Anatomical variations of the vertebral artery segment in the lower cervical spine: analysis by three-dimensional computed tomography angiography

Sizes of the transverse foramina correlate with blood flow and dominance of vertebral arteries

BACKGROUND CONTEXT

Knowing the side of the dominant vertebral artery (VA) may be of utmost importance if the VAs are at risk during spine surgery. Determination of the size of VAs is obtained by using Doppler ultrasonography or angiography. Because VA is the main anatomic structure occupying the transverse foramina (TF), it may be assumed that size of TF and blood flow of VAs should be proportional.

PURPOSE

To investigate if there is a correlation between the sizes of TF and the flow of VAs and determine the diagnostic accuracy of measuring TF to predict dominant side of VA. The specific hypothesis was that the larger side of TF corresponds to the side of the dominant VA.

STUDY DESIGN

This is a morphologically based, prospectively designed, single-center study. Thirty patients (14 male, 16 female) who were treated for degenerative spinal pathologies were included. Patients with cervical fractures, occluded VA, prominent degenerative changes affecting TF, deformity, or previous cervical instrumentation were excluded from the study.

OUTCOME MEASURES

In all patients, computed tomography of the cervical spine and Doppler ultrasonography of VAs were obtained for morphometric analysis.

METHODS

Axial computed tomography cuts at the C6 vertebral level were taken. Two measurements were performed for each foramen: its right to left width and its anteroposterior depth. Blood flow volumes of bilateral VAs were measured using color Doppler.

RESULTS

Diameters of TF ranged between 2.2 and 7 mm, and its width was generally slightly larger than the depth. Transverse foramina were always asymmetric, with no right or left side preference. There was a strong correlation between TF diameters and blood flow of VAs. Between TF width and VA blood flow, the Pearson correlation coefficient was 0.59 (p=.001) for right side and 0.72 for left side (p<.0001). The side of the larger TF matched with the side of dominant VA in 28 of 30 cases (93.3%) (p<.0001). The agreement between the dominant VA and the larger side of TF was almost perfect (Kappa=0.087, p<.0001).

CONCLUSIONS

There was strong correlation between TF diameters and VA blood volume. Our results suggest that TF diameter of C6 level can be used to predict the side of the dominant VA reliably.

Vertebral artery anomaly and injury in spinal surgery

STUDY DESIGN

Systematic review.

STUDY RATIONALE

The purpose of this review is to further define the published literature with respect to vertebral artery (VA) anomaly and injury in patients with degenerative cervical spinal conditions.

OBJECTIVES

In adult patients with cervical spine or degenerative cervical spine disorders receiving cervical spine surgery, what is the incidence of VA injury, and among resulting VA injuries, which treatments result in a successful outcome and what percent are successfully repaired?

MATERIALS AND METHODS

A systematic review of pertinent articles published up to April 2013. Studies involving traumatic onset, fracture, infection, deformity or congenital abnormality, instability, inflammatory spinal diseases, or neoplasms were excluded. Two independent reviewers assessed the level of evidence quality using the Grades of Recommendation Assessment, Development and Evaluation criteria; disagreements were resolved by consensus.

RESULTS

From a total of 72 possible citations, the following met our inclusion criteria and formed the basis for this report. Incidence of VA injuries ranged from 0.20 to 1.96%. None of the studies reported using preoperative imaging to identify anomalous or tortuous VA. Primary repair and ligation were the most effective in treating VA injuries.

CONCLUSION

The incidence of VA injuries in degenerative cervical spinal surgery might be as high as 1.96% and is likely underreported. Direct surgical repair is the most effective treatment option. The most important preventative technique for VA injuries is preoperative magnetic resonance imaging or computed tomography angiographic imaging to detect VA anomalies. The overall strength of evidence for the conclusions is low.

Variance of cervical vertebral artery measured by CT angiography and its influence on C7 pedicle anatomy

STUDY DESIGN

Observational study using a retrospective single-institute database.

OBJECTIVE

To investigate the variance of the vertebral artery (VA) V2 segment and the anatomical features of the C7 pedicle with or without VA entry based on computed tomographic (CT) angiography in 919 consecutive Japanese subjects.

SUMMARY OF BACKGROUND DATA

Generally, the level of the VA entrance into the transverse foramen is assumed to be C6. Therefore, surgeons tend to pay less attention to VA injury when inserting a C7 pedicle screw. However, anomalies at C7 surely exist and are considered to be 1 of the major risk factors for VA injury during posterior instrumentation.

