Cortical Bone Trajectory Screw for Lumbar Fixation: A Quantitative Anatomic and Morphometric Evaluation

Accepted Manuscript Cortical Bone Trajectory Screw for Lumbar Fixation: A Quantitative Anatomical and Morphometric Evaluation. Laboratory Investigation Mehmet Senoglu, Ali Karadag, Burak Kinali, Baran Bozkurt, Erik H. Middlebrooks, Andrew W. Grande PII:

S1878-8750(17)30460-6

DOI:

10.1016/j.wneu.2017.03.137

Reference:

WNEU 5506

To appear in:

World Neurosurgery

Received Date: 21 January 2017 Revised Date:

27 March 2017

Accepted Date: 28 March 2017

Please cite this article as: Senoglu M, Karadag A, Kinali B, Bozkurt B, Middlebrooks EH, Grande AW, Cortical Bone Trajectory Screw for Lumbar Fixation: A Quantitative Anatomical and Morphometric Evaluation. Laboratory Investigation, World Neurosurgery (2017), doi: 10.1016/j.wneu.2017.03.137. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Senoglu 1 Type of contribution: Anatomic Bases of Radiological and Surgical Original Article, number of references: 16

and Morphometric Evaluation. Laboratory Investigation

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Title: Cortical Bone Trajectory Screw for Lumbar Fixation: A Quantitative Anatomical

Mehmet Senoglu 1, Ali Karadag 1, 2, Burak Kinali 1, Baran Bozkurt 2, Erik H. Middlebrooks 3, Andrew W. Grande 2

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Affiliation:

Department of Neurosurgery, Tepecik Research and Training Hospital, Izmir, Turkey

2

Department of Neurosurgery, University of Minnesota, Minneapolis, Minnesota, USA

3

Department of Radiology, University of Alabama at Birmingham, Birmingham, Alabama, USA

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1

Mehmet Senoglu: MD, Department of Neurosurgery, Tepecik Research and Training Hospital, Izmir, Turkey, [email protected]. Conceiving the idea and writing the manuscript.

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Ali Karadag: -MD, Research Fellow, Department of Neurosurgery, University of Minnesota, Minneapolis, Minnesota, USA.

-MD, Resident, Department of Neurosurgery, Tepecik Research and Training Hospital, Izmir,

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Turkey. [email protected]

Literature search, collected data, revised the manuscript, performed the cadaveric study at

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University of Minnesota Neuroanatomy Lab. Burak Kinali: MD, Resident, Department of Neurosurgery, Tepecik Research and Training Hospital, Izmir, Turkey, [email protected]. Literature search and collected the statistical data. Baran Bozkurt: MD, Department of Neurosurgery, University of Minnesota, Minneapolis, Minnesota, USA, [email protected]. Literature search, collected data.

ACCEPTED MANUSCRIPT Senoglu 2 Erik H. Middlebrooks: MD, Department of Radiology, University of Alabama, Birmingham, AL, USA, [email protected]. Revised the manuscript. Andrew W. Grande: MD, Department of Neurosurgery, University of Minnesota, Minneapolis,

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Minnesota, USA, [email protected]. Edited the manuscript, statistical analysis, and figures.

Corresponding author: Mehmet Senoglu, MD, Department of Neurosurgery, Tepecik Research

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and Training Hospital, Izmir, Turkey

Adress: Tepecik Research and Training Hospital, Yenisehir, Konak, Izmir, Turkey

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Tel: +902324696969, fax: +90 232 433 07 56, e-mail: [email protected] Conflict-of-interest disclosure: The authors declare no competing financial interests and no sources of funding and support, including any for equipment and medications. Running title: Cortical Bone Trajectory Screw for Lumbar Fixation

Abstract Word: 248

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Number of Figures: 5

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Manuscript Text Word: 2684

Number of Tables: 1

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Abstract Objective

Lumbar cortical bone trajectory (CBT) screw constructs are reported as an alternative

method to pedicle screw fixation for minimally invasive spine surgery. The current study explores the CBT technique in further anatomic detail. The primary aims are to evaluate variations in anatomy relevant to CBT screw placement and to determine optimal screw location, trajectory, and length utilizing measures obtained from CT scans.

