Neurovascular complications of cervical pedicle screw fixation

Complications associated with subaxial placement of pedicle screws versus lateral mass screws in the cervical spine (C2-T1): systematic review and meta-analysis comprising 4,165 patients and 16,669 screws

Lateral mass screw (LMS) and cervical pedicle screw (CPS) fixation are among the most popular techniques for posterior fusion of the cervical spine. Early research prioritized the LMS approach as the trajectory resulted in fewer neurovascular complications; however, with the incorporation of navigation assistance, the CPS approach should be re-evaluated. Our objective was to report the findings of a meta-analysis focused on comparing the LMS and CPS techniques in terms of rate of various complications with inclusion of all levels from C2 to T1. We conducted a systematic review of PubMed and EMBASE databases with final inclusion criteria focused on identifying studies that reported outcomes and complications for either the CPS or LMS technique. These studies were then pooled, and statistical analyses were performed from the cumulative data. A total of 60 studies comprising 4165 participants and 16,669 screws placed within the C2-T1 levels were identified. Within these studies, the LMS group had a significantly increased odds for lateral mass fractures (odds ratio [OR] = 43.2, 95% confidence interval [CI] = 2.62-711.42), additional cervical surgeries (OR = 5.56, 95%CI = 2.95-10.48), and surgical site infections (SSI) (OR = 5.47, 95%CI = 1.65-18.16). No other significant differences between groups in terms of complications were identified. Within the subgroup analysis of navigation versus non-navigation-guided CPS placement, no significant differences were identified for individual complications, although collectively significantly fewer complications occurred with navigation (OR = 5.29, 95%CI = 2.03-13.78). The CPS group had significantly fewer lateral mass fractures, cervical revision surgeries, and SSIs. Furthermore, navigation-assisted CPS placement was associated with a significant reduction in complications overall.

Anatomical and Imaging Study on the Optimum Entry Point and Trajectory for Anterior Transpedicular Root Screw Placement into the Lower Cervical Spine

Objective

To study the optimum entry point and trajectory for anterior transpedicular root screw (ATPRS) placement into the lower cervical spine (LCS), so as to provide a basis for clinical application.

Methods

A retrospective analysis of cervical CT images of patients who underwent cervical CT examination in the Spinal Surgery of Ningbo No. 6 Hospital from January 2020 to August 2021 was conducted. The data were obtained and modeled. On the coronal plane, the vertebral body (VB) between the anterior midline of cervical vertebral segments C_3-7 and the left P line (by drawing the line parallel to the anterior midline of the VB at the intersection of the anterior edge of the Luschka's joint and the upper endplate) was equally divided into 9 zones (a-i). The ideal entry point and path of cervical ATPRS were designed and recorded. Additionally, 7 cadaveric specimens were selected, and the screw placement parameters were regenerated according to the above methods for screw placement.

Results

Zone i of each segment, with the longest screw length, was the best area for screw placement. In all patients, the horizontal angles of vertebrae C_3-7 in zones a, d, and g, zones b, e, and h, and zones c, f, and i showed a gradually decreasing trend. The sagittal angle range of C_3-7 in all patients showed a gradually increasing trend in zones a-c, d-f, and g-i. The distance from the anterior midline of C_3-7 to the P line increased in all patients, and the distance was longer in males than in females, with statistical significance. Pedicle screws were successfully inserted in all the 7 cadaveric specimens.

Conclusions

ATPRS placement can be used for LCS internal fixation, and the precise screw placement parameters can be simulated by the software, which provides theoretical basis for its future clinical application.

Free-Hand Cervical Pedicle Screw Placement by Using Para-articular Minilaminotomy: Its Feasibility and Novice Neurosurgeons' Experience

STUDY DESIGN.

Retrospective study.

OBJECTIVE.

Cervical pedicle screw (CPS) placement is technically demanding because of the great variation in pedicle size, dimension, and angulations between cervical levels and patients and the lack of anatomical landmarks. This retrospective study was conducted to analyze novice neurosurgeons' experience of CPS placement by using the technique with direct exposure of pedicle via para-articular minilaminotomy.

