Vertebral artery variations and osseous anomaly at the C1-2 level diagnosed by 3D CT angiography in normal subjects

Alternative Percutaneous Dural Puncture Routes: Cervical, Thoracic, Lumbar, and Sacral

Patients requiring lumbar punctures (LPs) are frequently challenging or may be impossible to do through a standard lower lumbar route. Therefore, if clinically indicated, consideration of alternative anatomic access routes to the spinal subarachnoid space may be necessary. However, some of these approaches are unpopular or seldom used, may be challenging to perform, or are associated with potential significant complications especially when combined with limited operator experience. Here we review the techniques and drawbacks of multiple different approaches for percutaneous insertion of spinal needles into the spinal dural sac as alternatives to standard interlaminar low LPs.

Management of complex vertebral artery anatomy in craniocervical surgery: A case report

Background

The surgery on the craniocervical junction is associated with complex techniques that endanger the vertebral artery (VA), especially if there are some anatomical variations present, thereby increasing the risk of vascular injury, particularly during cervical decompression or instrumentation.

Case Description

A case of a 60-year-old female with progressive myelopathy and craniocervical junction malformation is presented. Key preoperative imaging findings included basilar invagination, C1 assimilation, and os odontoideum, along with VA anomalies such as a tortuous, hypoplastic left VA arising anomalously from the aortic arch and a right VA with a V2 segment forming a high-riding medial loop into the C2 vertebral body. The surgical procedure was performed through a posterior approach using C-arm fluoroscopy, Doppler ultrasound, and intraoperative neurophysiologic monitoring, which achieved adequate deformity fixation and anterior decompression.

Conclusion

Computed tomography angiography is the gold standard for assessing the preoperative VA anatomy at the craniocervical junction. Intraoperative Doppler ultrasound is invaluable because it minimizes the risk of sudden accidental injury to VAs in cases with abnormal anatomies.

Anatomic variation of the vertebral artery: a case involving a persistent first intersegmental artery at C1-C2

BACKGROUND

We observed a rare anatomical variation of a persistent first intersegmental vertebral artery in the C1-C2 region in an elderly Chinese male cadaver at Changzhi Medical College. In this case, the vertebral artery, rather than passing through the transverse foramen of the atlas, exits the transverse foramen of C2 and enters the spinal canal at the lower portion of the C1 posterior arch. The original transverse foramen of C1 was filled with connective tissue. This report details the anatomical characteristics of this abnormal vertebral artery and discusses its anatomical, surgical, and developmental implications.

PURPOSE

We describe the detailed morphological features of a rare VA variant and discuss the anatomical, clinical, and developmental aspects of this case.

METHODS

A case of head dissection. The anatomical characteristics of the VA were studied and documented, and anatomical measurements were collected.

RESULTS

In this case, the vertebral artery, rather than passing through the transverse foramen of the atlas, exits the transverse foramen of C2 and enters the spinal canal at the lower portion of the C1 posterior arch. The original transverse foramen of C1 was filled with connective tissue.

CONCLUSION

The anomalous development of segmental arteries in our case is linked to failures in the embryonic sclerotome reconstruction during development and failure.

V3 segment of the right vertebral artery taking an anomalous posterosuperior course and penetrating occipital bone (wall of the jugular foramen) diagnosed by magnetic resonance angiography

PURPOSE

To describe a case of an anomalous posterosuperior course of the V3 segment of the right vertebral artery (VA) that penetrated the occipital bone (wall of the jugular foramen).

METHODS

A 33-year-old healthy woman underwent cranial magnetic resonance (MR) imaging and MR angiography from the upper cervical to the intracranial region using a 3-Tesla scanner to screen for asymptomatic brain lesions, including cerebrovascular diseases.

RESULTS

MR angiography showed no pathological arterial lesions such as aneurysms; however, there was an anomalous posterosuperior course of the V3 segment of the right VA. On MR angiographic source images and coronal reformatted images, the right VA was observed to penetrate the occipital bone lateral to the right hypoglossal canal and is located on the inferoposteromedial wall of the right jugular foramen and enter the posterior fossa at a higher level than the foramen magnum.

CONCLUSION

We present a case in which the right VA showed an anomalous posterosuperior course at the craniovertebral junction. It is extremely rare for a VA to take a higher course. To our knowledge, this is the first report of such a VA variation in the relevant English-language literature. We speculated that the right VA of our patient was formed by the persistence of one more cephalad primitive artery than the first intersegmental artery, not by the persistence of the primitive hypoglossal artery. Careful observation of MR angiographic source is useful and important for identifying the VA penetrating the occipital bone.

A Prevalence Anatomic-Imaging Study of the Posterior Inferior Cerebellar Artery's Origin

Background and Objectives: Typically, the vertebral arteries (VAs) enter the posterior fossa through dural rings and further unite, forming the basilar artery. The posterior inferior cerebellar artery (PICA) is usually a branch of the V4 segment of the VA (intradural origin). It may also leave the V3 suboccipital segment of the VA (extradural origin). The transdural origin of the PICA within the VA's dural ring has been consistently overlooked. A study was designed to determine the topographical patterns of the PICA's origin. Materials and Methods: Determinations were performed in a retrospective sample of 225 computed tomography angiograms. Four types of PICA origin were documented: type 0, absent PICA; type 1, the extradural origin of the PICA from the V3 segment of the VA; type 2, the transdural origin of the PICA within the dural ring; and type 3, the intradural origin of the PICA from the V4 segment of the VA. The bilateral symmetry of types was also investigated. Results: Out of 450 VAs, type 0 (absent PICA) was found in 36%, type 1 (extradural) in 0.44%, type 2 (transdural) in 5.56%, and typical type 3 in just 58%. In types 1 and 2, the PICA entered the posterior fossa through the dural ring and the marginal sinus. In the overall group (N = 225), the type combinations 1_1, 1_2 and 1_3 were not found. Bilaterally absent PICAs occurred in 18.67%. The bilateral combinations 0_1/0_2/0_3/2_2/2_3/3_3 were found, respectively, in 0.89%/3.11%/30.67%/1.78%/4.44%/40.44%. Four of the seventy-eight PICAs opposite to an absent one, three intradural and one transdural, were true bihemispheric PICAs. Conclusions: The PICAs with extradural or transdural origins are facultative contents of the dural ring and are at risk during neurosurgical approaches in the foramen magnum. Rare bihemispheric PICAs could originate either intradurally or within the dural ring.

Endovascular Management of a Ruptured Aneurysm on a Posterior Inferior Cerebellar Artery with Extradural C2-Origin: Case Report and Literature Review

Extracranial vascular pathology uncommonly causes intracranial subarachnoid hemorrhage (SAH). Among possible lesions are aneurysms at the craniocervical junction arising from a posterior inferior cerebellar artery (PICA) with an extradural origin. We describe a case of a 55-year-old female presenting with a sudden and severe headache. A computed tomography scan revealed a SAH within the fourth ventricle and cervical spinal canal, and a ruptured saccular aneurysm on a PICA with extradural C2-origin. Despite difficult access anatomy, endovascular treatment was feasible and resulted in subtotal initial occlusion and preservation of distal PICA flow. Upon 3-month follow-up, the aneurysm was completely occluded with a patent PICA. The patient's clinical status remained stable at the 1.5-year follow-up. In conclusion, we present a rare case of an aneurysm originating from a PICA with extradural C2-origin that was treated endovascularly with preservation of the PICA.

Unilateral high-riding vertebral artery is associated with asymmetric morphological changes of the atlantoaxial joint: a novel risk factor for atlantoaxial osteoarthritis

PURPOSE

This study aimed to investigate the association between unilateral high-riding vertebral artery (HRVA) and morphological changes in the atlantoaxial joint (AAJ) and to determine whether unilateral HRVA is a risk factor for atlantoaxial osteoarthritis (AAOA).

METHODS

We conducted a retrospective analysis of 2496 patients admitted to our medical center between January 2020 and December 2022 who underwent CT imaging of the cervical spine. Two hundred and seventy-two patients with unilateral HRVA (HRVA group) were identified and a respective 2:1 age- and sex-matched control group without HRVA was built. Morphological parameters, including C2 lateral mass settlement (C2 LMS), C1/2 coronal inclination (C1/2 CI), lateral atlanto-dental interval (LADI), and C1/2 relative rotation angle (C1/2 RRA) were measured. The degree of AAOA was recorded. Risk factors associated with AAOA were identified using univariate and multivariable logistic regression analyses.

