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.

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.

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.

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.

[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.

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.

[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 C_1,2. 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.

[Minimally invasive treatment of cervical1-2 epidural neurilemmoma]

OBJECTIVE

To explore the minimally invasive surgical method for cervical_1-2 epidural neurilemmoma.

METHODS

The clinical features, imaging characteristics and surgical methods of 63 cases of cervical_1-2 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 cervical_1-2 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 cervical_1-2 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.

[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.

[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.

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 bone-grafting 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.

Computed Tomography Scan-Based Morphometric Analysis of Lateral Masses of Atlas Vertebrae in Normal Indian Population

Study Design

A cross-sectional observational study involved the analysis of computed tomography (CT) scan data from 125 Indian subjects of 18 years or older with normal imaging findings. Scans were obtained from patients with head injuries as a part of the screening process along with brain CT scans.

Purpose

To establish the dimensions of lateral masses of the atlas vertebrae in normal disease-free Indian individuals.

Overview of Literature

Lateral mass fixation has become the standard of care in fixation of the supra-axial cervical spine. Many studies have investigated the dimensions of lateral masses in cadaveric specimens; however, studies involving the radiological morphometric analysis of the lateral masses of the atlas vertebra in living patients are lacking.

Methods

Subjects underwent craniovertebral junction CT scans during evaluations of head injury. All had normal radiology reports. The CT scans were obtained using a CT Philips Brilliance 64 machine (Philips, Amsterdam, Netherlands) with a slice thickness of 1 mm and then analyzed using Horos software ver. 2.0.2 (Horos Project, Annapolis, MD, USA) on a MacBook.

Results

Lateral masses of the atlas vertebrae were found to be larger in males than females and larger on the right than the left side. The angle of permissible medialization was found to be larger on the right side. The analysis of the average dimensions indicated the conventionally described screw positions to be safe.

Conclusions

The present study provides information that may help to establish standard dimensions of lateral masses of the atlas vertebrae among the normal Indian population. We demonstrate that there is no significant difference when compared with the Western population. The results presented here will be of use to clinicians as they may inform preoperative planning for lateral mass fixation surgeries.

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.

Biomechanical and Anatomical Validity of the Short Posterior Arch Screw

Objective

This 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.

Methods

Nine 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.

Results

The 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).

Conclusion

The via-PAS and S-PAS are valid surgical options, even in elderly patients. Along with sufficient biomechanical strength, the S-PAS screw prevents VAI.

The Transspinal Canal Screwing Technique for Atlantoaxial Anomalies: A Technical Note and 2 Case Reports

It is difficult to treat atlantoaxial instability in patients with a high-riding vertebral artery or anomalies of the craniocervical junction. We report 2 successful cases in which the transspinal canal screwing technique was used because of difficulties performing conventional fixation methods. Case 1: A 78-year-old woman suffered from progressive myelopathy due to severe spinal cord compression with a congenital anomaly of the craniovertebral junction. Bilateral transspinal canal screws from the axis body with spondylolisthesis to the dens were inserted by retracting the dural sac medially after foramen magnum decompression and cervical laminoplasty. Case 2: A 20-year-old man with a spinal deformity due to Loeys-Dietz syndrome presented to our hospital for treatment of syringomyelia. He had no obvious neurological deficits, but spinal cord compression due to right atlantoaxial rotating dislocation was observed. A screw was inserted from the vertebral body of the axis to the right lateral mass of the atlas via the spinal canal after laminectomy of the atlas. The transspinal canal screwing technique is useful for treating atlantoaxial instability in cases where other fixation methods are difficult.

Atlases with Arcuate Foramen Present Cortical Bone Thickening That May Contribute to Lower Fracture Risk

BACKGROUND

To date, no information about the cortical bone microstructural properties in atlas vertebrae with arcuate foramen has been reported. As a result, we aimed to test in an experimental model if there is a cortical bone thickening in an atlas vertebra which has an arcuate foramen that may play a protective role against bone fracture.

METHODS

We analyzed by means of micro-computed tomography the cortical bone thickness, the cortical volume, and the medullary volume (SkyScan 1172 Bruker micro-CT NV, Kontich, Belgium) in cadaveric dry atlas vertebrae with arcuate foramen and without arcuate foramen. We also reviewed a case series of 31 posterior atlas arch fractures to correlate the possible presence in the same atlas of both fracture and arcuate foramen.

