Extract
Children with early onset scoliosis present with the deformity in the first
five years of life. Radiographic criteria may be helpful to distinguish
between the curves that will progress from those that will spontaneously
resolve. Severe cardiopulmonary problems can occur in patients with untreated
progressive curves. A comprehensive evaluation should be performed to identify
the true cause of the deformity, including any conditions that are commonly
associated with early onset scoliosis.
Children with early onset scoliosis present with the deformity in the first
five years of life. Radiographic criteria may be helpful to distinguish
between the curves that will progress from those that will spontaneously
resolve. Severe cardiopulmonary problems can occur in patients with untreated
progressive curves. A comprehensive evaluation should be performed to identify
the true cause of the deformity, including any conditions that are commonly
associated with early onset scoliosis.
Progressive curves of =20° may require the use of magnetic resonance
imaging to assess for occult lesions of the central nervous system. Surgical
treatment of spinal deformity should be considered when nonoperative measures,
including bracing and casting, are not indicated or fail to arrest curve
progression. Surgical methods continue to evolve and are primarily directed at
obtaining and maintaining curve correction while simultaneously preserving or
encouraging spinal and trunk growth.
There are three surgical options for the treatment of early onset
scoliosis: spinal fusion to halt the growth of the spine entirely,
hemiepiphysiodesis or temporary tethering to cause a convex arrest of growth,
and the use of growing-rod instrumentation to allow spinal growth by way of
distraction.
In 1954, James described the three types of idiopathic
scoliosis—infantile, juvenile, and adolescent—on the basis of the
age of onset: infantile denotes curves that develop at three years of age or
less; juvenile, those that develop between four and nine years of age; and
adolescent, those that occur between ten years of age and the time at which
growth is complete1.
These three periods correspond to distinct periods of growth during childhood
and adolescence. The infantile and adolescent periods are marked by an
increased growth velocity, whereas most of the juvenile period, in contrast,
correlates with a deceleration of spinal growth. Consequently, the onset of
scoliosis is relatively uncommon during the juvenile
period2,3.
Dickson used the term "early onset" to reflect the presence of
scoliosis by five years of age and "late onset" for the appearance
of scoliosis at six years of age and
older4. The term
"early onset scoliosis" appears to be more descriptive than
"infantile idiopathic scoliosis," given the natural history of the
deformity and the growth rate in this age group. There are many etiologies for
scoliosis in this particular population, including congenital, neuromuscular,
and idiopathic, as well as various syndromes. The term "infantile"
assumes the common idiopathic etiology as seen with adolescent idiopathic
scoliosis5.
Regardless of etiology, the age of onset remains an important factor for
treatment because curves that demonstrate a major thoracic deformity before a
child is five years of age are more likely to be associated with pulmonary
complications in addition to other growth
abnormalities6-9.
In this article, the term "early onset scoliosis" is used to
include infantile idiopathic scoliosis as well as the other etiologies for
scoliosis diagnosed when a child is five years of age or younger.
The management of children with progressive early onset scoliosis has
proven to be difficult. Standard modalities, such as orthoses or spinal
fusion, that are utilized in older patients may be less effective in very
young children because they may adversely affect the growth and function of
the immature spine, lungs, and thoracic cage.
Infantile idiopathic scoliosis, one of the many causes of scoliosis in this
age group (three years of age or less), comprises less than 1% of all cases of
idiopathic scoliosis in the United
States10. The
disorder is rare and is more common in boys than girls (ratio,
3:2)10. The
majority of the curves (75% to 90%) tend to be left-sided rather than
right-sided. Infantile idiopathic scoliosis may be associated with congenital
anomalies such as hip dysplasia, congenital heart disease, and mental
retardation, and it was initially reported to be more prevalent in the United
Kingdom than in North America.
