SURGERY FOR DEVELOPMENTAL DYSPLASIA OF THE HIP

Open reduction of a dislocated hip is indicated when
closed reduction fails or when closed reduction would result in such
extremes of position that avascular necrosis would be a likely
consequence. It is also indicated in children older than 12–18 months,
when it is frequently combined with femoral shortening to decrease the
overall time of immobilization required to achieve remodeling of the
hip. Open reduction is indicated in a subluxated hip when abduction
fails to reposition the femoral head deeply into the true acetabulum;
in this instance, osteotomy of the pelvis or proximal femur is usually
performed simultaneously.

Failures of closed reduction under anesthesia that
obviously do not allow the femoral head to be centered in the
acetabulum or that result in extremes of position are easy to detect
and should be followed with prompt open reduction, preferably as a
continuation under the same anesthetic. In children younger than 12
months, closed reduction that results in a reduction that is stable but
not deep and concentric may be accepted initially. Follow these
reductions by arthrography in 8–12 weeks; if soft-tissue remodeling has
not occurred and the reduction is not congruent and deep, proceed with
open reduction.

The use of prereduction traction and femoral shortening in 1–3-year-old children is somewhat controversial (8,13,20,22,23,25).
Standard open reduction can be performed with relative safety in some
children, but many surgeons (including myself) elect femoral shortening
in a walking child because it allows prompt open reduction without
preoperative traction and with an extremely low incidence of avascular
necrosis. It also permits derotation of the anteverted femur, thus
stabilizing the reduction. This allows early ambulation and may speed
hip remodeling; both of these goals are admirable in a child who has
never had a reduced hip joint before surgery. Open reduction is
occasionally useful in diseases other than congenital hip dysplasia,
such as cerebral palsy or reconstruction following trauma or infection.

The use of preoperative traction, once so universally accepted, has been widely questioned in recent years (2,10,20);
I personally no longer use it. In general, open reduction and its
variants should be done without the use of blood transfusions. This
requires great care on the surgeon’s part. The use of X or 3X loupes is
valuable in the dissection, and electrocautery greatly facilitates
dissection without excessive bleeding. All tissues must be handled
extremely gently, and the surgeon should have a thorough knowledge of
hip anatomy. For children younger than 2–3 years, attempt a closed
reduction immediately before proceeding with an open procedure because
occasionally a stable reduction can be achieved with good long-term
prognosis for resolution of the dysplasia.

I prefer open reduction from an anterior approach
because capsulorrhaphy and other reconstructive procedures can easily
be accomplished. Open reduction from a medial (adductor) approach does
not give sufficient exposure for these essential parts of the operation
and is indicated only in very young children who will undergo prolonged
casting to maintain reduction while the capsulotomy heals and remodels.
The medial approach is not described here; see Chapter 3 and Ferguson’s (7) description for details.

Although the standard exposure is a classic
Smith–Petersen approach, I prefer a skin incision that falls in, or is
parallel and superior to, the inguinal crease. Inguinal incisions can
be extended medially and laterally, and they allow excellent deep
longitudinal exposure with a nearly undetectable scar that is hidden
beneath standard clothing. If open reduction and femoral shortening are
combined, the use of an inguinal incision for the open reduction and a
lateral incision for the femoral shortening yields a more cosmetic
appearance and permits simple removal of internal fixation devices
later through the lateral incision.

With the patient under a deep general anesthetic, gently
flex, lift, and abduct the femur with the knee flexed until reduction
is felt. In older children, the reduction is usually either definite or
unobtainable, but younger children may not have distinct stability.
Arthrography and fluoroscopy greatly improve assessment of the
reduction (Fig. 166.2). Occasionally,
percutaneous adductor-longus tenotomy enhances stability. If the hip is
unstable in less than 55° of abduction, strongly consider open
reduction. Full double-spica casting is safest in 90° to 100° of
flexion, neutral rotation, and less than 55° of abduction, which is
Salter’s (18,19) “human” position.

Change the cast every 6–8 weeks until fluoroscopy
demonstrates stability in the weight-bearing position. Usually, 12–18
weeks in a spica cast is required. Abduction bracing may be used
long-term, although there is no scientific evidence of its value in
this circumstance.

Management of the labrum is controversial. Occasionally,
the labrum may actually be inverted, but more often it is rolled and
hypertrophic. If an actual inversion can be demonstrated and it cannot
be adequately dissected to allow placement of the femoral head, use
axial (radial) incisions to allow part of the labrum to be teased out
of the acetabulum. This is rarely necessary. Do not excise the labrum
because it contributes to future growth of the acetabular rim.

