Congenital spinal deformities are among the most difficult deformities to
treat. They are a challenge both from a decision-making and a technical point
of view. Many deformities do not require any treatment short of investigation
and observation, but, at their worst, they will challenge the surgeon
technically and cognitively. The variety of combinations of congenital
deformities seems limitless and therefore makes the prediction about what will
happen with growth very difficult. In this article, the principles of
nonoperative and operative management will be discussed.
Observation is appropriate when the natural history suggests that the curve
will not worsen to an extent that will lead to a clinically important
deformity. This has been discussed elsewhere in this symposium and will not be
further discussed here.
The other form of nonoperative management is bracing. Bracing plays a very
limited role in the management of congenital scoliosis, especially as a
primary form of
treatment1. It is
often added as a supplement to surgical treatment.
Bracing is sometimes used to control secondary curves when the primary
congenital curve has not been treated surgically. Occasionally the
noncongenital curve progresses on its own and will respond to bracing. Bracing
may also be used to prevent progression of a secondary curve that is causing
balance problems.
The surgical management of a congenital spinal deformity can be divided
into two categories. There are procedures that prevent further deformity and
those that correct the present deformity. In the latter type, there are
techniques that correct the curve gradually and those that correct the curve
acutely. Fusion in situ is the classic example of a procedure that prevents
further deformity. Convex anterior and posterior hemiarthrodesis allows
gradual correction, while hemivertebra excision and osteotomy allow acute
correction.
As a guiding principle, it is safe to say that it is easier to prevent a
deformity than to correct a
deformity2,3.
It is almost always better to stabilize a curve when it is small, and thus
prevent it from worsening, than to allow it to progress and then decide to
correct the deformity when the child is larger.
Ultimately, decisions will be driven by the classification of the
congenital deformity, its location, the growth remaining that will allow
worsening, and the initial curve magnitude. Briefly, congenital deformities
can be divided into three categories: failures of formation, failures of
segmentation, and mixed patterns. A fully segmented hemivertebra represents
the classic failure of formation, while a unilateral bar is a prime example of
failure of segmentation.
In Situ Fusion
In situ fusion allows stabilization of a curve that is predicted to worsen
or has been documented to have already worsened. It is the ideal form of
treatment for small curves and is done at an appropriate time to prevent a
curve from becoming unacceptably large. The ideal patient for this procedure
has a unilateral unsegmented bar. There is no hope to get the congenitally
fused side growing again. Therefore, as long as the curve is not unacceptably
large or unbalanced, stopping the growth on the convex side is the simplest
and safest solution. Fusion should be accomplished very early, before a
significant curve develops, making a more extensive correction necessary. This
is particularly true if there is a contralateral hemivertebra, for which
fusion may be best done in the first year of
life4.
One of the major controversies surrounding in situ fusion is whether or not
a combined anterior and posterior fusion is
required4. There is
less potential for anterior growth in a spine with congenital scoliosis
because the growth plates may not be properly formed. Posterior fusion is
known to lead to progression of deformity in some young children due to the
crankshaft phenomenon, as reported by Dubousset et
al.5. In an in situ
fusion for congenital scoliosis, a shorter segment is fused and there is also
less rotation in the segment, which makes a true crankshaft phenomenon
unlikely to occur.
Posterior in situ fusion is accomplished by decorticating the spine and
doing facet fusions. This may be done at the level cephalad to and caudad to
the hemivertebra or, in the case of a unilateral bar, along the entire length
of the bar4. If
anterior fusion is added, it may be done as an open procedure in which the
intervertebral discs cephalad to and caudad to the hemivertebra are excised.
They will be found to come together, forming a Y on the contralateral side of
the spine. Thoracic discectomies may be done endoscopically. The segmental
arteries may be spared, but care must be taken because abnormal vessels may be
found. Anterior fusion may also be accomplished through a transpedicular
approach as popularized by
Lindseth6. If there
is flexibility in the curve through the area being fused, a Risser cast may be
used postoperatively to encourage the spine to fuse in a slightly corrected
position. Use of a cast is usually not necessary after an isolated fusion in
situ but may be helpful after a hemiepiphysiodesis and/or hemiarthrodesis or
after a fusion of the extended curve without instrumentation.