RESULTS

The study included 61.4% women, and the overall average age of the study population was 48.7 years. The morphological parameters (C2 LMS, C1/2 CI, and LADI) in AAJ were asymmetric between the HRVA and the non-HRVA sides in the HRVA group (p < 0.001). These differences in parameters (d-C2 LMS, d-C1/2 CI, and d-LADI) between the HRVA and the non-HRVA sides, and C1/2 RRA were significantly larger than those in the control group. Eighty-three of 816 patients (10.2%) with AAOA had larger values of d-C2 LMS, d-C1/2 CI, d-LADI, and C1/2 RRA compared with the patients without AAOA (p < 0.05). The multivariable logistic regression analysis indicated that unilateral HRVA [adjusted odds ratio (OR) = 2.6, 95% CI: 1.1-6.3, p = 0.029], age in the sixth decade or older (adjusted OR = 30.2, 95% CI: 16.1-56.9, p < 0.001), women (adjusted OR = 2.1, 95% CI: 1.0-5.6, P = 0.034) were independent risk factors for AAOA.

CONCLUSION

Unilateral HRVA was associated with asymmetric morphological changes of nonuniform settlement of C2 lateral mass, lateral slip of atlas, and atlantoaxial rotation displacement. Besides age ≥ 60 years and females, unilateral HRVA is an independent risk factor for AAOA.

A comprehensive review of the vertebral artery anatomy

BACKGROUND

The vertebral arteries (VA) play a critical role by supplying nearly one-third of the brain's blood flow, predominantly contributing to the posterior circulation. These arteries may need to be exposed in a various cranial and cervical procedures and offers access to investigate or treat vascular lesions by endovascular means related to the posterior circulation. Given its complex anatomy, which is subject to numerous variations, and its role in supplying vital brain regions, a thorough understanding of the VA's anatomy is paramount for any related procedure.

OBJECTIVE

To provide a comprehensive overview of vertebral artery anatomy and its relevance in contemporary clinical practice.

METHODS

Dissection of the entire vertebral artery length using cadaveric specimen, combined with a comprehensive literature review.

RESULTS

The vertebral artery can be subdivided into four segments. Each of these segments has its own unique topographic anatomy with its variations, anastomoses, and significance in surgery.

CONCLUSION

As surgical and endovascular techniques continue to evolve with technological improvements, we are now more equipped than ever to manage complex lesions involving the VA. However, with its increasingly complexity comes the necessity for a deeper and more comprehensive understanding of the VA. Possessing the detailed knowledge of the VA is vital for the successful execution of any procedure involving it.

Prevalence of anatomical variations at the suboccipital (V3) segment of the vertebral artery: a systematic review

BACKGROUND AND OBJECTIVE

A recent meta-analysis on the incidence of iatrogenic injury to the VA has revealed that patients with variant anatomy are more prone to iatrogenic injury. Therefore, this review is designed to investigate the incidence of variations in the suboccipital component of the vertebral artery in different population groups according to the available literature.

METHODS

This systematic review was conducted according to PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). The review is based on a comprehensive and extensive search of PubMed, Google Scholar, and ResearchGate. The following search terms were used: "vertebral artery" AND "suboccipital segment" AND "anomalies/anatomical variations of the V3 segment." Reference lists of all extracted articles were also extensively searched for references to any further relevant publications.

RESULTS

A total of 17 papers met the inclusion criteria. The 17 studies corresponded to a total of 10,820 patients. A persistent first intersegmental artery was registered in 1.8% (197 out of 10,820) of the patients. Extradural PICA origin was observed in 1.6% (175 out of 10,820) of the patients. Fenestration was detected in 0.7% (72 out of 10,820) of the patients.

CONCLUSION

The authors summarize the incidence of vascular variation at the suboccipital segment of the VA in different population groups across the Asian, European, American, and African continents. Awareness of the extent of possible anatomical variation will help interpret radiographs, which will enhance the identification of vascular pathologies and reduce the risk of iatrogenic injury.

Comparison of intraoperative CT- and cone beam CT-based spinal navigation for the treatment of atlantoaxial instability

BACKGROUND CONTEXT

Due to the complexity of neurovascular structures in the atlantoaxial region, spinal navigation for posterior C1-C2 instrumentation is nowadays a helpful tool to increase accuracy of surgery and safety of patients. Many available intraoperative navigation devices have proven their reliability in this part of the spine. Two main imaging techniques are used: intraoperative CT (iCT) and cone beam computed tomography (CBCT).

PURPOSE

Comparison of iCT- and CBCT-based technologies for navigated posterior instrumentation in C1-C2 instability.

STUDY DESIGN

Retrospective study.

PATIENT SAMPLE

A total of 81 consecutive patients from July 2014 to April 2020.

OUTCOME MEASURES

Screw accuracy and operating time.

METHODS

Patients with C1-C2 instability received posterior instrumentation using C2 pedicle screws, C1 lateral mass or pedicle screws. All screws were inserted using intraoperative imaging either using iCT or CBCT systems and spinal navigation with autoregistration technology. Following navigated screw insertion, a second intraoperative scan was performed to assess the accuracy of screw placement. Accuracy was defined as the percentage of correctly placed screws or with minor cortical breach (<2 mm) as graded by an independent observer compared to misplaced screws.

RESULTS

A total of 81 patients with C1-C2 instability were retrospectively analyzed. Of these, 34 patients were operated with the use of iCT and 47 with CBCT. No significant demographic difference was found between groups. In the iCT group, 97.7% of the C1-C2 screws were correctly inserted; 2.3% showed a minor cortical breach (<2 mm); no misplacement (>2 mm). In the CBCT group, 98.9% of screws were correctly inserted; no minor pedicle breach; 1.1% showed misplacement >2 mm. Accuracy of screw placement demonstrated no significant difference between groups. Both technologies allowed sufficient identification of screw misplacement intraoperatively leading to two screw revisions in the iCT and three in the CBCT group. Median time of surgery was significantly shorter using CBCT technology (166.5 minutes [iCT] vs 122 minutes [CBCT]; p<.01).

CONCLUSIONS

Spinal navigation using either iCT- or CBCT-based systems with autoregistration allows safe and reliable screw placement and intraoperative assessment of screw positioning. Using the herein presented procedural protocols, CBCT systems allow shorter operating time.

A comprehensive analysis and literature review of vertebral artery variation in craniovertebral junction using three-dimensional computed tomography angiography

PURPOSE

To describe vertebral artery (VA) variation in patients with or without osseous anomalies at congenital craniovertebral junction (CVJ).

METHODS

In the present study, we retrospectively analyzed 258 patients with VA variation who underwent three-dimensional computed tomography angiography (3D CTA) in our hospital from March 2017 to October 2019.

RESULTS

Among 258 patients, 180 were accompanied by skeleton structural malformation, including 105 cases of occipital ossification of the atlas, 8 cases of the bipartite atlas, 7 cases of hypoplasia of the posterior arch of the atlas, 45 cases of C2/3 congenital fusion, 2 cases of C2/3/4 congenital fusion, and 13 cases of congenital os odontoid. VA variation was divided into type A (VA variation in the CVJ area without osseous anomalies) and type B (VA variation in the CVJ area with osseous anomalies). There are totally 10 subtypes, including type A1 (atlas occipitalization with VA entrance approach close to middle line, 20.2%); type A2 (atlas occipitalization with VA entrance approach far from middle line, 30.2%); type A3 (first intersegmental VA in C1-C2, 1.9%); type A4 (fenestration of the VA, 2.3%); type A5 (VA bulging type, 6.6%); type A6 (VA exposures with the absence of the posterior atlas arch, 2.3%); type A7 (C2 inner wall type, 0.4%); type A8 (single vertebral artery, 2.3%); type B1 (posterior ponticuli, 2.7%); and type B2 (high-riding VA, 31.4%).

CONCLUSION

This study is expected to take the lead in the most comprehensive classification of VA variation.

