Overview of Above-the-Knee Amputations
An above-the-knee amputation (AKA) is a surgery to remove a leg. In this procedure, the surgeon makes a cut through both the thigh’s tissue and the large bone in the thigh, called the femur. This surgery might be needed for many reasons like injury, infection, cancer, or problems with blood flow in the leg.
It’s important to know that this surgery can have both physical and mental side effects. However, having a team of different healthcare professionals taking care of you can help reduce the chances of these side effects happening.
Anatomy and Physiology of Above-the-Knee Amputations
The thigh is split into three sections: the front (anterior), back (posterior), and middle (medial). These areas encompass the femur, which is the only bone found in the thigh. The front compartment houses various muscles including the four quadriceps muscles, and the genu articularis. Nerves radiating from the femoral nerve, which is found in this front compartment, help control these muscles. Another nerve, the saphenous, comes out from the femoral nerve and provides sensation to the inner skin of the thigh and leg. The iliotibial band, a tough group of fibers, is found on the outer border of the thigh. The sartorius muscle is located at the top front of the thigh and travels to the inside of the thigh as it reaches towards the upper part of the shin bone.
The medial or middle compartment of the thigh contains several muscles which control the movement of the leg towards the center of the body. These muscles receive signals from the obturator nerve, with the exception of the adductor magnus, which also receives signals from the sciatic nerve. The medial compartment also holds the femoral artery and vein, which provide blood supply to the thigh and move towards the back after passing through a gap in the adductor muscles.
Nearer to the hip, the femoral artery splits into two divisions – one for the surface and the other goes deep to supply blood to the thigh muscles and femur. The great saphenous vein, which returns blood to the heart, is situated near the skin on the inner aspect of the thigh. The rear compartment houses the muscles and nerves that allow your legs to bend at the knee. The sciatic nerve innervates these muscles, allowing them to contract and relax for movement.
Why do People Need Above-the-Knee Amputations
Doctors may decide to perform an above-the-knee amputation (removal of the leg above the knee) for a variety of reasons. One of the most common causes is a serious injury to the lower leg that makes the leg unable to function. If the injury is further down the leg, a below-the-knee amputation may be more suitable.
Experts have created several systems, such as the Mangled Extremity Severity Score (MESS), to help decide between repairing a leg or amputating it. MESS considers factors like the severity of the bone and tissue injury, lack of blood flow to the limb, patient’s reaction to injury, and the patient’s age.
Similarly, above-the-knee amputation could be necessary if an infection has affected the whole lower leg and cannot be removed. This could happen because of wounds that do not heal like those seen in diabetes, a severe infection called necrotizing fasciitis, or in patients with a weak immune system.
Additionally, amputation may be the best option if a tumor in the leg cannot be removed, or if removing it will leave the lower leg useless. Conditions that block or cut off blood flow to the leg, whether due to injury or disease, which cannot be fixed, may also result in an above-the-knee amputation. Furthermore, birth defects that leave a limb unable to function can be another reason for this type of amputation.
When a Person Should Avoid Above-the-Knee Amputations
An amputation above the knee is generally considered when other treatments haven’t worked. The only real reason why this wouldn’t be possible is if the person is too sick to handle the anaesthetic or the operation itself. It’s also worth noting that sometimes the condition of the leg being treated might be the reason for the person’s poor health.
Equipment used for Above-the-Knee Amputations
If you’re having a procedure done in the operating room, there are certain items the surgeon needs to effectively do the surgery – though, as everyone has their own ways of doing things, what they use might differ slightly from one another. Generally, they will need a specialized tool kit meant for bone-related procedures, complete with repurposing tools (retractors), grip tools (clamps), and more.
A few other key tools the surgeon will need include a type of mechanized bone-cutter named an oscillating saw or a flexible manual saw called a Gigli saw. They will also require a sharp cutting tool called a scalpel and a drilling tool. The types of strings (sutures) and bands (ties) used to stop blood flow from vessels are also imperative and these will depend on what the surgeon prefers to use.
Usually, a suction device is used to clear away fluids during the operation. The surgeon will also need equipment, according to their liking, to close up the wound after the operation. Additionally, some surgeons may opt to use a sterilized band (tourniquet) that can help minimize blood loss during the surgery – but not all surgeons will use this.
