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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6029_Библиотеки_им_академика_М_И_Перельмана.pdf
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Fig. 6.31 Necessary preoperative fluoroscopical visibility. (a) Odontoid process shank and tip. (b) Unobstructed lateral C2 view
6 Specific Reconstruction Techniques of Upper Cervical Spine and Craniovertebral Junction
fixation is planned, the entry point is created in the midline. We always attempt to first drill the pilot hole for
the lag screw. This strategy allows for a potential second chance in case of an initially wrong trajectory that
is difficult to fix by a simple change of the drill angle.
The drill is covered by a drill guide with a depth gauge;
however the depth measurement is usually fairly inaccurate as it is difficult to obtain a good contact of the
sleeve with the oblique surface of the vertebra. Drilling
is performed slowly step-by-step under continuous fluoroscopy but with high drill speeds as this provides better tactile feedback of resistance. The drill is stopped
Fig. 6.32 Surgeons position with direct view on the fluoro-
screens
once the condense bone of the apex is completely perforated. According to anatomical works, there is, on an
average, a 6 mm safety zone between the apex and the
brainstem. However, maximum attention must be paid
fluoroscopy. We do not damage the C2-3 intervertebral
disk. Because of lack of illumination in the oblique
approach tunnel, we use the headlight and the space is
held open either with the Apfelbaum retractor or simply
by the assisting surgeon using a Hohmann hook fixed
to C2 body (Fig. 6.33). We do not have experience with
tubular retractors that may have the advantage of being
fixed to the table and having tubular lighting. Thin and
sharp probe or K-wire is positioned on the expected
midline of the inferior C2 ridge and its correct position is checked on both fluoroscopes. A long, straight
probe can also predict the final sagittal screw angle
needed. If a double-screw construct is planned (more
common), two entry point holes are created approximately 4–5 mm from the midline at the C2 inferior edge
with a high-speed drill (3 mm burr). If a single screw
to this part of the drilling (i.e., fixed elbows to prevent
unintentional “plunge”). While drilling the first hole, we
already plan the position of the second screw as suffi-
cient space needs to be maintained. The screw should not
be located too far anteriorly within the C2 body as this
may predispose the screw to anterior breakout. The hole
is then tapped including the dens apex using the same
drill guide (Fig. 6.34). We use the Apfelbaum titanium,
short-threaded 4 mm screws attached to self-retaining
screw driver for odontoid fixation. Thus, no overdrilling
of the proximal screw hole is necessary. The screw is
forcefully tightened to perforate the apex approximately
by one thread. In our opinion, this is another essential
part of the procedure. If the screw does not perforate
the apex it can distract the fracture rather than compress
it. It is possible to note any rotational instability during
6.3 Axis as an Anchoring Structure
Fig. 6.33 Fluoroscopical view of two possibilities of oblique surgical canal spreading. (a) With Apfelbaum’s distractor. (b) With
pediatric Hohmann retractor held by assistant
99
Fig. 6.34 Tapping of the pilot hole including the odontoid pro-
cess tip
tapping or screw tightening as rotation of the odontoid
becomes apparent on fluoroscopic images. In such a situation, we drill a second screw hole and the lag screw is
tightened with the drill left in place. Under normal conditions, the second screw is placed in the same manner
with the aim to simply cross the fracture line sufficiently
Fig. 6.35 AP radiogram of double odontoid screw purchase
(Fig. 6.35) to fulfill the anti-rotational purpose. Finally,
the wound is closed in a standard fashion.
Anteriorly oblique fractures are usually considered a
contraindication to the odontoid screw fixation due to
the dislocation risk during screw tightening. In our
opinion, this fracture type can also be treated by this
100
ab
6 Specific Reconstruction Techniques of Upper Cervical Spine and Craniovertebral Junction
Currently, the use of a single versus two odontoid
screws remains controversial. In our opinion, only
those who are technically able to place two screws can
discuss the possibility of a single screw fixation. If the
fracture surface is rough (irregular) and the fracture
can be well compressed, then a single screw fixation
can be sufficiently strong (Fig. 6.37). We feel that the
crucial point is the perforation of apical cortex to allow
strong compression. Otherwise, distraction of the fracture and rotational dislocation of the dens will prevent
bony healing and the screw will subsequently break
(Fig. 6.38). Another possible drawback of direct odontoid screw fixation is poor bone quality in some patients
preventing adequate screw anchorage.
