Accuracy of freehand pedicle screws versus lateral mass screws in the subaxial cervical spine

Imaging guidance using intraoperative CT (O-arm surgical imaging system) combined with a navigation system has been shown to increase accuracy in the placement of spinal instrumentation. The authors describe 4 complex upper cervical spine cases in which the O-arm combined with the StealthStation surgical navigation system was used to accurately place occipital screws, C-1 screws anteriorly and posteriorly, C-2 lateral mass screws, and pedicle screws in C-6. This combination was also used to navigate through complex bony anatomy altered by tumor growth and bony overgrowth. The 4 cases presented are: 1) a developmental deformity case in which the C-1 lateral mass was in the center of the cervical canal causing cord compression; 2) a case of odontoid compression of the spinal cord requiring an odontoidectomy in a patient with cerebral palsy; 3) a case of an en bloc resection of a C2–3 chordoma with instrumentation from the occiput to C-6 and placement of C-1 lateral mass screws anteriorly and posteriorly; and 4) a case of repeat surgery for a non-union at C1–2 with distortion of the anatomy and overgrowth of the bony structure at C-2.

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Screw-related complications in the subaxial cervical spine with the use of lateral mass versus cervical pedicle screws

Journal of Neurosurgery Spine ◽

10.3171/2013.8.spine13136 ◽

2013 ◽

Vol 19 (5) ◽

pp. 614-623 ◽

Cited By ~ 47

Author(s):

Hiroyuki Yoshihara ◽

Peter G. Passias ◽

Thomas J. Errico

Keyword(s):

Cervical Spine ◽

Vertebral Artery ◽

Preoperative Evaluation ◽

Pedicle Screws ◽

Complication Rates ◽

Lateral Mass ◽

Subaxial Cervical Spine ◽

Number Of Patients ◽

Cervical Pedicle ◽

Cervical Pedicle Screws

Object Lateral mass screws (LMS) have been used extensively with a low complication rate in the subaxial spine. Recently, cervical pedicle screws (CPS) have been introduced, and are thought to provide more optimal stabilization of the subaxial spine in certain circumstances. However, because of the concern for neurovascular injury, the routine use of CPS in this location remains controversial. Despite this controversy, however, there are no articles directly comparing screw-related complications of each procedure in the subaxial cervical spine. The purpose of this study was to evaluate screw-related complications of LMS and CPS in the subaxial cervical spine. Methods A PubMed/MEDLINE and Cochrane Collaboration Library search was executed, using the key words “lateral mass screw” and “cervical pedicle screw.” Clinical studies evaluating surgical procedures of the subaxial cervical spine in which either LMS or CPS were used and complications were reported were included. Studies in which the number of patients who had subaxial cervical spine surgery and the number of screws placed from C-3 to C-7 could not be specified were excluded. Data on screw-related complications of each study were recorded and compared. Results Ten studies of LMS and 12 studies of CPS were included in the analysis. Vertebral artery injuries were slightly but statistically significantly higher with the use of CPS relative to LMS in the subaxial cervical spine. Although the use of LMS was associated with a higher rate of screw loosening, screw pullout, loss of reduction, pseudarthrosis, and revision surgery, this finding was not statistically significant. Conclusions Based on the available literature, it appears that perioperative neurological and late biomechanical complication rates, including pseudarthrosis, are similarly low for both LMS and CPS techniques. In contrast, vertebral artery injuries, although statistically significantly more common when using CPS, are extremely rare with both techniques, which may justify their nonroutine use in select cases. Given the paucity of well-designed studies available, this recommendation may be a reflection of deficiencies in the available studies. Surgeons using either technique should have intimate knowledge of cervical anatomy and an adequate preoperative evaluation for each patient, with the final selection based on individual case requirements and anatomical limitations.

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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

Journal of Orthopaedic Surgery and Research ◽

10.1186/s13018-020-02054-1 ◽

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.

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

Journal of Neurosurgery Spine ◽

10.3171/2012.8.spine12767 ◽

2012 ◽

Vol 17 (5) ◽

pp. 390-396 ◽

Cited By ~ 8

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.

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

Neurosurgery ◽

10.1227/01.neu.0000209929.38213.72 ◽

2006 ◽

Vol 58 (5) ◽

pp. 907-912 ◽

Cited By ~ 40

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.

