Atlanto-occipital assimilation is one of the most common osseous anomalies observed at the craniocervical junction. Most patients with atlas assimilation show no symptom, but some have neurological problems such as myelopathy that may require surgical treatment. Occipitocervical fusion may be required if atlato-occipital assimilation is accompanied by occipito-axial instability. However, in cases of symptomatic atlas assimilation with minor cord compression without instability, simple decompressive surgery may be the treatment modality. This report describes a case of successful treatment of a patient with myelopathy secondary to atlanto-occipital assimilation without instability, using posterior simple decompressive surgery.
Atlanto-Occipital Joint ; Decompression ; Humans ; Spinal Cord Diseases*

Occipito-atlantalrotatory subluxation that occurs in conjunction with atlanto-axial rotator fixation is extremely rare. The common clinical characteristics are painful torticollis and cock robin position presented with the head tilted to one side and rotated to the other side. The object of this report is to emphasize that AARF combined with OARF may be caused by a variety of conditions, to be must need algorithm for proper management, apparently. A torticollis patient who had cerebral palsy presented with severe nuchal pain and wryneck for a long period. The patient had a history of fallen down 16 years ago which caused severe nuchal pain. The conservative management had failed to correct the deformity and instability. we decided to operate using occiput-C1-C2 arthrodesis and C3-4-5 bilateral screw fixation for reinforcement. Now he doesn't have neurologic deficit and shows good outcome enough to sustain his head, not using his hands, in his daily life.
Arthrodesis ; Atlanto-Axial Joint ; Atlanto-Occipital Joint ; Cerebral Palsy* ; Congenital Abnormalities ; Hand ; Head ; Humans ; Neurologic Manifestations ; Songbirds ; Torticollis

OBJECTIVE: To evaluate the feasibility of ultrasound guided atlanto-occipital joint injection. METHOD: Six atlanto-occipital joints of three cadavers were examined. Cadavers were placed in prone position with their head slightly rotated towards the contra-lateral side. The atlanto-occipital joint was initially identified with a longitudinal ultrasound scan at the midline between occipital protuberance and mastoid process. Contrast media 0.5cc was injected into the atlanto-occipital joint using an in-plane needle approach under ultrasound guide. The location of the needle tip and spreading pattern of the contrast was confirmed by fluoroscopic evaluation. RESULTS: After ultrasound guided atlanto-occipital joint injection, spreading of the contrast media into the joint was seen in all the injected joints in the anterior-posterior fluoroscopic view. CONCLUSION: The ultrasound guided atlanto-occipital injection is feasible. The ultrasound guided injection by Doppler examination can provide a safer approach to the atlanto-occipital joint.
Atlanto-Occipital Joint ; Cadaver ; Contrast Media ; Head ; Joints ; Mastoid ; Needles ; Prone Position

STUDY DESIGN: Retrospective study. PURPOSE: To propose a new radiographic index for occipito-cervical instability. OVERVIEW OF LITERATURE: Symptomatic atlanto-occipital instability requires the fusion of the atlanto-occipital joint. However, measurements of occipito-cervical translation using the Wiesel-Rothman technique, Power's ratio, and basion-axial interval are unreliable because the radiologic landmarks in the occipito-cervical junction lack clarity in radiography. METHODS: One hundred four asymptomatic subjects were evaluated with lateral cervical radiographs in neutral, flexion and extension. They were stratified by age and included 52 young (20-29 years) and 52 middle-aged adults (50-59 years). The four radiographic reference points were posterior edge of hard palate (hard palate), posteroinferior corner of the most posterior upper molar tooth (molar), posteroinferior corner of the C1 anterior ring (posterior C1), and posteroinferior corner of the C2 vertebral body (posterior C2). The distance from posterior C1 and posterior C2 to the above anatomical landmarks was measured to calculate the range of motion (ROM) on dynamic radiographs. To determine the difference between the two age groups, unpaired t-tests were used. The statistical significance level was set at p<0.05. RESULTS: The ROM was 4.8+/-7.3 mm between the hard palate and the posterior C1, 9.9+/-10.2 mm between the hard palate and the posterior C2, 1.7+/-7.2 mm between the molar to the posterior C1, and 10.4+/-12.1 mm between the molar to the posterior C2. There was no statistically significant difference for the ROM between the young- and the middle-aged groups. The intra-observer reliability for new radiographic index was good. The inter-observer reliability for the ROM measured by the hard palate was low, but was better than that by the molar. CONCLUSIONS: ROM measured by the hard palate might be a useful new radiographic index in cases of occipito-cervical instability.
Adult ; Atlanto-Occipital Joint ; Humans ; Molar ; Palate, Hard ; Radiography ; Range of Motion, Articular ; Retrospective Studies ; Tooth

