CHAPTER 30
|
The Child with a Limb Deficiency
1557
prosthetic approaches to management. In children with type
I tibial deficiency who have been treated with knee disarticu-
lation and have a flare at the condyles, the prosthetic socket
consists of a nonischial weight-bearing design with rotational
control achieved through the intimate fit of the distal end of
the socket over the femoral condyles and a well-formed glu-
teal impression. Suspension is usually achieved with the use
of a segmented liner or bladder design that allows the wider
condyles to pass through, while maintaining pressure over the
femur just proximal to the condyles.
In cases in which the condyles are absent or there is the
need to fit with a transfemoral socket, rotational control is
achieved through proper contouring of the socket relative to
the femur—the musculature surrounding the femur has a slight
triangular shape in a cross-sectional view, with a flatter contour
on the lateral surface, especially proximally. This allows a lock-
ing of the musculature which, with proper socket fit, decreases
rotation. In addition, a silicone sleeve suspension may be used
in conjunction with a pull-through strap to secure the liner. If
all other procedures fail, a standard Silesian belt (around the
pelvis) may be utilized. The total elastic suspension (TES) belt
offers excellent suspension and flexibility of form, and it aids
in control of the prosthesis. However, the Silesian belt and TES
will interfere with grooming and toilet training.
In the knee disarticulation (or transfemoral) prosthesis
for children, there are differences of opinion as to when young
children are able to handle an articulated knee. Traditional
established practice is to first fit the child with a locked knee
and allow an articulating knee at approximately 3 to 5 years
of age. In contrast, Wilk et al. (157) advocate the use of artic-
ulating knees in children as young as 17 months. Children
as young as 11 months can be appropriate candidates for
articulated knees (155). The children learn how to handle
the knee very quickly, and there is very little need for any
type of device to temporarily stabilize the knee. The use of
a knee joint at this stage permits more normal development,
allowing bent-knee sitting, side sitting, crawling and kneeling
on hands and knees, and easier pull to a stand. With a pedi-
atric knee, children can reduce or eliminate a circumducted
gait pattern.
In type II cases, in which a tibial segment has been pre-
served or the fibula has been joined to the tibial remnant,
a modified transtibial prosthesis or a Syme prosthesis is uti-
lized. Unlike the standard transtibial design, the socket will
incorporate SC and suprapatellar proximal brim lines that
will aid in the control and stability of the knee and prevention
of a hyperextension moment, respectively. In some instances
in which knee stability is less than optimal, outside joints
and a thigh cuff or lacer may be required. These are used
as a last resort and often contribute to increased weakening
of the musculature as a trade-off for increased control and
alignment.
Authors Preferred Recommendations.
For patients
with no active knee extension and Jones type Ia tibial
deficiency (complete absence), the authors recommend knee
disarticulation and prosthetic fitting. The authors have not
seen any patients as described in the literature with com-
plete tibial absence yet the presence of adequate active knee
extension, but would recommend knee disarticulation and
prosthetic fitting for these patients as well because of its high
functional result compared to the poor functional results
reported for the Brown procedure. For patients with some
active knee extension and Jones type 1b or type 2 tibial defi-
ciency, the authors recommend waiting for the tibial rem-
nant to ossify, then performing a tibial–fibular synostosis in
an end-to-end fashion. At the same time as the synostosis,
a modified Boyd amputation is performed, with fusion of
the distal fibula to the calcaneus. If the proximal fibula is
proximally displaced, prominent, and if the knee has varus
deformity or instability, resection of the proximal fibula is
recommended as well.
Timing of the tibial–fibular synostosis, modified Boyd
amputation, and possible proximal fibular resection is under-
taken at approximately 1 year of age unless the proximal tibia
is unossified. The authors recommend fitting the child with
an unossified proximal tibia with an extension prosthosis
that accommodates the foot deformity and waiting until the
proximal tibia ossifies. This has the benefit of one definitive
surgical episode while allowing the child to walk at a nor-
mal developmental age and has the added benefit of saving
the toes for possible transfer to the hand if hand anomalies
coexist.
The authors have no experience with Jones type 3 tibial
deficiency but agree with Schoenecker that ankle disarticula-
tion and prosthetic fitting are appropriate. For Jones type
4 cases and a projected limb-length discrepancy of 5 cm or
less, the authors recommend early soft-tissue correction of the
foot deformity with later contralateral epiphysiodesis to achieve
limb-length equality. For those cases with a projected discrep-
ancy above 5 cm, Syme amputation and prosthetic fitting is
preferred.
Pearls/Pitfalls.
As mentioned previously, outcomes of
fibular centralization are poor. The literature suggests that
this almost uniformly results in a poor functional result and
subsequent knee disarticulation. Initial knee disarticulation in
patients without active knee extension results in less surgery
and a more functional result.
During tibiofibular synostosis surgery, a few points are
worth mentioning. The proximal fibula in these patients often
is proximally displaced and prominent laterally. The surgeon
should consider resection of this at the time of tibiofibular syn-
ostosis surgery so it does not cause difficulty with prosthetic
wear in the future. With regard to the technique of synostosis,
the authors have found that end-to-end apposition of the tibia
and fibula results in superior lower limb alignment for pros-
thetic fitting. The fibula usually needs to be slightly shortened
to take tension off of the soft-tissue structures to achieve this
alignment, which is of no consequence.
