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_6019_Библиотеки_им_академика_М_И_Перельмана.pdf
390
M.B. Frenkel et al.
Numerous biomechanical studies have demonstrated benefits of this enhanced cortical purchase.
Several investigators have instrumented cadaveric
lumbar vertebrae with pedicle screws in one pedicle and cortical screws in the contralateral pedicle
before subjecting both screws to biomechanical
testing. Santoni found that cortical screws had a
30% increase in uniaxial yield pullout load and no
significant difference in construct stiffness com-
Fig. 29.1 Width of exposure needed for placement of
cortical trajectory screws (green tissue) compared to traditional trajectory pedicle screws (blue tissue). Dashed blue
lines represent the approach trajectory for cortical screws,
while dashed white lines represent the same for traditional
trajectory pedicle screws (Courtesy Medtronic)
pared to traditional pedicle screws [1]. ønceo÷lu
found a statistically significant increase in pullout
strength of cortical screws compared with pedicle
screws; however, cortical screws had less tangential stiffness compared to the pedicle screws [5].
Cyclical toggling of the screws at increasing
physiologic loads has demonstrated significantly
increased resistance to toggling for the cortical
screw [6]. It has been proposed that this high toggling resistance may be attributable to the angle of
the cortical screw providing purchase of the thick
cortical bone of both the inferior and superior
pedicle isthmus [7]. In regard to multilevel constructs, Cheng in one cadaveric study demonstrated equivalence of cortical screws with pedicle
screws in stabilization of multilevel low-grade
spondylolisthesis models [7].
Another cadaveric study compared pedicle
screws and cortical screw rod fixation in specimens with intact intervertebral disc, transforaminal lumbar interbody fusion (TLIF) support, or
direct lateral interbody fusion (DLIF) support.
The authors found that the cortical screw group
had comparable stability in flexion/extension and
lateral bending when an intact disc was present
but the pedicle screw group was stiffer during
axial rotation. There was no difference in stability
with DLIF. In the TLIF group, they found that the
pedicle screw fixation was stiffer than cortical
screw fixation during lateral bending [8]. A separate finite element analysis also reported similar
results, with cortical screws having greater pullout strength and superior resistance to flexion/
extension loading but inferior resistance to lateral
Fig. 29.2 Cross sections of cadaveric vertebrae previously instrumented with cortical trajectory screws (left)
and traditional trajectory pedicle screws (right). The blue
circle indicates the amount of cortical bone encountered
along each trajectory (Courtesy Medtronic)
29 Cortical Bone Screw Fixation
391
Fig. 29.3 Lateral (left), superoinferior (middle), and
anteroposterior (right) fluoroscopic views of a cadaveric
lumbar vertebra with the trajectories of cortical (green
line) and traditional pedicle screws (dashed white line)
bending and axial rotation compared to pedicle
screws [9].
In addition, an in vivo biomechanical study
comparing pedicle screws and cortical screws
was performed by measuring the insertional
torque during screw placement in 48 consecutive
patients. Matsukawa found that the insertional
torque of cortical screws was about 1.7 times
higher than pedicle screws [10].
Aside from increased cortical purchase, several other benefits of the medial to lateral and
caudal to cephalad cortical screw trajectory have
been reported. A retrospective study of 202
patients who underwent cortical screw placement
found the incidence of adjacent cranial facet joint
violation by the screw, a phenomenon which can
contribute to the development of adjacent level
disease, to be lower than or comparable to most
historical reports of open or percutaneous pedicle
screw placement [11]. Matsukawa et al. have
suggested that this unique trajectory may result
in a lower rate of damage to neural elements, as a
misplaced screw would be less likely to breach
medially or inferiorly and injure the thecal sac or
exiting nerve root [12].
