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Procedure 18 | Operative Management of Scheuermann Kyphosis 167
S T E P 1 P EA R L S
• Resecting the anterior portion of the
rib head allows more exposure of the
posterior disk.
• A laminar spreader can be used to view
the remaining disk after the initial
diskectomy.
• It is critical to release the anterior
longitudinal ligament, because this is
part of the deforming force.
• Chest tubes are discontinued when
drain output is less than 80 mL per
8-hour shift.
S T E P 1 P IT FA L L S
• Anterior approaches require deflation of
the ipsilateral lung.
• The segmental vessels should be
maintained, because they are critical to
the stretched spinal cord.
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
• Specialized thoracoscopic equipment is
needed for VATS.
• Reduction screws below the apex
facilitate rod placement.
Procedure
Step 1: Anterior Release and Fusion
n
Perform an open or video-assisted thoracoscopic approach.
n
Disks that do not become lordotic on hyperextension radiographs should be
resected.
n
A strut graft can be placed to enhance fusion and prevent loss of correction.
n
Reintubate with a single-lumen tube after closure of the anterior approach, and
turn the patient into the prone position.
Postoperative Care and Expected Outcomes
n
Bracing is typically not necessary.
n
Patients are maintained in the intensive care unit or a monitored bed
overnight.
n
Ambulation is encouraged on the first postoperative day.
Upper fusion level
S T E P 1 C ON T R O V ER S I E S
• A thoracic surgeon may be required for
anterior approaches.
• A vertebral column resection (VCR) or
pedicle subtraction osteotomy (PSO) in
posterior-only fusion may lead to
correction equal to that of anterior
release and posterior fusion.
• Performing a VCR or PSO at cord level
potentially carries a higher risk of
neurologic complications, especially in
older patients.
• Combined procedures have a higher
incidence of general complications than
posterior-only surgery.
• VATS has been found to result in
less morbidity than conventional
thoracotomy, but it is approximately
30% more expensive.
S T E P 2 P EA R L S
• The distal end of the instrumentation
should be the sagittal stable vertebra,
which is the most proximal
thoracolumbar or lumbar vertebra
intersected (not bisected) by the
posterior sacral vertical line.
• The proximal end of the
instrumentation should be the proximal
vertebra measured in the Cobb angle
(Figure 18-1).
Cobb angle
Lower fusion level
FIGURE 18-1
168 Procedure 18 | Operative Management of Scheuermann Kyphosis
S T E P 2 P IT FA L L S
• If an apical disk herniation is seen on
the MRI, an anterior diskectomy or VCR
should be performed before curve
correction.
• A thoracic VCR requires resection of
the rib head and often sacrifices the
nerve root.
• The mean arterial pressure should be
increased to at least 75 mm Hg before
correction.
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 rigid rod for PSF (
steel) will prevent loss of correction.
1
-inch stainless
4
S T E P 2 C ON T R O V ER S I E S
• Posterior-only instrumentation with
thoracic pedicle screws and segmental
osteotomies can reduce operative time,
blood loss, and complication rates
compared with anterior-posterior
fusion.
A B
FIGURE 18-2, A-B
P O S T OP E R AT IV E P I T F A L L S
• The risk of superior mesenteric artery
syndrome is not insignificant.
• Presentation includes nausea, vomiting,
and abdominal pain.
• Treatment is to maintain “nothing by
mouth” status until the syndrome
resolves with adequate hydration.
Step 2
n
Perform a wide release, including a radical facetectomy at the apex and at the
three adjacent cranial and caudal levels.
n
Bilateral pedicle screws should be inserted at the apex and at least eight screws
above and eight screws below the apex.
n
A rod should be contoured to normal sagittal alignment.
n
The rod is inserted into the proximal screws (Figure 18-2, A) and cantilevered
into the remaining screws (Figure 18-2, B).
n
Once the rod is seated, additional compression will close the segmental oste-
otomies and increase curve reduction.
n
If a PSO or VCR is performed, a temporary fixation rod is required for any cor-
rection maneuvers.
Procedure 18 | Operative Management of Scheuermann Kyphosis 169
Evidence
Arlet V, Schlenzka D. Scheuermann’s kyphosis: surgical management. Eur Spine J
2005;14:817-27.
This review article discusses the use of newer segmental instrumentation used
to correct kyphosis. The four-rod technique as well as various compression
techniques are also presented.
Boachie-Adjei O, Sarwahi V. Scheuermann’s kyphosis. In: DeWald RL, editor. Spinal
Deformities: The Comprehensive Text. New York: Thieme Medical Publishers;
2003, p. 777-86.
This chapter describes some of the surgical concepts and techniques that are
used to correct kyphosis in Scheuermann disease.
