Introduction to Diabetic Foot Ulcers

What Causes Diabetic Foot Ulcers?

The chain of events leading to the development of diabetic foot ulcers has been well-characterized and involves a variety of factors. In general, the most common precipitating event is trauma to the foot of a person with diabetes. Examples of foot trauma that can predispose a person to develop a diabetic foot ulcer include:

• Irritation to the foot caused by poorly-fitting shoes
• Calluses that are left untreated
• Burn injury to the foot
• Cut (laceration) of the foot
• Penetrating injury to the foot from a sharp object
• Insect bite to the foot

In addition to trauma, there are two other conditions that predispose diabetic patients to develop diabetic foot ulcers:

• Peripheral neuropathy - Damage to the peripheral nerves from diabetes that leads to sensory, motor, or autonomic nerve dysfunction has been estimated to be a causative factor in about 90% of diabetic foot ulcers.

• Peripheral vascular disease - Many people with diabetes suffer from peripheral vascular disease which reduces the blood flow to the lower extremities resulting in tissue ischemia (inadequate blood flow to an area of the body) which is a recognized risk factor development of diabetic foot ulcers. Peripheral vascular disease has been estimated to be a major causative factor in about 35% of diabetic foot ulcers.

• Infection - Once an area of the skin protecting the foot has been broken, usually as a result of some type of trauma, bacteria enter the wound triggering a complex chain of events that can lead to infection. There are three well-recognized patterns of infection in diabetic foot ulcers:

  • Superficial - infection that is localized or limited to the superficial layers of the skin
  • Cellulitis - infection that has spread to the deeper layers of the skin (subcutaneous or connective tissue)
  • Osteomyelitis - infection that has spread to the underlying osseous tissue (bone).

Because normal wound healing is impaired in people with diabetes, without prompt diagnosis and treatment, a superficial (localized) skin infection can quickly spread to the deeper layers of the soft-tissue (cellulitis) and then further spread to the underlying bone (osteomyelitis). The risk for amputation of the infected limb increases significantly once the infection has reached the underlying bone.