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target vertebra.3 Skin hooks are used to lift the incised edges, and the dermal
and subcutaneous fat layers are then cut using electrocautery to reach the
platysma. Skin flaps are created using Metzenbaum scissors. The platysma is
divided in line with the skin incision, and a plane is then developed deep to
the platysma, which helps define the medial border of the
sternocleidomastoid muscle. The investing fascial layer is separated and then
incised using scissors. The carotid artery is palpated, and an appendiceal
retractor is placed medially to retract the trachea and the esophagus. The
prevertebral fascia is thinned using two peanut dissectors on the anterior
vertebral surface. A spinal needle is placed in the disk space, and a lateral
radiograph is obtained to confirm the level. The medial surface of the longus
colli is exposed, and a portion of the muscle corresponding to the target disk
space is elevated using bipolar cautery. Horner syndrome is a rare
complication that occurs secondary to a sympathetic plexus injury and can be
avoided by keeping the dissection medial to the longus colli muscle.4 A
Caspar retractor is used for craniocaudal distraction of the disk space.
Complications
Complications related to the anteromedial surgical exposure include
dysphagia, dysphonia (damage to the recurrent laryngeal nerve or the
superior laryngeal nerve), hematoma, esophageal damage, Horner syndrome,
and vascular injury.
5,6
Anterior Exposure of the Upper Cervical Spine
The anterior exposure of the upper cervical spine (C1-C3) can be performed
using the transoral approach or the anterior retropharyngeal approach.
Transoral Approach
The transoral approach provides direct access to C1 and C2.7 The procedure
is performed with the patient supine and his or her arms tucked at the sides.
The elbows should be well padded. The table is placed in the Trendelenburg
position to avoid aspiration of surgical debris. Endotracheal intubation is
preferred over nasal intubation because the endotracheal tube can be easily
moved laterally away from the operating field. Maintaining balloon integrity
of the endotracheal tube is crucial. A self-retaining rectangular retractor that
allows depression of the tongue and retraction of the uvula superiorly is used.
Superiorly, the C1 anterior tubercle is palpated, and the level is confirmed
fluoroscopically before an incision is made. A No. 10 blade is used to make
an incision on the pharynx vertically, and the entire soft-tissue layer then is
stripped off subperiosteally, including the anterior longitudinal ligament,
until the lateral masses of C1 and C2 are evident. After the procedure has
been completed, watertight closure of the soft tissues is performed in two
layers.
Complications associated with the transoral approach include infection,
aspiration, breakage of teeth, and laceration of the tongue or other soft-tissue
structures.
7
Anterior Retropharyngeal Approach
The anterior retropharyngeal approach, which provides access from the
occiput to C3, is entirely extramucosal and confers less risk of wound
infection. This approach also allows placement of bone graft, if required.
8-
11
The procedure is performed with the patient supine with skeletal traction or
chin strap traction. The skin incision extends from the mastoid process to the
hyoid bone in the midline. Because the encountered neurovascular structures
are symmetric, the side of the approach depends on surgeon preference and
pathology. The platysma is identified and incised along the line of the skin
incision. Deep to the platysma muscle, the parotid and submandibular glands
are located. At this stage of the procedure, it is important to identify three
important neurovascular structures—the marginal mandibular nerve, deep to
the parotid gland; the retromandibular vein, at the middle portion of the
parotid; and the common facial vein, at the angle of the jaw.8 Both veins are
ligated at their junctions with the internal jugular vein, and the dissection is
deepened to define the medial border of the sternocleidomastoid. The
submandibular gland is excised, and its duct is ligated to prevent fistula
formation. The stylohyoid and the digastric muscles are identified and tagged
and then detached from the hyoid bone, which helps in lateral retraction of
the hyoid and the trachea/larynx. Care should be taken to avoid damage to the
hypoglossal nerve, which lies deep to the detached muscles. The dissection is
further deepened in the plane between the carotid sheath laterally and the
esophagus/larynx medially. The following seven critical structures are
identified and ligated in a cranial to caudal direction: the facial artery and
Figure 1
vein, the ascending pharyngeal artery and vein, the superior laryngeal artery,
and the superior thyroid artery and vein.
