Risk Of Vertebral Artery Injury Research Articles

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

To determine the relationship between the uncinate process (UP) and vertebral artery (VA) from a radiologic view and to confirm the surgical safety margin to minimize the risk of VA injury during anterior cervical approaches. We retrospectively reviewed computed tomography angiography of 205 patients by using a contrast-enhanced computed tomography angiography protocol of the VA. Four kinds of images were simultaneously reconstructed to measure all the parameters associated with VA and UP of cervical spine. The shortest distance from the UP's tip to the VA's medial border (P < 0.001) was at the C-6 level (2.9 ± 0.9 mm on the left and 3.2 ± 1.3 mm on the right), and the longest distance (P < 0.001) was at the C-3 level on both sides. The distance between UP's tip and the medial border of the ipsilateral VA was statistically significantly different at each cervical level, and the right distance was larger than the left (P < 0.05). We found the height of UP gradually increased from C-3 to C5-level and then decreased from C-5 to C-7 level for both sides. The mean distance between the medial borders of left UP and left VA was on average 7.5 ± 1.4 mm. The diameter of VA was on average 3.4 ± 0.6 mm on the left side and 3.2 ± 0.7 mm on the right. The diameter of the VA was statistically significantly different on both sides, and the left side was larger than the right (P < 0.05). Detailed radiologic anatomy of VA and UP was reviewed in this study. A deep understanding of the correlation between the UP and VA is essential to perform anterior cervical spine surgery safely and ensure adequate spinal canal decompression.

A rotary trans-osseous ultrasound blood flow detection method for endoscopic application

Due to the small size and proximity to the spinal cord and vertebral artery, the cervical pedicle screw fixation procedure remains to be challenging in clinical practice. The screw misplacement has a high probability of occurrence of severe complications. How to prevent direct injury to the vertebral artery is a vital study focus in cervical spine surgery. In this work, a trans-osseous ultrasound Doppler method is proposed to explore the possibility of detecting blood flow through thin cortical bone. A miniature single-element prototype probe with a center frequency of 2.5 MHz is prepared. With the classical pulse-echo acquisition, a Spectral Power Index (SPI) algorithm based on Spectral Doppler and sliding window traversal is designed to enhance the Doppler signal intensity. In vitro and in vivo experiments were conducted to investigate the feasibility of this method. The results of in vitro experiments suggest that the anticoagulated bovine blood flowing at a mean velocity of 15 cm/s to 80 cm/s is detectable when the thickness of cortical bone is 0.7 ± 0.1 mm. The in vivo experiment showed that the large blood vessel with a diameter of about 3 mm (radial artery) can be detected through thin cortical bone (thickness of 0.7 ± 0.1 mm). The proposed trans-osseous Doppler method achieves artery detection through thin cortical bone, which has demonstrated the possibility of intraoperative vessel pre-warning. The present study poses a promising strategy to reduce the risk of vertebral artery injury and misalignment rate in the cervical pedicle screw insertion procedure.

Abnormal Terminal Vertebral Artery in Atlantoaxial Dislocation: A Rare Case Report

Atlantoaxial dislocation (AAD), is a challenging disorder of the craniocervical junction. Because of its deep location and intricate anatomic structure, the craniocervical junction is always a difficult region for spine surgery. (1) Risk of vertebral artery injury makes the surgery difficult. Patient having an abnormal vertebral artery, like our patient, makes the situation more complicated. Bang. J Neurosurgery 2022; 11(2): 118-121

The Comparison Between Transarticular Screw Fixation and Segmental Screw-Rod Fixation for Posterior Fusion of the C1-2 Segment: A Systematic Review and Meta-Analysis