Lee SS, Lenke LG, Kuklo TR, et al. Comparison of Scheuermann kyphosis correction
by posterior-only thoracic pedicle screw fixation versus combined anterior/
posterior fixation. Spine 2006;31:2316-21.
This article describes the clinical and radiographic results of 18 patients who
underwent posterior-only fusion compared with 21 patients who underwent
anterior/posterior fusion. With the use of segmental osteotomies and thoracic
pedicle screws, posterior-only fusion seems to be superior to combined fusion
when using hybrid hook/screw constructs.
Murray PM, Weinstein SL, Spratt KF. The natural history and long-term follow-up
of Scheuermann kyphosis. J Bone Joint Surg Am 1993;75:236–48.
This classical article describes the long-term follow-up of 67 patients with
Scheuermann kyphosis followed for an average of 32 years compared with a
control group. The patients with Scheuermann kyphosis had more intense back
pain, jobs that required less activity, and less range of motion of trunk
extension.
I N D I CAT I O NS P I T F A L L S
• Presence of concurrent neural axis
lesions
P R O C ED U R E 1 9
Resection of Intradural
Intramedullary or
Extramedullary
Spinal Tumors
John Christos Styliaras, Ashwini Sharan, John Birknes,
John K. Ratliff, and James S. Harrop
Indications
n
Spinal cord compression can manifest as
• Weakness (in either upper or lower extremities, or both)
• Loss of bowel and bladder function
• Sensory loss (to light touch or pinprick)
• Incoordination of hands or gait
n
Symptomatic neuronal compression, manifesting as radiculopathy
n
Progressive growth of lesion on serial imaging
n
Persistent pain or radiculopathy
n
Spinal deformity resulting from remodeling of osseous elements
Examination/Imaging
n
Physical examination
• Spinal cord compression—myelopathy
• Radicular signs or symptoms
• Dermatologic findings in neurocutaneous disorders (e.g., neurofibromatosis)
n
Plain films/computed tomography (CT) scan
• Typically nondiagnostic
• Bone erosion or remodeling of osseous elements (scalloping) resulting from
prolonged presence of the lesion may be seen, but not often.
• May use CT scan to diagnose bony versus soft tissue cord compression
n
Magnetic resonance imaging (MRI) with gadolinium
• Study of choice, because it provides more information about the lesion itself
• Differentiates type of intradural lesion
◆
Extramedullary—extrinsic to the spinal cord
• Meningioma—dural based. On T1- and T2-weighted images, it appears
as a homogenous hypointense lesion compared with the cord, while on
contrast-enhanced MRI, it enhances homogenously. In addition, many
times it is calcified.
• Nerve sheath tumor (schwannoma and neurofibroma): The tumor is a
dumbbell-shaped lesion that has a separate plane, is extrinsic to the
spinal cord, and follows the nerve through the neural foramina (Figure
19-1, A). Coronal Images (Figure 19-1, B) illustrate the path of nerve
sheath tumor exiting the foramen around the pedicle. On T1-weighted
images, it is isointense to the cord, while on T2 images, it appears
heterogenous and hyperintense. On contrast-enhanced MRI, it often
appears with an irregular margin and ring-shaped enhancement.
Procedure 19 | Resection of Intradural Intramedullary or Extramedullary Spinal Tumors 171
A
FIGURE 19-1, A-B
T R E A T M E N T OP T I O N S
• Maximal tumor resection: Favorable
outcomes postoperatively on
intramedullary tumors are based on
the histopathology of the tumor, total
resection, and neurologic status
preoperatively. In extramedullary
tumors, postoperative neurologic
recovery is very favorable in the vast
majority of cases.
• Serial observation with imaging and
clinical assessment is an option for
intradural spinal cord tumor
management in neurologically intact
patients.
• Radiation therapy is a secondary
treatment option or an adjuvant
therapy in malignant or rapidly
recurrent intramedullary spinal tumors
(although optimum management in
such cases remains controversial).
B
FIGURE 19-2
◆
Intramedullary—located within spinal cord parenchyma (Figure 19-2)
Expansion of the spinal cord
•
• Associated with intraparenchymal cyst or syrinx
• Primary glial neoplasms (e.g., ependymoma) predominate. On T1-
weighted images, they appear isointense to the cord, while on T2weighted images, they are hyperintense. On contrast-enhanced MRI,
these lesions present with a well-defined margin and homogenous
enhancement.
