Options of Thoracic Idiopathic Scoliosis Fixation and Fusion
For many years, the gold standard for fixation for a thoracic curve in idiopathic scoliosis was a single Harrington rod applied through a posterior approach, with a distraction rod on the left side. See Figures 1A & B. This yielded a "good result" in most cases. Posterior approach refers to exposing the laminae and posterior elements (Figures 2 and 3). Anterior approach refers to exposure of the vertebral bodies (Figures 4A & B and 5).
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applied through a posterior approach |
applied through a posterior approach |
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Figure 5, Anterior Approach |
EVOLUTION
However, advances have been made centered on trying to obtain more correction
and to get patients back to their previous activities more quickly with less reliance
on bed rest, cast or brace.
A next step in the evolution was that of using two rods for a thoracic curve and
achieving segmental fixation (fixation at each level) with either Wisconsin wires
or sublaminar wires. A distraction rod was used on the left side and a neutralizing
Luque rod on the right side. See Figures 6AD.
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Figure 6C, 2 Harrington Rods |
Figure 6D, Sublaminar Wires |
The next evolutionary stage then was that of CD (CotrelDubousset) instrumentation
using multiple hooks with both rods in an effort to get even stronger fixation
and to "derotate" the spine somewhat and also to reduce and correct
the lordosis that often goes along with right thoracic curves. See Figures 7AD.
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Figure 7C, CD Instrumentation |
Figure 7D, Multiple Hooks |
Step 3 has now evolved into a concept of anchors at the top and the bottom
of the curve with wires in between, either Wisconsin wires or sublaminar wires.
In most cases, the distal anchors described are hooks or pedicle screws, and the
proximal fixation points are hooks which are left loose until the final fixation.
See Figures 8AD for xrays, Figures 8E & F for clinical result in the
patient.
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Figure 8A,Preoperative |
Figure 8B, Side View |
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Figure 8C, Wisconsin Wires |
Figure 8D, Side View |
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Figure 8E, Preoperative | |||
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Figure 8F, Postoperative | |||
Step 4 of the evolutionary phase for posterior treatment has been that of using
pedicle screws more liberally throughout the thoracic and upper lumbar spine in
order to achieve more fixation, to reduce the number of levels being fused and
to reduce the number of junctional problems. Junctional problems refer to breakdown
or kyphosis that develops in segments above or below the instrumented vertebrae.
See Figures 9AD.
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Anterior instrumentation has been popular for thoracolumbar and lumbar curves
for several years. See Figure 10.
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Recently, anterior instrumentation for a thoracic curve has become popular.
The advantages of the anterior procedure are the following:
(1) Saving one or two levels distally;
(2) Another alternative to correct the lordotic component of the thoracic curve;
(3) Some suggestion of slightly better correction and slightly better derotation.
See Table 1.
Table 1. ANTERIOR APPROACH |
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Cons | Pros |
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The anterior technique has evolved from use of the threaded rod, to use of the solid rod, to potentially the use of two solid rods anteriorly in certain patients. See Figures 11AD. The potential advantages of the anterior approach are:
(1) A different scar;
(2) Preservation of the posterior spinal extensor muscles. See Table 2.
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Figure 11C, Vertebral Body Screws |
Figure 11D, Side View |
Table 2. POSTERIOR APPROACH |
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Cons | Pros |
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The anterior approach is still invasive, though, and does involve cutting through
and then sewing up shoulder muscles such as the serratus anterior and the latissimus
dorsi. The anterior approach has evolved further now into doing it with an endoscopic/videoassisted
thoracoscopic technique. See Table 3.
Table 3. THORACOSCOPIC APPROACH |
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Cons | Pros |
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Rather than a single incision, three to five "stab" incisions and
otherwise the same surgery with a screw at each level and a single rod.
Further, many surgeons and patients decide to have either an internal or external
thoracoplasty done at the time of the correction to reduce the size of the rib
hump. We do know that anterior surgeries done with an open thoracotomy and also
thoracoplasty techniques do diminish pulmonary functions which then take about
two years to recover.
In the modern day, virtually no spine surgeons in North America use Harrington
distraction. Surgeons use either open or endoscopic anterior approaches or posterior
approaches with bilateral rods, hooks, wires and/or pedicle screws. Patients usually
stand and walk the day after surgery and do not wear casts or braces.
At present there is no strong data to suggest that one technique is superior to
the others. Each technique has the potential to work quite well for the patient
as it does in most cases, but each of the techniques has limitations.
An incidence of pseudarthrosis (fusion not healing) still does exist with all
techniques. With any posterior technique, there is a potential for implant prominence.
With any anterior technique, there is a potential for reduced pulmonary function.
Most surgeons do not brace the patient postoperatively except after the anterior
endoscopic techniques. In five to ten years, it may become clearer that one technique
is superior to the others. It is also quite possible in five to ten years that
we will not decide that the various posterior and anterior techniques are all
very equivalent.
Still the goal is to achieve a solid and stable fusion with the top and the bottom
of the fusion in acceptable sagittal alignment and parallel to the shoulders and
the pelvis.