Wynne-Davies11
carried out a family survey of early onset scoliosis in Edinburgh. She found
that there was a genetic tendency toward the development of scoliosis, but she
also found that a genetic tendency by itself was insufficient and that other
factors were necessary to "trigger off" the deformity. McMaster
described the relative prevalence of early onset scoliosis seen in Edinburgh
in 1983 as comparable with the reported prevalence in Boston in 1973, an area
in which the genetic pool is
similar12. From the
results of this st udy it would appear that although the genetic tendency
toward the development of early onset scoliosis remains constant, the
triggering factors are either being removed or, alternatively, some beneficial
factor previously present in the environment of North America is now being
applied in
Edinburgh5.
Fortunately, the prognosis associated with early onset scoliosis differs
from that associated with late onset scoliosis. In a study by Lloyd-Roberts
and Pilcher, more than 90% of cases of infantile idiopathic scoliosis resolved
spontaneously without the need for
treatment13. It is
important to be aware that girls in this age group who present with
right-sided thoracic curves may have a worse prognosis and may not follow the
typical rate of spontaneous
resolution14.
Infantile idiopathic scoliosis was initially attributed to intrauterine
molding. Browne hypothesized that intrauterine molding not only caused
infantile scoliosis but was also responsible for associated crowding
deformities. In his series, 83% of patients exhibited some form of
intrauterine crowding deformity such as plagiocephaly, decreased hip
abduction, or rib
molding15,16.
Mehta subsequently recognized intrauterine molding as an etiologic factor for
infantile idiopathic
scoliosis17.
However, the view has subsequently been refuted due to the absence of
scoliosis at birth.
The second hypothesis to explain infantile idiopathic scoliosis, as
postulated by Mau, was the position in which the infant was positioned for
sleeping18. Mau
believed that prolonged oblique supine positioning in the crib was responsible
for infantile scoliosis. Data from the study by Wynne-Davies also supports the
postnatal pressure theory. She observed that scoliosis and plagiocephaly
developed in ninety-seven of 134 babies within the first six months of life
(the time during which children are unable to reposition
independently)19.
The rate of plagiocephaly in children without scoliosis is
28%20. In addition,
since very few curves were present at birth, she also refuted the claim that
these curves were congenital in nature. Interestingly, infant positioning may
explain the reported difference in the prevalence of infantile idiopathic
scoliosis between the United Kingdom and the United States. Infants in the
United Kingdom have conventionally been placed in a supine sleeping position,
whereas American children tended to be positioned prone. This trend in the
United States has shifted with the current recommendations from the American
Academy of Pediatrics, which advocates supine sleeping to decrease the risk of
sudden infant death
syndrome21.
The genetics of infantile idiopathic scoliosis was similar to that of late
onset scoliosis, in which parents or siblings of affected children are thirty
times more likely than controls to have
scoliosis19. In her
study population, Wynne-Davies found that 13% of male infants with progressive
curves were mentally retarded and 7% also had concomitant inguinal hernias.
The data from the Mehta study concurred with that of Wynne-Davies. Mehta noted
that infants with hypotonia were unable to resist deformation compared with
children with normal
tone17. Conner
reported that children with congenital malformations, including hiatal hernia,
were at increased risk of scoliotic
progression22.
Although several factors, such as age at onset, location, and type and
magnitude of the curve as well as associated anomalies, gender, and family
history, were proposed as predictors of curve progression, the most reliable
indicator has become the rib-vertebra angle difference (RVAD) reported by
Mehta in 1972 (Figs. 1-A, 1-B, and
1-C)23.
However, it is not possible to rely on a single measurement; for accuracy, the
RVAD measurement must be repeated after four months. Resolution of curves of
up to 60° has been
observed5.
Clinical Evaluation
Evaluation begins with a comprehensive history and physical examination.
The clinical evaluation of a child with suspected scoliosis or other spinal
deformity must proceed in a thorough, systematic fashion, and a complete
history must be obtained prior to physical examination. A prenatal history of
the mother, including all health problems, previous pregnancies, and
medications, is recorded. Birth history of the child should include details
such as length of gestation, type of delivery (vaginal or caesarean), birth
weight, and complications.
Given that the presence of cognitive delay has been shown to correlate with
curve progression in some patients, particular attention should be paid to
whether the child has appropriately reached developmental
milestones19,22.