METHODS

Subjects who underwent contrast-enhanced CT or CT angiography from November 2011 to October 2012 were eligible. The entrance into the transverse foramen was reviewed. In addition, anatomical features of C7 with or without VA entrance were measured.

RESULTS

A total of 919 subjects with a mean age of 56.1 years were surveyed. From among 1838 VA courses, VA entered the C6 transverse foramen in 95.6% of specimens (1757 of 1838 VA courses). Sixty-seven of 919 subjects (7.3%) had a unilateral anomaly and 7 (0.8%) had a bilateral anomaly. An abnormal level of entrance was observed in 8.1% of subjects (74 of 919 patients), and 4.4% of specimens (81 of 1838 VA courses), with a level of entrance into the C4, C5, or C7 transverse foramen in 0.5% (n = 10), 3.1% (n = 57), and 0.8% (n = 14) of all specimens, respectively. C7 transverse foramen with a VA entrance was wider in those without a VA entrance, and abnormal cases frequently showed an uneven transverse foramen. Therefore, the C7 pedicle diameter with abnormal VA entrance was significantly narrower in those without VA entrance (P < 0.01; t test).

CONCLUSION

CT angiography is recommended in cases with an uneven transverse foramen for confirming vascular anomaly.

LEVEL OF EVIDENCE

2.

A biomechanical comparison of three different posterior fixation constructs used for c6-c7 cervical spine immobilization: a finite element study

The intralaminar screw construct has been recently introduced in C6–C7 fixation. The aim of the study is to compare the stability afforded by three different C7 posterior fixation techniques using a three-dimensional finite element model of a C6–C7 cervical spine motion segment. Finite element models representing three different cervical anchor types (C7 intralaminar screw, C7 lateral mass screw, and C7 pedicle screw) were developed. Range of motion (ROM) and maximum von Mises stresses in the vertebra for the three screw techniques were compared under pure moments in flexion, extension, lateral bending, and axial rotation. ROM for pedicle screw construct was less than the lateral mass screw construct and intralaminar screw construct in the three principal directions. The maximum von Misses stress was observed in the C7 vertebra around the pedicle in all the three screw constructs. Maximum von Mises stress in pedicle screw construct was less than the lateral mass screw construct and intralaminar screw construct in all loading modes. This study demonstrated that the pedicle screw fixation is the strongest instrumentation method for C6–C7 fixation. Pedicle screw fixation resulted in least stresses around the C7 pedicle-vertebral body complex. However, if pedicle fixation is not favorable, the laminar screw can be a better option compared to the lateral mass screw because the stress around the pedicle-vertebral body complex and ROM predicted for laminar screw construct was smaller than those of lateral mass screw construct.

Preoperative evaluation of the vertebral arteries and posterior portion of the circle of Willis for cervical spine surgery using 3-dimensional computed tomography angiography

STUDY DESIGN

A retrospective analysis using prospectively collected data from 3-dimensional computed tomography angiography (3D-CTA).

OBJECTIVE

To investigate the frequency of anomalous vertebral arteries (VA) and variations of the posterior portion of the circle of Willis (PPCW) using 3D-CTA for preventing perioperative iatrogenic vascular complications.

SUMMARY OF BACKGROUND DATA

Some studies have reported that preoperative 3D-CTA is useful for determining the VA blood flow in the cervical spine. However, preoperative 3D-CTA has not been used for evaluating PPCW, which functions as vessels collateral to the basilar artery in the case of iatrogenic VA injury.

METHODS

The study included 100 consecutive patients (61 males and 39 females; mean age, 60.4 ± 15.4 yr; range, 11-86 yr) who underwent cervical decompression and/or instrumentation between April 2008 and May 2012. We measured the diameters of the VA (VAD), posterior communicating artery (PCOMD), first segment of the posterior cerebral artery (P1D), and basilar artery (BAD) twice and determined the frequency of anomalous VA and PPCW variations.

RESULTS

Hypoplastic VA, hypoplastic PCOM, and hypoplastic P1 were detected in 11 (11.0%), 81 (81.0%), and 13 patients (13.0%), respectively. Hypoplastic PCOM-P1 and hypoplastic basilar artery were observed in 87 (87.0%) and 3 patients (3.0%), respectively. Overall, 47 patients (47.0%) possessed some degree of abnormal VA blood flow.There were 7 patients (7.0%) with both unilaterally hypoplastic VA and bilaterally hypoplastic PCOM-P1s, in whom iatrogenic VA injury on the dominant side could have caused lethal vascular complications. We termed the hypoplastic VA of the contralateral side without collateral vessels as "critical VA."

