Prevalence of high-riding vertebral arteries and narrow C2 pedicles among Central-European population: a computed tomography-based study

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.

Advancements in Robotic-Assisted Spine Surgery

Applications and workflows around spinal robotics have evolved since these systems were first introduced in 2004. Initially approved for lumbar pedicle screw placement, the scope of robotics has expanded to instrumentation across different regions. Additionally, precise navigation can aid in tumor resection or spinal lesion ablation. Robot-assisted surgery can improve accuracy while decreasing radiation exposure, length of hospital stay, complication, and revision rates. Disadvantages include increased operative time, dependence on preoperative imaging among others. The future of robotic spine surgery includes automated surgery, telerobotic surgery, and the inclusion of machine learning or artificial intelligence in preoperative planning.

Radiologic Examination of High Riding Vertebral Artery and Analysis of Secure Areas

OBJECTIVE

To radiologically examine the pedicle, lamina, and vertebral artery foraminal anatomies at the C2 vertebra for pedicular and laminar screw instrumentation at the axis in a Turkish population.

METHODS

From 2018 to 2019, we evaluated 100 patients who underwent cervical computed tomography (CT) for various reasons (excluding cervical pathologies) at Marmara University Hospital. The C2 pedicles were measured on CT images using measurement tools. In addition, axial computed tomography was performed at 0.1 mm intervals. Bilateral measurements were performed for each case.

RESULTS

The median right and left pedicle axial diameters were 5.01 and 5.09 mm, respectively for the male patients and 4.31 and 4.38 mm for the female patients, showing a statistically significant difference between the sexes (P < 0.01). Of the patients, 15% had narrow pedicles. The pedicle sagittal diameters were smaller than 5 mm in 30% of the computed tomographic series. The internal height was <2 mm in 4% of the cases.

CONCLUSIONS

Our findings suggest significant individual and sex-related differences. Vertebral artery groove anomalies are commonly observed. Before performing a posterior craniocervical instrumentation surgery, a computed tomography (CT) examination is beneficial because high-riding vertebral arteries must be kept in mind in determining the appropriate screw diameter and screw trajectory.

The association between unilateral high-riding vertebral artery and atlantoaxial joint morphology: a multi-slice spiral computed tomography study of 396 patients and a finite element analysis

BACKGROUND CONTEXT

A high-riding vertebral artery (HRVA) can deviate too medially, too posteriorly, or too superiorly to allow the safe insertion of screws. However, it is unknown whether the presence of a HRVA is associated with morphological changes of the atlantoaxial joint.

PURPOSE

To investigate the association between HRVA and atlantoaxial joint morphology in patients with and without HRVA.

STUDY DESIGN

A retrospective case-control study and finite element (FE) analysis.

PATIENT SAMPLE

A total of 396 patients with cervical spondylosis underwent multi-slice spiral computed tomography (MSCT) of cervical spine at our institutions from 2020 to 2022.

OUTCOME MEASURES

A series of atlantoaxial joint morphological parameters, including C2 lateral mass settlement (C2 LMS), C1-2 sagittal joint inclination (C1-2 SI), C1-2 coronal joint inclination (C1-2 CI), atlanto-dental interval (ADI), lateral atlanto-dental interval (LADI), and C1-2 relative rotation angle (C1-2 RRA) were measured, and lateral atlantoaxial joints osteoarthritis (LAJs-OA) was recorded. The stress distribution on the C2 facet surface under different torques of flexion-extension, lateral bending, and axial rotation was analyzed by FE models. A 2-Nm moment was applied to all models to determine the range of motion (ROM).

METHODS

A total of 132 consecutive cervical spondylosis patients with unilateral HRVA were enrolled in the HRVA group, and 264 patients without HRVA matched for age and sex were enrolled in the normal (NL) group. Atlantoaxial joint morphological parameters were compared between two sides of C2 lateral mass within HRVA or NL group, and between HRVA and NL groups. A 48-year-old woman with cervical spondylosis without HRVA was selected for cervical MSCT. A three-dimensional (3D) FE intact model of the normal upper cervical spine (C0-C2) was created. We established the HRVA model by simulating atlantoaxial morphological changes of unilateral HRVA with FE method.

