The Heidelberg Arm (Heidelberg Pneumatic Prosthesis)
William A. Tosberg, C.P.&O. *
On February 12, 1957, Dr. Henry Kessler had invited a group of interested people to attend a demonstration of the Heidelberg Pneumatic Arm Prosthesis. The large auditorium of the Kessler Institute in West Orange, N.J., was filled with representatives of all the professions working for the rehabilitation of the physically handicapped when Dr. Kessler introduced Dr. Ernst Marquardt and Engineer Otto Hafner.
In his introduction. Dr. Kessler pointed out the differences in the prosthetic prescription for a leg amputee and an arm amputee. Whereas the artificial leg is primarily filled to the stump, a prescription for an arm must consider the whole amputee to a much greater degree. The replacement for a lost hand normally poses a relatively simple problem functionally, but tremendous difficulties face the prescription team when it becomes necessary to fit a bilateral above-elbow amputation or even more so if the patient has had to be amputated at the shoulders. The greatest problem is the lack of power sources to activate the different components of the prosthesis. Cineplastic operations in some cases have provided additional force. Small electric motors have been used in the I.B.M. arm and also in the Vaduz arm. Now Dr. Marquardt was to discuss a prosthesis that utilized carbon dioxide.
Dr. Marquardt traced the development of the Heidelberg arm, staling that it bad become imperative for Germany to improve the utility of prostheses provided, since, through the influence of war and because of the many industrial accidents, Germany was faced with 2,000 bilateral amputees who depended upon highly functional devices to become and remain self-sufficient. It was Mr. Otto Hafner. a mechanical engineer, who used highly compressed gases to activate the different joints in an artificial arm. These gases, compressed to a fluid state, are stored in an aluminum cylinder under a pressure of 45 atmospheres. By means of a reducing valve, the gases enter into a pneumatic system at a pressure that can be varied from 0 - 5 atmospheres. Through a series of microvalves the gases are routed to the different joints where they perform the function of some of the amputated muscles.
A number of slides shown during Dr. Marquardt's remarks illustrated some of the many functions possible with amputations at different levels. Mr. Walter Pavelchek, a certified prosthetist from Kessler Associates, demonstrated a Heidelberg Pneumatic Prosthesis for above-elbow amputation which had been fitted to a bilateral A.E. amputee only a few days before. This man had worn a standard arm previously and he had had only three hours of actual wear in which to become accustomed to the different actions of his new device. Although some of his motions appeared awkward, it was apparent that he was able to perform some tasks that had been impossible for him to do before he received the new arm. Outstanding was the active rotation of his forearm. This motion is so essential for many activities of daily living, such as eating, dressing and many toilet activities.
A film, made at the training center at the University of Heidelberg, showed a number of bilateral amputees during their training process. The day starts with general body conditioning after which a semifinished prosthesis is applied and functional exercises are performed at training boards. Eating and drinking are practiced as well as vocational skills in many fields. The film shows the construction details of several arms for different amputation levels. In one construction the remaining pronation and supination of the forearm is insufficient for normal rotation but is utilized for prehension of the hand. Where there is active forearm rotation, prehension is controlled by muscle valves placed over muscles that normally control wrist flexion and extension. These muscles have to be isolated and strengthened through training supervised by physical therapists. In above-elbow amputations the biceps and triceps muscles may be utilized in addition to scapular excursion. Mr. Hafner explained that the pneumatic system allows an almost limitless combination to activate the different motions. From viewing the film, it appears that most bilateral above-elbow amputees were fitted with only one functional arm. The metal containers were built into a dress arm on the opposite side. The film closed with a showing of several amputees at the farewell dinner which always is staged at a public restaurant and is enjoyed by the amputees in the presence of their wives or friends. It was apparent that no psychological problems connected with their disabilities existed with the group shown in this film. Dr. Marquardt also demonstrated several working models of the arm in order to show the many functions which can be obtained by the use of compressed gases.
A general discussion which followed the presentation brought out the fact that the container for the gas weighs less than one pound and lasts for about four days with average use. It can be refilled in about one minute from a master container which is provided for every amputee. The cost in Germany of a functional arm plus a dress arm for a bilateral shoulder disarticulation is about $700.00 in American money.
The writer had an opportunity to attend a demonstration during a recent visit to Germany in the interest of the International Society for the Welfare of Cripples. At that time I saw prostheses operated by men with different levels of amputations. Some of the arms had been worn for six years with only a replacement of the plastic tubes that distribute the gas to the different controls. I was told that presently about 80 arms are in constant use.
It is my impression that the Heidelberg Pneumatic Arm Prosthesis is an ingenious device to add to the function of the severely disabled. Its main advantages over any other artificial arm known to me are its excellent control of the many functions, its powerful motion at all joints and the normal appearance of these motions.
A disadvantage, at least from an American point of view, might be the type of hand used, its general bulkiness and the need for replenishing of motor power at rather frequent intervals. Despite these apparent disadvantages, the arm seems to have many indications especially in the bilateral amputee where it has definite merit.
It is hoped that through the visit to America which was arranged by Dr. Kessler in cooperation with the World Veterans Fund and the International Society for the Welfare of Cripples, the inventors will benefit further through their contacts with the main limb fitting centers maintained by members of the Orthopedic Appliance and Limb Manufacturers Association, by the Army and the Prosthetics Research Board. Only by such international cooperation will all amputees benefit from the work carried on in many parts of the world.