Anterolateral approach to the cervical spine: major anatomical structures and landmarks. Technical note

Radiologic Evaluation of Uncinate Processes of the Cervical Spine and the Relationship Between the Uncinate Process and Vertebral Artery: Implication in Anterior Cervical Spine Surgery

OBJECTIVE

To determine the relationship between the uncinate process (UP) and vertebral artery (VA) from a radiologic view and to confirm the surgical safety margin to minimize the risk of VA injury during anterior cervical approaches.

METHODS

We retrospectively reviewed computed tomography angiography of 205 patients by using a contrast-enhanced computed tomography angiography protocol of the VA. Four kinds of images were simultaneously reconstructed to measure all the parameters associated with VA and UP of cervical spine.

RESULTS

The shortest distance from the UP's tip to the VA's medial border (P < 0.001) was at the C-6 level (2.9 ± 0.9 mm on the left and 3.2 ± 1.3 mm on the right), and the longest distance (P < 0.001) was at the C-3 level on both sides. The distance between UP's tip and the medial border of the ipsilateral VA was statistically significantly different at each cervical level, and the right distance was larger than the left (P < 0.05). We found the height of UP gradually increased from C-3 to C5-level and then decreased from C-5 to C-7 level for both sides. The mean distance between the medial borders of left UP and left VA was on average 7.5 ± 1.4 mm. The diameter of VA was on average 3.4 ± 0.6 mm on the left side and 3.2 ± 0.7 mm on the right. The diameter of the VA was statistically significantly different on both sides, and the left side was larger than the right (P < 0.05).

CONCLUSIONS

Detailed radiologic anatomy of VA and UP was reviewed in this study. A deep understanding of the correlation between the UP and VA is essential to perform anterior cervical spine surgery safely and ensure adequate spinal canal decompression.

The Vertebral Artery: A Systematic Review and a Meta-Analysis of the Current Literature

(1) Background. The anatomical variations of the vertebral arteries (VAs) have a significant impact both in neurosurgery and forensic pathology. The purpose of this study was to evaluate the variational anatomy of the vertebral artery. We evaluated anatomical aspects regarding the V1 and V2 segments of the VA: origin, course, tortuosity, hypoplasia, and dominance, and established the prevalence of each variation. (2) Methods. We conducted a systematic search in PubMed and Google Scholar databases, up to December 2022. Sixty-two studies, comprising 32,153 vessels, were included in the current meta-analysis. We used a random-effects model with a DerSimonian-Laird estimator. The confidence intervals were set at 95%. The heterogeneity between studies was assessed using I². The funnel plot and Egger's regression test for plot asymmetry were used for the evaluation of publication bias. Statistical significance was considered at p < 0.05. (3) Results. The most common site for the origin of both VAs was the subclavian artery. The aortic arch origin of the left VA had a prevalence of 4.81%. Other origins of the right VAs were noted: aortic arch (0.1%), right common carotid artery (0.1%), and brachiocephalic trunk (0.5%). Ninety-two percent of the VAs entered the transverse foramen (TF) of the C6 vertebra, followed by C5, C7, C4, and least frequently, C3 (0.1%). Roughly one out of four (25.9%) VAs presented a sort of tortuosity, the transversal one representing the most common variant. Hypoplasia occurred in 7.94% of the vessels. Left VA dominance (36.1%) is more common, compared to right VA dominance (25.3%). (4) Conclusions. The anatomy of the VA is highly irregular, and eventual intraoperative complications may be life-threatening. The prevalence of VA origin from the subclavian artery is 94.1%, 92.0% of the VAs entered the TF at C6, 26.6% were tortuous, and 7.94% were hypoplastic.

Identification of Deep Cervical Fascial Layers During Anterior Cervical Spine Exposure

BACKGROUND

Anterior approaches to the cervical spine are among the most common exposures by which neurosurgeons and orthopedic surgeons access the prevertebral space and ultimately the cervical disk and vertebral bodies. There is a paucity of literature describing the microanatomic fascial planes of the neck with respect to anterior cervical approaches.

OBJECTIVE

To delineate the microanatomic connections of the cervical fascial planes pertinent to anterior cervical exposure.

METHODS

Using a cadaveric model, original illustrations, the Visible Human Project, and an original surgical video, we demonstrate a stepwise method for identifying the correct planes for anterior cervical exposure.

RESULTS

A step-by-step method for identifying the anterior cervical fascial planes intraoperatively is demonstrated.

CONCLUSION

A comprehensive understanding of anterior cervical microsurgical anatomy is vital for performing a methodical yet efficient approach to the prevertebral space while minimizing retraction and iatrogenic injury to the surrounding neurovascular structures.

Clip Ligation and Disconnection of a Ruptured Ventral Subaxial Cervical Isolated Spinal Aneurysm Using Tailored Access Osteotomies: An Operative Technique

BACKGROUND

Isolated spinal aneurysms (iSAs) are lesions of the spinal vasculature with no associated vascular malformation with difficult management paradigms limited by safe access.

OBJECTIVE

To describe a case of an irregular fusiform ruptured distal subaxial cervical spine iSA with a complex angioarchitecture intimately associated with the ventral pial plexus (VPP), treated using open clip ligation and disconnection.