RESULTS

The micro-computed tomography study revealed significant differences in cortical bone thickness (P < 0.001), cortical volume (P < 0.004), and medullary volume (P = 0.013) values between the arcuate foramen vertebrae and the nonarcuate foramen vertebrae. The clinical series found no coexistence in the same vertebra of a posterior atlas arch fractures and the arcuate foramen.

CONCLUSIONS

An atlas with arcuate foramen presents cortical bone thickening. This advantage in bone microarchitecture seems to contribute to a lower fracture risk compared to subjects without arcuate foramen as no coexistence in the same vertebra of a posterior atlas arch fractures and arcuate foramen was found.

Congenital malformed posterior arch of atlas with fusion defect: a case of developmental canal stenosis causing cervical myelopathy

Congenital anomalies of the posterior arch of the atlas (PAA) are usually asymptomatic and diagnosed incidentally. Very rarely, they present with cervical myelopathy, usually being associated with partial aplasia or agenesis of PAA. We describe a 44-year-old lady with cervical myelopathy secondary to a malformed PAA with developmental atlas-level spinal stenosis and a congenital posterior fusion defect with persistent midline cleft showing significant non-osseous fibro-cartilaginous hypertrophy, causing critical cord compression. Spinal decompression by en-bloc wide excision of anomalous arch with occipito-cervical fusion was performed. Post-operatively, the patient's neurology improved gradually over 12 months, with radicular symptoms being the earliest and gait disturbance being the last symptom to resolve. At 24 months, she was asymptomatic with imaging showing good spinal cord decompression at the level of atlas. Developmental atlas stenosis with hypertrophic posterior arch fusion defect is an unusual cause of cervical myelopathy, which can be effectively treated with decompression with/without stabilization. Being aware of such an entity can avoid diagnostic dilemma and facilitate prognostication of outcomes, accurate surgical planning in the stenotic segment thereby ensuring effective management of these patients.

Cortical bone thickening in Type A posterior atlas arch defects: experimental report

BACKGROUND CONTEXT

To date, no information about the cortical bone microstructural properties in atlas vertebrae with posterior arch defects has been reported.

PURPOSE

To test if there is an increased cortical bone thickening in atlases with Type A posterior atlas arch defects in an experimental model.

STUDY DESIGN

Micro-computed tomography (CT) study on cadaveric atlas vertebrae.

METHODS

We analyzed the cortical bone thickness, the cortical volume, and the medullary volume (SkyScan 1172 Bruker micro-CT NV, Kontich, Belgium) in cadaveric dry vertebrae with a Type A atlas arch defect and normal control vertebrae.

RESULTS

The micro-CT study revealed significant differences in cortical bone thickness (p=.005), cortical volume (p=.003), and medullary volume (p=.009) values between the normal and the Type A vertebrae.

CONCLUSIONS

Type A congenital atlas arch defects present a cortical bone thickening that may play a protective role against atlas fractures.

Simultaneous lateral ponticle with facet-like depression and epitransverse process of the atlas

The lateral ponticle and epitransverse process are rare anatomical variations found on the atlas vertebra of the cervical spine. When a lateral ponticle occurs, an abnormal bony bridge extends from the superior articular facet to the transverse process. This bony bridge bisects the transverse foramen wherein the vertebral artery normally lies. In this case report, we describe a C1 specimen from an adult male with a lateral ponticle on the right side and an epitransverse process on the left side. Additionally, an articular facet-like structure was also found on the lateral ponticle's surface. Relevant literature regarding the lateral ponticle across age groups, sex, race, and species is also reviewed. We postulate that genesis of the lateral ponticle of the atlas occurs in utero, specifically during the lateral ossification of the ventral sclerotomes. To our knowledge, an articular facet-like structure on such a ponticle has not been reported previously. Moreover, simultaneous occurrence of a lateral ponticle and contralateral epitransverse process has, to our knowledge, not been reported before.

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.

Prevalence and Morphologic Characteristics of Ponticulus Posticus: Analysis Using Cone-Beam Computed Tomography

OBJECTIVE

This study evaluated the prevalence and morphologic characteristics of ponticulus posticus (PP) by using cervical 3-dimensional (3-D) cone-beam computed tomography (CBCT) scan images.

METHODS

This was a retrospective study conducted by selecting cervical 3-D CBCT images of 698 patients, which were examined for the presence and types of PP.

RESULTS

In 257 patients, 438 PPs, complete or partial, bilateral or unilateral, were identified on the 698 cervical 3-D CBCT scans; therefore, the prevalence was 36.8%. Bilateral complete PP and partial PP were observed in 6.3% and 16.2% of subjects, respectively. There was a significant difference in the prevalence between males and females (P = .001) and between the right and left sides between males and females, but not between age groups.