With regard to clinical outcomes, the largest
published series of patients who underwent lumbar fusion with cortical screws included 79
patients at a single institution with mean follow up of 13 months. Snyder reported only one case
of screw loosening, two cases of pseudoarthrosis, and one case of graft migration in the entire
overlaid. Note that the trajectory of the cortical screws has
a more medial insertion point compared to the traditional
pedicle screw trajectory, as well as a medial to lateral and
caudal to rostral trajectory (Courtesy Medtronic)
population. They had no complications caused
by misplaced screws in any patients [13]. A retrospective study of ten TLIFs performed with
cortical screws reported less intraoperative blood
loss compared with similar cohorts of patients
who underwent TLIFs with pedicle screws
placed either via the Wiltse or percutaneous
approach. Kasukawa also reported good outcomes at a mean follow-up of 11.4 months with
no evidence of hardware loosening and fusion
rates comparable to the other groups [14]. Lee
performed the first prospective randomized trial
comparing 40 cortical screw patients to 39 pedicle screw patients in single-level PLIF patients
who had minimum 12-month follow-up. The
authors found similar fusion rates and improvement in pain and functional status between the
two groups. They also observed shorter operative time, incision length, and less blood loss in
the cortical screw group [15]. These findings are
also consistent with a number of other published
case reports [
16–18].
One early report of clinical outcomes had less
than desirable results, with five of eight patients
demonstrating evidence of screw loosening and
two requiring revision within 1 year [19]. More
recently, Cheng experienced a unique intraoperative pars fracture while placing cortical screws
in 2 of 22 patients, one of which was not discovered until the patient subsequently developed
complications from screw loosening. The fracture spanned from the screw insertion point on
392
M.B. Frenkel et al.
the lateral border of the pars through the superior
facet and into the lateral aspect of the pedicle.
The authors performed a cadaveric study and
attempted to reproduce the fracture while video
recording their screw insertion. They were successful and discovered that during final screw
placement, the head of the screw impinged medially against the lamina and base of the spinous
process, suddenly deviating the screw trajectory.
The authors attributed the prior group’s high rate
of loosening to this phenomenon and recommended leaving the screw proud to avoid hubbing, as well as performing laminectomy before
final screw insertion to attempt to avoid this phenomenon [20]. Similar concerns over the head of
the screw resting on the junction of the spinous
process and lamina were voiced by Akpolat et al.
[21] who were unable to fully insert some screws
because of fear of damage to the lamina or pars.
As a consequence of the shorter trajectory
and increased cortical purchase of cortical
screws compared to pedicle screws, specialized
screws have been developed for use along this
trajectory. These cortical bone screws (CBS)
differ from traditional pedicle screws in that
they have a shorter distance between threads
(narrower pitch) and smaller ratio of inner to
outer diameter [5]. A cadaveric study investigated the differences in pullout strength in both
a traditional and cortical bone trajectory when
using two screws which were similar except for
thread pitch. They found that while the narrower pitch screws provided a small increase in
pullout strength with both trajectories, it was
actually the cortical screw trajectory which had
the most significant impact on pullout strength
[22]. Wray had similar results and also deter-
mined that their findings remained true in both
high- and low-density bone groups, suggesting
benefits of cortical screws in osteoporotic
patients [23].
Indications and Patient Selection
The indications for cortical screws appear to be
the same as those for traditional pedicle screws
for degenerative lumbar pathology with segmental
instability. These include both degenerative and in
some circumstances lytic spondylolisthesis, lumbar stenosis with instability, recurrent disc herniation, adjacent level degeneration, and
pseudoarthrosis. There are a number of situations
in which cortical screws may be preferred over
pedicle screws. The shorter length and more vertical trajectory of cortical screws relative to pedicle
screws are less likely to interfere with anterior
vertebral body screws and thus may be preferred
when adding posterior instrumentation to these
patients [13].
As previously discussed, there is biomechanical evidence supporting the use of cortical screws
in osteoporotic patients, and cortical screws may
be preferred over pedicle screws in this population. Ueno has described a “double-trajectory”
technique in which pedicle screws and cortical
screws were placed together in all pedicles in a
severely osteoporotic patient requiring L1–S1
fusion and correction for degenerative scoliosis.
They reported good results at 14-month follow up with no hardware complications [24].