METHODS

A 51-year-old woman presented with complete spinal cord injury with a C8 sensory level and ventral subarachnoid hemorrhage at the C6-T1 vertebral levels. After emergent anterior evacuation and fusion, angiography revealed a small iSA around the VPP. A total laminectomy spanning C5 to T3 was completed, and bilateral C7 pedicle resections were performed. A temporary clip was placed from the left for proximal control, and a permanent clip was placed across the dome of the distal vessel for disconnection. The dura was then closed, and a cervicothoracic fusion completed.

RESULTS

Postoperative angiography confirmed iSA disconnection and obliteration with anterior spinal artery preservation. The patient had intermittent numbness in the right C8 dermatome. On postoperative day 1, she regained proprioception in the right foot and movement in the lower extremities on command. On postoperative day 3, she regained full sensation and voluntary movement in both lower extremities.

CONCLUSION

iSA is a rare and morbid condition with nonstandardized guidelines regarding management. We promote the concept of using tailored osteotomies to establish safe corridors for the open treatment of difficult subaxial cervical ventral lesions not amenable to transarterial treatment. Multidisciplinary collaboration is promising, and further investigation is highly warranted.

Topography of the Anatomical Landmarks of Carotid Bifurcation and Clinical Significance

OBJECTIVE

Carotid bifurcation (CB) and its terminal branches are the most common sites of atherosclerotic plaques. In surgical treatment, these plaques can be reached by an endarterectomy technique. The success of the technique can be achieved with good anatomical knowledge of these arteries and their relationships with surrounding structures.

MATERIALS AND METHODS

The study was performed retrospectively on archived images of patients with computed tomography angiography (CTA). Two hundred forty-seven patients who met the criteria were included in this study. Three-dimensional (3D) reconstructions of two-dimensional CTA images were made automatically using the open-source software Horos v.4.0.0. The distance between the transverse plane passing through the bifurcation point (BP) and the defined planes of the surrounding structures was evaluated.

RESULTS

CB was observed below the mastoid process, gonion point, and hyoid bone. CB was observed above the thyroid cartilage. Carotid bifurcation was seen at 15 levels in total, the lowest in the upper 1/3 of the C6 vertebral body and the highest in the lower 1/3 of the C2 vertebral body. In all cases, the most common level was the C3 lower level.

CONCLUSION

All these values, which emerged as a result of the study, provide general information about the topography of the CB according to the neighboring structures. Estimating the location of the CB according to the gonion and hyoid bone will give a more accurate result. The vertebral level on the right side increased in direct proportion to age; there was no similar relationship on the left side. It is necessary to be aware of these anatomical variations in order to prevent various iatrogenic complications.

Safety and Efficacy of Anterior Cervical Discectomy and Fusion with Uncinate Process Resection: A Systematic Review and Meta-Analysis

STUDY DESIGN

This is a meta-analysis and systematic review of the available literature.

OBJECTIVE

In the case of severe foraminal stenosis, conducting uncinate process resection (UPR) during ACDF could achieve complete nerve root decompression and significant relief of neurological symptoms for CR. However, there is some controversy regarding its necessity and safety. This study aims to compare the safety and efficacy of ACDF with UPR and ACDF.

METHODS

The following electronic databases were searched: Medline, PubMed, Embase, the Cochrane Central Register of Controlled Trials, Evidence Based Medicine Reviews, VIP, and CNKI. And the following data items were considered: baseline demographics, efficacy evaluation indicators, radiographic outcome, and surgical details.

RESULTS

10 studies were finally identified, including 746 patients who underwent ACDF with UPR compared to 729 patients who underwent ACDF. The group of ACDF with UPR had statistically longer intraoperative time (95% CI: 4.83, 19.77, P = .001) and more intraoperative blood loss (95% CI: 12.23, 17.76, P < .001). ACDF with UPR obtained a significantly better improvement of Arm VAS at postoperative first follow-up (95% CI: -1.85, -.14 P = .02). There was no significant difference found in improvement of Neck VAS at postoperative latest follow-up (95% CI: -.88, .27, P = .30), improvement of Arm VAS at postoperative latest follow-up (95% CI: -.59, -.01, P = .05), improvement of NDI (95% CI: -2.34, .33, P = .14), JOA (95% CI: -.24, .43, P = .56), change of C2-C7 lordosis (95% CI: -.87, 1.33, P = .68), C2-C7 SVA (95% CI: -.73, 5.08, P = .14), T1 slope (95% CI: -2.25, 1.51, P = .70), and fusion rate (95% CI: .83, 1.90 P = .29).

CONCLUSION

ACDF with UPR is an effective and necessary surgical method for CR patients with severe foraminal stenosis.

Intervertebral Foramen Width Is an Important Factor in Deciding Additional Uncinate Process Resection in ACDF-a Retrospective Study

