Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6030_Библиотеки_им_академика_М_И_Перельмана.pdf
A
B
C
Figure 3–4
A 28-year-old man injured his neck in an industrial accident. He was neurologically intact. At the time of hospital admission he refused halo application. Anteroposterior (AP) open mouth (A) and lateral (B) views show a type II odontoid fracture. Postsurgical AP (C) and lateral (D) views demonstrate the application of two compression screws.
■
20
SECTION I THE CERVICAL SPINE
Eurostile
D
ABC
Figure 3–5
A 19-year-old woman after a motor vehicle accident. (A) Note anterior displacement and posterior angulation at the fracture site. A fracture of this type would have required an anterior buttress plate to avoid iatrogenic anterior displacement of C1 on C2 and subsequent spinal stenosis. (B) This principle was ignored in this fracture,
which was treated elsewhere. Note the resulting severe spinal stenosis. (C) The buttress plate principle for an oblique odontoid fracture.
B
A
Figure 3–6
(A) Screw threads crossing the fracture site, violating the principle of interfragmentary compression. (Courtesy of Aesculap, Inc.) (B) Proper position of the screw threads.
Note the screw threads do not cross the fracture site.
Eurostile
3 ODONTOID FIXATION
21
■
Complications
1. Loss of reduction with screw pull-out
2. Nonunion
3. Malunion
4. Hardware-related complications rare
Postoperative Care
1. Depending on the fracture fixation stability and other patient factors,
place patient in a Philadelphia collar or cervicothoracic orthosis for 6
to 12 weeks.
2. Follow-up x-rays are obtained at 1 week and at 1, 2, and 3 months.
3. Begin gentle range of motion exercises at 6 weeks.
Suggested Readings
Montesano P. Anterior and posterior screw and plate techniques used in
the cervical spine. In: Bridwell K, DeWald R, eds. The Textbook of Spinal Surgery. 2nd ed. Philadelphia: Lippincott-Raven; 1997:1743–1762.
Montesano P. Screw fixation of the odontoid process. Tech Orthop
1994;9:60–67.
Montesano P, Anderson P, Schlehr F, Thalgott J, Lowrey G. Odontoid frac-
tures treated by anterior odontoid screw fixation. Spine 1991;16(suppl
3):S33–S37.
■
22
SECTION I THE CERVICAL SPINE
Eurostile
4
C1-C2 Fusion (Posterior Screw Fixation)
Dieter Grob
Goal of Surgical Treatment
To stabilize and fuse the atlantoaxial segment in its anatomic position.
Diagnosis
Suboccipital pain, headache, and neckache are nonspecific symptoms of
painful changes in the atlantoaxial segment. Neurologic deficit is rarely observed. Functional clinical investigation includes rotation of the head in a
maximally flexed position. In this position, the facets of the lower cervical
spine are blocked against rotation and the remaining rotational motion
must be executed at the atlantoaxial segment.
The diagnosis is often made by normal radiographs. An anteroposterior
open-mouth view reveals changes of the facets and the lateral masses of the
atlas and axis. Lateral view and flexion extension radiographs provide information about the relationship between the occiput, atlas, and axis, and
demonstrate any instability in the transverse plane. More detailed information about bone resorption, size of the pedicles of the axis, and soft tissue
involvement are gained from computed tomography (CT) and magnetic
resonance imaging.
Indications for Surgery
1. Normal atlantoaxial anatomy confirmed in CT scan
2. Nontraumatic (ligamentous) instability of the atlantoaxial segment
(Figs. 4–1 and 4–2)
3. Traumatic instability including fractures of the atlas and axis and liga-
mentous injuries
4. Degenerative changes of C1-C2
5. C1-C2 instability due to loss of bone (tumor, infection)
Contraindications
1. Missing pedicles of the axis
2. Congenital malformations (ill-defined anatomy)
Advantages
1. High fusion rates.
2. Translational and rotational displacement in the C1-C2 segment effec-
tively blocked.
3. Immediate postoperative stability: soft collar sufficient for postopera-
tive management.
Disadvantages
1. Potential risk of injury to the vertebral artery and medulla
2. Technically demanding
Procedure
Positioning
Positioning of the patient is crucial for correctly inserting the screws.
Surgery is performed with the patient in the prone position. Preferably, the
head is separately fixed in a device (halo, Mayfield) that allows unconstrained positioning. Basically, the subaxial cervical spine is axially extended and the atlanto-occipital joint flexed. To achieve this position, the
pivot should come to rest approximately at the level of the external meatus.