The use of cortical screws for “rescue” of a
failed pedicle screw has also been examined in a
cadaveric biomechanical study. Calvert et al.
stressed pedicle screws to failure in an instrumented lumbar spine model and then replaced
them with cortical screws. They found that in
addition to retaining 60% of the original pedicle
screw pullout strength, the rescue cortical screw
provided similar stiffness to that of the primary
pedicle screw in flexion/extension and axial rotation. The authors also found similar results when
testing a pedicle for replacement of a failed cortical screw [25].
Rodriguez et al. reported [16] the use of cortical screws in pedicles already instrumented with
pedicle screws for treatment of adjacent-segment
lumbar disease (ASLD) (Fig. 29.4). This method
allowed for the treatment of ASLD through a
minimally invasive approach without the need for
exposure or removal of old hardware. At least
one group has reported a hybrid technique in
which they use cortical screws cranially and pedicle screws caudally in single-level fusions [26].
Contraindications to using cortical screws
include cases where competent pedicles are
29 Cortical Bone Screw Fixation
393
Fig. 29.4 Postoperative anteroposterior (left) and lateral
(right) fluoroscopic imaging of a L3–L4 cortical screw
construct added above a prior L4–S1 traditional pedicle
lacking, such as in the case of fractured pedicles
or pedicles affected by a neoplastic or infectious
process. It may be more difficult to place cortical
screws when the screw starting point at the junction of pars and transverse process is absent from
prior decompression.
The use of cortical screws may be less optimal
in spondylolytic vertebrae as a finite element
study demonstrated lower fixation strength in all
planes of motion compared with a pedicle screw
construct. One explanation for these findings is
that pedicle screw relies mainly on the trabecular
bone within the pedicle for its fixation strength,
while the cortical screw relies largely on the pars
and adjacent lamina which is lacking in spondylolytic vertebrae [27].
Cortical screws can be used both with or without additional interbody support. A previously
mentioned cadaveric study [9] demonstrated that
cortical screws have similar overall stability compared to pedicle screws in specimens with intact
intervertebral discs, specimens with TLIF support, and specimens with DLIF support. It is at
the surgeon’s discretion whether or not to use
interbody support with cortical screws, but based
on this evidence, the decision-making process
should mirror that of pedicle screws.
screw construct. Note that cortical screws were added to
the L4 vertebrae without disrupting the existing traditional pedicle screws
Preoperative Considerations
When planning fixation, the surgeon must always
keep placement of the more medial head of the
cortical screw in mind. In a number of scenarios,
such as extending upward from an old construct
with pedicle screws or mixing pedicle screws and
cortical screws in the same construct, the surgeon
may have difficulty lining up rods between cortical screw and pedicle screw heads. In this circumstance, the rod would be oriented obliquely
instead of vertically as it angles from the more
lateral caudal screw heads.
We perform our cortical screw placement with
the use of intraoperative fluoroscopy. In the past,
we have reported [16] the use of intraoperative
navigation for placement of these screws, and we
recommend its use when placing a cortical screw in
a pedicle which is already instrumented with a pedicle screw. We have also had good early experience
with the use of an intraoperative robot for placement of cortical screws. This represents a potential
advance which provides the benefit of preoperatively planning the exact screw trajectory.
Finally, the surgeon should ensure the availability of appropriate cortical bone screws. As
previously discussed, screws with a narrower
394
M.B. Frenkel et al.
pitch provide increased pullout strength over conventional cancellous thread patterns, and we recommend their use. In general, we use 5.0 mm
diameter by 30–35 mm in length screws.
Surgical Technique
After the induction of general anesthesia, we
position the patient prone on two chest rolls on a
conventional surgical table. We do not typically
perform any additional manipulation at this stage
to increase lordosis as we accomplish this primarily through the use of lordotic interbody
grafts and compression of the screws during final
tightening. The correct operative level is identified using fluoroscopy, and a midline incision is
marked before prepping and draping in a sterile
fashion. We do not the routinely use intraoperative monitoring for cortical screw procedures
which are generally one or two level procedures.
For single-level operations, we make an incision
roughly 30–40 mm in length, but this is elongated
for multilevel procedures. Once incision is made,
it is extended down through the fascia over the
paraspinal muscles in the midline. We use the
minimal access spinal technologies (MAST)
midline lumbar fusion (MIDLF) system
(Medtronic, Minneapolis, MN) for retraction.