While X-ray imaging (Radiology) is typically not required during the process, the patient’s bed should be able to allow X-ray imaging to pass through (be radiolucent); this is to ensure that if an X-ray is necessary during the operation, it would be possible to perform without complications.
How is Above-the-Knee Amputations performed
During the procedure, the patient lies on their back on the operating table. The side of the body where the surgery will take place is raised up on some blankets. The leg that will be operated on is cleaned and covered in a sterile way. The surgeon then makes marks on the skin showing where they will make the initial cuts. Some surgeons might make a “fishmouth” type shape with the cuts, but this can also depend on the specific situation and what tissue remains healthy. To help control bleeding, a sterile band (tourniquet) can be placed on the leg before making the cuts.
Next, the surgeon makes cuts along the marked lines, using a special heated tool (electrocautery) to control bleeding. The surgeon continues to cut through the layer of tissue underneath the skin (fascia). The surgeon identifies specific groups of muscles and cuts through them with the electrocautery tool. These muscles are usually cut about 1-2 inches longer than the bone to cover it and allow the muscle and bone to join together (myodesis). The surgeon then identifies, dissects, ties off, and cuts the major artery and vein in the leg. This process is repeated if any other large vessel branches are found. The surgeon also identifies and cuts specific nerves in the leg, using special care to reduce the risk of excessive nerve growth (neuroma).
The next step is cutting through the thigh bone (femur), usually about 5 inches above the knee joint, but this can also depend on the specific situation. In some cases, a procedure called a Gritti-Stokes amputation is performed, which involves cutting the femur at a specific level and fusing the kneecap to the end of the cut femur. This helps to provide better support. The surgeon carefully removes the lining of the joints (synovium) to avoid fluid build-up after the surgery. An oscillating saw is used to cut the bone and a rasp is used to smooth the edges. The surgeon then stitches tendons and muscles to the bone, making sure to keep the leg in a specific position to aid in healing and mobility.
Once the inside structure of the leg is put together, the surgeon stitches the skin and tissue closed in layers. The surgeon takes care not to tighten the stitches too much to avoid tissue damage. Sterile soft dressings are then applied to protect the area. Depending on the case, a support (splint or cast) can be placed over the stump (remaining part of the leg). This helps to protect it and keep it in the right position while it heals.
Possible Complications of Above-the-Knee Amputations
Some possible issues that can arise after an above-the-knee amputation include muscle shrinkage, infections at the wound site, the wound reopening, and sores from wearing prosthetic limbs. To help prevent these problems, particularly those related to skin breakdown, it’s recommended to daily examine the skin, especially if the amputated part lacks sensation.
Prior to surgery, certain indicators can help anticipate a patient’s healing ability. For instance, having a high level of a protein called albumin (above 3.0g/dL), a particular kind of white blood cell called total lymphocyte count (higher than 1500/mm^3), and a specific index on blood flow in your leg and arm (ankle-brachial index) being greater than 0.45 are linked with improved wound healing.
Additionally, issues like muscle contractures, where a muscle or joint becomes rigid, can also happen after surgery. This can occur if certain muscles aren’t attached properly during surgery. Resting in specific positions after surgery and ensuring correct surgical procedures can help lessen the risk of this issue.
Phantom limb pain, a sensation of discomfort in an area that has been amputated, may affect up to 80% of patients. Another potential complication is mental health issues such as post-traumatic stress disorder (PTSD) and depression. These are more frequent in older patients with ongoing pain, and those who had a traumatic amputation. Interestingly, patients who had their limb amputated due to a chronic illness report lower rates of PTSD.
What Else Should I Know About Above-the-Knee Amputations?
Having your leg amputated above the knee can seriously change your life. Not all patients can afford to get a prosthetic leg and might need to keep using a wheelchair after the operation. Those who do get a prosthetic leg will find that their ability to move around is greatly impacted.
Research shows that people who’ve had one leg amputated above the knee walk about 8.6% slower than people who haven’t had an amputation. Another study found that these patients use up to 49% more oxygen when they walk, indicating it’s harder for them to move around. In fact, these patients need to expend about 65% more energy to walk than people without an amputation. If the amputation was done because of a circulation problem rather than an injury, this can go up to even 100% more energy.
This increase in energy needed and decrease in mobility can have a big impact on a person’s private and work life.