Establishing Parameters Affecting the
Use of Myoelectric Prostheses in
Children: A Preliminary Investigation
Gary M. Berke, M.S., C.P.
Caroline C. Nielsen, Ph.D.
Abstract
Little research currently exists describing
the factors that influence the use of myoelectric prostheses in children. A questionnaire
was designed to evaluate the relationship between the patterns of use and function of the
prosthesis and 1) length of residual limb, 2)
age the child was first fit with a passive prosthesis, and 3) the age the myoelectric prosthesis was first fit. Personal interviews were
conducted with the parents of 25 children
between the ages of 11 months and 18 years
who had been fit with a myoelectric prosthesis at a pediatric rehabilitation hospital. Results indicated that the length of the residual
limb was a critical factor in continued use of
the prosthesis. Results also showed that 22
percent of the below elbow amputees rejected their prosthesis completely. Suggestions
for further study in related areas are discussed.
Introduction
The purpose of this study was to investigate parameters that affect the use of myoelectric upper extremity prostheses in children. In the mid-1960s myoelectric prostheses were introduced as an alternative to conventional body-powered prostheses. The
conventional prosthesis is lacking in cosmetic qualities and requires extensive harnessing
for function and suspension (1). Reported
advantages of externally powered (myoelectric) prostheses are 1) superior pinch force of
between 15 and 25 lbs. compared to 7 to 8
lbs. with a cable-operated hook, 2) improved
cosmetic and social acceptance, 3) freedom
from a harness and 4) improved function for
high-level amputees (2).
However, little research exists describing
the actual use and function of myoelectric
prostheses with children. The fitting of
myoelectric prostheses is currently justified
on manufacturers' claims and clinical experimentation. The optimal age for fitting a child
with a prosthesis has been controversial for
many years. Previously, the accepted age of
first fit of a myoelectric upper limb prosthesis on a child was between the ages of two-and-a-half and four years (1). Currently, between 80 and 100 myoelectric terminal devices for children under the age of three are
sold in the country each year (3). Lack of
documentation in the area of myoelectric fitting in children provides little guidance in
determining successful candidates for myoelectric components.
In previous studies, some factors affecting
the use of upper extremity prostheses have
been identified, including level of amputation, age at first fitting of a passive prosthesis, and age at first fitting of a myoelectric
prosthesis (4,5). The level of amputation has
been considered a critical issue in the prediction of future myoelectric use (6). Unfortunately, the optimum level of amputation in
elective situations, for the most effective use
of a myoelectric prosthesis, has not been researched in children. Without this kind of
data, the prosthetist is forced to rely on clinical experience and personal opinion.
Several studies have looked at children
and the relationship between age and prosthetic acceptance. In 1983, Scotland and
Galway investigated the use of conventional
upper extremity prostheses in children (6).
Their results showed that 50 percent of children over the age of two rejected their prosthesis, compared with only 22 percent of the
patients who had been fit before the age of
two. Sorbye showed that only one in 40 children over the age of 18 months rejected his
prosthesis (1). Researched acceptance rates
of upper extremity prostheses have varied
considerably among authors and between
myoelectric and conventional prostheses
(2,7,8).
For this study, a chart review of the patients at a pediatric rehabilitation hospital
revealed that only half of the children previously fit with a myoelectric prosthesis continue to make regular appointments for the required routine maintenance or repairs on the
myoelectric prosthesis. This 50-percent return rate raised concerns because growing
children require frequent socket changes, as
well as occasional repairs due to prosthetic
malfunction. A 50-percent return rate may
indicate that only half of the children fit with
myoelectric prostheses are continuing to use
them. The effects of three factors were investigated: 1) level of amputation, 2) age at
which a prosthesis was first fit and 3) age at
which the first myoelectric prosthesis was fit.
MethodsSample
Since congenital amputees account for
only three percent of the population and upper extremity amputees make up less than 10
percent of the population, finding a significant sample size of young amputees for research purposes is difficult (9). The initial
sample for this study consisted of the entire
population of children at a pediatric rehabilitation hospital, under the age of 18, who had
been previously fit with myoelectric prostheses (N 30). Of the 25 families contacted, 52
percent of the children were below the age of
five and 56 percent of the children were
male. Ninety-six percent of the children
studied were amputees due to congenital
malformation of one or more of their limbs
(Table 1)
.
Fifty-six percent of the children were below-elbow (BE) amputees, 24 percent above
elbow (AE) and 20 percent were through-joint amputees. The latter group consisted of
elbow disarticulation, wrist disarticulation
and partial hand amputees.
Children in this facility are routinely fit at
a young age with a passive prosthesis in an
attempt to increase compliance by allowing
the child to "get used to wearing a prosthesis." Ninety-six percent of the children investigated in this study were initially fit with the
first myoelectric prosthesis under the age of
two years, and 12 percent under the age of
one.
An interview was carried out by telephone
or in person with the parents of these 30
children. Four of the families were unavailable or refused to be interviewed. One
young amputee was still wearing a temporary prosthesis and was excluded from the
study because her current wear patterns
would not reflect the actual use and wear.
The final sample included 25 children.
Data Collection
To address the concern of prosthetic acceptance in child amputees, a questionnaire
was designed to gather data on the child's
prosthetic and medical history, patterns of
use with the myoelectric prosthesis and pertinent parental information. The questionnaire consisted of open-ended questions, allowing parents to raise issues of concern for
them, as well as questions soliciting more
guided responses to provide data for comparison.