METHODS.

We retrospectively reviewed 78 CPSs in 22 consecutive patients performed by 2 surgeons. All pedicle screws were inserted under the direct visualization of the pedicle by using para-articular minilaminotomy without any fluoroscopic guidance. We analyzed the direction and grade of pedicle perforation on the postoperative computed tomography scan. The degree of perforation was classified as grade 0 to 3. Grades 0 and 1 were classified as the correct position and the others, as the incorrect position.

RESULTS.

In total, the correct position (grade 0 and 1) was found in 72 (92.3%) screws and the incorrect position (grade 2 and 3) in 6 (7.7%). Among the 16 pedicle perforations (grade 1, 2, and 3 perforations), the directions were lateral in 15 (93.8%) and superior in 1 (6.2%). There were no neurovascular complications related to CPS insertion.

CONCLUSION.

Free-hand CPS placement by using para-articular minilaminotomy seems to be feasible and reproducible.

Morphometric Analysis of Subaxial Cervical Spine Pedicles in a Middle Eastern Population

BACKGROUND

Pedicle screw instrumentation of the posterior cervical spine is the most secure form of fixation available to surgeons. It has not achieved widespread use yet in the Middle East, mostly due to concerns regarding its feasibility in the target population. A detailed morphometric analysis of the lower cervical spine pedicles using computerized tomography (CT) was proposed to address this issue.

METHODS

Two hundred and seventy patients were enrolled in the study. CT scans were reviewed by two experienced assessors, and measurements of pedicle width (PW), height (PH), and transverse angle (TA) were recorded for all patients. Interobserver and intraobserver reliability were calculated using the kappa statistic. Sex differences were also recorded and analyzed. The t test was used to assess for any significant differences in measurements due to sex (P < .05).

RESULTS

The mean PW varied from 4.4 mm in C3 to 6.1 mm in C7. The mean PH was 6.4 mm in C3 and 6.8 mm in C7. Pedicle TA varied from 42 to 51 degrees between the different levels. Sex differences were observed and were statistically significant for PW and PH. Interobserver reliability was high for PW and PH, but was low for TA. Intraobserver reliability was 0.99 for both assessors.

CONCLUSION

This study provides reliable PW and PH measurements and demonstrates that cervical pedicle screw instrumentation is feasible in our local population. Significant variability exists, however, and each patient must be addressed individually for best results.

LEVEL OF EVIDENCE

3.

CLINICAL RELEVANCE

This study shows that the morphology of the subaxial cervical pedicle permits instrumentation in a majority of cases of our target population.

Posterior Transpedicular Screw Fixation of Subaxial Vertebrae: Accuracy Rates and Safety of Mini-laminotomy Technique

Background and Aim:

Posterior cervical transpedicular screw fixation has the strongest resistance to pullout forces compared with other posterior fixation systems. Here, we present a case on the use of this technique combined with a mini-laminotomy technique, which serves as a guide for accurate insertion of posterior cervical transpedicular screws.

Materials and Methods:

We retrospectively analyzed data from 40 patients who underwent this procedure in our clinic between January 2014 and March 2017.

Results:

The study population comprised 27 males (67.5%) and 13 females (32.5%) aged 15–80 years (median, 51.5 years). Surgical indications included trauma (n = 18, 45%), degenerative disease (n = 19, 47.5%), spinal infection (n = 2, 5%), and basilar invagination due to systemic rheumatoid disease (n = 1, 2.5%). In the 18 trauma patients, 14 short-segment (1–2 levels) and 4 long-segment (≥3 levels) posterior cervical instrumentation and fusion procedures were performed. The mini-laminotomy technique was used in all patients to insert, direct, and achieve exact screw fixation in the pedicles. Pedicle perforations were classified as medial or lateral and were also graded. Among the 227 cervical pedicle fixations performed, 48 were at the C3 level, 49 at C4, 60 at C5, 50 at C6, and 20 at C7. Axial computed tomography scan measurements showed that 205 of 227 (90.3%, Grade 0 and 1) screws were accurately placed, whereas 22 (9.69%, Grade 2 and 3) were misplaced. However, no additional neurological injury due to misplacement was observed.