Both transarticular screw fixation (TAS) and segmental screw-rod fixation (SF) have been widely performed for C1-2 fusion; however, just only small clinical studies and a few meta-analyses comparing the 2 surgical techniques for C1-2 posterior fusion have been reported. We searched the Cochrane, Embase, and Medline databases for articles comparing the intraoperative and postoperative outcomes of TAS and SF for C1-2 posterior fusion with April 14, 2022, as the publication cutoff date. The odds ratio (OR) and standardized mean difference were used to analyze differences in outcomes between the 2 abovementioned surgical techniques. A P value<0.05 was considered statistically significant. A total of 5101 publications were assessed, and 6 studies were finally included in the study. In terms of the fusion rate, SF produced significantly better outcomes than TAS did (OR=2.96, P=0.02). With respect to surgical outcomes, blood loss and operation times were significantly lower in the TAS group than those in the SF group (P=0.008 and P<0.00001, respectively). The rate of vertebral artery injury was significantly lower in the SF group than that in the TAS group (OR=3.95, P=0.04). However, other complications, such as screw malposition, infection, hardware failure, and nonunion, were not significantly different between the 2 groups. SF showed a greater fusion rate and lower risk of vertebral artery injury than TAS did, but TAS showed less blood loss and lower operation times than SF.

C2 translaminar screw fixation in pediatric occipitocervical fusion

PurposeRigid occipitocervical (O-C) instrumentation can reduce the anterior pathology and has a high fusion rate in children with craniovertebral instability. Typically, axis (C2) screw fixation utilizes C1–C2 transarticular screws or C2 pars screws. However, anatomic variation may preclude these screw types due to the size of fixation elements or by placing the vertebral artery at risk for injury. Pediatric C2 translaminar screw fixation has low risk of vertebral artery injury and may be used when the anatomy is otherwise unsuitable for C1–C2 transarticular screws or C2 pars screws.MethodsWe retrospectively reviewed a neurosurgical database at UCSF Benioff Children’s Hospital Oakland for patients who had undergone a cervical spinal fusion that utilized translaminar screws for occipitocervical instrumentation between 2002 and 2020. We then reviewed the operative records to determine the parameters of C2 screw fixations performed. Demographic and all other relevant clinical data were then recorded.ResultsTwenty-five patients ranging from 2 to 18 years of age underwent O-C fusion, with a total of 43 translaminar screws at C2 placed. Twenty-three patients were fused (92%) after initial surgery with a mean follow-up of 43 months. Two patients, both with Down syndrome, had a nonunion. Another 2 patients had a superficial wound dehiscence that required wound revision. One patient died of unknown cause 7 months after surgery. One patient developed an adjacent-level kyphosis.ConclusionWhen performing occipitocervical instrumentation in the pediatric population, C2 translaminar screw fixation is an effective option to other methods of C2 screw fixation dependent on anatomic feasibility.

Morphometric Analysis of V2 Segment of Vertebral Artery in Patients with Symptomatic Neck Pain in South Indian Population – A CT Angiography Based Study

Objectives: The morphometric changes in the vertebral artery are essential for various interventions. Inadequate details about it can lead to risk of vertebral artery injury and other complications. This study explains the normal anatomical course of V2 segment of vertebral artery which is more prone for iatrogenic injury.&#x0D; Materials and Method: 25 adult patients with symptomatic neck pain were involved in the study. Various measurements were made from seventh cervical vertebra (C7) to the third cervical vertebra (C3) that included Distance from midline to VA, Distance from medial margin of Longus Colli to VA, Perpendicular distance from anterior margin of transverse process to center of VA, Horizontal distance from anterior tubercle to VA, sagittal and coronal diameter of the transverse foramen and vertebral artery.&#x0D; Result: Distance from midline, Distance from medial margin of Longus Colli, Perpendicular distance from anterior margin of transverse process to center of VA and Horizontal distance from anterior tubercle were increased towards right compared to left side. The sagittal and coronal diameter of the transverse foramen and vertebral artery decreased from C6 to C3 vertebra. Vertebral artery dominance was seen on left side in all cases.&#x0D; Conclusion: Preoperative assessment by computed tomography angiography helps to know the course of the vertebral artery, understand its patterns and assess various abnormalities thereby aids in preventing complications in future surgeries.

Determining C2 Pedicle Screw Placement Feasibility in the Pediatric Population: A Computed Tomographic Safe Zone Analysis.