Immobilize the child in a double-hip spica cast with the
legs in 30° of abduction, 20° of flexion, and gentle internal rotation (Fig. 166.3I).
The position is safe if the femur has been shortened and the iliopsoas
lengthened. After open reduction in older children, this extended
internally rotated position is more appropriate than the flexed “human”
position used after closed reduction.

Postoperative radiographs must show a reduced femoral
head, although the small ossific nucleus is often seen to be somewhat
inferior to its expected position. This results from the misshapen
femoral head and the hypertrophic labrum, and will remodel (Fig. 166.3J).
Casting for 6 weeks is usually sufficient to allow healing of any
osteotomy and development of satisfactory joint stability after open
reduction. Ambulation with or without abduction bracing, as the
clinical situation dictates, may begin immediately.

Femoral shortening is done during open reduction of the
hip to minimize the compressive force across the joint (thus decreasing
the risk of avascular necrosis) and to avoid preoperative traction in
older children. It is also done in combination with derotation
osteotomy to stabilize the reduction in the weight-bearing position (5,20,22).

I prefer a second longitudinal lateral incision for the femoral-osteotomy portion of the combined procedure (Fig. 166.4A).
This lateral approach is more cosmetic and facilitates plate removal,
if desired. However, the proximal femoral shaft can, with more
difficulty, also be reached anterolaterally through the lower arm of an
extended standard Smith–Petersen incision.

Proximal femoral derotation or varus osteotomy is
indicated in subluxation or dysplasia of the hip when reorientation can
stabilize a reduction, resolve mild subluxation, or stimulate
remodeling of the joint (4,5,12,22,25).
Often, it is used to achieve a congruent joint in the weight-bearing
position after closed or open reduction to allow a child of walking age
to ambulate with less risk of subluxation. When acetabular dysplasia
persists after reduction, femoral osteotomy can stimulate remodeling of
the acetabulum, if done by 5 years of age (12).
The choice of femoral or pelvic osteotomy in this situation is often a
matter of the surgeon’s personal preference; I prefer the pelvic
procedure.

The usual deformity of the femur in congenital hip
dysplasia is excessive anteversion. This contributes to anterolateral
subluxation in the weight-bearing position and encourages superolateral
subluxation in the sitting position. Femoral derotation alone is
generally sufficient to correct the deformity. This becomes obvious
when radiographs are taken with the legs internally rotated and a
normal neck–shaft angle (135°) is seen. If abduction is also necessary
to produce a congruent reduction, then varus can be added, as well.
Take great care not to overcorrect the femoral deformity. Avoid
retroversion; increased varus of greater than 20° is rarely indicated.
If a varus osteotomy is done, the hip must have an adequate range of
abduction to allow functional motion after surgery. In my opinion, the
prerequisites for femoral osteotomy in hip dysplasia are critical and
should be the same as those for innominate osteotomy: congruent
reduction of the hip and a full range of motion.

Internal fixation is necessary for femoral osteotomy.
Some have advocated single-screw fixation or multiple smooth pins, but
I strongly prefer rigid fixation with a small plate (for derotation
alone) or a pediatric blade plate (for a varus osteotomy in an older
child). This allows more accurate control of position during healing.

Pelvic osteotomy is indicated when there is primary
acetabular dysplasia, residual subluxation of the hip, or failure of
gradual improvement of radiographic dysplasia following reduction of a
dislocated hip. In general, pelvic osteotomy should be done when severe
dysplasia is accompanied by significant radiographic changes (high
acetabular index, failure of lateral acetabular ossification) on the
acetabular side of the hip joint, as opposed to changes on the femoral
side (e.g., marked anteversion), which are best treated by femoral
osteotomy (5). Surgical treatment of definite
hip subluxation by either pelvic or femoral osteotomy before age 4
years will be accompanied by at least partial remodeling and resolution
of anatomic abnormalities on the opposite surface of the joint (12).

Pelvic osteotomy is ideal for treatment of dysplasia
when expected remodeling has ceased (as assessed by serial radiographs)
and dysplasia or subluxation persists (5).
Often, after the hip is reduced, pelvic osteotomy can be postponed
until 4 years of age to allow adequate time for remodeling.

Pelvic osteotomy is also indicated when necessary to stabilize reduction during or after open reduction of the hip.

The many osteotomies described for acetabular dysplasia
may be categorized as indicated either for primary treatment of
dysplasia (Salter innominate osteotomy, Pemberton osteotomy, triple
innominate osteotomy) or for salvage of a poor result in the later
stages of dysplasia when complete remodeling is not expected (Chiari
osteotomy). The primary osteotomies are generally reorientation
procedures for the acetabulum, although the Pemberton procedure allows
actual diminution of acetabular volume at the expense of some
acetabular congruity. The Salter and Pemberton osteotomies are the most
common osteotomies performed in North America.