Conclusion:

As negligible complications were observed when performed by experienced surgeons, the mini-laminotomy technique can be safely used for posterior transpedicular screw fixation in the subaxial vertebrae for single-staged fusion.

Is a patient-specific drill template via a cortical bone trajectory safe in cervical anterior transpedicular insertion?

BACKGROUND

This study aimed to develop patient-specific drill templates by computer numerical control or three-dimensional printing via two cortical bone trajectories (CBTs) and to evaluate their efficacies and accuracies in cervical anterior transpedicular insertion.

METHODS

Preoperative CT images of 20 cadaveric cervical vertebrae (C3-C7) were obtained. After image processing, patient-specific drill templates were randomly assigned to be constructed via two CBTs (CBT0 and CBT0.7) and manufactured by two methods (computer numerical control and three-dimensional printing). Guided by patient-specific drill templates, 3.5-mm-diameter screws were inserted into the pedicles. Postoperative CT scans were performed to evaluate the screw deviation in the entry point and midpoint of the pedicle. The screw positions were also graded.

RESULTS

Computer numerical control patient-specific drill templates had a significantly shorter manufacturing time compared to three-dimensional-printed patient-specific drill templates (p < 0.01). Absolute deviations at the entry point and midpoint of the pedicle had no significant differences on the transverse and sagittal planes (p > 0.05). There were no significant differences in screw positions (p = 0.3). However, three screw positions were in grade 3 in CBT0, while the others were in grade 1.

CONCLUSIONS

CBT0.7 appears to be a safe and feasible trajectory for cervical anterior transpedicular insertion. Bio-safe computer numerical control patient-specific drill templates can facilitate cervical anterior transpedicular insertion with good feasibility and accuracy.

Easy method to simplify "freehand" subaxial cervical pedicle screw insertion

Study Design:

Technical note.

Objectives:

The objective of this study is to check out safety and rationality of standardized and fast tricks to select trajectory of subaxial cervical pedicle screw (SCPS) insertion, based on simple angles to bony landmarks.

Materials and Methods:

Stage 1 – Computed tomography (CT)-morphometric analysis of C3–C7 vertebrae of ten patients with cervical degenerative diseases. Stage 2 – SCPS insertion in 6 cadavers, according to the developed technique (59 pedicle screws). Stage 3 – SCPS insertion in 6 patients, according to the developed technique (32 pedicle screws).

Results:

CT-morphometric analysis showed that the average length of C3–C7 pedicle channels was 32 mm, the average angle between a pedicle axis and an axis of contralateral lamina - 180°, the average angle between a pedicle axis and plane of a posterior surface of a lateral mass amounted to 90° and the coordinates of an optimal entry point – 2 mm from a lateral edge and 2 mm from an upper edge of the lateral mass posterior surface. During the cadaveric study, 39 screws had a satisfactory position (66.1%), 7 screws permissible (11.9%), and 13 screws unacceptable (22%). During the clinical study, 26 screws (81.25%) had satisfactory position, 4 (12.5%) had permissible position, and 2 (6.25%) unacceptable position.

Conclusion:

Developed and clinically approved a method for simplicity SCPS insertion is relatively safe and cheap. No doubt, it requires further investigation, but the results of primary analysis allow us to recommend it to wide practical application.

Unplanned Reoperation of Lumbar Spinal Surgery During the Primary Admission: A Multicenter Study Based on a Large Patient Population

STUDY DESIGN

A retrospective study.

OBJECTIVE

The purpose of this study was to identify the rates and reasons, and the risk factors for unplanned reoperation of lumbar spinal surgery during the primary admission in terms of a multicenter and a large patient population study.