172 Procedure 19 | Resection of Intradural Intramedullary or Extramedullary Spinal Tumors
Surgical Anatomy
n
Spinal column defines boundaries of the spinal canal. These boundaries are
• Anterior—vertebral body
• Lateral—pedicles
• Posterior—laminae and spinous processes
n
Levels of the spinal column are
• Cervical—7 vertebrae
• Thoracic—12 vertebrae
• Lumbar—5 vertebrae
n
Spinal meninges or coverings of the spinal cord
• Dura mater
◆
Thick fibrous layer
◆
Separated from osseous region by a space containing epidural veins,
adipose, and fibrous tissue
• Arachnoid
◆
Delicate layer in between the dura and pia mater, containing the subarach-
noid space
◆
The subarachnoid space is filled with cerebrospinal fluid and extends down
to S2
• Pia mater
◆
Thin layer on the surface of the spinal cord
◆
Contacts the spinal cord and is adherent to blood vessels entering the
spinal cord
n
Spinal cord
• Approximately 45 cm in length
• Thirty-one pairs of spinal nerves arise from the spinal cord: 8 cervical, 12
thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
• Conus medullaris: terminal end of the spinal cord (ends at level L1-2)
• Filum terminalis: fibrous band that continues distally and attaches to the
dorsum of the first coccygeal vertebrae
• Spinal cord: highly organized, somatotopically arranged tissue composed of
two functionally and anatomically distinct regions
◆
Gray matter—central portion; consists of neuronal cell bodies and sup-
porting structures
• Axial plane—central bridge of gray matter connecting each side such
that, in an axial section, it resembles the letter H
• Ventral portion—anterior horn motor cells
◆
White matter
• Encircles gray matter
• Composed of both myelinated and unmyelinated axonal tracts
◆
Central canal—in the middle of the H
• Embryologic remnant from neurulation of the neural plate
• Continuation of the fourth ventricle from the medulla
• Spans the entire length of the spinal cord and terminates as a fusiform
terminal ventricle in the conus medullaris
• Lined with cuboidal ependymal cells
Procedure 19 | Resection of Intradural Intramedullary or Extramedullary Spinal Tumors 173
FIGURE 19-3
P O S I TI O N I N G PE A R L S
• With surgical positioning, minimizing
compression upon the abdomen
reduces intraabdominal pressure and
thus epidural venous pressure. This
reduces intraoperative blood loss.
• Localization of thoracic lesions may be
difficult. Either preoperative localizer or
entire spine radiograph may aid in
localizing incision and tumor.
P O S I TI O N I N G PI T FA L L S
• If shoulders are taped, ensure that the
brachial plexus is not stretched.
Intraoperative free-running
electromyography or intraoperative
upper extremity somatosensory evoked
potentials may help limit plexus palsies.
P O RTA L S / E X P O S U R ES
P E A R LS
• A short-acting muscle relaxant will
provide easier dissection but also enable
the use of neurophysiologic monitoring.
• An intraoperative localizing radiograph
aids in minimizing osseous removal.
• Laminectomy should provide exposure
of dural region necessary to define
neoplasm margins, and a slightly
greater incision provides for
manipulation of the lesion.
• A hemostatic agent applied along the
epidural and bony edges will be useful
to tamponade any venous bleeding.
FIGURE 19-4
Positioning
n
General anesthesia with neurophysiologic monitoring
n
Prone position with spinal axis in the midline
• Ensure eyes are not subject to external compression
• Ensure endotracheal tube is free and not obstructed
• Pad extremity peripheral nerves over bony protuberances (i.e., ulnar and
peroneal)
n
Occiput to T4 lesions (Figure 19-3)
• Application of a Mayfield headholder
• Neck remains in neutral position, and no external compression on the orbit
or endotracheal tube
• Shoulder taped to facilitate imaging
n
T4 to sacrum lesions (Figure 19-4)
• Andrews frame or laminectomy rolls
• Abdomen free of pressure, which provides for a decrease in the epidural
venous pressure
Portals/Exposures
n
Localize midline region and plan extent of laminectomy or bony removal.
n
Make a midline incision down to the paraspinal fascia.
n
Avascular subperiosteal dissection is continued bilaterally, centered over spinous
process and laminae.
n
The retractor system should be low profile and away from the surgical site.
n
Use a high-speed drill to resect posterior elements.
n
Drill through the laminae bilaterally at the facet–laminae junction.
n
Resect the rostral and caudal interspinous ligaments.
n
Resect the laminae en bloc and carefully dissect free all dural adhesions
(Figure 19-5).
n
Confirm that the extent of dural exposure is adequate through
• Palpation of the lesion
• Radiographic confirmation
• Intraoperative ultrasound
n
Confirm that hemostasis is excellent, particularly at dural margins.
174 Procedure 19 | Resection of Intradural Intramedullary or Extramedullary Spinal Tumors
P O RTA L S / E X P O S U R ES
P I T F A L L S
• Do not expose facet joints, because this
may lead to delayed instability.
• With inadequate hemostasis,
particularly for epidural bleeding,
bleeding will become excessive once
the dura is opened.
