Experiences With The Hepp-Kuhn Below-Elbow Prosthesis: A Follow-Up Report

Raymond J. Pellicore, M.D. Sally Mier, O.T.R. Robert C. Hamilton, M.D. Claude N. Lambert, M.D.


Every preliminary report, in our opinion, demands a follow-up or final report with the original impressions reaffirmed, modified, or denied. Therefore, we would like to follow up our initial preliminary report of September 19641 and present our experience covering approximately five years' use of the Muenster technique in fitting unilateral below-elbow amputees at the University of Illinois Amputee Clinic. We trust that this report will serve to supplement and perhaps modify the information contained in the comprehensive and detailed review of the Muenster-type prosthesis published by New York University in March 19672, and the other excellent articles which have appeared in the ICIB on the same subject 3,4.

While the socket we use is fabricated by techniques virtually the same as those published in the NYU manual, certain minor differences exist in the finished prosthesis when it is presented to the amputee. Only two of the patients fitted with Hepp-Kuhn prostheses have worn stump socks-one initially and the other three years after the initial fitting. One of the cases used a triceps pad. In the remainder, no additional suspension was used.

Two of the cases in our series had acquired amputations; the remainder had congenital deficiencies. No bilateral amputees were fitted with Muenster prostheses.

One child made a direct change from a split socket to a Muenster fitting. (Split sockets have not been ordered in our Clinic for the past six years.) Another child with a one-inch below-elbow stump was fitted as an above-elbow amputee prior to being fitted with a Muenster prosthesis. Only one case included in this report had been previously fitted with a Hepp-Kuhn socket. The remainder made the transfer from preflexed sockets, triceps pads, a variety of hinges, and figure eight harnesses. It is interesting to note that the child who sustained one of the greater losses of motion and socket freedom by transferring from a split socket to a Muenster-type fitting is still wearing her prosthesis five years later; yet those with losses of lesser degree, e.g., changing from preflexed arms to Muenster fittings, frequently cited "loss of motion" as the reason for rejection. Is this report then to be accepted as valid? It has also been noted that as the prosthetists became more familiar and proficient in the fabrication technique, the reduction in forearm flexion decreased appreciably.

All those who were fitted with the German-type arm, whether they accepted or rejected it, were in general agreement on certain points, as was the therapist doing the evaluation. Other reports have also concurred in the majority of these conclusions:

  1. Control-system efficiency, never a problem in any type of below-elbow fitting, was equally as good and in many instances slightly better with the Muenster fitting.

  2. The requirements for terminal-device opening, also never a problem in below-elbow fittings, were met for all positions.

  3. As would be expected live-lift capability showed an enormous increase, as compared to a split socket, and also a significant increase was found in comparison with a preflexed socket.

  4. Socket slippage with an axial load showed a marked decrease. In most cases slippage was nonexistent with a well-fitted German-type arm.

  5. A loss in range of motion was typical. In all but one instance, where the Muenster arm was substituted for a previously-worn prosthesis, there was some loss in range of motion. In this one instance the gain was two degrees, while the losses varied from five degrees to 47 degrees. However, our experience cannot be absolutely equated with other reports as we have never fitted medium or long below-elbow amputees.

  6. In our series, perspiration was a great annoyance, especially during warm weather. In many instances it was necessary to use a lubricant in order to don the prosthesis. Again we cannot equate our experiences with other reports since only two of our wearers used stump socks. Perhaps we should use this stump sock technique in the future, or modify the prostheses of patients whose major complaints are heat and perspiration. In conjunction with perspiration, we had several instances of skin irritation which, however, responded readily to treatment. In only one case was this condition the primary reason for rejection of the prosthesis. Holes in the socket ameliorated but never fully eliminated these complaints.

  7. Socket retention was much better because of the intimate fit necessary for successful application of the Muenster prosthesis.

  8. Virtually all patients liked the simplicity of the harness system and the freedom from suspension straps. Even the boys who required a modification of the "low take-off" preferred this aspect of the prosthesis. It also afforded much greater freedom of shoulder movement.

  9. For all the girls and their mothers, cosmesis was the most universal, desirable attribute of the Muenster arm. As the saying goes, "the boys couldn't care less."