SUMMARY OF BACKGROUND DATA

Unplanned reoperation is suggested to be a useful quality indicator for spinal surgery. However, the rates of unplanned reoperation in patients underwent lumbar spinal surgery during the primary admission are not well established.

METHODS

This study was performed to review all the patients who underwent lumbar spinal surgery at three institutions from January 2010 to April 2015. Patients with unplanned reoperations after primary surgery during the same admission were included in this study. The demographics, diagnosis, surgical procedure, and complications of patients were reviewed and statistical analysis was performed to investigate the incidences and risk factors of unplanned revision.

RESULTS

A total of 3936 patients who underwent lumbar spinal surgery from three institutions were reviewed, and 82 (2.08%) required unplanned reoperation during the primary admission because of wound infection (0.94%), screw misplacement (0.53%), cerebrospinal fluid leakage (0.27%), wound hematoma (0.18%), and neurologic deficit (0.15%). For the diagnosis, patients with lumbar spinal spondylolisthesis had a much higher rate of reoperation (4.3%) than those of lumbar stenosis (2.3%), vertebral tumor (2.2%), vertebral fracture (1.2%), and disc herniation (1.1%) with a significant difference (P < 0.001). The revision rate was significantly higher in patients underwent posterior lumbar interbody fusion than those received transforaminal lumbar interbody fusion (P = 0.007).

CONCLUSION

Unplanned reoperation rate of lumbar spinal surgery was 2.08% and the most common reasons for it were wound infection and screw misplacement. Patients with a diagnosis of lumbar spinal spondylolisthesis or who underwent posterior lumbar interbody fusion were more likely to required unplanned reoperation during the primary admission.

LEVEL OF EVIDENCE

4.

Accuracy of 3D fluoroscopy-navigated anterior transpedicular screw insertion in the cervical spine: an experimental study

PURPOSE

The technique of pedicle screw stabilization is finding increasing popularity for use in the cervical spine. Implementing anterior transpedicular screws (ATPS) in cervical spine offers theoretical advantages compared to posterior stabilization. The goal of the current study was the development of a new setting for navigated insertion of ATPS, combining the advantage of reduced invasiveness of an anterior approach with the technical advantages of navigation.

METHODS

20 screws were implanted in levels C3 to C6 of four cervical spine models (SAWBONES(®) Cervical Vertebrae with Anterior Ligament) with the use of 3D fluoroscopy navigation system [Arcadis Orbic 3D, Siemens and VectorVision fluoro 3D trauma software (BrainLAB)]. The accuracy of inserted screws was analyzed according to postoperative CT scans and following the modified Gertzbein and Robbins classification.

RESULTS

20 anterior pedicle screws were placed in four human cervical spine models. Of these, eight screws were placed in C3, two screws in C4, six screws in C5, and four screws in C6. 16 of 20 screws (80 %) reached a grade 1 level of accuracy according to the modified Gertzbein and Robbins Classification. Three screws (15 %) were grade 2, and one screw (5 %) was grade 3. Grade 4 and 5 positions were not evident. Summing grades 1 and 2 together as "good" positions, 95 % of the screws achieved this level. Only a single screw did not fulfill these criteria.

CONCLUSION

The setting introduced in this study for navigated insertion of ATPS into cervical spine bone models is well implemented and shows excellent results, with an accuracy of 95 % (Gertzbein and Robbins grade 2 or better). Thus, this preliminary study represents a prelude to larger studies with larger case numbers on human specimens.

The Ipsilateral Adjacent Laminae: A Reliable Guide in Determining the Direction of Subaxial Cervical Pedicle Axis in the Sagittal Plane

STUDY DESIGN

A retrospective radiographic analysis and applied anatomical study.

OBJECTIVE

The aim of this study was to evaluate the relationships between the ipsilateral lamina/laminae and pedicle axis in the sagittal plane, and the feasibility of free hand pedicle screw placement in subaxial cervical spine without intraoperative fluoroscopic guidance.