STUDY DESIGN: Cadaveric, observational study.PURPOSE: Atlantoaxial instability (AAI) is characterized by excessive movement at the C1–C2 junction between the atlas and axis. An anterior surgical approach to expose the upper cervical spine for internal fixation and bone grafting has been developed to fix AAI. Currently, no anatomic information exists on the anterior transarticular atlantoaxial screw or screw and plate fixation between C1 and C2 in the Indian population. The objective of this study is to assess the anatomic landmarks of C1–C2 vertebrae: entry point, trajectory, screw length, and safety of the procedure.OVERVIEW OF LITERATURE: Methods outlined by Magerl and Harms are the optimal approaches among the dorsal techniques. Contraindications for these techniques include aberrant location of vertebral arteries, fractures of C1–C2 posterior structures. In these cases, anterior transarticular fixation is an alternative. Several available screw insertion trajectories have been reported. Biomechanical studies have demonstrated that adequate rigidity of this fixation is comparable with posterior fusion techniques.METHODS: Direct measurements using Vernier calipers and a goniometer were recorded from 30 embalmed human cadavers. The primary parameters measured were the minimum and maximum lateral and posterior angulations of the screw in the sagittal and coronal planes, respectively, and optimum screw length, if it was placed accurately.RESULTS: The posterior and lateral angles of screw placement in the coronal and sagittal planes ranged from 16° to 30° (mean±standard deviation [SD], 23.93°±3.93°) and 8° to 17° (mean±SD, 13.3°±2.26°), respectively. The optimum screw length was 25–38 mm (mean±SD, 28.76±3.69 mm).CONCLUSIONS: If the screw was inserted without lateral angulation, the spinal canal or cord could be violated. If a longer screw was inserted with greater posterior angulation, the vertebral artery at the posterior or posterolateral aspect of the C1 superior facet could be violated. Thus, 26° and 30° of lateral and posterior angulations, respectively, are the maximum angles permissible to avoid injury of the vertebral artery and violations of the spinal canal or atlanto-occipital joint.
Anatomic Landmarks ; Atlanto-Occipital Joint ; Bone Transplantation ; Cadaver ; Humans ; Observational Study ; Spinal Canal ; Spine ; Vertebral Artery

Patients with atlanto-occipital dislocation (AOD) are increasingly being transported to emergency rooms, alive, by the improved pre-hospital emergency rescue system. The author reports a fatal case of AOD with severe neurovascular injuries following a high-speed pedestrian collision. Therefore, nowadays, neurosurgeons can expect an increase in the occurrence of such cases; an early diagnosis and prompt occipitocervical fusion can save lives. This report reviews the current concepts of AOD in mild to fatal conditions.
Atlanto-Occipital Joint ; Dislocations ; Early Diagnosis ; Emergencies ; Emergency Service, Hospital ; Humans ; Neurosurgeons

Rigid posterior fixation of the atlas to the third and fourth cervical spine was achieved in a patient in whom axis pedicle fracture and dislocation of axis on the third cervical spine. Althouth there was no evidence of neurologic disorder, marked instability of axis on the third cervical spine should inevitably be fused in any procedures. An anatomically contoured loop was secured to the posterior arch of the atlas and the laminae of the third and the fourth cervical spine by sublaminar wirings. The technique has the advantage over bone graft, either alone or with cement, in that it affords rigid stabilization, allows early mobilization and some flexion movement of atlanto-occipital joint.
Atlanto-Occipital Joint ; Dislocations ; Early Ambulation ; Humans ; Nervous System Diseases ; Spine ; Spondylolisthesis ; Transplants