The decision regarding which curves may be fused in situ is sometimes
difficult. The likelihood of progression and the location of the curve must be
considered, as well as what effect the curve will have on the balance and
cosmetic appearance of the child. Deformities at the lumbosacral and
cervicothoracic junction are more likely to lead to cosmetically displeasing
deformities and therefore should be fused in situ very early or treated in
other ways.
Correction may be gradual, allowing growth to correct the spine, or it may
be immediate or acute. Gradual correction is obtained through the use of a
hemiepiphysiodesis and/or hemiarthrodesis of the spine. Immediate or acute
correction may be accomplished through several different techniques. Removal
of the hemivertebra may be accomplished through excision or decancellization.
Acute correction may also be achieved through the application of
instrumentation, which may either be definitive or staged with use of a
growing rod. For fixed deformities, it may be necessary to perform an
osteotomy to balance the spine and correct the cosmetic deformity.
The use of a chest-wall distractor known as a vertical, expandable
prosthetic titanium
rib7 is another
alternative, but this instrument will not be discussed in this section as it
is discussed elsewhere in this symposium, in the article on thoracic
insufficiency syndrome by Campbell and Smith.
Gradual Correction Techniques
Hemiepiphysiodesis and Hemiarthrodesis
These techniques are used for failure of formation. There is no role for
their use in failures of segmentation unless the pattern is of a mixed type.
Correction of deformity relies on the future growth of the spine on the
concave side; in deformities due to failure of segmentation there is really no
potential for growth to occur.
These techniques are best utilized to treat a single hemivertebra vertebra
that has not caused a large curve at the time of surgery. These techniques
should not be considered for curves that are =50°. As the techniques
require future growth, the child must have adequate growth potential
remaining, and therefore the procedures are best reserved for children who are
five years of age or
younger6,8,9.
The portion of this procedure that deals with the anterior aspect of the
spine may be accomplished either through an
open8,10,
endoscopic11, or
transpedicular
approach6 or
simultaneously through a costotransversectomy
approach2. The goal
is to arrest the growth on the convex side of the curve. This is best
accomplished through the excision of between one-third to one-half of the disc
as well as the end plates cephalad to and caudad to the hemivertebra. As the
growth potential of the opposite side may be limited, it is best to include a
normal disc above and below the hemivertebra to increase the likelihood of
creating unbalanced growth. The posterior procedure includes decortication of
the hemilamina on the convex side and facetectomy and fusion. The concave side
of the spine is not exposed surgically, as doing so could lead to spontaneous
fusion.
If the choice is to do the anterior fusion through a transpedicular
approach, then the child may be positioned prone. Through a posterior
approach, straight curettes are used to open the pedicle and then curved
curettes are used to break through the end plates to remove some of the body
on the convex side. The holes in the end plates are enlarged, and disc
material is also removed. Cancellous bone graft from the posterior iliac crest
is inserted into the channels created to bridge the disc spaces. Keller et al.
reported that this hemiepiphysiodesis procedure is less predictable than
other, more extensive procedures but that the complications may be
fewer6. The
advantage is that it avoids an anterior procedure and associated morbidity.
They also point out that it may be used for upper thoracic curves where
exposure is difficult with a thoracotomy.
As the child grows, the growth will be unbalanced with a surgically created
growth arrest on the convex side. The curve will then gradually improve with
time.
A cast or brace may be used postoperatively to encourage fusion of the
spine in a somewhat corrected position, which will therefore improve the
starting point and permit the ultimate correction to rely less on the growth
of the spine (Figs. 1-A and
1-B).
One of the complications of this procedure is failure to achieve
correction. Roaf reported that 60% of his patients had correction of at least
10°2. In the
study by Keller et al., 37% of the curves improved, 42% remained unchanged,
16% progressed between 10 and 15°, and only 5% progressed more than
15°6. In the
study by Winter et al., the curves in five of thirteen patients showed steady
improvement over time and a gain of correction of at least 5° beyond that
gained by casting, indicating a true epiphysiodesis effect; seven showed
cessation of progression of the curve but no improvement over time, indicating
a fusion effect; and only one had an increase of deformity, indicating
failure. The average correction due to the epiphysiodesis was 10° (range,
5° to
20°)12.