Measurement of Deformity at the Craniovertebral Junction: Correlation of Triangular Area and Myelopathy

OBJECTIVE

Diseases of the craniovertebral junction (CVJ) are commonly associated with deformity, malalignment, and subsequent myelopathy. The misaligned CVJ might cause compression of neuronal tissues and subsequently clinical symptoms. The triangular area (TA), measured by magnetic resonance imaging/images (MRI/s), is a novel measurement for quantification of the severity of compression to the brain stem. This study aimed to assess the normal and pathological values of TA by a comparison of patients with CVJ disease to age- and sex-matched controls. Moreover, postoperative TAs were correlated with outcomes.

METHODS

Consecutive patients who underwent surgery for CVJ disease were included for comparison to an age- and sex-matched cohort of normal CVJ persons as controls. The demographics, perioperative information, and pre- and postoperative 2-year cervical MRIs were collected for analysis. Cervical TAs were measured and compared.

RESULTS

A total of 201 patients, all of whom had pre- or postoperative MRI, were analyzed. The TA of the CVJ deformity group was larger than the healthy control group (1.62 ± 0.57 cm2 vs. 1.01 ± 0.18 cm2, p < 0.001). Moreover, patients who had combined anterior odontoidectomy and posterior laminectomy with fixation had the greatest reduction in the TA (1.18 ± 0.58 cm2).

CONCLUSION

In CVJ deformity, the measurement of the cervical TA could indicate the severity of brain stem compression. After surgery, the TA had a varying degree of improvement, which could represent the efficacy of surgery.

Bilateral persistent intersegmental artery in a patient with posterior atlantoaxial subluxation after subaxial cervical laminoplasty

INTRODUCTION AND IMPORTANCE

To summarize the clinical manifestations and treatment of bilateral persistent first intersegmental artery (PFIA) in a patient with posterior subluxation of atlantoaxial joint.

CASE PRESENTATION

A-85-year-old woman with a two-months history of aggravating of gait disturbance and finger clumsiness was referred to our hospital. Magnetic resonance imaging revealed posterior subluxation of the atlantoaxial joint and spinal cord compression at C1 level. Three-dimensional computed tomography angiography (CTA) of cervical spine showed bilateral PFIA and left side high-riding VA. Because of the high risk of vertebral artery injury with posterior arch resection and lateral mass screw insertion due to the presence of PFIA, as well as the bony fragility of the cervical spine and the fact that the posterior atlantoaxial subluxation was reduced in the flexed position, the posterior occipito-thoracic fixation without posterior arch resection in the mildly flexed cervical position was underwent. The postoperative course was uneventful and her neurological symptoms improved gradually after surgery.

CLINICAL DISCUSSION

PFIA is a very rare condition representing between 0.01 % and 1.8 %. Most patients with this condition have a unilateral persistent segmental artery, but in a small minority of cases it occurs bilaterally. It may be more difficult to resect of posterior arch or insert the C1 lateral mass screw in cases of PFIA.

CONCLUSION

The best way to avoid IVAI may be careful examining the abnormal running of VA preoperatively especially on 3D-CT of cervical spine with arteriography and not to choose a technique with a high risk of VA injury.

[The effect of axis pedicle and intra-axial vertebral artery on C 2 pedicle screw placement]

OBJECTIVE

To investigate the influence of axis pedicle and intra-axial vertebral artery (IAVA) alignment on C 2 pedicle screw placement by measuring the data of head and neck CT angiography.

METHODS

The axis pedicle diameter (D), isthmus height (H), isthmus thickness (T), and IAVA alignment types were measured in 116 patients (232 sides) who underwent head and neck CT angiography examinations between January 2020 and June 2020. Defined the IAVA offset direction by referencing the vertical line through the center of C 3 transverse foramen on the coronal scan, it was divided into lateral (L), neutral (N), and medial (M). Defined the IAVA high-riding degree by referencing the horizontal line through the outlet of the C 2 transverse foramen, it was divided into below (B), within (W), and above (A). The rate of pedicle stenosis, high-riding vertebral artery, and different IAVA types were calculated, and their relationships were analysed. Simulative C 2 pedicle screws were implanted by Mimics 19.0 software, and the interrelation among the rates of pedicle stenosis, high-riding vertebral artery, IAVA types, and vertebral artery injury were analyzed.

RESULTS

The rate of C 2 pedicle stenosis was 33.6% (78/232), and the rate of high-riding vertebral artery was 35.3% (82/232). According to the offset direction and the degree of riding, IAVA was divided into 9 types, among which the N-W type (29.3%) was the most, followed by the L-W type (19.0%) and the L-B type (12.9%), accounting for 60.9%. The vertebral artery injury rate of simulative implanted C 2 pedicle screws was 35.3% (82/232). The vertebral artery injury rate in patients with pedicle stenosis and high-riding vertebral artery was significantly higher than that who were not ( P<0.001). The rate of pedicle stenosis, high-riding vertebral artery, and vertebral artery injury were significantly different among IAVA types ( P<0.001), and M-A type was the most common.

CONCLUSION

Vertebral artery injury is more common in pedicle stenosis and/or high-riding vertebral artery and/or IAVA M-A type. Preoperative head and neck CT angiography examination has clinical guiding significance.

The computed tomographic evaluation of bony bridge of C1 as bleeding risk factor at the screw placement

PURPOSE

To investigate the prevalence and morphological characteristics of ponticulus posticus (PP) and ponticulus lateralis (PL) using computed tomography (CT) images on a large study sample of the Anatolian population. The presence of the PP and PL bridges can limit gap available for placement procedure through the bony elements of C1. Routine screw techniques are contraindicated because of high risk of fatal bleeding of vertebral artery (VA).

METHODS

The CT images of 1000 subjects (500 males, 500 females) were examined for the morphological characteristics and presence of PP and PL. The anteroposterior diameter, superoposterior (transverse) diameter, surface area, and central thickness of the bony bridge of the PP, PL, and transverse foramina (TF).

RESULTS

The prevalence of PP was 14.8%, and bilateral complete PP was the most common PP type at 6.8%. The prevalence of PL was 4.1% and left-side complete PL was the most common PL type at 1.2%. The prevalence of both PP and PL was more common in males and bilateral complete PP were more predominant in males (p = 0.004, p = 0.038, and p = 0.010, respectively). The surface area of PP and PL were determined to be smaller than the surface area of the ipsilateral TF (p < 0.001 and p = 0.042, respectively).

CONCLUSION

PP is not an uncommon anatomic anomaly and PL is even less frequently encountered. The prevalence of PP and PL was more common in males and bilateral complete PP was more predominant in males. Detailed information about the prevalence and morphometry of the PP and PL obtained in the present study could guide the clinicians dealing with neurosurgery, physical medicine and rehabilitation, and radiology in their practice.

The association between atlantoaxial instability and anomalies of vertebral artery and axis

BACKGROUND CONTEXT

A screw-rod system is the most widely used technique for atlantoaxial instability (AAI). However, neglecting anomalies of the vertebral artery and axis could lead to fatal complications. Whether or not the presence of AAI is associated with a more complicated anatomy for instrumentation is unclear.

PURPOSE

To analyze the association between AAI and anomalies of the vertebral artery and axis in patients with and without AAI.

STUDY DESIGN

A retrospective comparative study.

PATIENT SAMPLE

One hundred and twenty patients who underwent preoperative 3-dimensional computed tomography with vertebral angiography of the cervical spine at our institution from 2012 to 2020.

OUTCOME MEASURES

The C2 isthmus height, internal height of the C2 lateral mass, and C2 pedicle width were radiologically assessed.

METHODS

A case control study with matched cohort analysis was conducted. One hundred and twenty patients were divided into 2 groups according to presence of AAI, and the presence of high-riding vertebral artery (HRVA) and a narrow pedicle for insertion of the C2 pedicle screw was assessed, as was the prevalence of extraosseous vertebral artery anomaly.

RESULTS

The C2 isthmus height, C2 internal height, and C2 pedicle width were significantly narrower in the AAI group (p<.01, <.01, and <.01, respectively). A significantly greater proportion of patients with AAI had HRVA and a narrow pedicle than those without (p<.01 and < 0.01, respectively). Among patients with AAI, the C2 internal height was significantly narrower in patients with rheumatoid arthritis (p<.01). Five patients (8.3%) with AAI had vertebral artery anomaly (3 fenestration, 2 persistent first intersegmental artery), while there were no vertebral artery anomalies in patients without AAI (p<.01).