Background: Anterior cervical discectomy and fusion (ACDF) has been established as a classic procedure for the management of cervical radiculopathy. However, it is unclear whether combined uncinate process resection (UPR) is necessary for treating cervical radiculopathy. Here, we investigated the clinical outcome of ACDF combined with UPR compared to ACDF alone to determine the necessity of UPR in treating cervical radiculopathy. Hypothesis: Uncinate process resection may be necessary in certain patients along with ACDF to achieve better clinical outcomes of cervical radiculopathy. Patients and Methods: Fifty-five patients underwent ACDF with UPR, and 126 patients without UPR were reviewed. The width and height of the intervertebral foramen were measured by 45° oblique X-rays. We also measured the Japanese Orthopedic Association (JOA) score and visual analog scale (VAS) score. C2-C7 Cobb angles were obtained from all patients pre- and post-operatively. Meanwhile, linear regression analysis was used to evaluate the relationship between the clinical outcomes and the intervertebral foramen width before surgery. Results: Linear regression analysis indicated that the improvement in the JOA and VAS scores was irrelevant to both the pre-operative width of the intervertebral foramen (wIVF) and the height of the intervertebral foramen (hIVF) in the ACDF+UPR group. However, pre-operative wIVF was associated with post-operative JOA and VAS scores in the ACDF alone group. Those with pre-operative wIVF <3 mm in the ACDF group had the least improvement in post-operative clinical symptoms due to the change in wIVF (P > 0.05). The ACDF group whose wIVF was over 3 mm showed similar clinical outcomes to the ACDF + UPR group, and wIVF significantly increased post-operatively (P < 0.05). The fusion rate and C2-C7 Cobb angles did not show significant differences between the two groups (P > 0.05). Discussion: Our current findings suggest that UPR should be considered when wIVF is <3 mm pre-operatively. However, there is no need to sacrifice the uncovertebral joint in ACDF when the pre-operative wIVF is over 3 mm. Level of Evidence: Level III.

Partial uncinatectomy combined with anterior cervical discectomy and fusion for the treatment of one-level cervical radiculopathy: analysis of clinical efficacy and sagittal alignment

BACKGROUND

Biomechanical studies have demonstrated that uncovertebral joint contributes to segment mobility and stability to a certain extent. Simultaneously, osteophytes arising from the uncinate process are a common cause of cervical spondylotic radiculopathy (CSR). For such patients, partial uncinatectomy (UT) may be required. However, the clinical efficacy and sagittal alignment of partial UT during anterior cervical discectomy and fusion (ACDF) have not been fully elucidated.

METHODS

A total of 87 patients who had undergone single level ACDF using a zero-profile device from July 2014 to December 2018 were included. Based on whether the foraminal part of the uncovertebral joint was resected or preserved, the patients were divided into the ACDF with UT group (n = 37) and the ACDF without UT group (n = 50). Perioperative data, radiographic parameters, clinical outcomes, and complications were compared between the two groups.

RESULTS

The mean follow-up was 16.86 ± 5.63 and 18.36 ± 7.51 months in the ACDF with UT group and ACDF without UT group, respectively (p > 0.05). The average preoperative VAS arm score was 5.89 ± 1.00 in the ACDF with UT group and 5.18 ± 1.21 in the ACDF without UT group (p = 0.038). However, the average VAS arm score was 4.22 ± 0.64, 4.06 ± 1.13 and 1.68 ± 0.71, 1.60 ± 0.70 at 1 week post operation and at final follow up, respectively, (p > 0.05). We also found that the C2-7 SVA and St-SVA at the last follow-up and their change (last follow-up value - preoperative value) in the ACDF with UT group were significantly higher than ACDF without UT group (p < 0.05). No marked differences in the other cervical sagittal parameters, fusion rate or complications, including dysphagia, ASD, and subsidence, were observed.

CONCLUSIONS

Our result indicates that ACDF using a zero-p implant with or without partial UT both provide satisfactory clinical efficacy and acceptable safety. However, additional partial UT may has a negative effect on cervical sagittal alignment.

Radiological evaluation of the localization of sympathetic ganglia in the cervical region

PURPOSE

To determine local variations of cervical sympathetic ganglia (CSG) according to vertebral levels on preoperative neck magnetic resonance imaging (MRI) by designating carotid artery (CA) as the standard landmark at the center, in attempts to prevent injury to CSG in the anterior-anterolateral approaches performed in the cervical spinal region.

MATERIALS AND METHODS

The retrospective study reviewed neck MRI images of 281 patients, of which the images of 231 patients were excluded from the study based on the exclusion criteria. As a result, the MRI images of the remaining 50 patients were included in the study. The circumference of carotid artery (CA) was divided into eight equal zones with CA defined as the standard landmark at the center. High-risk zones were determined based on the anterior-anterolateral approaches.

RESULTS

At C1 level, a superior ganglion was located on the right side in 32 (64%) and on the left side in 30 (60%) patients. At this level, it was most commonly located in Zone 6. Middle ganglion was observed most frequently at C3 level, which was detected on the right side in 17 (34%) and on the left side in 17 (34%) patients. At this level, it was most commonly located in Zone 2.

CONCLUSION

Variations in the localizations of superior and middle cervical ganglia should be taken into consideration prior to surgical procedures planned for this region. This study sheds light on high-risk zones in the surgical site and could guide surgeons to better understand the location of cervical sympathetic ganglia before surgical planning.

Effectiveness of 2 Types of Drill Templates for Cervical Anterior Transpedicular Screw Placements: A Comparative Study

OBJECTIVE

To evaluate effectiveness of regular and modified drill templates used to guide cervical anterior transpedicular screw (ATPS) placement.

METHODS

This study included 15 adult cadaveric specimens. Computed tomography images were imported into Mimics software. Three-dimensional modeling of all cervical vertebrae was done, and the ideal trajectories were designed for ATPSs. Models of regular and modified templates were designed for every level on the left or right side randomly. After three-dimensional printing, 2 types of templates were used to guide the insertion. Postoperative computed tomography scans were used to measure deviations between real and ideal trajectories in the direction and positioning of entry points. The deviations in the 2 groups were compared using paired t test.

