techniques, methods, indications and complications of various fusion techniques for subaxial cervical spine. comparison of anterior versus posterior techniques, their indications and complication.

1. Fusion techniques in Subaxial cervical spine
Presented By:
Dr. Rahul Jain
SR-2 Neurosurgery
Moderated by:
Dr V. C. Jha
Dr Nitish Kumar
Dr Gaurav Verma

2. Anatomy
• more conventional spinal motion segments compared to
C1 and C2
• Superior articulating facets transition from a posteromedial
orientation at C3 to a posterolateral orientation at C7.
• Uncovertebral (Luschka) joints in which the lateral aspects
of the vertebral body superior end plates project upward
as uncinate processes articulating with the unci of the
inferior end plates above, serving to restrain lateral motion

4. Surgical Planning
• Core principles of spine surgery—
• decompression of the neural elements,
• restoration of normal alignment,
• stabilization of pathologic segments, and
• prevention of further deformity
• Factors such as anterior versus posterior approach,
number of levels, the need for fusion, consideration of
cervical disk arthroplasty (CDA), type of grafting
material, and implant design must all be considered
when developing a surgical strategy.
• In addition, the cost-effectiveness of not only implants
but also the type of procedure itself must be weighed
into the surgical design.

5. Anterior v/s Posterior
• Anterior approach works well for a central and
posterolateral disk herniation resulting in spinal
cord compression.
• Posterior approaches often result in indirect
decompression of the spinal cord that can shift
away from anterior pathology, whereas an anterior
approach addresses the pathology directly.
• Risks unique to anterior approach are dysphagia,
hoarseness, vocal cord paralysis, anterior vascular
injury, injury to trachea or esophagus.

6. • Anterior approach is best suited to
address pathology when cervical kyphosis
is present, for restoration of lordosis and
improved sagittal balance.
• Historically more than three levels of
disease were considered a good
indication for posterior approach but
recently there has been increased
interest in three or even four level ACDF.
• In general a simple discectomy is
indicated when the disease is confined to
disk space but when there’s significant
disease posterior to vertebral body then
a corpectomy should be considered.

7. Anterior fixation techniques
• In 1955, Robinson and Smith – 1st attempt for anterior
approach - operation for ventral removal of cervical
disk material and replacement with a rectangular bone
graft obtained from the iliac crest.
• In 1958, Cloward described his technique, in which a
discectomy was performed and a cylindrical bone
dowel was inserted.
• in 1964 first reported use of screw-plate fixation in the
anterior cervical spine by Bohler and Gaudernak.
• In 1982, Caspar described a novel technique and
instrumentation system (retractors, distractors, and
screw plates) that popularized the practice of anterior
cervical plate application.

8. Indications
• Degenerative, neoplastic, infectious or inflammatory,
traumatic, and iatrogenic (postsurgical) causes of
vertebral column instability, with or without
concomitant neural compression.
• The two most widely accepted clinical indications for
anterior approaches to the cervical spine are
myelopathy and medically-refractory radiculopathy.
• Whereas structural compromise from discitis or
osteomyelitis and trauma can also necessitate
operative intervention, axial neck pain and cervicogenic
headache with or without kyphotic deformity are not
widely accepted indications for surgery.

10. Technique
The superior border of the thyroid
cartilage can be used to plan an
exposure of C3‒C4, whereas an
incision based in a skin crease near
the inferior border will allow access
to C4‒C5 and C5‒C6. C6‒C7 about 2
fingerbreadths above the clavicle.

12. Discectomy Versus Corpectomy
• When circumstances permit, multilevel discectomies
are superior to corpectomies.
• When possible, generous discectomies are
substituted for a corpectomy if adequate neural
decompression can be achieved through wide and
deep undercutting of the offending posterior
vertebral body surfaces.
• The benefits of avoiding a complete corpectomy
include preserving additional sites for screw fixation
along the plate and circumventing the higher risk of
non-union or hardware failure that accompanies
fusion constructs involving multiple corpectomy
segments.