RESULTS

The C2 LMS was significantly smaller on the HRVA side than that on the non-HRVA side in the HRVA group, but C1-2 SI, C1-2 CI, and LADI on HRVA side were significantly larger than those on non-HRVA side. There was no significant difference between left and right sides in the NL group. The difference in C2 LMS (d-C2 LMS) between HRVA side and non-HRVA side in the HRVA group was larger than that in the NL group (P < 0.05). Meanwhile, the differences in C1-2 SI (d-C1/2 SI), C1-2 CI (d-C1/2 CI), and LADI (d-LADI) in the HRVA group were significantly larger than those in the NL group. The C1-2 RRA in the HRVA group was significantly larger than that in the NL group. Pearson correlations showed that d-C1/2 SI, d-C1/2 CI, and d-LADI were positively associated with d-C2 LMS (r=0.428, 0.649, 0.498, respectively, p<.05 for all). The incidence of LAJs-OA in the HRVA group (27.3%) was significantly larger than that in the NL group (11.7%). Compared with the normal model, the ROM of C1-2 segment declined in all postures of the HRVA FE model. We found a larger distribution of stress on the C2 lateral mass surface of the HRVA side under different moment conditions.

CONCLUSIONS

We suggest that HRVA affects the integrity of the C2 lateral mass. This change in patients with unilateral HRVA is associated with the nonuniform settlement of the lateral mass and an increase in the lateral mass inclination, which may further affect the degeneration of the atlantoaxial joint because of the stress concentration on the C2 lateral mass surface.

Robotics in Cervical Spine Surgery: Feasibility and Safety of Posterior Screw Placement

Objective: Robot-assisted (RA) techniques have been widely investigated in thoracolumbar spine surgery. However, the application of RA methods on cervical spine surgery is rare due to the complex morphology of cervical vertebrae and catastrophic complications. Thus, the feasibility and safety of RA cervical screw placement remain controversial. This study aims to evaluate the feasibility and safety of RA screw placement on cervical spine surgery.Methods: A comprehensive search on PubMed, Cochrane Library, Embase Database, Web of Science, Chinese National Knowledge Databases, and Wanfang Database was performed to select potential eligible studies. Randomized controlled trials (RCTs), comparative cohort studies, and case series reporting the accuracy of cervical screw placement were included. The Cochrane risk of bias criteria and Newcastle-Ottawa Scale criteria were utilized to rate the risk of bias of the included literatures. The primary outcome was the rate of cervical screw placement accuracy with robotic guidance; subgroup analyses based on the screw type and insertion segments were also performed.Results: One RCT, 3 comparative cohort studies, and 3 case series consisting of 160 patients and 719 cervical screws were included in this meta-analysis. The combined outcomes indicated that the rates of optimal and clinically acceptable cervical screw placement accuracy under robotic guidance were 88.0% (95% confidence interval [CI], 84.1%–91.4%; p = 0.073; I² = 47.941%) and 98.4% (95% CI, 96.8%–99.5%; p = 0.167; I² = 35.954%). The subgroup analyses showed that the rate of optimal pedicle screw placement accuracy was 88.2% (95% CI, 83.1%–92.6%; p = 0.057; I² = 53.305%); the rates of optimal screw placement accuracy on C1, C2, and subaxial segments were 96.2% (95% CI, 80.5%–100.0%; p = 0.167; I² = 44.134X%), 89.7% (95% CI, 80.6%–96.6%; p = 0.370; I² = 0.000X%), and 82.6% (95% CI, 70.9%–91.9%; p = 0.057; I² = 65.127X%;), respectively.Conclusion: RA techniques were associated with high rates of optimal and clinically acceptable screw positions. RA cervical screw placement is accurate, safe, and feasible in cervical spine surgery with promising clinical potential.