ACCEPTED MANUSCRIPT Senoglu 3 Methods One-hundred CT scans of the lumbar spine were evaluated, and 14 total measurements were determined for screw entry points, trajectories, and lengths for placement of CBT screws.

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Results

Across all lumbar levels, the mean right pedicle-pars interarticularis junction length

ranged from 7.58-8.37 mm (SD = ±1.18-1.42 mm). The mean left pedicle-pars interarticularis

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junction length was 7.95-8.6 mm (SD = ±1.42-1.74 mm). The pedicle-pars interarticularis

junction from L1 to L5 was deemed too small for a 5 mm diameter CBT screw on the right in

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35%, 24%, 17%, 17%, and 19%, respectively, and on the left in 30%, 17%, 17%, 17%, and 20%, respectively. The average length of a screw placed along the cranial cortical bone of the pedicle measured 27-30.5 mm (± 2.5-3.4 mm) and the angle of the screw with respect to the vertebral body endplate measured 44-48° (± 4.1-6.2°).

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Conclusions

Improved anatomic knowledge relevant to CBT screw placement for lumbar fixation offers the potential to improve outcomes and reduce complications. Further, detailed analysis of the

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anatomy of the pedicle-pars interarticularis junction via preoperative CT can assist in choosing

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the ideal fixation method.

Key Words: Cortical, trajectory, bone, screw, pedicle, pars interarticularis

Abbreviations: CBT, cortical bone screw trajectory

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Senoglu 4

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Introduction

The cortical bone screw trajectory (CBT) technique is a novel lumbar pedicle screw path

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originally reported as an alternative strategy for rigid fixation of the lumbar spine by Santoni, et al. in 2009.1 In previous reports, patients have been successfully treated with the CBT technique in trauma, neoplastic, and degenerative pathologies.1,2

The CBT technique follows a medial-to-lateral path in the transverse plane and a caudal-

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to-cephalad path in the sagittal plane through the pedicle.1 The CBT technique maximizes thread contact with the cortical bone surface and provides increased fixation strength that may improve holding screw strength and minimize loosening.1 Additionally, screw insertion through a medial

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entry point offers advantages to avoid wide exposure of the superior facet joint and to minimize muscle dissection, both providing reduced invasiveness.3 Several studies have validated the

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biomechanical viability of the CBT screw fixation technique.1,4-7 This technique affords better biomechanical stability, fixation strength, and surgical safety while maintaining a minimally invasive profile.6

The current study was undertaken for further exploration of anatomic considerations

when utilizing the CBT technique. Our primary aim was to determine the variability in anatomy for pre-operative assessment prior to CBT screw placement and optimal parameters for screw

ACCEPTED MANUSCRIPT Senoglu 5 entry site, trajectory, and length based on anatomic factors. Materials and Methods We retrospectively evaluated a convenience sample of 100 three-dimensional CT (3D-

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CT) scans of L1-5 obtained in 100 adult patients (55 male/45 female) with a mean age of 36.6 ± 8.1 years (range 21–50 years) presenting to our neurosurgery outpatient clinic between January 2013 and July 2016. Patients were excluded if they had a spine fracture, history of spine surgery,

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infection, tumor, obvious hyperostosis of the facet joint, or underlying spinal deformity.

CT images were acquired in the axial plane with: 512 x 512 matrix; 20 x 20 cm field-of-

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view; and 1.0 mm slice thickness. Axial images were reconstructed into the sagittal and coronal planes using third-party software (AquariusNET, Tera-Recon).

