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P R O C ED U R E 3 8
Hemivertebrae
Resection
Rani Nasser, Matías G. Petracchi, Oheneba Boachie-Adjei,
and John K. Ratliff
I N D I CAT I O NS P I T F A L L S
• During the adolescent growth spurt,
patients with congenital kyphoscoliosis
may incur a rapid deterioration because
of compression of the spinal cord.
• Adolescent growth spurt occurs at a
mean age of 13.7 years.
• Hemivertebrae located higher up in
the spine (cervical or thoracic) have a
higher risk of intraspinal abnormalities.
FIGURE 38-1
Indications
n
The primary objective in surgical treatment of hemivertebrae is to prevent the
progression to severe spinal deformity.
n
Ideal surgical candidates should have their deformity addressed before the
development of compensatory curves.
• Progressive curve greater than 40 degrees
• Pelvic obliquity with deviation generating spinal imbalance
n
Single, fully segmented hemivertebrae located at the thoracolumbar junction
can deteriorate at a rate of 2 to 3.5 degrees per year.
n
Hemivertebrae may lead to a rapidly progressing torsional deformity.
• Anatomic convex compression can transform into a concave mechanical
compression.
Examination/Imaging
n
History and physical (Figure 38-1)
n
Routine history and physical with special attention to progression of
deformity
• Hemivertebrae deformities do not follow any clear genetic inheritance
patterns.
• Consider anomalies associated with the spectrum of spine deformity.
◆
VACTERL syndrome: vertebral anomalies, anal atresia, cardiovascular
anomalies, tracheoesophageal fistula, esophageal atresia, renal and/or
radial anomalies, and/or limb defects (1 in 10,000-40,000 live births)
◆
Genitourinary tract anomalies (26%)
◆
Cardiac defects (26%)
n
Imaging
• Radiographs
◆
Anteroposterior (AP) (Figure 38-2, A and C ) and (Figure 38-2, B) lateral
◆
Dynamic bending and traction films
• Computer tomography
◆
Coronal, sagittal, and three-dimensional reconstructions
• Magnetic resonance imaging (sagittal, Figure 38-3, A; and coronal, Figure
38-3, B)
◆
Evaluate for possible associated cord abnormalities.
• Arnold-Chiari malformation, syringomyelia, diastematomyelia, diplomy-
elia, or a tethered cord
360 Procedure 38 | Hemivertebrae Resection
T R E A T M E N T OP T I O N S
• In situ posterior fusion
• The technique is not indicated in
patients who are skeletally immature.
• Isolated posterior fusion is not
preferred in young children, because
of the reduced potential for
correction.
• Thirty-six percent of young children
by age 4 years could develop lordosis
and bending of the fusion mass as
the unfused anterior vertebral bodies
continue to grow.
• Known as the crankshaft
phenomenon
• Treatment goal is preventative and
does not primarily address correction.
• Combined anterior and posterior fusion
• More substantial correction with
diskectomies, combined anterior and
posterior reconstruction of spinal
deformity
• No crankshaft complications
• Decreased risk of pseudarthrosis
• May leave a residual curve, loss of
growth potential in fused segments
• Epiphysiodesis
• Growth arrest on the convex side is
indicated in patients with growth
potential remaining only on the
concave side.
• Concave growth is unpredictable and
kyphosis may develop with growth of
the posterior elements.
• Convex hemiepiphysiodesis
performed across the entire
measurable curve
• Optimized in patients less than 5
years old whose curve deformity has
not progressed beyond 60 degrees.
• Hemivertebrae resection
• Eliminates potential for curve
progression and potential to correct
60% to 70% of deformity
• Adjacent segments not involved and
have no restriction on growth
• Decreases risk of pseudarthrosis and
crankshaft phenomenon
• Could be performed as a combined
anterior/posterior (single session or
staged by 10 days) or posterior
approach
63°
A
34°
12
6
7
8
9
10
11
13
B
9
63°
12
C
FIGURE 38-2, A-C
Procedure 38 | Hemivertebrae Resection 361
A
FIGURE 38-3, A-B
P O S I TI O N I N G PE A R L S
• Abdomen relieved of all pressure while
prone
P O S I TI O N I N G EQ U I P M EN T
• Relton-Hall four-poster frame for prone
cases
P O RTA L S / E X P O S U R ES
P I T F A L L S
• A wake-up test after reducing
maneuvers and stabilization if
intraoperative monitoring is not reliable.
