What Is Below-Knee Amputation?
The goal of amputation is to remove unhealthy tissue and create a remaining leg that is less painful and more useful. Just like many reconstructive orthopaedic surgeries, the surgical goal is to improve a patient’s pain and function. Amputation
can improve quality of life for many patients.
A below-knee amputation (BKA) is an amputation often performed for foot and ankle problems. The BKA often leads to the use of an artificial leg that can allow a patient to walk. A BKA is performed roughly in the area between the ankle and knee. This amputation
provides good results for a wide range of patients with many different diseases and injuries.
A BKA is performed when a patient is severely injured or has a severe infection. After a severe injury to the lower leg, an amputation may be recommended immediately or after attempts to save the limb leaves the patient with significant pain or functional
limitations. Other reasons for amputation can include non-healing ulcers, chronic pain, birth defects and tumor. The decision to amputate involves many factors and is done after a thorough discussion between patient and orthopaedic surgeon.
There are many medical reasons why a patient may not be a good candidate for a BKA. Below are some of the more common reasons.
- Poor blood flow: Patients with poor blood flow should not undergo an operation without proper evaluation before surgery. Adequate blood flow is necessary for wound healing. This may mean a referral to a vascular specialist before surgery is considered.
- Medical problems: Severe heart or lung disease, a poor immune system or bleeding problems may be reasons to not have surgery.
- Infections or tumors that extend above the knee: In cases where an infection or tumor goes above the knee joint, a higher level of amputation may be required.
- Scar tissue or skin and muscle loss: Patients with scarring, tissue grafting or tissue loss may not be candidates for a BKA. Such patients may not have adequate skin or muscle to heal a wound or to use an artificial leg.
- Limited knee function or knee pain: Patients who cannot straighten their knee or have pain and giving way at the knee may find it difficult to use an artificial leg.
- Patients who already do not walk or stand due to other reasons may not benefit from a BKA.
If amputation is being considered, a team approach should be used. This often means meeting with numerous specialists. This may include your orthopaedic surgeon; your medical doctor, who can make sure you are healthy for surgery; a prosthetist, someone
who specializes in making artificial limbs; a physical therapist; and a rehab doctor. Support groups and patients with similar problems who have undergone amputation can be excellent resources before and after surgery.
During surgery, the leg is amputated at a level that removes as much damaged tissue as possible. There is no single length of amputation that will work for all patients. In general, several inches of leg bone below the knee are required in order for an
artificial leg to be properly fit. There is not an advantage to a very long residual leg as it does not improve the ability to fit and wear an artificial leg.
There are many different techniques for performing a BKA. Each surgery is customized for the individual patient. Most patients are completely asleep for the procedure. On occasion, a spinal anesthetic or a nerve block with a sedative may be appropriate.
An incision is made below the desired level of the amputation. The calf muscles and skin are cut in a way that creates a “flap.” The leg bones are cut with a saw. Some surgeons may fuse the end of the two bones (tibia and fibula) together,
called an Ertl technique. The calf muscle is then folded up over the ends of the bones and held with sutures. The skin is closed with sutures or staples. Some surgeons may place a temporary drain to help prevent blood from pooling under the flap.
A compressive dressing or a cast is applied to minimize swelling. Sometimes a cast is applied for added protection. The surgery usually lasts two to three hours. Patients spend some time in a recovery area and are then transferred to a hospital floor.
Most patients will be admitted to the hospital for at least one night following the procedure. Many are able to return home as long as they have help at home and are able to walk with crutches or a walker. Some patients who need more assistance with walking
or have multiple medical problems may benefit from a stay in a rehabilitation facility until they are ready to return home.
The incision will heal over a period of 2-6 weeks. This can depend on patient factors such as blood flow, quality of skin and soft tissue, and medical conditions such as diabetes.
Swelling is common and may last for months if not years.
Swelling often is treated with a compression stocking or “shrinker.” Decreased swelling is critical for proper use of an artificial leg. If a limb is swollen when the prosthesis is fitted, it will be loose when the swelling improves. Similarly,
a swollen limb won’t fit into an artificial leg. Complete healing may take up to a year. The artificial leg is continually adjusted during that time to make sure of a proper fit.
Most surgeons will want the incision to be completely healed before allowing a patient to walk with an artificial leg. Most patients are fitted with a temporary artificial leg within the first three months. Activities are increased slowly over time. A
permanent artificial leg may not be made for 6-12 months after surgery.
Risks and Complications
All surgeries come with possible complications, including the risks associated with anesthesia, infection, damage to nerves and blood vessels, and bleeding or blood clots.
After amputation patients may have continued nerve pain, phantom limb pain or bone spur overgrowth at the end of the limb (heterotopic ossification). Any of these problems may require additional operations. Disability can result from any of these problems.
What kind of activities can I expect to be able to do?
This depends on your level of activity before surgery. Patients often are able to return to the level of activity they had prior to amputation. An amputation may even allow a
higher level of activity such as brisk walking or running. Younger patients without other medical problems or joint ailments may have the best results. Different prosthetic styles are available depending on an individual’s functional demands.
What are the keys to having a good outcome?
Knowing what to expect is important. Even a perfectly performed surgery may be seen as a failure if a patient has the wrong expectations. This is one of the reasons why it is important
to learn about the procedure and talk to as many patients and practitioners as possible before the operation. Speaking with a patient who is of similar age and has undergone an amputation for similar reasons can be extremely helpful.
What can I do before surgery to stay strong?
Prior to your operation it is important to maintain hip and knee strength. This can be accomplished with straight leg raises and knee extension exercises. These exercises should be continued
during your recovery.
What kinds of things can help healing?
It is important to protect the limb and incision after surgery. If you are given a brace or cast to wear, you should wear this exactly as directed. It takes only one accidental bump to open
the incision. If this happens, it could delay healing by several weeks or even months. It may even require additional surgery.
If you are a smoker, you should stop. Smoking has been associated with
numerous complications. These include wound healing problems,
bone healing problems, heart and lung disease, pain, and even arthritis. The risks of surgery are sometimes so high that some surgeons will hold off on performing an amputation until a patient has stopped smoking entirely. Proper nutrition and medical
management of chronic disease, particularly diabetes, also is helpful.
Original article by Jonathan Kraus, MD
Last reviewed by Robert Leland, MD, 2019
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