Seven different morphometric measurements were obtained from each subject based on the CBT screw placement technique described by Santoni, et al.1 The assessed measurements are

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illustrated in Figure 1. The measurements were obtained on each side for a total of 14 different data points per subject. These measurements included:

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(1) Parasagittal angle - the angle between the medial-to-lateral cortical bone screw trajectory and the true sagittal plane (defined by the long axis of the spinous process) as

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measured in the axial view

(2) Trajectory of a cranial screw - the angle between a screw theoretically placed to maximize cortical bone contact with the cranial cortical bone of the pedicle and the upper vertebral body endplate (3) Trajectory of a caudal screw - the angle between a screw theoretically placed to maximize cortical bone contact with the caudal cortical bone of the pedicle and the upper

ACCEPTED MANUSCRIPT Senoglu 6 vertebral body endplate (4) Pedicle-pars interarticularis junction length - the oblique anterior-posterior length of the junction between the pedicle and the pars interarticularis as measured in the sagittal

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plane

(5) Length of the pars interarticularis - anterior-posterior length of the pars interarticularis as measured in the sagittal plane

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(6) Length of a cranial screw - the length of a screw theoretically placed to maximize cortical bone contact with the cranial cortical bone of the pedicle

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(7) Length of a caudal screw - the length of a screw theoretically placed to maximize cortical bone contact with the caudal cortical bone of the pedicle Asymmetry was defined as more than a two-millimeter difference in the left and right

Screw Technique

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pedicle-pars interarticularis junction length.

Location of the Entry Point

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The CBT screw optimal entry site was located 1 mm inferior to the transverse process at the junction of the midpoint of the superior articular process. The entry site was approximately 2

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mm medial to the lateral margin of the pars interarticularis. In the left pedicle, the tip of the screw was aimed at the 11-12 o’clock position, when viewed axially, with the long-axis of the screw oriented in the 5 o’clock position. In the right pedicle, the tip of the screw was aimed at the 12-1 o’clock position with the long-axis of the screw oriented at 7 o’clock (Figures 2 and 3).3,6 Screw Trajectory of the CBT

ACCEPTED MANUSCRIPT Senoglu 7 The screw trajectory was defined as the direction from the entry point to the mediolateral midpoint in the reconstructed axial CT plane and the cephalocaudal midpoint in the sagittal plane. 1,3,6 CBT screws were estimated to be approximately 10° lateral in the axial plane and 25°

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cranial in the sagittal plane as described by Matsukawa, et al. (Figures 2 and 3).3,6 Diameter and Length of the CBT

According to previous studies, the CBT technique screw diameter was in the range of

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4.5-5.5 mm and the length was in the range from 30-35 mm.8,9 The surgeon should be careful not to breach the superior endplate, which can result in damage to the disc.2

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Statistical Analysis

Mean, range, and SD were calculated for each of the measures. Results

Data for each of the 14 data points from L1-L5 are shown in Table 1. The mean pedicle-

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pars interarticularis junction length across all levels ranged from 7.58-8.37 mm (SD = ±1.18-1.42 mm) on the right and 7.95-8.6 mm (SD = ±1.42-1.74 mm) on the left (Figure 4). Accounting for a 5.0 mm diameter screw and desire for a minimum of 1 mm bone stock on each side of the

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screw, the pedicle-pars interarticularis junction length from L1 to L5 was too small (< 7 mm) on the right in 35%, 24%, 17%, 17%, and 19%, respectively, and on the left in 30%, 17%, 17%,

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17%, and 20%, respectively. While there were minor differences in mean and standard deviation between sides and across levels, there was notable intra-subject variability. Side-to-side asymmetry (>2 mm) of the pedicle-pars interarticularis junction length from L1 to L5 was detected on 13%, 20%, 31%, 18%, 17% of scans, respectively (Figure 5). The parasagittal angle, based on axial CT, measured from 13.5-15.6° (SD = ± 2.8-3.7°) on the right and 13-15.2° (SD = ± 2.3-3.5°) on the left (Figure 5). The mean trajectory of a

ACCEPTED MANUSCRIPT Senoglu 8 cranial screw across all lumbar levels would measure between 44.0-48.1°(SD = ± 4.4-5.1°) on the right and 44.1-47.9° (SD = ± 4.2-6.2°) on the left. The mean trajectory of a caudal screw