Fig. 6.36 AP fluoroscopical view of parallel K-wire introduced
to allow lag screw tightening without odontoid rotation
technique provided enough bone is available below the
fracture line in the C2 body. This is the fracture that
needs to be reduced preoperatively with positioning, as
emphasized earlier. First, the Kirschner wire (1.5 mm) is
passed to the tip of the dens without cortical perforation.
Then, a pilot hole for lag screw is drilled penetrating the
odontoid apex with subsequent tapping. A short-threaded
screw is placed and forcefully tightened to achieve compression of the fracture while the Kirschner wire is holding the odontoid in place not allowing anterior dislocation
(similarly to rotational instability) (Fig. 6.36). Finally,
the wire is replaced by a short antirotational screw.
We do not use cannulated screws. The main reason
is that we consider apical penetration and compression
of fracture very important and therefore, if a K-wire
was to be in place during tapping or screw tightening,
it could be inadvertently advanced into the canal with
catastrophic consequences.
6.3.6 Screw Introduced into C2 Body
Either monocortically or bicortically introduced screws
into the C2 body are used almost exclusively to fix the
plate stabilizing the axis to C3 and/or lower cervical
vertebras. High anterolateral cervical approach is
derived from the subaxial access described to reach
C3-T1 spine as described in detail in Chap. 4.
6.3.6.1 Our Preference
We use this type of screw purchase only to fix the plate
stabilizing subaxial cervical segments. We prefer to
introduce the screws bicortically in trauma cases especially in hangman type fractures (Figs. 12.14d and
12.18, Chap. 12) or combined injuries (Figs. 14.2 and
14.3, Chap. 14). The monocortical purchase can be
chosen in traumatic and degenerative disk prolapses
without marked segmental instability. From technical
Fig. 6.37 Compression
needed for fracture alignment
and healing. (a) Double
screw purchase. (b) Single
screw compression
6.4 Monosegmental Fusion Constructs
Fig. 6.38 Tomogram of improperly tightened screw 9 months
after surgery. Note distraction – pseudoarthrosis
101
6.4.1.1 Posterior C0-1 Fixation Methods
Grob [81] speculated that the ideal fixation should only
fix the target segment. Therefore, atlanto-occipital instability or dislocation should only be stabilized through
the CVJ if possible. Currently, there are two main
options for posterior stabilization of atlanto-occipital
joint. As described above, Grob [81] suggested performing a C1-0 transarticular fixation similar to Magerl
procedure for C1-2 (Fig. 6.3). Because of biomechanical weakness in flexion, Gonzalez et al. [75] proposed
the use of a bone graft between occiput and the atlas,
similar to Gallie type fusion. The same group successfully performed three such posterior stabilizations [60].
Maughan et al. (Fig. 6.39) described another option for
atlanto-occipital fixation in a patient with circular avulsion fracture of foramen magnum. It involved occipital
plate and C1 lateral mass screws connected by a rod
[156]. Bambakidis et al. [16] compared the two previously mentioned techniques with occipitoatlantal wire
and rod fixation, biomechanically. They found that both
screw techniques are substantially stiffer than the wirerod method. Nevertheless, they also confirmed that the
transarticular screw supplemented with a buttress graft
is slightly more rigid than the plate-screw-rod system.
point of view, compared to standard anterolateral
ACDF, the only difficulty represents the distant upper
C2 screw purchase. To enable the C2 anterior surface
perpendicular drilling trajectory quite important midline dislocation is necessary. In such a case, we remove
all the automatic wound retractors. This wound release
allows for more easy medial pharyngeal and laryngeal
dislocation. Usually, the drilling and screw purchase
are performed with manual wound distraction and with
instruments covered by a protection sleeve.
6.4 Monosegmental Fusion Constructs
6.4.1 Posterior Monosegmental Fusion
Constructs
Posterior monosegmental fusion constructs are usually
strong enough to maintain stability without the need
for external bracing and allow for exclusion of mobile
segments not involved in the pathological movement.
6.4.1.2 Our Preference
For mild types of AOD, isolated condyle fracture dislocations, and chronic atlanto-occipital instabilities, the
short monosegmental posterior fixation is sufficient.
Fig. 6.39 Artistic drawing of atlantooccipital fixation according
to Maughan
102
6 Specific Reconstruction Techniques of Upper Cervical Spine and Craniovertebral Junction
However, for typical AOD caused by high impact
trauma disconnecting the ligamentous attachments of
the head to the spine, the short construct is insufficient.
Such patients, if they survive, are often bedridden and
ventilator dependent needing very frequent positioning
and passive manipulation. Instability can have catastrophic consequences. Taking patient’s prognosis into
account, a construct extended to C2 or more caudally
may have negligible influence on further quality of life.