The posterior iliac crest is prepared for graft harvesting.
Note:
1. The eyes are taped closed so that they will not be exposed to antiseptic
prepping.
2. Draping and positioning have to take into account the possibility of in-
traoperative use of the C-arm in the lateral position.
Exposure
The skin incision is made strictly in the midline from the occiput to the
mid-cervical spine. The nuchal fascia and the superficial muscles are
divided. By this standard midline approach, the spinous process of the
axis is identified and this serves as a landmark. Exposure of the midline of
the atlas and the C2-C3 facets delineates the operative field. Subperiosteal
dissection, following the border of the spinal canal along the superior
aspect of the lamina, leads to the isthmus of the axis. This structure represents the key to anatomic orientation for screw insertion (Fig. 4–3).
Note:
1. To minimize surgical trauma, the muscular insertion of the short
occipital muscles (rectus major and minor, obliquus capitis inferior)
and of the semispinalis cervicis may be preserved by osteotomizing the
bifid spinous process of the axis.
2. To expose the isthmus of the axis, strict subperiosteal dissection prevents hemorrhage from the epidural and retroarticular venous plexus.
3. By carrying out the subperiosteal dissection anteriorly, the atlantoaxial
joint can be reached and exposed if necessary. The cranial retraction of
the soft tissue surrounding the dorsal nerve root C2 opens the view to
the posterior joint capsule.
Screw Insertion
The screw insertion is executed under lateral radiographic control. Prior to
screw fixation, anatomic realignment (if necessary) is achieved under
visual radiographic control by manipulating a towel clamp fixed to the
spinous process of C2. Drilling and screw insertion is performed in the reduced position. The entry point in the second cervical vertebra for the 2.5mm drill is situated at the lower caudal edge of the area where the joint
meets the lamina. The most lateral part of the medial contour of the isthmus (the lateral border of the spinal canal) serves as the main landmark in
the lateral-medial orientation. The drill ideally passes within the pedicle
of C2, 2 to 3 mm lateral to this bony landmark in a strictly sagittal direction.
The craniocaudal orientation is related to the inclination of the drill,
which is visualized in the C-arm. To achieve a reliable hold in the bone of
the lateral mass of the atlas, the drill should be directed to the upper half of
the oval-shaped projection of the anterior ring of the atlas, thus crossing
the atlantoaxial facet at its posterior aspect (Fig. 4–4). The screws are inserted bilaterally and the construct is completed with a Gallie-type fixation
in the posterior midline between the atlas and the axis using nonabsorbable suture or wire (Fig. 4–5).
Note:
1. Drilling through separate stab incisions allows the incision to be minimized. The position of the stab incision may be determined by the
radiographic projection of a Kirschner wire, held laterally in the
desired position of the drill hole. Specially designed drill guides are
required to protect the soft tissue.
2. Tap drilling allows the resistance at the tip of the drill to be constantly
monitored. It therefore allows control of the intraosseous course of
drilling and the crossing of the facet joint.
3. A strict sagittal direction of drilling is mandatory to avoid injury to the
vertebral artery laterally and violation of the spinal canal medially.
4. If reduction of atlantoaxial dislocation is not possible, the direction of
the drill has to be oriented primarily according to the anatomy of C2 to
place the screw safely.
Pitfalls
1. Beware of anomalies of normal anatomy of the axis and the atlas. Erosion of the isthmus of C2 may not allow the screws to be inserted safely.
2. The screw may pull out if the point of entry in C2 is chosen too superficially.
3. The anatomic structure of the axis may be weak. In the event of screw
malpositioning, a second attempt may be impossible. Switch to conventional fixation techniques.
4. In traumatic or congenital defects of the atlas, the latter may be reconstructed with bone graft and 2.7-mm screws fixing the graft to the remnants of the posterior arch of the atlas.
Complications of Instrumentation
1. Possible damage to the vertebral artery during its course in the isthmus
of C2 or due to too lateral drilling. If this is the case, bone should be removed until the artery can be identified and ligated. If hemorrhage is
from the venous plexus surrounding the vertebral artery, it may be controlled by simple insertion of the screw into the drill hole. If there is
any suspicion of injury to the vertebral artery, it is advisable not to continue with this technique on the contralateral side, but rather to switch
to conventional fusion techniques.