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across all lumbar levels would measure between 30.6-33.9° (SD = ± 3.7-4.6°) on the right and 31.3-39.9° (SD = ± 4.5-6.0°) on the left. The mean cortical bone screw length of a cranial screw ranged from 27-30.5 mm (SD = ± 2.5-3.2 mm) on the right and 27-30.3 mm (SD = ± 3.1-3.9 mm) on the left. The mean screw length of caudal screw ranged from 39.9-36.2 mm (SD = ± 3.2-

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3.6 mm) on the right and 36.1-39.5 mm (SD = ± 3.1-4.3 mm) on the left (Figure 5).

Discussion

CBT is a relatively novel pedicle screw fixation technique that engages the pars and the medial and superior cortices of the pedicle isthmus. CBT was developed as a means of enhancing fixation strength at the pedicle screw–bone interface with minimal soft-tissue dissection. The

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entry point is on the lateral aspect of the pars interarticularis, and its trajectory follows a caudocephalad path sagittally and a laterally directed path in the transverse plane.3 This unique

body.

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screw trajectory maximizes screw contact with dense cortical bone in the pedicle and vertebral

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Biomechanical studies have demonstrated equivalent pullout strength and toggle testing with CBT screws compared with traditional pedicle screw trajectory despite using a screw that is shorter and smaller in diameter.1 Insertional torque, which has been correlated with screw stability, is noted to be 1.7 times higher in CBT compared to the traditional technique by in vivo analysis.6 The CBT has superior fixation strength of an individual screw and sufficient stiffness in flexion and extension loading within a construct. However, the traditional pedicle screw construct is superior to the CBT construct during lateral bending and axial rotation.7 In a recent

ACCEPTED MANUSCRIPT Senoglu 9 cadaveric biomechanical study, CBT fixation provided similar stability as traditional pedicle screw fixation regardless of the presence of interbody support.5 As a result, the CBT pedicle screw technique is a valuable tool to maximize fixation strength in elderly or osteoporotic

testing when compared with the standard pedicle screw.4

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patients.3,5-7 Baluch, et al. found that the CBT screw had more resistance to loosening in fatigue

In addition to the stronger fixation strength, the CBT pedicle screw offers several other

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advantages over the traditional pedicle screw trajectory. First, there is a known risk of canal breach and subsequent neurologic injury with traditional lumbar pedicle screw placement;

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however, this has not been reported in patients undergoing spinal fusion with the CBT technique.3 This should not be a surprise given the medial to lateral and caudal to cephalad trajectory applied in the CBT technique. As such, a lower incidence of postoperative nerve injury is expected.

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Secondly, the screw insertion through a more medial entry point enables a reduction in incision length, extent of muscle dissection, intraoperative retraction, and recovery time. As such, a reduction in perioperative morbidity is suspected given the minimization of approach-

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related trauma, such as reduced iatrogenic facet joint injury and instability at the superior aspect of the surgical exposure, making CBT an attractive option for minimally invasive spine surgery.2

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CBT is particularly advantageous in the lower lumbar spine where the traditional pedicle screw entry point and insertion require more lateral exposure. The advantages of the limited dissection necessary using the CBT technique make it ideal for high-risk patients, including the morbidly obese and diabetic population.1-3,9-12 Likewise, the CBT technique offers an easier route for screw placement in the morbidly obese given the challenge of the traditional transpedicular axis when placed through deep soft tissue.2,13

ACCEPTED MANUSCRIPT Senoglu 10 Thirdly, the lateral trajectory through the pedicle reduces the risk of injury to the medial branch nerve (MBN) that originates from the dorsal rami of each of the lumbar spinal nerves and thereby reduces the incidence of postoperative radiculitis.14 As the anatomic course of the MBN

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passes near the mammillary process, it is vulnerable to injury during traditional pedicle screw insertion.3,14

Lastly, the CBT technique maximizes thread contact with the higher density cortical bone

