Accuracy of Palpation Procedures for Locating the C1 Transverse Process and Masseter Muscle as Confirmed by Computed Tomography Images.

OBJECTIVE: The purpose of this study was to examine the accuracy of palpation methods for locating the transverse processes of the first cervical vertebra and masseter muscle using radiographic images as the gold-standard method and the association between personal characteristics with the observed accuracy. METHODS: This was a single-blinded, diagnostic accuracy study. Ninety-five participants (49 women, 58 ± 16 years of age) were enrolled in this study. A single examiner palpated the neck and face region of all participants to identify the transverse processes of the first cervical vertebra and masseter muscles bilaterally. In sequence, participants underwent a multislice computed tomography scan for assessment of the superimposed inner body structure. Two radiologists assessed the computed tomography images using the same criteria and were blinded regarding each other's assessment and the anatomic landmarks under investigation. The palpation accuracy was calculated as the proportion of the correctly identified landmarks in the studied sample. The correlation of the palpation outcome (correct = 1; incorrect = 0) with age, sex (male = 1; female = 0), and body mass index was investigated using the point-biserial correlation coefficient. RESULTS: The right and left transverse processes were correctly located in 76 (80%) and 81 (85%) participants, respectively, and bilaterally in 157 events (83%), as evaluated by the consensus of the 2 radiologists. The masseter muscles were correctly localized bilaterally in 95 of 95 (100%) participants. Body mass showed statistical evidence of a weak, positive correlation with the correct location of the transverse processes of the first cervical vertebra at the right body side (r = .219; 95% confidence interval, 0.018-0.403; P = .033). CONCLUSION: Palpation methods used in this study accurately identified the location of the first cervical vertebra spinous processes and the masseter muscles.

Clinical impact of 3-level anterior cervical decompression and fusion (ACDF) on the occipito-atlantoaxial complex: a retrospective study of patients who received a zero-profile anchored spacer versus cage-plate construct.

PURPOSE: To evaluate changes in the sagittal parameters of the occipito-atlantoaxial complex after three-level anterior cervical decompression and fusion (ACDF) and identify the influential factors by comparing ACDF with a zero-profile anchored spacer (ACDF-Z) versus a cage-plate construct (ACDF-P). METHODS: The cohort comprised 106 patients who underwent three-level contiguous ACDF-Z or ACDF-P for cervical radiculopathy and/or myelopathy. Standing, flexion, and extension radiographs of cervical spine were obtained preoperatively, and 3 and 12 months postoperatively. The assessed cervical sagittal parameters were the platform angle of the axis, Cobb angle, and range of motion (ROM) of C2⁃7, C0⁃1, and C1⁃2. RESULTS: In both the ACDF-Z and ACDF-P groups, the Cobb angle of the upper cervical spine decreased and the C0-1 ROM increased from preoperatively to 3 and 12 months postoperatively (P < 0.01). The alignment restoration was lost at 12 months compared with 3 months in the ACDF-Z group, but not in the ACDF-P group (P < 0.01). The ACDF-P group showed more loss of C2-7 ROM and more compensatory changes in C0-2 ROM than the ACDF-Z group (P < 0.05). CONCLUSION: The Cobb angle decreased and ROM increased significantly as compensatory changes of the atlantooccipital or atlantoaxial joint after both types of ACDF, which may accelerate degeneration. The zero-profile anchored spacer had less impact on the occipito-atlantoaxial complex but was worse at maintaining the alignment restoration, which were contrary to the cage-plate construct. Surgeons should be aware of the impact of multi-level ACDFs on the occipito-atlantoaxial complex.

[Minimally invasive treatment of cervical1-2 epidural neurilemmoma].