P O RTA L S / E X P O S U R ES
E Q U I PM E N T
• Fluoroscopy
• Cell Saver
• Somatosensory and motor evoked
potentials during the procedure
B
Surgical Anatomy
n
Expose the convex and anterior side of the hemivertebrae.
Positioning
n
Lateral decubitus position
• Use lateral-posterior or simultaneous anterior/posterior approaches.
• Special attention should be paid to position the convex side up.
n
Prone position
• For single posterior approaches or sequential anterior-posterior approaches
• Relton-Hall four-poster frame (or similar device)
Portals/Exposures
n
In thoracic or thoracolumbar approaches, the rib that is one or two levels above
the hemivertebrae is removed.
n
Subperiosteal dissection of posterior elements is performed at the level of the
hemivertebrae.
362 Procedure 38 | Hemivertebrae Resection
S T E P 1 P EA R L S
• Directly excising the hemivertebrae
and appended structures will provide
immediate correction of the existing
deformity.
• Perform intraoperative monitoring of
evoked potentials.
• Dissect hemivertebrae from the convex
aspect toward the concave.
• Place thrombin-soaked gelatin over the
dura if it is exposed.
• The dissected hemivertebrae is cut into
morsels and is later used as a graft in
filling the cavity created from the
resection.
S T E P 1 P IT FA L L S
• To prevent neurologic injury consider
temporary stabilization with laminar
hooks.
Procedure A: Lateral-Posterior Lumbar Hemivertebra Resection and Correction with Segmental Anterior Instrumentation
Step 1
n
The patient is placed in the lateral decubitus position on the concave side.
n
Make an L-shaped lateral/longitudinal incision 3.5 cm lateral from the spinous
processes, above and below the hemivertebrae (Figure 38-4, A).
n
The posterior elements of the convexity are exposed subperiosteally.
n
Perform excision of the lamina, facets, pedicle, transverse process, and the
posterior part of the hemivertebrae.
• Disk material on both sides of hemivertebrae is excised completely.
• Excise the vertebral epiphyseal plates.
Step 2
n
An anterior incision is performed.
n
The remainder of the hemivertebrae is excised anteriorly.
n
Stabilization and compression may be performed with the use of baby Cotrel–
Dubousset (CD) Horizon or mini-Harrington instrumentation.
33°
A
FIGURE 38-4, A-B
9
63°
12
B
Procedure 38 | Hemivertebrae Resection 363
S T E P 1
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• Laminar hooks
S T E P 2 P EA R L S
• The fibular graft is used as a strut
between the two adjacent vertebral
bodies to prevent further kyphotic
deformity.
• The laminae and facets above and
below the hemivertebrae are
decorticated on the convex side.
S T E P 2 P IT FA L L S
• Hemivertebrae resection may create a
posterior gap.
S T E P 2
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• Baby Cotrel–Dubousset (CD)
• Mini-Harrington
• Medtronic Sofamor Danek Company
S T E P 1 P EA R L S
• Place thrombin-soaked gelatin over
dura if it is exposed.
• A hinge consisting of a small portion of
the annulus is preserved on the concave
side to avoid lateral translation of the
adjacent structures.
• The dissected hemivertebrae is cut into
morsels and is later used as a graft in
filling the cavity created from the
resection.
Procedure B: Hemivertebra Resection and Fusion: Anterior and Posterior Approach
Step 1
n
Anterior approach
• Make a linear incision from the approach side to the opposite side.
• Retract the psoas muscle and pleura from the vertebral bodies.
• Perform diskectomies caudal and cephalad from the hemivertebrae.
n
Resect vertebral body (Figure 38-4, B).
Step 2
n
Expose the posterior elements subperiosteally.
• Excise the lamina, facets, transverse process, and pedicle remnants.
n
Definitive stabilization is achieved by compressing the convex side.
n
Stabilization may also be attained by casting.
• Pantaloon spica casting keeps the patient toward the convexity.