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providing increased screw purchase and interface strength even though the path through bone is shorter. With the CBT technique, fixation to cortical bone is achieved at four sites: the dorsal,

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posteromedial, and anterolateral sides of the pedicle and the marginal region of the vertebral body.1 In contradistinction, the traditional trajectory fixation involves both strong cortical bone and weaker trabecular bone.1 The greater cortical bone engagement of CBT suggests a particular advantage in the osteoporotic spine.9

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While CBT offers several advantages to traditional approaches, several disadvantages deserve mention. There are some potential risks during screw insertion such as entry point or pedicle fractures due to increased screw diameter, upper nerve root injury from incorrect depth

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of screw penetration or screw trajectory, and lower nerve root injury from insufficient cephalad trajectory since the nerve root lies just caudal to the entry point. Pars fracture is also a theoretical

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risk of the CBT technique given the location of the entry point, in which case placement of a traditional pedicle screw has been recommended.2,3 A thorough understanding of spinal anatomy and accurate screw insertion techniques are essential for decreasing complications.3 Another potential disadvantage of the CBT technique is difficulty with rod placement when used in a hybrid construct since the CBT pedicle screw heads may not line up in the para-sagittal plane with traditional pedicle screw heads.8,13 Nevertheless, Takata et al. reported successful outcomes

ACCEPTED MANUSCRIPT Senoglu 11 in patients with spondylolisthesis undergoing minimally invasive spine fusion with a hybrid construct of CBT pedicle screw at the cephalad level and traditional pedicle screw at the caudal level.8,13

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Our results show that the parasagittal angle, as measured between the cortical bone screw trajectory and the true sagittal plane on axial CT, showed minimal variability ranging from

approximately 13-16°. Matsukawa et al. reported a similar angle of 8-9°.3 However, there was a

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notable difference between the caudocephalad trajectory of a screw placed along the cranial cortex of the pedicle compared with the trajectory of a screw placed along the caudal cortex of

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the pedicle. The cranial screw trajectory measured from an average of ~44-48° compared with an angle of ~31-40° for a caudal screw. Additionally, we found great variability in size and morphology of the pedicle-pars interarticularis junction length (Figure 4). This is important given the potential risks during screw insertion, such as pars fractures, due to increased screw

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diameter. As such, we believe that a pedicle-pars interarticularis junction length of less than 7.0 mm is too thin to safely accommodate a 5.0 mm screw given the preference for a minimum 1 mm bone stock on each side of the CBT screw in case of error. Thus, based on our results, 17-

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35% of pedicles would not be able to accommodate a 5 mm screw. Lastly, no previous studies have reported details about asymmetry of the pedicle-pars interarticularis junction length. We

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found >2 mm asymmetry of the pedicle-pars interarticularis junction length in 13-31% of subjects. The asymmetry is relevant since, at any level, one side may be able to accommodate a CBT screw, but the contralateral side may not. This would necessitate utilizing a hybrid technique. With these issues in mind, decisions about CBT procedures should be based on careful measurements taken during preoperative imaging and close attention to potential

ACCEPTED MANUSCRIPT Senoglu 12 asymmetry when choosing the fixation method. Preoperative CT scan assessed in three standard planes can assist with the choice of fixation technique. To optimize the CBT screw trajectory at each lumbar level, we measured the angle

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between the cortical bone screw trajectory and upper endplate of the vertebral body both for a screw theoretically placed along the cranial cortical bone of the pedicle and one placed along the caudal cortical bone of the pedicle. Our results show the mean cranial CBT screw trajectory was

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between ~44-48° on the right and ~44-48° on the left. The mean caudal CBT screw trajectory was between ~31-34° on the right and ~31-40° on the left (Figure 5). In order to maximize

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cortical bone anchoring and minimize trabecular placement, an ideal CBT screw trajectory was found to be approximately 46° along the cranial cortex of the pedicle (Figure 5). An entry site along the lateral pars is also favored due to the known gradual increase in pars interarticularis thickness from the medial to lateral edge.3,15