OBJECTIVE: To explore the minimally invasive surgical method for cervical1-2 epidural neurilemmoma. METHODS: The clinical features, imaging characteristics and surgical methods of 63 cases of cervical1-2 epidural neurilemmoma from July 2010 to December 2018 were reviewed and analyzed. Pain and numbness in occipitocervical region were the common clinical symptoms. There were 58 cases with pain, 30 cases with numbness, 3 cases with limb weakness and 2 cases with asymptomatic mass. Magnetic resonance imaging (MRI) showed that the tumors located in the cervical1-2 epidural space with diameter of 1-3 cm. The equal or slightly lower T1 and equal or slightly higher T2 signals were found on MRI. The tumors had obvious enhancement. Individualized laminotomy was performed according to the location and size of the tumors, and axis spinous processes were preserved as far as possible. Resection of tumor was performed strictly within the capsule. RESULTS: Total and subtotal resection of tumor were achieved in 60 and 3 cases respectively, and no vertebral artery injury was found. The operation time ranged from 60 to 180 minutes, with an average of 92.83 minutes. The hospitalization time ranged from 3 to 9 days, with an average of 5.97 days. All tumors were confirmed as neurilemmoma by pathology. There was no postoperative infection or cerebrospinal fluid leakage. There was no new-onset dysfunction except 9 cases of numbness in the nerve innervation area. The period of follow-up ranged from 6 months to 8 years (median: 3 years). All the new-onset dysfunction recovered completely. Pain disappeared in all of the 58 patients with pain. Numbness recovered completely in 27 patients while slight numbness remained in another 3 patients. Three patients with muscle weakness recovered completely. The spinal function of all the patients restored to McCormick grade Ⅰ. No recurrence was found on MRI. No cervical spine instability or deformity was found on X-rays. CONCLUSION: It is feasible to resect cervical1-2 epidural neurilemmoma by full use of the anatomical space between atlas and axis and individual laminotomy. It is helpful to prevent cervical instability or deformity by minimizing the destruction of cervical2 bone and preserving normal muscle attachment to cervical2 spinous process. Strict intracapsular resection can effectively prevent vertebral artery injury.

The feasibility of inserting a C1 pedicle screw in patients with ponticulus posticus: a retrospective analysis of eleven patients.

BACKGROUND: Ponticulus posticus is a common anatomic variation that can be mistaken for a broad posterior arch during C1 pedicle screw placement. When the atlas lateral mass screws are placed via the posterior arch, injury to the vertebral artery may result. To our knowledge, there are few clinical studies that have analyzed the feasibility of C1 pedicle screw fixation in patients with ponticulus posticus, in clinical practice. PURPOSE: To evaluate the feasibility of inserting a C1 pedicle screw in patients with ponticulus posticus. METHODS: Between January 2008 and January 2012, 11 consecutive patients with atlantoaxial instability, and with a ponticulus posticus at C1, underwent posterior fusion surgery in our institution. According to preoperative computed tomography (CT) reconstruction, a complete ponticulus posticus was found unilaterally in nine patients and bilaterally in two. Postoperative CT reconstructive imaging was performed to assess whether C1 pedicle screw placement was successful. Patients were followed up at regular intervals and evaluated for symptoms of ponticulus posticus syndrome. RESULTS: Thirteen C1 pedicles (atlas vertebral artery groove), each with a complete ponticulus posticus, were successfully inserted with thirteen 3.5- or 4.0-mm diameter pedicle screws, without resection of the bony anomaly. No intraoperative complications (venous plexus, vertebral artery, or spinal cord injury) occurred. The mean follow-up period was 21 (range 14-30) months. Postoperative CT reconstructive images showed that all 13 pedicle screws were inserted in the C1 pedicles without destruction of the atlas pedicle cortical bone. In the follow-up period, none of the patients demonstrated clinical symptoms of ponticulus posticus syndrome or developed bone fusion. CONCLUSION: Three-dimensional CT imaging should be considered prior to C1 pedicle screw fixation in patients with ponticulus posticus, to avoid mistaking the ponticulus posticus for a widened dorsal arch of the atlas. If there is no ponticulus posticus syndrome preoperatively, C1 pedicle screw fixation can be successfully performed without removing the bony anomaly.

