05 Sep Above Knee Amputation Procedures
by Douglas G. Smith, MD, Amputee Coalition Medical Director
[tabs style=”default” title=”Transfemoral (aboveknee) amputation”] [tab title=”Part 1″]
This is Part 1 of a three-part look at the transfemoral (aboveknee, or AK) amputation level, one of the more frequently performed amputation procedures. This article examines the prevalence of this amputation level, the nomenclature, and the various challenges facing the transfemoral amputee. Part 2 will examine surgical and postoperative issues, and Part 3 will focus on prostheses.
Though the transfemoral amputation can be a challenging amputation level for the amputee, the surgeon, prosthetists, therapists, and every member of the healthcare team, it is still required fairly often, despite the tremendous emphasis in recent decades on preserving amputation levels in the foot and below the knee.
Thirty years ago, people with foot infections that required amputation would quite frequently have those amputations in the thigh. At that time, doctors didn’t fully understand the impact of different amputation levels on rehabilitation and function. They also strongly believed that the chance of healing a thigh-level amputation was significantly better than amputations in the calf or foot, which historically had a very poor healing rate. To counter this thinking, one of my mentors, Dr. Ernest Burgess, helped spearhead a huge effort to educate healthcare professionals that healing in longer amputation levels was indeed possible and, for many individuals, preferable.
Still, more transfemoral amputations are required than many people realize. Of the more than 1.2 million people in the United States living with limb loss, 18.5 percent are transfemoral amputees, according to the latest figures provided by the National Center for Health Statistics. A study by Dr. Timothy R. Dillingham and colleagues titled Limb Amputation and Limb Deficiency: Epidemiology and Recent Trends in the United States, which was published in the Southern Medical Journal (2002), offers more statistics. The study, provided to us by the National Limb Loss Information Center (NLLIC), shows that there were 266,465 transfemoral amputations performed in the United States from 1988 through 1996 (the most recent years available). That’s an average of 29,607 annually. Statistically, almost one of every five people living with limb loss in this country has a transfemoral amputation.
In the United States, this amputation level is most commonly known as an above-knee amputation, or AK. Internationally, it’s referred to as a transfemoral amputation because the amputation occurs in the thigh, through the femoral bone (femur). Today, the international terminology is gaining favor as a more definitive description of the amputation level involved. Plus, using international nomenclature puts us more in line with the rest of the world.
While the transfemoral amputation level is fairly common, there’s nothing simple about adjusting to life after surgery. The person living with transfemoral limb loss faces distinct challenges, such as increased energy requirements, balance and stability problems, the need for a more complicated prosthetic device, difficulty rising from a seated position, and, unlike with amputation levels in the tibia and the foot, prosthetic comfort while sitting.
Energy and Speed
No amputation is “easy” to adapt to, but the transfemoral certainly offers more challenges than amputations in the calf or foot. Studies show that the higher the amputation level, the more energy needed for walking.
A study by Dr. Robert L. Waters and co-workers titled Energy Cost of Walking of Amputees: The Influence of Level of Amputation, which was published in The Journal of Bone and Joint Surgery (1976), looked at gait and energy use among 70 people with lower-limb amputations. Transfemoral, transtibial and Syme amputations resulting from vascular disease and trauma were compared among the participants with limb loss and to a control group of individuals without amputations. As Graph 1 illustrates, the chosen velocity of walking for vascular amputees was 66 percent of that for nonamputees at the Syme level, 59 percent at the transtibial level and 44 percent at the transfemoral level. Among trauma amputees, velocity was 87 percent for the transtibial level and 63 percent for the transfemoral level. In short, the higher the amputation level, the slower the walking speed. Trauma amputees walked faster than vascular amputees primarily because of age differences and overall health status. By the time blood vessels in the legs are diseased to the point where amputation is needed, individuals with vascular disease also have significant disease of the blood vessels in the heart and lungs. Gait improved and the energy required for prosthetic walking significantly decreased as amputation levels moved toward the foot.
Measuring energy required for walking is tricky. We’re not counting just the energy needed for each step; we’re also looking at the energy used over a particular distance. In some circumstances, each step for a transfemoral amputee requires more energy than it does for a transtibial amputee, but in other circumstances, the energy per step can be the same or even a little less. Because the stride length for a transfemoral amputee is shorter, however, it takes many more steps to cover the distance. Therefore, when the total energy used by a transfemoral amputee to get from point A to point B is added up, it will probably have taken him or her much more energy than it would have for a transtibial amputee to go the same distance, even though the transfemoral amputee’s energy expenditure per step may be less because of the shorter stride.
To measure energy, subjects are outfitted with a mask and a backpack containing an oxygen tank. As the person breathes in and out, sensitive monitoring equipment measures the amount of oxygen being inhaled and exhaled through the mask over a set distance. This oxygen use is then converted to the amount of energy that’s required to cover that distance. If your energy requirements increase, you breathe faster and use more oxygen. Graph 2 shows that the higher the amputation level, the more energy expended per meter traveled.
It’s not uncommon to slow down to the point where your energy use per minute approximates normal, but your energy use per distance walked – whether it is measured per meter, per 10 yards or per mile – increases substantially. But you may not feel fatigued because you’re burning that energy over a longer period of time.
A person with a transfemoral amputation usually walks more slowly than before but expends more energy over a longer time because it takes a greater effort to walk with an amputation in the thigh. To illustrate this, think of how you feel when you run a short distance as fast as you can and when you walk the same distance. Sprinting 100 yards will likely leave you out of breath, while walking will take you longer but will not leave you winded. A person with a transfemoral amputation walking 100 yards will, of course, take longer to cover that distance. But he or she will need to expend more energy to go that distance than does a person with a lower amputation level or no amputation. The factor that leaves you out of breath isn’t the total energy you expend; it’s how fast you expend it.
Another factor to consider is how energy expenditure will leave you feeling by the end of the day. We generally recover quickly from short, fast bursts of energy use and go about the rest of the day without feeling unusually tired. But if you walk more slowly for several hours, you’ll probably feel quite tired at the end of the day. You’ve expended less energy per second, but you’ve expended more energy over a longer period of time. For a person with a transfemoral amputation, it takes more energy to walk, even though he or she isn’t using as much energy per second.
Steps, Stairs and Other Ups & Downs
Inclines and stairs also become more challenging. Most people with transfemoral limb loss do not go “step over step” as they walk up or down stairs. Rather, they tend to go step by step, one stair at a time. Typically, an individual with transfemoral limb loss will first step up with the sound leg, then bring the prosthetic side up to the same step. This is because the prosthetic knee does not provide the power necessary to take the person up to the next higher step. The prosthetic knee would buckle as body weight was transferred to it in pushing up to the next stair, and the person would collapse. Newer, more advanced prostheses, such as the microprocessorcontrolled C-Leg, do allow some people to walk step over step, especially going down stairs. This is because it’s designed not to collapse. But even the most advanced, currently available knee units do not have a motor that provides lifting power.
Loss of knee power is one of the factors that make it very challenging to adjust to a new way of walking after a transfemoral amputation. The knee is an amazingly strong joint, and its power is vital for walking, rising, going from sitting to standing and vice versa, and transfers, such as getting in and out of the bathtub or on and off the toilet. After a transfemoral amputation, the muscles around the hip still move the thigh forward and back, but the prosthetic knee, contrary to a common misconception, cannot actively extend the lower leg out straight or bend it back into flexion. Prosthetic knee units are not run by muscles so they function, in a sense, like well-controlled passive hinges. Even with technological advancements, a prosthetic knee that can provide motor activity to take a person from standing to sitting the way a real knee does has not yet been made.