RESULTS

There were 120 templates and ATPSs fabricated and placed. Postoperative images showed that 7 screws perforated pedicles in the regular group, with an accuracy rate of 88.3%. Deviations between real and ideal trajectories in cranially inclined angles and extroversive angles were 1.13° ± 0.61° and 0.97° ± 0.60°, respectively, and deviations of entry point position in the x-axis and y-axis were 0.72 ± 0.38 mm and 0.95 ± 0.47 mm, respectively. In the modified group, there were 2 malposition screws with accuracy rate of 96.7%. Deviations in cranially inclined angles were 0.66° ± 0.53° and 0.66° ± 0.55° in extroversive angles, respectively, and deviations in entry point positions in the x-axis and y-axis were 0.45 ± 0.37 mm and 0.51 ± 0.34 mm, respectively. The differences in deviations between groups were statistically significant.

CONCLUSIONS

Compared with regular drill templates, modified drill templates can provide higher accuracy and stronger trajectory control in ATPS insertions.

The Smith-Robinson Approach to the Subaxial Cervical Spine: A Stepwise Microsurgical Technique Using Volumetric Models From Anatomic Dissections

BACKGROUND

The Smith-Robinson1 approach (SRA) is the most widely used route to access the anterior cervical spine. Although several authors have described this approach, there is a lack of the stepwise anatomic description of this operative technique. With the advent of new technologies in neuroanatomy education, such as volumetric models (VMs), the understanding of the spatial relation of the different neurovascular structures can be simplified.

OBJECTIVE

To describe the anatomy of the SRA through the creation of VMs of anatomic dissections.

METHODS

A total of 4 postmortem heads and a cervical replica were used to perform and record the SRA approach to the C4-C5 level. The most relevant steps and anatomy of the SRA were recorded using photogrammetry to construct VM.

RESULTS

The SRA was divided into 6 major steps: positioning, incision of the skin, platysma, and muscle dissection with and without submandibular gland eversion and after microdiscectomy with cage positioning. Anatomic model of the cervical spine and anterior neck multilayer dissection was also integrated to improve the spatial relation of the different structures.

CONCLUSION

In this study, we review the different steps of the classic SRA and its variations to different cervical levels. The VMs presented allow clear visualization of the 360-degree anatomy of this approach. This new way of representing surgical anatomy can be valuable resources for education and surgical planning.

Duplicated Vagus Nerve in Adolescence: Case Report and Review of Literature

BACKGROUND

Vagus nerve stimulation (VNS) has become an increasingly popular procedure for the treatment of epilepsy and depression. Significant complications or side effects associated with VNS surgery may result from either the inadvertent direct injury to the vagus nerve as part of the surgical approach, placement of the electrode, or the concomitant stimulation of vagal efferent fibers. To mitigate these effects, the recognition of anatomic variants that may place the nerve at increased risk is necessary.

CASE DESCRIPTION

During microsurgical dissection of the carotid sheath for the implantation of a vagus nerve stimulator in a 17-year-old male patient with refractory epilepsy, additional nonidentified nerve tissue was found running parallel to the vagus nerve. These fibers were two thirds of the thickness of the vagus nerve and ran medial to it, from the most superior to the most inferior aspect of the carotid sheath dissection, found at a distance of at least 4 cm in a craniocaudal direction. This duplicated nerve did not appear to branch from the vagal trunk nor exit the sheath but rather paralleled the course of the vagus nerve. The parallel course and the proximity of the unidentified nerve make this structure likely to be a duplicated vagus nerve.

CONCLUSIONS

This is the first reported case of cervical vagus nerve duplication presented in the literature. Surgeons performing VNS implantations should be cognizant of this potential anomaly in order to avoid inadvertent injury to the nerve.

A Review of Complication Rates for Anterior Cervical Diskectomy and Fusion (ACDF)

Background:

There are multiple complications reported for anterior cervical diskectomy and fusion (ACDF), one of the most common cervical spine operations performed in the US (e.g. estimated at 137,000 ACDF/year).

Methods:

Multiple studies analyzed the risks and complications rates attributed to ACDF.

Results:

In multiple studies, overall morbidity rates for ACDF varied from 13.2% to 19.3%. These included in descending order; dysphagia (1.7%-9.5%), postoperative hematoma (0.4%-5.6% (surgery required in 2.4% of 5.6%), with epidural hematoma 0.9%), exacerbation of myelopathy (0.2%-3.3%), symptomatic recurrent laryngeal nerve palsy (0.9%-3.1%), cerebrospinal fluid (CSF) leak (0.5%-1.7%), wound infection (0.1-0.9%-1.6%), increased radiculopathy (1.3%), Horner’s syndrome (0.06%-1.1%), respiratory insufficiency (1.1%), esophageal perforation (0.3%-0.9%, with a mortality rate of 0.1%), and instrument failure (0.1%-0.9%). There were just single case reports of an internal jugular veing occlusion and a phrenic nerve injury. Pseudarthrosis occurred in ACDF and was dependant on the number of levels fused; 0-4.3% (1-level), 24% (2-level), 42% (3 level) to 56% (4 levels). The reoperation rate for symptomatic pseudarthrosis was 11.1%. Readmission rates for ACDF ranged from 5.1% (30 days) to 7.7% (90 days postoperatively).