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Our results also show that the mean cortical bone screw length of a cranial screw ranged from ~27-30 mm, bilaterally. The mean screw length of a caudal screw ranged from ~36-40 mm on the right and ~36-39 mm on the left (Figure 5). Based on our measurements, 29 mm can serve

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as a safe value for the mean length of pedicle screws from L1 to S1. Our results are similar to previous reports that also found a mean screw length of 29.0 mm (L1-L5) and a maximum screw

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length of 36.8-39.8 mm (L1 to L5).1,3 CBT screws are shorter and smaller in diameter than the traditional trajectory pedicle

screw yet maximize thread contact with higher density cortical bone. The ideal trajectory of the CBT technique maximizes placement within cortical bone while minimizing trabecular bone involvement. This is possible since the CBT technique exploits the anatomy of the vertebral/pedicle complex to obtain a four-point fit between the dorsal cortex at the site of

ACCEPTED MANUSCRIPT Senoglu 13 insertion, the medially oriented posterior pedicle wall, the laterally oriented anterior pedicle wall, and the curvature of the vertebral body margin.16 Absolute contraindications to CBT include a congenital pars defect, lack of cortical bone at the pars secondary to a wide decompression, and

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iatrogenic pars fracture. Relative contraindications include a narrow pars and congenitally small pedicles.16 Conclusions

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Our study presents a detailed assessment of the lumbar CBT pedicle screw entry point, trajectory, length, and diameter utilizing preoperative CT data. We believe the information

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provided in this study is valuable to spine surgeons currently utilizing or planning to utilize the CBT pedicle screw technique. Ideally, the findings of this study will have a significant clinical impact regarding preoperative decision making and intraoperative surgical technique when

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Santoni BG, Hynes RA, McGilvray KC, et al. Cortical bone trajectory for lumbar pedicle

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Mobbs RJ. The "medio-latero-superior trajectory technique": an alternative cortical

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trajectory for pedicle fixation. Orthop Surg. 2013;5:56-59. 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;26:248-253.

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Baluch DA, Patel AA, Lullo B, et al. Effect of physiological loads on cortical and traditional pedicle screw fixation. Spine (Phila Pa 1976). 2014;39:1297-1302.

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Perez-Orribo L, Kalb S, Reyes PM, Chang SW, Crawford NR. Biomechanics of lumbar cortical screw-rod fixation versus pedicle screw-rod fixation with and without interbody support. Spine (Phila Pa 1976). 2013;38:635-641. Matsukawa K, Yato Y, Kato T, Imabayashi H, Asazuma T, Nemoto K. In vivo analysis

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of insertional torque during pedicle screwing using cortical bone trajectory technique. Spine (Phila Pa 1976). 2014;39:240-245.

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bone trajectory: a finite element study. J Neurosurg Spine. 2015;23:471-478. Rodriguez A, Neal MT, Liu A, Somasundaram A, Hsu W, Branch CL, Jr. Novel placement of cortical bone trajectory screws in previously instrumented pedicles for adjacent-segment lumbar disease using CT image-guided navigation. Neurosurg Focus.

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Calvert GC LB, Abtahi AM, Bachus KN, Brodke DS. Cortical screws used to rescue failed lumbar pedicle screw construct: a biomechanical analysis. J Neurosurg Spine.

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Wang J, Zhou Y, Zhang ZF, Li CQ, Zheng WJ, Liu J. Comparison of one-level minimally invasive and open transforaminal lumbar interbody fusion in degenerative and isthmic spondylolisthesis grades 1 and 2. Eur Spine J. 2010;19:1780-1784. Takata Y, Matsuura T, Higashino K, et al. Hybrid technique of cortical bone trajectory

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and pedicle screwing for minimally invasive spine reconstruction surgery: a technical note. J Med Invest. 2014;61:388-392.

Bogduk N, Long DM. The anatomy of the so-called "articular nerves" and their

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relationship to facet denervation in the treatment of low-back pain. J Neurosurg.