CONCLUSION

Ponticulus posticus is a relatively common anomaly in this Turkish sample, which may have implications for those who perform clinical procedures on the upper cervical spine.

Congenital anomaly of combined atlas-odontoid process fusion and bipartite atlas

Congenital fusion of the atlas with the odontoid process of the axis is a very rare condition caused by a segmental defect of the first cervical somite. Only 9 such cases have been reported in the literature to date. The bipartite atlas, another well-documented rare anomaly, has been observed in only 0.1% of the general population. We describe the first case of a 70-year-old male with both of these complex congenital anomalies.

Prevalence of ponticuli posticus among patients referred for dental examinations by cone-beam CT

BACKGROUND CONTEXT

Ponticulus posticus (PP) is the bony bridge that can completely or partially embrace the vertebral artery and the suboccipital nerve root at the atlas posterior arch. The PP can be a possible cause of vertigo, vertebrobasilar insufficiency, neck pain, shoulder pain, and cervicogenic headache. Moreover, the vertebral artery injury may happen during atlas lateral mass screw insertion in the presence of PP.

PURPOSE

The purpose of this study was to determine the prevalence of PP in a population of patients undergoing dental cone-beam computed tomography (CBCT) and the association between PP and atlas superior articular facet (SAF).

STUDY DESIGN

This is a retrospective study.

PATIENT SAMPLE

Five hundred consecutive patients who had undergone dental CBCT scans were included.

OUTCOME MEASURES

Outcome measures were age, sex, and radiologic measures.

METHODS

The maximum anteroposterior and transverse dimensions of atlas SAF were measured on the axial image, and then the area was calculated by using the formula for an elliptical area. The left-right differential ratios of the SAF in patients with unilateral PP were compared with those in age- and gender-matched patients without PP. The relationships among imaging findings, age, and sex were assessed with the two-tailed paired t test, χ(2) test, and logistic regression model, as appropriate.

RESULTS

The overall prevalence of PP was 7% (35 of 500 patients). There were no significant differences in the prevalence of PP with gender and age. The anteroposterior dimension, transverse dimension, and area of atlas SAF on the PP side were significantly larger than those on the non-PP side in the 18 unilateral complete PP patients (p<.001, p<.001, and p<.001, respectively) and in the 11 unilateral partial PP patients (p=.001, p=.007, and p<.001, respectively). The SAF area differential ratios in patients with unilateral PP were greater than those in the patients without PP (29.8% vs. 2.9%, p=.002 for 18 complete lesions, and 23.5% vs. 1.8%, p<.001 for 11 partial lesions).

CONCLUSIONS

The prevalence of PP and the measurement of SAF can be assessed by CBCT. The imaging findings show the larger SAF on the PP side and greater left-right difference of SAF area in the patients with unilateral PP.

Hypertrophy of the anterior arch of the atlas associated with congenital nonunion of the posterior arch: a retrospective case-control study

BACKGROUND CONTEXT

Nonunion of the posterior arch of the atlas is an uncommon but normal developmental variant. It is usually asymptomatic in the patient but may be associated with greater incidence of fracture because of increased stress on the anterior arch.

PURPOSE

We sought to determine whether anterior arch hypertrophy is present in cases of congenital nonunion of the posterior arch of the atlas.

STUDY DESIGN/SETTING

A retrospective analysis of 1 year (February 2005-January 2006) of computed tomography cervical spine studies requested by the University of California San Diego Medical Center Trauma Department was undertaken.

PATIENT SAMPLE

All patients matching the search criteria (see Study design) were included.

OUTCOME MEASURES

Area density product, defined as the midline cross-sectional area of the anterior arch on sagittal reformat multiplied by the average areal radiodensity in Hounsfield units (HU) as measured by two raters, was calculated for cases and controls.

METHODS

Cases of posterior arch nonunion were identified and matched to controls. The significance of differences in area density product between cases and controls were established by the Student t test. Interrater correlation was calculated.

RESULTS

Posterior arch nonunion was identified in 26 individuals (3.1% of 839 studies reviewed). Compared with age- and sex-matched controls, a 21% increase in area density product of the midline anterior arch was observed in posterior arch nonunion cases (773 HU-cm2 in cases vs. 637 HU-cm2 in controls; p<.001). This increase was attributable to a 21% increase in cross-sectional area (1.05 cm2 in cases vs. 0.87 cm2 in controls; p<.002). In contrast, there was no significant difference with regard to increased average radiodensity.