CONCLUSION

The VAs and PPCW vary considerably. Preoperative 3D-CTA provides important information for preventing tragic vascular complications caused by iatrogenic VA injury. Taking the risk of radiation into consideration, we recommend this method for patients at the highest risk for iatrogenic VA injury.

Congenital variations of the upper cervical spine and their importance in preoperative diagnosis. A case report and a review of the literature

Several variations of the bony and vascular anatomy around the first and second cervical vertebrae have been reported. Failure to recognise these variations can complicate operations on the upper cervical spine. We present a patient with recent onset of cervical myelopathy due to stenosis at the C3-4 level. Preoperative evaluation identified Klippel-Feil syndrome with cervical fusion of C2-3, aplasia of posterior arch of C1, anomalous vertebral artery course and a "ponticulus posticus" of C2. The combination of these variations in a Klippel-Feil syndrome patient has never been reported. Thus, we recommend a thorough preoperative imaging evaluation, with CT scan and CT angiography or DSA, in addition to plain radiographs. This evaluation is imperative, before a cervical spine surgery, allowing a better understanding of the anatomy, in order to minimise the risks of misplacement of cervical instrumentation especially in such patients.

Medial loop of v2 segment of vertebral artery causing compression of proximal cervical root

Objective

It is rare that the medial loop in the V2 segment of the vertebral artery (VA) causes compression of the proximal cervical root of the spinal cord without leading to bony erosion and an enlarged foramen. We evaluated the clinical significance and incidence of the medial loop in the V2 segment of the VA.

Methods

We reviewed the records from 1000 consecutive patients who had undergone magnetic resonance imaging evaluation of the cervical spine between January 2005 and January 2008. The inclusion criteria were that over a third of the axial aspect of the VA located in the intervertebral foramen was inside the line between the most ventral points of the bilateral lateral mass, and that the ipsilateral proximal root deviated dorsally because of the medial loop of the VA. We excluded cases of bone erosion, a widened foramen at the medial loop of the VA, any bony abnormalities, tumors displacing VA, or vertebral fractures. The medical records were reviewed retrospectively to search for factors of clinical significance.

Results

In six patients (0.6%), the VA formed a medial loop that caused compression of the proximal cervical root. One of these patients had the cervical radiculopathy that developed after minor trauma but the others did not present with cervical radiculopathy related to the medial loop of the VA.

Conclusion

The medial loop of the VA might have a direct effect on cervical radiculopathy. Therefore, this feature should be of critical consideration in preoperative planning and during surgery.

A Quantitative Comparison of the Vertebral Artery and Transverse Foramen Using CT Angiography

Background and Purpose

The vertebral artery (VA) is important for the development of the transverse foramen (TF). Most studies of these structures have focused on anatomical anomalies. Therefore, we investigated quantitatively the association between the relative sizes of the TF and VA.

Methods

We recruited a consecutive series of subjects who underwent CT angiography to estimate the relative sizes of the VA and TF in axial source images. Two neurologists independently reviewed the axial CT images of 208 patients who had no history of transient ischemic attack or stroke. Averaged areas of the VA and TF were defined by the sum of the areas at each level from C3 to C6, divided by 4. Correlation analyses were adjusted for age, sex, and vascular risk factors.

Results

The mean age of the subjects was 53 years. The interobserver and intraobserver reliabilities of TF size were good. There was a linear relationship between the sizes of the VA and TF on each side (right side: r²=0.58, p<0.001; left side: r²=0.62, p<0.001). The area of the VA was significantly associated with that of the TF after adjusting for vascular risk factors.

Conclusions

The size of the VA is strongly and linearly correlated with the size of the TF. These findings suggest that measurement of the TF and VA with CT angiography is a reliable method for evaluating VA diseases, and may provide new insight into the differentiation between VA hypoplasia and atherosclerosis of the VA.

Anthropometric assessment of cervical neurovascular structures using CTA to determine zone-specific vulnerability to penetrating fragmentation injuries

AIM

To determine military-specific cervical neurovascular and external anthropometric data to scale future numerical injury models of the neck and improve body armour design with a view to prevention or mitigation of combat neck injury.

