A New Device for the Treatment of
Metarsus Adductus
Andrew Chong, M.S., F.M.C.S.(c), F.A.C.S.
Abstract
While the usual treatment of moderate to
severe metatarsus adductus has been serial
castings, a new device has been developed
which may be used as an alternative to castings. The ready-made polypropylene orthosis embodies the corrective features of a cast,
and its clinical efficacy was confirmed in a
prospective study of the children with moderate to severe deformities between the ages
of two and eight months. All 116 children
obtained complete correction after two to 12
weeks of orthotic wear. The advantages of
orthotic treatment over casting include safety, convenience and dramatic savings in cost
and time.
Introduction
Metatarsus adductus is a common foot deformity at birth, characterized by adduction
of the forefoot in relation to the hindfoot at
the tarso-metatarsal joints. There may be
some varus of the forefoot associated with
the adduction, but the hindfoot or the heel is
usually in the neutral position.1 In most infants, this deformity is mainly postural at
birth, and resolves spontaneously in the first
two months of life.
In some infants, however, the deformity
persists even after two months of age, and
becomes increasingly structural and fixed.
While some of these instances might still correct spontaneously in the first year of life,
treatment becomes increasingly difficult
with each passing month. Bleck has demonstrated that if the deformity is not treated
before the age of nine months, the chances
for complete correction are significantly lower.2 The consensus of opinion of orthopedic
surgeons at this time is to start active treatment at the age of two to three months.3-9
Bleck has classified metatarsus adductus
into three grades of severity depending on
where the heel bisector falls between the
toes:
Normal - heel bisector crosses between
second and third toes.
Mild - heel bisector passes through third
toe.
Moderate - heel bisector passes between
third and fourth toes.
Severe - heel bisector passes between
fourth and fifth toes.
He also further distinguished between
those that are fully flexible (if one can passively overcorrect the deformity), partially
flexible (if one can passively correct the foot
to the neutral position only), and rigid
(where no passive correction is obtainable).
In the less flexible forms, a skin crease is
often present.
It is generally thought that the mild and
fully flexible forms of metatarsus adductus
correct spontaneously with time, and no active treatment is required. The moderate
and severe forms, which are only partially
flexible, require active treatment, especially
if associated with a skin crease.
There is general agreement among orthopedic surgeons that in a child two months of
age or older, where the deformity is moderate or severe and partially flexible, casting is
indicated10-16 Casting is usually for a period
of six to 12 weeks, with weekly or bi-weekly
cast changes to accommodate foot growth.
Once complete correction has been obtained, the child is put in corrective outflare
shoes for two to three months to maintain
the correction and prevent recurrence.
Although the results of cast treatment are
good, there are distinct disadvantages:
- Repeated casting by an orthopedic surgeon trained in casting techniques is required; repeated visits for cast changes
incur considerable expenditure of time
to both physician and family.
- There are possible cast complications.
The casting technique is a very exacting
procedure. While the cast has to be corrective, any undue pressure can cause
skin breakdown. If the cast is too tight,
circulatory problems may arise with serious consequences.
- The child is too young to complain in
any way except cry if the cast is causing
any problems. Parents have no indication of trouble except the condition of
the toes, since the whole foot is covered
by the cast. As a result, skin problems
may not be noticed till the next cast
change.
- Emotional trauma to both infant and
family.
Alternatives to casting have been sought
over the years, and they basically fall into
two groups: shoes (or boots) and orthoses
(or splints). In spite of several introductions
over the years these alternatives have not
been utilized to any significant degree, and
casting remains today the treatment of
choice. The reason is that these alternatives
lack the features that are necessary to correct
the deformity.
Shoes and boots have been ineffective in
obtaining correction because the flexible
material of which they are made does not
hold the foot securely enough to effect correction. At the present time shoes are used
mainly as a holding device after correction
has been obtained with casts.17-19
Orthoses that have been introduced so far
do not hold the heel and the medial portion
of the foot securely enough to allow for successful correction of the deformity. They are
rarely used for the correction of metatarsus
adductus; and if used at all, they serve primarily to maintain the correction that had
been previously obtained with casting.20,21
The Orthosis
The new device (Figure 1
and Figure 2
) which the
author developed and tested in the last three
years is an orthosis made of thermo
plastic material (polypropylene). It is unique
in that it embodies the corrective features of
a cast without its disadvantages. It is molded
to conform generally to the inner border of
the foot in the over-corrected position (Figure 5)
and makes use of the following principle of three-point fixation to correct the deformity:
- First point of fixation - the heel or
hindfoot is securely held by the heel
portion of the orthosis to prevent the
hindfoot from going into valgus when
the corrective force is applied.
