Arm Prosthetics

There are new developments in the arm prosthetic field that enable functional fittings:  The MyoHand VariPlus Speed®, the MovoShoulder Swing shoulder joint and the MyoEnergy Integral battery for adults as well as the MyolinoWrist 2000 for children.

The Mind-controlled Arm Prosthesis

A sensational new development from Otto Bock can be seen for the first time in Germany at the ORTHOPÄDIE + REHA-TECHNIK trade fair: A prototype of the unique mind-controlled arm prosthesis. The first user of the intelligent arm outside of the USA is the young Christian Kandlbauer (Steiermark, Austria) who has both arms amputated and is now working again at his former employer as a warehouse clerk. 

After an amputation of an arm, the nerves are functional up to the amputation point. These nerves can grow into a new muscle and bring about contraction. This principle is nature’s “repair mechanism” where the lost ability for muscle contraction is restored.

The idea of Targeted Muscle Reinnervation (TMR) involves artificially introducing this repair mechanism. A muscle that no longer functions due to an amputation is surgically divided into several segments. The original supply of nerves of this muscle is separated and used for growing the nerve ends. This procedure is called targeted reinnervation. After reinnervation, the muscle contracts according to a new scheme that relates to the movement of the phantom arm. If the prosthesis follows the same movement exactly as the phantom arm, it is referred to as intuitive control: The prosthesis user controls the prosthesis with his mind. 

Surgery must be carefully planned. Patience is required after surgery as the nerves must first grow in the new muscles. This takes about one day per millimetre. A targeted muscle build-up starts after three to six months according to current knowledge.

After this training, the patient can control a prosthesis with a considerably higher degree of functionality. The orthopaedic technician produces a prosthesis socket that securely fixes the prosthesis to the body. The socket should restrict the patient as little as possible and ensure that the electrode contacts for EMG conductance lie securely on the skin. The artificial arm is attached to the socket and covered cosmetically.

Artificial arms that exploit the described usage to the full extent exist as prototypes. The patient uses a modified standard prosthesis as an everyday prosthesis that consists of serial parts. This arm has only three active joints but enables the patient intuitive control and provides a significantly higher usage.

The MyoHand VariPlus Speed® is a new development that combines the mechanical properties of the SensorHand Speed® and the control versions of the DMC VariPlus system electric gripper. Objects are precisely and quickly grasped by a high gripping force and speed. Six different control programs can be selected.
 
Objects must be specifically fixed and positioned by muscle signals as the electronics do not automatically readjust the gripping force. For this reason, Otto Bock recommends VariPlus Speed® particularly for patients with a low amputation level. A significant advantage for the hand is that the patient can establish a gripping force of up to 130 N. Speed and gripping force can be adjusted.

MyolinoWrist 2000 is a mechanical friction wrist. It is compatible with all four sizes of the Otto Bock electric hand 2000. The wrist is available with a lamination ring or for gluing in the prefabricated components. The wrist gives children prostheses an additional degree of freedom. The hand can be flexed up to an angle of 30° combined with a hand rotation in all directions. The level of friction is adjustable. The multitude of position options prevents compensation movements.

MyoEnergy Integral is a built-in battery with magnetic receptacle. This battery can be very flexibly integrated between the inner and outer socket in a number of ways due to its flat and variable installation height. The associated MyoLoad Integral battery charger is connected via a charging plug with a permanently installed charging receptacle of the built-in battery.
 
2 Li-ion cells with a capacity of 600 mAh are used for energy storage. The two cells are attached side by side and are connected to each other by a hinge. The two cells can also be positioned independently of each other after removing the hinge.

This shoulder joint is suitable for passive arm prostheses such as for high-tech fittings. The free swing of up to 40° also allows bilateral amputees to have a natural gait pattern and reduces the pressure load in the shoulder cap region.

The lock can be activated or lifted by specific movements of the upper body or the hand at 30° in the anteversion. The abduction up to 20° provides a pleasant sequence of movements for many daily activities particularly for movements close to the body and/or activities when sitting. Additional control elements are required for this.