To be successful as a primary treatment of dysplasia, an
osteotomy must be done only in the presence of a congruent reduction,
satisfactory range of motion, and reasonable femoral sphericity. These
prerequisites have been popularized primarily by Salter (18,19)
for his innominate osteotomy, and they are appropriate preoperative
goals for any primary osteotomy about the hip (acetabular or femoral).

The Salter and Pemberton osteotomies differ somewhat in
concept, although both are designed to limit anterolateral subluxation
by improving coverage in this area. The Salter osteotomy, because it
goes completely through the pelvis, allows anterior and lateral
rotation of the acetabulum through an axis formed by the sciatic notch
and the pubic symphysis. There is a limit to the degree of correction
that can be obtained, and the procedure does not change acetabular
shape (17). Conversely, the Pemberton osteotomy
is an incomplete osteotomy that hinges the anterolateral acetabular
roof on the flexible triradiate cartilage for correction (16).
This actually changes the configuration of the acetabulum and
introduces joint incongruence that must be corrected by remodeling
during growth. For these reasons, the Pemberton procedure may be
indicated when there is an elongated, dysplastic acetabulum, but it is
most effectively done in children younger than 8 years, as there is
still flexibility in the triradiate cartilage and growth remains for
remodeling of the joint surfaces (29).

In older children with deficient, dysplastic acetabulae
but a relatively congruent reduction, the Salter osteotomy does not
provide sufficient angular correction to improve stability. When the
triradiate cartilage is closed, the Ganz periacetabular osteotomy (see Chapter 104)
can achieve the extremes of reorientation required. When the triradiate
cartilage is open, the same freedom to reorient the acetabulum in space
can be achieved by cutting the ischium and pubis in addition to the
ilium (triple innominate osteotomy). Variations of this technique have
been described by Steel (24), Tönnis et al. (28), and Tachdjian (25). All are complex operations that should not be attempted by an inexperienced surgeon.

In older children, salvage of a hip that is too deformed
to remodel for the growth time remaining requires a different type of
procedure. The Chiari (3) osteotomy is probably
the most commonly used operation. It is a displacement osteotomy that
essentially provides a shelf or buttress to limit further proximal
subluxation of the femoral head. The superior hip capsule provides an
interpositional surface between the cancellous bone of the shelf and
the femoral head, and the capsular tissue may undergo metaplasia into
fibrocartilage. Thus, the functional size of the acetabulum can be
increased by the operation. If done properly, the Chiari osteotomy also
moves the hip joint center medially and improves the mechanical
advantage of the abductor muscles, both of which tend to decrease the
intra-articular resultant force across the hip joint. The Chiari
osteotomy does not require a concentric reduction; it may be done above
a subluxated hip. The chief indication for Chiari osteotomy is pain
associated with a subluxated, dysplastic hip in an older child. It
should not be performed if degenerative changes are present or the hip
is stiff. Do not do a capsulotomy at the same time as a Chiari
osteotomy.

The exact indications for salvage surgery in congenital
hip dysplasia are controversial. The goal of surgery most often stated
is to treat chronic hip pain in an adolescent who has significant
dysplasia as seen on radiographs. For many surgeons, another
appropriate indication is radiographically demonstrated progressive
subluxation, often associated with increasing degenerative changes of
the hip. Although it may be unwise to consider surgery in an adolescent
who has no pain, regardless of the radiographic appearance of the hip,
there are surgeons who are exploring the use of late reconstructive
procedures (e.g., the Ganz osteotomy) in asymptomatic patients who have
severe radiographic dysplasia (see Chapter 104).

Remove the cast 8 weeks after surgery (Fig. 166.9).
Allow weight bearing as tolerated. Physical therapy is unnecessary.
Older children may exhibit transient stiffness of the hip joint because
of changes in the acetabular surface configuration caused by the
Pemberton osteotomy.

General approaches to the variations in triple innominate osteotomy are presented here (24,26,28). These are highly specialized operations, and their powerful ability to reorient the acetabulum can lead to overcorrection (6).
There is also significant potential risk of neural and vascular injury;
these are not operations for the inexperienced. Of the operative
approaches, I prefer Tachdjian’s (26), but each has its proponents. For fully detailed descriptions, readers are referred to the originators of each approach (24,26,28).

Perform a Chiari (3) osteotomy on a radiolucent table with AP image-intensifier control.

The original osteotomy described by Chiari (3)
was straight from the front to the back of the pelvis. Most surgeons
(including myself) prefer a curved cut, which limits anteroposterior
sliding of the osteotomy. However, if the cut is made as a conical
rather than cylindric curve three-dimensionally, the fragments will not
displace; therefore, accurate three-dimensional control is mandatory.