It Ain’t Easy
With all of these factors in mind, it’s no wonder that a patient of mine who had a transtibial amputation that was later, because of infection, revised to a transfemoral amputation, told me, “Doc, it’s not twice as difficult going from a BK (below-knee amputation) to an AK (above-knee amputation), it’s 10 times more difficult!” The biggest factor is the missing knee joint. He had to go from a prosthesis that essentially replaced one joint – the ankle – to one that replaced two – the ankle and the knee.
This means that problems with stumbling and falling increase, and much greater concentration is needed for walking. While traditional research such as Dr. Waters’ work looked at the physical energy required for walking, newer research is trying to measure the mental energy involved. Problems like stumbling and falling, while difficult to measure, are probably related to both physical and mental energy and balance. As a researcher and a transfemoral amputee, Laura Willingham has led the rest of our team at Prosthetics Research Study (PRS) in our investigations of stumbling, falling and the increased concentration required for walking by people who use a lower-limb prosthesis. Through work in focus groups, we have identified the following issues that are of particular concern to people with lower-limb amputations:
- Mental Energy: This refers to the conscious effort of thinking about walking, concentrating and moving with a prosthesis.
- The Stumble: This happens while walking or moving when the rhythm of the walk or movement is suddenly stopped or changed. A stumble does not mean actually falling down; instead, it can be thought of as a “near miss.” Recovery from a stumble often happens with a “stutter step,” a hop or a shift in weight balance.
- The Semi-Controlled Fall: This occurs when you lose your balance and start to fall. You recognize the fall as it is occurring and brace for it or grab onto something to either break the fall or help you land in a protected fashion. The semi-controlled fall may evoke feelings of embarrassment or frustration.
- The Uncontrolled Fall: This occurs during a sudden loss of balance when there’s insufficient time to protect yourself from the impact of the fall. This type of fall is more likely to produce injury and can make you feel angry, anxious and confused.
While stumbling and falling clearly are issues for all lowerlimb amputees, the higher the amputation level is above the knee, the greater the risks of falling. Walking is automatic for most individuals, with almost no conscious thought. A person with a transfemoral amputation, on the other hand, must really focus on walking, especially on uneven surfaces, stairs and inclines, and in unfamiliar areas. Different environments can bring different and sometimes hazardous challenges. It’s one thing to take a leisurely walk on an even, smooth pathway. It’s something else altogether to navigate an area such as an airport concourse where people are walking at many speeds, stopping and starting, and coming in and out of “your space” from all directions. You have to make countless adjustments to your gait as you walk to or from your gate.
I continue to be impressed by the number of people with this amputation level who master the skills needed to walk confidently with a transfemoral prosthesis. It’s a credit to the human spirit of perseverance that they’re able to face the many challenges brought by the loss of knee power and overcome them.
“Success consists of getting up just one more time than you fall.” – Oliver Goldsmith, Irish playwright
[/tab] [tab title=”Part 2″]by Douglas G. Smith, MD, Amputee Coalition Medical Director
Part 1 of this series of articles on the transfemoral (above-knee, or AK) amputation level examined various aspects of energy use while walking and some of the many challenges of adjusting to life with this type of amputation. This article will focus on surgery and postoperative management.
The transfemoral amputation level teaches surgeons the great importance of muscle reconstruction. A person with a transfemoral amputation can support very little, if any, weight directly on the end of the limb. In addition, the thigh muscles are out of balance after the femur is transected (cut). Therefore, during surgery, two of our goals are to try to regain muscle balance and to better position the femur so that it can take some weight on the side of the thigh.
The term for the surgical technique to reattach muscles to bone following amputation is “myodesis.” There are two main methods for performing this surgery:
- The surgeon can drill holes through the bone and suture (attach) the muscle directly to the bone.
- The surgeon can secure the muscle over the bone and suture it to the periosteum (the thick tissue covering the bone).
There are four major muscle movements in the thigh:
- Forward, which is called flexion
- Back, which is called extension
- In toward the middle, which is called adduction
- Out to the side, which is called abduction.
The abductors and flexors are attached up near the hip. They are above the surgical division in a transfemoral amputation so they usually are not affected by the transection. However, the adductor and extensor muscles are divided because they are attached at the lower end of the thigh. Therefore, in this type of amputation surgery, you lose those muscle attachments that allow you to move your leg inward, such as when you cross one thigh over the other, and to bring your leg back behind you.
Without the adductor and extensor muscles and without myodesis, there’s a natural tendency for the leg to simultaneously go forward into flexion and out to the side in abduction. The surgeon, therefore, needs to reattach muscles to the femoral bone or its periosteum as a counterbalance to the forces of flexion and abduction. Myodesis makes the residual limb stronger, more balanced, and keeps the femur centered in the muscle mass.
You might be asking, “What about the big muscle in the front of the thigh?” That’s called the quadriceps, and it is actually primarily a knee muscle. It plays a small part in hip movement, but chiefly is involved in knee movement.
Unlike individuals with a knee disarticulation, a person with a transfemoral amputation can no longer take the body’s weight directly on the transected end of the limb. As noted, one of the surgical goals is to balance the muscles so that some weight can be borne on the side of the thigh. The adductor muscles are tied down to prevent the femur from drifting out. If the femur drifts out, weight cannot be loaded as easily onto the side, and the bone end can press painfully against the socket. By surgically balancing the muscles, we make it easier to position the leg somewhat in adduction (tipped inward a bit) to help with weight loading and to maximize socket fit later. In the socket, the leg is positioned so the weight can go on the side of the thigh, not at the end of the limb. To get the weight more onto the side, the leg must be adducted.
Myodesis may also be beneficial in reducing a collection of tissue called “the adductor roll,” which can form high on the inner thigh above the socket line and can be quite bothersome for some people. Many believe that the adductor roll is caused, in part, by the retraction of muscles that are no longer held in place. The tissue spills out over the top of the socket, and before long a significant roll of soft tissue has accumulated in that area. The socket may dig painfully into this extra tissue. Myodesis helps secure that tissue and seems to reduce the adductor roll for some individuals.
Now that we understand the goals of myodesis, here’s the downside: Muscle doesn’t hold sutures very well, and the transfemoral amputation occurs in an area of muscle that isn’t ideal for holding surgical attachments. Many people don’t realize just how difficult it is to sew into muscle. You may look at a solidly built person, say a bodybuilder, and think, “That’s a lot of strong material to work with.” But appearances from the outside are deceiving. Think of the tissues of the muscles like a mop. The strings of the mop are encased in a plastic wrapper when you buy it. That plastic wrapper is like the fascia, which is the tissue that covers the muscle. Suturing muscle is like sewing through the plastic bag and the strings of the mop. Fascia, like the plastic wrapper, provides some reinforcement, but the individual strands of muscle don’t hold sutures well. And like the strings of a mop, there’s not much between the muscle strands to use as reinforcement. When a suture is inserted in mid-thigh, it drifts downward in the muscle tissue because it can’t be securely attached to anything. If the surgeon tries to go across the strands and loop them together, blood flow is cut off to the end of the muscle.
