Computed tomography–based determination of a safe trajectory for placement of transarticular facet screws in the subaxial cervical spine

2012 ◽  
Vol 16 (4) ◽  
pp. 334-339 ◽  
Author(s):  
Gregory F. Jost ◽  
Erica F. Bisson ◽  
Meic H. Schmidt
Keyword(s):  
Cervical Spine ◽  
Facet Joint ◽  
Entry Point ◽  
Ct Scans ◽  
Screw Placement ◽  
Exit Point ◽  
Lateral Mass ◽  
Subaxial Cervical Spine ◽  
Clinical Series ◽  
The Mean

Object Placement of transarticular facet screws is one option for stabilization of the subaxial cervical spine. Small clinical series and biomechanical data support their role as a substitute for other posterior stabilization techniques; however, the application of transarticular facet screws in the subaxial cervical spine has not been widely adopted, possibly because of surgeon unfamiliarity with the trajectory. In this study, the authors' objective is to define insertion points and angles of safe trajectory for transarticular facet screw placement in the subaxial cervical spine. Methods Thirty fine-cut CT scans of cervical spines were reconstructed in the multiplanar mode and evaluated for safe transarticular screw placement in the subaxial cervical spine (C2–3, C3–4, C4–5, C5–6, C6–7). As in placement of lateral mass screws, the vertebral artery and exiting nerve root were bypassed posterolaterally. The entry point was set 1 mm medial and 1 mm caudal to the center of the lateral mass. From this entry point, the sagittal angulation was set to traverse the facet joint plane approximately perpendicularly. For the axial angulation, the exit point was set posterolaterally to the transverse process. After ideal insertion angles and screw lengths were identified, the trajectory was simulated on CT scans of 20 different cervical spines to confirm safe screw placement. Results The mean optimal mediolateral insertion angles (± SD) were as follows: 23° ± 5° at C2–3; 24° ± 4° at C3–4; 25° ± 5° at C4–5; 25° ± 4° at C5–6; and 33° ± 6° at C6–7. The mean sagittal insertion angles measured to the sagittal projection of the facet joint space were as follows: 77° ± 10° at C2–3; 77° ± 10° at C3–4; 80° ± 11° at C4–5; 81°± 8° at C5–6; and 100° ± 11° at C6–7. The mean trajectory lengths were 15 ± 2 mm at C2–3; 14 ± 1 mm at C3–4; 15 ± 1 mm at C4–5; 16 ± 2 mm at C5–6; and 23 ± 4 mm at C6–7. Simulation of these insertion angles on 20 different cervical spine CTs yielded a safe trajectory in 85%–95% of spines for C2–3, C3–4, C4–5, C5–6, and C6–7. Conclusions The calculated optimal insertion angles and lengths for each level may guide the safe placement of subaxial cervical transfacet screws.

A radiographic computed tomography–based study to determine the ideal entry point, trajectory, and length for safe fixation using C-2 pars interarticularis screws

2010 ◽  
Vol 12 (6) ◽  
pp. 602-612 ◽  
Author(s):  
Daniel J. Hoh ◽  
Charles Y. Liu ◽  
Michael Y. Wang
Keyword(s):  
Entry Point ◽  
Ct Scans ◽  
Lateral Mass ◽  
Transverse Foramen ◽  
Inferior Aspect ◽  
Significant Difference ◽  
Pars Interarticularis ◽  
Entry Points ◽  
The Mean ◽  
Inferior Edge