9,10
Peanut dissectors are used to thin
the prevertebral fascia between the longus colli muscles. After performing the
required procedures, the wound is closed over a drain and the digastric and
stylohyoid tendons are repaired.
Possible complications of the anterior retropharyngeal approach include
injury to the esophagus, hypopharynx, or the neurovascular structures
previously mentioned.
The angle of the craniocervical junction is made by drawing
a line along the hard palate posteriorly to C2 and then
placing a line along the posterior wall of C2. The mean measurement
for this angle is approximately 100°. (Reproduced with permission
from Takami T, Ichinose T, Ishibashi K, Goto T, Tsuyuguchi N, Ohata
K: Importance of fixation angle in posterior instrumented
occipitocervical fusion. Neurol Med Chir (Tokyo) 2008;48[6]:279-282.)
Posterior Occipitocervical Approach
The proximity of the vertebral arteries and the complex upper cervical
vertebral anatomy make the posterior occipitocervical approach more
challenging than most posterior approaches. This approach facilitates occiput
to cervical and C1-C2 reconstruction procedures and is most commonly
indicated for conditions such as trauma, rheumatoid arthritis, infections, and
tumors.
12-14
Surgical Steps
If there is no ligamentous distraction injury, Gardner-Wells tongs can be
applied for traction. Some surgeons prefer to use the Mayfield head holder,
whereas other surgeons prefer a moveable head holder that is available on
Jackson frames or similar tables. Care should be taken to prevent fusion of
the occipitocervical junction in a flexed or extended position because
dysphagia, subaxial subluxation, and airway compromise can result. To
assess the occipitocervical junction, the angle of the craniovertebral cervical
junction provides a simple and reliable measurement (Figure 1). The mean
angle of the craniovertebral cervical junction is 99°± 8°.
15
The patient is turned prone on a frame with proper care and padding to
avoid pressure on the eyes, face, and abdomen. The palpable landmarks,
including the occipital protuberance and the C2 and C7 spinous process, are
marked, and the correct level is confirmed under fluoroscopy. A midline
incision is made extending from the occipital protuberance to the spinous
process of C3. The superficial dissection is performed strictly in the midline
to reach the ligamentum nuchae. To minimize bleeding, the ligamentum
nuchae is split in the midline. The rectus capitis and oblique capitis are
subperiosteally elevated from the spinous process and the lamina of C2, and
attention is then turned to the occipital bone where subperiosteal dissection is
performed from the midline along the inferior nuchal line. Exposure is
maintained with right-angle cerebellar or Gelpi retractors proximally and
distally.
The posterior tubercle of C1 is identified and subperiosteal exposure on
both sides of the midline is performed using curets. The vertebral artery runs
along the cranial surface of the lateral third of the posterior arch. To avoid
injury to the vertebral vessels, it is necessary to stay 1 cm or less away from
the midline as the superior aspect of the C1 arch is exposed.14 In some
complex clinical situations involving tumors, difficult anatomy, or C1 pedicle
analog screw insertion, it may be necessary to expose the C1 arch more
laterally. A study using CT angiography suggests that the vertebral artery
intersects the outer cortex of the vertebral artery groove approximately 18
mm from the midline.16 Preoperative CT angiography can help the surgeon
plan for a safe amount of exposure for an individual patient. Meticulous
surgical technique and avoidance of Bovie electrocautery and burring on the
superior arch of C1 also are recommended. The exposure of the C1 lateral
mass involves mobilizing the C2 dorsal nerve root caudally. Because this
root, which lies at the junction of the posterior C1 arch and the lateral mass,
is surrounded by an abundant perineural venous plexus, bleeding can make
dissection in this area challenging. Bleeding usually can be controlled with
the placement of small pieces of a gelatin sponge soaked with fibrin or slurry
(made of gelatin powder and thrombin) along with a small cottonoid until
bleeding stops; electrocautery usually is not as successful. In difficult cases,
the C2 nerve root can be transected to dramatically improve visualization of
the starting point on the C1 lateral mass, improve hemostasis, and allow
formal débridement and packing of the C1-C2 articulation for arthrodesis
17
(Figure 2). Interestingly, not all patients report numbness after C2
transection. Without root transection, C2 neuralgia can occur after placement
of C1 lateral mass screws in as many as 30% of cases. Alternatively, some
surgeons use C1 pedicle screws with a starting point that lies on the posterior
arch to avoid bleeding around and irritation of the greater occipital nerve that
can result from lateral mass screw placement. Even more care and
understanding of the proximity of the vertebral artery in relationship to the
screw’s starting point and trajectory is required.
