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A
SIS
R12
Skin
incision
Peritoneum
Anterior lateral
retroperitoneal
approach
Psoas
muscle
A
Posterior rods and
screw
Bone graft
B
Graft
embedded
in L 4
C
groove
Figure 47–2
(A) Anterior lateral incision. (B) Anterior lateral approach and exposure. (C) Stabilization with bone graft and posterior instrumentation. (D) Lateral radiograph of a freshfrozen allograft reconstruction following an L3 corpectomy for metastatic disease. Note the titanium cable that was required because of a vertical crack that was found
after the graft was inserted. Posterior segmental fixation significantly increases the immediate stability of this allograft reconstruction.
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SECTION III THE LUMBAR SPINE
Eurostile
D
length of the vertebral body. The width of the resection is pedicle to
pedicle and should provide complete decompression of the dural tube, exiting and traversing nerve roots. (Note: in certain cases for deformity or
degeneration where resection is performed only for the purpose of anterior
column reconstruction, a complete corpectomy down to the dura may not
be indicated.)
Stabilization
Structural autologous iliac crest, fibula or femoral allograft, polymethylmethacrylate (PMMA), and vertical cages are the materials that have been
effectively utilized as spacers following lumbar corpectomy (Fig. 47–2C).
None is predictably good as a stand-alone device in the lumbar spine.
These devices require supplemental stabilization either in the way of posterior segmental (pedicle) fixation or anterolateral plate or rod fixation
(Figs. 47–1C,D and 47–2D).
Pitfalls
1. Poor exposure
2. Not enough surgical staff
3. Poor hemostasis
Complications
General surgical: urinary tract infection (UTI), deep vein thrombosis
(DVT), wound infection, respiratory, cardiopulmonary.
Anterior Approach
1. Iliac vein tear
2. Iliac artery thrombosis
3. Bowel injury
4. Genitofemoral nerve injury
5. Retrograde ejaculation (superior hypogastric sympathetic plexus)
Device Related
1. Nerve root, spinal cord, or cauda equina injury secondary to poor
placement
2. Breakage or loosening of fixation with subsequent recurrent/progressive deformity
Fusion
1. Pseudarthrosis
2. Donor-site morbidity
3. Graft extrusion
4. Accelerated degeneration of adjacent level
Hints
Retraction
The Bookwalter retractor is extremely well suited for either the anterior or
anterior lateral retroperitoneal approach to the spine. The key is to use the
body wall blades on the midline side of the frame for retraction of the
abdominal contents and peritoneum. Great vessel retraction should not be
done via Bookwalter retractors. With the anterior paramedian approach,
retract the great vessels off the spine utilizing a hand-held Wiley-type vein
retractor (BAK sets have good imitations). When retracting the vessels, I
like to place a 3-inch cottonoid between the vein and the Wiley retractor. If
you find yourself short of assistance, you may place two medium-sized
smooth Steinmann pins into the vertebral body above and below the body
to be excised. You may protect the vessels by “insulating” the pin with a
red rubber catheter sheath. Note: when you are removing the pin is when
you are more likely to injure the vessel wall.
Corpectomy
When performing a corpectomy for compressive pathology (tumor, fracture fragments), it is necessary to remove the PLL, decompressing the full
extent of the dural tube at that level. In the surgical treatment of deformity
or degenerative disease, a corpectomy for anterior column reconstruction
usually does not require removal of the PLL.
Bleeding
Bleeding eventually stops. Packing, Gelfoam, and Avitene work well for
nonspecific soft tissue site bleeding. Bipolar electrocautery works well for
distinct epidural blooding. Bone wax is the choice for unacceptable bone
bleeding. In contradistinction to tearing segmental vessels, it is much easier to isolate, ligate (or clip), and then cut the segmental vessel. Take the
time to find them in the tumor, fracture, or deformity mass. The iliolumbar
vein has created problems for surgeons who felt it unnecessary to ligate it,
only to have it torn from zealous retraction later in the procedure. It is
much easier to isolate and control this vessel when it is not bleeding.