2. In the event of dural leak, the dura should be closed by direct suture or
using fibrin glue.
Postoperative Care
1. Extubation after awakening of the patient. Monitoring of normal ventilation and oxygenation. The flexed position of the head over a long period of time may cause pharyngeal edema and airway obstruction.
Eurostile
4 C1-C2 FUSION (POSTERIOR SCREW FIXATION)
23
■
11 mm
D
C2
axis
A
B
Figure 4–1
Lateral radiograph (A) and illustration (B) of atlantoaxial instability in rheumatoid arthritis. There is a significant dislocation with anterior
atlantodental interval of 11 mm.
C1
atlas
arch
Rectus capitis
posterior major m.
Bifid
(split)
process
Oblique
A
capitis
inferior m.
X
Semi spinalis
cervicis m.
C1
X
C2
B
Figure 4–2
Anteroposterior (A) and lateral (B) radiographs 2 months after atlantoaxial screw
fixation. The screws are crossing bilaterally the facet joints. The posterior bone
graft is fixed with a nonabsorbable suture.
■
24
SECTION I THE CERVICAL SPINE
Eurostile
Figure 4–3
Surgical exposure of the deep muscular layer. The insertion of the muscles at the
spinous process of the axis is detached together with the bony insertion to preserve proprioception. The important landmark is the medial part of the isthmus of
C2, which is dissected subperiosteally (X).
Radiographic
control
Rx
Drill crosses posterior aspect of facets
A
Rx
Lateral view
Posterior view
C
Figure 4–4
(A) The drilling is executed under direct visual control of the operative situs and the lateral image of the C-arm. (B) Direct vision through the surgical approach helps deter-
mine the sagittal direction of the drill, passing 2 to 3 mm laterally of the medial aspect of the isthmus. (C) The radiographic control helps in controlling the inclination. (D)
The ideal projection of the drill should cross the facet in its posterior third and end in the cranial half of the oval projection of the anterior ring of the atlas. (C, D) Ideally
positioned screws in lateral and AP view.
B
D
A
Graft
Figure 4–5
Radiograph (A) and illustration (B) of patient 10 years after atlantoaxial screw fixation with solid bony union posteriorly and screws in place traversing the facets.
Eurostile
4 C1-C2 FUSION (POSTERIOR SCREW FIXATION)
25
Screws
B
■
2. Administration of a soft collar when not in bed for 6 to 8 weeks.
3. Instruction on moving head and neck “en bloc” during this period.
4. Rehabilitation following confirmed fusion of the graft after approximately 6 to 8 weeks.
Suggested Readings
Grob D, Jeanneret B, Aebi M, Markwalder T. Atlantoaxial fusion with trans-
articular screw fixation. J Bone Joint Surg Br 1991;73:972–976.
Madawi AA, Casey AT, Solanki GA, Tuite G, Veres R, Crockard HA. Radio-
logical and anatomical evaluation of the atlantoaxial transarticular
screw fixation technique. J Neurosurg 1997;86:961–968.
Wright NM, Lauryssen C. Vertebral artery injury in C1–2 transarticular
screw fixation: results of a survey of the AANS/CNS section on disorders of the spine and peripheral nerves. J Neurosurg 1998;88:634–
640.
■
26
SECTION I THE CERVICAL SPINE
Eurostile
5
Far Lateral Approach to the Cervical Spine
Christopher J. DeWald
Goals
Decompress the anterolateral cervical spine with complete and safe extensive exposure.
Indications
1. Anterolateral disc herniations
2. Tumors of the cervical spine
3. Nerve compression due to lateral osteophytes
Contraindications
1. Midline or strictly posterior pathology.
2. Vertebral artery disease.
Advantages
1. Exposure of the vertebral artery.
2. Exposure of the neuroforamen.
3. Exposure of the nerve root.
4. The key to this approach is safe identification and exposure of the
vertebral artery. The vertebral artery is much less likely to be injured
during an anterior lateral approach of the cervical spine if it has already been exposed.
Procedure
1. The skin incision is made in the standard transverse fashion.
2. The platysma muscle is split longitudinally or incised in line with the
skin incision.
3. The cervical fascia is sharply dissected medially to the sternocleidomastoid muscle and the medial visceral structures.
4. The pretracheal fascia in then bluntly divided longitudinally along the
carotid sheath separating it from the visceral structures medially.
5. Carotid pulsations are checked to identify the carotid artery and ensure that there is not excessive pressure against the artery during retraction for the exposure.
