The Os odontoideum is a developmental anomaly of the axis in which the odontoid process is divided transversely. The Atlanto-axial dislocation due to Os odontoideum is presented. At first, we have performed the posterior atlanto-axial fusion with wire fixation. But the posterior fusion failed in realignment and did not adequately decompress the deformed cord by encroachment on its ventral surface. Next time, we have experienced further improvement following transoral decompression and anterior fusion.
Axis, Cervical Vertebra ; Decompression* ; Dislocations* ; Odontoid Process

Fibrous dysplasia is a benign disorder of bone primarily affecting young people from childhood through the third decade. It usually manifests as an enlargement of bones in and about the orbits or the the cranial vault. Whether localized or diffuse, it rarely involves the cervical spine. We report a case of fibrous dysplasia involving axis combined with atlantoaxial instability which was caused by odontoid process fracture. Transfacetal screw fixation augmented with Halifax interlaminar clamp technique was applied to obtain atlantoaxial stability. Postoperative course was unevenful and postoperative radiologic findings revealed favorable fixation of atlantoaxial joint. The pertinent literature on fibrous dysplasia and atlantoaxial instability is reviewed and discussed.
Atlanto-Axial Joint ; Axis, Cervical Vertebra ; Odontoid Process ; Orbit ; Spine*

With changing mechanisms of injury, heightened clinical awareness, and better diagnostic technology, odontoid fractures constitute 9~18% of cervical fractures in recent reports. The odontoid type II fracture is the most common axis fracture and it is also the most difficult to treat. Type II fractures with greater than 6mm dens dislocation have a higher incidence of nonunion with nonoperative therapy and should be offered early operative reduction with fusion. Recently we have experienced a young male patient with odontoid type II fracture. The degree of dens dislocation was 8mm. The fractured odontoid process was removed through transoral-transpharyngeal approach and bone fusion was performed with iliac bone. And the inserted bone was fixed with screws and mini-plate for further stabilization. The operative result was good without any serious complications. The operation technique is detailed.
Axis, Cervical Vertebra ; Dislocations ; Humans ; Incidence ; Male ; Odontoid Process

Fracture of odontoid process is relatively common, but fracture of axis body without fracture of odontoid precess is known to be exceptionally. Recently, we have experienced a case of axis body fracture complicating typical Brown-Sequard syndrome below the level of C4, and we present the case with the review of literature.
Axis, Cervical Vertebra* ; Brown-Sequard Syndrome* ; Odontoid Process

Type II fracture of the odontoid process is the most common form of axis fracture, and because of the difficulty in healing, its results may be fatal. The authors subclassified these fractures as anteriorly displaced(type II-A), posteriorly displaced(type II-P), and non displaced(type II-N). Twelve patients with type II fractures underwent anterior screw fixation : three were type II-A : one, type II-P : and eight, type II-N. The mean duration of follow-up was 29.3 months, and all patients except two showed good alignment and stable fixation : these exceptions were type II-A, with 9mm displacement, and showed delayed failure of screw fixation. All type II-N, II-P, and II-A, with 3mm displacement, were successfully treated. We conclude that selection of the treatment modality should be based on the direction of displacement of odontoid process. For type II-N, II-P and II-A fractures, where displacement is mild, anterior screw fixation is a reliable method, but for type II-A fracture, with severe displacement, posterior fixation should be considered.
Axis, Cervical Vertebra ; Follow-Up Studies* ; Humans ; Odontoid Process*

PURPOSE: The accurate dosimerty of independent collimator equipped for 6MV and 15MV X-ray beam was investigated to search for the optimal correction factor. METHODS AND MATERIALS: The field size factors, beam quality and dose distribution were measured by using 6MV, 15MV X-ray. Field size factors were measured from 3X3cm2 to 35X35cm2 by using 0.6cc ion chamber (NE 2571) at Dmax. Beam qualities were measured at different field sizes, off-axis distances and depths. Isodose distributions at different off-axis distance using 10X10cm field were also investigated and compared with symmetric field. RESULTS: 1) Relative field size factors was different along lateral distance with maximum changes in 3.1% for 6MV and 5% for 15MV. But the field size factors of asymmetric fields were identical to the modified central-axis values in symmetric fileld, which corrected by off-axis ratio at Dmax.2) The HVL and PDD was decreased by increasing off-axis distance. PDD was also decreased by increasing depth For field size more than 5X5cm2 and depth less than 15cm, PDD of asymmetric field differs from that of symmetric one (0.5~2% for 6MV and 0.4~1.4% for 15MV).3) The measured isodose curves demonstrate divergence effects and reduced doses adjacent to the edge close to the flattening filter center was also observed. CONCLUSION: When asymmetric collimator is used, calcutation of MU must be corrected with off-axis and PDD with a caution of underdose in central axis.
Axis, Cervical Vertebra ; Jaw*

PURPOSE: The aim of the present study was to evaluate the accuracy of three techniques for correction of cast implant bars. MATERIALS AND METHODS: Thirty cast implant bars were fabricated on a metal master model. All cast implant bars were sectioned at 5 mm from the left gold cylinder using a disk of 0.3 mm thickness, and then each group of ten specimens was corrected by gas-air torch soldering, laser welding, and additional casting technique. Three dimensional evaluation including horizontal, vertical, and twisting measurements was based on measurement and comparison of (1) gap distances of the right abutment replica-gold cylinder interface at buccal, distal, lingual side, (2) changes of bar length, and (3) axis angle changes of the right gold cylinders at the step of the post-correction measurements on the three groups with a contact and non-contact coordinate measuring machine. One-way analysis of variance (ANOVA) and paired t-test were performed at the significance level of 5%. RESULTS: Gap distances of the cast implant bars after correction procedure showed no statistically significant difference among groups. Changes in bar length between pre-casting and post-correction measurement were statistically significance among groups. Axis angle changes of the right gold cylinders were not statistically significance among groups. CONCLUSION: There was no statistical significance among three techniques in horizontal, vertical and axial errors. But, gas-air torch soldering technique showed the most consistent and accurate trend in the correction of implant bar error. However, Laser welding technique, showed a large mean and standard deviation in vertical and twisting measurement and might be technique-sensitive method.
Axis, Cervical Vertebra ; Welding

No abstract available.
Axis, Cervical Vertebra*

STATEMENT OF PROBLEM: Main consideration was given to the stresses at the site of implant entry into the cortical bone at the alveolar crest. As a suspectible factor affecting the occurrence of stress concentrations, the contact angle between the implant and the alveolar crest bone was addressed. PURPOSE: The purpose of this study is to evaluate angles between the alveolar crest bone and the implant effect on the implant crestal area induced stresses using a finite element method. MATERIAL AND METHODS: Cylindrically shaped, standard size ITI implants entering into alveolar crest with four different contact angles of 0, 15, 30, and 45 deg. with the long axis of the implant were axisymmetrically modelled. Alterations of stresses around the implants were computed and compared at the cervical cortical bone. RESULTS AND CONCLUSION: The results demonstrated that regardless of the difference of the implant/alveolar crest bone contact angles, stress concentration occurred at the cervical bone and the angle differences led to insignificant variations in stress level.
Axis, Cervical Vertebra

No abstract available.
Axis, Cervical Vertebra*