Diabetic foot reconstruction (part one)
Certainly among the public, diabetic foot problems are often synonymous with amputation. While diabetes is the most common cause of amputation in the United States, the use of amputation as a solution for the complications of diabetes is fortunately becoming less common. For most minor and some major problems resulting from diabetes, salvage of a functional foot is usually possible.
So why does diabetes affect the foot so severely? The answer is simple and yet complex. Diabetes affects the body’s ability to control the concentration of glucose in the bloodstream. Unfortunately, increased concentration of sugars within the blood has many devastating consequences.
High concentrations of sugar within the blood and serum of the body allow the sugar molecules to attached to proteins in the body. Many of these proteins do not function well with sugars attached to them. The proteins that do not turn over quickly are most affected as they have been exposed to high sugar concentrations for the longest period of time.
Collagen molecules are the scaffolding of the connective tissue within the body. They give skin its strength and keep the tissues from falling apart. They also act as the attachment points for cells within the body that travel. Cells within the body travel for many reasons. Inflammatory cells must travel to the site of infection in order to fight it. If there attachment points within the collagen are blocked by chains of attached glucose molecules, they cannot travel as well. Cells that repair the body also must travel in order to heal wounds. If they are unable to do this, wound healing can become prolonged.
This can also leave the connective tissue stiff. When the collagen within the ligaments and tendons loses its flexibility, the joints lose their flexibility in may become deformed. In addition, this loss of flexibility may result in changes to the way in which the feet handle stress, offloading some areas while greatly increasing the load and others.
The nerve cells have special channels within their cell membranes. These channels allow electrolytes to travel between the inside of the nerve cell and the serum. This is what conducts the electrical signals that are brain uses to communicate with muscles, skin, and other organs. These channels also can be damaged by glucose molecules which become attached to them. This is called neuropathy.
Neuropathy affecting the nerves that give us sensation will cause us to be less aware of painful feelings. This may cause us to be unaware of situations that damage our tissue until it is too late. Damage to the nerves that control our muscles causes weakness. Injury to the autonomic nerves, those nerves which control our skin and blood vessels, disrupt the regulation of blood flow within our legs, leading to swelling, decreased nutrition and oxygenation. The skin can become dry because signals to the sweat glands are disrupted. This can make the skin fragile.
Diabetes, in addition, leads to premature hardening of the arteries. It is a major cause of peripheral artery disease which can lead to inadequate circulation. Finally, some metabolites of sugar that occur only when the glucose is in higher concentrations are toxic to the cells and can lead to death of the tissue as well as hampered energy production.
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Diabetic foot reconstruction (part two)
The damage the diabetes causes many uncomfortable and potentially dangerous problems. Painful diabetic peripheral neuropathy often causes discomfort which is described as burning or “sunburn-like”, although it can be painful enough to require medication.
One of the most striking syndrome is a stress injury called Charcot arthropathy. Because the sensation protecting the feet is gone, injuries that a person with normal sensation would protect because of the discomfort are not perceived, and the injury is allowed to progress to the point that the foot is nearly ruined. This problem often begins as swelling. Sometimes, the swelling can be so severe and redness as to be mistaken for an infection. If it is left on treated, the joints and bones can loosen and deform to the point that the foot is no longer able to bear weight without developing an ulcer. Early treatment and protection of the foot can often prevent this.
Simple and easily treated traumatic fractures in a person with diabetic nerve damage can also rapidly become severe and unstable injuries. Even an ankle sprain, if not properly protected, can result in a joint which is unstable, arthritic, in severely deformed. Any significant unusual swelling, redness, or blistering should be immediately evaluated and closely managed by a physician comfortable and aware of the problems that a diabetic foot can be prone to.
Certainly one of the most dreaded and feared is that of a diabetic foot infection. Bluish or purpleish discoloration under the skin is a sign that bleeding has occurred under the skin. This often heralds more serious problems and should be evaluated. Once a break in the skin has occurred that penetrates into the deeper tissue, it should be aggressively treated. As mentioned above, diabetic tissue has a more difficult time healing because of dysfunction of the inflammatory and reparative cells, as well as the impaired protective sensation of the area. Loss of circulation can choke the tissue of needed nutrients and oxygen. If circulatory problems are present in a foot with a diabetic ulcer, it may be impossible to heal without surgical treatment. Tendon and muscle stiffness, leading to loss of flexibility, can shift the stresses on the foot, overloading parts of the foot while unloading other parts. The severe swelling that often accompanies a diabetic foot infection can also hamper healing and promote infection. Deformities caused by stress injuries and previous surgery sometimes become unstable, irritating the wound. These deformities may also lead to stress concentrations that will allow the skin to be penetrated.
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Diabetic foot reconstruction (part three)
Treatment of a diabetic foot problem should only be done by a physician specialist who is experienced and knowledgeable in this. The determination of whether the specific problem can be treated with or without surgery requires considerable judgment.