Muscle from the spinous process and lamina of
the operative levels are bluntly dissected with the
speculum retractor. This speculum retractor has a
ruler which is then used to determine the appropriate MAST retractor blade length. The speculum retractor is rotated 90° and opened so that the
MAST retractor blade may be inserted between
the blades of the speculum retractor over the
operative disc space. The other MAST retractor
blade is inserted on the contralateral side in the
same manner. These MAST blades are then
attached to the retractor device which is then
used to angle them outward laterally, maximizing
the operative field visible through the incision.
The retractor is then opened, exposing the operative corridor. The surgeon may then either attach
the light source to the retractor and continue the
operation using loupes or use the operative
microscope.
Prior to screw insertion, bilateral PLIF or
TLIF is performed but can be done unilaterally if
the surgeon desires. The inferior facets of the
superior vertebral level to be fused are amputated
using an osteotome and mallet. This exposes the
superior facet of the inferior vertebra to be fused
which is then removed with a Kerrison rongeur.
This bone is then ground for use as autograft later
in the case. Some authors have reported that spinous processes must be removed in order to reach
a necessary angle for the medial to lateral trajectomy [20], and this may be performed now as
well. The yellow ligament and soft tissues are
also removed with the Kerrison rongeur to expose
the dura and disc space and to achieve central and
lateral recess decompression. The borders of the
pedicle at the inferior level are identified with a
Woodson elevator or angled curette.
The dura is gently retracted and annulotomy is
performed. The disc material is removed with pituitary rongeurs and down-pushing curettes.
Sequential dilators are used to gradually restore the
disc space to its normal height, and a template is
used to determine an appropriate interbody device
size. Morselized autograft, which may be combined with a biologic extender material, is inserted
into the central disc space and the implants. The
interbody devices are inserted with caution to avoid
injury to traversing or exiting nerve roots.
Once interbody fusion is completed, attention is turned to screw placement. The starting
point for the cortical screw is approximately
1 mm inferior to the transverse process, 4 mm
medial to the lateral aspect of the pars interarticularis. If the inferior articular process is disrupted due to the patient’s pathology or previous
surgery, locating an insertion point for the screw
may be difficult. In these cases, a starting point
4 mm medial to the lateral aspect of the pars
may be used as a horizontal starting point with a
vertical starting point at the level of the superior
margin of the intervertebral foramen as seen on
lateral fluoroscopy [28]. Relative to an anteroposterior view of the pedicle, the optimal screw
insertion point can be imagined projecting from
a starting point at the 5 o’clock orientation in
the left pedicle and 7 o’clock orientation in the
right pedicle [
12].
29 Cortical Bone Screw Fixation
395
The trajectory of the screws is caudocephalad
and mediolateral. Matsukawa used in vivo measurements of insertional torque to determine an
ideal trajectory for placement of cortical screws
and found it to be 25–30 degrees cranially and 10
degrees laterally along the inferior border of the
pedicle [29].
The entry point and trajectory are confirmed
prior to and during pilot hole drilling using the
C-arm for fluoroscopic imaging. The entry point
is made using a high-speed drill with a routing bit
measuring approximately 2 mm at the tip. During
drilling, we frequently pause to confirm the tip
remains in cortical bone by tapping the bit against
the bottom of the hole. AP and lateral fluoroscopy can be used to verify the correct screw trajectory. The tip of the drill is slowly advanced to
approximately 30 mm. We inspect the tract to
ensure no breach has occurred before tapping
with the 5.0 or 5.5 mm cortical thread tap. The
hole is reinspected for a breach after tapping and
the screw is then inserted. This is repeated for the
remaining cortical screws to be placed (Fig. 29.5).
For screws placed at S1, we modify our technique slightly. At this level, we identify the
medial and superior borders of the S1 pedicle
during the decompression. The routing drill bit is
then used to drill a tract with a “straight-in” trajectory into the S1 pedicle. We also place a larger
diameter screw at this level, usually 7.5 mm.
The rods are inserted and secured with set
screws tightened under compression to help
secure segmental lordosis. We then close fascia
and skin in a usual fashion and cover the incision
with a topical skin adhesive.