SUMMARY OF BACKGROUND DATA

The morphology of subaxial cervical spine pedicle has been studied extensively. However, to our knowledge, no study has specifically evaluated the relationships between the ipsilateral lamina/laminae and pedicle axis in the sagittal plane on computed tomography (CT) reconstruction images.

METHODS

Axial CT images of 70 adult cases were obtained. Multi-directional pedicle axis reconstruction images of subaxial cervical spines were analyzed. Both the angle formed by the direction of ipsilateral lamina to the pedicle axis in the oblique sagittal plane (lamina-pedicle angle, LPA) and the angle formed by the tangential line passing the ipsilateral adjacent outer laminae cortex to the pedicle axis in the oblique sagittal plane (tangential line pedicle angle, TPA) were recorded. On the basis of the radiographic data, a "T"-shaped guiding tool was designed, and the accuracy of free hand subaxial pedicle screw placement using the guiding tool was evaluated in 12 cadavers.

RESULTS

A total of 350 vertebrae were analyzed. Averaged LPA ranged from 72.2 degrees at C3 to 84.2 degrees at C6, averaged TPA ranged from 89.8 degrees at C3 to 90.7 degrees at C6. The TPA showed a high level of consistency close to a right angle. A total of 115 inserted subaxial cervical pedicle screws on 12 cadavers were evaluated. The rate of screw insertion without pedicle wall penetration was 98%, and the rate of pedicle wall penetration of more than 2 mm in the sagittal plane was 0%.

CONCLUSIONS

The TPA serves to be a reliable guide in determining the direction of subaxial cervical pedicle axis in the sagittal plane. Free hand placement of subaxial pedicle screw is feasible under the guidance of the newly designed guiding tool based on TPA.

LEVEL OF EVIDENCE

5.

Posterior Fixation Techniques in the Subaxial Cervical Spine

This article reviews the historical context, indications, techniques, and complications of four posterior fixation techniques to stabilize the subaxial cervical spine. Specifically, posterior wiring, laminar screw fixation, lateral mass fixation, and pedicle screw fixation are among the common methods of operative fixation of the subaxial cervical spine. While wiring and laminar screw fixation are now rarely used, both lateral mass and pedicle screw fixation are technically challenging and present the risk of significant complications if performed incorrectly. With a sound understanding of anatomy and rigorous preoperative evaluation of bony structures, both lateral mass and pedicle screw fixation provide a safe and reliable method for subaxial cervical spine fixation.

Comparing Accuracy of Cervical Pedicle Screw Placement between a Guidance System and Manual Manipulation: A Cadaver Study

Background

The aim of this study was to compare the accuracy of cervical pedicle screw placement between a three-dimensional guidance system and manual manipulation.

Material/Methods

Eighteen adult cadavers were randomized into group A (n=9) and group B (n=9). Ninety pedicle screws were placed into the C3-C7 under the guidance of a three-dimensional locator in group A, and 90 screws were inserted by manual manipulation in group B. The cervical spines were scanned using computed tomography (CT). Parallel and angular offsets of the screws were compared between the two placement methods.

Results

In group A, 90% of the screws were within the pedicles and 10% breached the pedicle cortex. In group B, 55.6% were within the pedicle and 44.4% breached the pedicle cortex. Locator guidance showed significantly lower parallel and angular offsets in axial CT images (P<0.01), and significantly lower angular offset in sagittal CT images (P<0.01) than manual manipulation.

Conclusions

Locator guidance is superior to manual manipulation in accuracy of cervical screw placement. Locator guidance might provide better safety than manual manipulation in placing cervical screws.