Hand-tying vessels probable works better but takes longer; auto vessel
clip appliers are faster and work fairly well. I usually reserve hand-tying
for the iliolumbar vein and back branches of the iliac vein. Do not put a clip
on the ureter! A small hole or tear in the iliac vein can usually be handled
with one or two passes with 6–0 Prolene sutures; place some Gelfoam and
thrombin on the site after repair. Large tears should be avoided! If one occurs, initially apply pressure to control the bleeding, and then get adequate
help and instrumentation and repair it with Prolene sutures.
Constructs
It is very difficult to apply an anterior lateral plate with the appropriate
orientation below L4. If the construct extends below L4, consider a direct
anterior approach with anterior construct appropriate for pathology (graft
with or without and anterior plate, transsacral graft, kick-out plate, PMMA
construct, or vertical Harm’s cage).
PMMA Construct
A PMMA construct is reserved for tumor reconstruction. A small-diameter
titanium rod (I often use a cross-link rod) spans the empty space following
tumor removal. It is important to have the rod embedded into the vertebral
body above and below tumor resection. A thin layer of Gelfoam can be
placed against the dura, and then PMMA in liquid form is used to fill the
space. While the PMMA is solidifying, adjust it so that it stays within the
corpectomy site. It is a simple concept of “reinforced concrete” that works
well for tumors. It is not a stand-alone construct in the lumbar spine and
should be supplemented with segmental pedicle fixation.
Transsacral Fibula Allograft
This is a good construct for grade III or greater spondylolisthesis being
treated with an in situ fusion. Place the graft through the vertebral body
above across the disc space into the vertebral body below. I like to use the
anterior cruciate ligament reconstruction reamer. It is a straight reamer that
works well, and you can template the fibula graft for a good fit. It is rare for
the graft to be longer than 60 to 65 mm.
Postoperative Care
1. Medical
a. DVT prophylaxis: sequential compression stockings during
surgery and postoperatively until full ambulation. Low-dose
aspirin; enoxaparin (Lovenox) or dalteparin (Fragmin) for highrisk patients.
b. Antibiotics: Intraoperative and 24 hours postoperative.
2. Bracing: Dependent on stability of reconstruction construct. Ranges
from cloth corset for comfort to TLSO with thigh extension.
3. Patient activity: early ambulation
Suggested Readings
Connolly PJ, Yuan HA. Reconstruction of anterior column gap: an over-
view. In: Margulies JY, Aebi M, Farcy JP, eds. Revision Spine Surgery.
St. Louis: CV Mosby; 1999.
Majd ME, Harkess JW, Holt RT, Madsen K, Mahan J. Anterior approach to
the spine. In: Margulies JY, Aebi M, Farcy JP, eds. Revision Spine
Surgery. St. Louis: CV Mosby; 1999.
Watkins RG. Surgical Approaches to the Spine. New York: Springer-Verlag;
1983.
Eurostile
47 LUMBAR CORPECTOMY
221
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48
Smith-Peterson-Type Osteotomy
Vincent J. Devlin
The Smith-Peterson-type osteotomy is a posterior wedge osteotomy
centered between the vertebral pedicles. A posterior wedge is resected in
such a manner that the axis of rotation is located at the anterior border of
the intervertebral foramen at the posterior aspect of the disc space. Closure of the posterior wedge osteotomy is accompanied by opening of the
anterior and middle spinal columns (Fig. 48–1). The Smith-Peterson-type
osteotomy can be performed at a single spinal level or at multiple adjacent spinal levels. This type of osteotomy can be performed either
through a previous posterior fusion mass or through a nonfused spinal region.
Goals of Surgical Treatment
1. Restoration of sagittal and coronal spinal balance in a patient with
fixed spinal deformity
2. Achievement of solid arthrodesis
3. Rigid internal fixation to permit brace-free mobilization
4. Relief of axial and radicular pain
Diagnosis
Patients who are candidates for spinal osteotomy procedures present with
varied symptoms that may include back pain, spinal fatigue, progressive
spinal deformity, and the inability to stand erect with the knees fully extended. A comprehensive musculoskeletal examination includes consideration of the following questions:
1. Is the most severe spinal deformity located in the sagittal plane or
coronal plane? Is a complex deformity involving multiple planes present?