13. • The primary indications of
corpectomy over discectomy are:
(1) loss of structural integrity of the
vertebral body (anterior column
failure); and
(2) canal compromise behind the
vertebral body, not accessible
through the disc space
• End plate contouring above and
below the decompression zone can
be performed either after
discectomy or after corpectomy
but should be completed before
PLL removal.
• Options for cervical interbodies
include the use of ICBG, structural
allograft, titanium cages, or
polyetheretherketone (PEEK).

14. Multisegment disease with loss of cervical
lordosis
Restoration of lordosis is
made possible by paying
careful attention to
divergent distracting pins,
removing anterior and
posterior osteophytes,
performing wide
discectomies involving
uncovertebral joints, and
sequentially lagging the
vertebrae into the plate
with long screws.

15. Skip Corpectomy
• C4–C6 corpectomy with preservation of the C5
vertebral body to treat C3–C7 developmental stenosis.
• This technique was developed in response to the
relatively high failure rates seen with multilevel
anterior cervical corpectomy and fusion.
• Skip corpectomy allows for more graft–bone contacts
points versus standard corpectomy (four vs. two) and
more points of screw fixation during plating (six vs.
four).
• Skip corpectomy has also found a niche in cases of
OPLL.

16. A–C, there is
evidence of chronic
spinal cord
compression
D–F demonstrate
satisfactory
radiographic
decompression of the
spinal cord after C4
and C6 corpectomy
and preservation of
C5 ,with improvement
in global cervical
alignment

17. ANTERIOR CONTROLLABLE
ANTEDISPLACEMENT FUSION
• method in treating OPLL, Yang and colleagues described the
anterior controllable antedisplacement fusion (ACAF)
method in 2018.
• Expose the anterior vertebral bodies and intervertebral
discs spanning the vertical length of the OPLL.
• Discectomies are performed above and below the OPLL, and
a partial corpectomy is completed, leaving approximately
50% of the vertebral body intact.
• Vertical troughs are drilled medial to the transverse foramen
and lateral to the OPLL down to the dura. An anterior plate
is affixed to the vertebral bodies above and below the OPLL.
• Finally, screws are placed into the remnant vertebral bodies
spanning the OPLL in an effort to pull the vertebral bodies
and OPLL anteriorly towards the plate.
• Fusions are then performed at the levels of
discectomy/corpectomy.

18. • The goal of this procedure is to increase the anterior-
posterior diameter of the spinal canal and avoid
potential complications of CSF leak by displacing the
remnant vertebral bodies and OPLL en bloc as done in
less preferred floating method.
• Yang and colleagues compared their results of ACAF
versus ACCF for OPLL and found slightly better mJOA
scores at 6 months (15.4 vs. 14.5). Overall
postoperative complication rate in the ACAF group was
significantly lower compared with the ACCF group.
• Authors reported significantly lower CSF leak rates in
the ACAF versus ACCF (3.6% vs. 22.6%, respectively).

20. • Contraindications to an anterior-only approach in
traumatic sine injury or degenerative disease
include
1. posterior lesions, which compromise the spinal
cord or nerve roots and need to be addressed,
2. clinically significant posterior dural leaks,
3. locked facet joints that are irreducible by traction
or anterior open surgery, especially in instances
where surgery is delayed

21. Posterior fixation techniques
• 1891 when Berthold E. Hadra wrapped loops of
silver wire around the spinous processes of the
cervical spine for stabilization.
• 1911 Hibbs’ method of spinal fusion surgery: solid
bony arthrodesis by stripping the periosteum from
spinous processes.
• Goal of posterior cervical spine instrumentation is
to restore anatomic alignment, provide immediate
stability, pro-mote fusion, prevent neurological
compromise, and allow early mobilization of the
patient.

22. • Cervical instability is the primary indication for
posterior instrumentation of the subaxial cervical
spine; defined as loss of the ability of the spine to
maintain its displacement pattern and to prevent
increased deformity or neurological deficit under
physiologic loading.
• Injury to or destruction of the bony structures or
ligaments may induce instability.
• In general, the anterior and middle columns must
be capable of weight bearing for posterior
instrumentation to be used alone; an anterior or
combined anterior-posterior approach may be
needed if this is not the case.
• Trauma, degenerative disease, deformity,
congenital anomalies, neoplasm, infection, or
inflammatory conditions.