Anterior transpedicular screw fixation of cervical spine: Is it safe? Morphological feasibility, technical properties, and accuracy of manual insertion

OBJECT

Due to lack of construct stability of the current anterior cervical approaches, supplemental posterior cervical approaches are frequently employed. The use of an anterior-only approach with anterior transpedicular screws (ATPSs) has been proposed as a means of providing 3-column fixation. This study was designed to investigate the feasibility of anterior transpedicular screw (ATPS) fixation of cervical spine, to obtain the morphological measurements for technical prerequisites, and to evaluate the accuracy of the ATPS using fluoroscopy.

METHODS

The study included both radiological and anatomical investigations. The radiological investigations were based on data from cervical spine CT scans performed in 65 patients. Technical prerequisites of ATPS were calculated using OsiriX for Mac OS. In the anatomical part of the study, 30 pedicles (C3–7) from 6 formalin-preserved cadavers were manually instrumented. Measurements obtained included pedicle width (PW), pedicle height (PH), pedicle transverse angle (PTA), distance of the entry point from the midline (DEPM), and distance of the entry point from the superior endplate (DEPSEP). The authors also analyzed screw position in the manually instrumented vertebrae.

RESULTS

The mean PW and PH values showed a tendency to increase from C-3 to C-7 in both males and females. The means were significantly larger for both PW and PH in males than in females at all levels (p = 0.001). The overall mean PTA value was significantly lower at C-7 (p < 0.0001). The mean value for the distance of entry point from the midline (DEPM) represented a point at the contralateral side of the pedicle for every level except C-7. The mean DEPSEP values showed significant differences between all levels (p < 0.0001). Seven of the 30 screws were identified as breaching the pedicle (23.3%); these screw malplacements were seen at C-3 (3 screws), C-4 (2 screws), and C-5 (2 screws).

CONCLUSIONS

The morphological measurements of this study demonstrated that ATPS fixation is feasible in selected cases. They indicate that ATPS insertion using a fluoroscopy-assisted pedicle axis view is safe at the C-6 and C-7 levels, but the results at the other levels did not prove the safety of this technique.

Morphological study of the posterior osseous structures of subaxial cervical spine in a population from northeastern China

Background

Laminar screws and lateral mass screws have been increasingly used in the treatment of cervical diseases. The purpose of this study is to determine the morphological characteristics of the posterior anatomical structures of the subaxial cervical vertebrae in a northeastern Chinese population.

Methods

Sixty-one consecutive patients underwent cervical spine computed tomography (CT). We analyzed a total of 610 axial images and 61 sagittal images. The following parameters were measured: lamina outer width (LOW), lamina inner width (LIW), lamina axis length (LAL), lamina transverse angle (LTA), lateral mass longitudinal diameter (LMLD), lateral mass transverse diameter (LMTD), sagittal spinous process length (SSPL), axial spinous process length (ASPL), spinal canal transverse diameter (SCTD), spinal canal longitudinal diameter (SCLD), osseous spinal canal area (OSCA), and Pavlov ratio (PR). The participants were classified into male and female groups and developmental canal stenosis (DCS; PR ≤0.75) and non-DCS (NDCS; PR >0.75) groups.

Results

Significant differences were observed among the different vertebral levels for almost all evaluated parameters, except for LTA and OSCA. Statistical differences were found between the right and left sides in all parameters, except for LIW and LOW. All linear parameters, except for SCLD and the angular parameter LTA, significantly differed between the sexes. Significant differences were found between the DCS and NDCS groups in terms of all parameters, except for SCTD.

Conclusions

Various measurements of the posterior structures of subaxial cervical vertebrae differed between the left and right sides, females and males, and the DCS and NDCS groups. Different techniques for lateral mass screw insertion should be used according to different vertebral level. Only C7 laminar may be able to safely accommodate a 2.5-mm translaminar screw. The study data can help doctors to make better surgical decisions and develop more appropriate implants for northeastern Chinese patients.

Analysis of cervical pedicle with reconstructed computed tomography imaging in Korean population: feasibility and surgical anatomy

STUDY DESIGN

We analyzed the anatomy of C3-C6 cervical pedicles with reconstructed computed tomography images.