Results
As in previous studies, where patients
used conventional or myoelectric prostheses, the number of hours that the prosthesis
was worn was determined to be the primary
indicator for prosthetic acceptance (10). The
total number of hours that the prosthesis was
worn at home and at school was categorized
into full time, part time and none. Part-time
use was defined as less than 10 percent daily
wear time and use for special purposes and
therapy only. A significant relationship
(p<.01) was found between hours worn at
school and hours worn at home, suggesting
that the patients who wear their prosthesis
full time at home will usually wear their prosthesis full time at school.
A chi-square analysis was performed between "use" and 1) level of amputation, 2)
age first fit with a passive prosthesis and 3)
age when fit with a myoelectric prosthesis.
Results showed a significant correlation
(p<.05) between the level of amputation
and use of a myoelectric prosthesis (Table 2)
.
In this study, 100 percent of all through-joint
amputees (including partial hand, wrist disarticulation and elbow disarticulation amputees) no longer use their prosthesis. Twenty-two percent (N =4) of the BE amputees contacted rejected their prosthesis completely.
The BE prosthetic acceptance rate, in this
study, coincides directly with Millstein's
1982 study on adults with myoelectric prostheses (11).
Although the relationship between age at
first fitting of a passive or myoelectric prosthesis and myoelectric prosthesis use was not
statistically significant, the data suggest
trends that should be researched further with
a larger population. Over 50 percent of those
fit with a passive prosthesis at less than one
year of age still wear their myoelectric prosthesis full time. In comparison, less than 17
percent of those who were fit with a passive
prosthesis after the age of one continue to
wear their myoelectric prosthesis full time.
The age at which the myoelectric prosthesis was fit may also be associated with acceptance of the prosthesis. In this sample there
are only eight children over the age of seven.
However, 75 percent of those over seven
years old rejected the myoelectric prosthesis. The age factor appears to be an important variable in prosthetic acceptance, but
requires further study with a larger sample.
Discussion
Responses to open-ended questions provided descriptive information of value to the
prosthetist. When parents were asked if
there was any particular activity for which
the myoelectric prosthesis MUST be worn,
their responses varied considerably (Table
3)
. Bicycle riding was the most frequent response, followed closely by cutting paper.
While these are not usually thought of as
bimanual activities, they were activities for
which the children felt they needed to use
their prosthesis. Stringing beads was the
most popular activity used in therapy to enhance control and function of the myoelectric prosthesis. Many parents responded that
there was no activity for which their child
MUST wear his or her prosthesis. This report was particularly interesting, since one of
the respondents was the parent of a shoulder
disarticulation/short AE quadrimembral
amputee, and one was the parent of a bilateral BE amputee. This suggests that upper
extremity amputees, of any level, have the
ability to adapt and function in the activities
of daily living without the assistance of a
prosthesis, either through the use of adaptive equipment or by independent adaptation. Further study should be pursued, investigating specific activities for which a myoelectric prosthesis is used.
When the parents were asked "for what
reasons use of the myoelectric prosthesis
might be suspended for a period of time,"
several responses were noteworthy. Fear of
damage, while being the most common response, was the only response where the parents dictated when the prosthesis was not to
be worn. Comments such as "She complained of it being very hot inside and her
arm was very sweaty," or "He felt it was very
heavy" were cited as reasons that children
did not want to continue to wear their prosthesis. "Mood" was the most popular response among the parents of two-year-old
patients (Table 4)
.
There are several items that came up in
the interview process and that may be important for prosthetists and require further
study. Every patient who had previously
worn a conventional prosthesis, but had had
a time gap before the fitting of the myoelectric prosthesis, rejected both prostheses,
even if the patient had been a consistent conventional wearer in the past. Although rejection may be a function of patient motivation,
this finding suggests that it may be important
for the prosthetist to anticipate the need for
a new prosthesis and decrease the time lapse
between proper-fitting prostheses.
Secondly, 88 percent of the people interviewed were the mothers of the children.
Unfortunately, the mother was not always
the one to answer the telephone. Fathers
who were initially contacted deferred to
their wives, saying "She knows more than I
do about this," or "I better let you talk to my
wife." One father attempted to complete the
first half of the interview process prior to
turning to his wife for "more accurate answers." For the healthcare professional, this
information raises questions as to whether
greater emphasis should be placed on incorporating both parents in the rehabilitation
process. Future research may look at the role
of the family in maintaining use and function
of the prosthesis.
Conclusion
Several interesting trends were noted in
this investigation. The length of the residual
limb plays a significant role in the future
acceptance of a myoelectric prosthesis. This
information is essential for surgeons as well
as prosthetists and appears to be an important factor affecting the acceptance and continued use of the myoelectric prosthesis. Future research with other samples of children
would further substantiate this finding. In
addition, continued investigation of the role
of age at the final fitting and the timing of the
fitting of the myoelectric prosthesis will provide further information on optimal conditions for prosthetic acceptance. With future
research, it may be possible to specify parameters that predict successful use of a
myoelectric prosthesis in children.
Acknowledgements
This study was completed with the generous
assistance of Newington Children's Hospital,
Dept. of Orthotics and Prosthetics, Newington,
Conn.
Gary M. Berke, M.S., C.P., is director of prosthetics, California State University, Dominguez
Hills, Calif.
Caroline C. Nielsen, Ph.D., is associate professor and director, Research and Graduate Studies,
School of Allied Health Professions, 358 Mansfield Road, University of Connecticut, Storrs,
Conn. 06269-2101, (203) 486-0018.
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