6. Ipsilateral temporal artery pulsations can also be palpated during exposure to help prevent excessive arterial constriction.
7. The prevertebral fascia is incised longitudinally in the midline of the
vertebrae and the longus coli muscles are stripped laterally off the
anterior aspect of the cervical spine.
8. Carefully, the surgeon continues dissecting the muscles from the
lateral aspect of the cervical vertebrae, its uncovertebral joints, and
onto the transverse processes (Fig. 5–1). The vertebral artery lies just
anterior to the nerve root as the nerve root exits its foramen. Careful
dissection onto the transverse process is required not to injure the
nerve root or vertebral artery by slipping posterior to the transverse
process. Often, when the longus coli muscle is large, it has to be incised transversely a few millimeters directly on top of the transverse
process. Care should be taken not to injure the cervical sympathetic
chain as it lies further lateral in this approach, especially when incising the longus coli muscle in a transverse fashion.
9. Alternatively, the longus coli can be retracted medially once the uncovertebral joints have been safely exposed.
10. The transverse process is exposed from its costotransverse lamella to
the muscular attachment of the anterior tubercle of the transverse
process. The costotransverse lamellae connect the lateral transverse
process to the lateral vertebral body. Posterior to the costotransverse
lamellae lies the vertebral artery foramen. The exposure of the anterior
tubercle is the key to the dissection. The most prominent anterior
tubercle is the Chassaignac tubercle of C6.
11. Once the transverse processes have been exposed to the anterior
tubercle at the level of decompression and at the superior adjacent
vertebral level, the vertebral artery can be exposed above and below
the adjacent transverse processes. If the operating microscope has not
already been utilized during the exposure of the transverse processes,
it is brought into the operating field at this time. Magnification is extremely helpful during the exposure of the vertebral artery and should
be considered an essential part of the dissection. Additionally, the
operating microscope allows visualization for safe retraction by an assistant. A venous plexus surrounds the vertebral artery, and venous
ooze is expected during the exposure. Although brisk, the venous
bleeding is easily distinguished from a vertebral artery laceration and
can be controlled with various hemostatic agents such as Advitene,
Gelfoam, and limited bipolar coagulation. Light pressure is applied
using pledgets or cottonoid pads, but pressure as a means of controlling this venous bleeding can be difficult in this region of the cervical
spine due to the proximity of the vertebral artery and the cervical nerve
roots within their confined foramina. A certain amount of venous ooze
should be tolerated, avoiding overaggressive attempts of stopping all
venous bleeding. If an inadvertent small laceration on the artery occurs, the surgeon can place a small pledget with pressure for a few
minutes. Ligation of the vertebral artery can be considered for larger
lacerations, if the opposite vertebral artery is normal based on preoperative vascular studies such as magnetic resonance angiography
(MRA) or routine angiography.
12. After identifying and obtaining hemostasis of the vertebral foramen adjacent to the exposed transverse processes, the vertebral foramen is unroofed exposing the vertebral artery.
13. A Penfield dissector is used to carefully identify the superior and inferior borders of the costotransverse lamella, and a 1-mm Kerrison
rongeur is used under magnification to carefully unroof the vertebral
foramen, removing piecemeal the costotransverse lamellae. This is
done meticulously, taking time to protect the vertebral artery and to
maintain hemostasis.
14. Once the vertebral foramen is unroofed, the transverse process can be
excised back from the anterior tubercle toward the neuroforamen. The
vertebral artery, no longer tethered within the vertebral foramen, can
tolerate gentle manipulation and can be laterally translated a few millimeters during decompression of the far lateral cervical spine.
15. A small rongeur is used to remove the anterior tubercle and its muscular attachment. This exposes the exiting nerve root directly posterior to
the transverse process, allowing safe removal of the respective transverse process. A Woodson or Penfield dissector can be passed beneath
the remaining transverse process to free up the nerve root from any adhesions.
16. A small Kerrison rongeur is used to continue to remove the bony transverse process to the neuroforamen. The entire lateral aspect of the cervical spine, uncovertebral joints, neuroforamen, and its exiting nerve
root are clearly visualized, allowing complete lateral intervertebral
disc and foramina) decompression (Fig. 5–2). Large uncovertebral
osteophytes can be safely excised within the neuroforamen.