The physical examination attempts to analyze the spinal deformity and
eliminate associated conditions from the potential diagnosis. Initial
inspection should include the skin, the entire spine, the head, the pelvis,
and the extremities. The skin must be examined for cutaneous abnormalities
such as café au lait spots or axillary freckles as seen in
neurofibromatosis, midline patches of hair as seen in spinal dysraphism, or
bruising as seen with trauma.
The spinal examination should include inspection and palpation of the
spine. For children with early onset scoliosis, some aspects of the standard
physical examination are made more difficult due to the age of the patient,
and different techniques must be used. In young children, the Adams forward
bend test (looking for prominence of the ribs in the thoracic spine or
transverse processes in the lumbar spine) is not possible, but the test can be
simulated by laying the child in a prone position over the knee of the
examiner. Curve flexibility can be assessed by placing the child in a lateral
position over the knee of the examiner or by suspending the infant under the
arm of the examiner.
The physical examination must also include notation of chest or flank
asymmetry, chest excursion, and abdominal reflexes. Limitation in chest
excursion may indicate syndromic scoliosis and thoracic insufficiency
syndrome9. Abdominal
reflex abnormalities should initiate a thorough neurologic evaluation. Muhonen
et al. described the absence of an abdominal reflex as the only objective
finding seen in some patients with a Chiari
malformation24.
When the results of reflex testing are abnormal, the reflex is usually absent
on the convex side of the
curve25.
Other studies suggest that, even in the presence of a normal physical
examination, magnetic resonance imaging of the total spine is indicated in
some children with early onset scoliosis, such as those with infantile
idiopathic scoliosis, due to the high incidence of neural axis
abnormalities26. In
the report by Gupta et al. on six patients with infantile idiopathic scoliosis
and normal neurologic examinations, three patients were found to have neural
axis abnormalities on magnetic resonance
imaging27. Dobbs et
al. subsequently reported on forty-six neurologically normal patients with
Cobb angles of >20° who underwent magnetic resonance imaging. Of those
patients, ten demonstrated a neural axis abnormality and eight ultimately
required neurosurgical intervention for the abnormality. The current
recommendation is to perform a magnetic resonance imaging scan on patients who
have infantile scoliosis and a Cobb angle
>20°28.
For patients with infantile idiopathic scoliosis, it is also important to
thoroughly examine the head. Plagiocephaly is common and responds well to
therapy. The recessed side of the head is on the left side in a high
percentage of patients. Other conditions affecting the head that are
associated with infantile idiopathic scoliosis include bat-ear deformity and
congenital muscular torticollis. Although these conditions frequently occur
without scoliosis, it is important to be aware of the association. Examination
of the pelvis should be done to rule out developmental hip dysplasia, which is
associated with infantile idiopathic
scoliosis15,16.
The lower-extremity examination must exclude limb-length inequality as the
cause of scoliosis. When scoliosis is secondary to a limb-length inequality,
the lumbar prominence is found on the side of the longer limb. The diagnosis
of functional scoliosis due to limb-length inequality is confirmed by having
the patient perform a sitting forward bend or by placing a lift under the
short limb to equalize the limb lengths.
Radiographic Evaluation
The initial evaluation of a patient with reported scoliosis should consist
of anteroposterior and lateral radiographs of the entire spine (including the
cervical spine and pelvis). In children who are too young to stand, the
radiographs should be made with the child placed supine. Abnormalities of the
cervical spine should be sought and evaluated. Similarly, the lumbosacral
junction, pelvis, and hips should be carefully examined to rule out congenital
anomalies or developmental hip dysplasia.
Scoliosis measurement is done with use of the Cobb technique, which is also
helpful in monitoring the progression of the
curve29. Unlike the
curves associated with late onset scoliosis, the curves seen in patients with
early onset scoliosis frequently resolve spontaneously. The RVAD method is
available to predict progression or resolution of the curve in infantile
idiopathic scoliosis. In 1972, Mehta described the method that now bears her
name. Frustrated with the inability to predict which curves would progress,
she evaluated the relationship of the rib attachment to the vertebral body.