The fascia is the best available tissue for holding sutures in a transfemoral amputation, but it’s not especially thick around most of the muscles in mid-thigh. In fact, it’s quite thin and can tear easily. Tendon and skin hold sutures well, muscle does not, and fascia at mid-thigh is just so-so. So while myodesis is important, it can be difficult to do securely at this level. In the postoperative period, occasionally there are patients who feel the myodesis stretching out or even pulling free. “Doc, I think I felt something give” is the way they usually describe it.
Transfemoral Amputation and Children
The growth plate located at the bottom of the femur is lost in a transfemoral amputation. This plate provides for 60 to 70 percent of thigh growth. In children, that means the residual limb won’t grow equally with the upper part of the other limb, which becomes increasingly important as the person grows up and enters adulthood. By then, the differences between the two thighs can be significant. What appeared to be a very long transfemoral amputation in a young child turns out to be a very short transfemoral amputation level that’s difficult to fit with a prosthesis when the youngster becomes an adult.
When dealing with osteosarcoma (a type of cancer) in children, one challenge concerns the difficult decision between amputation and limb salvage. Most cases of this cancer happen in children between the ages of 8 and 15, and the disease frequently occurs in the knee area. A knee disarticulation often is not possible, however, because part of the tumor may be located at or near the far (distal) end of the femur. So, by necessity, an amputation must be at the transfemoral level, even though it means the growth plate near the knee will be lost and the residual limb will become shorter as the person grows.
Growth issues can also be a major concern with limb salvage. More often than not, salvage involves removing the end of the femur and replacing it with bone or metal, which does not grow. For young children, salvage can mean a number of surgeries over several years, each designed to add a bit of length to the limb because it’s no longer growing at its proper pace.
When facing the difficult choice between limb salvage or amputation, issues concerning rehabilitation and quality of life afterward must be examined closely before proceeding. We hear exciting news about limbs that are salvaged or even reattached. The typical person often believes this means, “It will be normal again.” Unfortunately, this usually is not the case. These salvaged limbs still have severe limitations. The procedures are complex and frequently there are complications. Even after the person has gone through extensive surgery and rehabilitation, it can be daunting to manage all of the issues of living with a fragile limb – one that is often without normal sensation. Limb salvage, like amputation, can still mean real restrictions, with issues such as functional limitations, durability and pain.
In general, for those who have had lower-limb amputations, healthcare professionals have tried to encourage aggressive and active rehabilitation in tandem with wound healing. My mentor, Dr. Ernest Burgess, used to say: “There is no excuse for delay or procrastination waiting for amputations to mature. Maturation will take place concurrent with active return of function.” In other words, “push ahead with the rehab.” Dr. Burgess urged others to overcome the misconception that rehabilitation should come only after the wound heals. He spent much of his professional career designing protocols to safely move forward with rehabilitation while the amputation is still healing. Many of the immediate postoperative casting protocols for partial foot amputations, transtibial amputations and knee disarticulations do include early weight-bearing by allowing some limited walking. Protocols for very aggressive rehabilitation after transfemoral amputations certainly have been offered; unfortunately, these are less successful than those for lower levels. Many rehabilitation programs that use aggressive casting protocols for transtibial amputations have drifted away from them for individuals with transfemoral amputations, primarily because of patient comfort. The end of the femur just cannot support the body’s weight so any immediate postoperative prosthetic device must include the pelvic area.
When amputations are performed at or below the knee, the cast comes up no higher than near the top of the thigh. For a casting protocol to work after a transfemoral amputation, it must come all the way up to incorporate part of the pelvis. Traditionally, casting rings, called brims, are used to help mold the cast in the region at the top of the thigh and buttock. The cast is then extended up around the hip and waist in a spica fashion. Spica means a cast that incorporates the waist. A hip spica is an extremity cast that incorporates the torso. While the top part is a little softer than the full rigid cast, it still comes high up into the groin and around the waist. These casts are designed to keep weight off of the surgical incision and to spread the weight higher up the residual limb. They’re also designed to stay on as the limb volume changes in the postoperative period.
When I first moved my surgical practice to Seattle, I worked with Mr. Joe Zettl, the prosthetist who teamed with Dr. Burgess to pioneer many of these casting techniques. We found that these protocols work well for the hour or two a day when the patient is upright during therapy, but that they are very uncomfortable when the person is lying in bed or sitting in a chair. For the transfemoral amputee, these immediate postoperative prosthesis (IPOP) casts are not designed to be removable. There are hygiene factors to take into account because the cast incorporates the waist and groin. We found that while patients appreciated having this system for the short time they were upright in therapy, they were miserable with it the other 22 hours of the day. Some literally begged us to remove it.
What’s the solution? We found simple techniques that wrap both the amputation site and waist with soft bandages to be effective. In the operating room, plaster splints are initially incorporated in the bandage over the amputation site as a rigid dressing to protect against bumps and bangs. Softer wrapping material comes up over the hip and around the waist. The hip can move more freely, and this also allows for exercises, leg lifts and stretching. It’s not rigid enough to support a foot attachment and allow the person to put weight on it, but it’s much more comfortable. This bandage typically is changed sometime between three and five days after surgery. The person is then fit with a shrinker sock that includes a waist belt. The shrinker sock is an elastic garment measured specifically to fit the length and shape of the amputated limb and to apply gentle compression more at the end of the limb than at the top of the limb. To further control swelling and decrease pain, the person learns massage and towel-pulling exercises. In towel pulling, a towel is draped over the end of the amputation site, and the person holds the ends with each hand and pulls the towel against the end of the amputated limb. This pumps out some of the edema to reduce swelling, and many people say it also lessens pain. They tell me, “It’s a good hurt. It’s sore when I’m doing the towel pull, but it feels so much better when I’m done.”
Another major focus of our immediate postoperative care is to prevent contractures, which are the loss of range of motion at one or more joints. Specifically with a transfemoral amputation, people have trouble with hip contractures from the shortening and wasting away of muscle fibers. For some transfemoral amputees, the hip becomes locked forward in a flexed position. This can make it difficult, sometimes even impossible, to fit the leg with a prosthesis. A helpful exercise to prevent contractures is to stretch the hip backward into extension. The best way to stretch the hip is to lie on your stomach for five to 10 minutes, staying flat at first and later using your hands and arms to push your shoulders, chest and torso up so that your back is arched. Those of you who practice yoga will recognize this as “The Cobra” position. This sounds simple enough, but it’s not that easy for some people, especially those who’ve developed “a little extra” in the belly. Some people haven’t lain on their stomachs in years, and this exercise can be a real challenge for them. At times like this, they don’t think of their therapist as “Mr. Wonderful” or “Ms. Fabulous,” to put it mildly. It’s tough. But hip flexibility really counts so we focus on stretching and encourage folks to do this two or three times every day.
A Note From the Doctor
I had intended this series on transfemoral amputations to be presented in three parts. But as this project has moved forward, it has become increasingly apparent that there are so many aspects to this amputation level – both during surgery and afterward – that it would be a disservice to limit the scope of this discussion in any way. Therefore, it has been expanded to four parts to include discussion of other important issues. The next article will discuss the sometimes-difficult choice of when, or even if, to use a transfemoral prosthesis and other personal, family and ethical concerns. The final article on the transfemoral level will look in-depth at various socket designs, suspension systems and the wide range of new and older prosthetic components.
“Technology presumes there is just one right way to do things and there never is.” – Robert M. Pirsig, author
Next: Mastering the Vital Skills & “When Can Grandpa Get His Leg?”