16
Figure 2
Schematic drawing depicting the posterior exposure of C1-
C2. Note the position of the greater occipital nerve as it
pierces the C1-C2 membrane and courses laterally and superiorly.
Exposure of the C1-C2 articulation for bone grafting generally requires
retraction or sectioning of this nerve. Note the position of the vertebral
artery lateral to the C1-C2 articulation. Generally, the exposure does
not need to be developed lateral to the lateral edge of the C2 lamina
because this marks the lateral edge of the C1-C2 joint, and further
lateral exposure puts the vertebral artery at risk.
Posterior Subaxial Cervical Approach in Laminoplasty and
Laminectomy
The posterior approach to the subaxial cervical spine is commonly used in
procedures such as laminectomy, laminoplasty, and lateral mass fixation. The
patient is placed prone for the performance of laminoplasty or laminectomy.
The patient’s head is placed in tongs or a selected head holder is used. For
patients with substantial cord compression, a slight flexion alignment is
initially preferred. If fusion is to be performed, it is important to restore
lordosis after decompression but before final implant tightening. The
patient’s arms are tucked to the sides of his or her body and wrapped in a
sheet. Placing the knees in slight flexion can limit patient movement on the
table.
Surgical Steps
The spinous processes of C2 and C7 are marked, and correct levels are
identified using fluoroscopy. The skin and subcutaneous tissue can be
infiltrated with a 1:500,000 epinephrine solution to help with hemostasis. The
skin is incised in the midline corresponding to the levels of surgery. The
dissection is then deepened, keeping strictly within the median raphe to avoid
bleeding and muscle damage. After the spinous process is reached, further
dissection is performed subperiosteally from distal to proximal using
electrocautery; self-retaining retractors are then placed bilaterally. The lateral
limit of dissection is the lateral edge of the lateral mass. Depending on the
pathology treated, a laminectomy is performed in a piecemeal or en bloc
fashion.
Specific Instructions: Laminoplasty
When performing a laminoplasty, patient positioning, skin incision, and
lamina exposure are like those of the conventional posterior approach, but
care should be taken to preserve the C2 and C7 attachments.
18,19
The muscles
attached to the C2 spinous process are the rectus major, inferior oblique, and
semispinalis cervicis muscles. Preservation of the C2 and C7 muscle
attachments theoretically reduces loss of lordosis and neck pain caused by
mechanical instability after laminoplasty.18 Technical goals of foraminotomy
are similar to the goals of other posterior surgeries performed without fusion
and include preservation of the joint capsules and avoidance of extensive
facet resection.
Posterior Minimally Invasive Foraminotomy
The minimally invasive approach to the cervical spine has been shown to
reduce the length of hospital stays and postoperative pain medication
requirements. This approach is mainly useful in treating radiculopathy
secondary to lateral disk herniation without instability and kyphotic
deformity.
20-22
Patient Position
A minimally invasive procedure can be performed with the patient prone or
seated. A prone position with a slight reverse Trendelenburg position can
reduce bleeding. The patient’s arms are tucked to his or her sides and the
shoulders are taped, which facilitates imaging when the procedure involves
the lower cervical spine. When small incisions are planned, fluoroscopy is
relatively more important for identification and confirmation of the target
level before the incision is made.
Surgical Steps
A 3-cm midline skin incision is placed with the target disk level as the center.