Due to high rates of anatomic variability of the C2 pedicle, thin-sliced pedicular-oriented computed tomography (CT) and 3-dimensional reconstructive CT technologies have been introduced to predict safe C2 pedicle screw placement. However, this technology may not be readily available in all centers. The purpose of this study was to perform a C2 pedicle safe zone analysis using standard sagittal CT scans to predict the feasibility of C2 pedicle screw placement in a pediatric population and to compare the results with our previously obtained safe zone analysis from the adult population. A retrospective analysis was performed at a single level I trauma center of pediatric patients who completed CT scans of the cervical spine. The feasibility of C2 pedicle screw placement was analyzed using our previously described C2 pedicle safe zone analysis technique. The risk profiles were compared with our previously obtained safe zone analysis from the adult population. Thirty-nine consecutive patients with a mean age of 7.8±4.4 years and 78 total pedicles were included in the study. Fourteen pedicles (18%) were considered low risk, 37 (47%) were moderate risk, and 27 (35%) were high risk for vertebral artery injury. Individual patients were found to have a significant amount of side-to-side variability between pedicles with 21 patients (54%) having left and right pedicles with different risk profiles. Four patients (10%) demonstrated low risk profiles in bilateral pedicles. There was no significant difference between the risk profiles of pediatric and adult patients. There is a considerable amount of anatomic variability within the pediatric C2 pedicles. Using this simple and accessible technique during the review of preoperative imaging, C2 pedicle screw placement may be considered in appropriately selected pediatric patients. Level III.

The Feasibility Study of C1 Posterior Arch Crossing Screw Fixation in Adult Thai Population: A Computed Tomographic Morphometric Analysis Study

Objective: Atlantoaxial instability can be caused by various etiologies and surgical fixation is often required. Various methods have been described for atlantoaxial fixation. Screw fixation is associated with an increased risk of vertebral artery injury especially in patients with an anomalous vertebral artery location or abnormal bony anomalies. A new C1 posterior arch crossing screw fixation technique was proposed to reduce the risk of vertebral artery injury. The present study aimed to assess morphometric CT analysis of atlas for C1 posterior arch crossing screw fixation in Thai people. Materials and Methods: The present research was an observational study that reviewed 150 computed tomography (CT) scans of the patients who had neck trauma or any other complaint requiring craniocervical investigations. Atlantoaxial articulation deformities due to trauma, infections, neoplasm, congenital anomaly, inflammatory disease, incomplete CT scan analysis, and history of surgical intervention of the cervical spine were excluded. All the images were measured for the height of the posterior tubercle, the width of the posterior arch was measured bilaterally in three parts on the axial plane, part 1: medial of the VA groove, where the arch transforms into the VA groove, part 2: the middle part between the posterior tubercle and medial of the VA, and part 3: posterior tubercle, length of the screw, and the screw projection angle was calculated. Results: Out of the 139 CT scans analyzed, the mean measurement of posterior arch height was 7.45±1.03 mm, wherein 73.3% exceed 7 mm. The mean width of the left posterior arch in part 1, 2, and 3 was 4.50±0.70 mm, 4.90±0.70 mm, and 5.70±0.80 mm, respectively, and the width of the right posterior arch in part 1, 2, and 3 was 4.50±0.70 mm, 4.80±0.70 mm, and 5.60±0.80 mm, respectively. The mean crossing screw length of the Left and Right was 17.02±3.04 mm and 17.37±2.75 mm, respectively. The mean angle of screw of the Left and Right was 24.62±3.38 degrees and 24.78±3.57 degrees, respectively. There were no significant differences in these variables between gender or sides (p&gt;0.05) except the mean angle of the screw between gender (p&lt;0.05). Conclusion: C1 posterior arch screw fixation is feasible in the adult Thai population. Preoperative thin-cut CT is essential for planning successful posterior arch crossing screws placement. Keywords: C1 posterior arch, Computed tomography, Crossing screw fixation

“Crossed C1 Lateral Mass–C2 Subfacetal Screw and Rod Construct” for Atlantoaxial Fixation in Patients with High-Riding Vertebral Artery: A Technical Note