MATERIALS AND METHODS

Contrast-enhanced computed tomography (CT) angiograms of 50 UK servicemen were analysed. Mean diameters and distances from the skin surface were determined for the carotid artery (CA), internal jugular vein (IJV), vertebral artery (VA) and spinal cord (SC) at the three surgical neck zones. Horizontal neck circumference at C6 and three potential vertical cervical anthropometric measurements were analysed to determine which had the least variability between subjects.

RESULTS

The diameters of cervical vascular structures are greater and the vessels more superficial as the anatomical plane moves caudally. The SC and VA are better protected than the IJV and CA due to their greater depth and bony coverage, except for the VA in zone 1.

CONCLUSION

Future cervical anthropometric assessments should use the vertical angle of mandible to mid-claviclular distance in combination with the horizontal neck circumference as these demonstrated the least variability. Cervical neurovascular structures are least vulnerable posterosuperiorly and therefore extending the posterior aspect of a ballistic helmet inferiorly or adding a nape protector would appear to be less justified. Cervical vessels are most vulnerable in zone 1 and a circumferential collar of ballistic material at least 75 mm high would cover this area in 95% of this population.

Computerized tomographic morphometric analysis of the cervical spine

Background:

Detailed knowledge of cervical canal and transverse foramens’ morphometry is critical for understanding the pathology of certain diseases and for proper preoperative planning. Lateral x-rays do not provide the necessary accuracy. A retrospective morphometric study of the cervical canal was performed at the authors’ institution to measure mean dimensions of sagittal canal diameter (SCD), right and left transverse foramens’ sagittal (SFD) and transverse (TFD) diameters and minimum distance between spinal canal and transverse foramens (dSC-TF) for each level of the cervical spine from C1-C7, using computerized tomographic scans, in 100 patients from the archives of the Emergency Room.

Results:

Significant differences for SCD were detected between C1 and the other levels of the cervical spine for both male and female patients. For the transverse foramen, significant differences in sagittal diameters were detected at C3, C4, C5 levels. For transverse diameters, significant differences at C3 and C4 levels. A significant difference of the distance between the transverse spinal foramen and the cervical canal was measured between left and right side at the level of C3. This difference was equally observed to male and female subjects.

Conclusion:

CT scan can replace older conventional radiography techniques by providing more accurate measurements on anatomical elements of the cervical spine that could facilitate diagnosis and preoperative planning, thus avoiding possible trauma to the vertebral arteries during tissue dissection and instrument application.

Esophageal and vertebral artery injuries during complex cervical spine surgery--avoidance and management

Vertebral artery and esophageal injuries are rare but feared complications of cervical spine surgery. Appropriate understanding of treatment algorithms for prompt intervention in the event of a vertebral artery injury minimizes the risk of exsanguination and/or profound neurologic consequences. Esophageal injuries are often more subtle, and although intraoperative injuries can sometimes be diagnosed at the time of surgery, they frequently do not present until the week after surgery. They can additionally be seen as a late complication of instrumentation usage and/or failure. Expedient diagnosis and management of these injuries minimize their impact and allow for optimal treatment outcome.

Vertebral artery injury during cervical discectomy and fusion in a patient with bilateral anomalous arteries in the disc space: case report

OBJECTIVE

Our goal was to increase the safety of anterior cervical discectomy, a routine surgery performed by neurosurgeons worldwide, in the face of vertebral artery (VA) anomalies.

CLINICAL PRESENTATION

A 59-year-old woman had an intraoperative injury of the left VA during elective anterior cervical discectomy and fusion from C3 to 7. Retrospective analysis of her magnetic resonance images showed bilateral anomalous VAs. Intervention postoperatively, a pseudoaneurysm developed that was subsequently coiled. The patient underwent embolization of the pseudoaneurysm and sacrifice of the parent vessel by endovascular neurosurgical techniques. She had no neurological sequelae but did have some difficulty swallowing.

CONCLUSION

Radiologists, neuroradiologists, and surgeons should note the location and course of the VA in their routine evaluation of cervical magnetic resonance images. Neuroradiologists should alert surgeons to the possibility of anomalous VAs that are at risk of injury during surgery. Ultimately, it remains the responsibility of the surgeon to carefully review the images, assess for vascular anomalies, and plan the surgery accordingly.

