Computerized Prostheses—

Advanced Artificial Limbs Intended to Restore Normalcy

By Andrew Gorosko

A Trumbull firm is offering some people who have lost portions of their limbs an opportunity to better adapt to their handicaps through the use of advanced, computer-controlled prostheses, which approximate the functioning of legs and hands.

BioMetrics, which also has offices in Danbury, Waterbury, and Torrington, designs, constructs, and custom-fits prostheses, which are replacement limbs. The firm also provides orthoses, which are external devices such as braces, to help to manage limb and spinal dysfunction.

Prosthetic and orthotic devices should be comfortable, easy to manage, and allow for maximum efficiency of movement while providing stability, according to BioMetrics.

BioMetrics President Robert Dzurenda said that the technical advances in the field of prosthetics have been rapid. Progress has been so rapid, in fact, that technical improvements to artificial legs and hands have now outpaced some medical insurance companies’ willingness to pay for such devices, he said.

Some private medical insurance firms, which formerly paid for the computer-controlled prosthetic devices, do not now pay for them because the companies do not consider such advanced devices to be “medically necessary,” Mr Dzurenda said. The public Medicare insurance program is evaluating whether it should continue providing coverage for such devices, he said.

The devices are costly. An artificial leg for people who have had amputations above the knee, known as a C-Leg, costs about $45,000. A computer controlled myoelectric hand costs about $25,000. Hopefully, the cost of the devices will drop in the future, Mr Dzurenda said.

The C-Leg, which is short for computerized leg, provides people who have had leg amputations above the knee with a means to approximate the gait that they had had before they lost their limb, Mr Dzurenda said.

The C-Leg employs a computer-controlled hydraulic system, which is regulated by internal feedback, to create a gait as normal as possible for its user.

Sensors located within the foot section of the artificial limb route electronic signals on the changing relative positioning of that foot to the upper joint of the device, which serves as a surrogate knee for the artificial leg’s user. A compact hydraulic system lies between the device’s artificial foot and artificial knee. Through continuously variable joint-tensioning, the C-Leg regulates and coordinates the overall action of the artificial limb to approximate a natural walking motion.

The computerization of the artificial leg relieves a patient of some of the conscious, deliberate effort that is needed to walk by people using artificial legs, Mr Dzurenda said. The C-Leg is powered by a battery that must be recharged daily.

The C-Leg is made by Otto Bock Health Care, a prosthetics manufacturer. BioMetrics custom fabricates the carbon-fiber laminate fitting, or socket, that C-Leg users wear to connect themselves to the C-Leg, Mr Dzurenda explained.

Most of the prosthetics patients that BioMetrics have are diabetics, who are over age 50 and who have had leg amputations below the knee, Mr Dzurenda said. It is much simpler to use such lower-leg prostheses than prostheses that join the body above the knee, such as C-Legs, he noted.

Good candidates for a C-Leg are physically active people in their 20s, and older, who have had amputations above the knee, often due to traumatic injuries, he said.

BioMetrics can reprogram the functioning of a C-Leg to vary the degree of mechanical advantage provided by the device, thus customizing the action of the C-Leg to meet a patient’s current physical condition and his or her individual skill in using the C-Leg, Mr Dzurenda said.  

Myoelectric Hand

Patients who are using a myoelectric hand prosthesis subtly regulate the muscle flexion in their arms to operate the three artificial digits on the hand, Mr Dzurenda said. Myoelectric hands may be used either by patients who have arm amputations below the elbow, or amputations above the elbow. Controlling such an artificial hand is more complex for those with amputations above the elbow.

Mastering the actions of a myoelectric hand requires much practice, Mr Dzurenda said. Technologists currently are working to develop artificial hands whose mechanical action would be controlled  by the subtle sounds created by muscle flexion, he noted.

Myoelectric hands are more sophisticated than earlier versions of artificial hands that patients have used to grasp objects, he said. Those artificial hands are controlled by mechanical cables.

Like the C-Leg, the battery that powers a myoelectric hand must be recharged daily.

Due to the inherent complexity of the computer-controlled legs and hands, BioMetrics is selective in deciding which amputees will be good candidates for using the artificial devices, Mr Dzurenda said.

But “nothing replaces a human body part,” he noted.

How well people adapt to computer-controlled limbs hinges on their motivation to succeed, Mr Dzurenda said. Thus, BioMetrics uses a “team approach,” coordinating its prosthetics work with the needs of the patient, the patient’s family, and the patient’s doctor.

Mr Dzurenda explained that a 21-year-old man who had had his leg amputated above the knee following a motorcycle accident was so motivated to succeed that he was able to walk using a C-Leg on the day that he received it. The man began walking down stairs within the first month of receiving the leg, Mr Dzurenda added.

BioMetrics has had patients who have lost legs in motorcycle accidents return to motorcycling after they gain confidence in using their C-Legs, Mr Dzurenda said.

The increased use of all-terrain vehicles has resulted in more accidents with amputations, creating a group of people who may need BioMetrics’ services, he said.

Each year, BioMetrics fits about a dozen patients with C-Legs, and fits several people with myoelectric hands, Mr Dzurenda said. Some patients may be fitted in two C-Legs in the case of double leg amputations.

Flesh-colored silicone coverings, which mimic the appearance of actual limbs, may be used to  disguise the mechanical aspect of C-Legs and myoelectric hands.