Background: Goel–Laheri's posterior C1/C2 fixation technique is the gold standard procedure for atlantoaxial dislocation (AAD) and basilar invagination. Coexisitng vertebral artery anomalies such as high-riding vertebral arteries pose an increased risk of vertebral artery injury during instrumentation. Alternate technique for avoiding vertebral artery injury in such cases like translaminar screw fixation had been associated with a high chance for screw pull out, resulting in an unstable construct. This case report introduces a novel, cost-effective technique of atlantoaxial fixation with a “bilateral crossed C1 lateral mass-C2 subfacetal screw and rod construct” in patients with atlantoaxial subluxation with high-riding vertebral arteries.Case Presentation: A 63-year-old male presented with complaints of neck pain and difficulty in walking. On physical examination, he had features of high cervical myelopathy. Imaging revealed AAD with bilateral high-riding vertebral arteries. He was treated with “Crossed C1 lateral mass-C2 subfacetal screw and rod fixation” without evidence of vertebral artery injury or neurological deficits. Postoperatively, the patient showed significant improvement in pain and Nurick score.Conclusions: This technique has the uniqueness of providing a stable, rigid fixation of the atlantoaxial joint with screws inserted into the C2 body providing good bone purchase and at the same time avoid vertebral artery injury in high riding cases. The surgical technique is demonstrated in a detailed manner in this technical note.

Pipeline embolization for recurrent vertebral artery thromboembolic events secondary to a misplaced pedicle screw

Cervical spine instrumentation carries a risk of vertebral artery injury which can cause devastating neurological events. Flow diversion using the Pipeline embolization device (PED) is a commonly used endovascular modality that can treat various vessel wall abnormalities including aneurysms and arterial dissections. CASEDESCRIPTION: We report the case of a 69-year-old female who presented with multiple cryptogenic strokes secondary to a vertebral artery irregularity from a misplaced pedicle screw. She continued having ischemic infarcts despite maximal medical therapy. The patient was successfully treated with the PED and has not had any further ischemic events at 1-year follow-up. To our knowledge, this is the first published case of a chronic vertebral artery abnormality secondary to a misplaced pedicle screw that was treated with flow diversion. This is likely a safe and effective treatment for this rare complication of pedicle screw placement.

Cervical fixation in the elderly

Posterior fixation of the cervical spine is a common procedure performed for many conditions including trauma, degenerative conditions, deformities, infection, neoplasms, and congenital malformations. Unlike thoracolumbar spine fixation, cervical fixation should consider the risk of vertebral artery injury in addition to the stability of the fixation and spinal cord/nerve root injury. Although lateral mass screw fixation is the most common type of cervical fixation, other options including pedicle screws and translaminar screws could be utilized. Each technique comes with its own advantages and risk of complications to the neural structures, vertebral artery, and fixation failure. However, these risks can be elevated in the elderly population with 1) decreased bone density 2) degenerative changes to the spine and 3) tortuosity of vertebral artery.

Navigated transoral odontoidectomy to treat congenital basilar invagination after failed posterior reduction and fusion.

Transoral odontoidectomy is a traditional technique to treat congenital basilar invagination (BI) associated with atlantoaxial dislocation (AAD). Although posterior surgery has been a trend to treat most cases, there are still cases that need to be treated through a transoral approach. In addition, intraoperative modern image-guided navigation systems help identify any remnants of the dens and decrease the risk of vertebral artery injury. For symptomatic cases with a history of previous posterior fusion and severe osteoporosis, transoral odontoidectomy is preferred over a posterior-only approach. Our video demonstrates the surgical technique for transoral revision odontoidectomy to treat congenital basilar invagination associated with atlantoaxial dislocation after previous posterior craniovertebral junction surgery.The video can be found here: https://youtu.be/vzcAW8oLcZY

C2 medial pedicle screw: a novel "in-out-in" technique as an alternative option for posterior C2 fixation in cases with a narrow C2 isthmus.

The authors describe a novel "in-out-in" technique as an alternative option for posterior C2 screw fixation in cases that involve narrow C2 isthmus. Here, they report the preliminary radiological and clinical outcomes in 12 patients who had a minimum 12-month follow-up period. Twelve patients with basilar invagination and atlantoaxial dislocation underwent atlantoaxial reduction and fixation. All patients had unilateral hypoplasia of the C2 isthmus that prohibited insertion of pedicle screws. A new method, the C2 medial pedicle screw (C2MPS) fixation, was used as an alternative. In this technique, the inner cortex of the narrow C2 isthmus was drilled to obtain space for screw insertion, such that the lateral cortex could be well preserved and the risk of vertebral artery injury could be largely reduced. The C2MPS traveled along the drilled inner cortex into the anterior vertebral body, achieving a 3-column fixation of the axis with multicortical purchase. Satisfactory C2MPS placement and reduction were achieved in all 12 patients. No instance of C2MPS related vertebral artery injury or dural laceration was observed. There were no cases of implant failure, and solid fusion was demonstrated in all patients. This novel in-out-in technique can provide 3-column rigid fixation of the axis with multicortical purchase. Excellent clinical outcomes with low complication rates were achieved with this technique. When placement of a C2 pedicle screw is not possible due to anatomical constraints, the C2MPS can be considered as an efficient alternative.