Closure
1. Performed in a standard manner as for an anterior cervical spine procedure.
2. A submuscular drain is more often required than the standard anterior
cervical disc excision due to the additional venous ooze associated
with the exposure of the vertebral artery.
Suggested Readings
Henry AK. Extensive Exposure of the Cervical Spine. Baltimore: Williams
& Wilkins; 1959:53–72.
Hodgson AR. An approach to the cervical spine (C3–7). Clin Orthop
1965;39:129–134.
Louis E, Ruge D. Lateral approach to cervical spine. In: Wiltse LL, Ruge D,
eds. Spinal Disorders. London: Henry Kimpton; 1977:132–136.
Verbiest H. A lateral approach to the cervical spine: technique and indica-
tions. J Neurosurg 1968;28:191–203.
Verbiest H. Anterolateral operations for fractures and dislocations in the
middle and lower parts of the cervical spine. J Bone Joint Surg Am
1969;1:1489–1530.
Verbiest H. The lateral approach to the cervical spine. Clin Neurosurg
1973;20:295–305.
Watkins RG. Surgical Approaches to the Spine. New York: Springer-Verlag;
1983.
Whitecloud TS, Dunsker SB, eds. Anterior Cervical Spine Surgery: Prin-
ciples and Techniques in Spine Surgery. New York: Raven Press; 1993.
Eurostile
5 FAR LATERAL APPROACH TO THE CERVICAL SPINE
27
■
C6
C3
C4
C7
T1
T6
T
E
C7
C6
C7 Spinal nerve root
C6 spinal
nerve root
Vertebral artery
Anterior tubercle,
transverse process
Anterior scalene
muscle
Anterior tubercle of
transverse process and
insertion of anterior
scalene muscle
Vertebral
artery and
spinal nerve
root C6
Figure 5–1
Vertebral artery
retracted
laterally
Anterior
tubercle of
transverse
process removed
(larger portion)
Longus coli and capitis
muscles retracted medially
Vertebral
artery
retracted
laterally
Position of transverse
process removed
C6
C6
Anterolateral view of the lower cervical spine, illustrating the relationship of the vertebral artery to the transverse process, spinal nerves, and adjacent musculature.
Figure 5–2
The vertebral artery is retracted laterally, exposing the exiting nerve
root, intervertebral disc, and foramina.
■
28
SECTION I THE CERVICAL SPINE
Eurostile
6
Anterior Cervical Corpectomy
Eeric Truumees and Harry N. Herkowitz
Goals of Surgical Treatment
To decompress and stabilize an area of stenosis; to correct a segment of cer-
vical kyphosis.
Diagnosis
Most commonly, anterior cervical corpectomy and fusion (ACCF) procedures are performed for spondylotic myelopathy. These procedures,
however, are also indicated to decompress the cord and nerve roots or remove pathologic material in certain cases of ossification of the posterior
longitudinal ligament (OPLL), cervical fracture, tumor, infection, and kyphotic deformity (e.g., postlaminectomy kyphosis).
Due to the high incidence of major abnormalities noted in the radiographic studies of asymptomatic patients, the history and physical examination are ultimately the most important diagnostic modalities. Neurologic involvement is defined by careful physical examination, with particular attention to sensory changes, motor deficits, reflex abnormalities, long
tract signs, and gait and grasp difficulties. Deformity and overall bony architecture are defined by plain radiographs obtained in anteroposterior
and lateral projections. The extent of canal compromise and cord impingement is defined by myelography followed by computed tomography (CTmyelo) or magnetic resonance imaging (MRI) (Figs. 6–1 and 6–2). In all
cases, clinical findings must be consistent with imaging before surgery is
recommended.
Indications for ACCF
1. Trauma: decompression of the canal after burst fractures
2. Tumor: biopsy and excision
3. Infection: biopsy and debridement of osteomyelitis or epidural abscess
4. Deformity: anterior correction and stabilization of kyphosis or decom-
pression at a spondylolisthetic segment
5. OPLL: decompression in some cases of OPLL
6. Multiple, contiguous levels of cervical disc herniation
7. Spondylosis: decompression of osteophytes
Most patients are initially managed nonoperatively. More expeditious
surgical intervention is recommended in patients with severe myelopathy;
rapidly evolving deficits; multiple level radiculopathy, with persistent
disabling pain and weakness (3 months); static deficits with significant
pain; or progressive kyphosis.
