Age-Appropriateness of Myoelectric Prosthetic Fitting

SHARON R. MENKVELD, MD.*MARY POINT NOVOTNY, RN, MS,AND MARCIA SCHWARTZ, OTR/L**


Myoelectric upper-limb prostheses have been available for adults for twenty years. The first reported fitting of a young child was in 1971 at the Orebro Rehabilitation Center and used adult components. This led to the development of an electrically powered hand in sizes appropriate for preschoolers by 1976. Currently, three child-size electric hands are commercially available. The last ACPOC survey showed 25 of 40 member clinics offer myoelectric fittings for upper traumatic and congenital deficiencies. The experience of many clinics 2,5,6,7,8,9,10,12,13,16 is contradictory or inconclusive about the best time to fit this prosthesis for a child. Therefore, we reviewed amputees fitted with myoelectric prostheses (MEP) in our clinic, and compared them with other reported series to establish guidelines for the appropriate age for myoelectric prosthetic prescription.

Method

This study looks at children who are past their initial training and evaluation period and have resumed their usual life style and activities. The first year is a time of excitement and experimentation with a new device and is not typical of established prosthetic wearing patterns. The study group was restricted to unilateral below-elbow amputees who had received professional prosthetic management throughout childhood. Twenty such patients were identified from our clinic population. No congenital amputee who had an MEP for more than one year was excluded. Twenty children, 17 girls and 3 boys, had myoelectric prostheses, most provided with support of the Variety Club, Chicago chapter. Nineteen had congenital transverse deficiencies and one had traumatic amputation at the age of 2 weeks, performed secondary to vascular complications of an intravenous catheter. Three right and 17 left limbs were involved.

X-rays were available on 13 patients. All children whose length of amputation was at least 50 percent that of the contralateral forearm had located radial heads. Of those with a shorter amputation limb, all but two radial heads were dislocated; one demonstrated distal tip synostosis between the radius and ulna.

Fitting the myoelectric prosthesis was done at an average age of 8.5 years. All children with below-elbow amputations had a modified Munster socket and the Otto Bock 2-state proportional control motor with a 6 volt battery. Cosmetic gloves were ordered as needed. At the time of this study, the age range was 5 to 21 years, with a mean of 13.5 years (Fig. 1 ). In addition to clinical examination, all patients completed a questionnaire constructed with open ended questions to elicit idiosyncratic responses and internal checks for consistency.

Results and Discussion

We tried to distinguish groups of non-wearers, cosmetic wearers, and functional wearers of myoelectric prostheses. Comparison of adult myoelectric and conventional hook wearers showed that the wearing time for each group was significantly different.14 The conventional prosthesis was worn an average of 14 hours per day and the myoelectric, 9.6 hours per day. Therefore, full-time MEP wear was defined as longer than 9 hours per day. We patterned our prosthetic functional usage questions after the study done in Toronto to obtain patterns of wear.11 Within each functional group we compared length of amputation limb, non-MEP prosthetic experience, training, technical skill with each prosthesis, number and type of complaints about each prosthesis, age at MEP prescription, years of MEP wearing, and age at the time of our study. Four patterns of MEP wear and usage described our population: full-time functional usage, full-time cosmetic wear, interchangeable prosthetic choice, and rejection of the MEP Table 1 shows the distribution of patients within the groups.

Length of the amputation limb is optimal when it is within the middle third of the contralateral forearm length, but almost any length can be accommodated by a myoelectric prosthesis. Our series consisted of comparative lengths equal to the proximal third in seven children, equal to the middle third length in nine, and distal third in two patients. Two others had length equal to the contralateral side; all lengths were represented in each group of MEP wearing patterns.

Previous prosthetic experience revealed that the average age at first fitting was 9 months. In our series, 18 children were originally fitted before the age of one year; half having a prosthesis before the age of 6 months. The CAPP terminal device was prescribed for five patients at an average age of 18 months, and there were 18 previous hook users whose average age at fitting was 22 months. No significant differences of pre-MEP prosthetic wear or prescription were evident among the four wearing pattern groups.

Formal training time varied from no additional training with the MEP to three times a week for one year. The mean and range of training time of each group of wearing pattern subjects showed no difference among the groups. Only two requested and required more intensive therapy to increase skill and comfort in the prostheses. Of course, our patients were experienced conventional prosthetic wearers.