CONCLUSIONS

Vertebral artery anomalies are more common in patients with AAI. Furthermore, posterior instrumentation in patients with AAI has a narrower safe zone compared to that in patients without AAI, which may be caused by a long-lasting deformity rather than a congenital deformity. Therefore, more thorough preoperative evaluation of the anatomy should be performed in these patients.

Vertebral Artery Variations at the Craniovertebral Junction in "Sandwich" Atlantoaxial Dislocation Patients

Objective

To summarize the vertebral artery (VA) pattern of 96 “sandwich” atlantoaxial dislocation (AAD) patients and to describe the strategies of reducing the injury of VA during surgery.

Methods

From 2009 to 2020, we retrospectively reviewed the 3-dimensional computed tomography angiography data of 96 AAD patients combined with atlas occipitalization and C2–3 fusion, which were diagnosed as “sandwich” AAD and 96 patients as control group patients who were without atlas occipitalization, C2–3 fusion and any other cervical bone deformity at our institution. The variations of each side of VA were described in 3 different parts (C0–1, C1–2, and C2–3) according to the characteristics of the 3-part pathological structures in “sandwich” subgroup.

Results

One hundred ninety-two sides of VAs in every group of patients were analyzed and every VA was described separately at 3 different level regions. There were different variations in these 3 different regions: 4 variations in the upper fusion region, 5 variations in the sandwiched region, and 6 variations in the lower fusion region in sandwich AAD patients. And the rate of VA deformity in sandwich AAD patients was much higher and more types of VA variations existed.

Conclusion

In “sandwich” AAD patients, deformities of vertebral arteries in craniovertebral junction are more common, and the same VA may have deformities at different levels that severely affect surgical procedures. Therefore, preoperative imaging examination of VA for “sandwich” AAD patients is vital of guiding surgeons to avoid injury of VA during surgery.

Prevalence of Vertebral artery anomaly in upper cervical and its surgical implications: a systematic review

BACKGROUND

The presence vertebral artery (VA) abnormalities in the upper cervical may be a potential cause of catastrophic complication in the posterior approach of the upper cervical spine surgery. The aim of this study was to demonstrate the real incidence of the V3 segment anomaly in patients who need upper cervical surgery, and tried to find out the risk factors of V3 segment anomaly to evaluate the necessary of computed tomographic angiography (CTA) for upper cervical surgery.

METHOD

This systematic review was conducted following the preferred reporting items for systematic reviews and meta-Analyses (PRISMA). Retrospective studies and reports of case series involving human subjects with data on anomalies of vertebral artery in upper cervical spine were included. Data on the prevalence of persistent first intersegmental artery (PIA), fenestration of the VA (FA), posterior inferior cerebellar artery (PICA) were extracted.

RESULTS

A total of 16 articles involving 5927 subjects met the inclusion criteria. The total incidence of V3 segment anomaly in the patients with bony abnormalities was 25.9% (74/286): PIA was 17.5%, FA was 6.6% and PICA was 1.8%. The total incidence of V3 segment anomaly in the patients without bony abnormalities was 2.7% (152/5671): PIA was 1.76%, FA was 0.4% and PICA was 0.5%. The total incidence of V3 segment anomaly in Asian population without bony abnormalities was 5.8%, while in European and American population was 0.8 and 0.6%, respectively.

CONCLUSION

Patients with bone abnormalities are high risk factor for VA abnormalities, CTA is of paramount importance to evaluate the variant VA anatomy. However, regarding to the low incidence of V3 variation in normal population, we do not recommend preoperative CT angiography as mandatory part of preoperative.

A rare case report: bilateral occipital artery arising from the vertebral artery

BACKGROUND

Variations of the origin of the occipital artery (OA) can be considered as congenital anomalies that are often asymptomatic and detected incidentally on angiography or during cadaver dissection. While OA normally originates from the posterior aspect of the external carotid artery (ECA), recent evidence also reflects that OA may infrequently originate from the internal carotid artery (ICA); however, OA originating from the vertebral artery (VA) is a highly rare phenomenon.

CASE PRESENTATION

In a 54-year-old female patient with the complaint of left hemiparesis, computed tomography (CT) angiography revealed nonstenotic calcified plaques at the beginning of right ICA where common carotid artery (CCA) bifurcates. We also incidentally observed that bilateral OA originated from the VA using maximum intensity projection (MIP) technique. In addition to this rare variation, CT angiography showed the osseous anomaly termed as high-riding VA (HRVA) in the C1/2 vertebral space of the V3 segment of the VA.

CONCLUSION

To the best of our knowledge, a case of bilateral OA originating from the VA has not been reported to date. We believe that recognition of this rare variation may contribute to the relevant literature and it is of importance to consider this variation in radiological imaging and surgical procedures involving this region.

Correlation between osteoarthritis of the atlantoaxial facet joint and a high-riding vertebral artery

BACKGROUND

A high-riding vertebral artery (HRVA) is an intraosseous anomaly that narrows the trajectory for C2 pedicle screws. The prevalence of a HRVA is high in patients who need surgery at the craniovertebral junction, but reports about HRVAs in subaxial cervical spine disorders are limited. We sought to determine the prevalence of HRVAs among patients with subaxial cervical spine disorders to elucidate the potential risk for VA injury in subaxial cervical spine surgery.

METHODS

We included 215 patients, 94 were with a main lesion from C3 to C7 (subaxial group) and 121 were with a main lesion from T1 to L5 (thoracolumbar group). A HRVA was defined as a maximum C2 pedicle diameter of < 3.5 mm on axial CT. The sex, age of patients, body mass index (BMI), osteoarthritis of the atlantoaxial (C1-2) facet joints, and prevalence of a HRVA in the 2 groups were compared and logistic regression was used to identify the factors correlated with a HRVA.

RESULTS

The patients in the subaxial group were younger than those in the thoracolumbar group, but their sex and BMI did not differ significantly between the 2 groups. The mean osteoarthritis grade of the C1-2 facet joints of patients in the subaxial group was significantly higher than that in those in the thoracolumbar group. A HRVA was found in 26 patients of 94 (27.7 %) in the subaxial group and in 19 of 121 (15.7 %) in the thoracolumbar group. The prevalence of a HRVA in the subaxial group was significantly higher and osteoarthritis of C1-2 facet joints correlated significantly with a HRVA.

CONCLUSIONS

The prevalence of a HRVA in patients with subaxial cervical spine disorders is higher than in those without and osteoarthritis of the C1-2 facet joints is correlated with a HRVA.

Posterolateral epidural supra-C2-root approach (PESCA) for biopsy of lesions of the odontoid process in same sitting after occipitocervical fixation and decompression-perioperative management and how to avoid vertebral artery injury

This study aims to describe the posterolateral epidural supra-C2-root approach (PESCA), which might be a good alternative to the transoral, anterolateral, and other posterolateral approaches for biopsy of lesions of the odontoid process (OP). The preoperative planning of PESCA included computerized tomography (CT), CT-angiography, and three-dimensional reconstruction (if possible, even with three-dimensional print) to analyze the angle of the trajectory and the anatomy of the vertebral artery (VA). For PESCA, the patient is positioned under general anesthesia in prone position. In case of an osteolytic lesion with fracture of the OP, an X-ray is performed after positioning to verify anatomic alignment. In the first step, in case of instability and compression of the spinal cord, a craniocervical fusion and decompression is performed (laminectomy of the middle part of the C1 arc and removal of the lower part of the lateral C1 arc). The trajectory is immediately above the C2 root (and under the upper rest of the lateral part of C1 arc). Even if the trajectory is narrowed, it is possible to perform PESCA without relevant traction of the spinal cord. The vertical segment of V3 of the VA at the level of C2 is protected by the vertebral foramen, and the horizontal part of V3 is protected by the remnant upper lateral part of the C1 arc (in case of normal variants). PESCA might be a good choice for biopsy of selected lesions of the OP in same sitting procedure after craniocervical stabilization and decompression.

An infected aneurysm of the vertebral artery following cervical pyogenic spondylitis: a case report and literature review

BACKGROUND

An important complication of pyogenic spondylitis is aneurysms in the adjacent arteries. There are reports of abdominal aortic or iliac aneurysms, but there are few reports describing infected aneurysms of the vertebral artery. Furthermore, there are no reports describing infected aneurysms of the vertebral arteries following cervical pyogenic spondylitis. We report a rare case of an infected aneurysm of the vertebral artery as a complication of cervical pyogenic spondylitis, which was successfully treated by endovascular treatment.