2. Is the spinal deformity balanced or unbalanced? This is assessed by the
relationship of the C7 plumb line to the sacrum in the coronal and
sagittal planes.
3. Is the spinal deformity flexible or rigid? Are flexible nonfused spinal
segments present above or below a previously fused spinal region?
4. What is the relationship of the shoulders and pelvis to the spinal de-
formity? Factors such as shoulder imbalance, pelvic obliquity, and hip
flexion contractures require consideration when planning osteotomy
procedures.
Radiographic Assessment
Appreciation of normal three-dimensional spinal alignment is essential
when analyzing spinal radiographs. Spinal alignment is assessed on a
global, regional, and segmental basis using standing posteroanterior (PA)
and lateral radiographs taken on a 36-inch cassette (Fig. 48–2). Specialized
radiographs including supine anteroposterior (AP) bending views, traction
views, and hyperextension lateral radiographs are obtained as indicated.
1. Global assessment: In the coronal plane, a plumb line suspended from
C7 on a PA radiograph will bisect the vertebra below and pass through
the center of the sacrum in the absence of spinal deformity. Sagittal
plane balance is assessed by suspending a plumb line from the center of
C7. This global measurement is termed the sagittal vertical axis (SVA)
and normally falls anterior to the thoracic spine, through the center of
the L1 vertebral body, posterior to the lumbar spine and through S1.
2. Regional assessment: Cervical lordosis (occiput-C7) averages 40
degrees. In the thoracic region, normal kyphosis (T1-T12) ranges from
20 to 50 degrees with a tendency to increase slightly with age. The
thoracolumbar junction is essentially straight and serves as the transition area between the relatively stiff kyphotic thoracic region and the
relatively mobile lordotic lumbar region. Normal lumbar lordosis (L1S1) ranges from 30 to 80 degrees with a mean lordosis of 60 degrees.
3. Segmental assessment: The majority of cervical lordosis occurs at the
C1-C2 motion segment. The kyphosis in the thoracic spine usually
starts at T1-T2 and gradually increases at each level toward the apex
(T6-T7 disc). Below the thoracic apex, segmental kyphosis gradually
decreases until the thoracolumbar junction is reached. The thoracolumbar junction is essentially straight. Lumbar lordosis generally
begins at L1-L2 and gradually increases at each distal level toward the
sacrum. The apex of lumbar lordosis is normally located at the L3-L4
disc. Normally two thirds of lumbar lordosis is located between L4 and
S1 and one third between L1 and L3. Eighty percent of lumbar lordosis
occurs through wedging of the lumbar intervertebral discs and 20 % is
due to the lordotic shape of the vertebral bodies. It has been shown that
the wedge shape of the lowest three discs is responsible for one half of
the total lumbar lordosis.
Indications for Surgery
Patients with symptomatic fixed sagittal and/or coronal spinal deformity
merit consideration for surgical treatment with spinal osteotomy. Conditions for which spinal osteotomies are most commonly indicated include:
1. Ankylosing spondylitis
2. Postsurgical flat-back syndrome
3. Iatrogenic spinal deformities arising after scoliosis fusion
4. Posttraumatic kyphotic deformity
5. Transition syndromes (proximal or distal) following degenerative lumbar spinal procedures
Contraindications
1. Spinal deformities that can be treated by less extensive procedures
such as multiple anterior discectomies and fusion followed by posterior segmental spinal instrumentation and fusion.
2. Patients with severe degrees of fixed decompensated spinal deformities, in whom spinal balance would not be achieved despite multiple
Smith-Peterson-type osteotomies. This situation may occur when (1)
greater than 6 cm of fixed coronal imbalance exists; (2) a fixed upper
thoracic curve and pelvic obliquity coexist; or (3) asymmetric length
exists between the convex and concave sides of the spinal column. In
these cases, a vertebral column resection procedure is considered.
Advantages
1. May be used to treat coexistent sagittal and coronal spinal deformity
2. May result in long harmonious sagittal curves if multiple osteotomies
are performed over adjacent levels
Disadvantages
1. This osteotomy requires the anterior structures of the spine to be flexible enough to allow the osteotomy gap to completely close posteriorly.