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THE USE OF RIGID INTERNAL FIXATION IN THE SURGICAL MANAGEMENT OF CERVICAL SPONDYLOSIS

Neurosurgery ◽

10.1227/01.neu.0000249222.57709.59 ◽

2007 ◽

Vol 60 (suppl_1) ◽

pp. S1-118-S1-129 ◽

Cited By ~ 17

Author(s):

Brian K. Kwon ◽

Alexander R. Vaccaro ◽

Jonathan N. Grauer ◽

John M. Beiner

Keyword(s):

Cervical Spine ◽

Internal Fixation ◽

Surgical Management ◽

Cervical Spondylosis ◽

Pedicle Screws ◽

Rigid Fixation ◽

Lateral Mass ◽

Regional Anatomy ◽

Rigid Internal Fixation ◽

Lateral Mass Screws

Abstract IN THE SURGICAL management of cervical spondylosis, the application of rigid internal fixation can enhance the immediate stability of the cervical spine. The sophistication of such internal fixation systems and the indications for their use are continuously evolving. A sound understanding of regional anatomy, biomechanics, and kinematics within the cervical spine is essential for the safe and effective application of internal fixation. Numerous options currently exist for anterior cervical plating systems; some lock the screws to the plate rigidly (constrained), whereas others allow for some rotational or translational motion between the screw and plate (semiconstrained). The role of anterior fixation in single and multilevel fusions is still the subject of some controversy. Long anterior cervical reconstructions may require additional posterior fixation to reliably promote fusion. Rigid fixation in the posterior cervical spine can be achieved with lateral mass screws or pedicle screws. Although lateral mass screws provide excellent fixation within the subaxial cervical spine, the regional anatomy of C2 and C7 often make it difficult to place such screws, and pedicle screws at these levels are advocated. Pedicle screws achieve fixation into both the anterior and posterior column and are arguably the most stable form of rigid internal fixation within the cervical spine. Familiarity with these internal fixation techniques can be an extremely valuable tool for the spine surgeon managing these degenerative disorders of the cervical spine.

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Using the Screw Sock as a Simple Method to Salvage Stripped Lateral Mass Screws in the Subaxial Cervical Spine

The Spine Journal ◽

10.1016/j.spinee.2011.08.402 ◽

2011 ◽

Vol 11 (10) ◽

pp. S168-S169

Author(s):

Ryan Siskey ◽

Joshua Auerbach ◽

Christophe Geisert ◽

Kathrin Ellfeldt

Keyword(s):

Cervical Spine ◽

Lateral Mass ◽

Simple Method ◽

Subaxial Cervical Spine ◽

Lateral Mass Screws

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Pedicle Screws Can be 4 Times Stronger Than Lateral Mass Screws for Insertion in the Midcervical Spine

Journal of Spinal Disorders & Techniques ◽

10.1097/bsd.0b013e31824e65f4 ◽

2014 ◽

Vol 27 (2) ◽

pp. 80-85 ◽

Cited By ~ 17

Author(s):

Zenya Ito ◽

Kosaku Higashino ◽

Satoshi Kato ◽

Sung Soo Kim ◽

Eugene Wong ◽

...

Keyword(s):

Pedicle Screws ◽

Lateral Mass ◽

Lateral Mass Screws

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Utility of intraoperative electromyography in placing C7 pedicle screws

Journal of Neurosurgery Spine ◽

10.3171/2019.11.spine191120 ◽

2020 ◽

Vol 32 (6) ◽

pp. 891-899 ◽

Cited By ~ 1

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.

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

Asian Spine Journal ◽

10.4184/asj.2018.12.1.18 ◽

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>This was a double-blinded cross-sectional study, which obtained no financial support for the research.</sec><sec><title>Purpose</title>To obtain a detailed morphometry of the lateral mass of the subaxial cervical spine.</sec><sec><title>Overview of Literature</title>The literature offers little data on the dimensions of the lateral mass of the subaxial cervical spine.</sec><sec><title>Methods</title>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.</sec><sec><title>Results</title>For a majority of the parameters, males and females significantly differed at all levels (<italic>p</italic><0.05). Females consistently required higher (<italic>p</italic><0.05) minimum lateral angulation and lateral angulation. While the minimum lateral angulation followed the order of C5<C4<C6<C3, the lateral angulation followed the order of C3<C5<C4<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.</sec><sec><title>Conclusions</title>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.</sec>

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