  10. Olecranon pressure was seldom a problem with the girls, but with the boys the reverse was true. The more active the boy, the more annoying the olecranon pressure became.

Even though our fitting technique, theoretically, was more intimate and critical (without stump socks except for the two cases cited), the life of the prosthesis for those who accepted the arm varied from 16 to 30 months. Perhaps this discrepancy with the NYU report can be explained by the fact that only two of our cases had acquired amputations while the remainder were of congenital origin. The bulbous stump of the patient with a congenital defect is not conducive to shrinkage, and the decreased stimulus to the epiphysis, due to the shortness of the stump and associated musculature, results in less longitudinal growth.

Statistics

Twenty-nine children from our Clinic were fitted with Muenster prostheses. Seven are excluded from this report because of lack of adequate follow-up. The remaining 22 consisted of twelve boys and ten girls (see Table 1 ). In 20 patients the limb loss was of congenital origin; only two being of traumatic etiology. Both of these latter were boys. Stump lengths varied from one to four inches. Follow-up periods ranged from a minimum of 11 months to a maximum of 59 months.

Eleven children (nine boys and two girls) rejected the prosthesis emphatically and totally. Length of wear varied from two to 17 months, the average being three months. However, this is not a very valid statistic since, at our insistence, many in this group wore the prosthesis much longer than they desired. It can readily be surmised from our statistical chart that our persuasiveness did not always prevail. Two wore their prosthesis two months; one, three months; and a fourth, four months.

All of the children rejecting the prosthesis were excellent wearers, both before and after their interlude with the German arm. All were very active children who participated in sports, music, and numerous extracurricular activities. The reasons most often given for the rejection were: "too restrictive," "too hot," "uncomfortable," "too much pressure on arm (olecranon)," and "too difficult to put on."

In one child the results were indeterminate. Although he accepted the prosthesis, he was such a poor wearer generally that in our opinion it would not be statistically valid to categorize him as either an acceptance or a rejection. This boy (C.H.) incurred fractures of both forearm bones while pole vaulting, developed gangrene, and was amputated at the age of 14 years. He had a 3-1/8 inch stump and was fitted at the age of 16 years with a preflexed socket which was then changed to a Hepp-Kuhn prosthesis when he was 18 years of age.

Eight girls and two boys have accepted the German-type prosthesis and continue to wear it. All are good to excellent wearers. They have been wearing their prostheses from 11 to 59 months, the average length of wear being 33.6 months. One of the boys in this group (R.J.) was fitted with a Hepp-Kuhn arm at nine years of age. He has never participated in any sports or virtually any other activities typical of the normal boy. He is an excellent wearer but a poor performer. The other boy was fitted at three and one-half years of age and is now five and one-half years old. He occasionally takes naps wearing his prosthesis.

One girl (D.T.) was originally fitted with a split socket at 27 months, changed to a preflexed arm and then to a Hepp-Kuhn prosthesis at nine years of age. She wore this limb for three months, was unhappy with the decrease in elbow flexion and the "low takeoff." The anterior trim line was cut down, a triceps pad added, and the harness changed to a figure eight. Her next prosthesis was a standard preflexed limb but at 11 years of age, at her request, she was again fitted with a Hepp-Kuhn arm. She did not like the added suspension, triceps pad, and hinges of the standard fitting. She has now been wearing her Hepp-Kuhn prosthesis for 30 months and is an excellent wearer.

The reasons for acceptance most often given by this group are: "better appearance," and "less straps." Most mothers liked the cosmesis of the arm.

Our series shows an acceptance rate of 47.6 percent (10 of 21) and a rejection rate of 52.4 percent (11 of 21). A further breakdown reveals that the boys have a rejection rate of 81.8 percent (9 of 11), and an acceptance rate of 18.2 percent (2 of 11). Conversely, the girls had an acceptance rate of 80 percent (8 of 10) with only a 20 percent rejection rate (2 of 10).

These figures are at great variance with those reported by New York University not only in the overall acceptance rate, 84 to 47.6 percent, but in the marked discrepancy in the rate of acceptance by the girls in our series, and the high rejection rate by the boys. In the New York University report, there was little difference in acceptance and rejection by the two sexes.