Conclusions:

Complications attributed to ACDF included; dysphagia, hematoma, worsening myelopathy, recurrent laryngeal nerve palsy, CSF leaks, wound infection, radiculopathy, Horner’s Syndrome, respiratory insufficiency, esophageal perforation, and instrument failure. There were just single case reports of an internal jugular vein thrombosis, and a phrenic nerve injury. As anticipated, pseudarthrosis rates increased with the number of ACDF levels, ranging from 0-4.3% for 1 level up to 56% for 4 level fusions.

Anterior cervical spine blood supply: a cadaveric study

PURPOSE

To describe the origin of the vessels supplying the anterior sub-axial cervical vertebrae (C3-C7) to further understand their potential influence on anterior bone loss after anterior cervical spinal surgery.

METHOD

Cadaveric dissection was performed on ten adult human necks after latex perfusion of their subclavian, common carotid and vertebral arteries. The nutrient vessels of the sub-axial cervical spine were identified and traced to their origin. The course and distribution of these vessels and their nutrient foraminae are described.

RESULTS

In all cases the anterior nutrient vessels were derived from the thyro-cervical trunk with branches that passed over the longus coli muscles forming a leash of vessels in the pre-vertebral fascia which subsequently extended in a frond-like pattern to pass onto the anterior aspect of vertebrae. The more cranial the cervical level the fewer the number of nutrient vessels and foraminae. The distribution of the foraminae on the anterior vertebral body followed the oblique supero-medial course of the nutrient vessels.

CONCLUSION

Nutrient vessels perforate the cervical vertebrae on their anterior surface. These are derived from a leash of vessels that lie within the pre-vertebral fascia overlying the longus coli muscles. The origin of these vessels is the ascending cervical artery with a variable contribution from the transverse cervical artery.

Transection of Omohyoid Muscle as an Aid During Vagus Nerve Stimulator Implantation

BACKGROUND

Exposure of the carotid sheath during vagus nerve stimulator (VNS) implantation is usually straightforward but can be difficult for patients with a large body habitus. In addition, the exposure must be done with care if the surgeon wants to keep the vagus nerve in situ without using retractors that might impair access.

OBJECTIVE

We describe the use of the omohyoid muscle as a landmark for the jugular vein and report how transection of the omohyoid can facilitate rapid and wide exposure of the carotid sheath.

METHODS

We review the records of 59 consecutive patients undergoing VNS implantation from 2009-2015 and describe our technique incorporating omohyoid transection. We also summarize complications such as postoperative hoarseness, cough, dysphagia, or wound issues.

RESULTS

Forty-two of the 59 patients (29 adults and 13 children) underwent omohyoid transection during implantation. In all cases, the carotid sheath and jugular vein were immediately visible after transection. One patient developed permanent hoarseness and coughing due to left vocal cord paresis, requiring further surgery. This result was most likely due to manipulation of the vagus nerve rather than division of the omohyoid muscle.

CONCLUSION

Omohyoid transection provides excellent exposure of the carotid sheath during VNS implantation.

Morphometric evaluation of the uncinate process and its importance in surgical approaches to the cervical spine: a cadaveric study

INTRODUCTION

The uncinate process (UP) has an important role because of its relationship with the vertebral artery and spinal roots. Degenerative diseases cause osteophyte formation on the UP, leading to radiculopathy, myelopathy and vertebral vascular insufficiency, which may require surgical management. This study aimed to evaluate the morphometry of this region to shed light on the anatomy of the UP.

METHODS

Morphometric data was obtained from 13 male formaldehyde-fixed cadavers. Direct measurements were obtained using a metal caliper. Computed tomography (CT) morphometry was performed with the cadavers in the supine position.

RESULTS

Direct cadaveric measurements showed that the height of the UP increased from C3 (5.8 ± 1.0 mm) to C7 (6.6 ± 0.5 mm). On CT, the corresponding measurements were 5.9 ± 1.2 mm at C3 and 6.9 ± 0.6 mm at C7. The distance between the left and right apex of the UP from C3 to C7 also increased on both direct cadaveric and CT measurements (C3: 20.8 ± 1.0 mm and C7: 28.1 ± 2.4 mm vs. C3: 23.7 ± 3.4 mm and C7: 29.0 ± 3.0 mm, respectively). On CT, the distance between the UP and superior articular process at the C3 to C7 levels were 9.8 ± 1.7 mm, 7.9 ± 1.8 mm, 7.9 ± 1.6 mm, 7.8 ± 1.3 mm and 8.2 ± 1.7 mm, respectively.

CONCLUSION

Direct cadaveric and CT measurements of the UP are useful for preoperative evaluation of the cervical spine and may lead to better surgical outcomes.