If the anterior disc spaces are narrow or have been previously fused,
anterior surgery including discectomy and/or anterior osteotomy may
be necessary prior to posterior osteotomy. In this situation, a pedicle
subtraction osteotomy may be preferable and allow correction with a
single posterior procedure.
2. Smith-Peterson-type osteotomies performed at spinal segments with
existing foraminal stenosis may worsen foraminal stenosis as the
posterior wedge is closed. Such segments are best avoided as sites for
osteotomy.
3. When multiple Smith-Peterson-type osteotomies are performed, correction may occur preferentially at a single level resulting in less than
complete correction, nonharmonious correction, or a neurologic complication.
4. If a large degree of correction is obtained at a single spinal level, an
anterior column defect may be created because the axis of closure of
the osteotomy is located at the posterior disc margin. Anterior arthrodesis may be indicated to enhance healing of the resultant anterior
gap. Pedicle subtraction osteotomy is an attractive alternative in this
situation, as the axis of rotation for closure of this osteotomy is located
at the anterior aspect of the vertebral body. Pedicle subtraction
osteotomy achieves deformity correction by shortening all three spinal
columns from the posterior approach and avoids creation of an anterior column gap.
Procedure
Planning
1. Location of osteotomies: The location and magnitude of the spinal deformity determines the location of osteotomy or osteotomies. Ideally,
osteotomies are centered over the area of most significant spinal deformity. If the deformity is purely located in the sagittal plane, the
osteotomies should be performed over the most kyphotic segments. If
there is an associated coronal plane deformity, the osteotomies should
be centered around the apex of the scoliotic deformity. The L3-L4 level
is the apex of lumbar lordosis and considered an ideal level for
osteotomy due to its location above the aortic bifurcation and below
the rib cage and conus medullaris.
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222
SECTION III THE LUMBAR SPINE
Eurostile
Line of osteotomy through
= Axis of osteotomy closure
Spinal
nerve
Dural sac
Pedicle
Osteotomy
facet joints
C
B
A
Figure 48–1
(A) The osteotomies are V-shaped with their base located inferiorly in the midline at the original interlaminar space. (B) The lateral extensions of the osteotomy pass proximally across the original facet joints and exit through the neural foramen just proximal to the pedicles. (C) Closure of the posterior osteotomy is accompanied by opening of
the anterior and middle spinal columns.
Eurostile
48 SMITH-PETERSON-TYPE OSTEOTOMY
223
■
A, B
A, B
Figure 48–2
Preoperative standing anteroposterior (AP) (A) and lateral (B) radiographs of a patient with a
sagittal imbalance syndrome following unsuccessful scoliosis surgery.
Pedicle
screws
Osteotomy
outline
Placement of fixation sites
above and below levels
undergoing osteotomy
Remaining osseous
bridge in front of
intervertebral
foramen, spinal
nerve protected
with a dissector
Initiation of
osteotomy
Figure 48–3
Postoperative standing AP (A) and lateral (B) radiographs following
revision surgery. Multilevel anterior discectomy and fusion with nonstructural grafting was followed by multiple-level Smith-Petersontype osteotomies, with restoration of sagittal and coronal plane
alignment and achievement of successful arthrodesis.
Pedicle
screw
Dural sac
Figure 48–4
After the osteotomy sites are outlined, fixation sites are created proximal and dis-
tal to the osteotomies and the osteotomies are initiated.
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224
SECTION III THE LUMBAR SPINE
Eurostile
Spinal nerve
Figure 48–5
The osteotomies are completed and pedicle screws placed at the osteotomized
spinal levels.
A
Screws and rods
prior to
compression
B
C
D
Figure 48–6
(A−D) The osteotomies are closed using a combination of compression forces and table repositioning. Decortication and bone grafting are performed.