[/tab] [tab title=”Part 3″]by Douglas G. Smith, MD, Amputee Coalition Medical Director
Part 2 of this series on the transfemoral (above-knee, or AK) amputation level examined surgery and postoperative care. This article will look at the importance of mastering a set of vital skills before a prosthesis is prescribed. It will also look at whether life without a prosthesis might be the right choice for certain individuals. Part 4 of this series will examine high-tech and low-tech sockets, suspension systems and parts.
Before the Prosthesis
Amputations in the thigh and hip place much more challenging demands on a person than do those in the calf or foot. For an individual with a transtibial (below-knee, or BK) amputation who retains good use of the knee, a prosthesis can make it easier to transfer and to get from a sitting to a standing position. Having a natural knee joint with all of its wonderful power makes a prosthetic device helpful even for someone who never remasters walking. The prosthesis can provide a point of contact with the ground for balance and support, and the person still retains the knee power needed for transfer activities. In the lower amputation levels, the person often starts working with a prosthesis very soon after surgery.
But it just doesn’t work that way for transfemoral amputees. A prosthesis for an amputation in the thigh or hip does not really help with transfers or in rising from a sitting to a standing position because the leg no longer has knee strength. Since the prosthesis doesn’t help with lifting power, we ask that people demonstrate or develop sufficient strength in their other limb, torso, pelvis and arms. That strength is needed to get the body up and over the prosthetic device, and added strength in the thigh and pelvis are fundamental to making a transfemoral prosthesis work safely.
Because people with high-level amputations in the thigh and hip areas are at greater risk of falls and injury, they should safely master a set of vital skills before a prosthesis is ordered. They should be able to do the following:
- Transfer independently, both in and out of bed and on and off of the toilet
- Go from a sitting to a standing position independently
- Walk in parallel bars or with a walker for at least 25 feet.
To illustrate how difficult it is to lift yourself using only one knee, try this: Sit in a chair. Now, raise one foot off of the floor and try to lift yourself out of the chair using the other leg. Hard, isn’t it? Most people can’t accomplish this without using their arms to push themselves up out of the chair. Can you see how important it is to have the power of both knees to push yourself up?
People with transfemoral amputations have not only lost their knee with its marvelous lifting power, but they are faced with learning to use a prosthesis that works very differently than the leg that they lost. Because there are no muscles or motors inside the prosthesis, body weight can go through the prosthesis to the floor only when the knee is fully straight or, for some knee units, within 5 to 10 degrees of full extension. When rising to a standing position, people with a transfemoral amputation must bear all of their weight on the sound leg, which greatly affects their balance. If they try to put weight onto their amputated limb while their prosthetic knee is still bent, the prosthesis may buckle and collapse. Once they are fully upright with their knees extended, however, weight can then be transferred through the amputated limb.
We never say that these people absolutely cannot obtain or use a prosthesis. But we do ask that they demonstrate the strength and skills necessary to use one safely.
Some people have asked me whether having a prosthetic leg will help them accomplish the vital skills. “Actually, a prosthesis will not make it easier to perform these skills,” I have to tell them. “If you can’t do them without your prosthetic leg, you won’t be able to do them with it.” I sometimes call a transfemoral prosthesis “a bit of an anchor” because its weight, bulk and long lever actually make it tougher to master these skills. Amputees shouldn’t simply be given a transfemoral prosthesis and sent off with it. The training is much more demanding than it is for lower-level amputations.
The time frame for meeting the vital preprosthetic goals can vary tremendously, depending on the individual and his or her general health and physical fitness. Young, healthy people who lose a limb to trauma or tumors often master these skills within one or two days. Most elderly people also master these skills in a very short time. Patients who have severe multiple trauma or major medical problems, especially those who’ve had strokes, heart attacks or are limited by other medical conditions, might need much more time to heal and rehabilitate. Unfortunately, some people are just not capable of accomplishing these goals because of disease or infirmity.
“When Can Grandpa Get His Leg?”
Deciding precisely when to prescribe a prosthesis for a person with a transfemoral amputation can be difficult. Usually, the person and his or her family are eager to get a prosthetic leg to help the new amputee move forward with his or her life. They don’t understand why the prosthetic fitting should wait until the person has mastered the vital skills – independent transfers, going from a sitting to a standing position, and walking in the parallel bars for 25 feet.
I clearly remember two very loving and caring young women who pleaded with me to prescribe a prosthesis for their grandfather, a transfemoral amputee who’d previously had a stroke and was confined to a wheelchair. They were convinced that a prosthetic leg would enable him to transfer and walk, allowing him to leave the nursing facility. “If you’d only give him a leg, then he can walk and come home,” they told me. I talked with them about the three steps, and then we tried to see how safely their grandfather could do a simple transfer from his wheelchair to a low examination table. He was unable to do it without all three of us helping him.
So, I emphasized the three-skills set. If he mastered them, then we could talk about prescribing a prosthesis. But when they returned six weeks later, they fully realized that their grandfather just wasn’t going to be able to do it. And after talking with other amputees and watching people use a transfemoral prosthesis, they finally understood why it would not be wise for their grandfather to have a prosthetic leg. For him, it would be “an anchor.” Attempts at walking would likely result in falls and possible fractures. And because he spends so much of his time in a wheelchair, the top of the socket would press uncomfortably into his groin and buttock, increasing the risk that he’d develop pressure sores.
The lesson they learned is that the prosthesis does not make it easier for transfemoral amputees to transfer or go from a sitting to a standing position. They need a significant amount of strength in their arms, their other leg, their pelvis and their trunk to rise to a standing position and to use a transfemoral prosthesis effectively and safely. And that’s why the three preprosthetic goals were developed. They establish criteria for when it will be safe for a person to begin working with a prosthesis.
Inaccurate Assumptions and Unclear Expectations
Another unfortunate misconception may occur if amputees or their family members believe that the doctor or the insurance company is preventing them from obtaining a transfemoral prosthesis because of cost. I’m not saying that this doesn’t happen at times, but it is not automatically the reason why. Usually, the reason the doctor hasn’t prescribed a prosthesis for them is that they have not yet mastered the preprosthetic skills.
When people think the doctor and healthcare system are “just being mean,” it creates an adversarial mindset. “They know what I need; they just won’t give it to me.” Everyone benefits when amputees and their families know about the need to master the vital skills. Even for individuals who master these skills in the first few days following surgery, understanding these concepts is important. Everyone has a better understanding of what ought to be accomplished to safely undertake a prosthetic fitting.
Providing a prosthesis too soon for an individual with a high-level amputation can backfire with devastating results. It can be emotionally shattering for a person to get a prosthesis and be unable to use it. It’s also very hard on the person’s loved ones. The common misconception is that the device will solve all of the problems. But when the device arrives and the problems still persist, they look at each other in confusion, asking, “Who failed?” In reality, nobody failed. Inaccurate assumptions can lead to unclear expectations. There is perhaps a misunderstanding over whether the amputee must do something to make the device work or whether the device will do the work for the amputee. The person makes the device work; the prosthesis doesn’t make the person walk.
Unfortunately, it has become increasingly common for physicians who don’t fully understand amputation rehabilitation and prosthetic devices to write a prescription that simply says “artificial leg.” They may write that prescription for a transfemoral patient who hasn’t mastered the preprosthetic skills or they may write an inappropriate prescription for a device that is either too simple or too complex. Then the prosthetist and therapist are faced with the ethical dilemma of attempting to build and fit a limb and to train a person who is physically unprepared to meet the challenges of using this new device. Or, it’s left to the prosthetist and therapist to explain to the disappointed patient and his or her family why it isn’t the right time to begin using a prosthesis. Or, worse, the person ends up in a frustrating situation of failure.