Percutaneous Fixation of Levine-Edwards Type II Hangman's Fractures Under the Guidance of an Orthopedic Robot

There is no consensus regarding the optimal treatment for unstable hangman's fractures. Conservative treatment, although time-consuming and associated with complications such as nonunion, neck stiffness, and pseudarthrosis formation, is still preferred by many surgeons. With the development of minimally invasive techniques, surgical treatment is trending in recent years. We have proposed a minimally invasive, robot-assisted technique for the treatment of Levine-Edwards (L-E) type II hangman's fractures; this could improve the patients' quality of life. Five patients with L-E type II hangman's fractures were treated operatively initially. After closed reduction, the C2 pedicle screws were inserted percutaneously with the guidance of the orthopedic surgical robot. The positions of pedicle screws were verified by intraoperative 3-dimensional C-arm fluoroscopy. Regular follow-ups were performed to evaluate the radiological and functional outcomes. Postoperatively, all the fractures have healed with an average healing time of 3.5 months, the functional outcomes were satisfactory at last follow-up, and there was no neurovascular injury associated with this technique. The 3D-fluoroscopy-based, robot-assisted C2 pedicle screw fixation is a safe, precise, and feasible method for the initial treatment of L-E type II hangman's fractures. [Orthopedics. 2023;46(1):59-63.].

Ideal entry point and trajectory for C2 pedicle screw placement in basilar invagination patients with high-riding vertebral artery based on 3D computed tomography

BACKGROUND

C2 pedicle screw placement in patients with basilar invagination (BI) is fraught with risks because of a high incidence of anatomical variations and high-riding vertebral artery (HRVA). However, no study can be found in the literature that attempted to identify the ideal entry point and trajectory through the C2 pedicle in BI patients with HRVA.

PURPOSE

To investigate the parameters of ideal entry point and trajectory for C2 pedicle screw placement in BI patients with HRVA and compare them with those in BI patients without HRVA and patients without BI as control. These parameters would serve as a guide to pedicle screw placement.

STUDY DESIGN

A retrospective comparative study.

PATIENT SAMPLE

A total of 396 patients (198 consecutive BI patients and 198 matched patients without BI as control) and 792 unilateral pedicles from April 2017 to October 2021 at two medical centers were included.

OUTCOME MEASURES

The insertion parameters of mediolateral angle, surface distance, cephalad angle, and vertical distance from the superior border of the lamina were the primary outcome measures for the reference of C2 pedicle screw placement. Furthermore, factors that affect the primary insertion parameters were assessed via multiple linear regression analyses.

METHOD

According to the diagnosis of BI and HRVA, the unilateral pedicles were assigned into HRVA of BI, non-HRVA of BI, HRVA of control, and non-HRVA of control groups. Subgroup analyses based on Goel types A and B were also performed. Moreover, vertebral artery (VA) anomalies that might result in potentially serious complications were identified and systematically compared.

RESULTS

The measurements of insertion parameters in BI patients with HRVA indicated a mean mediolateral angle of 27.42°, a mean cephalad angle of 43.02°, a mean surface distance of 9.74 mm, and a mean vertical distance from the superior border of the lamina of 3.85 mm. Compared with that in BI patients without HRVA, the measurements suggested that the entry point in BI patients with HRVA should be shifted upward by 0.38 mm and the trajectory should be angled cephalad by 6.05° and medially by 4.78°. In the control group, changes in the insertion parameters between HRVA and non-HRVA showed a similar trend to the BI group. Multiple linear regression showed that mediolateral angle was significantly associated with the male gender (B=-0.930, p=.017) and the diagnoses of HRVA (B=6.964, p<.001), Goel type A (B=-1.656, p=.003), and Goel type B (B=0.981, p=.030). Moreover, cephalad angle was significantly associated with the length of lateral mass (B=-0.319, p=.001) and the diagnoses of HRVA (B=3.254, p<.001) and Goel type A (B=6.924, p<.001). The VA anomalies were significantly higher in the BI group than in the control group.

CONCLUSIONS

The insertion parameters of the ideal entry point and trajectory for C2 screw placement in BI patients with HRVA were remarkably different from those of non-HRVA of BI, HRVA of control, and non-HRVA of control cohorts. Preoperative 3D computed tomography (CT) and CT angiography are highly recommended in such patients to improve intraoperative safety and reduce postoperative complications.

[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.

EuroQol-5 dimensions health-related quality of life questionnaire in craniovertebral instability treated with posterior fixation with or without occipital plating: A comparative study with matched datasets

Objective:

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