Eurostile
48 SMITH-PETERSON-TYPE OSTEOTOMY
225
■
2. Size and number of osteotomies: As an estimate, 1 degree of sagittal
plane correction is achieved by removal of 1 mm of bone at the
osteotomy site. Therefore, if 30 degrees of correction is required in the
sagittal plane, 30 mm of bone must be removed posteriorly. The degree
of correction that can be achieved at one level versus multiple levels
depends on a number of factors including the height of the disc space
as well as the stiffness of anterior column structures. As an estimate, 10
to 15 degrees of correction can be readily achieved per single level
Smith-Peterson-type osteotomy. Many patients with a sagittal imbalance syndrome sufficiently severe to merit surgical treatment require multiple osteotomies. As a guideline for preoperative planning,
the achievement of sagittal balance requires that lumbar lordosis
exceed thoracic kyphosis by 30 degrees following surgery. The use of
preoperative templates to estimate the surgical correction required can
be extremely helpful.
3. Distal extent of fusion and instrumentation—lumbar spine vs. sacrum:
The decision whether or not to fuse to the sacrum is made on a case-bycase basis depending on a variety of factors. Patients with mild deformities (SVA쏝 4 cm), relatively normal disc spaces at L4–5 and L5-S1, and
no symptoms of lumbosacral pain are reasonable candidates for ending
a fusion above the lumbosacral junction. Fusion to the sacrum is indicated for patients with symptomatic degenerative changes involving
the lumbosacral disc or in whom prior fusion procedures involved the
lumbosacral junction. Patients with severe degrees of sagittal imbalance
(SVA 쏜 10 cm) frequently require fusion to the sacropelvis to achieve
and maintain sagittal and coronal balance.
4. Proximal extent of posterior fusion and instrumentation: The relationship of the proximal extent of fusion and instrumentation to the apex of
thoracic kyphosis (T6-T7 disc) should be assessed. If the planned proximal fusion level is within two to three segments of the thoracic apex,
then it is probably advantageous to consider extending the fusion above
the thoracic apex to the upper thoracic spine. This will help to prevent
the development of a junctional kyphosis (proximal transition syndrome).
5. Posterior vs. anterior and posterior surgery: A posterior approach may
be sufficient in cases with mild deformity in whom fusion to the sacrum
is not required. Such patients are generally relatively young with good
bone quality and permit rigid segmental spinal fixation to be achieved.
Combined anterior and posterior surgery is more frequently required in
patients with deformities severe enough to warrant surgical treatment.
Advantages provided by the anterior approach include improved deformity correction, increased rate of fusion, and the opportunity to reconstruct anterior column defects.
Technique of Osteotomy
1. Positioning and operating room (OR) setup: The patient is positioned
on a four-poster frame with supports under the thighs. Extension of the
hips is important, as this will assist in maintaining or increasing lumbar lordosis. When the magnitude of the spinal deformity is severe, the
four-poster frame is positioned with its lower end at the break in the
operating table and the table is flexed to facilitate patient positioning.
The flex is reduced and the table straightened after the osteotomy is
completed to assist in closure of the posterior wedge. Spinal monitoring is used to assess sensory and motor pathways as well as nerve root
function. Wake-up tests are utilized as needed. Controlled hypotensive
anesthesia and a cell saver are used routinely.
2. Exposure: The spine is exposed through the midline posterior approach. Exposure of the spine and previous fusion is from tip of transverse process to tip of transverse process. The transverse processes are
used as landmarks to identify the location of the pedicles and intervertebral foramen when spinal anatomy has been distorted by prior
surgical procedures.
3. Osteotomy outline: The osteotomy site(s) are planned and outlined
with a narrow osteotome. The osteotomies are V-shaped with their
base located inferiorly in the midline at the original interlaminar
space. The lateral extensions of the osteotomy extend proximally
across the original facet joints and exit through the neural foramen just
proximal to the pedicles.
4. Implant placement: Generally, pedicle fixation is used in the sacrum,
lumbar spine, and lower thoracic region. Hook fixation is used to
achieve fixation in a preexisting fusion mass or proximal thoracic spine.
After the spine is exposed, fixation sites are created above and below the
spinal level(s) requiring osteotomy. This sequence helps reduce overall
blood loss during the procedure as bleeding increases significantly after
completion of the osteotomies. Placement of pedicle screws at spinal
levels undergoing osteotomy is simplified if these screws are placed
after the osteotomies are initiated. Performing osteotomies requires
opening the neural canal and permits localization of the pedicles by
direct palpation, which facilitates screw placement.