CASE PRESENTATION

Cervical magnetic resonance imaging (MRI) of a 59-year-old man who complained of severe neck pain showed pyogenic spondylitis. Although he was treated extensively by antibiotic therapy, his neck pain did not improve. Follow-up MRI showed the presence of a cyst, which was initially considered an abscess, and therefore, treatment initially included guided tapping and suction under ultrasonography. However, under ultrasonographic examination an aneurysm was detected. The contrast-enhanced computed tomography (CT) scan showed an aneurysm of the vertebral artery. Following endovascular treatment (parent artery occlusion: PAO), the patient's neck pain disappeared completely.

CONCLUSION

Although there are several reports of infected aneurysms of the vertebral arteries, this is the first report describing an infected aneurysm of the vertebral artery as a result of cervical pyogenic spondylitis. Whenever a paraspinal cyst exist at the site of infection, we recommend that clinicians use not only X-ray, conventional CT, and MRI to examine the cyst, but ultrasonography and contrast-enhanced CT as well because of the possibility of an aneurysms in neighboring blood vessels. It is necessary to evaluate the morphology of the aneurysm to determine the treatment required.

C2 partial transpedicular screw technique for atlantoaxial dislocation with high-riding vertebral artery: A technique note with case series

OBJECTIVE

Although the C2 pedicle screw (C2PS) is currently the most biomechanically robust option for C2 fixation, the high-riding vertebral artery (HRVA) precludes safe C2PS placement. However, unintentional partial C2 pedicle perforation and vertebral foramen violation due to C2PS placement without neurovascular complications occurred frequently in clinic. Therefore, we have attempted to apply C2 partial transpedicular screw (C2PTS) in patients with HRVA with satisfactory preliminary outcomes. The aim of the present study is to introduce the C2PTS technique and report the preliminary radiological and clinical outcomes of application of C2PTS.

PATIENTS AND METHODS

The data of 15 patients with atlantoaxial dislocation underwent atlantoaxial arthrodesis with posterior screw-rod construct were retrospectively reviewed. All patients had unilateral or bilateral HRVA that precluded safe C2PS placement and C2PTS was used as an alternative. In this technique, a Penfield dissector was used to properly mobilize the HRVA inferiorly to preclude vertebral artery injury and pave the way for C2PTS placement. The C2PTS travelled under the superior border of the isthmus and toward the ipsilateral atlantoaxial articulation. The implant position and atlantoaxial reduction were evaluated using computed tomography (CT) scans and vertebral artery (VA) was assessed using CT angiography postoperatively.

RESULTS

Satisfactory C2PTS placement and atlantoaxial reduction were achieved in all patients. Postoperatively, no vertebral artery injury and implant failure were observed, and bone fusion was achieved in all the patients. Additionally, there were no VA occlusion or stenosis due to screws demonstrated on VA CT angiography.

CONCLUSION

C2PTS can achieve three-column fixation of axis and is an efficient alternative to C2PS which is prohibited due to HRVA; also, gently mobilizing the HRVA inferiorly is mandatory to prevent vertebral artery injury during C2PTS placement.

Computed tomographic angiography to analyze dangerous vertebral artery anomalies at the craniovertebral junction in patients with basilar invagination

OBJECTIVE

Failure to detect dangerous anatomic vertebral artery anomalies (AVAAs) and dangerous functional vertebral artery anomalies (FVAAs) at the craniovertebral junction (CVJ) in patients with basilar invagination (BI) can result in major complications such as intraoperative vertebral artery injury, brain infarctions, and even death. Iatrogenic vertebral artery injury is a rare but severe complication of cervical spine surgery. We aimed to evaluate dangerous vertebral artery anomalies at the CVJ in patients with BI using computed tomographic angiography (CTA).

METHODS

CTA images of 61 BI patients were retrospectively analyzed to evaluate AVAAs and FVAAs at the CVJ. Dangerous AVAAs include a persistent first intersegmental artery (FIA), fenestration of the vertebral artery (FEN), and posterior inferior cerebellar artery with an extradural C1/2 origin (PICA-C1/2). Dangerous FVAAs include a dominant vertebral artery (DVA) and hypoplastic vertebral artery ending in the PICA (HVA-PICA) without joining the basilar artery.

RESULTS

Overall, 31 female and 30 male patients (mean age, 42.3 years) were included. The incidences of FIA, FEN, and PICA-C1/2 were 29.5 % (18/61), 3.3 % (2/61), and 3.3 % (2/61), respectively, whereas the incidences of DVA and HVA-PICA were 36.1 % (22/61) and 1.65 % (1/61), respectively.

CONCLUSION

Dangerous vertebral artery anomalies at the CVJ have a high incidence in patients with BI. Preoperative CTA is highly recommended in such patients to identify anomalous vertebral arteries and reduce the risk of intraoperative injury.

Computed Tomographic Morphometric Analysis of C1 and C2 for Lamina Cross Screw Placement in Malay Ethnicity

Study Design

This is an observational study of computed tomography (CT) data.

Purpose

The C1 and C2 laminas in the Malaysian Malay population were analyzed for the feasibility of fitting 3.5-mm laminar screws in a cross configuration.

Overview of Literature

Morphometric analysis of the C1 and C2 laminas has been performed for various populations but not for the Malaysian Malay population.

Methods

A total of 330 CT cervical images were measured to establish the bicortical diameter of the C1 and C2 laminas as well as their height and length. The C1 posterior tubercle bicortical diameter and height were also determined from these images. All parameters were measured up to 0.1 mm, and statistical analysis was performed using IBM SPSS Statistics ver. 24.0 (IBM Corp., Armonk, NY, USA). An independent t -test and the Pearson chi-square test were used to determine the mean difference and screw acceptance.

Results

The means of the C1 lamina measurements were 5.79±1.19 mm in diameter, 9.76±1.51 mm in height, and 20.70±1.86 mm in length. The means of the measurements of the posterior tubercle were 7.20±1.88 mm in diameter and 10.51±1.68 mm in height. The means of the C2 lamina measurements were 5.74±1.31 mm in diameter, 11.76±1.69 mm in height, and 24.96±2.56 mm in length. Overall 65.5% of C1 and 80.3% of C2 laminas are able to accept 3.5-mm screws in a cross configuration. Screw acceptability is similar between the right and left sides (p>0.05). However, males have a higher screw acceptability compared with females (p<0.05), except for the C2 left lamina.

Conclusions

It is feasible to insert a 3.5-mm screw in a cross configuration in the C1 and C2 laminas of the Malaysian Malay population, especially in males. However, a CT scan should be performed prior to the operation to determine screw acceptability and to estimate screw sizes.

Comparative Analysis of Surgical Outcomes of C1-2 Fusion Spine Surgery between Intraoperative Computed Tomography Image Based Navigation-Guided Operation and Fluoroscopy-Guided Operation

OBJECTIVE

Fixation of the C1-2 segment is challenging because of the complex anatomy in the region and the need for a high degree of accuracy to avoid complications. Preoperative 3D-computed tomography (CT) scans can help reduce the risk of complications in the vertebral artery, spinal cord, and nerve roots. However, the patient may be susceptible to injury if the patient's anatomy does not match the preoperative CT scans. The intraoperative 3D image-based navigation systems have reduced complications in instrument-assisted techniques due to greater accuracy. This study aimed to compare the radiologic outcomes of C1-2 fusion surgery between intraoperative CT image-guided operation and fluoroscopy-guided operation.

METHODS

We retrospectively reviewed the radiologic images of 34 patients who underwent C1-2 fusion spine surgery from January 2009 to November 2018 at our hospital. We assessed 17 cases each of degenerative cervical disease and trauma in a study population of 18 males and 16 females. The mean age was 54.8 years. A total of 139 screws were used and the surgical procedures included 68 screws in the C1 lateral mass, 58 screws in C2 pedicle, nine screws in C2 lamina and C2 pars screws, four lateral mass screws in sub-axial level. Of the 34 patients, 19 patients underwent screw insertion using intraoperative mobile CT. Other patients underwent atlantoaxial fusion with a standard fluoroscopy-guided device.