• Inadequate exposure may create the
need for further bony resection when
the dura is opened and will allow
unnecessary entry of blood and osseous
shavings into the dural sac.
P O RTA L S / E X P O S U R ES
E Q U I PM E N T
• Retractor with low-profile bar: provides
area to attach dural or pial sutures
• Paraspinal muscle hooks: provide
exposure and are away from
surgical site
S T E P 1 P EA R L S
• Fold the dural edges over hemostatic
strips, which are packed into the
epidural space with the tack-up sutures.
• Tack-up sutures to the lateral muscles
provide greater access to the spinal
canal.
S T E P 1 P IT FA L L S
• Inadequate exposure before opening
the dura results in the potential for
bone and blood products to enter the
spinal canal.
FIGURE 19-5
Procedure
Step 1
n
Hemostasis is meticulously maintained, particularly in the epidural region, before
opening the dura.
n
The rostral and caudal extent of the spinal lesion are defined and assured to
be within the bony opening.
n
Based on preoperative images, a single dural suture is placed, through which
traction is applied to draw the dura away from the spinal cord.
n
A midline or lateral dural incision is made with a sharp instrument.
• Maintain the arachnoid plane if possible.
• The arachnoid is opened and spinal fluid allowed to flow freely and decompress the canal.
n
Dural tack-up sutures bilaterally maintain the exposure of the spinal lesion and
prevent blood products from entering the cerebrospinal fluid (Figure 19-6). In
addition, the epidural space can be visualized with the use of hemostatic material (Surgicel; Ethicon, Somerville, N.J.).
FIGURE 19-6
Procedure 19 | Resection of Intradural Intramedullary or Extramedullary Spinal Tumors 175
A
B
S T E P 2 P EA R L S
• The microscope should be balanced
with the correct cross-table
attachments.
• Add film or CD-ROM to the microscope
if applicable.
• Remove all previous surgical tools from
the field and replace with a
microdissection instrument set.
S T E P 2 P IT FA L L S
• Overmagnification using the microscope
may limit the field of view.
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
• Operative microscope
• Microdissection instrument set
S T E P 3 P IT FA L L S
• Active bleeding in the surgical bed is
consistent with residual tumor.
C
FIGURE 19-7, A-C
Step 2
n
An intraoperative microscope is brought into the surgical field.
• Provides illumination
• Higher magnification of field than standard loupes
n
Dissection with microinstrumentation enables the surgeon to
• Define normal anatomy proximal and distal to the lesion
• Outline proximal and distal extent of pathologic lesion (Figure 19-7)
• Determine nerve root or parenchymal involvement
Step 3
n
Extramedullary lesions
• Nerve sheath lesions should be dissected from the spinal cord, and entering
and exiting nerve rootlets should be defined (Figure 19-8).
• Neurofibromas and schwannomas may follow the exiting nerve and have a
“dumbbell” appearance on imaging studies.
◆
Opening the nerve sheath and debulking may provide for manipulation of
the intracanal portion away from the spinal cord.
◆
A major goal is to remove intracanal portion to prevent or remove cord
compression.
176 Procedure 19 | Resection of Intradural Intramedullary or Extramedullary Spinal Tumors
FIGURE 19-8
S T E P 3
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• Intraoperative ultrasonography
• Microdissection tools
• Neurophysiologic stimulation provides data on nerve conduction and potential sequelae of sacrifice.
• Meningiomas are dural based and dissected out en bloc and resected.
n
Intramedullary lesions
• Define the lesion with intraoperative ultrasonography.
• Plan the cordotomy incision and bipolar coagulation of dorsal vessels along
the cordotomy section.
• Make an incision parallel to posterior columns along the midline raphe.
• Biopsy the lesion and send the specimen to the pathologist.
• Lengthen the cordotomy to the extent of the lesion to enable removal of
rostral and caudal poles.
• Define the gliotic planes and infold the tumor into the dissected region.
• Cavitation of the tumor with collapsing of the edges of the tumor’s capsule
into the cavitation defect affords minimal manipulation of the neural
elements.
Step 4
n
After resection of the lesion, the wound is confirmed to have no active
bleeding.
n
Exploration of the surgical bed for residual neoplasm is necessary to confirm
gross total resection.
n
Dura is closed with nonabsorbable suture.
n
Before completion of the dural closure, saline is injected into the subarachnoid
space to confirm a watertight closure.
n
The wound is closed in multiple layers.
Postoperative Care and Expected Outcomes
n
MRI images of surgical resection should be obtained to confirm the extent of
resection and to serve as a basis for future comparisons.
n
On contrast-enhanced images, the amount of residual tumor can be assessed
and can help determine the postoperative course of treatment.