Anatomical anomalies of the V3 segment of the vertebral artery in the Polish population.

PURPOSE: The aim of this study is to evaluate the incidence of the anatomical anomalies of the V3 segment of the vertebral artery in the Polish population. There is conflicting evidence on the incidence of these anomalies: Asian-based studies show high incidence of 10 %, whereas the North American study identifies these anomalies in less than 1 % of patients. METHODS: 1800 computed tomography angiographies (CTA) obtained at the Barlicki University Hospital in Lodz, Poland, were reviewed retrospectively. RESULTS: All the patients were Caucasians. There were 968 males and 832 females. The mean age of the patients was 58. CTAs were obtained for the following reasons: stroke 1312, trauma 25, vascular/aneurysm 216, and intracranial haemorrhage 247. Vertebral artery hypoplasia was present in 360 cases (20 %). Persistent intersegmental artery (type I anomaly) was not found in any study. Fenestration of the V3 vertebral artery (type II) was recognized in three angiograms (0.16 %). Vertebral artery ending up as posterior inferior cerebellar artery (type III anomaly) was seen in 11 patients (0.61 %). CONCLUSIONS: Very low incidence of V3 segment anomalies does not justify in our opinion routine vascular imaging in patients undergoing posterior cervical instrumented procedures.

Atlantooccipital assimilation associated with combined atlas arch defect: a radiological case report.

In this report, atlantooccipital assimilation (AS), anterior arch defect (AAD), and posterior arch defect (PAD) of the atlas, and several variations around the craniocervical junction were identified on computed tomography (CT) of a patient of unknown sex and age. Coronal and sagittal CT scans showed AS and bilateral fusion of the atlas and the base of occipital bone. Axial CT scan at the atlas revealed PAD type B on the left side and midline AAD. Morphometric measurements indicated a potential ventral spinal cord compression. In addition, mid-sagittal CT revealed the presence of fossa navicularis magna and incomplete formation of the transverse foramen on the right side. This study reports an extremely rare AS associated with AAD, PAD, and other variations of the clivus and the atlas. To our knowledge, no similar case has been reported in the literature.

Combined replantation of the posterior arch of the atlas and bilateral axial lamina in the treatment of intradural schwannoma: a case report.

Background: Laminotomy and laminar replantation have emerged as novel treatment modalities for intraspinal tumors, aiming to minimize postoperative complications and retain spinal mobility. However, existing research predominantly emphasizes their application in the thoracolumbar spine. The unique anatomy of the atlantoaxial segments necessitates surgical techniques that differ from those used in other spinal regions, and the clinical effect of such procedure remains unknown. Case presentation: A 61-year-old male patient with intradural schwannoma at the atlantoaxial level was operated on. The patient underwent posterior laminectomy, as well as a combined replantation of the posterior arch of the atlas and bilateral axial laminae. Postoperatively, the patient experienced significant neurological improvement, with no deformities or instability on the radiological assessments during the follow-up. Conclusion: Laminotomy with combined replantation of the posterior arch of the atlas and bilateral axial lamina emerges as an effective approach for managing intraspinal tumors at the atlantoaxial level. This technique not only offers ample operating space but also restores the stability of the spinal canal. Moreover, it preserves the mobility of the atlantoaxial segment, minimizes impact on adjacent segments, and mitigates the formation of postoperative fibrosis.

Two-level Anterior Cervical Corpectomy and Fusion versus Posterior Open-door Laminoplasty for the Treatment of Cervical Ossification of Posterior Longitudinal Ligament: A Comparison of the Clinical Impact on the Occipito-Atlantoaxial Complex.