RESULTS

A total of 139 screws were correctly positioned. We analyzed the positions of 135 screws except for the four screws that performed the lateral mass screws in C3 vertebra. Minor screw penetration was observed in seven cases (5.2%), and major pedicle screw penetration was observed in three cases (2.2%). In one case, the malposition of a C2 pedicle screw was confirmed, which was subsequently corrected. There were no complications regarding vertebral artery injury or onset of new neurologic deficits. The screw malposition rate was lower (5.3%) in patients who underwent intraoperative CT-based navigation than that for fluoroscopy-guided cases (10.2%). And we confirmed that the operation time can be significantly reduced by surgery using intraoperative O-arm device.

CONCLUSION

Spinal navigation using intraoperative cone-beam CT scans is reliable for posterior fixation in unstable C1-2 pathologies and can be reduced the operative time.

Posterior atlantoaxial fusion: a comprehensive review of surgical techniques and relevant vascular anomalies

Posterior atlantoaxial fusion is an important surgical technique frequently used to treat various pathologies involving the cervical 1-2 joint. Since the beginning of the 20th century, various fusion techniques have been developed with improved safety profile, higher fusion rates, and superior clinical outcome. Despite the advancement of technology and surgical techniques, posterior C1-2 fusion is still a technically challenging procedure given the complex bony and neurovascular anatomy in the craniovertebral junction (CVJ). In addition, vascular anomalies in this region are not uncommon and can lead to devastating neurovascular complications if unrecognized. Thus, it is important for spine surgeons to be familiar with various posterior atlantoaxial fusion techniques along with a thorough knowledge of various vascular anomalies in the CVJ. Intimate knowledge of the various surgical techniques in combination with an appreciation for anatomical variances, allows the surgeon develop a customized surgical plan tailored to each patient's particular pathology and individual anatomy. In this article, we aim to provide a comprehensive review of existing posterior C1-2 fusion techniques along with a review of common vascular anomalies in the CVJ.

Clinical Importance of the Posterior Inferior Cerebellar Artery: A Review of the Literature

The posterior inferior cerebellar artery (PICA), with its unique anatomical complexity, is of great clinical importance and involved in many diseases including aneurysm, ischemic stroke, neurovascular compression syndrome (NVCS), arteriovenous malformation (AVM), and brain tumor. However, a comprehensive systematic review of the importance of the PICA is currently lacking. In this study, we perform a literature review of PICA by searching all the associated papers in the PUBMED database hoping to provide a better understanding of the artery. The PICA has tortuous and variable course and territory, divided into 5 segments. Various aneurysms involving PICA were not uncommon, of which the treatment is challenging. The PICA infarct typically manifests lateral medullary syndrome (LMS) and is more likely to cause mass effects. The PICA frequently compresses the medulla and the cranial nerves resulting in various neurovascular compression syndromes (NVCS). Arteriovenous malformation (AVM) fed by PICA are associated with aneurysm and dissection which have high risk of rupture and worse outcome. PICA injured by head trauma can cause fatal SAH. VA terminating in PICA probably cause Bow hunter's syndrome (BHS). The PICA supplies many brain tumors and can be used in intracerebellar chemotherapy. The PICA can be exposed and injured during surgeries especially in telovelar approach, and it also plays an important role in bypass surgeries, hinting the surgical importance of PICA. In conclusion, PICA is very important in clinical practice.

Anomalous vasculature in the neck diagnosed by ultrasound

Anomalous vascular anatomy was detected in the neck of a 52-year-old female with a Klippel-Feil anomaly. Ultrasound identified three separate arteries in the left carotid sheath without any branching or bifurcations. The vascular waveforms were used to identify the vessels as the internal carotid artery, external carotid artery and vertebral artery. This rare vascular anomaly was confirmed with CT angiography.

Accuracy evaluation of placements of three different alternative C2 screws using the freehand technique in patients with high riding vertebral artery

An observational study.To evaluate the safeties of placing three different alternative C2 screws using the freehand technique under high riding vertebral artery (HRVA) and to analyze the C2 morphometry in patients with HRVA.A retrospective analysis of radiologic data was performed on patients that underwent C2 instrumentation from September 2004 to December 2017. Two hundred fifty-one patients were included, and 90 of these patients (35.9%) had a unilateral or bilateral HRVA. We placed three alternative C2 screws including superior pars, inferior pars, and translaminar screws. Computed tomography was used to assess cortical breeches of screw placement and obtain morphometric measurements of C2 pars and lamina, that is, superior pars height/length, inferior pars length, and laminar thickness/length. We used the modification of the all India Institute of Medical Sciences outcome to define cortical breach.In total, 117 alternative C2 screws were inserted in 90 patients; 7 superior pars screws (6%), 69 inferior pars screws (59.0%), and 41 translaminar (35%) screws. Although cortical breaches occurred during 31 screw placements (26.5%), these were unacceptable in only two cases (1.7%). No symptomatic neurovascular complication was observed after screw placement in any case. Mean height of C2 superior pars was 3.8 ± 1.8 mm and mean thickness of C2 lamina was 5.2 ± 1.1 mm. Mean lengths of superior pars, inferior pars, and lamina were 17.8 ± 3.0 mm, 13.6 ± 2.2 mm, and 26.7 ± 3.3 mm, respectively. Superior pars height and lamina thickness < 3.5 mm that was a minimal diameter of cervical screw were 49.6% and 6.8%, alternative C2 screw was not available in these cases.Placements of alternative C2 screws using the freehand technique were achieved accurately and safely in patients with HRVA. However, preoperative morphometric evaluation is essential to determine the best option for C2 instrumentation and C2 screw length to avoid neurovascular complications.

Posterior Inferior Cerebellar Artery Infarction Originating at C1-2 after C1-2 Fusion

Vertebral artery injuries associated with C1 lateral mass screw insertion rarely occur during C1-2 fusion. The posterior inferior cerebellar artery (PICA) is uncommonly located at the C1 lateral mass insertion position. A 71-year-old woman with atlanto-axial subluxation and cord compression underwent C1-2 fusion. Sixth nerve palsy and diplopia were detected postoperatively, and decreased consciousness occurred on postoperative day 4. Brain magnetic resonance image (MRI) and computed tomography (CT) revealed PICA infarction. In the preoperative CT angiography, the PICA originated between the C1 and C2 level. In the postoperative CT scan, the PICA was not visible. The patient was treated conservatively for two weeks and recovered. PICA originating between the C1 and C2 level comprises 1.1–1.3% of cases. Therefore, vertebral artery anomalies should be evaluated prior to C1-2 fusion to prevent vessel injuries.

Bilateral Extradural Posterior Inferior Cerebellar Artery Origins Where Vertebral Artery Ascends Between Transverse Foramina of C-2 and C-1, with Simultaneous Right Double Origin PICA: Rare Case Report and Literature Review

BACKGROUND

The location of the origin of the posterior inferior cerebellar artery (PICA) is highly variable. An extracranial origin PICA from the vertebral artery (VA) is not rare. But the PICA originated extradurally where the VA ascends between the transverse foramina of C-2 and C-1, a rare anatomic variant. Double-origin PICA is another rare anatomic variant observed in 1%-4% of patients in whom 2 PICA branches converge distally.

CASE DESCRIPTION

We present a rare cadaveric anatomy case in which both PICAs originated extradurally between the vertebrae C1 and C2, a simultaneously existing right double-origin PICA. For this case, the right PICA was a double-origin PICA, including 1 extradural origin in which the VA ascends between the transverse foramina of C-2 and C-1 and another being intradural and intracranial.

CONCLUSIONS

To our knowledge, this is the first report of a cadaveric anatomy case of bilateral PICA that originated extradurally between the vertebrae C-1 and C-2, and simultaneously there existed a right double-origin PICA. Such a case is rare, but understanding of the anatomic variation is important. To avoid complications during surgery at the craniovertebral junction, these potential variations should be correctly identified preoperatively.