6.4.1.3 Posterior C1-2 Fixation Methods
Mixter and Osgood Silk Loop
In 1910, Mixter and Osgood [161] were the first to
describe surgical treatment of atlantoaxial instability
in a 15-year-old boy who fell from a tree. He came
to be operated in Massachusetts General Hospital,
6 months after unsuccessful conservative treatment of
unrecognized odontoid fracture with C1/2 dislocation.
He had pain but no neurological deficit. He was first
manipulated under anesthesia. Then new radiographs,
including transoral projections, revealed the old odontoid fracture. A leather external orthosis was manufactured. Surgery was performed by Dr. Mixter from
posterior midline approach. Benzoin-soaked, braided
silk loop was passed below the C1 arch and around
spinous C2 process and no bone graft was added. The
patient survived and fused without complications.
In this report, we can recognize some interesting
facts. They performed “open mouth” films to visualize
the UCS. They reviewed the available literature and
concluded that in the UCS trauma cohort, the most
common abnormality was atlantoaxial dislocation
without fracture, followed by odontoid fractures and
then fractures of C1 and C2 arches, and lateral masses.
imperative. Posterior surgical treatment was indicated
whenever displaced facets were irreducible by traction, or failed to maintain reduction in external orthosis or in cases of non-reduced malunion. He stated that
“recurrence of displacement can be prevented by fastening the two vertebrae together by fine steel wire
passed around the laminae or spines. And the risk of
late recurrence can be eliminated by bone grafts laid in
the spines or on the laminae and articular facets.” So,
no typical H shape graft was mentioned neither
depicted on the pictures in the original paper. Other
authors also describe the technique of posterior graft
and wiring, even 2 years earlier [33]. Fried used the
“Gallie method” of C1-2 wiring and grafting after
scraping the atlantoaxial joints with failure rate of 80%
[66]. The first paper describing an H-shaped onlay
notched graft placed on the surface of C1 and spinous
process of C2 is that of McGraw and Rusch [158].
It can be summarized that the original technique of
onlay grafting is the simplest fusion method but also
the least stable when compared to other techniques,
especially in rotation [82]. Today, the notched onlay
graft positioned on the surface of C1 and around the
spinous process of C2 is called “Gallie – type graft”
(Fig. 6.40). Failure (pseudoarthrosis, wire breakage, or
loosening) of Gallie type fusion can be seen in up to
80% of cases if used as standalone method [66]. Fusion
rate can be improved with halo bracing, but even then
25% of cases still fail [36].
Brooks and Jenkins – Wire and Graft
In order to increase the stability of posterior wire and
graft fusion, Brooks and Jenkins suggested interposing
Atlantoaxial Wire and Graft
The addition of an H-shaped bone graft currently used
as supplement to other more solid metal constructs, is
usually attributed to W.E. Gallie, surgeon from Toronto.
He published his algorithm in 1939, describing how to
treat fractures and dislocations in cervical spine [67].
He suggested to always begin with skeletal head traction in cases of subluxation anywhere in the cervical
spine, emphasizing that reduction of dislocation is
Fig. 6.40 Gallie’s type of posterior AA fixation
6.4 Monosegmental Fusion Constructs
Fig. 6.41 Brooks and Jenkins type of grafts and wire posterior
AA fixation
103
Fig. 6.42 Sonntag’s modification of AA graft and wire fixation
two grafts laterally between the C1 and C2 laminae by
wedge compression technique [24]. Beveled iliac crest
autografts were fixed in place with doubled 20 gauge
stainless steel sublaminar wires (Fig. 6.41). It is the
need for bilateral sublaminar cable passage that has a
higher potential rate of neurological or dural injury.
They successfully treated 15 patients with final fusion
rate of 93%. They supplemented their surgical procedure by postoperative use of either a Minerva or SOMI
brace. Later works evaluating larger series using
Brooks method for C1-2 fixation reported failure rate
up to 30% [36, 80].
Sonntag – Wire and Graft
Sonntag et al. modified the Gallie graft fusion technique
in the early 1990s in an attempt to improve stability of
the construct and avoid bilateral C2 sublaminar cables
[46]. They decorticated the contact surfaces of C1 and
C2 arches and interposed curvilinear strut graft approximately 4 cm long with caudal notch for the C2 spinous
process. The graft was then fixed by a cable passing
under the posterior arch of C1 and looped around a
notched inferior C2 spinous process (Fig. 6.42).
However, in patients treated with posterior wiring techniques only, they treated them with three months of
postoperative halo immobilization. This approach
achieved 97% fusion rate in their series of 36 patients.