Object Effective methods for fixation of the axis include C1–2 transarticular and C-2 pedicle screw placement. Both techniques pose a risk of vertebral artery (VA) injury in patients with narrow pedicles or an enlarged, high-riding VA. Pars screws at C-2 avoid the pedicle, but can cause VA injury with excessively long screws. Therefore, the authors evaluated various entry points and trajectories to determine ideal pars screw lengths that avoid breaching the transverse foramen. Methods Both pars were studied on 50 CT scans (100 total). Various pars lengths were assessed using 2 entry points and 3 trajectories (6 measurements). Entry point A was the superior one-fourth of the lateral mass. Entry point B was 3-mm rostral to the inferior aspect of the lateral mass. Using entry points A and B, Trajectory 1 was the minimum distance to the transverse foramen; Trajectory 2 was the maximum distance to the transverse foramen; and Trajectory 3 was the steepest angle to the pars/C-2 superior facet junction without transverse foramen breach. Results The mean patient age was 46 ± 17 years, and 84% of the CT scans reviewed were obtained in men. There was no significant difference in right or left measurements. Entry point B demonstrated greater pars lengths for each trajectory compared with entry point A (p < 0.0001). For both entry points, Trajectory 3 provided the greatest pars length. Using Trajectory 3 with entry point B, 84, 95, and 99% had a pars length that measured ≥ 18, 16, and 14 mm, respectively. Using Trajectory 3 with Entry point A, only 41, 64, and 87% had a pars length that measured ≥ 18, 16, and 14 mm, respectively. Conclusions Using an entry point 3-mm rostral to the inferior edge of the lateral mass and a trajectory directed toward the superior facet/pars junction, 99% of partes interarticularis in this study would tolerate a 14-mm screw without breach of the transverse foramen.

scholarly journals Subaxial lateral mass prosthesis for posterior reconstruction of cervical spine

2022 ◽  
Author(s):  
Qiang Jian ◽  
Zhenlei Liu ◽  
Wanru Duan ◽  
Fengzeng Jian ◽  
Zan Chen
Keyword(s):  
Cervical Spine ◽  
Joint Angle ◽  
Facet Joint ◽  
Posterior Fixation ◽  
Lateral Mass ◽  
Subaxial Cervical Spine ◽  
Fixation Plate ◽  
The Stability ◽  
Posterior Reconstruction ◽  
Surface Angle

Purpose: To obtain the relevant morphometry of the lateral mass of the subaxial cervical spine (C3-C7) and to design a series of lateral mass prostheses for the posterior reconstruction of the stability of cervical spine. Methods: The computed tomography (CT) scans of healthy volunteers were obtained. RadiAnt DICOM Viewer software (Version 2020.1, Medixant, Poland) was used to measure the parameters of lateral mass, such as height, anteroposterior dimension (APD), mediolateral dimension (MLD) and facet joint angle. According to the parameters, a series of cervical lateral mass prostheses were designed. Cadaver experiment was conducted to demonstrate its feasibility. Results: 23 volunteers with an average age of 30.1 ± 7.1 years were enrolled in this study. The height of lateral mass is 14.1 mm averagely. Facet joint angle, APD and MLD of lateral mass averaged 40.1 degrees, 11.2 mm and 12.18 mm, respectively. With these key data, a lateral mass prosthesis consists of a bone grafting column and a posterior fixation plate was designed. The column has a 4.0 mm radius, 41 degrees surface angle and adjustable height of 13, 15, or 17 mm. In the cadaver experiment, the grafting column could function as a supporting structure between adjacent facets, and it would not violate exiting nerve root (NR) or vertebral artery (VA). Conclusion: This study provided detailed morphology of the lateral mass of subaxial cervical spine. A series of subaxial cervical lateral mass prostheses were designed awaiting further clinical application.

scholarly journals Comparative effectiveness of surgical versus nonoperative management of unilateral, nondisplaced, subaxial cervical spine facet fractures without evidence of spinal cord injury

2014 ◽  
Vol 20 (3) ◽  
pp. 270-277 ◽  
Author(s):  
Bizhan Aarabi ◽  
Stuart Mirvis ◽  
Kathirkamanthan Shanmuganathan ◽  
Alexander R. Vaccaro ◽  
Cassandra J. Holmes ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Cervical Spine ◽  
Motor Vehicle ◽  
Nonoperative Management ◽  
Fracture Plane ◽  
Lateral Mass ◽  
Subaxial Cervical Spine ◽  
Cord Injury ◽  
The Mean ◽  
Stage 1

