A Wrist-Driven Hand Prosthesis
GUSTAV RUBIN, M.D. MICHAEL DANISI, CO. EUGENIO LAMBERTY
The type of amputation resulting in the loss of all digits including the thumb as a result of trauma is unusual but is somewhat more frequently encountered as a birth defect. The functional prosthesis described in this report will therefore have a wider application for patients with congenital deficits2,3 than for those with traumatic amputations. By the very nature of the Veterans Administration Prosthetics Center (VAPC), congenital amputees are not seen. Hence the prosthesis reported here was fabricated for a patient with posttraumatic amputation.
The prosthesis is based on a simple concept and involves the use of the Engen "reciprocal wrist-extension finger-flexion orthosis"1 to open and close prosthetic fingers by the action of the wrist stump. Since the Engen splint was originally developed to manipulate inactive flaccid fingers through the agency of an actively functioning wrist, it was a logical extension of this design to substitute prosthetic fingers in the case of a patient with total digital amputation, and to fit such fingers to the splint.
F. M., a 27-year-old stockbroker, sustained shell-fragment wounds on June 4, 1968. One feature of his multiple injuries was total amputation of all digits and metacarpals on the left hand, except for the proximal half of the thumb metacarpal ( Fig. 1 and Fig. 2 ). He was examined by the VAPC Clinic Team on Dec. 23, 1971, because he was dissatisfied with a Robin-Aids hand with which he had been provided and which functioned by means of a harness and transmission system. He found that this unit was extremely heavy and awkward and cosmetically unsatisfactory Jentschura et al., recommended that children with this lesion be fitted at years of age with an open-end plastic forearm with a hook attached over the extensor surface of the stump and activated by harness control3
At the VAPC Clinic Team meeting, two prosthetic approaches to the problem were outlined:
1. An attempt would be made to extend the thumb stump with a prosthesis to provide active opposition against a post. Since there was a distinct possibility that this might not succeed, a second course of action was outlined at the same time.
2. The Engen reciprocal wrist-extension finger-flexion orthosis would be used in conjunction with prosthetic fingers.
The first approach ended in failure. The second method was then employed and the patient was fitted on Aug. 21, 1972. He was given a short period of training here and returned home to practice. Since the patient came to VAPC from West Virginia, his visits were somewhat more widely spread than would be the case if he were locally situated. He performed well with this device and considered it cosmetically acceptable ( Fig. 3 , Fig. 4 . and Fig. 5 ). The patient communicated with this office by telephone on Aug. 24, 1972, and reported that, using the prosthetic hand, he could pick up grapes and put them in his mouth, and that he could also separate and pull off stamps. He said that he was rapidly becoming proficient in the use of his new prosthesis.
On Sept. 19, 1972, the patient returned for follow-up. He had been using the prosthesis constantly, and he demonstrated his ability to function with the device, eating grapes as he had reported, holding large objects such as soda cans, and holding a pencil or a sheet of paper. Measured pinch force was 3 pounds. [A new design under development will enable the patient to accomplish pinch with wrist flexion rather than with extension. This modification will make use of the more powerful wrist flexors (as compared to the extensors) and will increase pinch force significantly above the 3 pounds provided by the present prosthesis.]
The two components of this device are:
- A prosthetic hand.
- The Engen splint.
The prosthetic hand can be prefabricated in various sizes. In the reported case the hand was individually prepared in a stone mold employing Parcloid 23-126 white foam.* This could be made in a flesh color. If used in the density in which it reaches the laboratory, Parcloid will have the consistency of heavy rubber. If it is foamed its consistency remains satisfactory and its weight will be reduced by about one-third. The hand we used was foamed and weighed 4 ounces. Armatures were employed to reinforce the fingers and the Parcloid foam was poured into a stone mold** and cured at 135 deg. C. for three hours. It was allowed to cool overnight in the oven before removal. A thumb was prepared in the same manner.
The Engen reciprocal wrist-extension finger-flexion orthosis was modified in three ways:
- The metal band and Velcro strap controlling the middle finger were removed from the basic orthosis. Since the entire prosthetic hand is a unit, the Engen splint attachment to the index finger is sufficient to control movement of the total hand ( Fig. 4 and Fig. 5 ).
- The previously prepared prosthetic thumb was laminated to the splint ( Fig. 4 and Fig. 5 ).
- A 34-in. stainless-steel band was fitted to the proximal volar area of the prosthetic hand ( Fig. 4 and Fig. 5 ) to serve as a point of attachment for the ulnar joint. The band was brazed to the Engen splint on the radial side.
Action of the Prosthesis
The prosthesis functions in a manner similar to the well-known mode of action of the Engen splint1, i.e., dorsiflexion of the wrist closes the index finger against the thumb, and volar flexion opens the fingers.
A functional wrist-driven splint has been presented. It has proved to be a useful device for the total-hand amputee with an active wrist stump.
The authors wish to extend their appreciation to Mr. Harvey Young and Mr. Joseph Coppolino for their cooperation in preparing the Parcloid hand.
* Parcloid Chemical Co., 140 Greenwood Ave , Midland Park, N J 07432
** To prepare a mold of this type, a cosmetic glove of proper size is filled with wax and a two-piece mold of dental stone is fabricated over the wax.
1. Engen, Thorkild J., Development of upper extremity orthotics. Orth. and Pros., 24:2:1-31, June 1970.
2. Gingras, G., M. Mongeau, P. Moreault, M. Dupuis, B Hebert, and C. Corriveau, Congenital anomalies of the limbs-Parts I & II. Canad. Med J., 91:67-73, July II, 1964;91:115-119, July 18, 1964.
3. Jentschura, G., E Marquardt, and E. M Rudel, Malformation and Amputation of ¦ the Upper Extremity. Grune and Stratton, New York and London, 1967.