- Second point of fixation - the distal
part of the first metatarsal and great toe
are securely held by the foot portion of
the orthosis.
- Third point of fixation (between the 1st
and 2nd points) - provides the corrective force on the lateral border of the
foot against the convexity of the deformity by use of a Velcro? strap. The
amount of correction can be determined and graduated, if necessary, by
adjusting the tightness of the strap. In
this way, the patient is provided with a
relatively inexpensive ready-made device, but customized correction.
When first conceived, the orthosis was
made in several different sizes to accommodate size differences in the feet. Subsequent
experience indicated that within the age
range of the children studied, this was not
necessary. By trial and error, one particular
size was found that would accommodate
most feet between the ages of two to eight
months. In the younger infant, the fit may be
loose, but as long as the medial border of the
heel (first point of fixation) and the great toe
second point of fixation) were securely held
against the device, the foot strap could be
applied effectively against the apex of the
deformity. In the older infant, the orthosis
might be snug, but as long as the foot including the great toe was properly seated in the
brace, it would work. Occasionally, there
would be the "hard-to-fit" foot, and slight
adjustment to the device might be needed.
This could be done with a heat gun to open
up the orthosis (Figure 3)
or a hand trimmer
to remove the edge of the orthosis in the
appropriate areas (Figure 4)
to allow for
more proper fit and effective correction.
Needless to say, even within the age range
under discussion, there will be occasion
when a different size device would be required.
It would appear that if such an orthosis
works as well as casting, it would be preferable to castings. The advantages are obvious:
- Ease of application and high acceptability. Any interested physician could learn
the technique in a matter of minutes,
and in turn may teach and supervise the
parent in the use of the device.
- Avoidance of cast complications, since
the orthosis is removed twice a day for
cleaning. Any serious skin breakdown
and circulatory problems are thus avoided.
- Cost effectiveness. The same orthosis is
used for the whole duration of treatment, usually about three months.
The Study
A prospective study was therefore undertaken by the author to test the clinical efficacy of this device. All cases were referred to
me by primary-care physicians (pediatrician
or family practitioner). All children who fitted the following criteria were included in
the study:
- They were between the ages of two and
eight months.
- The deformities were moderate or severe, and partially flexible or worse by
Bleck's criteria. These were cases that
would have needed serial castings. Mild
deformities or completely flexible feet
(regardless of severity) by Bleck's criteria were excluded from the study.
- They returned for regular follow-up for
a period of at least six months.
There were 116 children (200 feet) (Table 1)
who
were studied, 59 of whom were males and 57
females (Table 2)
. One-hundred-thirteen
feet were classified as moderate, and 87 feet
classified as severe by Bleck's criteria (Table
3)
. All the feet were partially flexible in differing degrees. No rigid (totally inflexible)
feet were encountered in the series. Eighty-four children had bilateral involvement and
32 children were unilateral. This indicated a
72% incidence of bilaterality, compared to
65.6% reported by Bleck.1 Of the 32 unilateral cases, 23 were left feet and nine were
right feet, indicating a preponderance of left
feet involvement.
At the initial office visit, the parent was
taught to apply the orthosis correctly, to the
satisfaction of the physician. Wear was for 24
hours a day, except for half-hour twice a day
cleaning, for a period of eight weeks or until
complete correction was obtained, whichever was the greater. Then the device was used
at night to maintain the correction for four
more weeks to prevent recurrence.
The child was seen at two weeks, four
weeks, eight weeks, twelve weeks, six
months and one year and beyond from the
time of initial fitting. At each visit, clinical
examination, clinical photographs and foot
imprints were taken for objective evaluation
of the feet. Clinical photographs, while useful for illustrative purposes, were not as objective as foot imprints for evaluation purposes, and were not routinely used later in
the study.
