CHAPTER 30
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The Child with a Limb Deficiency
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Both of these procedures have had limited use. There are
significant problems in achieving an arthrodesis, and the distal
femoral segment cannot be allowed to grow too long. Additional
surgical procedures are to be expected. As yet, there are only
very limited reports on the functional advantages (190, 191).
Prosthetic Management.
Initial prosthetic management of
the child with PFFD begins with fabrication of an extension or
nonstandard prosthesis, with or without an activated knee joint
(Fig. 30-33). With the foot positioned in plantar flexion, the
limb is cast proximal to the hip joint, and the prosthesis fab-
ricated with a prosthetic foot positioned under the shortened
limb. The ischial containment socket has been called a “ship’s
funnel” because of the resemblance to the engine air intake
funnels of ocean vessels. This drastic socket design is neces-
sary because of the flexed hip and knee that must be contained
within the socket while attempting to gain ischial support.
The purpose of the extension-type prosthesis is to equal-
ize limb length, in preparation for early ambulation, while
affording time for surgical decisions. There are four indications
that have been identified relating to the fitting of nonstandard
prostheses (192):
1. When the patient is still too young for surgical conversion.
2. When the patient or parent refuses surgical intervention,
and a prosthesis is necessary for ambulation.
3. In bilateral cases, when extra height or better balance is the
goal.
4. When there is lower extremity involvement, combined
with bilateral upper extremity absence, requiring the feet
for ADL.
When foot ablation with knee fusion option is chosen, the
prosthesis resembles a knee disarticulation prosthesis, except
for the need for ischial weight bearing and high lateral brim
containment to aid in hip stability. Weight bearing is divided
between the ischium and the distal heel pad. Full distal weight
bearing could severely compromise hip function over a period
of time, because of the inherent instability of the hip with pos-
sible proximal migration of the femur. Prosthetically, fusion of
the knee with correction of the angular deformities results in
improved gait and ease of fitting because of the single skeletal
lever arm (193). During growth, the child should be evaluated
periodically for the relative length of the two limbs so that, if
needed, distal femoral epiphysiodesis can be performed. This
will allow fitting of an optimal knee joint when the patient is
fully grown while maintaining the knees at the same level.
In the small child, and when the residual limb is longer
than the opposite femoral segment, external knee joints may
be used. As the child grows, an internal four-bar knee can be
used. More about the indications and selection of knee joints
is discussed later in this chapter.
A foot amputation without knee fusion results in dif-
ficulty with prosthetic management. Movement within the
prosthesis, at the level of the anatomic knee, and the increased
need for an intimately fitted socket, foster a decreased stride
length and increased pelvic movement. However, in the child
with an Aitken class D PFFD and only a remnant of distal
femoral epiphysis in which knee fusion will have little to offer,
this may be a suitable choice.
The Van Nes rotationplasty requires a nonconventional
prosthesis with the ankle functioning as the new knee. This
is a very difficult prosthesis to align and fit, although it gives
excellent function (177, 194). The prosthesis has a lower
padded foot socket that contains the rotated foot in full plan-
tar flexion. Lateral and medial external joints are attached to
the upper thigh section to increase stability and to prevent
hyperextension of the lower shank (194). The original design
incorporated a laminated thigh section with ischial weight
bearing. For patients with good hip stability, for example, in
those who had a tumor and trauma, the laminated section
is often replaced with a leather thigh lacer and no ischial
weight bearing. It is imperative for proper function that the
external joints be aligned with the axis of rotation of the
ankle/subtalar complex while maintaining the line of pro-
gression. Failure to ensure this alignment, regardless of the
anatomic joint, will result in a poor gait pattern and skin
breakdown. The prosthetist should incorporate mechanical
joint placement with slight external rotation on a new pros-
thesis, in anticipation of the mild internal derotation inevi-
table during growth.
Author’s Preferred Recommendations.
Children with
more severe forms of femoral deficiency are initially fit with an
extension-type prosthesis until the age of approximately 3 years.
For children with a congenitally short femur with <20 cm of
anticipated limb-length discrepancy at skeletal maturity, an arc
of motion of the knee of 60 degrees without flexion contrac-
ture, and a foot that is plantigrade or can be made plantigrade
with surgery, the authors suggest limb lengthening. Hip and
proximal femoral stability are achieved first by redirecting or
augmenting the acetabulum as necessary and repairing a proxi-
mal femoral pseudarthrosis and/or varus if it exists.
For patients where the foot falls at the level of the contralat-
eral knee, the authors suggest Van Nes rotationplasty and knee
fusion if the family is accepting the idea and the ankle/subtalar
joint complex has at least a 60 degrees arc of dorsi/plantar flex-
ion and no equinus contracture. If the family is unaccepting of
rotationplasty, or if the foot and ankle are not well-aligned and/
or lack sufficient range of motion, then knee fusion with Boyd
amputation is undertaken. Careful prediction of the ultimate
length of the tibial and femoral segments guides the decision
of which epiphyses and physes to remove at the time of knee
fusion. In the majority of cases, both physes will be removed.
The authors do not have sufficient experience with ilio-
femoral arthrodesis with or without rotation to recommend
either procedure.
Pearls and Pitfalls.
In evaluating these patients, it is
important to accurately predict the ultimate limb-length dis-
crepancy as early as possible. This is essential in formulating an
early treatment plan. Because of the flexion, abduction, and
external rotation deformity of the proximal femoral segment,