Illustrative Case
History
injections which helped at first but were no longer
providing her any relief. She endorsed some relief
when lying flat, but her pain was refractory to pain
medication. She had also tried physical therapy
with no relief.
Physical Exam
On examination, the patient was noted to have an
antalgic gait. Patellar and Achilles deep tendon
reflexes were present but decreased in amplitude.
She endorsed hypoesthesia to light touch in the
lateral and posterior left lower extremity. She had
significant pain with straight leg raise on the left.
All lower extremity muscle groups appeared full
strength, and she had no signs of myelopathy.
Radiographical Imaging
Magnetic resonance imaging of the patient’s
lumbar spine revealed a Grade 1 degenerative
spondylolisthesis at L5–S1 with disc collapse
and foraminal stenosis (Fig. 29.6). Dynamic
radiographs of her lumbar spine demonstrated a
9 mm anterolisthesis of L5 on S1 which worsened with flexion.
Treatment
She was taken to the operating suite where a
MAST bilateral L5–S1 PLIF was performed with
cortical screws at L5 as previously discussed.
The described “straight-in” trajectory was used
for the S1 screws. Her hospital course was
uneventful, and she was discharged home on the
second postoperative day.
A 74-year-old female presented with complaints
of radicular pain in the right lower extremity as
well as midline axial back pain. The pain had
been present for more than 10 years but had been
gradually worsening and had recently progressed
to include numbness and weakness with standing.
She had undergone multiple epidural steroid
Outcome
Lumbar radiographs obtained immediately post op and at 1-month, 3-month (Fig.
12-month follow-up showed good hardware
placement with no evidence of screw back out or
loosening. At her 1-month postoperative visit, she
29.7), and
396
M.B. Frenkel et al.
Fig. 29.5 Postoperative AP (top left) and lateral (top
right) radiographs demonstrating cortical screw fixation
of L4 and L5 vertebral bodies. Axial CT imaging in the
reported an improvement in her leg numbness and
a resolution of her radicular pain. Twelve months
postoperatively, she reported a complete resolution of all her symptoms and noted that she had
lost 20 lbs through an exercise program she had
previously been unable to participate in.
Technical Pearls
• Surgeons may initially use CT-guided navigation
or both AP and lateral fluoroscopy while gaining
familiarity with the trajectory to help avoid pedi-
cle breach and optimize bone screw fixation.
same patient demonstrating screw trajectory in both L5
(bottom left) and L4 (bottom right)
• Given the medial trajectory starting point for
CBT, the technique can be easily incorporated
with midline minimally invasive systems.
• Visually confirm the lateral pars and transverse process junction before initial pilot drilling. Occasionally contours in the lamina pars
junction may be misleading and lead to a
medial screw placement.
• The length of the drill bit must equate to the
proposed length of the screw. Inadequate drill
depth may lead to fracture of the lateral cortical wall.
• Should the lateral pars fracture upon insertion
of the screw, this is easily converted to a
29 Cortical Bone Screw Fixation
Fig. 29.6 Preoperative lateral fluoroscopic imaging demonstrating a Grade 1 spondylolisthesis at L5–S1
397
traditional pedicle screw approach as a salvage technique without requisite addition of
the adjacent level.
Complications and Strategies for Avoidance
Placement of the screw in S1 requires a slightly
modified technique. At this level, an alar cortical
screw trajectory can lead to damage of the traversing L5 roots. In our early experience, 2 of 21
patients who underwent CBT sacral fixation with
an attempted alar trajectory required subsequent
revision due to impingement of the L5 nerve roots.
We now use shorter screws with a “straight- in” trajectory at S1. The tips of these screws terminate
within the sacrum. Other authors have described a
similar trajectory with the tip of the screw penetrating the S1 superior end plate [30]. Caution
should be taken with placement of cortical screws
at this level, and the surgeon may want to consider
Fig. 29.7 Postoperative anteroposterior (right) and lateral (left) fluoroscopic imaging demonstrating the posterior lum-
bar interbody fusion performed at L5–S1 using cortical screws in the L5 vertebral body
398
M.B. Frenkel et al.
an intraoperative O-arm CT after placement of
these screws if CT-guided navigation is not used.