Procedure C: Posterior Hemivertebra Resection and Correction
Step 1
n
Make a longitudinal incision along the entire scoliotic curvature (see Figure
38-2, C ).
n
Expose the lateral tip of the transverse processes subperiosteally.
n
Resect the spinous process, lamina, and facet of the hemivertebrae.
n
Pedicle resection is performed anteriorly until the lateral and anterior cortex of
the vertebral body is reached.
n
Disk material and end plates are removed.
Step 2
n
After hemivertebrae resection, hooks and pedicle screws are placed (Figure
38-5 A [AP view] and B [lateral view]).
n
Rods are bent to accommodate the convex side.
n
Crushing the osteotomy gap with compression force will correct the kyphotic
deformity as well as the scoliotic curvature.
n
Transverse processes and posterior elements are decorticated.
S T E P 1 P IT FA L L S
• Avoid damage to nerve roots exiting
from underneath the pedicle.
• If bleeding from epidural veins is
encountered:
• Use bipolar cautery if the site of
epidural hemorrhage can be
localized.
• Thrombin-soaked gelatin or other
hemostatic agents may be used.
• Temporary stabilization is recommended
before posterior approach to prevent
potential neurologic injury.
S T E P 2 P IT FA L L S
• The initial part of the stabilization may
be performed during the posterior
hemivertebrae resection.
364 Procedure 38 | Hemivertebrae Resection
S T E P 2
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• A wide range of instrumentation should
be available in the operating room,
including screws (pedicle, iliac), hooks,
and cables or wires.
• Pantaloon spica casting may be used.
S T E P 1 P EA R L S
• Resection of the pedicle and transverse
process is performed under direct
visualization of the spinal cord.
• In the thoracic hemivertebrae, the
attached rib is excised up to a 3-cm
length.
• Cortex removal is not necessary
because of the compressive forces
applied to the convex side.
• Residual cortical shell is crushed and
closes the osteotomy gap.
S T E P 1 P IT FA L L S
• Excising disk material on the concave
side may be problematic.
• These far lateral disk components are
beneficial during the correction.
• This remnant disk and annulus serve
as a hinge to prevent translation of
the vertebral body.
S T E P 2 P EA R L S
• Placement of anchors should be
designed to allow compression force
application to the convex side.
• Distraction forces should be directed
toward the concave side.
• A second rod could be applied to the
concave side to provide extra stability.
S T E P 2 P IT FA L L S
• A bony gap often remains at the site of
the resected hemivertebrae.
S T E P 2
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• A wide range of instrumentation should
be available in the operating room,
including screws (pedicle, iliac), hooks,
and cables or wires (see Figure 38-5).
A
B
FIGURE 38-5, A-B
Procedure 38 | Hemivertebrae Resection 365
P O S T OP E R AT IV E P E A R L S
• Obtain cell blood counts to analyze
hematocrit and hemoglobin
postoperatively.
P O S T OP E R AT IV E
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• Custom-molded rigid brace should be
worn to protect the instrumentation for
6 months.
Postoperative Care and Expected Outcomes
n
Standing AP and lateral views of the full spine should be attained postopera-
tively before hospital discharge, with the patient wearing the brace.
• The same studies should be repeated before the follow-up visit.
Evidence
Bollini G, Docquier PL, Viehweger E, Launay F, Jouve JL. Lumbar hemivertebra
resection. J Bone Joint Surg Am 2006;88:1043-52.
This study demonstrated that excision of a lumbar hemivertebra is safe and
provides stable correction when combined with a short-segment fusion and
when performed as early as possible.
Bollini G, Docquier PL, Viehweger E, Launay F, Jouve JL. Thoracolumbar
hemivertebrae resection by double approach in a single procedure: long-term
follow-up. Spine 2006;31:1745-57.
This study demonstrated that thoracolumbar hemivertebrae resection by double
approach is safe and offers a persistent correction with a short-segment fusion.
Hedequist DJ, Emans JB. Congenital scoliosis. J Am Acad Orthop Surg 2004;12:
266-75.
This article reviewed congenital scoliosis, embryologic errors in vertebral column
formation, predicting the natural history, and applying the correct treatment.
Hedequist DJ, Emans JB. The correlation of preoperative three-dimensional
computed tomography reconstructions with operative findings in congenital
scoliosis. Spine 2003;28:2531-4.