Based on the research history of the biomechanics of occipito-atlantoaxial complex, we have systematically summarized the use of finite element method for studying biomechanics of occipito-atlantoaxial complex. Then, combined with four basic principles of establishing an effective finite element model for mechanics, our comments are focused on the establishment of geometrical model, finite element model, finite element mechanics model, and on the method and implementation for validating the model. In addition, the developing trends, existing problems and future researching directions in this area are discussed.
Atlanto-Axial Joint ; physiology ; Atlanto-Occipital Joint ; physiology ; Biomechanical Phenomena ; Computer Simulation ; Finite Element Analysis ; Humans ; Models, Biological ; Range of Motion, Articular ; physiology

Atlanto-occipital dislocation (AOD) is rarely seen in clinic because it is characteristically immediately fatal. With recent progress in the pre-hospital care, an increasing number of AOD survivors have been reported. However, because the pathophysiology of AOD is not clearly understood yet, the appropriate strategy for the initial management remains still unclear. We report a case of successful AOD treatment and describe important points in the management of this condition. It is important to note that abducens nerve palsy is a warning sign of AOD and that AOD can result in a life-threatening distortion of the arteries and the brain stem. We recommend the application of a halo vest to protect the patient's neural and vascular competence as the immediate initial step in the treatment of AOD. Horn's grading system is useful in assessing indications for surgery. Finally, when performing posterior fixation, C2 should be included because of the anatomy of the ligamentous architecture.
Abducens Nerve Diseases ; Arteries ; Atlanto-Occipital Joint ; Brain Stem ; Dislocations* ; External Fixators ; Humans ; Internal Fixators ; Ligaments ; Mental Competency ; Survivors

STUDY DESIGN: Retrospective case-control study, level 4. PURPOSE: To clarify the risk factors for late subaxial lesion after occipitocervical (O-C) reconstruction. We examined cases requiring fusion-segment-extended (FE) reconstruction in addition to/after O-C reconstruction. OVERVIEW OF LITERATURE: Patients with rheumatoid arthritis (RA) frequently require O-C reconstruction surgery for cranio-cervical lesions. Acceptable outcomes are achieved via indirect decompression using cervical pedicle screws and occipital plate–rod systems. However, late subaxial lesions may develop occasionally following O-C reconstruction. METHODS: O-C reconstruction using cervical pedicle screws and occipital plate–rod systems was performed between 1994 and 2007 in 113 patients with RA. Occipito-atlanto-axial (O-C2) reconstruction was performed for 89 patients, and occipito-subaxial cervical (O-under C2) reconstruction was performed for 24 patients. We reviewed the cases of patients requiring FE reconstruction (fusion extended group, FEG) and 26 consecutive patients who did not require FE reconstruction after a follow-up of >5 years (non-fusion extended group, NEG) as controls. RESULTS: FE reconstructions were performed for nine patients at an average of 45 months (range, 24–180 months) after O-C reconstruction. Of the 89 patients, three (3%) underwent FE reconstruction in cases of O-C2 reconstruction. Of the 24 patients, five (21%) underwent FE reconstruction in cases of O-under C2 reconstruction (p=0.003, Fisher exact test). Age, sex, RA type, and neurological impairment stage were not significantly different between FEG and NEG. O-under C2 reconstruction, larger correction angle (4° per number of unfixed segment), and O-C7 angle change after O-C reconstruction were the risk factors for late subaxial lesions on radiographic assessment. CONCLUSIONS: Overcorrection of angle at fusion segments requiring O-C7 angle change was a risk factor for late subaxial lesion in patients with RA with fragile bones and joints. Correction should be limited, considering the residual mobility of the cervical unfixed segments.
Arthritis, Rheumatoid ; Atlanto-Occipital Joint ; Case-Control Studies ; Decompression ; Follow-Up Studies ; Humans ; Joints ; Pedicle Screws ; Retrospective Studies ; Risk Factors