becomes the only treatment option. An article published in the August 1998 "American Journal of Surgery" found that of diabetic patients who develop foot ulcers, between 14 percent and 24 percent will eventually require some degree of amputation.
References
- "The Lancet"; "Diabetic foot ulcers"; WJ Jeffcoate and KG Harding; May 2003
- "Harrison's Principles of Internal Medicine" 16th edition; Dennis L. Kasper, et al., ed.; 2005
- "American Journal of Surgery"; The burden of diabetic foot ulcers; GE Reiber, et. al.; August 1998