The data demonstrated three-dimensional reconstructions of computed
tomography scans and the utlility of visualizing posterior vertebral anomalies
associated with hemivertebra.
Hedequist DJ, Hall JE, Emans JB. Hemivertebra excision in children via
simultaneous anterior and posterior exposures. J Pediatr Orthop 2005;25:60-3.
This study reported that hemivertebra excision by simultaneous anterior/
posterior exposure is effective and safe in managing congenital hemivertebra.
Correction results were comparable to posterior-only procedures and staged
anterior-posterior procedures.
Lazar RD, Hall JE. Simultaneous anterior and posterior hemivertebra excision.
Clin Orthop Relat Res 1999;364:76-84.
This report described simultaneous anterior/posterior resection of the
hemivertebra and correction of deformity with posterior instrumentation in 11
patients, with immediate postoperative curves averaging 13 degrees (range, 1
to 40 degrees). At a mean of 28 months follow-up, the curves averaged 14
degrees (range, 1 to 47 degrees).
McMaster MJ, Ohtsuka K. The natural history of congenital scoliosis: a study of
two hundred and fifty-one patients. J Bone Joint Surg Am 1982;64:1128-47.
This study described the natural history of congenital scoliosis in 251 patients.
Nasca RJ, Stilling FH III, Stell HH. Progression of congenital scoliosis due to
hemivertebrae and hemivertebrae with bars. J Bone Joint Surg Am
1975;57:456-66.
This study reported that the rate of progression of the scoliosis was variable,
ranging from 1 to 33 degrees per year (average, 4 degrees per year).
Ruf M, Harms J. Posterior hemivertebra resection with transpedicular
instrumentation: early correction in children aged 1 to 6 years. Spine
2003;28:2132-8.
This study advocated early correction surgery of congenital scoliosis, before the
development of severe local deformities and secondary structural changes.
Shono Y, Abumi K, Kaneda K. One-stage posterior hemivertebra resection and
correction using segmental posterior instrumentation. Spine 2001;26:752-7.
The results of this paper indicate that correction of kyphoscoliosis caused by
a single hemivertebra can be treated by one-stage posterior hemivertebra
resection and correction using segmental posterior instrumentation.
Solomon BD. VACTERL/VATER Association. Drphanet J Rare Dis 2011;6:56.
P R O C ED U R E 3 9
Lumbar Internal
Laminectomy
Sunil Jeswani, Eli M. Baron, and Neel Anand
I N D I CAT I O NS P I T F A L L S
• The presence of lateral listhesis or
pedicle-on-pedicle stenosis in the
setting of deformity may predispose to
treatment failure.
T R E A T M E N T OP T I O N S
• Lumbar laminectomy
• Bilateral laminoforaminotomies with
mesial facetectomy
• Lumbar fusion
P O S I TI O N I N G PE A R L S
• Alternatively the patient may be placed
on a Jackson table. A decompression
performed with the spine in extension
may achieve a more thorough
decompression as any compression is
removed in a position more accurately
simulating the neutral standing
position.
Indications
n
Lumbar stenosis
n
Lumbar stenosis in the setting of unilateral disk herniation
n
Low-grade degenerative spondylolisthesis without gross instability on flexion-
extension views
Surgical Anatomy
n
The pars interarticularis should be identified, because violation of this structure
may predispose to instability.
n
The location of the pedicle should be established early in the procedure. Local-
ization is based on the pedicle of the inferior level being decompressed (e.g.,
the L5 pedicle in an L4-5 decompression.
n
Certain anatomic configurations of the lumbar spine facilitate easier decompres-
sion by this approach. If the transverse diameter of the lumbar spinal canal is
congenitally narrowed, then the position of the posterior osseous roof of the
spinal canal will be relatively vertical. This configuration will allow easy achievement of an optimal working angle of the microscope, which will facilitate
contralateral decompression of bone and ligamentum flavum. Conversely, if the
anteroposterior diameter of the spinal canal is congenitally narrowed, then the
position of the osseous canal roof will be relatively horizontal. In this case,
achieving an optimal working angle for the visualization of the contralateral
structures will be more difficult.