Surgical Anatomy of the Uncinate Process and Transverse Foramen Determined by Computed Tomography

Study Design Computed tomography-based cohort study. Objective Although there are publications concerning the relationship between the vertebral artery and uncinate process, there is no practical guide detailing the dimensions of this region to use during decompression of the intervertebral foramen. The purpose of this study is to determine the anatomic parameters that can be used as a guide for thorough decompression of the intervertebral foramen. Methods Fifty-one patients with three-dimensional computed tomography scans of the cervical spine from 2003 to 2012 were included. On axial views, we measured the distance from the midline to the medial and lateral cortices of the pedicle bilaterally from C3 to C7. On coronal reconstructed views, we measured the minimum height of the uncinate process from the cranial cortex of the pedicle adjacent to the posterior cortex of vertebral body and the maximal height of the uncinate process from the cranial cortex of the pedicle at the midportion of the vertebral body bilaterally from C3 to C7. Results The mean distances from midline to the medial and lateral cortices of the pedicle were 10.1 ± 1.3 mm and 13.9 ± 1.5 mm, respectively. The mean minimum height of the uncinate process from the cranial cortex of the pedicle was 4.6 ± 1.6 mm and the mean maximal height was 6.1 ± 1.7 mm. Conclusions Our results suggest that in most cases, one can thoroughly decompress the intervertebral foramen by removing the uncinate out to 13 mm laterally from the midline and 4 mm above the pedicle without violating the transverse foramen.

Virtual pathology of cervical radiculopathy based on 3D MR/CT fusion images: impingement, flattening or twisted condition of the compressed nerve root in three cases

Background

There have been several imaging studies of cervical radiculopathy, but no three-dimensional (3D) images have shown the path, position, and pathological changes of the cervical nerve roots and spinal root ganglion relative to the cervical bony structure. The objective of this study was to introduce a technique that enables the virtual pathology of the nerve root to be assessed using 3D magnetic resonance (MR)/computed tomography (CT) fusion images that show the compression of the proximal portion of the cervical nerve root by both the herniated disc and the preforaminal or foraminal bony spur in patients with cervical radiculopathy.

Findings

MR and CT images were obtained from three patients with cervical radiculopathy. 3D MR images were placed onto 3D CT images using a computer workstation.

The entire nerve root could be visualized in 3D with or without the vertebrae. The most important characteristic evident on the images was flattening of the nerve root by a bony spur. The affected root was constricted at a pre-ganglion site. In cases of severe deformity, the flattened portion of the root seemed to change the angle of its path, resulting in twisted condition.

Conclusions

The 3D MR/CT fusion imaging technique enhances visualization of pathoanatomy in cervical hidden area that is composed of the root and intervertebral foramen. This technique provides two distinct advantages for diagnosis of cervical radiculopathy. First, the isolation of individual vertebra clarifies the deformities of the whole root groove, including both the uncinate process and superior articular process in the cervical spine. Second, the tortuous or twisted condition of a compressed root can be visualized.

The surgeon can identify the narrowest face of the root if they view the MR/CT fusion image from the posterolateral-inferior direction. Surgeons use MR/CT fusion images as a pre-operative map and for intraoperative navigation. The MR/CT fusion images can also be used as educational materials for all hospital staff and for patients and patients’ families who provide informed consent for treatments.

Probabilistic mapping of the cervical sympathetic trunk ganglia

The goal of this study was to create a heat map indicating the probabilistic location of major ganglia of the cervical sympathetic trunk (CST). Detailed dissections of human cadaveric specimens, followed by spatial registration and analysis of the cervical sympathetic ganglia in the neck and upper thorax regions (C1-T1) were performed in 104 neck specimens (both sides from 52 cadavers). Unbiased parametric mapping, visualized with a heat map, revealed a general pattern of two major ganglia located on both sides of the neck: The superior cervical ganglion (SCG) was located 80-90 mm superior to the point at which the vertebral artery entered the transverse foramen (VA-TF); the stellate ganglion (SG) was located approximately 10 mm inferior to the VA-TF in 80% of our sample, or surrounding the VA-TF in the remaining 20% of our sample. In between these ganglia, a highly variable number of smaller and less prevalent ganglia were present on either side of the neck. The middle ganglia on the right side of the neck were located closer to the SCG, possibly indicative of the middle cervical ganglion. On the left side the middle ganglia were located closer to the SG, perhaps indicative of the vertebral ganglion or the inferior cervical ganglion. Individual specimens could be classified into one of seven different patterns of cervical trunks. The results may help surgeons and anesthesiologists more accurately target and preserve these structures during medical procedures.

Anatomy and clinical significance of the uncinate process and uncovertebral joint: A comprehensive review

INTRODUCTION

The uncinate process and its associated uncovertebral articulation are features unique to the cervical spine. This review examines the morphology of these unique structures with particular emphasis on the regional anatomy, development and clinical significance.

MATERIALS AND METHODS

Five electronic databases were utilized in the literature search and additional relevant citations were retrieved from the references. A total of 74 citations were included for review.

RESULTS

This literature review found that the uncinate processes and uncovertebral articulations are rudimentary at birth and develop and evolve with age. With degeneration they become clinically apparent with compression of related structures; most importantly affecting the spinal nerve root and vertebral artery. The articulations have also been found to precipitate torticollis when edematous and be acutely damaged in severe head and neck injuries. The uncinate processes are also important in providing stability and guiding the motion of the cervical spine.

CONCLUSION

This review is intended to re-examine an often overlooked region of the cervical spine as not only an interesting anatomical feature but also a clinically relevant one.

The efficacy of carotid tubercle as an anatomical landmark for identification of cervical spinal level in the anterior cervical surgery: comparison with preoperative C-arm fluoroscopy

Background

In cervical anterior approach, transverse skin incision is preferred due to cosmetic reasons. Precise skin incision is required to reach the surgery segment while minimizing soft tissue injury. Skin incision site is frequently identified using C-arm fluoroscopy or the carotid tubercle. Accordingly, this study was conducted to investigate the efficacy of skin incision using the carotid tubercle as a marker.