She noted variability in the takeoff angle of the ribs from the convex versus
the concave side of the curve. The rib-vertebral angle difference of Mehta
(RVAD) measures the angle of a line drawn perpendicular to the apical thoracic
vertebra end plate and a line drawn down the center of the concave and convex
ribs. The actual difference is calculated by subtracting the convex from the
concave angles23
(Figs. 1-A, 1-B, and 1-C). An
RVAD of =20° indicates a curve that is likely to resolve (85% to 90% of
patients), while an RVAD of =21° is frequently associated with a curve
that will progress. Mehta later described an additional tool, known as the
"phase of the rib head," that is useful for prognostication of
infantile scoliosis. The phase of the rib head notes the position of the
convex rib head on the apical vertebra. A "phase-1" relationship
indicates no overlap of the rib head or neck on the apical vertebra. In curves
that have a phase-1 relationship, the RVAD may be calculated and used to
determine the likelihood of progression. In a phase-2 relationship, the head
of the rib on the convex side of the apical vertebra overlaps the vertebra and
the RVAD is not measured because the curve is certain to
progress23. In the
initial description of the RVAD and phase of the rib head, Mehta reported 83%
resolution in phase-1 relationships with an RVAD of =20°. Conversely,
84% of the group that progressed had an RVAD of =21°.
Ferreira and James tested the RVAD and head of the rib phase in their own
patient population and reported results similar to those of Mehta. Curves in
patients with phase-1 ribs and an RVAD of =20° resolved in 99% of
patients, whereas 98% of patients with an RVAD of >20° or a phase-2
relationship
progressed30. One
final radiographic clue to evaluate is the presence of a lumbar curve.
Ceballos et al. demonstrated that double curves are very likely to progress
and must be followed
closely31.
Nonoperative Treatment
The treatment of children with early onset scoliosis is based on
anticipated or actual curve progression. As discussed, Mehta's prognostic
criteria have proven to be very helpful in differentiating between resolving
and progressive curves with infantile idiopathic scoliosis. Curves with a Cobb
angle of =25° and an RVAD of =20° are at low risk for
progression. These patients may be observed and should be reevaluated with
serial radiographs every four to six months. Active treatment should be
initiated if curve progression of =10° occurs. If the curve resolves,
it is prudent to follow the patient at one to two-year intervals, until
maturity, to watch for any possible recurrence during the adolescent growth
spurt. A recent long-term study of resolving curves validated the use of the
RVAD and demonstrated that there was no advantage of plaster-bed treatment
over physiotherapy with regard to either the time to resolution or functional
outcomes32. Curves
with a high likelihood of progression are those with an RVAD of =21° or
a phase-II rib-vertebra relationship and a Cobb angle of between 20° and
35°. These patients should also be followed closely at four to six-month
intervals, and active treatment should be initiated if progression occurs
(Fig. 2).
Traditional nonoperative treatment approaches to early onset scoliosis
include casting and bracing. Treatment usually begins with application of a
molded body cast with the patient under general anesthesia. The cast is
changed at six to twelve-week intervals until maximum correction is achieved.
Following this, the cast may be replaced by a Milwaukee brace with full-time
implementation (twenty-three hours per day). Milwaukee braces have been
preferred over thoracolumbar orthoses due to the distortion of the rib cage
and reduction of pulmonary function that can occur with the circumferentially
fitting thoracolumbar braces. In addition, the immature rib cage often deforms
before appreciable correction is transmitted to the spine. Bracing is
generally continued for a minimum of two years and until there is no further
evidence of progression as indicated by an unchanging Cobb angle and RVAD.
Mehta and Morel have reported that, with total correction prior to the
prepubertal growth spurt, there is no relapse during
adolescence33.
However, without full correction, small relapses may occur. These patients may
require surgery if further progression occurs during the adolescent growth
spurt, and they should be followed until skeletal maturity.
