Plaster-Cast Application
The same initial approach has been used for all of our patients who have
had treatment of congenital vertical talus in the last five years, regardless
of age at the time of presentation or comorbid medical diagnoses
(Figs. 1-A and 1-B). Treatment
is started as soon as possible after referral, preferably shortly after birth.
As with the Ponseti method for clubfoot
correction1,
treatment begins with serial manipulation and casts, but with the forces
applied in exactly the opposite direction. All components of the deformity are
corrected simultaneously, except for the equinus, which should be corrected
last. The manipulations and cast applications are usually performed in the
outpatient clinic setting. The baby often cries during manipulation and must
be picked up by a parent and comforted before the cast can be applied. It is
helpful to have one parent beside the baby during the manipulation and casting
to offer a pacifier or a bottle of milk. If the baby is breastfed, he or she
should be nursed before manipulation. The more relaxed the baby, the better
the cast that can be applied. Occasionally, in patients who are more than
eighteen months of age and are not interested in being still, the serial casts
are applied with the patient under general anesthesia because of the
difficulty in holding the patient's knee in flexion while the plaster
sets.
The baby is placed supine on the clinic table with the feet at the end of
the table and enough room whereby the assistant can be on one side of the baby
and a parent can be on the other side. It is crucial for the manipulation that
the treating physician be able to palpate the head of the talus, which in a
child with congenital vertical talus is located on the plantar-medial aspect
of the midfoot. The thumb of one hand is placed on the head of the talus for
counterpressure while the other hand gently stretches the foot into plantar
flexion and inversion (Figs. 2-A, 2-B, and
2-C). The heel should not be touched, in order to allow the
calcaneus to slide from a valgus to a varus position under the talus. After
two to three minutes of gentle manipulation, a thin, well-molded long leg
plaster cast is applied over a thin layer of soft cotton in two sections. The
tightness of the ligaments gradually decreases during cast immobilization.
During the plaster cast application, an assistant holds the thigh with one
hand and holds the toes with the thumb and index finger of the other hand,
maintaining the knee in 90° of flexion. A two-inch-wide (5.1-cm-wide) roll
of soft cotton is wrapped by the treating orthopaedist, starting at the toes
and proceeding to the proximal part of the thigh. Only a thin layer of cotton
is applied so that the physician can still easily palpate the osseous
landmarks in the foot, which allow careful molding of the plaster cast. A
two-inch (5.1-cm) fast-setting plaster bandage, moistened in lukewarm water
but not wrung out, is wrapped over the cotton, starting at the toes and ending
distal to the knee. Keeping the plaster very moist allows better molding than
if the plaster dries while it is being applied. The plaster is smoothed with
one hand after every wrap around the foot and ankle, which also optimizes the
ability to obtain a good mold. One roll of two-inch (5.1-cm) plaster is enough
to cover the leg in most infants and children less than six months of age. For
children more than six months of age, a three-inch (7.6-cm) plaster may be
used. One should avoid the temptation to put on more plaster; a thicker cast
is more difficult to mold. The plaster should be wrapped around the
assistant's fingers to prevent the cast from being too tight on the toes.
The foot is held by the assistant in the position achieved earlier by
gentle manipulation while the plaster cast is applied. It is important for the
assistant to hold the foot in the position achieved by manipulation as the
cast is applied. If the orthopaedist has to manipulate the foot into position
after the plaster is applied, then the cast mold will be poor and there is a
potential for pressure sores under the cast. The treating physician then takes
the foot from the assistant and carefully molds the plaster cast. The
assistant should place a hand on the knee and should provide slight
countertraction as the orthopaedist molds the foot into equinus and adduction.
The cast is gently molded over the malleoli as well as over the head of the
talus and the arch and above the calcaneus. It is important that these areas
are molded precisely to avoid creating pressure sores. Once the plaster has
set, the cast is extended above the knee, covering the thigh, with the knee in
90° of flexion. A single three-inch (7.6-cm) plaster bandage is usually
enough to complete the long-leg portion of the cast.