OBJECTIVES

The objective of the study was to estimate the feasibility and to understand the surgical anatomy in order to reduce pedicle penetration.

SUMMARY OF BACKGROUND DATA

It is necessary to minimize pedicle penetration by anatomic analysis of cervical pedicles. Many studies have been conducted on cervical pedicle anatomy and cervical pedicle screw fixation, yet there are debates about the feasibility and surgical anatomy.

METHODS

Oblique axial and oblique sagittal images were reconstructed from a 1 mm cut computed tomography image. The pedicle transverse diameter, pedicle length, pedicle convergence angle (CA), and pedicle distance were measured on the oblique axial images. The pedicle sagittal diameter, pedicle sagittal angle (SA), and lateral mass index were measured on the oblique sagittal images. The multiple t test was used for statistical analysis.

RESULTS

The averages of the pedicle transverse diameter ranged from 5.79 to 6.19 mm, the pedicle length ranged from 16.24 to 17.56 mm, the CA ranged from 47.49 to 48.86 degrees, the pedicle distance ranged from 22.67 to 24.93 mm, the SA ranged from -15.43 to 19.98 degrees, and the lateral mass index ranged from 0.64 to 1.25.

CONCLUSIONS

Because of a tight safe margin, to reduce pedicle penetration the screw should be inserted along the pedicle. With regard to SA, C3 and C4 have a risk of upper end plate penetration. However, C5 and C6 have a risk of facet joint violation, which needs C4 and C5 inferior articular process removal for screw placement. The entry point at C3 and C4 is near one third of the lateral mass height from the posterior border of the superior articular process at the posterolateral border of the lateral mass. The entry point at C5 is near the posterolateral border of the superior articular process and that at C6 is superior to the posterior border of the superior articular process at a line medial to the posterolateral border of the C5 lateral mass. During insertion, not only CA but even SA should be considered carefully to reduce pedicle penetration.

CT morphometric analysis to determine the anatomical basis for the use of transpedicular screws during reconstruction and fixations of anterior cervical vertebrae

BACKGROUND

Accurate placement of pedicle screw during Anterior Transpedicular Screw fixation (ATPS) in cervical spine depends on accurate anatomical knowledge of the vertebrae. However, little is known of the morphometric characteristics of cervical vertebrae in Chinese population.

METHODS

Three-dimensional reconstructions of CT images were performed for 80 cases. The anatomic data and screw fixation parameters for ATPS fixation were measured using the Mimics software.

FINDINGS

The overall mean OPW, OPH and PAL ranged from 5.81 to 7.49 mm, 7.77 to 8.69 mm, and 33.40 to 31.13 mm separately, and SPA was 93.54 to 109.36 degrees from C3 to C6, 104.99 degrees at C7, whereas, 49.00 to 32.26 degrees from C4 to C7, 46.79 degrees at C3 (TPA). Dl/rSIP had an increasing trend away from upper endplate with mean value from 1.87 to 5.83 mm. Dl/rTIP was located at the lateral portion of the anterior cortex of vertebrae for C3 to C5 and ipsilateral for C6 to C7 with mean value from -2.70 to -3.00 mm, and 0.17 to 3.18 mm. The entrance points for pedicular screw insertion for C3 to C5 and C6 to C7 were recommended -2∼-3 mm and 0-4 mm from the median sagittal plane, respectively, 1-4 mm and 5-6 mm from the upper endplate, with TPA being 46.79-49.00 degrees and 40.89-32.26 degrees, respectively, and SPA being 93.54-106.69 degrees and 109.36-104.99 degrees, respectively. The pedicle screw insertion diameter was recommended 3.5 mm (C3 and C4), 4.0 mm (C5 to C7), and the pedicle axial length was 21-24 mm for C3 to C7 for both genders. However, the ATPS insertion in C3 should be individualized given its relatively small anatomical dimensions.

CONCLUSIONS

The data provided a morphometric basis for the ATPS fixation technique in lower cervical fixation. It will help in preoperative planning and execution of this surgery.