Of the 116 children studied, 38 children
had a six month follow-up, 28 children had a
one year follow-up, 21 had a 18 months follow-up, 26 had a two year follow-up, and
three had a three year follow-up. Average
duration of follow-up was 14 and a half
months from the time of treatment (Table 4)
.
Results
The results of the study have been most
encouraging.
(Figure 6
, Figure 7
, Figure 8
, Figure 9
, and Figure 10
).
All 116 children obtained complete correction with
bracing (by Bleck's criteria for correction
and flexibility). Of the 200 feet studied, 15
feet (or 7.5°c) obtained complete correction
after two weeks of bracing; 59 feet (or
29.5%) obtained complete correction after
four weeks of bracing; 111 feet (or 55.5%)
obtained complete correction after eight
weeks of bracing; and 15 feet (or 7.5%) obtained complete correction after twelve
weeks of bracing (Table 5)
.
It was interesting to note that while there
was no direct correlation between the age of
the patient and the duration of bracing required for complete correction, only children four months or younger could obtain
complete correction in as little as two weeks
(Table 6)
. Again, no direct correlation was
found between the severity of the deformity
and the duration of the bracing required to
obtain complete correction, but the less severe deformities responded more readily to
bracing. Fourteen of the moderate deformities obtained complete correction after only
two weeks of bracing, while only one of the
severe deformities responded in two weeks
(Table 7)
.
The sex of the child did not play a part in
determining the severity of the deformity,
nor the duration of bracing required to obtain correction (Table 3
and Table 8
).
The feet remained completely corrected at
subsequent follow-ups of up to three years
Table 3
, indicating no recurrence.
Complications
Complications and difficulties were encountered, but were not serious in nature:
- Skin redness was common over the
pressure points at the distal part of the
first metatarsal, the heel, and the dorsum of the foot under the foot strap, but
were of no consequence. The redness
disappeared once full-time orthotic
wear was discontinued. There were,
however, two cases of skin blistering on
the dorsum of the foot due to pressure
against the edge of the brace. This was
obviated by use of a heat-gun to relieve
the edge of the orthosis. Incorporation
of a polyethylene foam lining in the device and use of thin cotton or acrylic
socks under the orthosis also helped.
- Dynamic hallux varus occurred in five
cases. In this condition, the foot remained straight, but the great toe tended to turn in when the child stood or
walked. When seated or lying down,
the great toe returned to its normal direction. This is an often encountered
condition even with castings. There is
no structural problem involved, and
usually the condition clears up spontaneously after a few months. In the series, all five cases resolved on follow-up.
- No response to treatment, though not
encountered in this present study of 116
children, could be expected if bracing
was used in the rarer, totally inflexible
or rigid deformities. An attempt at
studying the efficacy of the orthosis on
this class of deformities is needed. In
the meantime, the author's approach is
to start bracing as early as possible, and
if no improvement is evident after four
to six weeks, casting should be used.
- Recurrence after correction was not encountered in this present study. The author felt that the best way to prevent
recurrence was to continue full-time
bracing for eight weeks or till complete
correction was obtained, whichever was
the greater, and then to maintain the
correction using the orthosis at night for
four weeks afterwards. Corrective
shoes were not found to be necessary.
- Circulation problems were not encountered since the whole foot was exposed
to view, and the Velcro? straps could
be easily detached in case of doubt. The
infant's parents were always told to call
immediately if there was any concern.
Conclusion
In conclusion, a new device has been developed and tested for the treatment of
metatarsus adductus in infancy, and has
been found to be a very effective alternative
to serial castings. Distinct advantages of this
corrective brace over castings include safety
convenience and dramatic savings in cost
and time.
Note: The Wheaton Brace is available
through the Wheaton Brace Co., 380 5.
Schmare Road, Suite #201, Carol Street,
Illinois 60188; tel. 1-800-227-6769.
Andrew Chong. M.D., F.M.C.S.(C), F.A.C.S., presented this paper as a scientific exhibit at the American Academy of Orthopaedic Surgeons Annual Meeting in San Francisco, California, in
February 1987. Send correspondence to Andrew Chong, M.D., at 1800 N. Main Street, Wheaton, Illinois 60187. Tel. (312) 665-6200.
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