Four to six plaster casts, changed weekly following gentle manipulations,
are necessary to loosen the dorsal and lateral ligamentous structures of the
tarsus. With each successive cast, the foot is brought into more equinus,
hindfoot varus, and forefoot adduction. In the last cast, prior to any
surgical intervention, the foot should be in a position of maximum plantar
flexion and inversion to ensure adequate stretching of the contracted
dorsolateral tendons, joint capsules, and skin
(Fig. 3). The foot in this
position simulates the position of a clubfoot. A lateral radiograph of the
foot should be made while the limb is in the last cast to ensure reduction of
the navicular on the head of the talus. As the navicular is not ossified in
infants, an indirect radiographic measurement (the talar axis-first metatarsal
base angle on the lateral radiograph) is used.
Kirschner Wire Fixation of the Talonavicular Joint
If the talonavicular joint has been reduced in the last plaster cast (a
talar axis-first metatarsal base angle in maximum plantar flexion of
<30°), the patient is scheduled for surgery the following week for
fixation with a percutaneous Kirschner wire to hold the talonavicular joint in
the reduced position (Fig. 4).
Once in the operating room, the patient is placed supine on a radiolucent
operating table. The entire lower extremity is prepared and draped. A single
Kirschner wire is placed retrograde from the navicular into the talus with the
foot held in maximum plantar flexion. The wire is cut and buried underneath
the skin for later removal in the operating room. Accurate placement of the
Kirschner wire is based on the ability of the surgeon to palpate the head of
the talus and the navicular because these bones are primarily cartilaginous
and are difficult to visualize radiographically in infants. Intraoperative
fluoroscopy is used to ensure a talar axis-first metatarsal base angle of
<30° after Kirschner wire fixation and to confirm that the ankle is in
neutral dorsiflexion.
If the talonavicular joint is not reduced (the talar axis-first metatarsal
base angle in maximum plantar flexion is =30°) after six casts have
been applied, then an attempt is made in the operating room to lever the talus
into position percutaneously with a Kirschner wire that is placed into the
talus in a retrograde manner. If this is successful as seen radiographically,
then the talonavicular joint is held with Kirschner wire fixation as described
above. In our experience, closed reduction of the talonavicular joint is more
likely to fail when treatment is initiated after the age of two years or in
children who have multiple congenital anomalies. If the talonavicular joint
cannot be reduced by closed means, then a small, 2-cm medial incision is made
over the talonavicular joint and a capsulectomy of the talonavicular joint and
medial subtalar joint is performed (Fig.
5). Traction is applied to the forefoot in the plantar flexed
direction while an elevator is used to gently lift the talus to a horizontal
and reduced position (Fig. 6).
With the talus held in the reduced position, a Kirschner wire is then placed
retrograde across the talonavicular joint
(Figs. 7-A and 7-B). For
patients who require this open procedure, we now transfer the tibialis
anterior tendon from its insertion on the navicular to the dorsal aspect of
the talar neck with use of suture fixation of the tendon directly into the
talar neck. This is done through the same 2-cm skin incision that was used for
the talonavicular capsulectomy. The goal is for the transferred tibialis
anterior tendon to provide a dynamic correction of the talonavicular joint in
these more difficult cases.