Methods

This study was retrospectively conducted on 114 patients who underwent anterior cervical surgery by the same surgeon from April 2004 to June 2012. The rate of the appropriate insertion of K-wire, which was inserted into the disc after anterior approach, into the surgery segment was compared between 62 patients where skin incision site was identified using C-arm fluoroscopy before skin incision and 52 patients where skin incision site was identified using carotid tubercle palpitation before surgery.

Results

The needle was shown to have been inserted into the planned site in 106 patients out of the total 114 patients. The appropriate insertion of the needle was shown in 59 patients of group I (95.2%) and in 47 patients of group II (90.4%). Although the success rate was higher in group I than group II, it was statistically insignificant. The success rate of one-segment surgery was shown to be 89.7% in group I and 82.6% in group II. Although the success rate was higher in group I than group II, it was statistically insignificant. The success rate of two-segment surgery was shown to be 100% in group I, and 96.4% in group II due to one case of the failure at C3-4 and C5-6. The success rate of three- and four-segment surgeries was shown to be 100% in both groups.

Conclusions

The identification of skin incision site via carotid tubercle palpation was useful for surgeries involving two or more segments. Furthermore, it could be useful for one-segment surgery if surgical site is identified using vertebral body or soft tissues such as longus collis rather than insertion into the disc.

Application of the cervical subaxial anterior approach at C2 in select patients

The purpose of this study was to assess the feasibility and radiographic indications of using the subaxial anterior approach for decompression and fusion at C2. Anterior exposure at C2 was difficult and associated with increased morbidity. The subaxial anterior approach is easy and familiar to spine surgeons but did not provide satisfying exposure in all patients. This article describes a series of patients undergoing anterior surgery involving C2 through the subaxial anterior approach. Patients were selected based on lateral extension radiographs showing a mandibular angle higher than the C3 upper endplate. Forty-two patients (29 men and 13 women) with average age of 45 years and an average follow-up of 9.7 months were reviewed. Etiologies included Hangman's fracture (n=35), traumatic disk herniation at C2-C3 (n=1), C3 fracture (n=2), ossification of the posterior longitudinal ligament (n=2), and tumor (n=2). Single-level diskectomy (n=36) and corpectomy (n=6) were performed. Exposure was satisfactory, and operations went smoothly in all patients except in 1 man with a muscular neck. One (2.4%) postoperative complication of choking and trouble swallowing liquids was observed and diminished in 3 months with no treatment. Pre- and postoperative Japanese Orthopaedic Association scores were 13.86 ± 2.25 and 16.50 ± 0.76, respectively, with an improvement rate of 85% ± 24% in 14 patients who had preoperative neurological dysfunction. A fusion rate of 100% was achieved. The subaxial anterior approach may be simple and safe for exposure at C2 in select patients. Complicated exposure, such as the transoral or retropharyngeal approach, should be avoided in these patients.

Quantitative evaluation of the anatomical parameters for subaxial cervical spondylectomy: an anatomical study

OBJECT

The object of this investigation was to conduct a morphometric study in cadavers to determine anatomical structures, their relationships, and their morphometry for subaxial cervical spondylectomy.

METHODS

Forty sides of 20 cadavers were used for this study. Dissections were performed in 2 stages (anteriorly and posteriorly). Twenty-one morphometric measurements were performed for both sides of the C3-6 vertebrae. Data were analyzed statistically.

RESULTS

Morphometry of the laminas, tuberculum posterius, pedicle, corpus, foramen transversarium, and processus costalis were measured.

CONCLUSIONS

Detailed quantitative anatomical knowledge for operations requiring wide dissection and resection, such as cervical spondylectomy, lowers the morbidity rate.

Vertebral levels of key landmarks in the neck

Vertebral levels of key landmarks in the neck are well documented in anatomy texts but are they accurate? This study aimed to investigate the vertebral levels of the hard palate, hyoid bone, thyroid cartilage, cricoid cartilage, and bifurcation of the common carotid artery (CCA) using computed tomography (CT). After excluding patients with distorting pathology, 52 CT scans of the neck from supine adults with a standardized head position (mean age 63 ± 17 years, range 30-94 years; 21 female) were available for analysis by dual consensus reporting. Only the vertebral level of the hard palate (C1) was consistent with contemporary descriptions. Other landmarks were located most frequently at the following vertebral levels: the center of the body of the hyoid bone at C4 (54% of cases); the superior limit of the laminae of the thyroid cartilage at C4 in women (60%) and C5 in men (52%) (P = 0.02); the inferior border of the cricoid cartilage in the midline anteriorly at C6 in women (37%) and C7 in men (47%) (P = 0.008); and the bifurcation of the left and right common carotid arteries at C3 (left 56%, right 62%). The bifurcation of the CCA was a mean of 1.6 ± 1.2 cm above the superior border of the thyroid laminae. Vertebral levels of key bony/cartilaginous structures in the neck differ from standard descriptions but in the absence of a standardized cervical axial plane have limited value and clinical utility.

Total subaxial reconstruction

OBJECT

Certain cervical spinal conditions require decompression and reconstruction of the entire subaxial cervical spine. There are limited data concerning the clinical details and outcomes of patients treated in this manner. The object of this study was to describe the specific technique employed to perform a total subaxial reconstruction and review the postoperative outcomes following surgery.