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Ivanov AA, Faizan A, Ebraheim NA, Yeasting R, Goel VK. The effect of removing the lateral part of the pars interarticularis on stress distribution at the neural arch in lumbar foraminal microdecompression at L3-L4 and L4-L5: anatomic and finite element

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Table legends:

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(Engl). 2014;127:3808-3813.

Table 1. Table 1. Results of measurements at all lumbar vertebral levels (n = 100).

Figure legends:

ACCEPTED MANUSCRIPT Senoglu 16 Figure 1: The measured parameters. (1) Parasagittal angle (2) Trajectory of a cranial screw (3) Trajectory of a caudal screw (4) Pedicle-pars interarticularis junction length (5) Length of the

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pars interarticularis (6) Length of a cranial screw (7) Length of a caudal screw.

Figure 2: Illustration of cortical bone screw trajectory in the sagittal (A), posterior (B), and axial

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(C) projection.

Figure 3: Sagittal (A) and coronal (B) radiographs showing the cortical bone screw trajectory

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follows a caudocephalad path sagittally and a laterally directed path in the transverse plane. Sagittal CT (C) of the lumbar spine showing acceptable screw length and trajectory in the L1 vertebrae (arrow). Used with permission from Department of Neurosurgery, University of

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Minnesota

Figure 4: Results of measurement for the pedicle-pars interarticularis junction length and pars

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interarticularis length.

Figure 5: Results of measurements for caudal angle, cranial angle, parasagittal angle, caudal

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length, and cranial length.