Herberts4 reported in adult amputees that technical skill was not related to acceptance of prosthetic devices. The electric hand is slower than a conventional hook with an average time to full myoelectric finger opening of I second. All our patients could complete age-appropriate tasks with their preferred fitting (including no prosthesis). Most agreed verbally and demonstrated increased skill with a conventional terminal device but this was not distinctive among groups. All liked the appearance of the MEP, the absence of harnessing, and its enhancement of social situations. Appearance was important to both parents and patients. Fewer subjects commented on the increased grip strength or independence of arm position in terminal device operation. Perceived disadvantages of the MEP were increased weight, glove fragility, increased temperature in the socket, and increased time for socket fittings and refittings. The tighter than usual fit led to the complaint of pain after wearing the prosthesis for a long time. Three subjects experienced swelling after heavy use which required packing the amputation limb in ice. Battery failure and slowness of closing were also mentioned sporadically. No difference existed in the distribution or the severity of complaints among the groups of prosthetic wear patterns.

Functional MEP wearers showed full-time wear with no other prosthesis being used. All wore their prosthesis at least 9 hours per day. Their age at fitting varied from 3.5 to 16 years and, at time of evaluation, from 5 to 20 years (Table 2 ). Confirming the literature,9 the optimal prosthetic users were adolescent girls. In our series, the young women wore their MEP the greatest number of hours per day and had the fewest number of activities routinely performed without the prosthesis. Cosmetic wearers (Table 3 ) were older as a group and were successful MEP wearers but were less interested in function; they were happy to discard the motor and battery to decrease weight of their prostheses. This group actually had the longest average accumulated MEP wearing time prior to changing to cosmetic prostheses.

Part-time wearers (Table 4 ) usually switched freely between their MEP and no prostheses, although one subject used a body-powered hook and the MEP. This group was the most homogeneous regarding the age of the myoelectric fitting; all were in the middle childhood years at the time of our survey. All identified themselves as part-time MEP wearers. As compared to the age-matched group of full-time prosthetic wearers, the wearing time differed by less than 2 hours per day.

The group that rejected the MEP (Table 5 ) was heterogeneous and the largest of our series. Four discontinued MEP wear between ages 8 and 9. Most actually liked the MEP while they used it but discarded it for a variety of reasons. Trouble obtaining repairs, child care and an industrial job, switching to a CAPP terminal device after five years of fulltime MEP wear that became "too heavy", and fragility of the glove with inadequate strength were some explanations. Only one subject, fitted at the age of 10, after two years of no prosthetic wear, never became comfortable with her MEP; she discontinued it after a year. Currently, two patients in this group wear no prosthesis, one wears a CAPP device, two use a hook and two use a body-powered hand (Table 6). Sorbye13 studied 40 children, all unilateral below-elbow amputees. Fifteen had no previous prosthetic fitting, 15 had had a cosmetic limb, and 10 had used a body-powered hook. Sorbye's age distribution at the time of intial myoelectric fitting was younger than ours; all were fitted in the preschool years. Of the 35 subjects in his study who had had an MEP longer than 6 months, 11 wore it for less than 5 hours per day (31%). He also found free interchange between two alternative prostheses in the ten previous conventional prosthetic wearers. Their age at evaluation was not given. Mendez10 reported the experience of 87 children with unilateral below-elbow amputations, all of whom had been previous conventional prosthetic wearers. They were fitted between the ages of 3'/2 and 4 years. She reported 20 percent used the electric hand intermittently or for cosmetic or minimal function only. Another quarter continued to interchange both prostheses freely.

Trost16 studied 45 children, all of whom had conventional prostheses; 34 previously wore conventional prostheses at the time of myoelectric fitting (average age 12.5 years). He reported seven of the 34 children wore myoelectric and conventional prostheses interchangeably; among myoelectric wearers, equal numbers wore the prosthesis for occasional cosmetic reasons as those who wore it full time for functional use.

Excellent MEP acceptance was reported by Kritter7 in a series of children fitted from the ages of 5 to 17 years with an average of 10.9 years, as well as by the UCLA series' which had an age range at myoelectric fitting of 26 months to 12'/2 years, and by a group of 17 preschoolers in Toronto.6 Smaller series of patients' and teenagers using adult components3,9 also experienced MEP success.

Rejection rates of MEP for juvenile amputees are less than 10 percent, 1.2.7.13 20 percent,10 and 30 percent.16 Part-time interchangeable or cosmetic MEP usage can be dissected from these reports. In spite of the variability of wearing patterns and outright rejection by long-time prosthetic wearers, many clinicians remain proponents of early MEP fittings. For example, Sorbye13 recommended fitting the MEP between the ages of 2 1/2 and 4 years, and advocated conventional cosmetic fitting earlier. He noted that between the ages of 5 and 6 years, a body-powered hook wearer lacks motivation to change to the myoelectric system; the motivational factor does not increase until the age of 12 to 14 years. Based on his experience, however, Trost16 now prescribes a MEP for patients between the ages of 9 and 11 and uses conventional prosthetic prescriptions before that time.

