Experiences With The Hepp-Kuhn Below-Elbow Prosthesis A Preliminary Report

Raymond J. Pellicore, M.D.

The "thalidomide" episode of 1961-62 stimulated tremendous interest in the limb deficient child and accelerated research in prostheses and other rehabilitation measures both here and abroad. In West Germany, where the incidence of "thalidomide" children was very high, a noteworthy advance was the expedited development of externally powered arms for severely handicapped patients (amelias and phocomelias), which has received wide attention.

Less well known in this country, perhaps because it was originated prior to the "thalidomide" catastrophe, is the "Muenster" arm developed by Drs. Oscar Hepp and G. G. Kuhn which also represents a valuable addition to prosthetic restoration. Techniques for the fabrication of both above-elbow and below-elbow prostheses have been developed by Drs. Hepp and Kuhn. This preliminary report presents our initial experiences in applying the "Muenster" below-elbow technique to child amputees.

The most common congenital skeletal limb deficiency is the terminal transverse partial hemimelia (Meromelia: terminal transverse; radius M, ulna M) which presents an amputation-like short below-elbow stump. Of 319 congenital amputees treated in our clinic, 191 are of the below-elbow type. In addition, 58 children with acquired below-elbow amputations are under our care. Not all of these below-elbow amputations, of course, fall into the very short classification, the group for which we have found the "Muenster" arm to be of greatest value.

Three Necessities

Function, comfort and cosmesis are the three most important necessities of good prosthetic restoration but it has been extremely difficult to achieve these goals with the very short below-elbow prostheses in common use during the past decade. Typically, this prosthesis has incorporated a split socket and step-up hinges. This combination left much to be desired from the cosmetic standpoint. Functionally, it was usually possible to obtain a full range of elbow flexion (135°) but this was achieved at the expense of a considerable loss of power. The weight of a Dorrance hook did not present a serious problem but the patients experienced difficulty in flexing the forearm when a functional hand was provided.

The split socket was later superseded by the pre-flexed forearm which represented a great improvement over the split socket cosmetically, although the hinges and triceps pad were still bulky and detracted from the appearance of the prosthesis. Functional forearm lifting power was increased but at the expense of range of motion, the average maximum being 100 to 110°. When well fitted, prostheses were comfortable except during the very hot days of Summer. Unfortunately, heat discomfort still remain* a problem with the German arm. When a prosthesis causes discomfort to the wearer, even though it may be very practical and useful, it is usually relegated to the closet. Female amputees, of course, are the exception - they are willing to accept considerable discomfort if cosmetic appearance can be improved.

Fitting Technique

In the fabrication of the "Muenster" arm, the socket is pre-flexed approximately 35°. The posterior aspect encloses the olecranon and fits snugly above it. A channel is provided for the biceps tendon at the antecubital space. When the wrap cast is made, the elbow should be positioned in approximately 90° of flexion. The posterior aspect of the cast is carefully molded over the olecranon and the biceps tendon sharply defined in the antecubital space. Securing an intimately fitting socket is critical in the "Muenster" technique. If the molding of the biceps tendon is not done satisfactorily, the anterior wall of the socket must be extended too high in the antecubital space, thus decreasing the amount of flexion that can be obtained. As we gained experience in the fabrication of these prostheses, we were able to obtain more and more flexion by improved channeling for the biceps tendon, as will be indicated in our case histories.

All our fittings were accomplished without use of stump socks and, in the majority of cases, greasing of the stump was necessary before the prostheses were applied. When the socket is properly fitted, it is almost impossible to pull it off the stump.

In the Hepp-Kuhn fitting technique, the harness played a negligible role in the suspension of the prosthesis. Thus, a simple axillary loop around the opposite shoulder can be used for activation of the terminal device, instead of the conventional figure of 8 harness (Fig. 1 ).

Since the line of the cable and housing is from a proximal retainer located near the elbow, to the axilla loop at the opposite shoulder, impingement on the axillary portion of the shirt presents a problem for boys. In these instances, a posterior retainer located on a strap fitted around the biceps is necessary to raise the cable (Fig. 2 ). Other means to accomplish the same end have been devised by ingenious prosthetists. Fortunately, girls do not experience this difficulty, since they can wear loose-fitting blouses. The cable is usually carried along the lateral side of the prosthesis, but we have found no contraindication to installing it medially.

Favorable Reports

Cosmetically, this prosthesis is a marked improvement over those previously used. This improvement, plus the elimination of hinges and a portion of the suspension harnessing, is particularly pleasing to our female patients and their parents (Fig. 3 ). Reports concerning comfort are also favorable. The majority of the patients offered no complaints after more than a month of wear, except during extremely hot weather, and this discomfort was anticipated because of the close fitting.

Functionally, a vast improvement in flexion power was noted, especially in boys, but the added weight of a functional hand is still a major problem for the girls. Several children reported improved sensory feedback as a result of the intimate socket fit. One of the prime drawbacks, especially in the early fittings, was limitation of flexion. However, as skill in the fabrication of the prosthesis improved, the range of flexion obtained also improved. It has been our observation that a minimum of 90° of flexion should be obtained in fitting the average short below-elbow patient. In slightly longer stumps, a maximum of 110° of flexion has been secured. Limitation of extension has not presented a problem.

The major contraindication to the use of "Muenster-type" below-elbow prostheses is bilateral amputation. Since it is extremely difficult to insert the stumps into the sockets unaided, wear of the prosthesis by a bilateral below-elbow amputee is virtually impossible.