OBJECTIVE: Both two-level anterior cervical corpectomy and fusion (t-ACCF) and posterior open-door laminoplasty (ODLP) are effective surgical procedures for the treatment of ossification of the posterior longitudinal ligament (OPLL). Previous studies have identified different effects of different surgical procedures on the upper and subaxial cervical spine (UCS, SCS), however, there are no studies on the effects of t-ACCF and ODLP on the occipito-atlantoaxial complex. Therefore, the purpose of this study is to compare the changes in sagittal parameters and range of motion (ROM) of the occipito-atlantoaxial complex in OPLL patients treated with t-ACCF and ODLP. METHODS: This was a retrospective study that included 74 patients who underwent t-ACCF or ODLP for the treatment of OPLL from January 2012 to August 2022 at our institution. Preoperative, 3-month, and 1-year postoperative cervical neutral, flexion-extension, and lateral flexion radiographs were taken. Sagittal parameters including Cobb angle of C2-7, C0-2, C0-1, C1-2, C2 slope, and the ROM were measured. The clinical outcome was assessed using the JOA, VAS, and NDI scores preoperatively and at 3 and 12 months postoperatively. Multiple linear regression was employed to identify factors influencing changes in UCS. RESULTS: In the ODLP group, the SCS (C2-7) Cobb angle was significantly reduced (12.85 ± 10.0 to 7.68 ± 11.27; p < 0.05), and the UCS (C0-2) Cobb angle was significantly compensated for at 1 year postoperatively compared with the t-ACCF group (3.05 ± 4.09 vs 0.79 ± 2.62; p < 0.01). The SCS and lateral flexion ROM of the ODLP group was better maintained than t-ACCF (14.51 ± 6.00 vs 10.72 ± 3.79; 6.87 ± 4.56 vs 3.81 ± 1.67; p < 0.01). The compensatory increase in C0-2, C0-1, and C1-2 ROM was pronounced in both groups, especially in the ODLP group. The results of multiple linear regression showed that only the surgical procedure was a significant factor influencing UCS. CONCLUSION: The loss of the SCS Cobb angle was more pronounced in ODLP relative to t-ACCF, resulting in a significant compensatory increase in UCS and atlantoaxial Cobb angle. The ROM of the UCS, atlantooccipital, and atlantoaxial joints was significantly increased in both groups, this may accelerate degenerative changes in the occipital-atlantoaxial complex, may leading to poorer outcomes in the long-term; of these, ODLP should receive more attention. In contrast, t-ACCF better maintains normal curvature of the SCS and occipito-atlantoaxial complex but loses more ROM.

Radiological Study of Atlas Arch Defects with Meta-Analysis and a Proposed New Classification.

This study consists of a retrospective cohort study, a systematic review, and a meta-analysis which were separately conducted. This study aimed to investigate the prevalence of atlas arch defects, generate an evidence-based synthesis, and propose a common classification system for the anterior and combined atlas arch defects. Atlas arch defects are well-corticated gaps in the anterior or posterior arch of the atlas. When both arches are involved, it is known as a combined arch defect. Awareness of these defects is essential for avoiding complications during surgical procedures on the upper spine. The prevalence of arch defects was investigated in an open-access OPC-Radiomics (Radiomic Biomarkers in Oropharyngeal Carcinoma) dataset comprising 606 head and neck computed tomography scans from oropharyngeal cancer patients. A systematic review and meta-analysis were performed to generate prevalence estimates of atlas arch defects and propose a classification system for the anterior and combined atlas arch defects. The posterior arch defect was found in 20 patients (3.3%) out of the 606 patients investigated. The anterior arch defect was not observed in any patient, while a combined arch defect was observed in one patient (0.2%). A meta-analysis of 13,539 participants from 14 studies, including the present study, yielded a pooled-posterior arch defect prevalence of 2.07% (95% confidence interval [CI], 1.22%-2.92%). The prevalences of anterior and combined arch defects were 0.00% (95% CI, 0.00%-0.10%) and 0.14% (95% CI, 0.04%-0.25%), respectively. The anterior and combined arch defects were classified into five subtypes based on their morphology and frequency. The present study showed that atlas arch defects were present in approximately 2% of the general population. For future studies, larger sample sizes should be used for studying arch defects to avoid the small-study effect and to predict the prevalence accurately.

