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.
Brain ; Cadaver ; Cervical Atlas ; Craniocerebral Trauma ; Female ; Humans ; Male ; Mass Screening ; Observational Study ; Spine ; Standard of Care ; Tomography, X-Ray Computed

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.
Axis, Cervical Vertebra ; Cervical Atlas ; Prevalence ; Retrospective Studies ; Vertebral Artery

The commonly used examination procedures of the upper cervical spine depend upon the symmetry for comparison and interpretation of joint functions. If symmetry is not normal, then these assessments may mislead the examiners, allowing them implementation of incorrect treatment plans. Objectives of this study are to explore the possibility that asymmetry is more common than symmetry and, if it is true, to find out the effects of asymmetry on the biomechanics of these joints. The study was carried out on 30 atlas vertebrae of cadavers of Indian origin. The different intra-atlas distances were measured on both sides by digital vernier calliper. All the parameters studied showed statistically significant differences between the right and left side i.e. a p value of < 0.05. The anteroposterior diameter of the foramen transversarium, the transverse diameter of the foramen transversarium, the distance from the midline to medial edge of the vertebral artery groove (inner as well as outer cortex) and the length of the superior articular facets were more on the right side as compared to the left side. The breadth as well as the length of the inferior articular facet, the breadth of the superior articular facet and the difference of posterior arch thickness at the site of vertebral artery groove were more on the left side as compared to the right side. These differences may be explained by the handedness of an individual, which influences the intra-osteal asymmetry in a characteristically distinct manner, which needs to be confirmed or refuted in a further study.
Cervical Atlas

OBJECTIVETo study the biomechanical change of the craniovertebral junction in conditions of atlas assimilation.

METHODSMimics software was used to process CT data of the craniovertebral junction in a health adult to obtain the three-dimensional reconstruction and the cloudy points of C1, C2 and part of the occipital bone. Then the cloudy points were imported into the Abaqus 6. 8 software to establish the occipito-atlantoaxial finite element model in normal structure. According to the established model in normal structure, the model in conditions of atlas assimilation was set by changing the model parameters. Both models of normal structure and atlas assimilation were loaded with 1. 5 N . m static moment to simulate four motions of flexion, extension, lateral bending and axial rotation respectively. The movement characteristics,joint stress force and ligament deformation was analyzed.

RESULTSUnder 1. 5 N . m moment, in model of atlas assimilation the C1-C2 range of movement decreased from 13. 55° to 11.88° in flexion,increased from 13. 22° to 15. 24° in extension and from 4. 05° to 4. 23° in lateral bending and remained unchanged in axial rotation when compared with the normal model. In flexion movement, the contact force of the atlanto-dental joint increased from 1. 59 MPa to 3. 28 MPa and the deflection of apical ligament, tectorial membrane and alar ligament increased 129. 1%, 157. 6% and 75. 1% respectively when compared with the normal model.

CONCLUSIONSThe normal C1-C2 motion mode is destructed in conditions of atlas assimilation, leading to the changes of the range of movement,joint stress force and the ligament deformation at C1 C2 junction. The atlantoaxial instability will likely occur in flexion motion.

Atlanto-Axial Joint ; physiology ; Biomechanical Phenomena ; Cervical Atlas ; physiology ; Cervical Vertebrae ; Finite Element Analysis ; Humans ; Imaging, Three-Dimensional ; Joint Instability ; Ligaments, Articular ; Occipital Bone ; Range of Motion, Articular ; Rotation

Atlas fracture accounts for 1% to 3% of all spinal column injuries and 10% of cervical spine fractures, and is most frequently caused by motor vehicle accidents and falls. Only a few cases involving complications after surgical treatment have been reported. We present a case of anterior atlas arch stress fracture accompanied by worsening neurologic symptoms following atlas posterior arch resection for cervical myelopathy with retro-odontoid pseudotumor.
Cervical Atlas ; Fractures, Stress* ; Motor Vehicles ; Neurologic Manifestations ; Spinal Cord Diseases* ; Spine

