|
|
Adolescent
Idiopathic Scoliosis
|
 |
Figure
1: Cobb Method. All vertebra within the curve
are included and the ends marked with lines.
The angle of the intersection of these lines
is defined as the Cobb Angle. This curve measures
35° |
|
Scoliosis
is defined as curvature of the spine in the coronal (front
view) plane. Idiopathic scoliosis should be conceptualized
as a three dimensional deformity though; twisting of
the spine is coupled with curvature producing deformity
in both coronal and sagittal (side view) planes. As its
name implies, adolescent idiopathic scoliosis occurs
between the ages of 10 and 18 and to date, has no known
cause. The magnitude of the curve is determined using
the Cobb method (figure 1) and conveyed in degrees. Curves
measuring more than 10° occur with an approximate
worldwide incidence of 0.3% and are distributed equally
between males and females. Curves greater than 20° occur
with an incidence of 0.3% and have a distribution of
five females to every male. Because large degree curves
are more likely to require treatment and occur more frequently
among females, there is a common misconception that adolescent
idiopathic scoliosis, in general, is more common in girls.
The exact etiology of idiopathic scoliosis is yet to
be determined, but it is thought to be due to multiple
factors. Although the exact genetics is unclear, the
observation that idiopathic scoliosis is more common
within families suggests the presence of an inherited
trait. Research focusing on changes in muscles, the spinal
column, rib cage and the chemistry of cartilage in discs
suggests that these abnormalities are most likely secondary
to the primary scoliosis and not a causative factor.
The fact that most curves occur in common patterns, such
as right thoracic or left lumbar, raises the possibility
that other anatomical asymmetries such as the pulsatile
beating of a left sided heart, might have an influence
on curve production and progression. We are currently
investigating with MRI the relationship between observed
turbulent CSF (fluid surrounding the spinal cord) flow
at the curve of the apex, differential pressure on the
spinal cord, and the influence of these factors on curve
progression. For the
reader who is interested in more information on the current
state of knowledge and research into the etiology of
idiopathic scoliosis, a recent Current Concepts Review
(Journal of Bone and Surgery, Volume 82A, No. 8, August
2000) will be helpful.
|
Adolescent
idiopathic scoliosis curves are classified by their location
in the spine. Curves can occur in the cervical, thoracic,
and lumbar spine in various combinations (figure 2).
|
|
|
|
Figure
2a: Thoracic |
Figure
2b: Double
Major |
Figure
2c: Thoracolumber |
|
Structural curves are defined as those curves that
incompletely straighten on side-bending. Compensatory
curves straighten significantly on side bending and function
to produce spinal balance. The location of the structural
curve determines the classification of the scoliosis.
For example, a structural curve occurring in the thoracic
spine with a lumbar compensatory curve is called thoracic
adolescent idiopathic scoliosis (figure 3)
|
|
|
|
Figure
3a: Right thoracic adolescent idiopathic scoliosis. |
Figure
3b: Left
side bending - notice the lumber curve straighten
and therefore is compensatory. |
Figure
3c: Right
side bending - the thoracic curve incompletely
straightens and therefore is structural. |
|
Single curves, curves whose apex is at T12 or L1 are
defined as a thoraculumbar curve (figure 4), and curves
with apices at L2 or L3 are defined as lumbar curves.
Structural curves in both the thoracic and lumbar spine
are called double major curves. (figure 5) The exact
definition of the curve has implications for determining
progression and treatment.
|
|
|
Figure
4a: Apex of curve at T12. This curve
is defined as Thoracolumar Adolescent Idiopathic
Scoliosis. |
Figure
5: Two large structured curves are classified as
a Double Major Curve. |
|
 In
California , as in many other states, law mandates middle
school screening for scoliosis. Scoliosis is detected
by observation of a rib prominence during a forward bending
test. Girls and boys are most often screened in the
7th and 8th grades, respectively. School screening has
effectively reduced both the number of patients requiring
surgery and the magnitude of those curves at the time
of surgery. |
Based on these conditions,
this table (figure 7) summarizes current treatment of
adolescent idiopathic scoliosis. Small curves measuring
less than 20-25° that do not require brace treatment
should be observed during periodic examinations of four
to six months or 1 year intervals based on their size.