5. Osteotomy: Bone is removed to initiate the V-shaped osteotomy at each
level. If no prior fusion has been performed, a large double-action
rongeur can be used to remove bone from the midline interlaminar region including portions of adjacent spinous processes (Fig. 48–4). If a
prior fusion mass is present, a trough is created through the outer cortex
and cancellous bone of the fusion mass until the deep cortex is reached.
Then an air drill is used to thin the remaining inner cortical bone to a
thin shell to facilitate its subsequent removal. The spinal canal is then
entered in the midline and the osteotomy is extended in a lateral direction using Kerrison rongeurs (Fig. 48–5). If the ligamentum flavum is
present, it is left intact until the osteotomy is partially completed to reduce blood loss and risk of dural tear. The osteotomy will tend to close
spontaneously,so a lamina spreader is used to hold the osteotomy open
until it can be modified to permit safe closure. It is critical to bevel the
underside of each osteotomywith a Kerrisonrongeur to preventimpingement on the contents of the spinal canal and neural foramen.
6. Osteotomy closure: Spinal implants are used to apply compression
forces across the osteotomies to gradually and equally close the
osteotomy gaps. When all of the osteotomies have been prepared for closure, the OR table can be extended to assist with closing the osteotomies.
During osteotomy closure, the sites are constantly checked to be sure
that each osteotomy closes equally on both sides and that there are no
areas of bone impingement preventing complete closure. After the
osteotomies are closed and the spinal implants are secured, the spine is
decorticated and bone graft is applied (Fig. 48–6).
Technical Tips
1. It is helpful to initiate the osteotomies in a spinal region where anatomy has not been distorted by prior surgical procedures.
2. A distal to proximal progression in performing osteotomies is helpful
as bleeding tends to pool away from the level undergoing osteotomy.
3. In the presence of scoliosis and associated axial plane rotation,
osteotomies are required to be wider on the convex side of the deformity to prevent coronal plane decompensation. When creating this type
of posterior convex-based wedge osteotomy, the osteotomy should first
be completed on the convex side. The concave hinge can be left uncompleted until all the osteotomies have been completed on the convex side and screws have been placed over the osteotomized levels. As
a final step the concave hinges can be completed and final deformity
correction carried out.
Pitfalls
1. Iatrogenic deformity: Obtain a 36-inch PA radiograph on the operating
table prior to wound closure to assess coronal plane alignment and ensure that an iatrogenic deformity has not been created.
2. Insufficient sagittal plane correction: Obtain a lateral radiograph to
confirm that required sagittal plane correction has been achieved prior
to wound closure.
Complications
1. Sagittal or coronal imbalance
2. Pseudarthrosis
3. Neurologic deficit
4. Wound infection
Postoperative Care
1. Expert critical care management
2. Prophylactic antibiotics
3. Nutritional support
4. Mechanical deep vein thrombosis prophylaxis
5. Early mobilization
6. Postoperative TLSO with or without a thigh cuff is considered
Suggested Readings
Bradford DS. Vertebral column resection for the management of rigid
decompensated spinal deformity. Semin Spine Surg 1998;10:381–386.
Bridwell KH. Osteotomies for fixed deformities in the thoracic and lumbar
spine. In: Bridwell KH, DeWald RL, eds. The Textbook of Spinal
Surgery. 2nd ed. Philadelphia: Lippincott-Raven; 1997:821–835.
LaGrone MO. Flat-back syndrome: avoidance and treatment. Semin Spine
Surg 1998;10:328–338.
Lenke LG, Linville DA, Bridwell KH. Sagittal balance considerations in
adults. In: Margulies JY, Aebi M, Farcy JP, eds. Revision Spine Surgery.
St. Louis: CV Mosby; 1999:752–770.
Rawlins BA, Boachie-Adjei O. Revision and salvage deformity surgery.
Semin Spine Surg 1998;10:320–327.
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SECTION III THE LUMBAR SPINE
Eurostile
49
Osteotomy for Ankylosing Spondylitis
Edward D. Simmons
Goals of Surgical Treatment
Osteotomy of the spine in ankylosing spondylitis is done to correct fixed-
rigid deformities of the cervical, thoracic, or lumbar spine that are impairing functional status and quality of life. These deformities are predominantly in the sagittal plane.