CRITICAL CONCEPTSINDICATIONS:This technique has been used successfully in children with congenital
vertical talus from birth to the age of four years, regardless of associated
diagnoses. The upper age limit at which this technique can be successful has
yet to be defined.CONTRAINDICATIONS:There are no contraindications to attempting this technique in a child of
any age with the diagnosis of congenital vertical talus. Vertical tali that
are associated with syndromes and those that have had previous surgical
treatment tend to be more challenging to correct. However, this method of
correction does allow partial correction of the deformity, which limits the
amount of surgery needed to achieve correction of the deformity.PITFALLS:Difficulty palpating the bones of the foot in a small infant. The surgeon
must have a thorough understanding of the kinematics and pathologic anatomy of
the deformity.Failure to obtain a position of maximum hindfoot varus, hindfoot equinus,
and foot adduction in the last cast prior to talonavicular Kirschner wire
fixation. If this position is not obtained, then the dorsolateral soft tissues
will not be adequately stretched and the deformity will be more likely to
recur.Application of below-the-knee cast instead of a toe-to-groin cast. A long
leg plaster cast is needed to prevent the ankle and talus from rotating. In
addition, with the hindfoot in extreme equinus, short leg casts slip off the
leg.Failure to achieve perfect talonavicular reduction. Unlike the cast
correction of clubfoot, for which it has been shown that a perfect
radiographic result is not necessary for an excellent clinical outcome, this
is not true for the congenital vertical talus. If the talonavicular reduction
is not complete as seen radiographically, then there is a high recurrence
rate. For this reason, we recommend that the treating surgeon, when learning
this technique, make the small medial incision over the talonavicular joint to
directly visualize the reduction and gain confidence and experience as to when
the joint is anatomically reduced.Performing the Achilles tendon tenotomy without first securing
talonavicular joint reduction with a Kirschner wire. Bringing the ankle out of
equinus without having Kirschner wire fixation of the talonavicular joint
results in a loss of talonavicular reduction.Failure of parents to perform stretching exercises. Stretching exercises
have proved beneficial in maintaining the elongation of the dorsolateral soft
tissues and preventing recurrent deformities.AUTHOR UPDATE:The technique has changed since the original article was
published3 in that
we now pay more attention to achieving a complete reduction of the
talonavicular joint at the time of Kirschner wire fixation. If there is any
question about talonavicular reduction, we make a small medial incision over
the talonavicular joint to directly visualize the reduction. In cases in which
we perform a capsulectomy of the talonavicular and medial subtalar joints to
achieve reduction, we now transfer the tibialis anterior tendon from its
insertion on the navicular to the dorsal aspect of the talar neck with suture
fixation to provide a dynamic force working to maintain reduction of the
talonavicular joint. Because of our experience with Kirschner wires backing
out of the talonavicular joint in small infants, we now prefer to bury the
Kirschner wire underneath the skin at the time of talonavicular fixation. We
have also developed criteria to help the treating surgeon to decide when it is
appropriate to perform a fractional lengthening of the extensor digitorum
communis and/or the peroneus brevis tendon, which are discussed in detail
above. The last modification to the technique is that we recommend use of the
ankle-foot orthosis only after the child has reached walking age and not
before.
CRITICAL CONCEPTS
INDICATIONS:
This technique has been used successfully in children with congenital
vertical talus from birth to the age of four years, regardless of associated
diagnoses. The upper age limit at which this technique can be successful has
yet to be defined.
CONTRAINDICATIONS:
There are no contraindications to attempting this technique in a child of
any age with the diagnosis of congenital vertical talus. Vertical tali that
are associated with syndromes and those that have had previous surgical
treatment tend to be more challenging to correct. However, this method of
correction does allow partial correction of the deformity, which limits the
amount of surgery needed to achieve correction of the deformity.