METHODS

The author performed a review of data prospectively collected in 27 consecutive patients undergoing complete anterior decompression and reconstruction of the anterior cervical spine and followed by posterior instrumented arthrodesis with or without decompression.

RESULTS

There were 16 men and 11 women whose mean age was 59 years (range 35-86 years). The minimum follow-up was 12 months and the mean follow-up period for all patients was 26 months. One patient underwent C2-7 surgery, and in all others the procedure crossed the cervicothoracic junction. Following surgery patients remained intubated for an average of 3.3 days (range 1-22 days). The mean hospital length of stay was 11 days (range 3-45 days). One patient died 6 weeks following an uneventful surgery. Pneumonia developed in 5 patients, 1 patient experienced a minor pulmonary embolism, and 2 patients had posterior wound infections. No patient was neurologically worse following surgery. A single patient presented with a C-8 radiculopathy 6 weeks after surgery. At final follow-up no patient complained of dysphagia when specifically questioned about this potential problem. In all patients solid fusions developed at each treated levels. Preoperatively the mean sagittal Cobb angle was 15.4° (kyphosis) and the postoperative mean angle was -10.9° (lordosis) representing a total average correction of over 25° (p < 0.0001). The mean preoperative Neck Disability Index was 27.6; this score decreased to 15.5 (p = 0.0008) postoperatively. The mean pre- and postoperative visual analog scale neck pain scores were 6.0 and 2.1, respectively (p = 0.0004), and mean visual analog scale arm pain scores decreased by 3.7 following surgery (p = 0.001). Based on Odom criteria, the author found that 8 patients had an excellent outcome and 14 patients a good outcome. There were 4 patients in whom the outcome was judged to be fair and the single death was recorded as a poor outcome. The mean preoperative Nurick score was 2.68. Postoperatively the group improved to an average score of 1.5; the difference between the 2 was statistically significant (p = 0.002).

CONCLUSIONS

Segmental anterior decompression and reconstruction of the entire subaxial cervical spine, combined with an instrumented posterolateral fusion, can be performed with acceptable morbidity and is of significant benefit in selected patients.

Anterior Fixation of the Axis

BACKGROUND:

Although anterior fixation of the axis is not commonly performed, plate fixation of C2 is an important technique for treating select upper cervical traumatic injuries and is also useful in the surgical management of spondylosis.

OBJECTIVE:

To report the technique and outcomes of C2 anterior plate fixation for a series of patients in which the majority presented with symptomatic degenerative spondylosis.

METHODS:

Forty-six consecutive patients underwent single or multilevel fusions over a 7-year period; 30 of these had advanced degenerative disease manifested by myelopathy or deformity. Exposure was achieved with rostral extension of the standard anterior cervical exposure via careful soft tissue dissection, mobilization of the superior thyroid artery, and the use of a table-mounted retractor. It was not necessary to remove the submandibular gland, section the digastric muscle, or make additional skin incisions.

RESULTS:

Screws were placed an average of 4.6 mm (± 2.3 mm) from the inferior C2 endplate with a mean sagittal trajectory of 15.7° (± 7.6 °).

Short- and long-term procedure-related mortality was 4.4%, and perioperative morbidity was 8.9%. Patients remained intubated an average of 2.5 days following surgery. Dysphagia was initially reported by 15.2% of patients but resolved by the 8th postoperative week in all patients. Arthrodesis was achieved in all patients available for long-term follow-up. Multilevel fusions were not associated with longer hospitalization or morbidity.

CONCLUSION:

Anterior plate fixation of the axis for degenerative disease can be accomplished with acceptable morbidity employing an extension of the standard anterolateral route.

Surgical anatomy and quantitation of the branches of the V2 and V3 segments of the vertebral artery

Object

The vertebral artery (VA) and its branches may be encountered during various neurosurgical procedures such as far lateral suboccipital approaches to the skull base and spinal operations. Therefore, a working knowledge of the distribution and significance of such VA branches may be advantageous to the surgeon. To date, quantitation of these branches is lacking in the literature.

Methods

The authors evaluated the branches of 20 VAs from 10 adult cadavers and assessed the distribution and surgical significance of the branches from the V2 and V3 segments.

Results

In terms of target tissues, the VA branches encountered at the C1–2 level were most likely to be muscular, branches at C2–3 osseous, and those at C3–6 radicular. No radicular or medullary branches were identified arising from any V3 segment of the VA or C1–2 level of the V2 segment. The greatest concentration of branches per level was found arising from the V2 segment at C2–3. Posterior branches of the VA tended to be radicular or muscular, whereas anterior branches tended to be radicular or osseous. Lateral branches were most commonly radicular and medial branches tended to be osseous or muscular in nature. The largest branches of the VA originated from its V3 segment or the C2–3 part of its V2 segment. Rarely, branches to the extracranial glossopharyngeal and spinal accessory nerves were identified originating from the V3 and V2 segments of the VA, respectively.

Conclusions

Although seemingly diverse in their distribution, the branches of the V2 and V3 segments of the VA may follow a certain consistent arrangement. The potential for injury to neural branches of the VA is minimal at its V3 segment and the C1–2 portion of its V2 segment. Such knowledge may be of use to the neurosurgeon who operates in the neck and at the craniocervical junction.