Positioning
n
The patient is placed in the prone position, typically on a Wilson frame.
n
The lumbar spine is gently flexed to increase the width of the interlaminar space.
Portals/Exposures
n
This technique is theoretically advantageous to bilateral microdecompression as
well as standard laminectomy, because unilateral exposure may result in reduction of risk for disruption of spinal stability and less postoperative pain.
n
Because only the ipsilateral paraspinal musculature is dissected unilaterally, the
contralateral paraspinal musculature remains intact, resulting in the preservation
of the contralateral bone/muscle complex. This conceivably results in added
postoperative stability compared with a bilateral approach.
S T E P 2 P EA R L S
• The authors use a straight curette to
detach the ligamentum flavum from the
inferior lamina and the superior
articular facet. This is followed by use
of a curved curette to ensure the
ligamentum is detached.
• Afterward, a no. 2 Kerrison rongeur is
used to perform the initial bite of bone
to minimize the risk of compressive
neural injury.
• The authors generally attempt to avoid
removal of bone from the inferior
lamina rostral edge, because this may
predispose to pars fracture.
Procedure 39 | Lumbar Internal Laminectomy 367
n
A study by Adams and associates suggested that the muscular attachments to
the posterior arch and the insertions of the muscular slips on the facet capsule
serve to brace the facets, improving their ability to resist displacement.
n
Because dissection and retraction of the multifidus muscle is carried out unilater-
ally with this technique, less postoperative dead space results.
n
Postoperative dead space can have significant consequences. Increased volume
of the dead space may result in increased blood loss. Moreover, increased dead
space provides an ideal bacterial culture medium, with the potential for increasing the chance of a postoperative infection.
Procedure
Step 1
n
A longitudinal skin incision is made over the affected segment.
n
Subsequently, the lumbodorsal fascia incision is made ipsilaterally, approxi-
mately 1 cm off midline on the side that is more symptomatic.
n
The multifidus muscle is subsequently retracted off the spinous process and
lamina.
n
Alternatively, the approach using a tubular retractor system has also been
described.
Step 2
n
A laminotomy is subsequently performed on the ipsilateral side, with the ipsi-
lateral cephalad lamina partially removed using a high-speed drill and Kerrison
rongeurs. The resection of the cephalad lamina should be extended until the
insertion of the ligamentum flavum and the dura are visible. This may be performed in a “trumpeted” fashion to preserve as much of the lamina as possible
by angling the microscope. The ligamentum flavum is exposed.
n
The mesial inferior facet is drilled so that the superior articular facet can be
visualized. Figure 39-1 is a postlaminotomy intraoperative photograph that
shows removal of the mesial surface of the inferior facet. Note the exposed
superior articular facet.
Ligamentum
flavum
Medial
FIGURE 39-1
Rostral
Lateral
Superior
articular facet
368 Procedure 39 | Lumbar Internal Laminectomy
A
FIGURE 39-2, A-B
A
FIGURE 39-3, A-B
B
B
S T E P 3 P EA R L S
• If there is significant central stenosis,
the central ligamentum flavum should
be removed before addressing
foraminal pathology to minimize risk of
neural injury by compressing the neural
elements while working in the foramen.
n
The ligamentum flavum is then elevated using curettes and dissectors. A curette
is used to release the ligamentum flavum, first medially (Figure 39-2, A), then
laterally (Figure 39-2, B). Note that the curette stays in the plane between the
bone and the ligamentum.
n
The ligamentum flavum is subsequently resected. The ligamentum flavum is
elevated with a dental tool (Figure 39-3, A) and then resected with a Kerrison
rongeur (Figure 39-3, B). The microscope is then angled toward the ipsilateral
facet and subarticular zone.
n
After entering the spinal canal, the first structure to be identified should be the
pedicle. The pedicle serves as a reference point for the decompression and
orients the surgeon both in terms of locating the foramen and locating neural
structures. Descending nerve roots are always medial to the pedicle.
Step 3
n
Using Kerrison rongeurs, the ipsilateral lateral recess and foramen is decom-
pressed (Figure 39-4). All soft tissue and bony stenosing pathology is resected
from the recess and foramen.
n
A Murphy probe or a Woodson dissector should be easily passable through and
out the foramen.