Nine children have been fitted with the "Muenster-type" below-elbow arms at the university of Illinois Clinic thus far and arms for two additional children* are being fabricated. Of the nine children fitted, eight have typical congenital very short below-elbow "stumps" (2" to 2 3/4"), and one has an acquired below-elbow amputation, with a (3 3/4") stump.

Five members of the group originally wore split sockets and were later fitted with preflexed sockets. Four wore pre-flexed sockets as their first prosthesis. Three of the children are girls and six are boys. The longest period of wear is seven months, and the shortest is six weeks. As would be expected, the boy with the 3 3/4" stump has the greatest range of motion. Our experiences are described in the five case histories which follow:

Case One

Diane Wilson, who is now seven years old, is a congenital, very short below-elbow amputee. She was initially fitted at the age of 20 months, with a split-socket prosthesis which provided 135 of forearm flexion. Diane wore units of this type until January 1964, when she became the first child in our clinic to be fitted with a "Muenster-type" prosthesis. At the first fitting with the German arm, her range of motion was from 25 to 70 of forearm flexion. After modification to the prosthesis, the range was increased 20° (25° to 90° of flexion).

Diane has always been an excellent wearer and wears her German arm almost as much as she previously wore the split socket prostheses. She develops a rash on her stump periodically, but wears the prosthesis throughout the day unless it causes her great discomfort. In this event she removes the arm for varying periods of time to relieve the discomfort and then resumes full-time wear when the rash heals.

In response to a questionnaire, Diane reported that she strongly preferred the German arm because it felt lighter and more a part of her person. The arm appeared more natural when it hung by her side and when she walked and was not as bulky at her elbow as was the split socket previously worn (Fig. 4 ).

The only negative comment offered by Diane and her mother was that she was unable to perform some of the things she had previously done, such as coloring and weaving, because of the limitation in forearm flexion. Dressing herself had also become slightly more difficult. It is our feeling that Diane could be provided with an additional 10 of flexion with better fitting prostheses.

Case Two

Richard Jones, who is now nine years of age, was first fitted with a prosthesis at the age of six years (Fig. 5 ). He is a congenital short below-elbow amputee and had previously worn a preflexed below-elbow prosthesis. His flexion range with his old prosthesis was 25° - 125°, virtually 100° of motion. In January, 1964, Richard was fitted with a German-type prosthesis. When first fitted with the ngw arm, his range of motion was 75°(from 20° to 95° of flexion). Lowering the antecubital trim line increased maximum flexion to 105° without effecting the limitation on extension, thus providing 85° range of motion.

The patient reported that the German arm was more like a natural arm, with fewer straps and hinges. However, he complained that he could not scratch his nose or head and was not able to comb his hair adequately. He also remarked that in warm weather the arm socket felt "icky" inside.

Case Three

Dennis Smith, a short below-elbow amputee, age eleven years, was originally fitted with a split socket at the age of six-and-a-half years. Two-and-a-half years later, he was fitted with a preflexed socket. His range of motion with his preflexed arm was from 25° to 120° of flexion. He was fitted with the German-type prosthesis in July, 1964, and it is too early to make a full evaluation of the outcome. His range of motion with the German arm is from 20° to 110° of flexion.

Case Four

Raymond Swabowski, age eight years, is a short below-elbow amputee. He was fitted initially with a split socket at the age of 13 months and with a preflex-ed socket at the age of six-and-a half years. He wore his preflexed arm virtually all of the time and was considered to be an excellent wearer. However, he was very unhappy with his German-type prosthesis, fitted in June of this year. Both he and his parents objected to it and expressed a desire to go back to the preflexed socket with the triceps pad and elbow hinges.

Raymond complained that his arm sweated tremendously and that he had difficulty in applying it. He objected to the need to carry a jar of vaseline to regrease his stump whenever the prosthesis had to be taken off and reapplied; as, for example, when he went swimming. He said that his ability to bat a ball and hold things when riding his bike was reduced with the "Muenster" arm. Raymond's range of motion with his new prosthesis was from 25 to 90 of flexion. He was the only child in our group of 10 who did not like the German arm and wished to go back to his old prosthesis.

Case Five

Denise Tanner, another short below-elbow amputee, was fitted initially at the age of 27 months with a preflexed forearm. Her range of motion was 25° to 100° of flexion. With her new German arm fitted in July, 1964, at the age of eleven years, she had 10° to 65° of flexion. Since Denise was accustomed to a limited amount of motion with the preflexed arm, she did not offer any strenuous objections to the further limitation imposed by the new prosthesis. However, in her case, as with some of the others, I am certain that the range of motion could be increased with improved fabrication. It is interesting to note that despite the limitations of the German arm, Denise and her mother still preferred it to the prosthesis previously worn.


Eight of the nine patients already fitted with the "Muenster" arm definitely preferred it to the prosthesis they had worn previously. Their parents expressed a similar preference. The girls were willing to tolerate the limitation of motion and the discomfort from heat to secure the benefits of improved cosmesis. The lightness of the arm, as compared to their previous prosthesis, and the reduction in harnessing, were other advantages frequently mentioned by the children and their parents.

* Both of these children have congenital very short below-elbow stumps, 1" and 1-1/2" in length respectively. They were initially fitted with elbow-disarticulation prostheses and previous attempts to convert them to below-elbow prostheses, preflexed or split socket, were unsuccessful. Fittings with "Muenster" arms have been completed since the original manuscript of this report was submitted. The ranges of flexion motion achieved were: for the 1" stump 45° to 95°, and for the 1-1/2" stump 25° - 65°.

Raymond Pellicore is Co-Chief of the University of Illinois Amputee Clinic, Chicago, Illinois