CONCLUSIONS

It has long been subjectively recognized but not objectively quantified, until the present study, that the anterior arch of the atlas is hypertrophied in cases of posterior arch nonunion. Anterior arch hypertrophy may represent an adaptive response to chronically elevated mechanical stress and loss of hoop strength in cases of posterior nonunion.

Complications of upper cervical spine trauma in elderly subjects. A systematic review of the literature

The frequency of cervical spine trauma in elderly patients is increasing with most injuries occurring in the upper cervical spine. These fractures are associated with a risk of sometimes life-threatening complications, although very few studies have specifically analyzed this. The goal of this study was to identify the incidence of complications in the literature (mortality and morbidity) following upper cervical spine trauma in elderly patients.

METHODS

A systematic search was performed on the MEDLINE database without limiting the search by language or date to identify all studies reporting the rate of complications after upper cervical spine trauma in patients over the age of 60.

RESULTS

Twenty-four observational studies were included, four were comparative. These studies included a total of 857 patients, mean age 76. Nearly all traumas were odontoid process fractures, and most were treated surgically (57%). The median mortality rate was 9.2% (Q1-Q3: 2.5-19.6) and the median rate of short-term complications was 15.4% (Q1-Q3: 5.8-26.9). The main late stage complication was nonunion, which developed in a mean 10 to 12% depending on the type of treatment.

CONCLUSION

Complications following cervical spine trauma are frequent in elderly patients whatever the type of treatment. Knowledge of the rate of complications in the literature and the potential risk factors is essential for the clinician to improve the information provided to patients and to prevent complications.

TYPE OF STUDY

Systematic review of the literature. Level of evidence IV.

Hypertrophic posterior arch of atlas causing cervical myelopathy

Cervical stenosis, especially of the upper cervical spine, is quite rare which can be developmental or acquired. Clefts or aplasias of anterior and posterior arches of atlas, ossification of the transverse atlantal ligament, hypertrophy of the dens and os odontoideum are rare conditions causing cervical myelopathy reported either singly or in combination. Hypertrophy of the posterior arch of atlas in the absence of any ring hypoplasia as a cause of cervical myelopathy has not been reported earlier. The authors report a case of cervical myelopathy in a 26-year-old female due to hypertrophied posterior arch of atlas which was preoperatively diagnosed as a bony tumor. Being aware of such an entity may avoid diagnostic surprises and facilitate patient prognostication and management.

Occipital neuralgia after occipital cervical fusion to treat an unstable jefferson fracture

In this report we describe a patient with an unstable Jefferson fracture who was treated by occipitocervical fusion and later reported sustained postoperative occipital neuralgia. A 70-year-old male was admitted to our center with a Jefferson fracture induced by a car accident. Preoperative lateral X-ray revealed an atlanto-dens interval of 4.8mm and a C1 canal anterior-posterior diameter of 19.94mm. We performed fusion surgery from the occiput to C5 without decompression of C1. The patient reported sustained continuous pain throughout the following year despite strong analgesics. The pain dermatome was located mainly in the great occipital nerve territory and posterior neck. Magnetic resonance images revealed no evidence of cord compression, however a C1 lamina compressed dural sac and C2 root compression could not be excluded. We performed bilateral C2 root decompression via a C1 laminectomy. After decompression, bilateral C2 root redundancy was identified by palpation. After decompression surgery, pain was reduced. This case indicates that occipital neuralgia, suggesting the need for diagnostic block, should be considered in the differential diagnosis of patients with sustained occipital headache after occipitocervical fusion surgery.

Congenital cleft of anterior arch and partial aplasia of the posterior arch of the c1

Congenital anomalies in arches of the atlas are rare, and are usually discovered incidentally. However, a very rare subgroup of patients with unique radiographic features is predisposed to transient quadriparesis after minor cervical or head trauma. A 46-year-old male presented with a 2-month history of tremor and hyperesthesia of the lower extremities after experiencing a minor head trauma. He said that he had been quadriplegic for about 2 weeks after that trauma. Radiographs of his cervical spine revealed bilateral bony defects of the lateral aspects of the posterior arch of C1 and a midline cleft within the anterior arch of the atlas. A magnetic resonance imaging revealed an increased cord signal at the C2 level on the T2-weighted sagittal image. A posterior, suboccipital midline approach for excision of the remnant posterior tubercle was performed. The patient showed significant improvement of his motor and sensory functions. Since major neurologic deficits can be produced by a minor trauma, it is crucial to recognize this anomaly.