[Posterior cervical pedicle screw rod short-segment internal fixation for the treatment of atlantoaxial fracture and dislocation].

OBJECTIVE: To investigate the clinical efficacy of posterior cervical pedicle screw short-segment internal fixation for the treatment of atlantoaxial fracture and dislocation. METHODS: The clinical data of 60 patients with atlantoaxial vertebral fracture and dislocation underwent surgery between January 2015 and January 2018 were retrospectively analyzed. The patients were divided into study group and control group according to different surgical methods. There were 30 patients in study group, including 13 males and 17 females, with an average age of (39.32±2.85) years old, were underwent short-segment internal fixation with posterior cervical pedicle screws. There were 30 patients in control group, including 12 males and 18 females, with an average age of (39.57±2.90) years old, were underwent posterior lamina clip internal fixation of the atlas. The operation time, intraoperative blood loss, postoperative ambulation time, hospitalization time and complications between two groups were recorded and compared. The pain visual analogue scale(VAS), Japanese Orthopedic Association(JOA) score of neurological function, and fusion status were evaluated between two groups. RESULTS: All patients were followed up for at least 12 months. The study group was better than control group in operation time, intraoperative blood loss, postoperative off-bed activity time, and hospital stay (P=0.000). One case of respiratory tract injury occurred in study group. In control group, 2 cases occurred incision infection, 3 cases occurred respiratory tract injury, and 3 cases occurred adjacent segmental joint degeneration. The incidence of complications in study group was lower than that in control group (χ2=4.705, P=0.030). At 1, 3, 7 days after operation, VAS of study group was lower than that of control group(P=0.000). At 1, 3 months after operation, JOA score of study group was higher than that of control group(P=0.000). At 12 months after operation, all the patients in the study group achieved bony fusion. In control group, there were 3 cases of poor bony fusion and 3 cases of internal fixation fracture, the incidence rate was 20.00%(6/30). The difference between two groups was statistically significant (χ2=4.629, P=0.031). CONCLUSION: Posterior cervical short-segment pedicle screw fixation for atlantoaxial fracture and dislocation has the advantages of less trauma, shorter operation time, fewer complications, and less pain, and can promote the recovery of nerve function as soon as possible.

C2 Superior Facetal Osteotomy: A Novel Technique in Complex Craniovertebral Junction Surgery for C1 Lateral Mass Screw Placement.

Complex craniovertebral junction (CVJ) defects account for a considerable proportion of CVJ diseases. Given the heavily assimilated C1, an unfavorable C1-C2 joint orientation, an overriding C2 superior facet, a low-hanging occiput, and an abnormal vertebral artery course with a high-riding vertebral artery, placement of C1 lateral mass screws might be difficult. To address this, a novel technique for placing C1 lateral mass screws that avoid vertebral artery injury, low-hanging occiput, and overriding C2 superior facet was developed in this study. This approach enables firm fixation of C1-C2 even in difficult situations where the placement of the C1 lateral mass is challenging.

Direct Internal Fixation for Unstable Atlas Fractures.