Thompson et al. also had a high success rate. Seventy-six percent of their
thirty patients had improvement in the Cobb
angle13. There was
also an average rate of curve improvement of 1.2° per year following the
operation, whereas the average worsening prior to the operation had been
1.9°. In their series, there was better improvement in the lumbar curves
than in the high thoracic, thoracic, or thoracolumbar curves.
Preoperative kyphosis is a relative contraindication to this procedure
because anterior growth arrest will prevent spontaneous correction of the
kyphosis6. Not all
believe that kyphosis is a contraindication, however, and some recommend that
this procedure may be done even in the presence of a
kyphosis14.
This procedure may also be used with the insertion of a growing rod for
children who have a more extended and extensive curve. This scenario is
discussed below.
Growing Nonfusion Rod
This is not a technique that is commonly used in the treatment of
congenital scoliosis. The congenital anomaly may lead to an extended curve,
especially if the anomaly has been missed or the treatment delayed. If the
child is still very young, the primary congenital curve can be treated with
fusion in situ, hemiepiphysiodesis and/or hemiarthrodesis, excision, or
osteotomy, and the extended curve can then be treated with a growing rod until
the child is older. This avoids fusing the entire curve, which will lead to
growth retardation and potentially harmful pulmonary effects.
Many instrumentation patterns for nonfusion, or growing, rods are used.
Akbarnia and
McCarthy15
popularized the double-rod system. The basic goal is to straighten the
extended curve with instrumentation but without extensive fusion, thus
permitting the spine to continue to grow. The rod needs to be lengthened as
the child grows. An apical fusion involving the congenital anomaly may also be
added; this will obtain control of the apex of the curve and, if a
hemiepiphysiodesis and/or hemiarthrodesis is used, possibly permit improvement
of the apical curvature with growth. Fusion of the apex is mandatory if the
apical curvature is due to failure of segmentation.
Acute Correction Techniques
Instrumentation and Fusion
Some believe that congenital curves should not be instrumented, whereas
others have a contrary opinion and will straighten congenital
curves16. The goal
is not to make the spine as straight as possible but to achieve whatever
correction is safe and to balance the patient. Choosing levels is most
difficult when there are multiple noncontiguous anomalies. The whole curve
must be fused, but there may be abnormal segments cephalad or caudad to the
curve that will not be included or two curves may need to be included in the
instrumentation. Care must be taken not to overcorrect one curve at the cost
of unbalancing the patient. Special care must be taken when there is a
congenital anomaly in the high thoracic or cervical region. Overzealous
correction of a lower thoracic or thoracolumbar curve may lead to very serious
shoulder imbalance or obliquity of the neck. The remaining part of the spine
that is not being fused may not behave in the same manner as would be expected
of an idiopathic scoliosis.
Preliminary traction may sometimes help reveal what may be corrected safely
without unbalancing the child; this is particularly useful if there is an
intraspinal abnormality that has been treated prior to surgical stabilization
of the spine. Prior to instrumentation, the status of the spinal cord must be
assessed with magnetic resonance
imaging17.
Determining fixation points may be a challenge, depending on the anatomy.
Occasionally, intraspinal abnormalities must be dealt with prior to the
instrumentation procedure. Computed tomography with sagittal, coronal, and
three-dimensional reconstructions is very helpful for the assessment of local
anatomy and as an aid in planning the implants. It is important to have a full
selection of implants during this operation because pediatric implants may be
needed at one level while an adult-size implant may be required at another
(Figs. 2-A through 2-F).
If there is any concern about the patient's neurological status, fusion in
situ with instrumentation is an option that will provide stabilization but no
correction.
Hemivertebra Excision
Removal of a hemivertebra is now a popular procedure because it results in
immediate and often excellent correction of the
deformity18-21.
It removes the cause of and prevents further worsening of the deformity. The
difficulty is in deciding when this more invasive procedure is necessary. When
detected early, many curves may be stabilized by a much more simple procedure
that has lower risks for the patient. The stabilization of this type of
deformity early will often result in no serious deformity or balance problems.
Sometimes it is necessary to resist the temptation to make things look better
radiographically at the expense of putting the patient at risk.