PITFALLS:
Difficulty palpating the bones of the foot in a small infant. The surgeon
must have a thorough understanding of the kinematics and pathologic anatomy of
the deformity.Failure to obtain a position of maximum hindfoot varus, hindfoot equinus,
and foot adduction in the last cast prior to talonavicular Kirschner wire
fixation. If this position is not obtained, then the dorsolateral soft tissues
will not be adequately stretched and the deformity will be more likely to
recur.Application of below-the-knee cast instead of a toe-to-groin cast. A long
leg plaster cast is needed to prevent the ankle and talus from rotating. In
addition, with the hindfoot in extreme equinus, short leg casts slip off the
leg.Failure to achieve perfect talonavicular reduction. Unlike the cast
correction of clubfoot, for which it has been shown that a perfect
radiographic result is not necessary for an excellent clinical outcome, this
is not true for the congenital vertical talus. If the talonavicular reduction
is not complete as seen radiographically, then there is a high recurrence
rate. For this reason, we recommend that the treating surgeon, when learning
this technique, make the small medial incision over the talonavicular joint to
directly visualize the reduction and gain confidence and experience as to when
the joint is anatomically reduced.Performing the Achilles tendon tenotomy without first securing
talonavicular joint reduction with a Kirschner wire. Bringing the ankle out of
equinus without having Kirschner wire fixation of the talonavicular joint
results in a loss of talonavicular reduction.
Difficulty palpating the bones of the foot in a small infant. The surgeon
must have a thorough understanding of the kinematics and pathologic anatomy of
the deformity.
Failure to obtain a position of maximum hindfoot varus, hindfoot equinus,
and foot adduction in the last cast prior to talonavicular Kirschner wire
fixation. If this position is not obtained, then the dorsolateral soft tissues
will not be adequately stretched and the deformity will be more likely to
recur.
Application of below-the-knee cast instead of a toe-to-groin cast. A long
leg plaster cast is needed to prevent the ankle and talus from rotating. In
addition, with the hindfoot in extreme equinus, short leg casts slip off the
leg.
Failure to achieve perfect talonavicular reduction. Unlike the cast
correction of clubfoot, for which it has been shown that a perfect
radiographic result is not necessary for an excellent clinical outcome, this
is not true for the congenital vertical talus. If the talonavicular reduction
is not complete as seen radiographically, then there is a high recurrence
rate. For this reason, we recommend that the treating surgeon, when learning
this technique, make the small medial incision over the talonavicular joint to
directly visualize the reduction and gain confidence and experience as to when
the joint is anatomically reduced.
Performing the Achilles tendon tenotomy without first securing
talonavicular joint reduction with a Kirschner wire. Bringing the ankle out of
equinus without having Kirschner wire fixation of the talonavicular joint
results in a loss of talonavicular reduction.
Failure of parents to perform stretching exercises. Stretching exercises
have proved beneficial in maintaining the elongation of the dorsolateral soft
tissues and preventing recurrent deformities.
AUTHOR UPDATE:
The technique has changed since the original article was
published3 in that
we now pay more attention to achieving a complete reduction of the
talonavicular joint at the time of Kirschner wire fixation. If there is any
question about talonavicular reduction, we make a small medial incision over
the talonavicular joint to directly visualize the reduction. In cases in which
we perform a capsulectomy of the talonavicular and medial subtalar joints to
achieve reduction, we now transfer the tibialis anterior tendon from its
insertion on the navicular to the dorsal aspect of the talar neck with suture
fixation to provide a dynamic force working to maintain reduction of the
talonavicular joint. Because of our experience with Kirschner wires backing
out of the talonavicular joint in small infants, we now prefer to bury the
Kirschner wire underneath the skin at the time of talonavicular fixation. We
have also developed criteria to help the treating surgeon to decide when it is
appropriate to perform a fractional lengthening of the extensor digitorum
communis and/or the peroneus brevis tendon, which are discussed in detail
above. The last modification to the technique is that we recommend use of the
ankle-foot orthosis only after the child has reached walking age and not
before.
Fractional Lengthening of Extensor Tendons and Peroneal Brevis
Tendon
Once Kirschner wire fixation of the talonavicular joint is achieved, a
clinical assessment of passive ankle plantar flexion and forefoot adduction is
done. If plantar flexion is limited to <25°, fractional lengthening of
the extensor digitorum communis and tibialis anterior tendons is done at the
level of the musculotendinous junction through a small incision over the
distal part of the leg, proximal to the ankle joint. If passive forefoot
adduction is <10°, fractional lengthening of the peroneal brevis tendon
is performed at the musculotendinous junction. If these tendons are not
lengthened when indicated, they can act as deforming forces and can lead to
recurrent deformities.