Surgical Treatment
The ultimate goal of surgical treatment for early onset scoliosis is to
stop progression of the curve while allowing maximum growth of the spine,
lungs, and thoracic cage. Surgical treatment of infantile idiopathic scoliosis
is recommended for progressive curves of =45° in an immature
child20. This
statement indicates the current trend toward less tolerance of curve
progression prior to operative management. The age of the patient at the time
of curve progression will frequently dictate the type of surgical procedure
chosen. Initial techniques promoted spinal fusion as the primary method to
halt curve progression. Success was thought to be a straight, shortened spine
rather than a deformed spine of near normal length. Isolated posterior spinal
fusion in young children was quickly found to be unsuccessful for long-term
correction of deformity due to the occurrence of the crankshaft
phenomenon34,35.
The crankshaft phenomenon describes the progression of the curvature due to
continued anterior growth of the spine following a successful posterior spinal
fusion in skeletally immature patients. Sanders et al. reported that patients
who have open triradiate cartilages and are at Risser grade-0 spinal maturity
have a high likelihood of curve progression due to the crankshaft phenomenon
if an isolated posterior fusion is
performed36.
To prevent the crankshaft phenomenon in patients with an open triradiate
cartilage, an anterior arthrodesis must be included with the posterior fusion.
However, anterior and posterior fusion results in considerable loss of both
spinal growth and sitting height. Since there are two stages of maximal spinal
growth velocity (at zero to five years of age and at ten to fifteen years of
age), it can be concluded that early fusion for early onset scoliosis will
result in substantial loss of expected height. Dimeglio developed charts to
predict remaining growth in a growing
child2. Similarly,
Winter described a formula for calculating the amount the spine will be
shortened as a result of premature spinal
fusion37. To
calculate projected shortening in centimeters, one can multiply 0.07 ×
the number of segments fused × the number of years remaining for growth.
These valuable tools allow the physician and family to understand the
ramifications of spinal fusion in the very young child. In addition to the
detrimental effects on spinal growth, premature fusion has potentially
deleterious repercussions for the developing thoracic cage and lungs. This has
prompted attempts to devise other methods for the treatment of early onset
scoliosis, and current research has focused on fusionless methods for the
treatment of early onset scoliosis.
The surgical treatment of early onset scoliosis has evolved throughout
several generations (and has been continually adapted to fit the prevailing
understanding of scoliosis). More than forty years ago, Roaf proposed that the
deformity seen in early onset scoliosis was due to asymmetric growth of the
convex (faster-growing) and concave (inhibited) sides of the
curve38. Due to the
successful use of hemiepiphysiodesis in the treatment of angular growth
deformities in the extremities of growing children, he recommended a similar
approach to the spine. The technique he described involved ablation of the
convex epiphyseal cartilage and adjacent discs at the vertebrae near the apex
of the curve. Although 23% of the patients showed improvement in the Cobb
angle of the curve, 40% were seen as demonstrating little or no improvement in
Cobb angle (<10° change). More recently, Marks et al. reported on
convex epiphysiodesis with or without Harrington instrumentation and found no
significant improvement in the measured
deformity39. They
recommended instrumentation at the time of convex epiphysiodesis as the best
option to control, but not reverse, the progression of the curve.
The concept of convex growth retardation in the treatment of idiopathic
scoliosis continues to have supporters. The latest attempts to control
curvature with hemiepiphysiodesis have focused on a minimally invasive
approach through the use of thoracoscopic techniques. Staples similar to those
used in treating angular deformity of the lower extremities are placed on the
convex side of the vertebrae at the apex of the curve. The technique avoids
fusion and thereby preserves the potential for future growth. Betz et al.
reported on the use of staples placed thoracoscopically for convex
epiphysiodesis in patients with adolescent idiopathic
scoliosis40. In
that study, 60% of the curves remained stable (<6° progression) at a
minimum duration of one year of follow-up. The authors recommended caution in
interpreting the results and have not attempted to perform the procedure on
any younger patients, such as those with early onset scoliosis.
Vertical expandable prosthetic titanium rib (VEPTR) implantation is another
nonfusion technique that is aimed at correcting the thoracic deformity and
improving lung function. It is used more often for patients with thoracic
insufficiency syndrome and fused
ribs41. No
published data are available with regard to the use of this procedure in
children who have early onset scoliosis but no congenital anomalies of the
spine.
