Myoelectric arm prosthesis

An industrially manufactured prosthetic hand is located at the end of the socket. It is selected depending on the individual needs of the prosthesis wearer. We supply our patients with prosthetic hands from different manufacturers. There are two primary classifications for prosthetic hands:

• System hand
• Multi-articulating hand

System hand:

The basic unit of all myoelectric system hands is a functional grasping unit that opposes the thumb with a two-finger group (index and middle finger). The system hand performs a "pincer grip". The gripping unit is covered by a soft plastic shell in the form of a hand. This shell provides both shape and load-bearing capacity and is typically covered by prosthetic glove.

Multi-articulating hand:

Multi-articulating hands contain individual motors in all fingers that enable precise, natural grasping. The fingers or finger joints can be moved individually. In addition to the pincer grip, many other grip types can be set (cylinder grip, three-point grip, index finger, etc.). In contrast to the system hand, the thumb of a multi-articulating hand can be used in lateral and opposition positions.

All prostheses are equipped with an on/off switch. This prevents loss of power or unintentional opening of the hand (e.g. when carrying a bag).

Prosthetic hands function in different ways:

• Myoelectrically controlled prosthesis with passive rotation of the hand:

Opening and closing of the hand occurs via a muscle signal, while rotation to the desired position is performed by the users opposite hand.

• Myoelectrically controlled prosthesis with active rotation of the hand (pronation and supination):

Opening and closing, as well as rotation in both directions, are each performed via a specific muscle signal. A rotation insert is integrated into the prosthesis for this purpose.

• Myoelectrically controlled prosthesis with electrical rotation of the hand (pronation and supination):

Opening and closing of the hand occurs via a muscle signal. The electrical pronation and supination is switched by slight rotational movements of the residual limb via a rotation control.

• Myoelectrically controlled prosthesis with electrical rotation of the hand (pronation and supination) by means of four-channel control:
  
  Opening of the hand occurs via a muscle signal. A stronger contraction results in a higher muscle signal, the system automatically switches from opening and closing to rotation (pronation and supination). A weaker contraction brings the system back to the first function. Another switching option is the so-called "co-contraction", i.e., briefly tensing both muscle groups brings the system from one function to the other.
   
• Pattern recognition system:

Prosthetic hands with pattern recognition have a high level of functionality (e.g. wrist rotation, wrist flexion, various grips, grip patterns, individually controllable fingers). In this case, the hand is directly controlled by the trained muscle signal (no compensatory control). The hand learns to interpret the user's individual movement patterns and assigns them to a specific prosthetic movement.

The electrically-powered gripper can be exchanged for the myoelectric hand. It works like a pair of pliers and has the shape of a hook. The gripper is intended for rough activities with high demands (e.g. agriculture, housework, manual work).

The electrodes built into the socket detect the muscle signals from the residual limb muscles. For this reason, it is important that the electrodes lie on the skin. A potentiometer amplifies the voltages of the muscles, which are in the Myo-Volt range, up to 50,000 times.

Each myoelectrically controlled prosthesis has a rechargeable battery that serves as the energy source (depending on the hand system, these are 11.1 or 7.4 volt batteries - 4.8 volts for children's hands).

In most prostheses, the battery is built into the prosthesis, so the entire prosthesis is connected to the charger for charging.

With other prostheses, the battery is in an insert frame and can be replaced. In this case, it is recommended to always keep a charged battery in reserve, as the battery may not last the entire day. For safety reasons, only the original batteries may be used.

If your prosthesis has a removeable battery, you will also receive a battery charger from us. This is connected to a 220 volt power supply. The charger must not be used to charge other batteries. Please make sure that the battery is only inserted into the charger in the correct position. Improper handling will lead to defects of the accumulator and the charger!

With the switch on the side, the charger can be set to "operation". A red signal light indicates that the battery is charging. If even a charging time of 4-5 hours does not improve the function, please contact your orthopedic technician. The charger must be secured against falling, impact or operating errors, as this can lead to defects.

For prostheses with integrated rechargeable batteries, a charging socket is located on the socket. To charge the prosthesis, simply plug the supplied cable into the charging socket. The scale shows you how far the battery is charged. Please observe the specific manufacturer's information on operating the charger.

The prosthetic glove replicates the anatomical structure of the hand and gives the prosthetic hand a natural appearance. It is available in many color variations.

Multi-articulating hands are usually worn without a glove, as gloves may cause functional restrictions.