Observation remains a form of treatment because any 5° increase
in the size of the curve may change the course of treatment. |
Adolescent Idiopathic Scoliosis
Treatment Skeletally Immature Adolescent |
| Curve (degrees) |
Treatment |
| <20° |
Observation |
| >20° < 25° |
4 month X-rays |
| 25°-30° with a 5° documented progression |
Brace |
| 30°-40° |
Brace |
| >40° |
Consider surgery |
|
Those patients who have curves
greater than 40° at presentation and have progressive
curves despite bracing should be considered for surgery.
Curves between 40 and 50° fall into a relative gray
area for surgical indications, but any curve above 50° in
a growing child should be surgically stabilized.
The basic principle of surgery is to stop progression
of the curve and leave the patient balanced in a frontal
and sagittal plane. Cessation of curve progression is
achieved with bony fusion between the affected vertebrae
while correction is held and supported by spinal instrumentation
until healing is complete. All structural curves need
to be fused. Depending on the type of instrumentation,
a brace may or may not be necessary subsequent to surgery.
Although much attention has been focused on the various
approaches to stabilizing curves in adolescent idiopathic
scoliosis, certain principles are applicable to all of
them. A minimum number of vertebrae should be fused to
achieve a balanced spine. Secondly, the extent of the
fusion into the lumber spine may negatively impact the
future occurrence of low back pain in the patient and,
therefore, the fusion should attempt to preserve as many
free lumbar segments as possible.
|
 |
|
| Figure
8: Pre-op thoracolumber curve treated with anterior
spinal instrumentation. Distal lumber motion segments
are preserved with this technique. |
|
In general, either anterior or posterior
spinal fusions are employed, based on surgeon preference
and curve location. Only in very large curves is it necessary
to operate on both sides of the spine. Some approaches
clearly make more sense than others. For example, in this
author's opinion a thoracolumbar curve fused through the
front generally has a greater chance of preserving distal
lumbar fusion levels than a similarly efficacious posterior
fusion. (figure 8)
Spinal instrumentation has revolutionized the surgical
treatment of progressive curves in adolescent idiopathic
scoliosis. Instrumentation serves to correct the curve
while holding it stable until bone applied to the spine
heals (the fusion). Once the bony fusion occurs, the
instrumentation has no function, although it rarely needs
to be removed. In the past, Harrington rods provided
two points of fixation in the spine and therefore needed
to be supplemented with a cast to hold the spine. Contemporary
instrumentation techniques utilize segmental fixation
which provides attachment to the spine at multiple points.
Unlike the Harrington rod, segmental fixation techniques
allow better correction of the curve in both the frontal
and sagittal planes (figure 9) (See Sagittal Balance
of the Spine and Flat Back Deformity article by Robert
S. Pashman, M.D. in Backtalk, June/July 1996.)
|
|
| New instrumentation techniques
have, in many instances, proven to be so rigid that postoperative
bracing is sometimes not necessary (Figure 10). The type
of instrumentation, approach, and the use of post operative
braces are based on the surgeon’s experience. |
 |
 |
 |
| Figure
10: Pre-op and post-op segmental spinal
instrumentation. Frontal and sagittal plane contours
have been controlled. |
|
One exciting, potential advance
in the surgical treatment of adolescent idiopathic scoliosis
is the use of less invasive techniques, utilizing multiple
small incisions for the placement of cameras to view
and instruments to correct the scoliosis from the front
of the thoracic or thoracolumbar spine. Currently, multi-center
studies are under way to establish the safety and efficacy
of this type of approach.
|
Related links:
Scoliosis overview
Adolescent Idiopathic
Surgical Cases performed by Dr. Pashman
Patient
journal of scoliosissurgery, Patient
follow-up journal four years after surgery
Scoliosis Bracing
Scoliosis FAQ's
Scoliosis Books
|
|