The present of atlanto-axial pedicle screw fixation through posterior approach provide a new remedy for treating instability of pillow and cervical. A lot of researches have reported feasibility of atlanto-axial pedicle screw fixation, the results showed that it had advantages of easily exposure, less blood loss, shorter operative time, especially in treating as remedy fixation for atlanto-axial joint screw, atlas lateral mass screws and pedicle screw caused by injuries of tumor,inflammation and trauma. If not done properly, it can cause serious complications, such as iatrogenic fracture,injuries of vertebral artery and cervical spinal cord. Therefore,the safty and effectiveness of atlanto-axial pedicle screw fixation may be focus of research.
Atlanto-Axial Joint ; surgery ; Bone Screws ; utilization ; Cervical Atlas ; surgery ; Fracture Fixation, Internal ; instrumentation ; methods ; trends ; Humans ; Spinal Fractures ; surgery

OBJECTIVETo explore the ideal screw entry point and optimal trajectory for anterior C1 lateral mass screw internal fixation, and provide an anatomical basis for the technique of anterior C1 lateral mass screw placement.

METHODSA radiographic analysis of the anatomy of the C1 lateral mass using Computed tomography, CT scan was performed in cervical spine of 56 healthy Chinese adults (28 males, 28 females; mean age, 36.5 years; age range, 18-55 years), by using the Mimics software to reconstruct the 3-D morphology of C1 lateral mass and measuring the inside, middle and outside effective height of the C1 lateral mass in front and back. Measuring the C1 lateral mass safe width with different extraversion angles range from 0° to 30° with a uniform interval of 5°, to find out the ideal extraversion angle. Measuring the range of sagittal angle, to find out the ideal sagittal angle.

RESULTSThe inside (H1), middle (H3) and outside (H5) effective height of the C1 lateral mass in front is 6.67 mm, 12.09 mm, and 17.51 mm, the inside (H2), middle (H4) and outside(H6) effective height of the C1 lateral mass in back is 8.17 mm, 13.20 mm, and 18.22 mm. When the extraversion angle choose 0°, 5°, 10°, 15°, 20°, 25°, 30°, and δ, the relative results of safe width (SW) of lateral mass were 4.73 mm, 5.36 mm, 5.90 mm, 6.33 mm, 6.44 mm, 5.70 mm, 4.38 mm, 6.95 mm averagely. The mean distance along the atlas anterior surface between the anterior tubercle and the screw entry point was 12.80 mm, the mean distance from the inferior border of the lateral mass to the screw entry point was 6.87 mm. The range of sagittal angle is 24.22° (-17.74°∼6.48°) .

CONCLUSIONSThe ideal extraversion angle was 21.14°. The mean distance along the atlas anterior surface between the anterior tubercle and the screw entry point was 12.80 mm. The mean distance from the inferior border of the lateral mass to the screw entry point was 6.87 mm. The ideal sagittal angle is -5.63°. These measurements may facilitate anterior C1 lateral mass screw fixation decreasing the risk of injury to the spinal cord, vertebral artery, and internal carotid artery theoretically. Delineating the individual anatomy in each case with CT scan before surgery is recommended.

Adolescent ; Adult ; Bone Screws ; Carotid Artery, Internal ; diagnostic imaging ; Cervical Atlas ; Cervical Vertebrae ; diagnostic imaging ; surgery ; Female ; Fracture Fixation, Internal ; instrumentation ; Humans ; Image Processing, Computer-Assisted ; Male ; Middle Aged ; Reconstructive Surgical Procedures ; Tomography, X-Ray Computed ; Vertebral Artery ; diagnostic imaging ; Young Adult

Partial or complete absence of the posterior arch of the atlas is a well-documented anomaly but a relatively rare condition. This condition is usually asymptomatic so most are diagnosed incidentally. There have been a few documented cases of congenital defects of the posterior arch of the atlas combined with atlantoaxial subluxation. We report a very rare case of congenital anomaly of the atlas combined with atlantoaxial subluxation, that can be misdiagnosed as posterior arch fracture.
Adult ; Cervical Atlas/*abnormalities ; Diagnosis, Differential ; Female ; Humans ; Spinal Diseases/*diagnosis

OBJECTIVETo explore radiographic results and clinical effects of posterior atlanto axial vertebra internal fixation in treating instability of occipitocervical.

