Modification of the Hepp-Kuhn Arm

Earl E. Vanderwerker, Jr., M.D. Siegfried Paul, C.P.O.

In the late 1950s Drs. Oskar Hepp and G. G. Kuhn of Munster, Germany3, developed a fitting technique for the below-elbow amputee which provided for very close fitting of the stump and extension of the socket above the olecranon and humeral condyles. This fitting also eliminated the front support strap of the typical below-elbow figure-8 harness. The Hepp-Kuhn or Münstertype fitting, as it was variously called, was given emphasis in the United States by an evaluation study conducted at New York University2 and by an instructional manual developed in connection with this study4.

Published reports on experiences with the Hepp-Kuhn fitting in the United States indicate some variability in the degree of success achieved1,5. In general, however, it can be said that the Hepp-Kuhn arm has been universally accepted over the past five years because of its security, lightness, and simplified harness. Nevertheless, some of our patients have complained of (1) diminished elbow flexion as compared to that obtained with a split-socket prosthesis with step-up hinges, and (2) increased clothing wear and lack of cosmesis due to the take-off angle of the control cable and consequent deformation of blouses and sweaters. These complaints have been obviated by the two modifications described below.

The biceps tendon is ignored in forming the mold for the socket, in contrast to the original concept. The index and middle fingers are placed over the superior margins of the medial and lateral humeral condyles. The "V" formed by the fingers allows space for the biceps tendon. The trim line of the socket over the tendon can be made more distal and the medial and lateral walls of the socket are slightly higher. Thus a greater range of flexion of the elbow is permitted without affecting security (Fig. 1 -A).

The harness has been modified to a "butterfly" or figure-8 (Kuhn) to route the control cable more parallel to the humerus and to relieve interference with clothing and wear (Fig. 1 -B). Although this arrangement necessitates a greater amount of harnessing and a slight decrease in the speed of applying the prosthesis, these minor drawbacks are more than compensated for by greater patient acceptance. Neither of the modifications described has produced a noticeable decrease in the mechanical efficiency of the prosthesis.

Newington Children's Hospital, Newington, Connecticut

1. Epps, C. H., and J. H. Hile, Experience with the Muenster-type below-elbow prosthesis-A preliminary report. Inter-Clin. Information Bull., 7:10:1 -5, July 1968. 
2. Fishman, S., and H. W. Kay, The Münster-type below-elbow socket, an evaluation. Artif. Limbs, 8:2:4-14, Autumn 1964. 
3. Hepp, O., and G. G. Kuhn, Upper extremity prostheses, Proceedings of the Second International Prosthetics Course, Copenhagen, Denmark, July 30 to August 8, 1959. Committee on Prostheses, Braces and Technical Aids, International Society for the Welfare of Cripples, Copenhagen, Denmark, 1960, pp. 133-181. 
4. Kay, H. W., K. A. Cody, G. Hartmann, and D. E. Casella, The Munster-type below-elbow socket, a fabrication technique. Artif. Limbs, 9:2:4-25, Autumn 1965. 
5. Pellicore, R. J., S. Mier, R. C. Hamilton, and C. N. Lambert, Experiences with the Hepp-Kuhn below-elbow prosthesis, Inter-Clin. Information Bull., 8:6:9 14, Mar. 1969.