PURPOSE: To investigate the radiologic and clinical outcomes of direct internal fixation for unstable atlas fractures. MATERIALS AND METHODS: This retrospective study included 12 patients with unstable atlas fractures surgically treated using C1 lateral mass screws, rods, and transverse connector constructs. Nine lateral mass fractures with transverse atlantal ligament (TAL) avulsion injury and three 4-part fractures with TAL injury (two avulsion injuries, one TAL substance tear) were treated. Radiologic outcomes included the anterior atlantodental interval (AADI) in flexion and extension cervical spine lateral radiographs at 6 months and 1 year after treatment. CT was also performed to visualize bony healing of the atlas at 6 months and 1 year. Visual Analog Scale (VAS) scores for neck pain, Neck Disability Index (NDI) values, and cervical range of motion (flexion, extension, and rotation) were recorded at 6 months after surgery. RESULTS: The mean postoperative extension and flexion AADIs were 3.79±1.56 (mean±SD) and 3.13±1.01 mm, respectively. Then mean AADI was 3.42±1.34 and 3.33±1.24 mm at 6 months and 1 year after surgery, respectively. At 1 year after surgery, 11 patients showed bony healing of the atlas on CT images. Only one patient underwent revision surgery 8 months after primary surgery due to nonunion and instability findings. The mean VAS score for neck pain was 0.92±0.99, and the mean NDI value was 8.08±5.70. CONCLUSION: C1 motion-preserving direct internal fixation technique results in good reduction and stabilization of unstable atlas fractures. This technique allows for the preservation of craniocervical and atlantoaxial motion.

[Research progress of causes and strategies in revision surgery for atlantoaxial dislocation].

Atlantoaxial dislocation (AAD) is a kind of life-threatening atlantoaxial structural instability and a series of neurological dysfunction caused by common multidisciplinary diseases. The operation risk is extremely high because it is adjacent to the medulla oblongata and the location is deep. With the increase of the number of operations in the upper cervical region, postoperative complications such as failure of internal fixation, non fusion of bone graft and poor prognosis gradually increase.Incomplete primary operation, non fusion of bone graft, infection and congenital malformation are the potential causes. In addition, considering the objective factors such as previous graft, scar formation and anatomical marks changes, revision surgery is further difficult. However, there is currently no standard or single effective revision surgery method. Simple anterior surgery is an ideal choice in theory, but it has high risk and high empirical requirements for the operator;simple posterior surgery has some defects, such as insufficient reduction and decompression;anterior decompression combined with posterior fixation fusion is a more reasonable surgical procedure, but many problems such as posterior structural integrity and multilevel fusion need to be considered.This article reviews the causes and strategies of AAD revision surgery.

[Application of posterior arch of the atlasrch resection for high-level cervical dumbbell schwannoma surgery].

OBJECTIVE: To investigate the feasibility and clinical effect of hemi-resection of posterior arch of atlas in the upper cervical spinal dumbbell-shaped schwannomas. METHODS: A retrospective analysis was performed on 13 patients with high level cervical dumbbell schwannomas from January 2005 to December 2018, including 10 males and 3 females, aged 19 to 67 years old. The occipital foramen to the C1 were 4 cases and 9 cases of C1,2. Tumors were removed by posterior arch of the atlas resection without internal fixation. The clinical efficacy was evaluated by visual analogue pain scale (VAS), Japanese Orthopaedic Association (JOA) scores, and American Spinal Injury Association(ASIA) ratings. RESULTS: The operation was successfully completed in 13 cases of this group. No vertebral artery injury or spinal cord injury occurred during the operation. All 13 patients were followed up for more than 12 months. No local recurrence was found. Both the VAS and the JOA score were significantly improved compared with those before surgery. The ASIA classification before operation was:1 case of grade C, 6 cases of grade D, 6 cases of grade E;the latest follow up was 3 cases of ASIA grade D and 10 cases of E. CONCLUSION: The posterior arch of the atlas hemisection can remove the upper cervical dumbbell schwannoma in one stage. The short-term clinical effect is good, and there are no complications such as cervical instability.

[Treatment strategy and curative effect analysis of os odontoideum complicated with atlantoaxial joint dislocation].