Diagnosis
Ankylosing spondylitis is an inflammatory arthritis of the spine presenting
in the early stages with an inflammatory arthritic pain typically involving
the sacroiliac joints initially and then spreading to involve other portions
of the spine. Early on there is normal or very mildly limited range of motion; however, as the disease progresses, a fixed ankylosed spine typically
results. The diagnosis is confirmed with clinical and radiographic evaluation as well as serologic testing. The patients typically have a human
leukocyte antigen (HLA) B27 tissue type.
Indications for Surgery
With ossification of the spine in ankylosing spondylitis, the spine may
eventually fuse in a kyphotic position, and this can involve lumbar,
thoracic, and cervical areas of the spine. In the cervical spine, the flexion
deformity is often a result of a misdiagnosed fracture that went on to heal
in a forward flexed position.
1. Indications for cervical spine osteotomy are for flexion deformity
where there is impairment of the visual field to see ahead and where
patients have difficulty with personal hygiene and function. Difficulty
with swallowing is common. The most severe case of this is the “chin
on chest” deformity.
2. Kyphotic deformity of the thoracic spine in ankylosing spondylitis
does not usually reach proportions that require surgical correction.
Combined anterior and posterior approaches are necessary. The diaphragm must not be violated, as these patients breathe solely with their
diaphragms due to absence of motion through the costovertebral joints.
3. Osteotomy of the lumbar spine is commonly done for lumbar hypolor-
dosis or actual kyphosis giving rise to a fixed flexion deformity.
Contraindications
Contraindications include patients who are not suitable candidates for
medical reasons and where the severity of the deformity does not warrant
the procedure. Severe osteopenia is also a relative contraindication.
Advantages
The technique as described allows for the osteotomy to be done from a
single-stage posterior approach in the lumbar and cervical spines and allows for a high degree of correction to be obtained in a safe manner with the
least morbidity to the patient. The results can be very gratifying in terms of
overall improvement in functional status and quality of life.
Disadvantages
The disadvantages of the procedure predominantly are those related to
potential complications or morbidity from the procedure. Many of these
patients have concomitant medical illnesses and cardiac problems, and
must be carefully evaluated preoperatively from a medical standpoint.
Major neurologic problems are relatively infrequent; however, they can be
a major problem when they occur.
Lumbar Spine Osteotomy
Procedure
The lumbar spine osteotomy is done with the patient in the prone position.
The patient must be carefully positioned on the operating table in a flexed
knee-chest position. The typical table used is an Andrews table. Careful
positioning is also necessary as these patients have fixed ankylosed spines,
and undue pressure in any one particular area must be avoided. The
thoracic chest support must often be elevated considerably to accommodate the patients on the operating table. The procedure is done under spinal cord monitoring. A wake-up test can also be used if necessary. The
osteotomy is done at the L3-L4 level, which is the normal center of lumbar
lordosis. This is also below the conus medullaris, and the spinal canal
volume is fairly reasonable at this level. A preoperative computed tomography (CT) scan should be done to evaluate the spinal canal preoperatively.The apex of the osteotomy is at the L3–4 disc space and the posterior
elements are removed to accomplish the realignment of the spine. The
bone is removed with rongeurs as well as power burs and Kerrisons.
Eurostile
The entire L4 lamina is removed along with a portion of the L3 and L5
laminae with undercutting of the laminae to bevel them so that there is no
impingement upon closure of the osteotomy site (Fig. 49–1A-C). The entire
superior L4 facet is removed and the L3–4 neuroforamina widely exposed
laterally and undercut with medium-angle Kerrisons, again so as to prevent any impingement upon closure of the osteotomy site. The precise
amount of bone removed posteriorly is calculated to arrive at the amount of
correction desired. Upon closure of the osteotomy with osteoclasis of the
spine anteriorly, the lateral masses should meet with good bone surface
contact. The pedicles also must be undercut, removing the superior edge of
the L4 pedicle and inferior edge of the L3 pedicle to again allow adequate
room for the nerve root during the extension correction of the spine.