When people realize that prosthetic devices for amputations at the transfemoral and hip areas demand more of their users, they understand that it’s not simply a matter of “get up and go.” Much more training and physical therapy are required than for amputations below the knee. Remember the person in Part 1 whose amputation was revised upward from transtibial to transfemoral? He said it was “10 times more difficult” being a transfemoral amputee. When it comes to physical therapy and training, it can take 10 times longer to make the transition and really learn to use a transfemoral prosthesis. Prosthetic devices for people with amputations in the thigh are fascinating engineering models. They replace two joints – the knee and the ankle. But they demand a lot more of their users. Only through very open discussions can people realize that the most ethical, the safest, and the most helpful course is to be absolutely clear about the need for mastering the vital skills.
Matching People With Technology and Societal Obligations
Appropriately matching the right person with the right prosthetic technology is quite complex. It’s probably one of the biggest challenges we’re going to have to face in the next decade as technology advances by leaps and bounds – along with its costs. Figuring out who can really benefit from new technology and how society wants to pay for it is not easy. Some people can get a lot of use out of it. Others don’t need a lot of technology and prefer simpler mechanics and reliable function.
Similarly, we’ve struggled for decades over the question of when to prescribe power wheelchairs vs. manual chairs. Recent headlines have emphasized the rising costs of power chairs. Medicare payments for power wheelchairs skyrocketed from $289 million in 1999 to more than $1.2 billion in 2003 (Reference 1). And this leap doesn’t even include a new technology called the iBOT, which is a wheelchair that can go over inclines and up and down stairs. An iBOT costs $29,000 (Reference 2), and some say Medicare’s obligation for total iBOT costs could reach as much as $30 billion (Reference 3). So while many people might benefit from technological advances, not all wheelchair users need it, and the costs are significant.
As with wheelchairs, choices about transfemoral prostheses involve matching people with the right device. An analogy I like to use is the VCR. Are you going to use it to record, rewind, fast forward, adjust the TV’s settings, set the clock, etc., or are you happy to just push Play? Does the person need a prosthesis for a variety of functions or for simple things? Some people love the newest models and can’t wait to try out every setting and function. For others, though, there is nothing like the reliability and durability of simpler, tried-and-true systems. They know they can count on “old faithful” to do the job.
As you will see in Part 4 of this series, knee units have made a great technological leap with microprocessors. We’re already struggling to match knee unit technology with each person. Imagine the next leap when we add not just microprocessors but motor control and the power to go from a sitting to a standing position. What if the price goes up another tenfold? How are we going to manage that? We want to help everybody, but economic factors can’t be ignored. As William F. Buckley Jr. has noted: “Idealism is fine, but as it approaches reality the costs become prohibitive.”
Rehabilitate Without a Prosthesis?
We also should understand that it’s okay if some people choose to rehabilitate without a prosthesis. Sometimes, people feel influenced by others or pressure from within themselves to use an artificial leg when they don’t want to. It’s not mandatory. The prosthesis is there to be used when it makes life easier. But there shouldn’t be pressure to use one if you don’t want to or aren’t quite ready for it. A person has the right to say, “It’s not for me.”
I’m often fascinated by patients who tell me that they choose not to use a prosthetic leg when they’re home alone but use it when they’re out with family or friends. For some, it’s not that they want or need to use it; instead, they’re trying to make everyone around them feel more emotionally comfortable! They feel social pressure to wear a prosthesis.
Others tell me that they do not feel comfortable in public without a prosthesis because it makes them feel self-conscious and “different.” Also, it’s not unusual for people with limb loss to experience times when they can’t wear a prosthesis because their residual limb is swollen or bruised or there’s a blister. For those who would never dream of leaving home without a prosthesis, a blister or soreness that prevents them from wearing a prosthetic leg can be a jail sentence. Each time they cannot wear their leg, they sentence themselves to lockup in their own homes. Peer pressure and social forces truly can be intimidating.
Some think that prosthetic rehabilitation follows amputation surgery just as surely as summer follows spring. But we should not make someone feel like a failure simply because he or she chooses not to use a prosthesis. In an ideal world, rehabilitation should address comprehensive functional living both with and without prosthetics. Prosthetics can be overemphasized, while other important information falls through the cracks. I get the impression that many people really want the freedom to use a prosthesis when it’s helpful and not feel that they have to use it when they don’t want to. Many people, through choice or circumstance, can benefit from learning to manage their lives with and without a prosthesis. We want to encourage everyone to wear a prosthesis that might be useful. But if you choose not to use one, that’s okay too.
“Man never made any material as resilient as the human spirit.” – Bern Williams, author
- 1. Bloomberg.com ( www.bloomberg.com )
- 2. Independence Technology, a Johnson & Johnson company ( www.independencenow.com )
- 3. The Hill newsletter ( www.hillnews.com )
Next: The Transfemoral Amputation, Part 4: Great Prosthetic Components Are Good, but a Good Socket Is Great
[/tab] [tab title=”Part 4″]by Douglas G. Smith, MD, Amputee Coalition Medical Director
I intended our discussion of the transfemoral amputation level to be comprehensive, insightful and helpful. It certainly has turned into a marathon. There are so many elements and nuances to this common high level amputation that I thought it would be a disservice to readers to skip over any topics or touch on them too briefly.
Parts 1, 2 and 3 of this series covered topics ranging from preoperative issues through recovery and rehabilitation. In this part, we’ll focus on prosthetics, sockets and suspension. Technology is helpful and often marvelous, but it’s still comfort that counts.
Finally, in Part 5 of this series, we will examine why walking is particularly challenging for individuals with transfemoral amputations. In addition, we will offer some thoughts on both the expected and the unforeseen consequences of technological advances.
The Prosthetic System
When discussing the transfemoral prosthesis, it is important to consider four major aspects of the system: the socket, the suspension, the components and the alignment.
• The Socket: This is the part of the prosthesis that attaches it to the body and largely determines whether the fit is good or not. It’s what holds the prosthesis to the person and enables him or her to make the foot and knee units work. Almost every transfemoral amputee I’ve met believes that it is the most important aspect of the prosthesis.
• The Suspension: This is the method used to attach the prosthesis to the body. Successful suspension keeps the prosthesis from falling off and prevents excessive motion of the residual limb, such as slipping, sliding, rotating, or pistoning up and down, inside the socket. It also helps prevent bell-clapping, which is the phrase we use when the residual femur (thigh bone) moves around inside the socket like the clapper in a bell. Good suspension, together with a good socket, holds the femur in the right position.
• The Components: These are the parts that replace the various anatomic structures of the lower limb, such as the knee and foot, that were lost at birth or through amputation. These parts range from simple to very complex and are often what people focus on most. Improvements in the design of and materials for prosthetic foot, ankle and knee components over the last several decades have been truly amazing, but to really appreciate the advantages of technologically advanced components, the amputee must have a good socket and proper suspension.
• The Alignment: This is the unique way everything fits together – the way the socket, foot and knee are put together in three-dimensional space. Proper alignment ensures that the person isn’t too bowlegged or knockkneed and that the prosthetic knee doesn’t buckle when the person stands. Proper alignment means getting the prosthetic knee under the socket in the right spot and the prosthetic foot uniquely positioned beneath the knee and the socket. Good alignment allows the components to accept and support body weight during the “stance phase” and to bend fluidly as the prosthesis moves through space during the “swing phase.” (The swing and stance phases will be more fully described in Part 5 of this series.)
