Experiences with Myoelectric Prostheses: A Preliminary Report

MILDRED C. EY, B.S., O.T.R., F.A.O.T.A.


Introduction

At this writing, six patients have been fitted with myoelectric prostheses at our Center, one more prosthesis is being fabricated, and others are pending. Prior to our first experience, a physician, two prosthetists, and an occupational therapist attended an Advanced Seminar on External Energy in Upper-Limb Prosthetics and Orthotics held in Syracuse, New York, in the spring of 1974. Subsequently, bilateral myoelectric prostheses were recommended for one of our patients. Once approval was obtained, the same group accompanied the patient to the Otto Bock facility in Minneapolis, Minnesota, where the patient was fitted and we had the opportunity to learn more about fitting and training. Our experiences since that time have been varied, and we have all learned valuable lessons.

Criteria for Selection

Although we have not established formal criteria for selection of candidates for myoelectric controls, there are many factors which we consider.

Primarily, the individual must have a desire for such a device, and it must be compatible with the type of work done. We do not feel that myoelectric prostheses are appropriate for those whose work frequently necessitates involvement with soil, heavy lifting, or sharp objects. They are excellent for any "clean" type of work and have also proved to be satisfactory for housework and for school.

Potential candidates are checked on the myotestcr for differentiation of signal. It is felt that if the patient can get even as little as 10 microvolts of signal, the electrical output can be developed to an adequate point.

We have fitted patients with congenital anomalies, and those with traumatic amputations. In the case of those with traumatic amputations, it is necessary that residual limbs be well healed, and that no further shrinkage is anticipated. This is necessary because of the importance of a very close fit.

At this time, we have fitted only those who have achieved full growth. If there were any financial resources, however, we would certainly consider younger candidates, providing they met the other criteria.

Case Report 1

S.C. was 40 years old when she had both hands amputated while operating a cutting machine in a leather mill in April 1974. She was initially fitted with conventional prostheses and was supplied with both hands and hooks. Once she received the hands, she stopped using the hooks for any activity and, in fact, has never even taken them home. It was about this time that several members of our clinic attended the Clinic Chiefs' Meeting in Montreal, and then the Syracuse Seminar. We returned full of enthusiasm and prescribed myoelectric prostheses for S.C. In February 1975 the trip to Otto Bock was undertaken. Prior to departure for Minneapolis, S.C. was placed on a program of preprosthetic training with a myotester. At the first fitting of her prostheses, she operated them well and in fact amazed the people at Otto Bock with her ability. Upon completion we returned to Schenectady, where she finished training on an outpatient basis.

Because her fitting is bilateral, the prostheses are given extremely hard and continuous use, and there have been many electrical and mechanical problems. For S.C., however, the myoelectric function is far superior to that of the conventional prostheses, and if one hand is not functioning properly, she will operate "one-handed" rather than revert to the conventional prostheses. She is a busy housewife with two grown daughters living at home.

We recommended a second pair of prostheses for S.C. and are awaiting approval. We feel that she should have a spare pair available. (There is no comparison in the effort required to operate conventional and myoelectric prostheses.) Also, the precision of myoelectric control is superior to conventional control.

For S.C., we feel that myoelectrie prostheses are the answer.

Case Report 2

Less than a year after S.C. had received her myoelectric prostheses, she telephoned one day to say that the 21-year-old daughter of her former supervisor had just had her right hand amputated in a similar accident on the same type of machine! When S.B. was referred to our clinic, she had only one thing in mind, a myoelectric prosthesis. SB. also had a program of preprosthetic training using the myotester. There was some delay in fitting because of size fluctuations in SB's residual limb. This problem persisted following receipt of the prosthesis, but the limb finally stabilized, and training was completed in November 1976. Although she had adapted to one-hand function, she found the prosthesis useful and wore it regularly until a dermatitis developed from the socket. Usually acrylic plastic is used for myoelectric sockets. After considerable testing, and cooperation with a dermatologist, a new socket was fabricated from polyester.

Although follow-up has been poor, S.B. has recently requested a new glove, so we know that she must be using the prosthesis.

Case Report 3

D.O. sustained a traumatic left below-elbow amputation in May 1968 at the age of 12. He was initially fitted with a conventional prosthesis and became a good user. Early in 1976 he became interested in having a myoelzctrie prosthesis and was seen in our clinic for evaluation. Preprosthetic training with a myotester was again used, and upon receiving the prosthesis in March 1976, D.0. had excellent control with no further training. He wore it for a few months and willingly came to our center to demonstrate it for others but ultimately found that he was doing primarily mechanical work and that it was not suitable for such work. He has returned to use of his conventional prosthesis. Perhaps, if he further pursues college and another career, he may someday return to use of his myoelectric prosthesis.

Case Report 4

S.P. sustained a left below-elbow amputation in an auto accident in May 1972 at the age of 20. At that time she was fitted with a conventional prosthesis with interchangeable functional hand and hook. She became an excellent user and consistent wearer. By 1977 she had decided that she wanted a myoelectric prosthesis. Preprosthetic training with the myotester was successfully used in combination with a home exercise program. Upon receipt of her prosthesis she immediately used it as though it had always been a part of her, and no further training was indicated. She has consistently worn it since that time, and very few repairs have been needed.

Case Report 5

L.L. was born December 22, 1963, with a left terminal transverse partial hemimelia and a malformed elbow with limited range of motion. She was initially fitted with a conventional prosthesis in June 1965 and has been continually followed in our clinic. In February 1976 she was supplied with a functional hand and received training with this device. She became interested in a myoelectric prosthesis, and in the summer of 1977 surgery was performed to increase her elbow range of motion. She received both a home exercise program and preprosthetic training with the myotester in January and February 1978, and received her myoelectric prosthesis in March. She had one session for checkout and training and demonstrated excellent use. An active teenager, she has already had two replacement gloves.

Case Report 6

S.C. was just 20 when her right hand was amputated by a meat grinder while she was working as a meat cutter in a supermarket. This accident occurred in February 1977. She received a conventional prosthesis and extensive training in its use. She found, however, that she could function well without it and used it only once a week when she went bowling. She was referred to our clinic in the spring of 1978 and was seen when her baby daughter was only 2 weeks old. Because of the travel distance involved, she was admitted for a few days of preprosthetic training with a myotester. She was discharged with a home exercise program and was readmitted when her prosthesis was completed. Within 48 hours she was using it as though she had been born with it, and was wearing it most waking hours. Her enthusiasm is such that she willingly returned to have TV tapes made for a news special about Sunnyview. She is wearing the prosthesis 8 to 10 hours daily. She is still somewhat reluctant to use it when caring for her baby.

Conclusion

In our limited experience we have fitted five females ranging in age from 14 to 41, and one male, age 20. The young man has been the only one who has reverted to a conventional prosthesis. The lady with bilateral fitting has probably had more problems with her prostheses than the others combined, but of course, she gives them much harder use. Also, in the newer prostheses the electronics have been improved. Generally, we have been very satisfied with our results and will continue to recommend myoelectric prostheses when we feel they are indicated. We currently have one man and one more woman awaiting financial approval and fabrication. We have had excellent results with preprosthetic training using a myotester, and prosthetic-use training has been minimal. The patients receive their prostheses and immediately start using them in a very natural manner. Those who have worn conventional prostheses really appreciate the absence of a harness!

Certainly, there is still much room for improvement. Myoelectric prostheses are, however, a "giant step"-or a "giant grasp," if you will-beyond what we have had!