Object Facet joints are major stabilizers of cervical motion allowing for effortless and pain-free multidimensional cervical spine movements without significant linear or rotational translation, thus minimizing any chance for spinal cord or nerve root impingement. Unilateral, nondisplaced subaxial facet fractures do not meet the conventional criteria for spinal instability under physiological loads. Limited evidence indicates that even with no or minimal displacement, 20%–80% of these fractures fail nonoperative management. The risk factors for instability in isolated nondisplaced subaxial facet fractures remain uncertain. In this retrospective study of prospectively collected data, the authors attempted to identify the predictors of failure in the management of isolated, nondisplaced subaxial facet fractures admitted to their Level I trauma center over a 10-year period. Methods Demographic, clinical, imaging, and follow-up data for 25 patients with unilateral nondisplaced subaxial facet fractures who were managed surgically (n = 10) or nonoperatively (n = 15) were statistically analyzed. Results The mean age of the patients was 38 years, 19 were male, and 21 of the fractures were the result of either motor vehicle accidents or falls. The mean motor score on the American Spinal Injury Association scale was 99.2, and the mean Subaxial Injury Classification (SLIC) severity score was 3 (operated 3.5, nonoperated 2.3). Allen mechanistic classification included 22 compressive-extension Stage 1 and 2 distractive-extension Stage 1 fractures. Subaxial facet fractures involved C-7 in 17 patients (68%), C-6 in 7 (28%), and C-3 in 1 (4%). The anatomical plane of fracture through the lateral mass was sagittal in 12 patients, axial in 8, and coronal in 3 patients. Nondisplaced floating lateral mass injuries were noted in 2 patients. The mean instability score, considering 7 components of the discoligamentous complex on MRI, was 3.2 (operated 3.6, nonoperated 3.0). Ten (40%) of 25 patients in this investigation did not have successful management, 9 in the nonoperated and 1 in the operated group (p = 0.018). Unsuccessful management was significantly greater in younger patients (p = 0.0008), possibly indicating selection bias (p = 0.07, Wilcoxon ranksum test). Fracture plane, instability, and SLIC scores did not play a significant role in treatment failure in this study. Conclusions In this study, surgery was superior to nonoperative management of isolated, nondisplaced, or minimally displaced subaxial cervical spine facet fractures.

scholarly journals Detecting Facet Joint and Lateral Mass Injuries of the Subaxial Cervical Spine in Major Trauma Patients

2015 ◽  
Vol 9 (3) ◽  
pp. 327 ◽  
Author(s):  
Joost Johannes van Middendorp ◽  
Ian Cheung ◽  
Kristian Dalzell ◽  
Hamish Deverall ◽  
Brian J.C. Freeman ◽  
...  
Keyword(s):  
Cervical Spine ◽  
Major Trauma ◽  
Facet Joint ◽  
Trauma Patients ◽  
Lateral Mass ◽  
Subaxial Cervical Spine

scholarly journals The accuracy of a novel pedicle screw insertion technique assisted by a special angular scale in the subaxial cervical spine using lateral mass as a reference marker

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Hang Shi ◽  
Lei Zhu ◽  
Jun Ma ◽  
Yu-Cheng Zhu ◽  
Xiao-Tao Wu
Keyword(s):  
Cervical Spine ◽  
Pedicle Screws ◽  
Ct Images ◽  
Entry Point ◽  
Lateral Mass ◽  
Insertion Technique ◽  
Reference Marker ◽  
Subaxial Cervical Spine ◽  
Angular Scale ◽  
Cervical Pedicle