Contraindications
There are no specific contraindications to ACCF. Discectomy procedures,
however, should be considered when compression is limited to the disc
level at one to two interspaces. Consider posterior procedures in patients
with:
1. Predominantly posterior compression
2. If lordotic, multiple level (쏜 3) spondylosis or congenital stenosis
3. Anterior bony ankylosis due to degenerative or inflammatory disease
4. Developmental stenosis
5. Prior anterior neck surgery or severe anterior soft tissue injury
6. Continuous OPLL
7. Severe osteoporosis, which increases the possibility of graft collapse
Advantages of ACCF
1. Removal of anterior impinging structures without disturbing the cord
2. Decompression despite cervical kyphosis
3. Segment distraction with foraminal widening and decreased posterior
ligamentum flavum buckling
4. Stabilization allowing resorption of osteophytes and prevention of
further spur formation
Disadvantages
1. Bone graft donor site pain (if autogenous graft is used)
2. Immobilization required
3. Risk of graft dislodgment or pseudarthrosis
4. Risk of injury to soft tissues of anterior neck from direct trauma or long
retraction times
5. Risk of adjacent segment degeneration
6. Technically difficulty
Procedure
Selection of Levels for Vertebrectomy
1. Levels causing clear compression with symptoms attributable to that
level clearly must be included in any planned decompression. This is
usually most obvious in cases of trauma, tumor, or infection.
2. Myelopathy from spondylosis, however, is often not clearly attributable to a given level or set of levels. Further degeneration of adjacent
segments occurs in up to 25 % of patients. Therefore, decompression of
all levels with significant involvement is recommended.
Incision Options
Right- vs. Left-Sided: The recurrent laryngeal nerve, a branch of the vagus,
may be traumatized during the deepest layer of approach. Many surgeons
prefer a left-sided approach because the nerve takes a more predictable
course on this side, descending into the thorax with the carotid sheath,
curving around the aortic arch, and ascending between the trachea and
esophagus to supply the larynx.
On the other hand, a right-sided approach may be easier for a righthanded surgeon. Yet the recurrent laryngeal nerve descends with the
carotid sheath and curves around the subclavian artery to ascend into the
neck at a higher level than on the left. Further, there is a higher rate of aberrant courses for the nerve on this side, with early departures from the
sheath to cross the operative field at the level of the thyroid gland.
Transverse vs. Longitudinal: A transverse incision is usually planned for
one- or two-level corpectomies. Here, the skin incision is placed in a crease
and extends obliquely from midline to the middle of the sternocleidomastoid (SCM). Although exposure for longer decompressions may be obtained through a transverse incision, the additional retraction may well increase postoperative swallowing and breathing difficulties. Also, although
cosmetically more appealing, this approach is not extensile.
1. If more than two levels will be decompressed or if the upper level of
decompression is higher than C4, a longitudinal incision along the
anterior border of the SCM is used.
2. Localize the approach to the level of pathology via external landmarks
(Table 6–1, Fig. 6–3).
Approach
1. With either incision, a standard anterolateral approach (Smith-Robinson), offering direct exposure of the anterior bodies, disc spaces, and
uncinate processes from C3 to T1, is undertaken (Fig. 6–4).
2. Directly beneath the skin lies the platysma, which may be divided
longitudinally (in line with its fibers) with the tips of the index fingers.
Alternately, the platysma may be divided, without functional consequence, in line with a transverse incision using a Kelly to bluntly
elevate it from the deep cervical fascia.
3. The deep cervical fascia is next identified as an investing layer that
splits around the SCM. It is superficial to all of the structures of the
neck except the platysma and external jugular vein.
4. The anterior border of the SCM is identified and the fascia is incised
longitudinally immediately anterior to the muscle.
5. The SCM may now be gently laterally retracted. Simultaneously, retract the sternohyoid, sternothyroid, trachea, and esophagus medially
with baby Richardson retractors. This maneuver will expose the
carotid sheath (containing the common carotid artery and vein with
the vagus nerve).
6. Next, a plane is developed between the medial edge of carotid sheath
and midline structures by incising the pretracheal fascia (which is continuous with the carotid sheath at its lateral margin and invests the
strap muscles medially).
Table 6−1. External Landmarks
Hard palate Arch of atlas
Lower border of mandible C2–3
Hyoid C3
Thyroid cartilage C4–5
Cricoid cartilage C6
Carotid tubercle (anterior transverse process) C6
Eurostile
6 ANTERIOR CERVICAL CORPECTOMY
29
■