Detection of anomalous vertebral arteries by ultrasound as an alternative to radiological methods

In order to examine 'ultrasound' approach in detecting the course of the vertebral artery (VA) and its anomalies important for neck surgery. An observational study with retrospective analysis of ultrasound images. 500 VAs on 250 3D CT angiographies and 500 ultrasound images performed on the same set of patients were analyzed. The relationship between the extraosseous portions of the VA to the neck organs with a special emphasis to the thyroid gland area, and the abnormal position of the VA were detected. Ultrasound and CT 3D images were compared. Ultrasound detected that 29 out of 500 VAs were anomalous (5.8%), 3D CT detected 30 cases. These anomalies were found in 22 patients (8.8%) (23 for 3D CT; 9.2%), in 7 (31.8%) of them bilaterally. An abnormal level of entrance (C3, C4, and C5) was observed in all anomalous cases. An additional case detected by 3D CT indicated C7 level of entrance. The ultrasound data correspond the CT data in 96.7% of cases. In ten cases (33.3%) the anomalous VA run close to the thyroid gland even touching the lower pole (16.7%; n = 5) or the upper pole (10.0%; n = 3) of the gland. In ten cases (33.3%) the anomalous VA crossed common carotid artery and the internal jugular vein by a way of a median loop. The incidence of anatomic variations of the VA is significant. Preoperative ultrasound investigation allows precise identification of anomalous VAs. Radiation-free ultrasound investigation of blood vessels is as precise as CT 3D imaging.

Two case presentations and surgical management of Bow Hunter's syndrome associated with bony abnormalities of the C7 vertebra

Bow Hunter's syndrome is a condition in which patients experience vertebrobasilar symptoms on head turn. It may be a consequence of intrinsic factors such as atherosclerosis, or it may be secondary to mechanical compression. Most commonly, this occurs at the level of C2 or above. We present two rare cases of Bow Hunter's syndrome secondary to mechanical compression at the level of C7. Discussed are the anatomic conditions leading to this syndrome in these two patients, the methodology for confirming the diagnosis, and the successful management by partial resection of the transverse processes compressing the vertebral arteries.

Vertebral artery anatomy: a review of two hundred fifty magnetic resonance imaging scans

STUDY DESIGN

The aim of this study is to characterize the anatomy of vertebral arteries using magnetic resonance imaging scans of 250 consecutive patients.

OBJECTIVES

To document the prevalence of midline vertebral artery (VA) migration in a subgroup of patients presenting with neck pain, radiculopathy, or myelopathy and to identify the course of the VA through the TFs.

SUMMARY OF BACKGROUND DATA

Knowledge of VA anomalies and their respective prevalence may help surgeons decrease the incidence of iatrogenic injury to this artery.

METHODS

In this retrospective review of 281 consecutive patients, who had an magnetic resonance imaging for axial neck pain, radiculopathy, or myelopathy, anatomic measurements were obtained from C2 to C7.

RESULTS

The observed VA anomalies can be classified into following 3 main groups: (1) intraforaminal anomalies-midline migration, (2) extraforaminal anomalies, and (3) arterial anomalies. Midline migration of the VA was identified in 7.6% (19/250) of patients. The etiology can be degenerative or traumatic. It is important to note that the pattern of medial migration was clockwise rotation from caudal to cephalad and was present in all of our patients with anomalous arteries. Additionally, at C6, only 92% (460/500) of VAs were located within their respective transverse foramens and hypoplastic VAs were identified in 10% (25/250) of patients.

CONCLUSION

Anomalies that must be considered before surgery include interforamenal anomalies, extraforamenal anomalies, and arterial anomalies. The intraforaminal anomalies involve midline migration, which places the VA at direct risk during corpectomy. Extraforaminal anomalies are related to VAs entering the transverse foramen at a level other than C6, which can increase the risk of injury during the anterior approach to the cervical spine. Arterial anomalies can be fenestrated, hypoplastic, or absent. These raise concern with the ability to maintain cerebral perfusion in the setting of damage to one of the VAs with the presence of contralateral arterial abnormality.

C7 posterior fixation using intralaminar screws : early clinical and radiographic outcome

OBJECTIVE

The use of segmental instrumentation technique using pedicle screw has been increasingly popular in recent years owing to its biomechanical stability. Recently, intralaminar screws have been used as a potentially safer alternative to traditional fusion constructs involving fixation of C2 and the cervicothoracic junction including C7. However, to date, there have been few clinical series of C7 laminar screw fixation in the literature. Thus, the purpose of this study is to report our clinical experiences using C7 laminar screw and the early clinical outcome of this rather new fixation technique.

METHODS

Thirteen patients underwent C7 intralaminar fixation to treat lesions from trauma or degenerative disease. Seventeen intralaminar screws were placed at C7. The patients were assessed both clinically and radiographically with postoperative computed tomographic scans.