Abstract Background Posterior cervical pedicle screw (CPS) internal fixation has better biomechanical stability than other posterior cervical fixation methods. However, this technique is limited in clinical practice due to the complex anatomical structure and the adjacent relationship of the cervical pedicle, and the high risk of neurovascular injury. The purpose of this study was to describe a novel subaxial CPS insertion technique assisted by a special angular scale using lateral mass as a reference marker and to evaluate the accuracy of CPS placement and the distribution characteristics of CPS misplacement. Methods A total of 36 patients with subaxial cervical spine diseases who underwent posterior CPS fixation were consecutively selected. The optimal entry point on the posterior surface of the lateral mass was identified on the three-dimensional cervical model reconstructed from preoperative computed tomography (CT) images. The pedicle transverse angle (PTA) and pedicle-lateral mass angle (PLMA) were measured on the transverse and sagittal CT images respectively. The pedicle screws were inserted according to the preoperatively planned entry point and angles. We analysed the postoperative CT images for CPS misplacement rates and perforation directions following the Lee classification. Results Overall, 177 pedicle screws were inserted, of which 119 (67.2%) were classified as grade 0, 43 (24.3%) as grade 1, 12 (6.8%) as grade 2 and 3 (1.7%) as grade 3 by the postoperative CT images. The accuracy rate of CPS placement was 91.5%. Of the 15 misplaced pedicle screws (grades 2 and 3), 11 were lateral pedicle perforations, 3 were superior perforations and 1 was an inferior perforation. There were no neurovascular injuries related to CPS misplacement. Conclusions With our technique, the optimal entry point and two angles (PTA and PLMA) were identified for CPS insertion. The novel CPS insertion technique assisted by a special angular scale provides high accuracy and few complications.

scholarly journals Computed tomography morphometric analysis for lateral mass screw placement in the pediatric subaxial cervical spine

2012 ◽  
Vol 17 (5) ◽  
pp. 390-396 ◽  
Author(s):  
George Al-Shamy ◽  
Jacob Cherian ◽  
Javier A. Mata ◽  
Akash J. Patel ◽  
Steven W. Hwang ◽  
...  
Keyword(s):  
Cervical Spine ◽  
Morphometric Analysis ◽  
Pediatric Patients ◽  
Screw Fixation ◽  
Screw Placement ◽  
Lateral Mass ◽  
Lateral Mass Screw ◽  
Subaxial Cervical Spine ◽  
Screw Length ◽  
Lateral Mass Screws

Object Lateral mass screws are routinely placed throughout the subaxial cervical spine in adults, but there are few clinical or radiographic studies regarding lateral mass fixation in children. The morphology of pediatric cervical lateral masses may be associated with greater difficulty in obtaining adequate purchase. The authors examined the lateral masses of the subaxial cervical spine in pediatric patients to define morphometric differences compared with adults, establish guidelines for lateral mass instrumentation in children, and define potential limitations of this technique in the pediatric age group. Methods Morphometric analysis was performed on CT of the lateral masses of C3–7 in 56 boys and 14 girls. Measurements were obtained in the axial, coronal, and sagittal planes. Results For most levels and measurements, results in boys and girls did not differ significantly; the few values that were significantly different are not likely to be clinically significant. On the other hand, younger (< 8 years of age) and older children (≥ 8 years of age) differed significantly at every level and measurement except for facet angularity. Sagittal diagonal, a measurement that closely estimates screw length, was found to increase at each successive caudal level from C-3 to C-7, similar to the adult population. A screw acceptance analysis found that all patients ≥ 4 years of age could accept at least a 3.5 × 10 mm lateral mass screw. Conclusions Lateral mass screw fixation is feasible in the pediatric cervical spine, particularly in children age 4 years old or older. Lateral mass screw fixation is feasible even at the C-7 level, where pedicle screw placement has been advised in lieu of lateral mass screws because of the small size and steep trajectory of the C-7 lateral mass. Nonetheless, all pediatric patients should undergo high-resolution, thin-slice CT preoperatively to assess suitability for lateral mass screw fixation.