C1-C2 posterior screw fixation in atlantoaxial fractures revisited: technical update based on 127 cases.

Posterior fusion of traumatic odontoid fractures by C1 lateral mass and C2 isthmic screws (modified Harms-Goel technique) is a viable alternative to transarticular screw fixation due to its universal applicability. This retrospective study reports on a series of 127 patients. Our clinical database was screened for patients with fractures of the upper cervical spine incorporating a C2 fracture, operated on between 2007 and 2015. Patients were included if fused by internal fixation via C1 lateral mass screws, C2 isthmic screws in freehand technique under lateral fluoroscopy. Screw placement was controlled postoperatively by computed tomography and rated using the Gertzbein & Robbins classification. Surgery-related complications, consecutive treatment, revision surgeries and duration of surgeries were registered. In total, 127 patients were identified with altogether 572 screws. Correct screw positions of grade A and B according to Gertzbein & Robbins were achieved in a total of 539 (94.2%) screws (grade A: 453 (79.2%); grade B: 86 (15%)), grade C screw malpositions noted in 21 (3.7%), grade D in 10 (1.7%) and grade E in 2 (0.3%) screws. Vertebral artery canal breaches occurred in 29 screws (5.1%), with vertebral artery occlusion in 4 patients. Coiling of injured vertebral artery had to be performed in one patient. None of these patients suffered clinically apparent cerebrovascular complications. Revision surgery was performed in 8 patients (6%). Posterior fixation of atlantoaxial fractures by C1 lateral mass and C2 isthmic screws with fluoroscopy without navigation is a safe and feasible method but not free of risk of vertebral artery injuries. These slides can be retrieved under Electronic Supplementary Material.

The case for T2 pedicle subtraction osteotomy in the surgical treatment of rigid cervicothoracic deformity.

Rigid cervicothoracic kyphotic deformity (CTKD) remains a difficult pathology to treat, especially in the setting of prior cervical instrumentation and fusion. CTKD may result in chronic neck pain, difficulty maintaining horizontal gaze, and myelopathy. Prior studies have advocated for the use of C7 or T1 pedicle subtraction osteotomies (PSOs). However, these surgeries are fraught with danger and, most significantly, place the C7, C8, and/or T1 nerve roots at risk. The authors retrospectively reviewed their experience with performing T2 PSO for the correction of rigid CTKD. Demographics collected included age, sex, details of prior cervical surgery, and coexisting conditions. Perioperative variables included levels decompressed, levels instrumented, estimated blood loss, length of surgery, length of stay, complications from surgery, and length of follow-up. Radiographic measurements included C2-7 sagittal vertical axis (SVA) correction, and changes in the cervicothoracic Cobb angle, lumbar lordosis, and C2-S1 SVA. Four male patients were identified (age range 55-72 years). Three patients had undergone prior posterior cervical laminectomy and instrumented fusion and developed postsurgical kyphosis. All patients underwent T2 PSO: 2 patients received instrumentation at C2-T4, and 2 patients received instrumentation at C2-T5. The median C2-7 SVA correction was 3.85 cm (range 2.9-5.3 cm). The sagittal Cobb angle correction ranged from 27.8° to 37.6°. Notably, there were no neurological complications. T2 PSO is a powerful correction technique for the treatment of rigid CTKD. Compared with C7 or T1 PSO, there is decreased risk of injury to intrinsic hand muscle innervators, and there is virtually no risk of vertebral artery injury. Laminectomy may also be safer, as there is less (or no) scar tissue from prior surgeries. Correction at this distal level may allow for a greater sagittal correction. The authors are optimistic that these findings will be corroborated in larger cohorts examining this challenging clinical entity.