The superficial dissection is continued through the midline until the cervical
fascia is encountered, which is divided longitudinally in the midline to
expose the tips of the spinous process. Further dissection is performed
subperiosteally elevating the paraspinal musculature from the lamina, spinous
process, and facet joint using a Cobb elevator and electrocautery. At this
stage, a self-retaining or handheld retractor is placed to reflect paraspinal
muscles from the target interlaminar area. Decompression is performed under
loupe or microscope magnification. A high-speed burr is used to remove the
caudal edge of the upper lamina and the medial third of the facet. This
resection may be completed with a small Kerrison rongeur, but no more than
half of the facet should be resected. Next, the medial and cephalad portion of
the caudal pedicle are located.23 The root is typically mobilized in a cephalad
direction; however, if root tension limits mobility, a small portion of the
pedicle can be resected with a burr to facilitate exposure of the disk.
Microscope magnification and protection of the nerve root with a small
Penfield retractor is suggested. Bleeding from the perineural venous plexus
can usually be controlled with hemostatic agents and cottonoid packing.
Figure 3
Schematic drawing depicting the cross-sectional anatomy
as seen in the posterior transpedicular approach for
exposure of the anterior column from a posterior incision. The shaded
region of the lamina, facet region, pedicle, and vertebral body can be
completely resected if a tumor or infection is present. The bilateral
exposure allows for complete corpectomy, if needed.
Circumferential Decompression of the Thoracic Spine Via a
Posterolateral Transpedicular Approach
The posterolateral transpedicular approach is a single-stage approach used to
reach the anterior and posterior aspect of the thoracic vertebral body (Figure
3). This approach is indicated in the treatment of tumors, infections, spine
fractures, and spine dislocations.
24-27
Surgical Steps
The procedure is performed with the patient under general anesthesia and
positioned prone on a Wilson or Jackson frame. Intraoperative fluoroscopy or
plain radiography is used to locate the intended surgical level. A posterior
vertical midline incision is made, and the thoracolumbar fascia is divided in
the midline.
25,26
The paraspinal muscles are dissected using electrocautery
and Cobb elevators. The muscles can then be retracted using self-retaining
retractors. Total laminectomies of the affected levels are performed using a
high-speed burr or Kerrison rongeurs. Next, complete facetectomy and
pedicle resection are performed bilaterally. After the posterolateral
decompression is completed, the disks corresponding to the upper and lower
corpectomy levels are removed. The corpectomy is performed using curets,
rongeurs, and osteotomes from the posterolateral corner through a
transpedicular approach. The exiting nerve root often is transected to improve
exposure; however, the T12 and T1 roots should be preserved whenever
possible because of the potential for more important radicular sequelae. The
posterior longitudinal ligament can be resected if needed, and the
completeness of the corpectomy can be judged by direct visualization of the
anterior longitudinal ligament. Care should be taken to preserve the bony end
plates at the upper and lower levels of the corpectomy to avoid subsidence
and enhance graft incorporation.
26,27
Preserving a thin bone wafer anteriorly
may reduce the incidence of graft migration and provide another layer of
protection between the instrumentation and the aorta.
Advantages
The advantages of the posterolateral transpedicular approach include
circumferential decompression of the spinal cord and stabilization through a
single skin incision. This approach obviates the need for single-lung
ventilation and the lateral decubitus positioning required for standard anterior
thoracic approaches.
25-27
This approach can sometimes be performed without
the need for a postoperative chest tube if the pleural space is not entered.
Minimally Invasive Thoracotomy
Minimally invasive thoracotomy uses a smaller incision and generally
smaller retractors compared with traditional open transthoracic exposures.
Generally, a 5- to 6-cm skin incision is used to reach the anterior and lateral
surface of the T5-T10 vertebral bodies.
28-30
This approach is indicated for
thoracic disk herniations, infections, fractures, dislocations, and tumors.
Surgical Steps
Minimally invasive thoracotomy is performed with the patient placed in the
right lateral decubitus position and under general anesthesia. Because this
procedure requires single-lung ventilation, a double-lumen endotracheal tube
is used. The intended spinal level is identified by counting the ribs and is
confirmed with fluoroscopy. A 4- to 6-cm skin incision is made parallel to
the rib. The serratus anterior muscle is separated along the direction of its
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