Minimally Invasive Lateral Mass Screw Fixation in the Cervical Spine: Initial Clinical Experience with Long-term Follow-up

Neurosurgery ◽  
2006 ◽  
Vol 58 (5) ◽  
pp. 907-912 ◽  
Author(s):  
Michael Y. Wang ◽  
Allan D.O. Levi
Keyword(s):  
Cervical Spine ◽  
Minimally Invasive ◽  
Screw Fixation ◽  
Ct Scans ◽  
Lateral Mass ◽  
Minimal Access ◽  
Lateral Mass Screw ◽  
Subaxial Cervical Spine ◽  
Lateral Mass Screws

Abstract OBJECTIVE: Lateral mass screw fixation of the subaxial cervical spine has been a major advancement for spinal surgeons. This technique provides excellent three-dimensional fixation from C3 to C7. However, exposure of the dorsal spinal musculature can produce significant postoperative neck pain. The incorporation of a minimal access approach using tubular dilator retractors can potentially overcome the drawbacks associated with the extensive muscle stripping needed for traditional surgical exposures. METHODS: A retrospective analysis was performed on the first 18 patients treated using lateral mass screws placed in a minimally invasive fashion. All patients, except 2 who were lost to follow-up, had a 2-year minimum clinical follow-up. All patients had a computed tomography (CT) scan in the immediate postoperative period to check the positioning of implanted hardware. Operative time, blood loss, and complications were ascertained. Fusion was assessed radiographically with dynamic radiographs and CT scans. RESULTS: Sixteen of the 18 patients underwent successful screw placement. Two patients had the minimal access procedure converted to an open surgery because radiographic visualization was not adequate in the lower cervical spine. Six cases involved unilateral instrumentation and 10 had bilateral screws. A total of 39 levels were instrumented. There were no intraoperative complications, and follow-up CT scans demonstrated no bony violations except in cases where bicortical purchase was achieved. All patients achieved bony fusion. CONCLUSION: A minimally invasive approach using tubular dilator retractors can be a safe and effective means for placing lateral mass screws in the subaxial cervical spine. Up to two levels can be treated in this manner. This approach preserves the integrity of the muscles and ligaments that maintain the posterior tension band of the cervical spine but requires adequate intraoperative imaging.

scholarly journals Utility of intraoperative electromyography in placing C7 pedicle screws

2020 ◽  
Vol 32 (6) ◽  
pp. 891-899 ◽  
Author(s):  
Jonathan J. Rasouli ◽  
Brooke T. Kennamer ◽  
Frank M. Moore ◽  
Alfred Steinberger ◽  
Kevin C. Yao ◽  
...  
Keyword(s):  
Cervical Spine ◽  
Pedicle Screw ◽  
Thoracolumbar Spine ◽  
Pedicle Screws ◽  
Neurological Injury ◽  
Screw Placement ◽  
Pedicle Screw Placement ◽  
Data Set ◽  
Subaxial Cervical Spine ◽  
Increased Risk

OBJECTIVEThe C7 vertebral body is morphometrically unique; it represents the transition from the subaxial cervical spine to the upper thoracic spine. It has larger pedicles but relatively small lateral masses compared to other levels of the subaxial cervical spine. Although the biomechanical properties of C7 pedicle screws are superior to those of lateral mass screws, they are rarely placed due to increased risk of neurological injury. Although pedicle screw stimulation has been shown to be safe and effective in determining satisfactory screw placement in the thoracolumbar spine, there are few studies determining its utility in the cervical spine. Thus, the purpose of this study was to determine the feasibility, clinical reliability, and threshold characteristics of intraoperative evoked electromyographic (EMG) stimulation in determining satisfactory pedicle screw placement at C7.METHODSThe authors retrospectively reviewed a prospectively collected data set. All adult patients who underwent posterior cervical decompression and fusion with placement of C7 pedicle screws at the authors’ institution between January 2015 and March 2019 were identified. Demographic, clinical, neurophysiological, operative, and radiographic data were gathered. All patients underwent postoperative CT scanning, and the position of C7 pedicle screws was compared to intraoperative neurophysiological data.RESULTSFifty-one consecutive C7 pedicle screws were stimulated and recorded intraoperatively in 25 consecutive patients. Based on EMG findings, 1 patient underwent intraoperative repositioning of a C7 pedicle screw, and 1 underwent removal of a C7 pedicle screw. CT scans demonstrated ideal placement of the C7 pedicle screw in 40 of 43 instances in which EMG stimulation thresholds were > 15 mA. In the remaining 3 cases the trajectories were suboptimal but safe. When the screw stimulation thresholds were between 11 and 15 mA, 5 of 6 screws were suboptimal but safe, and in 1 instance was potentially dangerous. In instances in which the screw stimulated at thresholds ≤ 10 mA, all trajectories were potentially dangerous with neural compression.CONCLUSIONSIdeal C7 pedicle screw position strongly correlated with EMG stimulation thresholds > 15 mA. In instances, in which the screw stimulates at values between 11 and 15 mA, screw trajectory exploration is recommended. Screws with thresholds ≤ 10 mA should always be explored, and possibly repositioned or removed. In conjunction with other techniques, EMG threshold testing is a useful and safe modality in determining appropriate C7 pedicle screw placement.