Acrylic C1-2 Fusions
Poly-methyl-methacrylate (PMMA) onlay for atlantoaxial fixation was advocated as a fast option for surgical
immobilization in patients with traumatic atlantoaxial
instability. Kelly et al. [124] successfully treated seven
patients suffering from traumatic AA instability with
pure C1-3 acrylic and wire fusion. Authors reported
“fusion” in all cases in “satisfactory” position during
an 8–9 year follow-up. Good, long-term results were
also reported in other series [50, 206]. The experienced
authors recommended using screw anchors imbedded
in the acrylate to increase the long-term stability [50].
However, the main objections of polymethacrylate
fixation method are the heat produced during polymerization process and the inability of PMMA to bond
to bone. Further, a large number of revisions due to
infection, inlay loosening, or inability to maintain spinal alignment led to substantial decrease in popularity of PMMA fixations [157]. In our opinion, PMMA
can still be used as a palliative measure in UCS tumor
surgery and/or if used in other indications, it has to be
supplemented with additional bone grafting.
Halifax Atlantoaxial Interlaminar Clamps
After a very successful application of interlaminar
clamps in the treatment of subaxial cervical spine
trauma [101, 227], this method was applied in the
treatment of atlantoaxial instability as well. Cybulski
et al. [39] confirmed the safety of interlaminar clamps
with one out of eight clamps loosening prior to fusion.
Clamps with claw-type construct avoid the need for
sublaminar cable and its potential risks but the risk of
neural injury is not completely depleted (Fig. 6.43).
The exact fit of the clamps can be of concern under
certain anatomical conditions, so can be the loosening
of compressing screws. Previously described problems
were the main reason for failure and revision of up to
20% of cases, especially in the absence of bony graft
104
Fig. 6.43 Halifax clamp with interlaminar grafts
6 Specific Reconstruction Techniques of Upper Cervical Spine and Craniovertebral Junction
wire loosening are relatively common complications
of wiring techniques [251]. If there is a need for standalone posterior wiring technique, then the Sonntag
modification should be used supplemented by external
hard brace (SOMI) or a halo vest.
It is generally accepted that solid bony fusion, when
desired, is most reliably achieved when the segmental
fixation minimizes motion. This is why the previously
mentioned techniques were not the last point in C1-2
fixation development and more rigid screw constructs
followed.
[4, 163, 210]. If iliac crest autograft is interposed and
the halo vest applied then fusion rate improves
dramatically [109]. Historically, other claw type constructs were also used.
In summary, methods using posterior C1 and C2
arches to fix the segment do have some advantages but
also some important disadvantages:
Advantages
– Simple to apply
– Valuable addict to other more firm fusion methods
– Can be a salvage procedure (AV injury during screw
techniques)
Disadvantages
– Posterior elements must be intact
– Not possible in low bone quality of arches
(osteopenic status)
– Cable has to pass bellow the arch of C1 (dangerous
in dislocation)
– High failure rate
– Necessity for hard external support
– Autologous graft-related complications
Our Preference
Posterior wiring techniques have long been the mainstay of surgical stabilization of atlantoaxial complex.
They are relatively easy but of limited stiffness. In particular, they cannot reach the same stability in translation and rotation when compared to other screw
constructs. The “parallelogram effect” was well
described by Panjabi [176]. The other concern is that
they provide less than optimal fusion rates and external
rigid immobilization is mandatory. Graft breakage or
Transarticular C2-1 Screw Fixation (Magerl)
Magerl’s technique of C1-2 fixation (Fig. 6.44), introduced in 1987 [152], gradually achieved a high degree
of acceptance and success, mainly because of high
fusion rates, instant stability, and relatively low incidence of complications. It has gained popularity over
the wiring techniques used earlier for posterior atlantoaxial stabilization especially because of higher proven
biomechanical stability avoiding the necessity of postoperative hard external support [82, 164, 188, 237].
High fusion rate (between 87 and 100%) was documented by many authors [36, 44, 69, 86, 91, 116, 154,
212, 214, 219]. As described earlier, a meticulous technique must be used to achieve a safe C2 transisthmic
passage and adequate C1 lateral mass anchorage.
Thorough preoperative anatomical analysis with 3D
modeling in potentially risky cases is invaluable in
identifying patients/sides unsuitable for the transisthmic screw [234]. As the risk of VA injury can be as high
as 23% per patient in borderline cases, navigational systems can prove to be a useful adjunct [99, 100, 234].
Strong C1 anchorage is important, therefore the
screw should be placed at least 5 mm within the bone
and should not protrude more than 5 mm. Grob et al.