Risk of Vertebral Artery Injury and Stroke Following Blunt and Penetrating Cervical Spine Trauma: A Retrospective Review of 729 Patients

Cervical spine trauma (CST) may result in vertebral artery injury (VAI), increasing the risk of developing stroke. Stroke risk following CST is poorly reported. In total, 729 patients with CST were retrospectively analyzed, including rates of VAI, age at injury, cause of injury, cardiovascular history, smoking history, substance abuse history, embolization therapy, and antiplatelet or anticoagulant therapy prior or after injury. VAIs were identified and graded following the Modified Denver Criteria for Blunt Cerebrovascular Injury using magnetic resonance angiography and computed tomography angiography. Brain scans were reviewed for stroke rates and statistically significant variations. Thirty-three patients suffered penetrating trauma, whereas 696 patients experienced blunt trauma. In total, 81 patients met the criteria for analysis with confirmed VAI. VAI was more common in penetrating injury group compared with blunt injury group (64% vs. 9%, P < 0.0005). However, low-grade VAI (less than grade III) was more common in blunt injury group versus penetrating group (37% vs. 14%, P < 0.05). The frequency of posterior circulation strokes did not vary significantly between groups (26.3% vs. 13.8%, P= 0.21). Cardiovascular comorbidities were significantly more common in the blunt group (50%, P= 0.0001) compared with the penetrating group (0%). VAI occurs with a high incidence in penetrating CST. Although stroke risk following penetrating and blunt CST did not vary significantly, they resulted in serious complications in a group of patients. Further study of this patient population is required to provide high-level, evidence-based preventions for VAI complications.

Direct Aortic Origin of the Left Vertebral Artery in Two Adult Female Cadavers

BackgroundThe vertebral artery (VA) is a branch of the aortic arch which usually arises from the posterosuperior aspect of the first part of the subclavian artery and ascends medially to the transverse process of the seventh cervical vertebra and continues ascending through the transverse foramina of the upper six cervical vertebrae to enter the skull via the foramen magnum. It is an important blood supply of the spinal cord, vertebral muscles, hindbrain and contribution to the circle of Willis.ResultsDuring routine dissection of the superior mediastinum and neck of two adult female cadavers the left VA was observed originating directly from the aortic arch rather than the left subclavian artery. In one cadaver the left VA entered the transverse foramen of the fifth cervical vertebra (CV5), while in the other cadaver it entered the typical the sixth cervical vertebra (CV6) transverse foramen. The diameter and length of the vessel that entered CV5 maintained the same diameter of 5mm from its origin to its position on the posterior arch of the atlas and measured 95mm in length from its origin to its entrance at CV5. In the other cadaver, the diameter decreased from 4mm, at its origin, to 3mm as it entered CV6. As it ascended from its origin it took a highly coiled approach and measured 60mm in length from its origin to it entrance in CV6. Direct aortic origin of the left vertebral artery is the most frequent anatomic variant of the vertebral artery with an incidence ranging from 2.4–5.8%.ConclusionKnowledge of this variation is important to reduce the risk of vertebral artery injury in angiography and surgical approaches.Support or Funding InformationCenter for Anatomical Science and Education, Department of Surgery, Saint Louis University School of MedicineThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Radiographic and clinical outcomes of C1-C2 intra-articular screw fixation in patients with atlantoaxial subluxation

BackgroundThe Magerl and Goel-Harms techniques have been reported to produce excellent treatment outcomes in cases of atlantoaxial subluxation, but they also carry a risk of vertebral artery injuries. In order to completely prevent such injuries, we developed a surgical procedure, involving bone grafting between the C1 posterior arch and C2 lamina with clamp- or hook-and-rod-based fixation combined with the insertion of an interference screw into the posterior atlantoaxial joint.MethodsThis was a retrospective single-center study. The subjects were 58 patients in whom atlantoaxial subluxation was treated with the abovementioned procedure after 1995 (33 patients with rheumatoid arthritis (RA group) and 25 patients without rheumatoid arthritis (non-RA group)). The clinical outcomes and imaging findings of anterior subluxation at ≥ 2 years after surgery were compared between the RA and non-RA groups.ResultsNo vertebral artery injuries occurred during surgery. Seven and two patients died during the follow-up period in the RA and non-RA groups, respectively, but none of these deaths were associated with surgery. At ≥ 2 years after surgery, the visual analogue scale score, Japanese Orthopaedic Association score, and Ranawat classification had significantly improved in both groups (p < 0.001). Radiologically, bone fusion was noted in all patients. Significant changes in the atlas-dens interval (ADI) were seen immediately after surgery in both groups (p < 0.001). In the non-RA group, significant changes in the corrected atlantoaxial height were observed immediately after surgery (p < 0.01), and loss of correction was seen at the final follow-up, but it was not significant (p = 0.1965). No significant changes were noted in any other parameter. Regarding the postoperative alignment of the cervical spine, lordosis tended to decrease, but additional surgery was only performed in one patient, who had developmental stenosis at the mid-lower level and belonged to the RA group. No reoperations due to fused adjacent segmental disease or exacerbated curvature were required.ConclusionIn the present study, no vertebral artery injuries occurred during surgery, and no major perioperative complications developed. Favorable clinical outcomes were observed at ≥ 2 postoperative years although the patients’ diseases varied. This procedure produced superior outcomes, especially in terms of spinal correction and the maintenance of the ADI.