Though all of these aspects are involved in a successful prosthetic system, in survey after survey, amputees identify a comfortable, well-fitting socket as the most important. That’s why we say, “Great prosthetic components are good, but a good socket is great.” A comfortable socket is almost incalculably more important than the fanciest prosthetic parts (knees, feet, etc.) in the world.
Sockets: A Continuing Evolution of Design and Materials
As noted previously in this series, the transected femur can support very little weightbearing at its end. The socket is therefore designed to shift weight up onto the side of the thigh and the pelvis to take weight off the end of the limb. Though no one should underestimate the importance of a good socket fit, many people often do. In fact, there can be a tendency to focus so closely on prosthetic parts that the significance of socket comfort is overlooked. Some may think that a specific part – such as the prosthetic foot or the prosthetic knee – is the major factor in overall function following a transfemoral amputation, but I believe that socket fit and quality are much more important. A great prosthesis doesn’t work great if the socket doesn’t fit and the alignment is not right.
Socket shapes have changed over the years. During the 1950s, there was an evolution to the quadrilateral socket. This design has two chief physical characteristics:
• The socket looks square when viewed from the top.
• It contains a contoured area for the ischium (part of the hip bone) to sit on called the ischial seat.
At first glance, you might think, “The thigh’s not shaped like that. It’s not square. What good is this socket?” But the socket is specifically designed to be narrower from front to back (anterior to posterior) to hold the residual limb back, keeping the ischium up on the ischial seat. The individual actually sits up on the back rim of the socket. To accomplish this, the socket must be higher in front than in back. There’s a downside, though. The high front wall of the socket often digs uncomfortably into the groin area, especially while the person is sitting. But if the front wall is lower, the leg slides forward and the ischium falls off the ischial seat. Sometimes, it’s a no-win situation.
Transfemoral sockets began to change dramatically in the 1970s and ’80s. Most sockets now are narrower from side to side (medial, the inside part of the thigh, to lateral, the outside part). The ischium, instead of sitting up on top of an ischial seat, is contained down in the socket. The femur, rather than sitting straight in the socket, is tipped inward to distribute some of the weight onto the lateral side. This is called adduction. Adducting the femur also helps stretch the hip abductors (butt muscles) a little, making them stronger and improving their mechanical advantage. If the femur is not secure and it drifts out, these muscles are mechanically weaker. Also, when the femur is tipped in, more weight can be put on the side of the thigh, and the hip muscles are positioned to provide better balance.
The quadrilateral socket is commonly called the quad socket, and all sockets that are narrower from side to side, medial to lateral, are called narrow ML sockets. While the majority of sockets today are ML designs, there are still many successful quad fittings and many good reasons for some people to continue using the quad design. While there’s a tendency to think that a newer model must be better, it might be better or it might just be different. When the ML socket came out, many people who used quad sockets wanted to change to the new model, assuming, “It must be better because it’s new.” But some people who were doing fine with the quad socket changed to the newer design and had trouble. “Best” is what works best for you.
Not only have the shapes of sockets evolved, so have the materials they’re made of. Many of the initial sockets were made of carved wood. Then came leather and metal. Aluminum followed steel to reduce the device’s weight. Rigid plastics and laminates followed. Most recently, plastics have advanced to become both flexible and durable. This enables sockets to rigidly support some areas and still allow for muscle motion and more flexible support in others. There are also combinations of an inner socket that’s made of a flexible material and a rigid frame that has open spaces, which allow the brims to be a little more pliant (easily bent).
Traditionally, transfemoral sockets have been made with walking in mind, and all of the design changes have focused on holding the prosthesis securely while the person is standing up and in motion. However, the optimal shape for walking is not the best shape for sitting. A transfemoral socket molds up to or around the ischium – the part of the hip bone that we sit on – to transfer weight when the person is upright. But because of this construction, the socket can dig uncomfortably into the groin and buttocks when the person is seated. To this day, unfortunately, none of the sockets are really designed for sitting. If a socket were made to be comfortable while sitting, it might not provide the stability and support needed when standing. Technically, it’s hard to design one socket that’s optimal for both sitting and standing. The newer sockets that combine rigid and flexible materials are a start in the right direction. Socket design is an ongoing evolution, however, and most would acknowledge that we haven’t solved all of the problems.
While sockets are better now than they were when they were carved out of wood, some transfemoral amputees still can’t get a comfortable socket fit. Many of these amputees might agree with these words from Thomas Edison: “I have not failed. I’ve just found 10,000 ways that won’t work.”
Suspension: Keeping the Socket Attached
Regardless of design and materials, all sockets must have secure suspension to keep the prosthesis from falling off. Some sockets are made of softer plastics, some are composed of laminates, and still others are constructed of carbon fiber. Soft or rigid, all of these sockets need to be held on. The following are commonly used types of suspension:
• Suction valve
• Elastomeric roll-on liners with locking pins
• Soft straps or belts that go around the waist (the TES Velcro belt or the Silesian band)
• A rigid belt that securely grabs the pelvis area and uses a mechanical hip hinge to hold the limb on and support the pelvic area.
In the traditional suction valve suspension system, as the residual limb goes into the top of the socket, air is forced out through a one-way valve at the bottom. This creates a vacuum between the skin of the residual limb and the inside of the socket. When the limb is pushed all the way into the socket, the skin at the top of the thigh forms a seal with the plastic of the socket. Because air cannot get back into the socket through the valve unless it’s deliberately released, the vacuum that’s created prevents the socket from falling off. This is called negative pressure, and it keeps the socket securely attached to the limb.
This suction valve suspension can fail, however, if there’s not a good intimate fit between the top of the thigh and the socket where the skin and plastic seal is formed. If there’s a dramatic weight change or a person’s tissue has too many folds, air can slip in the top, eliminate the negative pressure, and cause the socket to fall off. While suction valve suspension is successful for many people, it doesn’t work for everyone.
Roll-on locking liners were introduced more than 15 years ago and have really improved in recent years. The liner is still most typically connected to the socket by a distal pin lock. But like many things, the locking pin is not perfect. The pin concentrates many forces at the very end of the residual limb and causes a pistoning-suctioning effect that can be likened to a cow’s udder during milking and may produce swelling and tenderness. Edema fluid, skin discoloration and ulceration can result. Up to one-third of the people using a distal locking pin for suspension simply cannot tolerate the stress on their tissues. People have put cloth, mesh and other types of reinforcement at the end of their liners to try to lessen the uncomfortable pistoning-suctioning forces, but the results have been mixed. Some people who have failed with distal pins feel bad because they think they did something wrong or that something is wrong with their residual limb. But there’s no fault involved; it’s actually a fairly common occurrence.
As noted in the section on sockets, when something new comes along there’s a risk of forgetting about the benefits of previous designs. For example, a patient recently told me that he hadn’t known it was possible to use a prosthesis without a roll-on liner. The roll-on liner was the only form of suspension he’d been told about. After struggling for years with a roll-on liner and pin, however, when he tried the older suction valve system, he had great success. He had been introduced to what was perceived as the new and better technology, but when it failed, no one had attempted to help him return to the tried-and-true method. He didn’t even know about it. When he did learn about it and try it, it worked. To avoid such situations, healthcare providers need to make their patients aware of advances in design, while at the same time reminding them of the benefits of the older, tried-and-true methods.