Percutaneous Tenotomy of the Achilles Tendon
Once the talonavicular joint is reduced and stabilized with the Kirschner
wire, a percutaneous tenotomy of the Achilles tendon is used to correct the
equinus deformity (Fig. 8). The
patient is placed supine on the operating table while the assistant holds the
leg with the foot in dorsiflexion. We do not inject local anesthetic around
the tenotomy site prior to performing the tenotomy because injection raises
the skin and obscures the starting point for the tenotomy by making palpation
of the Achilles tendon more difficult. A Beaver eye blade (Becton Dickinson,
Franklin Lakes, New Jersey) is introduced by the surgeon through the skin onto
the medial edge of the Achilles tendon, about 1 cm proximal to its calcaneal
insertion (Fig. 9). Two types
of Beaver blades are commonly used for Achilles tendon tenotomies, and both
are illustrated in Figure 10.
The blade shown in Figure 10,
A, which is our preferred blade, has a rounded tip, which
may decrease the risk of neurovascular injury when compared with the more
pointed blade illustrated in Figure 10,
B. The cutting surface of the blade is pointing
proximally at this stage. The undersurface of the tendon is palpated with the
tip of the blade, which is then rotated 45° to allow the tendon to be
severed from ventral to dorsal. The angle of dorsiflexion of the ankle will
suddenly increase by 10° to 15°, and the equinus deformity will
correct. Advancing the blade too far laterally can place the peroneal artery
and/or lesser saphenous vein at risk (Fig.
9)2. The
Kirschner wire prevents loss of reduction of the talonavicular joint as the
hindfoot is brought into dorsiflexion.
A long leg cast is then applied with the foot in a neutral position and the
ankle in 5° of dorsiflexion. The cast is changed in the clinic at two
weeks, at which time a mold is made for a solid ankle-foot orthosis if the
child is of walking age. The orthosis is made in 15° of plantar flexion
and 15° of adduction at the midtarsal joint to help to maintain reduction
of the talonavicular joint once the Kirschner wire is removed. All patients
are also measured at this time for a night-time brace consisting of two shoes
connected by a metal bar. This is the same brace that is used in the
management of clubfoot patients who are treated with the Ponseti
method1. The only
difference is that the shoes are placed on the bar pointed straight ahead
rather than externally rotated as in the treatment of clubfoot. This allows
for an adduction stretch on the foot while in the brace. A new long leg cast
is then applied with the ankle in 10° to 15° of dorsiflexion and is
worn for three weeks, after which time the cast is removed in the operating
room and the Kirschner wire is removed through a small skin incision.
To help to prevent a recurrent deformity, the parents are given
instructions and a hand-out on how to effectively perform range-of-motion
exercises for the ankle and foot, emphasizing ankle plantar flexion and foot
inversion. The exercises are performed with the patient supine. The parent
uses one hand to stabilize the leg with the knee bent. The other hand is used
to grasp the heel and then to place the ankle into maximum plantar flexion.
The second exercise involves adducting the foot with one hand while
stabilizing the leg with the other. The parents repeat these exercises forty
times at a setting and perform the exercises at every diaper change. These
exercises have improved our ability to effectively maintain ankle motion and
foot flexibility achieved with casting and/or surgery. After the last cast is
removed, the patient is seen every three months until the age of two years and
then is seen every six months to one year until the age of seven years. After
the age of seven years, the patient is seen once every two years until
skeletal maturity is reached (Figs. 11-A
and 11-B). A solid ankle-foot orthosis is used for all of our
patients once they begin to walk. The orthosis is worn for walking (for twelve
to fourteen hours in a twenty-four-hour period) until the age of two
years.