Because of the injury is perhaps one of the most important factors. Injuries caused by unusual circumstances, new shoes, new activity, or trauma are likely to heal spontaneously. The next consideration is to identify and treat reversible risk factors. This includes an objective assessment of the degree of infection that is present. While all wounds, and even skin for that matter, have bacteria which live on the surface, and experienced surgeon should be able to identify whether this bacteria is attacking the wound and whether it has caused the tissue to die. This may require treatment with antibiotics and/or surgical removal of the dead and infected tissue. Problems with circulation, either arterial or venous, should be evaluated and addressed when necessary. Concentrations of stress should be identified and mitigated when possible. This may be accomplished through the use of orthotics, special shoes, casts, or cast boots.
One of the most controversy all topics is the place of surgeries directed towards increasing the flexibility of the foot, specifically the Achilles tendon. There definitely are people with diabetic foot problems who benefit from surgical loosening of the Achilles tendon. It is sometimes difficult to identify exactly who will benefit from these procedures. My own opinion is that, if initial treatment fails or the problem has occurred more than once, that gastrocnemius lengthening may be reasonable if overload of the forefoot is a likely contribution to the problem.
While many aspects of the foot with a diabetic injury are specific to the individual foot, some principles are reasonable to follow. Foremost, is to ensure that adequate blood supply is present to allow the tissue to recover from both the surgical and infectious trauma. It is important to avoid incisions over high pressure areas of possible. However, this should not be done at the expense of creating thin bridges of tissue between the wound in the incision. On the chronic and infected tissue needs to be meticulously removed, while minimizing the damage to viable remaining tissue. If a joint is infected, it should be excised or fused. Joints that are unstable need to be stabilized to prevent tension on the wounds that made damage them or delay healing. Bony prominences that cause stress concentrations on the foot should be removed, repositioned, or stabilized.
Complete coverage with viable soft tissue and skin greatly enhances recovery when possible. Certainly a heavily contaminated or still infected wound should not be closed but packed open until the infection is controlled. Residual wounds if present can be closed through natural healing if the diabetes is well controlled and the vitality of the tissue remains or a vacuum assisted closure can be done using a special device. Amputation of nonessential digits or shortening of the amputation stump can be helpful to allow for wound closure. Unfortunately, plastic surgery using tissue flaps is often not possible because of the limited circulation often present.
It is critical to maintain major tendon attachments of possible. The foot is a finely balanced structure. If looked at in cross-section, it has tendons at every quadrant which maintain the posture of the foot. These can be compared to the reins of a horse. If both reins are held at equal tension, the horse moves forward in a straight line. If one of the reins is released, the horse will veer to the side. In a similar fashion, if they tendon is removed without weakening its opposing tendon, the foot will turn to the opposite direction often with disastrous and difficult to reconstruct results. These tendon attachment sites lie at the base of the fifth metatarsal (peroneus brevis), the base of the first metatarsal (anterior tibialis, peroneus longus), the navicular (posterior tibialis), and at the back of the heel (Achilles tendon). If sacrifice of one of these structures is absolutely necessary, then the opposing tendon must be weakened or transferred.
Finally, as mentioned above, weakening or lengthening the Achilles tendon complex is often necessary especially when the deformity involves ulceration of the forefoot, or collapse of the arch. In my opinion, release of the gastrocnemius (otherwise known as the Strayer procedure) is vastly superior and safer then release of the Achilles tendon itself.
It may be necessary to stabilize the foot with plates and screws or through the use of external fixation, a device or cage which surrounds the foot and is attached to the foot through wires or pins.
Postoperative follow-up and restrictions are often greater than with the nondiabetic patient. The complication rate in diabetic foot procedures is considerably higher than the complication rate in people without diabetes. Edema control is often very helpful and elevation should be more strict. Weight restrictions typically are twice as long as those in people without diabetes undergoing similar procedures. It is often necessary to treat residual infection and persistent soft tissue defects. It is also much more common to develop marginal tissue death or necrosis along the edges of the wound. This may also cause the wound to take much longer to heal.
So, when is amputation the best choice? Despite the fear and abhorrence that people have for amputation, limb salvage procedures are sometimes not the best choice. Often if the person with a diabetic foot problem cannot avoid using the foot to bear weight, the salvage may be doomed from the start. It is also not advised that the patient with multiple severe medical problems undergo many complicated and possibly dangerous operations in the attempt to save a foot which may be of limited functional use. It must be possible to create a sturdy, shoe-able, stable, and usable foot. This may not be possible when there is severe bone loss, unreconstructed bull arterial damage, severe soft tissue loss, or persistent deep tissue infection.
Fortunately, this is rarely the case. Diabetic foot salvage can result in useful and functional feet in more than 80% of the cases that I see.
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