Other methods are being explored to attach roll-on liners to the socket for those who can’t tolerate a pin. Alternatives include side-locking strips that work a bit like ski buckles and vacuum-assisted suspension in which a little pump is used to develop a vacuum between the liner and the socket. These new systems are helpful, but we’re still growing in our understanding of which system is appropriate for which person. If only something like “Electronic Velcro” existed, we could just flip a switch and a small battery current would make the liner stick to the socket. To remove it, we could just flip the switch off and the socket would come right off. Someday, we may be able to secure gel liners to the entire surface of the socket, not just at one or two points.
For people who have difficulty with suspension, securing the prosthesis up around the waist is the next step. First attempts are always with softer materials, including neoprene, different types of cloth, and leather. One part of these soft suspension belts securely grasps the prosthesis, and the other part wraps around the waist, often above the belt line, where it is then cinched with Velcro or buckles.
Some people want something more solid than the softer suspension belts, and hip hinges and rigid belts may help these people feel more confident. A very rigid band that grasps the opposite iliac crest (hip) and a mechanical hip hinge may give them the feeling that the prosthesis will stay on and the hip will track properly. While this form of suspension adds weight to the prosthetic device and can be cumbersome, for some it provides a secure feeling of suspension that leads to success.
“When you’re prepared, you’re more confident. When you have a strategy, you’re more comfortable.” – Fred Couples, PGA golfer
Next: Doc, Walking Is Not as Easy as It Looks
[/tab] [tab title=”Part 5″]by Douglas G. Smith, MD
In the fifth and final part of our series on the transfemoral (above-knee) amputation level, we discuss some of the challenges and complexities of walking. We then examine the functions of the prosthetic knees and feet for transfemoral amputees and some new technological advances. Finally, we outline some thoughts on deciding whether you’re a high-tech, lowtech or no-tech type of person.
Swing and Stance
When we walk, one foot or the other is always in contact with the ground. Each leg is constantly transitioning, going from standing and supporting our weight to swinging through from behind to in front of us to get ready for the next step. The legs are always transitioning from stance to swing, which is why our walking motion is divided into what we call the “swing phase” and the “stance phase.”
The stance phase begins with “heel strike,” when your heel initially contacts the ground out in front of you. The foot then transitions into “foot flat,” when your weight comes over your foot. The knee is almost straight. As your body passes over the foot, your heel starts to rise behind you, and then your knee starts to bend. When just the tips of your toes are touching the ground behind you, you’ve reached the end of the stance phase.
Now you’re transitioning into the swing phase. Your knee continues to bend, your toes come off the ground, and your heel keeps rising behind you. As you move your pelvis and thigh forward, your prosthesis swings from behind you to underneath your body, all in a bent position. Finally, your leg swings out in front of you and your knee straightens so that when your heel touches the ground, your leg is straight and ready to accept your weight. You’ve reached the end of the swing phase and are transitioning into the stance phase again when your heel hits the ground.
There also are brief periods of time when both feet are on the ground and both legs are accepting some weight. Looking closely at this brief phase of our stride, we see that the toe of one foot is touching the ground while the heel of the other foot is also on the ground. That brief period of time is called “double limb support.”
Conversely, when we run, there are short intervals when both feet are off the ground. The definition of going from walking to running is that our gait changes from a pattern with a moment of double limb support to a pattern where both feet are briefly off the ground and we’re literally up in the air for a split second. In running, there’s no longer any double limb support. In fact, there’s just the opposite; there’s aperiod of no leg support. We’re actually airborne.
Examine your own stance and swing phases. You may be surprised at the intricacies involved in each step we take. Walking is something most of us do without much thought; it’s virtually automatic. But when you examine each phase of the stride, you will see what small, but complicated, interconnected motions are involved in getting one foot in front of the other. Our bodies really are biomechanical marvels. Many patients have told me that one of their major frustrations following a transfemoral amputation is the difficulty they have in learning to walk again. They’ve lost the physical parts that make these complex and intertwined motions automatic and subconscious. Bringing this complicated process back to the conscious level of thought requires a lot of work, but don’t get discouraged if progress comes more slowly than you’d like. As the philosopher Stanislaw J. Lee noted, “He who limps is still walking.”
Prosthetic Knees and Feet
The major differences between prostheses for a person with a transfemoral amputation and those for a person with a transtibial (below-knee) amputation are the knee unit and the foot. First, we’ll examine the knee unit and how it functions. At the end of this section, we’ll discuss feet and the erroneous concept that a prosthetic foot designed for a person with a transtibial amputation would also be optimal for a personwith a transfemoral amputation.
The simplest prosthetic knee joint is a basic hinge. Adjustable friction can be added to this hinge with the friction tuned so that swing phase occurs very smoothly at one walking speed. Next, weight-activated brakes can help prevent the leg from buckling when in stance phase. Knees with weightactivated brakes used to be referred to as “safety knees.” Now, they’re called “stance-control knees.” While these friction knee systems work well for people who walk at a single speed, big problems can occur for individuals who walk at different speeds.
When you’re walking slowly or if the friction is set too tight, your knee unit doesn’t bend enough when your toes come off the ground behind you, and your prosthetic foot will trip against the floor as your prosthesis swings under you. There simply is not adequate distance between the ground and your foot to complete the stride without tripping. Also, if the friction is too tight, your knee won’t straighten out in time at the end of the swing phase, your leg won’t get into position in front of you quickly enough for proper heel strike, and your knee will buckle because it cannot support weight while bent. You can spot those people whose knee friction is too tight. To avoid dragging their toes, they bring the prosthetic leg out to the side in a kind of half circle to keep from tripping. This is called circumduction.
A single setting can also be a problem when you’re walking faster or if the friction setting is too loose. Then your foot comes up a little higher than it should behind you during heel rise, and your leg snaps forward too strongly in front of you during follow-through. The leg reaches an exaggerated extended position too soon in the swing phase, and that makes it awkward to complete the stride comfortably. The prosthetic side appears to be bending far too much behind and snapping straight much too early in front. It looks very awkward.
To control these unwanted occurrences, prosthetic limbs were fit with hydraulic or pneumatic regulators. Hydraulic systems use liquid while pneumatic systems use air to control friction by speed. The faster a person brings the thigh forward, the more friction there is to control the lower leg. Friction prevents the leg from snapping forward too quickly. Conversely, the more slowly you move the same knee unit, the easier the motion. Think of a bicycle pump. If you push down on the handle very slowly, it moves smoothly and easily. But if you try to shove it down quickly, air resistance kicks in, and it takes a lot more exertion to move it. If a person with a prosthetic knee tries to walk really fast, it’s like pushing the bicycle pump down quickly. It will go, but it takes a lot more “oomph” to get it to move. It’s more resistant so the leg will slow down. When the person walks slowly, there’s less friction so the unit moves smoothly and the leg is where it is supposed to be throughout the stride. Hydraulic and pneumatic control units allow smooth gait at very different walking speeds.
Stability is very important during the stance phase and has improved over the years, thanks to slightly different technological advances. The initial advances involved a friction brake mechanism inside the unit. The more weight you put on it, the more resistant it was to buckling. With the weight unloaded, it became free to flex again. If your knee did not give freely after a certain point, you could not sit down without your leg sticking straight out in front of you. Then some units were designed so that the knees won’t buckle even when the loading happens with the knee bent between 5 and 15 degrees of flexion. This established an added range of stability and safety against buckling.
