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David
H. Clements, M.D.
Rohinton K. Balsara, M.D
Introduction
Thoracoscopic
anterior release and fusion is an advanced surgical technique
for correction of adolescent idiopathic scoliosis (AIS).
In this procedure, the thoracic spine is accessed through
small incisions on the side of the chest and the surgery
performed with the aid of a thoracoscope (an illuminated
optical instrument). The surgical procedure involves a discectomy
(removal of one or more discs). The abnormal curvature is
'released' and the spine realigned and held in place using
instrumentation and fusion. The advantages to this procedure
include fewer levels in the fusion, resulting in a more
flexible spine; decreased pain after surgery; less scarring;
and curve correction comparable to that of an open procedure.
Safety
and Effectiveness Proven
Since
1991, we have been prospectively evaluating (following patients
forward in time) the safety and efficacy of anterior thoracic
instrumentation inserted through an open incision, and we
have been inserting the instrumentation with the thoracoscope
since 1996. The procedure with both insertion techniques
has been shown to be safe and effective, with results comparable
to those of posterior spinal fusion. In selective anterior
fusion, fewer vertebrae are fused. Thus the scoliosis can
be corrected while leaving the spine flexible and relatively
well aligned.
Surgical
Considerations
The
primary indication for thoracoscopic anterior instrumentation
and fusion is a thoracic curve measuring between 40 and
70° by the Cobb method (a full-length AP x-ray is to used
calculate the curve angle in degrees). Patients between
10 and 21 years of age are good candidates because the vertebrae
are usually fully formed and the spine flexible. Since the
anterior instrumentation adds kyphosis, patients must have
kyphosis measuring less than 40° (and less than 20° is ideal,
because the kyphosis will then fall into the normal range
following surgery).
Anesthesia
Requirements
The
patient must be able to tolerate one-lung anesthesia, in
which one lung must be completely collapsed for the entire
procedure to allow space for the thoracoscope and other
instruments. Preoperative pulmonary function (lung capacity)
tests are necessary. The anesthesiologist must be experienced
in utilizing one-lung ventilation techniques in order for
the procedure to succeed.
Study
Results
For
the first 30 patients (28 female, 2 male) who have undergone
the thoracoscopic procedure for AIS:
| |
Average |
Range |
| Age at surgery (years) |
14.7 |
8 to 12 |
| Number of vertebral levels fused |
8 |
6 to 9 |
| Preoperative thoracic curve (degrees) |
47.6° |
40 to 58° |
| Postoperative coronal thoracic curve (degrees) |
15.4° |
5 to 44°(60% correction)
|
| Preoperative kyphosis (T5 to T12) (degrees) |
22° |
6 to 38° |
| Postoperative kyphosis (degrees) |
22.5° |
3 to 63° |
Complications
Two
patients developed a peroneal palsy (paralysis) of the underneath
leg, which resolved by six weeks following surgery. This
problem was resolved by changing the leg position in the
operating room. Three patients developed a pleural effusion
(fluid accumulation in the membrane encasing the lungs),
which resolved without needing to insert a chest tube. In
three patients a rod broke following surgery, one of which
was surgically repaired and the other two are being watched.
Improvements in the bone grafting technique to obtain fusion
have decreased this problem.
Conclusion
If
left untreated, thoracic AIS of 40º or greater may progress
after the spine has finished growing. However, adolescent
patients are usually concerned with the more immediate problem
of trunk deformity. A procedure, which can correct and fuse
AIS in a minimally invasive fashion is extremely attractive
to patients, families and surgeons. The benefits of the
procedure (most notably improved appearance of the thoracic
deformity and a mobile lumbar spine as the patients get
older) are immeasurable.
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