Amputation of the lower limb is not without its own risks. In those patients with diabetes, after amputation of one limb, there is a 50% risk of a second amputation in 2 years and the risk of death is 50 – 70% in 5 years. Most amputees require multiple prosthetics over their lifetime. It is also a costly option, at around $50,000 for the initial amputation, but can climb to $250,000 over the next 3 years in rehabilitation, increased care requirements and multiple prosthetics.
As an Amputation Prevention Center facility, we understand that a comprehensive approach is needed to save a limb from amputation. We believe that saving a limb improves quality of life by preserving independence and mobility; in many cases, it may save lives given the high mortality rate after amputation.
Our approach involves evaluating the whole patient to determine their potential for healing. First, it is important to diagnose and manage the main causes of amputation, infection, impaired circulation, and wounds.
Infection is a clinical diagnosis based on how the wound looks. Some tools, such as x-rays, MRI (Figure 1), and bone scans (Figure 2) may help to determine if the infection is in the bone. Bone infections may require a bone biopsy and culture to determine the bacteria which is causing the infection. Skin and soft tissue infections are showing an increased resistance to typically used antibiotics. Depending on risk factors, we often use antibiotics that are effective against resistant bacteria until cultures can confirm otherwise.
Impaired circulation may be visible by gangrene or may require testing to uncover. Gangrenous tissue cannot be salvaged, but the neighboring tissue might be saved if circulation can be restored. There are both non-invasive and invasive tests to uncover impaired circulation. Non-invasive tests can check the pressures in the arteries or capillaries, while ultrasound can directly visualize the artery and flow. Invasive tests like angiography involve using dye injected into an artery and using sophisticated x-rays to view the blood vessels. If there is significant impairment, either an angioplasty (balloon) or open bypass surgery may be required. In those with diabetes, the bypass must often extend all the way down to the foot and not just the knee.
Foot and Leg Wounds
Foot and leg wounds are typically the visual sign of trouble in the limbs, but they are usually just the tip of the iceberg. The first concerns with any wound are to evaluate for infection or impaired circulation as described above. Second, it’s important to keep any extraneous pressure off of the wound. Many foot wounds are caused by an improperly-fitting shoe. Others are caused by an underlying bone or joint problem that increases pressure. One must use special casts or walking boots to take the pressure off and keep the patient active. Some cases require crutches, a rolling crutch, walker, or a wheel chair until the wound heals. Other cases require surgery to correct the underlying bone structure causing the pressure. One example is that of an ulcer on the big toe, usually caused by restriction in its movement (Figure 3). With surgery, the movement can be restored and the ulcer healed. Some ulcers are located on areas that receive pressure when lying down, like on the back of the heel or leg. These require offloading boots during activities like sleeping or reclining.
Wound Healing Techniques
Most wounds need debridement to remove any fibrotic (yellow) or necrotic (black) tissue. Debridements are performed in the operating room or in the wound center. Since wounds are usually a cavity, we perform therapies to improve the wound tissue and make the cavity shallower. After the wound is level and granular (red), a closure technique can be performed. Many techniques are available and have different uses. Some commonly used techniques for wound closure are skin graft, skin substitutes (Figure 4), skin stretchers and plastic surgical flaps. We know that wounds that do not heal by at least 50% in 4 weeks are unlikely to heal in 12 weeks.
Our centers utilize the most advanced tools to measure wounds (Figure 5). We aggressively treat wounds to accelerate the healing process and prevent infections, ultimately saving the limb from amputation.
The Charcot foot deserves special mention because it is often amputated unnecessarily. There are options for treatment starting with custom bracing to simple surgeries to more complex reconstructions. Since the Charcot foot bones are soft, they do not hold screws and plates well. In these cases an external halo fixator can be used (Figure 6). Even in the presence of bone infection, the bone can be removed and fused with graft.
Limb Sparing Amputations
Not all limbs can be salvaged, but the World Health Organization estimates that 85% of amputations are preventable. In some cases a partial foot amputation may be performed to spare the limb. These are termed limb-sparing amputations. They are usually a toe removal or forefoot removal (transmetatarsal) for gangrene or infection. A limb sparing amputation can be a functional alternative to limb loss.