The next evolution has been to control the knee functions withmicroprocessor and computer control. Instead of having a setting only for speed, microprocessors can also instantly interpret the knee position and the loading forces so that the friction is constantly adjusting throughout the swing and stance phases. The older knee was in swing phase unless there was weight on it. Then as the little brakes were applied, it would go into stance phase. The newer knees are mostly in stance phase to prevent the person from falling and convert to swing phase just when the person loads weight onto the toe and also starts putting a bending force on the lower leg. The microprocessors sense all of these forces and allow the knee to then swing freely.
The newer microprocessor knees are much more resistant to buckling, and my patients tell me they have fewer incidents of stumbling and falling with them. I believe that these microprocessor knees are a great advance and have helped many individuals, young and old alike. While the current microprocessor knees certainly add improved control, another advance in knee units is still needed – a motor that provides lifting power. We’re headed in that direction, but we’re not there just yet.
A tremendous variety of prosthetic feet are available. With so many models, I wonder why people automatically assume that the type of foot that works best for a transtibial amputee would also be the best for a transfemoral amputee? It’s often not the case.
Jacquelin Perry is a renowned researcher from Southern California who was a physical therapist before she became one of the first women orthopedic surgeons in the United States. As she points out, many people with a transfemoral amputation prefer a prosthetic foot with enough ankle motion to get to “foot flat” quickly. Transfemoral amputees can have a greater sense of stability when the foot is flat against the ground. Elastic response feet preferred by many transtibial amputees don’t have the bending characteristic necessary to get to foot flat quickly. They’re just too stiff. Not only could a more flexible foot help some individuals with a transfemoral amputation have a better sense of contact with the ground, it could also allow a smoother transition from heel strike to toe off during the stance phase of gait. Conversely, Dr. Perry points out that the increased ankle motion that helps many transfemoral amputees often seems too soft or too mobile for many transtibial amputees. Their needs and desires can be different.
Technology: The Expected and the Unexpected
It can be quite difficult for a person with transfemoral limb loss to walk on uneven surfaces and up or down slopes, ramps or stairs. Transfemoral amputees have to spend more time thinking about walking and scanning the terrain than do people with most other lowerlimb amputations. They are always onthe lookout for dangerous situations that might make them stumble or fall.
The newer microprocessor knees overcome some of the difficulties in walking on nonlevel surfaces, especially down hills and down stairs. And while these technological changes are improvements, measuring the impact of technology can be difficult. Physically, it’s clear to see when someone is walking more symmetrically than not. In a gait lab, we can measure the forces at work while walking. But, interestingly, we’re finding that having to consciously think about walking and issues such as stumbling and falling is more important than we had ever realized.
For many of us, walking is automatic without any real conscious thought. But as we’ve discussed, a person with a transfemoral amputation must think more about walking, especially on uneven surfaces or in unfamiliar areas. Different environments can bring different and sometimes hazardous challenges. It’s one thing to take a walk alone on an even, smooth path. It is quite another to navigate an area like an airport concourse, where people are walking at a great variety of speeds, stopping and starting, and coming at you from all directions. You have to make countless adjustments to your gait as you’re headed to or from your plane.
Technological advances have made it possible to better meander through situations like this. I know a female executive with a transfemoral amputation who does a lot of work-related travel. She says that airports used to be full of possible pitfalls because of crowds, turns and changing speeds. She says she really had to focus on walking when she got off the plane and headed for baggage claim. After she switched to a new knee unit with microprocessors, however, she found herself free to think about other things – where to find ground transportation, which hotel she was going to, reading signs and notes. She could concentrate on other things, unlike before when most of her mental energy was focused only on walking.
Technology can also free a person for the unexpected. Many transfemoral amputees do very little talking while walking because they must concentrate on both the mechanics of walking and the environment. Interestingly, one person who converted to a microprocessor knee told me that before she made the change she and her husband rarely talked while walking because she had to concentrate on walking. She says her husband really enjoyed those silent, contemplative strolls. Now that she’s converted to one of the new microprocessor knees, her bubbling personality comes out while they’re walking. Though her husband appreciates her newfound freedom, she says that he sometimes wonders what happened to the peace and quiet he used to enjoy on their walks.
These last two scenarios illustrate that the new technological advantages are not always obvious or easy to measure. When thinking about walking, most of us tend to focus on energy, the number of steps a person takes during a typical day, and other things of this nature. But the real value might be in minimizing stumbling and falling and freeing people to think about other things while walking – like listening to what your spouse is saying, for instance.
“The difference between a good walker and a bad one is that one walks with his heart, the other with his feet.”
– William Henry Davies, poet
High-Tech, Low-Tech and No-Tech Solutions
The recent decades have brought tremendous technological advances aimed at improving quality of life and ease of motion. Therefore, many people assume that the latest and greatest technology is always the best. Though technology offers solutions for problems, however, it’s important to keep in mind that there isn’t a single answer for everything. One knee system is not right for everybody. One socket system isn’t perfect for everyone. There isn’t a single suspension system that does the job for all. When it comes to people, there are high-tech, low-tech and no-tech kinds of folks. Remember our earlier analogy of the VCR. It can come with a wide array of options, but many of us are content to just push play, stop and rewind.
High-tech products are developed to solve problems, but they generally come with several “costs.” While cost is usually measured in dollars, the biggest impact on a person can be the emotional cost: the anxiety and fear that something will go wrong with the new technology, for example. Then there’s the “fiddle factor” – how often do I have to mess with this thing to make it work right? Circuits may go bad. What if the electronics get soaked in the rain? Batteries have to be plugged inand replaced so what happens when it runs out of “juice”? Is this new technology convenient for me? There’s a learning curve. You can’t just plug it in, push a button and go. Many new microprocessor legs are adjusted early in training, but later the software settings need to be readjusted as the person becomes more proficient and uses the device in different ways. It’s kind of like computer software upgrades. As you learn to use more and more of your computer, you have to keep changing the settings. Something that’s high-tech and fancy can require more work than something that’s simple but reliable.
“Computers are magnificent tools for the realization of our dreams, but no machine can replace the human spark of spirit, compassion, love and understanding.”
– Louis Gerstner, retired CEO, IBM
Other solutions might seem less “glamorous” because they’re not high-tech, but they’re stable and durable. There’s less gadgetry, fewer maintenance problems, and you can count on them to work when you need them. Some individuals simply love to rely on “old faithful.”
Ideally, each of us would have just the right amount of technology so that it helps us with our needs but doesn’t overwhelm us with its demands. Technology should be tailored to each person, and there’s a real art to finding the right balance. Some people even prefer not to use any technology at all.
One of the challenges in this next decade will be coming up with suggestions and protocols to appropriately match the right technology and right prosthetic design to the right person. We need to figure out who’s going to do better with a quad socket than with a narrow ML socket. Who will do best with which knee unit? As for feet, there currently are more kinds of prosthetic feet on the market than you can count. Unfortunately, there are very few guidelines that actually say which foot is the best match for a specific person’s needs. One size does not fit all.
There’s a vast spectrum of high-tech, low-tech and notech solutions and products, and each person is unique. I’m a big believer in technology. I think it does make our lives better, but I also realize that there can be practical reasons for doing things one way versus another. What Bob likes doesn’t work as well for Joe. And Mary’s preferences are different from Betty’s. One of the secrets to success following a transfemoral amputation is matching each person with the right technology or understanding a person’s desire to go forward with no technology at all. It’s your body. What’s best for you?