Thoracoscopic Anterior Instrumentation For Scoliosis
David H. Clements, M.D.
Rohinton K. Balsara, M.D.
Introduction
Posterior spinal fusion (PSF) with spinal instrumentation has
been the mainstay of surgical treatment since the late 1960s.
In 1991, we began a prospective study to evaluate the safety
and efficacy of a selective anterior thoracic fusion using thoracic
segmental instrumentation performed through an open thoracotomy.
Our study indicated that the procedure was safe, with coronal
and sagittal correction comparable to posterior instrumentation
and fusion [1]. In addition, due to the selective fusion, fewer
vertebrae in the lumbar spine required incorporation into the
fusion (average levels saved equals 2.5) compared to PSF. Thus
the scoliosis could be corrected and fused while leaving the
lower back flexible and relatively well aligned.
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Fig. 1B The sagittal profile shows 18 degree of kyphosis from T5 to T12. |
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Thoracoscopic anterior release and fusion is a technique for
obtaining additional flexibility of the thoracic spine as an
aid in correction of the spinal deformity [2,3,4,5]. Instead
of a long open thoracotomy to obtain exposure of the anterior
spine, small incisions are made to allow introduction of a thoracoscope
and working instruments. The advantages are less postoperative
pain in the chest wall, better longterm cosmesis, and equal
release when compared to open discectomy [5].
Combining a selective anterior thoracic instrumentation and fusion
with a thoracoscopic approach creates a novel treatment for thoracic
adolescent idiopathic scoliosis.
Indications
Our inclusion criteria for patients who are candidates for this
procedure were developed from our experience utilizing anterior
thoracic instrumentation.
A thoracic idiopathic curve (Lenke, et al. Type 1 [6]), which
measures between 40 and 70º by the Cobb method is the primary
indication. The age group of patients with adolescent idiopathic
scoliosis between 10 and 21 years of age ensures that the vertebrae
will be fully formed and that the spine should be flexible. The
lumbar curve should be flexible enough on the bending films to
correct to less than 25º. There should be minimal clinical
lumbar asymmetry in the prone position on the exam table.
Thoracic kyphosis should be measured from T5 to T12. Due to the
kyphosing nature of the anterior instrumentation, 40º or
less of kyphosis should be present preoperatively so as not to
cause hyperkyphosis. A patient who is hypokyphotic (less than
20º) would be an ideal candidate for this procedure, as
their kyphosis will fall into the normal range postoperatively.
Junctional kyphosis at the thoracolumbar area is not a contraindication.
The ability of the patient to tolerate one lung anesthesia is
crucial. The lung in the chest cavity entered by the thoracoscope
must be kept completely collapsed for the entire procedure, which
may last 6 to 8 hours. Preoperative assessment by pulmonary function
tests and by an anesthesiologist is necessary for the procedure
to succeed. Prior surgical procedures in the chest cavity to
be entered, or a history of pleural adhesions or scarring, are
a contraindication to the procedure due to the subsequent inability
to completely collapse the lung. An anesthesiologist experienced
in utilizing one lung ventilation techniques is also required
for the success of the procedure.
Results
Since December 1996 we have prospectively studied 30 patients
who have undergone thoracoscopic anterior fusion and instrumentation
for adolescent idiopathic scoliosis. We have performed the procedure
on two males and 28 females. The age at the time of surgery was
a mean of 14.7 years, with a range of 12 to 18 years. The number
of vertebral levels fused was a mean of 8 (range, 6 to 9). The
preoperative thoracic curve averaged 47.6º (range, 40.0
to 58.0º). The first erect postoperative film of the primary
thoracic coronal curve averaged 15.4º (range 5.0 to 44.0º)
(60% correction). Kyphosis measured preoperatively from T5 to
T12 measured an average of 22.0º (range 6 to 38º).
The first erect kyphosis measurement averaged 22.5º (range
3 to 63º).
Neurologic complications consisted of two peroneal palsies in
the down leg, which resolved by three months. These were not
present at the end of the procedure but developed over the subsequent
24 hours postoperatively. Somatosensory evoked potential monitoring
and wakeup tests were both normal in these patients. A
change in leg position has obviated any further neurologic complications.
Three patients developed a postoperative pleural effusion, which
resolved without reinsertion of a chest tube.
Three patients sustained a broken rod postoperatively. One was
revised through a posterior approach with instrumentation, and
the two remaining were painless and are being followed. These
occurred prior to the use of anterior intervertebral body structural
support in addition to the rod, which is now standard procedure.
Conclusion
If untreated, thoracic adolescent idiopathic scoliosis of 40º
or greater may progress after the end of skeletal growth. In
the adolescent patients with idiopathic scoliosis, however, the
concerns are usually with the deformity of the trunk. A procedure,
which can correct and fuse this deformity in a minimally invasive
fashion is extremely attractive to patients, families, and surgeons.
The preponderance of female patients presenting for operative
scoliosis treatment only increases the desirability of a procedure
that effectively corrects the deformity while creating minimally
visible surface scarring. The added benefit of a mobile, minimally
deformed lumbar spine for these patients as they age is also
immeasurable.
References
1. Betz RR, Harms J, Clements DH, Lenke LG , Lowe TG, Shufflebarger
HL, Jeszenszky D, Beele B: Comparison of anterior and posterior
instrumentation for correction of adolescent thoracic idiopathic
scoliosis. Spine 24:225239, 1999.
2. Cunningham BW, Kotani Y, McNulty PS, Cappuccino A, Kanayama
M, Fedder IL , McAfee PC: Videoassisted thoracoscopic surgery
versus open thoracotomy for anterior thoracic spinal fusion.
A comparative radiographic, biomechanical, and histologic analysis
in a sheep model. Spine 23:13331340, 1998.
3. Mack MJ, Regan JJ, McAfee PC, Picetti GD III, BenYishay
A, Acuff TE: Videoassisted thoracic surgery for the anterior
approach to the thoracic spine. Annals of Thoracic Surgery 59:11001106,
1995.
4. McAfee PC, Regan JJ, Zdeblick T, Zuckerman J, Picetti GD III,
Heim S, Geis WP, Fedder IL: The incidence of complications in
endoscopic anterior thoracolumbar spinal reconstructive surgery.
A prospective multicenter study comprising the first 100 consecutive
cases. Spine 20:16241632, 1995.
5. Newton PO, Wenger DR, Mubarak SJ, Meyer RS: Anterior release
and fusion in pediatric spinal deformity. A comparison of early
outcome and cost of thoracoscopic and open thoracotomy approaches.
Spine 22:13981406, 1997.
6. Lenke LG, Betz RR, Harms J, Clements DH, Lowe TG, Bridwell
KH: A new and comprehensive classification system of adolescent
idiopathic scoliosis. Spine in press: 2001.
7. Lenke LG, Betz RR, Harms J, Bridwell KH, Clements DH, Lowe
TG: Spontaneous lumbar curve correction following selective anterior
or posterior thoracic fusion in adolescent idiopathic scoliosis.
Spine 24:16631671, 1999.
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