Morphologic variations of the second cervical vertebra in Down syndrome compared with age-matched peers

OBJECTIVEAtlantoaxial instability is an important cause of pain and neurological dysfunction in patients with Down syndrome (DS), frequently requiring instrumented fusion of the upper cervical spine. This study provides a quantitative analysis of C2 morphology in DS patients compared with their peers without DS to identify differences that must be considered for the safe placement of instrumentation.METHODSA retrospective chart review identified age-matched patients with and without DS with a CT scan of the cervical spine. Three-dimensional reconstructions of these scans were made with images along the axis of, and perpendicular to, the pars, lamina, facet, and transverse foramen of C2 bilaterally. Two of the authors performed independent measurements of anatomical structures using these images, and the average of the 2 raters' measurements was recorded. Pedicle height and width; pars axis length (the distance from the facet to the anterior vertebral body through the pars); pars rostrocaudal angle (angle of the pars axis length to the endplate of C2); pars axial angle (angle of the pars axis length to the median coronal plane); lamina height, length, and width; lamina angle (angle of the lamina length to the median coronal plane); and transverse foramen posterior distance (the distance from the posterior wall of the transverse foramen to the tangent of the posterior vertebral body) were measured bilaterally. Patients with and without DS were compared using a mixed-effects model accounting for patient height.RESULTSA total of 18 patients with and 20 patients without DS were included in the analysis. The groups were matched based on age and sex. The median height was 147 cm (IQR 142-160 cm) in the DS group and 165 cm (IQR 161-172 cm) in the non-DS group (p < 0.001). After accounting for variations in height, the mean pars rostrocaudal angle was greater (50.86° vs 45.54°, p = 0.004), the mean transverse foramen posterior distance was less (-1.5 mm vs +1.3 mm, p = 0.001), and the mean lamina width was less (6.2 mm vs 7.7 mm, p = 0.038) in patients with DS.CONCLUSIONSPatients with DS had a steeper rostrocaudal trajectory of the pars, a more posteriorly positioned transverse foramen posterior wall, and a narrower lamina compared with age- and sex-matched peers. These variations should be considered during surgical planning, as they may have implications to safe placement of instrumentation.

Differences in fixation strength among constructs of atlantoaxial fixation

OBJECTIVETo avoid jeopardizing an aberrant vertebral artery, there are three common options in placing a C2 screw, including pedicle, pars, and translaminar screws. Although biomechanical studies have demonstrated similar strength among these C2 screws in vitro, there are limited clinical data to address their differences in vivo. When different screws were placed in each side, few reports have compared the outcomes. The present study aimed to evaluate these multiple combinations of C2 screws.METHODSConsecutive adult patients who underwent posterior atlantoaxial (AA) fixation were retrospectively reviewed. Every patient uniformly had bilateral C1 lateral mass screws in conjunction with 2 C2 screws (1 C2 screw on each side chosen among the three options: pedicle, pars, or translaminar screws, based on individualized anatomical consideration). These patients were then grouped according to the different combinations of C2 screws for comparison of the outcomes.RESULTSA total of 63 patients were analyzed, with a mean follow-up of 34.3 months. There were five kinds of construct combinations of the C2 screws: 2 pedicle screws (the Ped-Ped group, n = 24), 2 translaminar screws (the La-La group, n = 7), 2 pars screws (the Pars-Pars group, n = 6), 1 pedicle and 1 pars screw (the Ped-Pars group, n = 7), and 1 pedicle and 1 translaminar screw (the Ped-La group, n = 19). The rate of successful fixation in each of the groups was 100%, 57.1%, 100%, 100%, and 78.9% (Ped-Ped, La-La, Par-Par, Ped-Par, and Ped-La, respectively). The patients who had no translaminar screw had a higher rate of success than those who had 1 or 2 translaminar screws (100% vs 73.1%, p = 0.0009). Among the 5 kinds of construct combinations, 2 C2 pedicle screws (the Ped-Ped group) had higher rates of success than 1 C2 pedicle and 1 C2 translaminar screw (the Ped-La group, p = 0.018). Overall, the rate of successful fixation was 87.3% (55/63). There were 7 patients (4 in the Ped-La group and 3 in the La-La group) who lost fixation/reduction, and they all had at least 1 translaminar screw.CONCLUSIONSIn AA fixation, C2 pedicle or pars screws or a combination of both provided very high success rates. Involvement of 1 or 2 C2 translaminar screws in the construct significantly lowered success rates. Therefore, a C2 pars screw is recommended over a translaminar screw.

The C2 Pedicle Width, Pars Length, and Laminar Thickness in Concurrent Ipsilateral Ponticulus Posticus and High-Riding Vertebral Artery: A Radiological Computed Tomography Scan-Based Study

STUDY DESIGN

Retrospective radiological study.

PURPOSE

We aimed to determine the prevalence of ponticulus posticus (PP) and high-riding vertebral artery (HRVA) occurring simultaneously on the same side (PP+HRVA) and in cases of PP+HRVA, to assess C2 radio-anatomical measurements for C2 pars length, pedicle width, and laminar thickness.

OVERVIEW OF LITERATURE

PP and HRVA predispose individuals to vertebral artery injuries during atlantoaxial fixation. In cases of PP+HRVA, the construct options thus become limited.

METHODS

Consecutive computed tomography scans (n=210) were reviewed for PP and HRVA (defined as an internal height of <2 mm and an isthmus height of <5 mm). In scans with PP+HRVA, we measured the ipsilateral pedicle width, pars length, and laminar thickness and compared them with controls (those without PP or HRVA).

RESULTS

PP was present in 14.76% and HRVA in 20% of scans. Of the 420 sides in 210 scans, PP+HRVA was present on 13 sides (seven right and six left). In scans with PP+HRVA, the C2 pars length was shorter compared with controls (13.69 mm in PP+HRVA vs. 20.65 mm in controls, p<0.001). The mean C2 pedicle width was 2.53 mm in scans with PP+HRVA vs. 5.83 mm in controls (p<0.001). The mean laminar thickness was 4.92 and 5.48 mm in scans with PP+HRVA and controls, respectively (p=0.209).

CONCLUSIONS

The prevalence of PP+HRVA was approximately 3% in the present study. Our data suggest that, in such situations, C2 pedicle width and pars length create important safety limitations for a proposed screw, whereas the translaminar thickness appears safe for a proposed screw.

Late Subaxial Lesion after Overcorrected Occipitocervical Reconstruction in Patients with Rheumatoid Arthritis

Study Design

Retrospective case-control study, level 4.

Purpose

To clarify the risk factors for late subaxial lesion after occipitocervical (O-C) reconstruction. We examined cases requiring fusion-segment-extended (FE) reconstruction in addition to/after O-C reconstruction.

Overview of Literature

Patients with rheumatoid arthritis (RA) frequently require O-C reconstruction surgery for cranio-cervical lesions. Acceptable outcomes are achieved via indirect decompression using cervical pedicle screws and occipital plate–rod systems. However, late subaxial lesions may develop occasionally following O-C reconstruction.

Methods

O-C reconstruction using cervical pedicle screws and occipital plate–rod systems was performed between 1994 and 2007 in 113 patients with RA. Occipito-atlanto-axial (O-C2) reconstruction was performed for 89 patients, and occipito-subaxial cervical (O-under C2) reconstruction was performed for 24 patients. We reviewed the cases of patients requiring FE reconstruction (fusion extended group, FEG) and 26 consecutive patients who did not require FE reconstruction after a follow-up of >5 years (non-fusion extended group, NEG) as controls.

Results

FE reconstructions were performed for nine patients at an average of 45 months (range, 24–180 months) after O-C reconstruction. Of the 89 patients, three (3%) underwent FE reconstruction in cases of O-C2 reconstruction. Of the 24 patients, five (21%) underwent FE reconstruction in cases of O-under C2 reconstruction (p=0.003, Fisher exact test). Age, sex, RA type, and neurological impairment stage were not significantly different between FEG and NEG. O-under C2 reconstruction, larger correction angle (4° per number of unfixed segment), and O-C7 angle change after O-C reconstruction were the risk factors for late subaxial lesions on radiographic assessment.

Conclusions

Overcorrection of angle at fusion segments requiring O-C7 angle change was a risk factor for late subaxial lesion in patients with RA with fragile bones and joints. Correction should be limited, considering the residual mobility of the cervical unfixed segments.

Freehand technique for C2 pedicle and pars screw placement: is it safe?

BACKGROUND CONTEXT

During placement of C2 pedicle and pars screws, intraoperative fluoroscopy is used so that neurovascular complications can be avoided, and screws can be placed in the proper position. However, this method is time consuming and increases radiation exposure. Furthermore, it does not guarantee a completely safe and accurate screw placement.