Biomechanical and Anatomical Validity of the Short Posterior Arch Screw.

ObjectiveThis study was conducted to clarify the validity of the short posterior arch screw (S-PAS). The S-PAS is inserted only in the pedicle-analogue portion of the posterior arch. The S-PAS screw length is almost half that conventional C1 lateral mass screws inserted via the posterior arch (via-PAS). S-PAS reduces the risk of vertebral artery injury (VAI) because it never reaches the transverse foramen. Although the biomechanical validity of various C1 lateral mass screws (C1LMS) analyzed in young specimens have been published, that of unicortically inserted C1LMS such as the unicortical Harms screw, S-PAS, and via-PAS for elderly patients is concerning because of the high prevalence of osteoporosis in the elderly. MethodsNine fresh frozen cadavers (average age at death, 72.1 years) were used for pullout testing. The bone mineral density of each specimen was evaluated using quantitative computed tomography. ResultsThe pullout strength of via-PAS (1,048.5 N) was significantly greater than that of the unicortical Harms screw (257.9 N) (p<0.05). The pullout strength of S-PAS was 720.3 N, which was also significantly greater than that of the unicortical Harms screw (p<0.05). ConclusionThe via-PAS and S-PAS are valid surgical options, even in elderly patients. Along with sufficient biomechanical strength, the S-PAS screw prevents VAI.

Morphometric Evaluation of Occipital Condyles: Defining Optimal Trajectories and Safe Screw Lengths for Occipital Condyle-Based Occipitocervical Fixation in Indian Population.

Study DesignComputed tomographic (CT) morphometric analysis.PurposeTo assess the feasibility and safety of occipital condyle (OC)-based occipitocervical fixation (OCF) in Indians and to define anatomical zones and screw lengths for safe screw placement.Overview of LiteratureLimitations of occipital squama-based OCF has led to development of two novel OC-based OCF techniques.MethodsMorphometric analysis was performed on the OCs of 70 Indian adults. The feasibility of placing a 3.5-mm-diameter screw into OCs was investigated. Safe trajectories and screw lengths for OC screws and C0–C1 transarticular screws without hypoglossal canal or atlantooccipital joint compromise were estimated.ResultsThe average screw length and safe sagittal and medial angulations for OC screws were 19.9±2.3 mm, ≤6.4°±2.4° cranially, and 31.1°±3° medially, respectively. An OC screw could not be accommodated by 27% of the population. The safe sagittal angles and screw lengths for C0–C1 transarticular screw insertion (48.9°±5.7° cranial, 26.7±2.9 mm for junctional entry technique; 36.7°±4.6° cranial, 31.6±2.7 mm for caudal C1 arch entry technique, respectively) were significantly different than those in other populations. The risk of vertebral artery injury was high for the caudal C1 arch entry technique. Screw placement was uncertain in 48% of Indians due to the presence of aberrant anatomy.ConclusionsThere were significant differences in the metrics of OC-based OCF between Indian and other populations. Because of the smaller occipital squama dimensions in Indians, OC-based OCF techniques may have a higher application rate and could be a viable alternative/salvage option in selected cases. Preoperative CT, including three-dimensional-CT-angiography (to delineate vertebral artery course), is imperative to avoid complications resulting from aberrant bony and vascular anatomy. Our data can serve as a valuable reference guide in placing these screws safely under fluoroscopic guidance.