OBJECTIVE: To explore the treatment strategy and clinical efficacy for os odontoideum complicated with atlantoaxial dislocation. METHODS: The clinical data of 17 patients with os odontoideum complicated with atlantoaxial dislocation surgically treated from January 2006 to January 2015 were retrospectively analyzed, including 7 males and 10 females, aged 17 to 53 (43.1±11.3) years old;course of disease was 3 to 27(10.2±6.9) months. All patients received cranial traction before operation, 12 of 14 patients with reducible dislocation were treated by posterior atlantoaxial fixation and fusion, and 2 patients with atlantooccipital deformity were treated by posterior occipitocervical fixation and fusion;3 patients with irreducible alantoaxial dislocation were treated by transoral approach decompression combined with posterior atlantoaxial fixation and fusion. The operation time, intraoperative blood loss and perioperative complications were recorded. Visual analogue scale (VAS) and Japanese Orthopaedic Association (JOA) score were used to evaluate the change of neck pain and neurological function. Atlantoaxial joint fusion rate was evaluated by CT scan. RESULTS: The operation time of posterior fixation and fusion ranged from 86 to 170 (92.2±27.5) min, and the intraoperative blood loss was 200-350 (250.7±65.2) ml. No vertebral artery injury and spinal cord injury were recorded. Among the patients underwent atlantoaxial fixation and fusion, 1 patient with reducible dislocation fixed by C2 laminar screw lost reduction after primary operation, and received anterior release again and finally occipitocervical fusion. All patients were followed up for 15 to 58 (32.0±12.2) months. VAS score was decreased from preoperative 4.2±0.9 to 1.3±0.7 at final follow up and the JOA score was improved from preoperative 11.2±1.2 to 16.9±0.8 at final follow-up. CT scan confirmed that the atlantoaxial or occipitocervical fusion wasgood, and the fusion time was 5 to 9 (6.7±0.6) months. CONCLUSION: Surgical treatment of os odontoideum complicated with atlantoaxial dislocation can achieve satisfactory results, improve the patient's neurological function and improve the quality of life, however the surgical options needs to be individualized.

Reconsidering the tectorial membrane: A morphological study.

BACKGROUND: Published descriptions of the tectorial membrane have been inconsistent. Descriptions vary from a simple ligamentous band extending between the axis and occiput to a more complex layered structure composed of bands of fibers. The purpose of this study was to examine and document the macrostructure of the tectorial membrane. MATERIALS AND METHODS: The tectorial membrane was examined by fine dissection in 11 formalin-fixed human adult cadavers. Detailed descriptions of the macrostructure and attachments were recorded. RESULTS: Each tectorial membrane examined consisted of two distinct layers. The superficial layer was composed variably of three or four bands. Its fibers extend caudally over multiple spinal levels, becoming continuous with the posterior longitudinal ligament. The deeper layer routinely consisted of three bands, each being firmly adherent to the posterior aspect of the body of the second cervical vertebra. Attachments of fibers from both layers extended beyond the foramen magnum to create a semicircular attachment onto the base of the skull. CONCLUSIONS: The tectorial membrane has a more complex structure than has been described to date in standard anatomical texts. The existence of a layered and banded composition may have implications for understanding its function and for the clinical assessment of this structure.

Freehand Placement of the C1 Pedicle Screw Using Direct Visualization of the Pedicle Anatomy and Serial Dilatation.

OBJECTIVE: We designed a method for inserting C1 pedicle screws using the direct visualization technique of the pedicle and serial dilatation technique to reduce complications and malposition of screw, and assessed the accuracy of this method. METHODS: Free-hand C1 pedicle screw insertion using the direct visualization technique of the pedicle and serial dilatation technique was performed on 5 consecutive patients with C1-2 instability at a single institute from March to December 2018. The method involved protecting the vertebral artery (VA) and C1 root using the Penfield No. 1, securing the entry point of the posterior arch screw and the pedicle was visible directly in Trendelenburg position. The hole at the entry point of the C1 posterior arch was serially dilated using a 2.5×3.0 mm drill bit, and the C1 pedicle screw was inserted with the free hand technique. We measured postoperative radiological parameters and recorded intraoperative complications, postoperative neurological deficits and the occurrence of occipital neuralgia. Postoperative computed tomography (CT) was performed to check screw malposition or construction failure. RESULTS: Of the 10 C1 pedicle screws on postoperative CT, 20% of screws (grade A) were in the ideal position while 80% of screws (grade B) occupied a safe position. Overall, 100% of screws were safe (grade A or B). There were no iatrogenic neurological deficits, VA injury. CONCLUSION: Freehand placement of the C1 pedicle screw through the direct visualization technique of the pedicle and serial dilatation technique is safe and effective without intraoperative fluoroscopy guidance.

