Walking as an Amputee
The goal of amputee prosthetics for the lower extremity is to mimic the normal gait pattern as much as possible. The normal human gain is complicated and more than just putting one foot in front of the other. There are various phases of the normal human gait that must be accounted for so that the amputee with a prosthesis can walk without much of a limp.
One of the biggest problems in amputee walking is that the good limb is often weakened from disuse. Before the individual can make good use of a leg prosthesis, the normal leg must be strengthened through physical therapy so as to be of maximum use to the patient.
There are three different kinds of feet prostheses:
- Anatomic foot prostheses
- Biomechanical foot prostheses
- Dynamic foot prostheses
Each type of foot prosthesis is different in the amount of flexion and extension the foot can provide at the level of the ankle and on the amount of pressure put on the heel as it strikes the ground. When walking, the heel strikes the ground first and then the ankle flexes forward (called plantar flexion) in order to put the entire foot on the ground so the opposite foot can lift up and make another swinging motion to create a normal gait.Trans-tibial AmputationsThese are also called “below the knee” amputations; they rely on the knee to flex during a normal gait pattern and on the strength of the quadriceps muscles in the front part of the thigh to hold the knee strongly as it goes through the motions of flexing and straightening out during a normal gait pattern.
The hip and gluteal muscles of the butt must be strong enough to maintain a normal gait. Most of the time, the gluteal muscles act normally when a person has had a below the knee amputation; however, it is required to flex the hip about 10 percent more than a normal gait in order to walk relatively normally.
The normal leg must do more work when dealing with a single leg amputation, taking on more body weight during walking than in a normal gait. In fact, it has been shown that both the good leg and the amputee leg must be much stronger than normal in order to create a normal gait pattern, even in a trans-tibial amputation. Trans-femoral AmputationsIn such cases, the individual loses knee function and ankle function, making the effort of walking all that much more difficult. Hip muscles tend to weaken when the patient has had an amputation above the knee and these must be strengthened in order to have as normal a gait as possible. Care must be taken before actually walking on the leg to make sure the hip doesn’t get contractures before the person learns to walk with a prosthetic device. Strengthening of the gluteal muscles is also an important aspect of having a normal gait following amputation.
The prosthetic device used in knee amputations must allow for flexion of the knee during the swing phase of walking and then extension and locking of the knee when the leg has reached the floor. Above the knee amputations involve a great deal more energy expenditure than below the knee amputations, so strength of the good leg and of the gluteal muscles of the bad leg must be maximized before an acceptable gait can be maintained.
More than 80 percent of leg amputations done in the US are from poor circulation in peripheral vascular disease or from diabetes. These patients have the added disadvantage of not having strong muscles and good circulation to the opposite leg so that often, the amputation of the legs tends to be bilateral. Less than 10 percent of amputations result from trauma to the lower extremity—in part due to advances in salvaging the limb lost to trauma so that an amputation isn’t necessary. Most amputees of the leg are between 55 and 75 years of age, and more and more extremely elderly people are getting amputations due to diseases of the lower extremity.
One goal the surgeons have in doing an amputation is to preserve the knee if at all possible. Walking with a below the knee amputation is much easier and uses much less energy than above the knee amputations. Fortunately, the practice of amputation surgery has advanced to the point that more than 60 percent of all lower limb amputations are below the knee.
Most of the rehabilitation programs designed to get a leg amputee back to walking with a prosthesis have been designed for young people when most of the amputations are done in older people. This can be a problem because it means that the frail elderly person with an amputation often fails to do very well with a leg prosthetic device and usually ends up in a wheelchair.
Those that do learn how to walk with a prosthetic device for the amputee often sacrifice speed in order to be able to walk. Above the knee amputations involve a much slower walk when compared to below the knee amputations. Only young people who have required an amputation due to trauma actually stand a chance of walking at a normal speed and this is usually only the case for below the knee amputations.
The endurance of an amputee’s gait is not very high as there is a lot more energy needed to walk with a leg prosthesis. Only young people with below the knee amputations were able to improve the number of steps per day using physical therapy. In the end, age was a great factor, with 44 percent of people in their sixties developing the ability to walk and a drop to ten percent of people in their seventies having the ability to walk. Virtually no one in their eighties was able to accept a prosthetic device in order to walk with the device, despite therapeutic interventions.
In order to help ambulation, a number of people with an amputation use some kind of walking aid, such as a cane or walker. These things further slow down the rate of ambulation but can be useful around the home, where gait can be slower than they need to be when the patient is in a public situation.