Posterior Instrumentation without Fusion (Growing-Rod
Instrumentation)
The goal of posterior instrumentation without fusion is the preservation of
spinal growth in concert with correction of the deformity. Ironically, this
technique was initially reported in 1962 by Harrington for the treatment of
scoliosis42. He
described a fusionless approach involving a distraction rod attached to
laminar hooks placed at each end of the concave side of the deformity.
Complications included implant failures such as hook dislodgment and rod
breakage; however, no long-term follow-up results were reported. Harrington
proposed that "progressive scoliosis in a child less than ten years old
can be managed with the apparatus alone without fusion, whereas in a child
more than ten years old fusion should usually be done at the time of the
initial
correction."42
Subsequently, his technique for instrumented spinal fusion altered the course
of modern scoliosis surgery.
Using the work of Harrington as a foundation, Moe et al. modified the
surgical technique by limiting subperiosteal dissection to the location of
hook placement43.
No formal fusion was performed at the site of hook placement, and the rod was
tunneled in a subcutaneous rather than a submuscular manner. The rod itself
was also modified to include a smooth section at the middle portion to ease
insertion, avoid scar formation, and allow sagittal contouring. Moe et al.
used a Milwaukee brace for postoperative immobilization. Lengthening of the
construct was performed at intervals of six to twelve months or when the loss
of correction was =10°. The final results of this technique
demonstrated an average additional growth of 2.9 cm in the region that
received instrumentation among all patients. Of the patients ultimately
managed with fusion, growth averaged 3.8 cm compared with the predicted 4.5 cm
for those same patients. Moe et al. reported a 50% complication rate, with
hook dislodgment occurring from both the rod and lamina. The modified thicker
rod resulted in slightly less rod breakage.
Klemme et al. reported on their twenty-year experience in managing
sixty-seven patients with
scoliosis44. The
patients had an average of 6.1 procedures from the time of initiation of
treatment to the time of definitive fusion. The method was considered
successful because 66% of the patients demonstrated either no progression or
an average of 30% improvement in curve magnitude. In the remaining patients,
twelve of whom had neuromuscular scoliosis, the curve progression averaged
33%. The overall spinal growth of the patients who were managed with this
method was comparable with normal growth. Complications due to implant failure
were reported in 8% of the total procedures performed.
In 1977, Luque and Cardosa described segmental spinal fixation without
fusion45. Luque
reported on the use of sublaminar wires in combination with Harrington rods in
forty-seven patients with neuromuscular
scoliosis46. He
reported that use of this technique resulted in an average growth of 2.6 cm in
the instrumented portion of the spine, with a 78% curve correction. The
technique was later modified to include smooth "L" shaped rods and
wires known as a "Luque trolley." Proponents of this technique
suggested that operative lengthening would be unnecessary because the rods
would slide through the wires and allow growth of the
spine47. The
strength of the construct also obviated the need for postoperative
immobilization. However, the Luque trolley was not without complications. Rod
breakage continued to occur, and patients required lengthening procedures. It
was difficult to achieve sublaminar passage of wires without subperiosteal
exposure, and the technique was noted to result in spontaneous fusion in young
patients48. Several
authors also noted that growth was minimal in the portion of the spine that
had undergone
instrumentation48,49.
Modifications of the Luque trolley have been described. Patterson et al.
combined the Luque trolley with anterior growth arrest of the convexity of the
curve in young
patients50. Curve
correction averaged 46% after two years of follow-up. The results were better
in patients who underwent segmental instrumentation and anterior fusion than
they were in those with posterior segmental instrumentation alone. No
spontaneous fusions were reported in their series. A similar study was
performed by Pratt et
al.51. The study
agreed with the findings of Patterson et al. regarding the poor prognosis for
patients managed solely with posterior segmental spinal instrumentation. The
Cobb angle worsened in 54% of the patients, remained stable in 31%, and
improved in only 15%. Despite these disappointing results, the authors still
believed that this treatment was superior to bracing for the treatment of
early onset scoliosis but that modification of the technique and implants was
required for improved success.