Pedicle screw instrumentation of the spine is now carried out from L1
to S1. Pedicle screws are inserted in standard fashion, using anatomic and
image-guided techniques as needed. The surface landmarks can often be
obscured due to ossification of the posterior elements of the spine. Pedicle
screws should be inserted in L1, L2, L3, LS, and S1. It is not usually
possible to have screws in L4 as they will impinge upon the L3 screws following extension correction of the spine. Following insertion of the
pedicle screws, the osteoclasis-extension maneuver is carried out (Fig. 49–
1D,E).
The osteoclasis is carried out by extending the foot end of the table,
bringing the hips and thighs up into an extended position. Upon doing so,
pressure can also be applied manually by pushing downward at the L3–4
site, causing a fulcrum for the osteoclasis to occur. An audible and palpable osteoclasis of the spinal column is often present and the lateral
masses will then come together in extension. The lower extremities and
hips are now kept in an extended position, preferably with the knees
flexed, so as to avoid any tension on the sciatic nerve roots.
Rods are now cut and contoured to the appropriate length and shape for
each side of the spine and then fitted down into the pedicle screws and secured. Decortication of the spinal surfaces at the L3–4 osteotomy site is carried out with the power bur or Capener gauge. Autogenous bone graft is
now applied on each side of the spine at the L3–4 osteotomy site, utilizing
autogenous local bone that was removed from the laminectomy and facetectomy procedure. This usually provides ample bone graft without the necessity for procuring any further bone. Cross-link plates can also be applied, adjoining the rods together at each end of the construct.
The wound should be thoroughly irrigated several times throughout the
procedure. A one-eighth-inch Hemovac drain is now inserted and the
wound closed in layers with interrupted sutures. The wound is then
dressed.
Before the patient is transferred from the operating table onto a bed, a
molded plaster shell is made, extending from the base of the occiput down
to the mid-thigh area. The back and posterior thighs are padded with onequarter-inch-thick felt and web roll, and then slabs of plaster applied over
this. After the plaster has had a chance to cure and harden, the patient can
then be transferred onto a bed. The plaster shell support is important in the
early postoperative period so as to give complete support to the spinal
column as the spine is rigid above and below the osteotomy site and any
undue pressure has a long lever arm to act at the osteotomy site and could
potentially cause shifting or disruption of the instrumentation. At our institution, a “roto-rest” postoperative bed is used as this allows for ideal
nursing care and stabilizes the patient well postoperatively.
A nasogastric tube should be in place and left in until there is proven intestinal motility and bowel gas passage. The extension at the osteotomy
site can result in impingement of the superior mesenteric artery on the
duodenum and cause a bowel obstruction. Patients with ankylosing
spondylitis have no or very little neck motion, and if vomiting occurs postoperatively, the patients are unable to clear their airways adequately.
On postoperative day 2 or 3, the patient is fitted with a TLSO brace that
has to be extremely well molded. Alternatively, a body cast can be fitted to
the patient. Following this, the patient is mobilized with physical and occupational therapy. On postoperative day 6 or 7, the patient is usually
ready to go home after appropriate physical and occupational therapy, and
the ability to ambulate well has been demonstrated.
Exposure Secrets
1. Be certain of the level that you are preparing to do the osteotomy at, as
the landmarks are obscured. Radiographic confirmation is often necessary.
49 OSTEOTOMY FOR ANKYLOSING SPONDYLITIS
227
■
Fused spine
V
L1
L2
Wedge
to be
resected
L3
L4
Lines
of
osteotomy
B
A
L5
S1
Transverse
process
intact
isualize
spinal
nerves
C
L1
D
Figure 49–1
(A−E) Schematic diagrams showing areas of posterior resection for L3−4
osteotomy and pedicle screw fixation.
L2
L3
L4
L5
S1
E
■
228
SECTION III THE LUMBAR SPINE
Eurostile
C6
C6
T1
Area of
bone removal
A
on C 7 and T 1
C7
Site after
correction
C6
C7
C7
T1
C8
nerve
root
B
Figure 49–2
(A−C) Schematic diagrams showing areas of bony removal for cervical spine extension osteotomy at C7-T1.
C
T1
Eurostile
49 OSTEOTOMY FOR ANKYLOSING SPONDYLITIS
229
■