23. TECHNIQUES
• Bony posterior elements that are available to anchor
instrumentation include the spinous processes,
laminae, facets, and lateral masses.
• The pedicles are also available for instrumentation,
although the small diameters of the C3, C4, and C5
pedicles frequently preclude safe screw placement.
• The individual patient’s disease process, the suitability
of the bony structures to accept instrumentation, the
biomechanics of each construct, and the surgeon’s
experience should be considered when the method of
instrumentation is selected.

24. Interspinous Wiring
• Technically simple to perform and generally safe,
with minimal risk to the neural elements
• Historically has played a major role in stabilizing the
cervical spine.
• Although wiring restores the posterior tension
band construct, it does not stabilize against
extension, rotation, or lateral bending.
• Since the introduction of fusion and
instrumentation with plates and screws, it has very
limited role usually functioning as a salvage
procedure or as an adjunct to other fixation
constructs.

25. Indications
• Requires that the
posterior bony ring is
preserved (i.e., lamina,
facet, or spinous
process).
• As it stabilizes flexion
motion, it can be utilized
in a flexion-distraction
injury with facet
subluxation or
dislocation.
• Augment anterior
cervical instrumentation.
• Pathology involving just
one cervical level

26. Contraindications and limitations
• Any traumatic or pathologic process that compromises
the integrity of the posterior bony elements is a
contraindication.
• Tension band wiring is at risk for failing in osteoporotic
bone.
• In general, stand-alone posterior fixation is relatively
contraindicated when there is instability of the anterior
or middle column.
• wiring only offers resistance against flexion, so
additional fixation technique(s) must be employed to
provide extension, rotation, and lateral bending
stability.

27. Bohlman Interspinous Wiring Technique
Rogers Interspinous Wiring Technique

28. Laminar screw fixation
• Traditionally performed in the atlantoaxial and
thoracolumbar spine.
• in the subaxial spine remains an uncommon
practice.
• The feasibility of translaminar screw placement at
C7 is primarily due to its larger laminar size.
Clinically, laminar screw fixation has had promising
results with low complication rates; the main
complication reported was dorsal laminar breach.
• Requires intact posterior elements, specifically
intact laminae, at the levels to be instrumented.

29. Lateral mass screw fixation
• mainstay technique to achieve posterior fixation of the
subaxial spine.
• First in 1964 by Roy-Camille and later modified by Louis,
Magerl, Anderson, Ebraheim.
• Anatomically, the lateral mass, or articular mass, consists of
the superior and inferior articular facets. The lateral mass
lies anterolateral to the lamina.
• Lateral mass screws ranging in diameter from 2.7 to 4.5 mm
may be used. Screws smaller than 3.2 mm in diameter or
larger than 4.5 mm in diameter have lower pullout
resistance than do screws with diameters within this range.
• Screw length may be 10 to 16 mm; 14-mm screws achieve
bicortical purchase in approximately 92% of lateral masses,
as reported by Sekhon

30. Entry point is identified in the
center of the exposed dorsal
surface of the lateral mass.
trajectory that aims for the
ventrolateral corner of the lateral
mass

31. • Fusions supplemented with lateral mass screws and
rods or plates are associated with an overall fusion rate
of 80% to 97%.
• Failure of lateral mass screw–based instrumentation
occurs most commonly at the bone-screw interface.
Pullout resistance is highest at C4, with strength
decreasing about 30% at C7 because of anatomic
variability of the lateral masses.
• Disadvantages
1. including potential nerve root and vertebral artery
injuries.
2. Furthermore, this technique cannot correct kyphotic
deformities, significant translation, or subluxation,
3. Adequate spinal alignment must be achieved before
instrumentation.

32. Transpedicular Screws
• Not routinely used in the cervical spine because they
are technically difficult to place due to small pedicle
diameter and high medial angulation.
• Pedicles get smaller caudal to C2, reaching a nadir
around C3-C4, and 75% of C3-C4 pedicles have an
average diameter less than 4 mm.
• Furthermore, the lateral wall is the thinnest structure in
the pedicle making screw perforation into the vertebral
artery a significant risk.
• The medial angulation of pedicles increases in the
subaxial cervical spine. Therefore, in order to match the
pedicle trajectory, a far lateral exposure is required.