At the same time that Luque reported on his technique, Marchetti and
Faldini described the "end-fusion technique" for treating early
onset scoliosis in young
children52. The
technique described staged operative procedures, the initial procedure of
which was fusion of the vertebrae at the ends of the Cobb angle. Several
months later, hook and subperiosteal rod placement was performed. The third
procedure, typically performed six to eight weeks after placement of the hooks
and rod, involved distraction of the upper hook. Unfortunately, the report
contained only limited follow-up.
Other reports have focused on lengthening through submuscular rod
placement. Blakemore et al. described the use of an Isola single submuscular
rod with and without apical fusion in a heterogeneous population of
twenty-nine patients with scoliosis or
kyphoscoliosis53.
Only ten patients were considered to have scoliosis that was idiopathic in
nature. Unlike the procedures described in previous reports, the rod was
placed submuscularly. Curves that were =70° or that were seen to be
stiff on bending radiographs were treated with an apical fusion in addition to
placement of the submuscular rod system. The initial postoperative curve
measurements had a mean angle of 38°, which was a significant improvement
from the mean preoperative measurement of 66° (p = 0.05). Complications
included hook displacement, rod breakage, and superficial wound infection,
which occurred in 24% of the patients. Spinal growth was not reported. Despite
the complications, the authors believed that the technique was useful in the
treatment of major spinal deformity in young children.
Dual Growing Rod
Several studies regarding the growing-rod technique have recently been
reported54,55.
The recent treatment efforts continue to promote spinal growth while
maintaining deformity correction and minimizing complications. With use of the
basic principles of Isola instrumentation described by
Asher56 and the
dual rods described by
McCarthy57,
Akbarnia and Marks have developed and currently use a dual growing-rod
technique that can be used submuscularly or subcutaneously
(Fig.
3)58.
Subperiosteal dissection is performed only at the upper and lower anchor
sites of the construct. At the upper end, hooks or screws are placed in a claw
pattern spanning two or three levels to allow for maximum stability in a young
child. A similar pedicle screw or hook pattern is used at the lower end of the
implants. These sites are called the "foundations" of the
construct. A transverse connector is preloaded or added at the level of each
foundation, especially when hooks alone are used. In a recent biomechanical
study, Bagheri demonstrated that transverse connectors add significant
stability (p < 0.002) to the construct if pedicle screws are not
used59. Limited
fusions are performed at the site of the foundations with the use of local
bone or synthetic graft. Each rod is then measured and cut into an upper and
lower portion. Contoured rods are placed on each side of the spine, and the
upper and lower rods are linked by way of a tandem connector placed at the
thoracolumbar junction (Figs. 4-A through
4-I). Bracing is used until a solid fusion is achieved, which
usually happens in six months.
Following the initial placement of the construct, lengthenings are
performed at six-month intervals. Lengthening of the construct is performed
with use of a distractor designed to fit inside the connector. Somatosensory
evoked potential monitoring is used during each lengthening procedure to
monitor the response of the spinal cord to the correction. Patients who have
shorter intervals (six months or less) between lengthening procedures have
better correction of the scoliosis and greater spinal growth than patients who
have longer intervals (more than six months) between lengthening
procedures60.
Akbarnia et al. reported on the initial, minimum two-year follow-up data
from the Growing Spine Study
Group54. Age at the
time of initial surgery averaged 5.4 years, and patients had an average of 6.6
lengthenings over the course of the treatment period. The Cobb angle averaged
82° preoperatively, 38° at the time of the initial postoperative
visit, and 36° at the time of the most recent follow-up or after the final
fusion. Growth of the spine approached that associated with normal spinal
growth, with an average of 1.21 cm per year. Seven patients who were followed
to the time of final fusion had an average of 11.8 cm of total spinal growth
during the time of treatment. Eleven of the twenty-three patients had a total
of thirteen complications during the "treatment period."
In a recent study by the Growing Spine Study Group, the complications of
dual growing-rod technique were reported in a larger
group61.