Radiographic and Clinical Results of C1 Laminoplasty for the Treatment of Compressive Myelopathy.

STUDY DESIGN: Case series. PURPOSE: To evaluate the radiographic and clinical results of C1 laminoplasty without fusion. OVERVIEW OF LITERATURE: C1 laminectomy has been the standard procedure for decompression at the C1 level. However, there have been some reports of trouble cases after C1 laminectomy. C1 laminoplasty might be superior to C1 laminectomy with regard to maintaining the original C1 anatomical shape, preventing compression from the posterior soft tissue, and ensuring an adequate bonegrafting site around the C1 posterior part if additional salvage fusion surgery is necessary afterward. METHODS: Seven patients with spinal cord compression without obvious segmental instability at the C1/2 level treated by C1 laminoplasty were included. The indication of C1 laminoplasty was same as that of C1 laminectomy. C1 laminoplasty was performed in the same way as subaxial double-door laminoplasty. The imaging findings were evaluated using X-ray, computed tomography, and magnetic resonance imaging. The clinical results were evaluated using the Japanese Orthopaedic Association (JOA) Cervical Myelopathy Evaluation Questionnaire (JOACMEQ) and JOA score. Peri- and postoperative complications were also investigated. RESULTS: No patient showed increased C1/2 segmental instability after the surgery. The mean pre- and postoperative JOA scores were 8.6 and 11.7, respectively. The mean recovery rate was 40.2%. The effective rate in the JOACMEQ was 50% for the cervical spine function, 33% for the upper extremity function, 50% for the lower extremity function, 17% for the bladder function, and 17% for the quality of life. No major complication that seemed to be unique to C1 laminoplasty was observed over a period of about 4 years follow-up. CONCLUSIONS: C1 laminoplasty for patients without obvious segmental instability might be a viable alternative procedure to C1 laminectomy.

Agenesis of the posterior arch of the atlas and complex alterations of the craniovertebral junction: A case report.

The craniovertebral junction is a unique part of the somite-derived axial skeleton. The absence or hypoplasia of the posterior arch of C1 is frequently associated with compensatory hypertrophy of the anterior arch of C1 and of the spinous process of C2. Here, we report a patient with agenesis of the posterior arch of C1 without neurologic deficits. Our patient presented with complex alterations of the craniovertebral junction that involved interactions between the condyles, clivus, atlas, and epistropheus. To our knowledge, dislocation of the odontoid process above the Chamberlain line, including cranial migration of the anterior arch of C1, has not been reported in the literature.

The Retrotransverse Foramen of the Atlas Is not a Modern Anatomic Variation.

BACKGROUND: The retrotransverse foramen (RTF) is a nonmetric variant of the atlas vertebra that consists of an abnormal accessory foramen located on the posterior root of the transverse process and it extends from the posterior root of the transverse process to the root of the posterior arch. Its presence has been related to regional variations of the venous circulation. It is currently unknown whether the RTF is a modern or an ancient anatomic variation. CASE DESCRIPTION: We analyzed the skeletal remains from the late-ancient Roman necropolis (II-VI centuries ad) of La Boatella (Valencia, Spain) and we found a well-preserved individual skeleton that presented with a left retrotransverse foramen in C1. CONCLUSIONS: The RTF is not a modern anatomic variation. As a result, ancient individuals had the same modifications in the regional circulation as modern subjects present today.