[86] evaluated 161 patients in a multicentre Swiss
study and found a 15% rate of less than perfectly positioned screws with 3.4% of them missing the C1 lateral mass. In our cohort of 80 patients collected from
4 centers, 150 screws were placed [219]. The morphology on one side of six patients prevented adequate
screw placement and two procedures needed to be converted to posterior wire fusion. VA injury was encountered in four patients (5%) without clinical
consequences. We found 28.6% of screws to be suboptimally placed. They were adequately imbedded in the
6.4 Monosegmental Fusion Constructs
Fig. 6.44 Transarticular
C2-1 fixation according to
Magerl. (a, b) Posterior and
lateral view. (c) Transarticular
AA fixation supplemented
with posterior graft and wire
fusion
105
C1 lateral mass but in 6% they were too short, in 5.3%
too long, and in the other 17.3% deviated out of middle
third of the mass (Figs. 6.45–6.47). Four screws (2.7%)
were misplaced (i.e., out of C1 lateral mass).
Computerized navigation can substantially improve
accuracy. Foley et al. [65] were the first who used stereotactic guidance to place atlantoaxial transarticular
screws with improved safety. Weidner et al. [234]
placed 72 screws with image guidance and significantly decreased the frequency of suboptimally placed
screws. On postoperative CT, they found lateral deviation only on three sides and medial, on only one. The
anchorage within C1 lateral mass was always sufficient. Several authors reported a successful and safe
placement of transarticular C1-2 screws in pediatric
population as young as 3 years of age [23, 97].
Fig. 6.45 Correct transarticular screw position and length. (a) Transoral radiograph. (b) Lateral view
106
6 Specific Reconstruction Techniques of Upper Cervical Spine and Craniovertebral Junction
Biomechanical superiority over posterior graft fixation techniques is given by more central position of the
screws and was, indeed, confirmed in many biomechanical studies [82, 93, 132, 164, 188, 237]. The stability of the construct in flexion-extension is certainly
improved by and comparable to Goel-Harms procedure if posterior wire-fixed graft is added [202]. On the
other hand, Naderi et al. [164] found that unilateral
screw fixation is much less stable than bilateral one in
all directions, especially in rotation.
Sven Olerud suggested a modification of Magerl’s
method to decrease the frequency of graft-related problems but mostly to increase the stability of the construct [174]. He connected transarticular screws to an
Fig. 6.46 Postoperative evaluation of transarticular screw posi-
tion and length from plain X-rays (suboptimal means sufficient
anchorage of C1 lateral mass). (a) Suboptimal purchase, too
long screws. (b) Too short screws, suboptimal introduction.
(c) Suboptimal position, too medially located left screw.
(d) Suboptimal purchase, too laterally located left screw.
(e) Wrong trajectory, the screw is outside of C1 lateral mass
6.4 Monosegmental Fusion Constructs
Fig. 6.46 (continued)
adaptable claw attached to the posterior arch of C1 with
a 3.5 mm rod. This innovative technique allows for use
of morselized graft only because a structural block
of bone was not necessary to create a posterior band.
Another theoretical advantage is that the claw can grasp
even a partially defective posterior C1 arch in situations
where cable fixation would not be possible. The Olerud
modification was later successfully used in 26 patients
with 91% fusion rate treated for AA instability caused
by trauma, RA, and developmental anomalies [35].
In our experience, there are advantages and disad-
vantages of the described technique:
107
Advantages of Magerl’s technique
– Immediate and strong stability, no external support
needed
– Laminae could be absent, no wiring necessary
– Longer construct incorporation is feasible if polyax-
ial screw heads are used
– High fusion rate
– If bone block-wire fusion added, biomechanically
superior
– Cost (it is significantly cheaper than other
techniques)
– Low profile of hardware
Disadvantages of Magerl’s technique
– VA injury risk in up to 23% of patients
– The angle of C2 transpedicular trajectory is not
easy to achieve
– Reduction feasibility of atlantoaxial dislocation
possible, but limited
– Cannot be used if target structures are comminuted
or destructed
– C1-2 joint is damaged
– Learning curve necessary
– Fluoroscopy mandatory
Our Preference
Magerl’s fixation is often described as unsafe but it is
not dangerous because of the technique itself. It is the
surgeon who can make the procedure unsafe, usually as
a result of inadequate preoperative radiological analysis
Fig. 6.47 CT verification of correct transarticular screw positions. (a) Oblique axial reconstruction. (b, c) Parasagittal reconstruc-
tion of both sides of pars interarticularis screw position