Forty-eight patients with early onset scoliosis were treated with the dual
growing-rod technique and were followed for a minimum of two years. Fifty-five
complications developed in twenty-nine patients, and twenty-three of those
patients required unplanned procedures. Complications were divided into four
categories: implant, wound, alignment, and general. Wound problems were the
most common cause of unplanned procedures and required early and more
aggressive treatment. Most implant problems were addressed during planned
procedures.
Patients who were younger at the time of the initial surgery had higher
complication rates. More complications occurred with longer treatment periods.
A high correlation existed between the diagnosis of infantile idiopathic
scoliosis and implant-related problems. Patients whose lengthening intervals
were seven or fewer months apart had fewer implant complications but more
wound complications. Patients whose intervals were seven or more months apart
had more implant complications but fewer wound complications. It was concluded
that the technique has a high but manageable complication rate.
The study by Thompson et al. again supports the use of dual-rod
instrumentation55.
Twenty-eight patients were divided into three groups and were followed to the
time of final fusion: single rod with anterior and posterior apical fusion
(five patients), single rod without apical fusion (sixteen patients), and dual
rod without apical fusion (seven patients). Although the authors determined
that either the single or the dual-rod technique was effective at achieving
curve correction and allowing spinal growth, the dual-rod system not only
improved the curves but maintained initial correction better and facilitated
increased spinal growth. In the series, short apical fusion was associated
with curve stiffening, the crankshaft phenomenon, and a higher prevalence of
complications. As a result, the authors questioned the effect of combining
apical fusion with either of the growing-rod techniques in treating patients
with early onset scoliosis.
When Should Growing-Rod Techniques Not Be Considered?
The following recommendations are made on the basis of initial experience
and short-term follow-up and not all are evidence based. Unfortunately, no
long-term outcomes are available at this time for the various surgical
procedures on very young children. Prospective studies are under way to find
answers for the many questions that currently exist.
Since the goal is correction and/or maintenance of the deformity while also
allowing spinal growth, the growing-rod technique should be avoided if these
goals cannot be achieved. This is true in children with very stiff curves,
older children with minimal remaining growth, and those in whom correction
cannot be achieved either because the patients are too young for the use of
instrumentation or because they have very soft bone. Although there may be
ways to achieve flexibility and to enhance the bone quality, the procedures
may be complex and require an expert surgeon with appreciable experience.
Some patients with deformities, such as congenital anomalies of the spine,
may not necessarily have appreciable remaining growth potential; however, the
growing-rod technique, in selected cases, may prevent worsening of the
deformity as well as provide ongoing internal support. Patients who have
severe congenital curves with fused ribs and thoracic insufficiency syndrome
may be candidates for other treatment methods, such as VEPTR.
Finally, for this procedure to be successful, the family should be
counseled with regard to the length of the treatment period, all possible
complications, and the need for their complete cooperation.
The treatment of early onset scoliosis remains one of the more challenging
aspects of pediatric orthopaedic surgery. Historical data have demonstrated
that untreated curves have the potential for causing serious cardiopulmonary
and skeletal
complications1,62.
Observation, casting, orthotics, traction, and operative treatment remain the
options for the treatment of early onset scoliosis. Operative treatment should
be reserved for patients who do not meet the criteria for observation or
orthotic management or for whom orthotic management has failed.
While current fusionless operative techniques are an attempt to allow
continuing spinal growth and to prevent curve progression, the patient
requires numerous operations prior to the definitive spinal fusion. Reducing
the frequency of reoperation or removing the need for it altogether without
sacrificing the growth or correction achieved by the fusionless techniques
should be one of the primary goals in the development of new treatment
methods. The question needs to be asked if it is reasonable to start the
treatment earlier, when the curves are less severe and maintenance of
correction is easier, to see if better correction is achieved and maintained
over an extended period until skeletal maturity. It may be possible to remove
the implants at maturity without the need for definitive fusion. Future
research and longer follow-ups will attempt to answer these questions.
We should find solutions that are less invasive and require fewer operative
procedures but that still allow normal spinal growth and correction of the
deformity. For the time being, the dual growing-rod technique allows the
surgeon to offer minimal restriction to the normal growth of the spine and to
maintain spinal and chest-wall deformity correction in patients with
progressive early onset scoliosis. ?
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