Lateral Radiologic Evaluation of Lateral Mass Screw Placement in the Cervical Spine

Spine ◽  
1998 ◽  
Vol 23 (4) ◽  
pp. 458-462 ◽  
Author(s):  
Nabil A. Ebraheim ◽  
Micheal R. Tremains ◽  
Rongming Xu ◽  
Richard A. Yeasting
Keyword(s):  
Cervical Spine ◽  
Screw Placement ◽  
Lateral Mass ◽  
Lateral Mass Screw ◽  
Radiologic Evaluation

scholarly journals Computed Tomography- and Radiography-Based Morphometric Analysis of the Lateral Mass of the Subaxial Cervical Spine in the Indian Population

2018 ◽  
Vol 12 (1) ◽  
pp. 18-28
Author(s):  
Nirmal D Patil ◽  
Sudhir K Srivastava ◽  
Sunil Bhosale ◽  
Shaligram Purohit
Keyword(s):  
Computed Tomography ◽  
Cervical Spine ◽  
Indian Population ◽  
Tertiary Care ◽  
X Rays ◽  
Lateral Mass ◽  
Cross Sectional ◽  
X Ray ◽  
Subaxial Cervical Spine ◽  
Screw Length

<sec><title>Study Design</title><p>This was a double-blinded cross-sectional study, which obtained no financial support for the research.</p></sec><sec><title>Purpose</title><p>To obtain a detailed morphometry of the lateral mass of the subaxial cervical spine.</p></sec><sec><title>Overview of Literature</title><p>The literature offers little data on the dimensions of the lateral mass of the subaxial cervical spine.</p></sec><sec><title>Methods</title><p>We assessed axial, sagittal, and coronal computed tomography (CT) cuts and anteroposterior and lateral X-rays of the lateral mass of the subaxial cervical spine of 104 patients (2,080 lateral masses) who presented to a tertiary care public hospital (King Edward Memorial Hospital, Mumbai) in a metropolitan city in India.</p></sec><sec><title>Results</title><p>For a majority of the parameters, males and females significantly differed at all levels (<italic>p</italic>&lt;0.05). Females consistently required higher (<italic>p</italic>&lt;0.05) minimum lateral angulation and lateral angulation. While the minimum lateral angulation followed the order of C5&lt;C4&lt;C6&lt;C3, the lateral angulation followed the order of C3&lt;C5&lt;C4&lt;C6. The lateral mass becomes longer and narrower from C3 to C7. In axial cuts, the dimensions increased from C3 to C6. The sagittal cut thickness and diagonal length increased and the sagittal cut height decreased from C3 to C7. The sagittal cut height was consistently lower in the Indian population at all levels, especially at the C7 level, as compared with the Western population, thereby questioning the acceptance of a 3.5-mm lateral mass screw. A good correlation exists between X-ray- and CT-based assessments of the lateral mass.</p></sec><sec><title>Conclusions</title><p>Larger lateral angulation is required for Indian patients, especially females. The screw length can be effectively calculated by analyzing the lateral X-ray. A CT scan should be reserved for specific indications, and a caution must be exercised while inserting C7 lateral mass screws.</p></sec>

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