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L3

L4

L5

1. Parasagittal Angle - Right (°)

8.2 - 30.3 13.94 ±3.45

6.3 - 21.5 13.5 ± 2.75

7.6 - 20.6 13.62 ± 2.92

6.62 - 20.9 13.89 ± 3.03

7.7 - 25.5 15.57 ± 3.67

2. Parasagittal Angle – Left (°)

8.9 - 29.4 14.13 ± 3.02

8.9 - 22.4 13.45 ± 2.6

8.3 - 21.1 13.0 ± 2.34

7.84 - 21.6 14.11 ± 2.77

8.14 - 24.5 15.22 ± 3.53

3. Trajectory of a Cranial Screw - Right (°)

35.0 - 57.5 46.13 ± 4.81

33.7 - 56.6 48.1 ± 4.37

34.5 - 54.9 46.79 ± 4.69

32.3 - 58.8 46.51 ± 4.73

30.8 - 55.9 44.04 ± 5.14

4. Trajectory of a Cranial Screw - Left (°)

36.0 - 56.5 47.39 ± 4.36

34.2 - 58.6 47.89 ± 4.15

24.6 - 58.6 47.4 ± 5.73

30.4 - 57.6 46.93 ± 4.53

27.5 - 56.7 44.14 ± 6.2

5. Trajectory of a Caudal Screw - Right (°)

22.14 - 42.6 32.94 ± 3.99

24.5 - 45.0 33.93 ± 3.84

24.6 - 44.9 33.82 ± 3.69

20.8 - 41.7 32.15 ± 3.97

19.9 - 44.9 30.56 ± 4.63

6. Trajectory of a Caudal Screw - Left (°)

25.3 - 55.3 33.46 ± 4.48

25.9 - 55.1 34.39 ± 4.71

7. Pedicle-Pars Interarticularis Junction Length - Right (mm)

5.35 – 10.6 7.58 ± 1.18

5.68 – 11.22 7.88 ± 1.22

8. Pedicle-Pars Interarticularis Junction Length - Left (mm)

5.32 – 13.04 7.95 ± 1.57

9. Pars Interarticularis Length – Right (mm)

8.41 – 16.22 11.46 ± 1.41

10. Pars Interarticularis Length – Left (mm)

8.63 – 16.24 11.68 ± 1.43

11. Length of a Caudal Screw – Right (mm) 12. Length of a Caudal Screw – Left (mm)

20.8 - 52.3 39.92 ± 5.21

20.4 - 49.4 31.28 ± 6.03

5.5 – 11.0 8.2 ± 1.22

5.03 – 12.82 8.37 ± 1.42

5.02 - 14.37 8.09 ± 1.41

5.32 – 13.66 8.6 ± 1.42

5.63 – 13.49 8.44 ± 1.49

5.07 – 13.66 8.5 ± 1.56

5.43 – 15.9 8.25 ± 1.74

8.47 – 18.35 11.66 ± 1.76

7.5 – 16.13 12.01 ± 1.82

8.37 – 17.0 11.92 ± 1.68

8.37 – 17.0 11.82 ± 1.69

7.9 – 15.7 11.63 ± 1.63

8.4 – 15.82 12.22 ± 1.61

7.5 – 16.43 12.0 ± 1.92

7.5 – 14.64 11.38 ± 1.62

26.76 - 46.67 39.55 ± 3.38

33.37 - 47.42 39.91 ± 3.18

33.33 - 47.94 39.83 ± 3.39

30.01 - 45.96 38.3 ± 3.19

25.4 - 45.79 36.16 ± 3.57

26.37 - 48.3 39.26 ± 3.69

30.21 - 45.74 36.67 ± 3.22

30.81- 45.98 39.46 ± 3.05

25.62 - 50.14 38.75 ± 4.25

23.48 - 45.91 36.12 ± 3.8

22.84 - 39.83 30.45 ± 2.76

24.93 - 37.75 29.87 ± 2.47

21.84 - 35.0 28.98 ± 2.98

14.03 - 36.75 26.98 ± 3.22

23.78 - 44.2 30.29 ± 3.21

20.59 - 40.69 29.97 ± 3.13

20.21 - 39.8 29.6 ± 3.39

20.2 - 39.2 27 ± 3.9

TE D

21.26 - 40.52 29.5 ± 3.23

AC C

13. Length of a Cranial Screw – Right (mm) 14. Length of a Cranial Screw – Left (mm)

M AN U

26.4 - 53.9 34.2 ± 4.78

EP

Minimum, Maximum, Mean±SD

RI PT

L1

SC

Table 1:

23.3 - 39.4 29.66 ± 3.28

Table 2:

ACCEPTED MANUSCRIPT 8.0-8.9 9.0-9.9 10.0-10.9

6.0-6.9

7.0-7.9

11.0-

L1

8-9

27-21

33-24

17-20

11-14

3-3

1-3

L2

5-2

19-15

33-37

25-23

10-12

3-6

5-5

L3

2-5

15-12

32-21

21-32

23-16

5-9

2-5

L4

3-4

14-14

28-21

20-25

10-22

10-7

L5

3-8

16-12

30-27

29-20

11-19

7-6

RI PT

Right-Left 5.0-5.9

5-7

AC C

EP

TE D

M AN U

SC

4-8

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT

Highlights •

In this study, we emphasize that proper anatomical knowledge and surgical experience are absolutely essential for successfully operating the suitable cases for posterior lumbar

•

RI PT

fixation with cortical screws.

Deciding appropriate cases pre-operatively for posterior fixation of lumbar vertebra is very important for better outcome.

SC

This technique was compared with the traditional technique and may be preferred

EP

TE D

M AN U

because of the less complications and faster recovery.

AC C

•

ACCEPTED MANUSCRIPT

Abbreviations CBT, cortical bone screw trajectory;

RI PT

Cm, centimeter; CT, computerized tomography;

SC

L, lumbar; Mm, millimeter;

M AN U

S, sacral; SD, standart deviaton;

AC C

EP

TE D

Three-dimensional, 3D

ACCEPTED MANUSCRIPT

Abbreviations

AC C

EP

TE D

M AN U

SC

RI PT

CBT, cortical bone screw trajectory;

ACCEPTED MANUSCRIPT

Conflict-of-interest disclosure The authors declare no competing financial interests and no sources of funding and support,

AC C

EP

TE D

M AN U

SC

RI PT

including any for equipment and medications.