The ideal indication is the hemivertebra at the lumbosacral junction, as
this particular deformity often leads to major imbalance or very serious
compensatory curves. Hemivertebra excision may also be the best procedure for
curves that have been ignored and have already created significant deformity
or imbalance.
Various techniques are described for removal of a hemivertebra. It may be
removed through a combined anterior and posterior approach, either
simultaneously or in
stages20,21.
It may also be dealt with posteriorly through a costotransversectomy approach.
As mentioned above, it may also be dealt with by the so-called eggshell
procedure, in which the hemivertebra is decancellized and then the shell is
collapsed to correct the deformity. If combined anterior and posterior
excision is chosen, it may be staged with the anterior procedure done first
and completed with the posterior stage done one or two weeks later. The
proponents of staged surgery state that the interval between the operations
allows for reconstitution of the blood supply and decreases the prevalence of
spinal cord injury; however, others believe that it is safe to perform both
approaches under the same anesthetic. The anterior resection removes the
hemivertebra and the discs cephalad to and caudad to the hemivertebra along
with the pedicle. The posterior excision removes the lamina, facets,
transverse process, and any residual pedicle that has been left behind.
My preference is to perform a single procedure, exposing the hemivertebra
both anteriorly and posteriorly at the same time. The patient is placed on his
or her side and the anterior approach is done first. Once the anterior
exposure is accomplished, a straight posterior approach to expose the
posterior elements is completed. Next, the anterior elements are removed. The
anulus on the concave side may be preserved to act as a restraint to prevent
lateral translation of the spine. A temporary rod may then be placed on the
concave side posteriorly to add stability and prevent any sudden movement of
the spine. The posterior elements are then removed, and a convex rod is used
to compress the remaining gap. Anterior instrumentation may also be considered
if the size of the vertebra allows placement of screws. Kyphosis is a relative
contraindication to the addition of anterior instrumentation unless a cage is
also added. If the child is too small for posterior instrumentation,
sublaminar fixation around the lamina cephalad and caudad may be considered;
wires, cables, or heavy sutures may be used to pull the two laminae together.
If the child is too small for any instrumentation at all, a cast may be used.
It must include at least one leg and may be wedged postoperatively to obtain
more correction.
The potential complications from hemivertebra excision are severe and must
be carefully considered when developing a treatment plan for the individual
patient10,22.
Blood loss from segmental bleeding or epidural bleeding may be excessive. The
most severe complication is that of neurological injury. Lumbar excision is
safer than thoracic excision because the cauda equina is much more resistant
to injury than is the spinal cord.
Hemivertebra excision may be combined with other procedures if there is an
extended curve that needs to be treated. It is possible to combine this
procedure with a convex hemiepiphysiodesis and/or hemiarthrodesis, with use of
a nonfusion rod or definitive instrumentation of a longer curve.
Osteotomy
For fixed deformities that leave the patient with an unacceptable cosmetic
appearance, osteotomy may be
considered23.
Osteotomy may be combined with other procedures, such as hemivertebra
excision, or it may be done as the sole procedure. These are truly salvage
procedures and should probably only be considered when treating severe
imbalance. They should only be considered for curves for which no other
solution is possible and should only be contemplated by experienced spinal
surgeons. A curve that may be cosmetically displeasing but that has left the
patient well balanced is probably best treated with stabilization alone.
Each deformity will be unique and will often involve more than just an
osteotomy. An osteotomy may be part of a combined approach that involves
resection of the hemivertebra and instrumentation and fusion of a more
extended curve. The principles of osteotomy involve cutting through the
anterior fusion mass in the absence of segmentation and resecting enough bone
to allow correction of the deformity. Through a posterior incision, the
osteotomy is done to match the one in front. Temporary stabilization with a
rod on the concave side is always a safe approach to prevent sudden
translation of the spine. Compressive instrumentation then allows closure of
the osteotomy. Care must be taken not to compress the neural elements as the
osteotomy is closed. Once the osteotomy is closed, further instrumentation
cephalad and caudad to the osteotomy site may be placed to balance the spine
and deal with the extended curve. Bone-grafting is the final step to ensure
solid healing and long-term survival of the repair. ?