Salvage of a pedicle fracture during insertion
of a cortical screw with a pedicle screw has been
described in the literature [14] and may be of
benefit in this situation.
Conclusion
Cortical bone trajectory screws are an exciting
new addition to the armamentarium of spinal
techniques. Their more medial insertion point
provides for a faster, less invasive exposure than
traditional trajectory pedicle screws while still
maintaining similar biomechanical strength.
References
1. Santoni BG, Hynes RA, McGilvray KC, et al. Cortical
bone trajectory for lumbar pedicle screws. Spine
J. 2009;9(5):366–73.
2. Hung C-W, Wu M-F, Hong R-T, Weng M-J, Yu G-F,
Kao C-H. Comparison of multifidus muscle atrophy
after posterior lumbar interbody fusion with conventional and cortical bone trajectory. Clin Neurol
Neurosurg. 2016;145:41–5.
3. Hirano T, Hasegawa K, Takahashi HE, et al. Structural
characteristics of the pedicle and its role in screw stability. Spine. 1997;22(21):2504–9–discussion 2510.
4. Mai HT, Mitchell SM, Hashmi SZ, Jenkins TJ, Patel
AA, Hsu WK. Differences in bone mineral density
of fixation points between lumbar cortical and traditional pedicle screws. Spine J. 2015;16(7):835–41.
5. ønceo÷lu S, Montgomery WH, St Clair S, McLain
RF. Pedicle screw insertion angle and pullout strength:
comparison of 2 proposed strategies. J Neurosurg
Spine. 2011;14(5):670–6.
6. Baluch DA, Patel AA, Lullo B, et al. Effect of physio-
logical loads on cortical and traditional pedicle screw
fixation. Spine. 2014;39(22):E1297–302.
7. Cheng WK, ønceo÷lu S. Cortical and standard trajec-
tory pedicle screw fixation techniques in stabilizing
multisegment lumbar spine with low grade spondylolisthesis. Int J Spine Surg. 2015;9:46.
8. Perez-Orribo L, Kalb S, Reyes PM, Chang SW,
Crawford NR. Biomechanics of lumbar cortical screwrod fixation versus pedicle screw-rod fixation with and
without interbody support. Spine. 2013;38(8):635–41.
9. Matsukawa K, Yato Y, Imabayashi H, Hosogane N,
Asazuma T, Nemoto K. Biomechanical evaluation
of the fixation strength of lumbar pedicle screws
using cortical bone trajectory: a finite element study.
J Neurosurg Spine. 2015;23(4):471–8.
10. Matsukawa K, Yato Y, Kato T, Imabayashi H,
Asazuma T, Nemoto K. In vivo analysis of insertional
torque during pedicle screwing using cortical bone
trajectory technique. Spine. 2014;39(4):E240–5.
11. Matsukawa K, Kato T, Yato Y, et al. Incidence and risk
factors of adjacent cranial facet joint violation following pedicle screw insertion using cortical bone trajectory technique. Spine. 2016;41(14):E851–6.
12. Matsukawa K, Yato Y, Nemoto O, Imabayashi H,
Asazuma T, Nemoto K. Morphometric measurement of cortical bone trajectory for lumbar pedicle
screw insertion using computed tomography. J Spinal
Disord Tech. 2013;26(6):E248–53.
13. Snyder LA, Martinez-Del-Campo E, Neal MT, et al.
Lumbar spinal fixation with cortical bone trajectory pedicle screws in 79 patients with degenerative
disease: perioperative outcomes and complications.
World Neurosurg. 2016;88:205–13.
14. Kasukawa Y, Miyakoshi N, Hongo M, Ishikawa Y,
Kudo D, Shimada Y. Short-term results of transforaminal lumbar interbody fusion using pedicle screw with
cortical bone trajectory compared with conventional
trajectory. Asian Spine J. 2015;9(3):440–8.