Our evaluation of wearing patterns in children after they have completed the first year when the prosthesis is an active issue in their life supports this more conservative MEP prescriptive practice. The conclusions based on our data included that early fitting correlates with continued prosthetic use throughout childhood. This is a cornerstone of pediatric amputee practice." The middle childhood years are the most variable in prosthetic wearing habits. Myoelectric prosthetic usage depends primarily on the current age of the child. The older child does demand a cosmetic terminal device but prescriptions which include a cosmetic or body-powered hand may be alternatives to a myoelectric powered system. We found no evidence that MEP prescription at a young age significantly changed wearing patterns throughout childhood. For patients under the age of nine, we now routinely prescribe body-powered hooks and hands. When the child voices dissatisfaction with the harnessing or grip strength and requests a MEP, it can then be made available.

Conclusions

Prescription of myoelectric limbs in young, and even preschool, children is a current trend. Twenty children fitten with below-elbow MEP for at least one year were interviewed and tested. All were previous conventional prosthetic wearers, originally fitted before the age of 1 year. Four wearing patterns were identified which distinguished wear and usage of the MEP: 1) functional full-time wearers; 2) interchangeable, part-time wearers; 3)cosmetic wearers; and 4) rejection. The groups could not be distinguished by level of amputation, facility of prosthetic use, MEP training time, or age of MEP fitting. Thus, 1) early prosthetic fitting correlates with continues prosthetic usage. 2) Middle childhood years show the greatest variability in prosthetic choice and usage. 3) MEP usage is most dependent on the current age of the child and full-time functional usage is unusual before adolescence. This implies that older children demand good appearance primarily and that prostheses with a passive or body-powered hand may be alternatives to myoelectrically powered hands.

*Milwaukee Medical Clinic, SC, 3003 West Good Hope Road, Milwaukee, WI 53217

**LaRabida Children's Hospital and Research Center, East 65th at Lake Michigan Chicago, IL 60649

References:

  1. Baron E, Clarke SD, Solomon C: The Two Stage Myoelectric Hand for Children and Young Adults, Inter-Clinic Information Bulletin 19:1-12, 1984.
  2. Dick HM, Hutnick G, Akdeniz R: Myoelectric Management of the Pediatric Amputee. Inter-Clinic Information Bulletin 20:39, 1985
  3. Ey MC: Experiences with Myoeletric Prostheses: A Preliminary Report. Inter-Clinic Information Bulletin 17:15-17, May-June 1978.
  4. Herberts P, Korner L, Caine K, Wensby L: Rehabilitation of Unilateral Below-Elbow Amputees with Myoelectric Prostheses. Scandinavian Journal of Rehabilitation Medicine 12:123-128, 1980.
  5. Hubbard S, Koheil R, Heger H, Galway HR, Milner M: Development of Upper-Extremity Myoelectric Training Methods for Preschool Congenital Amputees. Inter-Clinic Information Bulletin 19:1, 1984.
  6. Hubbard S, Galway R, Urquhart K, Mifsud M: Preschool Myoelectric Program: A Three-Year Review. Inter-Clinic Information Bulletin 20:38, 1985.
  7. Kritter AE: The Milwaukee Experience with Myoelectric Prostheses. Inter-Clinic Information Bulletin 19:1, 1984.
  8. Kritter AE: Current Concepts Review: Myoelectric Prostheses. Journal of Bone and Joint Surgery 67-A:654-657, 1985.
  9. Lyttle D, Sweitzer R, Steinke T, Trefler E, Hobson D: Experiences with Myoelectric Below-Elbow Fittings in Teenagers. Inter-Clinic Information Bulletin 13:11-20, March 1974.
  10. Mendez MA: Evaluation of a Myoelectric Hand Prosthesis for Children with a Below-Elbow Absence. Prosthetics and Orthotics International 9:137-140, 1985.
  11. Northmore-Ball MD, Heger H, Hunter GA: The Below-Elbow Myo-Electric Prosthesis. Journal of Bone and Joint Surgery 62-B:363-367, 1980.
  12. Sauter WF: A Cost-Benefit Analysis of 160 Patients with Electrically Powered Limbs. Inter-Clinic Information Bulletin 19:2-4, 1984.
  13. Sorbye R: Myoelectric Prosthetic Fitting in Young Children. Clinical Orthopaedics and Related Research 148:34-40, 1980.
  14. Stein RB, Walley M: Functional Comparison of Upper Extremity Amputees Using Myoelectric and Conventional Prostheses. Archives of Physical Medicine and Rehabilitation 64:243-248, 1983.
  15. Tervo RC, Leszczynski J: Juvenile Upper Amputees: Early Prosthetic Fit and Functional Use. Inter-Clinic Information Bulletin 18:11-15, Winter 1983.
  16. Trost FJ: A Comparison of Conventional and Myoelectric Below-Elbow Prosthetic Use. Inter-Clinic Information Bulletin 18:9-16, Fall 1983.