Every child in our series had a normal range of stump motion (elbow flexion) of approximately 135 degrees-some even greater because of hyperextension. Yet we cannot equate, in this series, range of motion with the prosthesis and stump length, and we believe a constant direct ratio should exist between length of stump and range of motion, i.e., the longer the stump the greater the range of motion. This discrepancy in our series can be explained on the basis of prosthetic familiarity and competency in fabrication. Six different prosthetics facilities were involved in the fittings and none of our prosthetists had received instruction in the Hepp-Kuhn procedures. Hence, there was no uniformity of fabrication technique or skill.

Age at time of fitting seemed to have a great influence on whether the prosthesis was accepted or rejected. In this we concur with the results of the NYU survey. Those accepting the arm ranged in age from three to ten years at the time of fitting with the Hepp-Kuhn prosthesis, the average being 6.1 years. On the other hand, the age range of those rejecting the limb was from eight to 17 years, with the mean being 12.2 years. A negative correlation was also found between acceptance and the length of time a prosthesis of a different type was worn prior to fitting with a Muenster arm.

Socket comfort was an area in which wide disagreement was found among the amputees. Pressure areas from poor prosthetic fabrication was discounted in this evaluation. Some praised the feeling of the intimate fit, others did not like the "tight socket."

Level of performance provided the sharpest criterion for demarcation between acceptance or rejection. Whether boy or girl, those who were most active in sports, play activities, and strenuous hobbies tended to reject the prosthesis because of limited motion, socket discomfort, increased perspiration, and pressure on the olecranon. Conversely, those children who led a more sedentary existence accepted the limitations of the prosthesis for better cosmesis and a less cumbersome suspension.

Conclusions

  1. Girls tend to have a greater liking for the Hepp-Kuhn prosthesis and accept it more readily than do boys.

  2. Active boys and girls usually reject the German-type prosthesis.

  3. The longer a child has worn a standard-type fitting, the less the chances are for acceptance of a Hepp-Kuhn fitting.

  4. The younger a child is when he is fitted with a Hepp-Kuhn prosthesis, the more likely he is to accept it.

  5. Ability to use the prosthesis seemed to have no bearing on acceptance.

  6. Range of motion is dependent on length of stump and skill in fabrication.

  7. Reasons most often given for rejection of the Hepp-Kuhn prosthesis were tight fit and restriction of motion.

  8. Reasons most often given for acceptance were less straps and better appearance.

We believe the Muenster socket is an excellent fabrication technique for short below-elbow amputees, whether used with or without auxiliary suspension. In cases of extremely short stumps, one to one and one-half inches, it may be the only way a below-elbow fitting can be accomplished.

Addendum

We have found a unique situation in which a Muenster socket seemed to be the perfect answer to a child's needs. One of our children with a congenital deficiency (Fig. 1 ) desired to play a guitar. The prosthetist fitted her with a Hepp-Kuhn socket, a very short forearm shell and a small hook (Fig. 2 ). The pick is inserted and held in the hook. The child can then play the guitar without additional harnessing or suspension (Fig. 3 ). However, she uses this prosthesis only for playing the guitar and has no desire to wear it on a full-time basis. For regular use, she prefers her arm with a standard preflexed socket, triceps pad, and figure eight harness.

Raymond J. Pellicore, M.D., Sally Mier, O.T.R., Robert C. Hamilton, M.D., and Claude N. Lambert, M.D. are associated with the University of Illinois Amputee Clinic Chicago, Illinois

References:
1. Pellicore, R.L.: "Experiences With the Hepp-Kuhn Below-Elbow Prosthesis-A Preliminary Report," Inter-Clin. Information Bull., 3:1-7, Sept. 1964. 
2. Gorton, A.: "The Muenster-Type Below-Elbow Prosthesis for Children," Prosthetic and Orthotic Studies, New York University Post-Graduate Medical School, Mar. 1967. 
3. Epps, C.H., Jr., and Hile, J.H.: "Experience With the Muenster-Type Below-Elbow Prosthesis-A Preliminary Report," Inter-Clin.Information Bull., 7:1-6, July 1968. 
4. Gazeley, W.E., Ey, M.C., and Sampson, W.: "Follow-up Experiences With Muenster Prostheses," Inter-Clin. Information Bull., 7:7-11, July 1968.