15. Lee GW, Son J-H, Ahn M-W, Kim H-J, Yeom JS. The
comparison of pedicle screw and cortical screw in posterior lumbar interbody fusion: a prospective randomized
noninferiority trial. Spine J. 2015;15(7):1519–26.
16. Rodriguez A, Neal MT, Liu A, Somasundaram A,
Hsu W, Branch CL. Novel placement of cortical bone
trajectory screws in previously instrumented pedicles
for adjacent-segment lumbar disease using CT imageguided navigation. Neurosurg Focus. 2014;36(3):E9.
17. Berjano P, Damilano M, Ismael M, Formica C,
Garbossa D. Erratum to: Minimally invasive PLIF
with divergent, cortical trajectory pedicle screws. Eur
Spine J. 2015;24(5):654–5.
18. Ninomiya K, Iwatsuki K, Ohnishi Y-I, Ohkawa T,
Yoshimine T. Clear zone formation around screws in
the early postoperative stages after posterior lumbar
fusion using the cortical bone trajectory technique.
Asian Spine J. 2015;9(6):884–8.
19. Glennie RA, Dea N, Kwon BK, Street JT. Early clinical results with cortically based pedicle screw trajectory for fusion of the degenerative lumbar spine.
J Clin Neurosci. 2015;22(6):972–5.
20. Cheng WK, Akpolat YT, ønceo÷lu S, Patel S, Danisa
OA. Pars and pedicle fracture and screw loosening
associated with cortical bone trajectory: a case series
and proposed mechanism through a cadaveric study.
Spine J. 2016;16(2):e59–65.
21. Akpolat YT, ønceo÷lu S, Kinne N, Hunt D, Cheng
WK. Fatigue performance of cortical bone trajectory screw compared with standard trajectory pedicle
screw. Spine. 2016;41(6):E335–41.
22. Ueno M, Sakai R, Tanaka K, et al. Should we use
cortical bone screws for cortical bone trajectory?
J Neurosurg Spine. 2015;22(4):416–21.
23. Wray S, Mimran R, Vadapalli S, Shetye SS,
McGilvray KC, Puttlitz CM. Pedicle screw placement
in the lumbar spine: effect of trajectory and screw
29 Cortical Bone Screw Fixation
399
design on acute biomechanical purchase. J Neurosurg
Spine. 2015;22(5):503–10.
24. Ueno M, Imura T, Inoue G, Takaso M. Posterior corrective fusion using a double-trajectory technique (cortical
bone trajectory combined with traditional trajectory)
for degenerative lumbar scoliosis with osteoporosis:
technical note. J Neurosurg Spine. 2013;19(5):600–7.
25. Calvert GC, Lawrence BD, Abtahi AM, Bachus KN,
Brodke DS. Cortical screws used to rescue failed lumbar pedicle screw construct: a biomechanical analysis.
J Neurosurg Spine. 2015;22(2):166–72.
26. Takata Y, Matsuura T, Higashino K, et al. Hybrid technique of cortical bone trajectory and pedicle screwing
for minimally invasive spine reconstruction surgery: a
technical note. J Med Investig. 2014;61(3–4):388–92.
27. Matsukawa K, Yato Y, Imabayashi H, Hosogane N,
Asazuma T, Chiba K. Biomechanical evaluation
of lumbar pedicle screws in spondylolytic vertebrae: comparison of fixation strength between the
traditional trajectory and a cortical bone trajectory.
J Neurosurg Spine. 2016;24(6):1–6.
28. Iwatsuki K, Yoshimine T, Ohnishi Y-I, Ninomiya
K, Ohkawa T. Isthmus-guided cortical bone trajectory for pedicle screw insertion. Orthop Surg.
2014;6(3):244–8.
29. Matsukawa K, Taguchi E, Yato Y, et al. Evaluation of
the fixation strength of pedicle screws using cortical
bone trajectory: what is the ideal trajectory for optimal fixation? Spine. 2015;40(15):E873–8.
30. Matsukawa K, Yato Y, Kato T, Imabayashi H,
Asazuma T, Nemoto K. Cortical bone trajectory
for lumbosacral fixation: penetrating S-1 endplate
screw technique: technical note. J Neurosurg Spine.
2014;21(2):203–9.