METHODSThe clinical data of 155 patients with instability of occipitocervical treated by posterior atlanto axial vertebra internal fixation were respectively analyzed from September 2005 to January 2011. There were 68 males and 87 females, ranging in age from 6 to 75 years old with an average of 45.6 years old. Of them, 53 cases were fresh odontoid fractures(Aderson type II C), 30 cases were os odontoideum, 20 cases were old odontoid fractures, 18 cases were unstable atlas fractures, 12 cases were atlanto axial rotatory dislocation, 11 cases were atlanto axial dislocation after rheumatoid arthritis, and 11 cases were basilar invagination. Radiographic results were evaluated in terms of atlas pedicle screw fixation, bone healing and bone graft fusion. Clinical effect evaluation included relief of pain in the occipital-cervical region by VAS score and JOA score.

RESULTSTotally 300 screws were set through atlas pedicle screw fixation in 150 patients. Five patients receivde hook fixation. Postoperative CT showed ideal nailing were 275 (91.7%),acceptable nailing were 14 (4.7%) and unacceptable nailing were 11 (3.6%). All patients were followed up, and the duration ranged from 16 to 40 months with an average of 25.4 months. The fresh fractures healed and 140 cases got bone graft fusion. Preoperative VAS and JOA score were respectively improved from (7.2 +/- 1.1), (7.3 +/- 2.4) to (3.2 +/- 1.1), (13.3 +/- 2.4) at the latest follow-up.

CONCLUSIONPosterior atlanto axial vertebra internal fixation in treating instability of occipitocervical can effectively recover physiological curvature of cervical, provide mechanical stability, and obtain good clinical effect. For the young patients who require further activity, posterior fixation and non-fusion technology is a good choose, which can avoid bone graft.

Adolescent ; Adult ; Aged ; Atlanto-Axial Joint ; surgery ; Bone Screws ; Cervical Atlas ; surgery ; Child ; Female ; Fracture Fixation, Internal ; Humans ; Internal Fixators ; Joint Instability ; surgery ; Male ; Middle Aged ; Retrospective Studies ; Treatment Outcome ; Young Adult

OBJECTIVETo evaluate the efficacy and safety of transoral plate internal fixation for instability atlas fracture.

METHODSA retrospective study was performed in eight patients with instability atlas fractures, who were treated by a transoral plate internal fixation from July 2007 to June 2011. There were 6 males and 2 females,with an average age of 39.5 years old ranging from 23 to 48 years. Among them, 5 case were falling injury, 3 cases were traffic accident injury. Three patients had bilateral fractures of the anterior arch (prehalf Jefferson fractures, Landells type I), 5 had anterior are fracture associated posterior are fracture (Half-ring Jefferson fractures, Landells type II), and 2 had anterior and posterior are fracture associated with single lateral mass fractures (Landells type III).

RESULTSAll patients were followed up for 6 to 24 months after operation (av- eraged 13 months), and all the patients had the clinical symptoms improved to some extent. Operation time ranged from 80 to 140 min (averaged 98 min); the intra-operative blood loss was 120 to 300 ml (averaged 180 ml); and the average fluoroscopic time was 55 s. No patients happened neurological and vertebral artery injuries-related complications or other complications after operation. The followed-up X-ray and CT manifested osseous fusion in all the 8 patients,no loosening or breakage of the screws.

CONCLUSIONTransoral plate internal fixation for instability atlas fracture is a reliable and safety technique that allows maintenance of rotatory mobility in the C1,2 joint and restoration of congruency in the atlanto-occipital and atlanto-axial joints.

Adult ; Bone Plates ; Cervical Atlas ; injuries ; surgery ; Female ; Fracture Fixation, Internal ; methods ; Fractures, Bone ; surgery ; Humans ; Male ; Middle Aged ; Retrospective Studies