33. Indications
• Certain trauma cases, spondyloarthropathies,
osteoporosis, metastatic disease, and revision
surgery, the posterior elements may be
comminuted or deficient, such that lateral mass
fixation is not possible and this is where pedicle
screws can be useful.
• relative indication for its use is posterior correction
of kyphosis and deformity, for which transpedicular
screws offer enhanced biomechanical stability and
resistance to pullout.

34. Technique
• The starting point is 1 mm
lateral to the center of the
articular mass, near the
cranial end of the superior
articular process.
• high-speed burr is used to
decorticate the starting
point to expose the pedicle
canal. A small pedicle probe
is then inserted into the
canal. The pedicle is tapped
under fluoroscopic guidance
• suggested trajectory is 25 to
45 degrees medially in the
axial plane and parallel to
the superior end plate in the
sagittal plane.

35. • Technically less demanding
at C7 than in other subaxial
cervical vertebrae because
the C7 pedicles have a
larger mean diameter (5.4
to 9.1 mm) and are
relatively remote from the
vertebral arteries.
• A lateral pedicle
perforation would lead to
violation of the transverse
foramen with potential
vertebral artery injury.
• medial perforation would
violate the spinal canal and
risk dural tear or spinal
cord injury

36. • Five studies in the literature have analyzed
complications from pedicle screw fixation in the
subaxial cervical spine.
• rates of screw perforation ranged from 6.7% to
30%, and most cases breached the lateral wall
• Despite the relatively high rate of pedicle
perforation with screw placement, the incidence of
neurovascular injury is relatively low. Out of the
350 patients across the five studies, only two
patients had a vertebral artery injury, five patients
had a nerve root injury, and zero patients had a
spinal cord injury.
• high incidence of pedicle perforation, yet the low
incidence of neurovascular injury, can be explained
on an anatomic basis.

37. • vertebral artery occupies only 35% of its foramen
and distance from the vertebral artery to the lateral
pedicle wall increases from C2 to C7.
• In the cervical spine, nerves occupy the inferior half
of the neural foramen, lie nearly opposed to the
superior part of the caudal pedicle and lie 1.1–1.7
mm from the inferior aspect of the cranial pedicle -
Therefore, a superiorly placed pedicle screw is
more likely to cause nerve damage.
• The medial wall of the pedicle is thickest and the
dural sac is 2.4–3.1 mm away.

38. 360 degree fixation
• Provides very strong construct in severe spine
instability.
• Posterior column + Anterior column Disruption - An
anterior standalone bone graft will not be sufficient for
fixation because
1. Graft extrusion
2. Kyphotic deformity
3. Significant risk of neural injury
• To avoid dislocation and graft extrusion :
1. Anterior plating
2. Supplemental posterior fixation,
3. Rigid external orthosis (halo vest)

39. Conclusion
• Continued improvements in techniques and technology
havenexpanded the capabilities of both anterior and
posterior cervical spine instrumentation.
• The immediate stability afforded by contemporary
constructs facilitates postoperative patient mobility.
Improved techniques enable the treatment of
increasingly complex spinal disease with greater safety
and efficacy, and potentially with less tissue damage.
• The spinal surgeon, however, must have familiarity with
a wide variety of instrumentation techniques as the
optimal technique for any given patient is determined
by the patient’s unique combination of anatomic and
pathologic variations.

40. References
1. Youmann’s and winn neurological surgery 8th ed
2. Benzel’s spine surgery 5th ed
3. Posterior Fixation Techniques in the Subaxial
Cervical Spine. A Ghori et al. Cureus. 2015 Oct;
7(10): e338.
4. Mikhail CM, Dowdell JE 3rd, Hecht AC. Posterior
Fusion for the Subaxial Cervical Spine: A Review
of the Major Techniques. HSS J. 2020;16(2):188-
194.