RESULTS

There was no violation of the screw into the spinal canal during the procedure and no neurological worsening or vascular injury from screw placement. The mean clinical and radiographic follow up was about 19 months, at which time there were no cases of screw pull-out, screw fracture or non-union. Complications included two cases of dorsal breech of intralaminar screw and one case of postoperative infection.

CONCLUSION

Intralaminar screws can be potentially safe alternative technique for C7 fixation. Even though this technique cannot be used in the cases of C7 laminar fracture, large margin of safety and the ease of screw placement create a niche for this technique in the armamentarium of spine surgeons.

3D reconstructions of spinal segmental arteries using CT angiography: applications in minimally invasive spinal procedures

BACKGROUND AND PURPOSE

Injury to spinal segmental arteries may potentially occur during spinal surgery, particularly during anterior or minimally invasive approaches. Use of a noninvasive radiologic tool to evaluate these arteries before surgery may reduce this risk.

MATERIAL AND METHODS

We performed spinal CT angiography and reconstructed 3D images of segmental arteries in 41 patients. We classified the pathways and locations of the segmental arteries into 4 zones (A, B, C, and D) according to pedicle and vertebral endplates. We designated segmental arteries from T8 to L1 as "high-level segmental arteries" and those from L2 to L4, as "low-level segmental arteries." We compared the distribution of segmental arteries between these 2 groups. We also investigated anatomic variations of segmental arteries and the rate of occurrence of the artery of Adamkiewicz.

RESULTS

In all patients, 3D reconstruction images from spinal CT angiography clearly showed the pathways of segmental arteries on the vertebral bodies. Most of the segmental arteries passed the middle portion of the vertebral body (zones B and C). However, 51 of 738 segmental arteries (6.9%) had uncommon pathways (zones A and D), and segmental arteries from L2 to L4 had a higher incidence of uncommon pathways than higher level vertebrae (P < .05). We also observed 2 types of segmental artery anatomic variation, agenesis and dual supply.

CONCLUSIONS

We suggest that spinal CT angiography can help to precisely visualize the spinal segmental arteries and surrounding bony structures and can aid clinicians in deciding on optimal approaches for spinal surgery.

In vitro study of accuracy of cervical pedicle screw insertion using an electronic conductivity device (ATPS part III)

Reconstruction of the highly unstable, anteriorly decompressed cervical spine poses biomechanical challenges to current stabilization strategies, including circumferential instrumented fusion, to prevent failure. To avoid secondary posterior surgery, particularly in the elderly population, while increasing primary construct rigidity of anterior-only reconstructions, the authors introduced the concept of anterior transpedicular screw (ATPS) fixation and plating. We demonstrated its morphological feasibility, its superior biomechanical pull-out characteristics compared with vertebral body screws and the accuracy of inserting ATPS using a manual fluoroscopically assisted technique. Although accuracy was high, showing non-critical breaches in the axial and sagittal plane in 78 and 96%, further research was indicated refining technique and increasing accuracy. In light of first clinical case series, the authors analyzed the impact of using an electronic conductivity device (ECD, PediGuard) on the accuracy of ATPS insertion. As there exist only experiences in thoracolumbar surgery the versatility of the ECD was also assessed for posterior cervical pedicle screw fixation (pCPS). 30 ATPS and 30 pCPS were inserted alternately into the C3-T1 vertebra of five fresh-frozen specimen. Fluoroscopic assistance was only used for the entry point selection, pedicle tract preparation was done using the ECD. Preoperative CT scans were assessed for sclerosis at the pedicle entrance or core, and vertebrae with dense pedicles were excluded. Pre- and postoperative reconstructed CT scans were analyzed for pedicle screw positions according to a previously established grading system. Statistical analysis revealed an astonishingly high accuracy for the ATPS group with no critical screw position (0%) in axial or sagittal plane. In the pCPS group, 88.9% of screws inserted showed non-critical screw position, while 11.1% showed critical pedicle perforations. The usage of an ECD for posterior and anterior pedicle screw tract preparation with the exclusion of dense cortical pedicles was shown to be a successful and clinically sound concept with high-accuracy rates for ATPS and pCPS. In concert with fluoroscopic guidance and pedicle axis views, application of an ECD and exclusion of dense cortical pedicles might increase comfort and safety with the clinical use of pCPS. In addition, we presented a reasonable laboratory setting for the clinical introduction of an ATPS-plate system.