PURPOSE

The objective of this study was to evaluate the safety of the C2 pedicle and pars screw placement without fluoroscopic or other guidance methods.

STUDY DESIGN

This is a retrospective comparative study.

PATIENT SAMPLE

One hundred ninety-eight patients who underwent placement of C2 pedicle or pars screws without any intraoperative radiographic guidance were included in the study.

OUTCOME MEASURES

Medical records and postoperative computed tomography (CT) scans were evaluated.

MATERIALS AND METHODS

Clinical data were reviewed for intraoperative and postoperative complications. The accuracy of screw placement was evaluated with postop CT scans using a previously published cortical-breach grading system (described by the location and the percentage of the screw diameter over the cortical edge [0=none, Grade I≤25% of the screw diameter, Grade II=26%-50%, Grade III=51%-75%, and Grade IV=76%-100%]).

RESULTS

A total of 148 pedicle screws and 219 pars screws were inserted by two experienced surgeons. There were no cases of cerebral spinal fluid leakage and no neurovascular complications during screw placement. Postoperative CT scans were available for 76 patients, which included 52 pedicle screws and 87 pars screws. For cases with C2 pedicle screws, there were 12 breaches (23%); these included 10 screws with a Grade I breach (19%), 1 screw with a Grade II breach (2%), and 1 screw with a Grade IV breach (2%). Lateral breaches occurred in seven screws (13%), inferior breaches occurred in three screws (6%), and superior breaches occurred in two screws (4%). For cases with C2 pars screws, there were 10 breaches (11%); these included 6 screws with a Grade I breach (7%), 2 screws with a Grade II breach (2%), and 2 screws with a Grade IV breach (2%). Medial breaches were found in four (5%), lateral breaches in two (2%), inferior breaches in two (2%), and superior breaches in two (2%). Two of the cases with superior breaches (one for pedicle and one for pars) experienced occipital neuralgia months after surgery. There was no statistically significant difference in the incidence of overall and high-grade breaches between the groups (p=.07 and 1.0, respectively).

CONCLUSIONS

Although even in experienced hands up to 23% of C2 pedicle screws and 11% of C2 pars screws placed using a freehand technique without guidance may be malpositioned, a clear majority of malpositioned screws demonstrated a low-grade breach, and only 2 of 198 patients (1%) experienced complications related to screw placement.

How Common Is the Ponticulus Posticus?: A Computed Tomography Based Analysis of 2917 Patients

STUDY DESIGN

A computed tomography (CT) study of the morphology of the C1 vertebra.

OBJECTIVE

Is to determine the prevalence of ponticulus posticus (PP) by analyzing CT scans performed on a large, diverse population in the northeast United States. This study also proposes a CT-based classification system both to aid in unifying the description of PP, and to aid in future research.

SUMMARY OF BACKGROUND DATA

The prevalence of PP varies from 5% to 68% in published studies. There may be geographic variation in the prevalence of PP. Our objective was to establish the prevalence of PP in the general population, and to develop a comprehensive classification system to describe PP.

METHODS

We evaluated cervical spine CT scans performed on patients in the emergency room of a level I trauma center over a 1-year period (January 1, 2014-December 31, 2014). The CT images were evaluated for the presence of a PP, and if present the following demographic data were collected: age, sex, race/ethnicity, and body mass index (BMI). We propose a novel classification system to standardize the description of PP identified on CT scan.

RESULTS

Two thousand, nine hundred and seventeen cervical spine CT scans were reviewed in this study. The prevalence of PP was 22.5%. Men had a higher prevalence of PP than women (53.5% male vs. 46.5% female P ≤ 0.01). When compared with the overall population, African-Americans were more likely to have a PP (P ≤ 0.01), while Caucasian patients were less likely (P ≤ 0.01). The novel classification consisted of a two letter designation for each patient, with the first letter denoting the right sided arch and the second letter the left sided arch. Each side of the arch described as an A, B, or C type. The A type had no presence of a PP, B type had in incomplete PP, and C type had a complete PP. The most common type of a PP was CC encompassing 25% of the patients. The presence of a PP was more common in the left sided arch than the right side (B and C type Left 89.2% vs. B and C type Right 84.7%, P = 0.02).

CONCLUSION

We found a 22.5% prevalence of PP in 2917 patients undergoing a cervical spine CT. This is the largest study to evaluating the prevalence of PP.

LEVEL OF EVIDENCE

4.

The Ponticulus Posticus as Risk Factor for Screw Insertion into the First Cervical Lateral Mass

BACKGROUND

Awareness of the osseous anomaly of ponticulus posticus (PP) is crucial in avoiding vertebral artery (VA) injuries during C1 instrumentation. The aim of this study was to investigate PP and its relationship with the VA with three-dimensional computed tomography angiography.

METHODS

PP and the VA were investigated as intraoperative landmarks. The intersection of the VA to the posterior arch of C1 and the medial line and the posterior arch and VA curve around lateral masses were measured as intraoperative references.

RESULTS

PP was identified in 14.3% of samples. The anomaly was more common in women and on the right side. Of cases, 48.2% had PP bilaterally. In PP cases, the VA had variable courses through C2 before it passed under its bony bridges on the posterior arch of C1. Mean distances were found at the intersection of the VA to the posterior arch of C1 and the medial line to be larger and the posterior arch of C1 and the VA curve around lateral masses to be narrower than normal cases. Dual computed tomography scan data from C1 with PP were used to create three-dimensional patient-specific life-sized cervical spine models. Models revealed how the bone bridge affected the VA. The feasibility (>4 mm) of a safe lateral mass screw fixation was not influenced by PP anomalies.

CONCLUSIONS

The presence of the PP loop can limit space available for placement of the screw through the bony elements of C1. Standard screw techniques are contraindicated owing to the unacceptable high risk of VA injury.

C1-2 Fixation Approach for Patients With Vascular Irregularities: A Case Report

In posterior spinal fusion (PSF), the vertebral artery is most vulnerable to injury at C1-2. C2 pedicle screws are often placed into the dorsomedial isthmus of C2. Alternative techniques include C2 laminar screws and wiring techniques. A 67-year-old male underwent PSF for persistent severe intractable neck pain and degeneration at C1-2. The patient had an enlarged left vertebral artery with midline migration into the C2 body. This pattern was within one standard deviation of normal; however, it rendered typical placement of a C2 pedicle screw unsafe. As a salvage, a C2 laminar screw was placed on the left to avoid risk of vertebral artery injury. The operation and recovery were without complication. C2 laminar screws can be viable alternatives to C2 pedicle screws in cases of midline vertebral artery migration or other vascular anomalies preventing normal safe placement of C2 pedicle screws.

Posterior inferior cerebellar artery with an extradural origin from the V3 segment: higher incidence on the nondominant vertebral artery

OBJECTIVE The posterior inferior cerebellar artery (PICA) and the vertebral artery (VA) often exhibit anatomical variations at the craniovertebral junction (CVJ). An example of this is the PICA originating extradurally from the V₃ segment of the VA. To date, some cadaveric investigations have been reported, but the incidence and relationship of this variation to the VA and the atlas as observed on clinical imaging have not been discussed. This study evaluated the prevalence of PICAs originating from the V₃ on CT scanning. Other variations of the atlas and VA were also analyzed. METHODS CT images from a series of 153 patients who underwent 3D CT angiography (CTA) were analyzed, and variations of the PICA, VA, and atlas were investigated. RESULTS A total of 142 patients (284 sides) were analyzed; 11 patients (7.2%) were excluded due to poor image quality. The most common VA variation was the PICA originating from V₃ (9.5% of 284 sides), which was more frequently observed on the nondominant VA than the dominant VA (22.5% vs 6.25%, p = 0.0005). A VA with a PICA end was identified in 4 sides (1.4%), which is the same incidence as observed in the persistent first intersegmental VA (1.4%). VA fenestration was only found in 1 side (0.35%). Regarding the atlas, ponticulus posticus was observed in 24 sides (8.5%). There was no relationship between the incidence of ponticulus posticus and the variations of the VA. CONCLUSIONS A PICA originating from V₃ was the most common VA variation at the CVJ and was more common on the nondominant VA. Three-dimensional CTA is useful for the evaluation of this variance. Surgeons should be mindful of this variation during operations.