Lateral atlantoaxial arthrodesis.
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Adult↗
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The clinical biomechanics of the occipitoatlantoaxial complex.
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Atlanto-Occipital Joint↗
[Clinical picture and diagnosis of craniovertebral anomalies].
It has been found that anomalies of the craniovertebral region are characterized by polymorph degenerative changes in the bones. This regularity appeared to be especially typical for Arnold-Chiari's anomaly, the fact, that gives one ground to expand the scope of the notion and to specify some variants of that anomaly. Complicated anomalies manifest themselves in the form of three clinical syndromes, that is, the cerebellobulbar, the syringomyelitic and the pyramid ones. In cases of acute progressing of those syndromes surgical intervention is indicated, while in chronically developing syndromes restorative and rehabilitation treatment can be given.
Adolescent↗
Halifax interlaminar clamps for posterior atlanto-axial arthrodesis with spinal fusion by "H" bone+graft.
The use of Halifax interlaminar clamps in posterior arthrodesis for atlanto-axial instabilities has recently been reported. The four Anderson II fractures submitted were surgically treated by posterior arthrodesis with Halifax clamps and bilateral "H" shaped bone-grafts obtained from the iliac crest. Only in the first case--initially treated without fusion--a review of the system became necessary due to the loosening of one clamp. No post-operative neurological complications appeared and non malunion or nonunion occurred at follow-up. Posterior arthrodesis with Halifax clamps does not involve any complication connected with the use of metal wire and the association of posterior fusion by lateral "H" shaped bone grafts ensures a stable and physiological reduction of dens fractures and atlanto-axial luxations/subluxations often associated.
Adult↗
Lesions of the craniovertebral junction.
There has been a renewed interest in the normal and pathologic lesions of the CVJ with the growth of MR imaging. A host of pathologies, both congenital and acquired, may manifest at the CVJ. Basilar invagination and basilar impression and their impact on the CMJ are readily diagnosed using a variety of noninvasive imaging modalities. Evaluation of the CVJ on cranial and cervical MR examinations should be a routine part of image interpretation.
Atlanto-Axial Joint↗
Rheumatoid atlantoaxial subluxation.
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Arthritis, Rheumatoid↗
Radiological and anatomical evaluation of the atlantoaxial transarticular screw fixation technique.
Sixty-one patients treated with C1-2 transarticular screw fixation for spinal instability participated in a detailed clinical and radiological study to determine outcome and clarify potential hazards. The most common condition was rheumatoid arthritis (37 patients) followed by traumatic instability (15 patients). Twenty-one of these patients (one-third) underwent either surgical revision for a previously failed posterior fusion technique or a combined anteroposterior procedure. Eleven patients underwent transoral odontoidectomy and excision of the arch of C-1 prior to posterior surgery. No patient died, but there were five vertebral artery (VA) injuries and one temporary cranial nerve palsy. Screw malposition (14% of placements) was comparable to another large series reported by Grob, et al. There were five broken screws, and all were associated with incorrect placement. Anatomical measurements were made on 25 axis bones. In 20% the VA groove on one side was large enough to reduce the width of the C-2 pedicle, thus preventing the safe passage of a 3.5-mm diameter screw. In addition to the obvious dangers in patients with damaged or deficient atlantoaxial lateral mass, the following risk factors were identified in this series: 1) incomplete reduction prior to screw placement, accounting for two-thirds of screw complications and all five VA injuries; 2) previous transoral surgery with removal of the anterior tubercle or the arch of the atlas, thus obliterating an important fluoroscopic landmark; and 3) failure to appreciate the size of the VA in the axis pedicle and lateral mass. A low trajectory with screw placement below the atlas tubercle was found in patients with VA laceration. The technique that was associated with an 87% fusion rate requires detailed computerized tomography scanning prior to surgery, very careful attention to local anatomy, and nearly complete atlantoaxial reduction during surgery.
Adolescent↗
Craniocervical junction as a focus for craniofacial growth studies.
The craniocervical junction is a highly specialized unit simultaneously supporting head during movements in all planes and protecting the spinal cord. Anatomically, it includes an atlantoaxial complex, part of which embryonically arises from the occipital region of the skull. This review deals with the gross anatomy, kinematics, and growth reactions associated with functional alteration in this complex. Particular attention is paid to the atlas, the connecting element between the head and the vertebral column proper. From several studies it is concluded that the horizontal growth of the atlas is regulated by synchondroseal growth, whereas the vertical growth is determined by appositional growth. Some vertebral anomalies and concomitant anomalies of the cranial base are reported, to point out the ontogenetic integration between the skull base and the craniocervical junction. The high frequencies of atlantal posterior arch deficiency in cleft palate patients have led to speculations about common etiologic factors in these conditions.
Atlanto-Axial Joint↗
A method for classification of the posterior atlanto-axial subluxation.
Atlanto-axial subluxation and dislocation in rheumatoid arthritis is a multidirectional abnormality. The most common subluxations take place anteriorly, vertically or laterally. Posterior atlanto-axial subluxations are rare. The distance between a line tangential to the anterior aspect of the axis (C2) and the most posterior aspect of the anterior arch of the atlas (C1) could be used to measure the displacement in posterior atlanto-axial subluxation. Routine measurement of this distance could give us a better idea of the frequency of this type of affection in rheumatoid arthritis of the cervical spine. Serial measurements might be used to estimate the progression of the disease.
Arthritis, Rheumatoid↗
Development of a high resolution three-dimensional surgical atlas of the murine head for strains 129S1/SvImJ and C57Bl/6J using magnetic resonance imaging and micro-computed tomography.
The mouse has emerged as a major experimental model system for examining the functional properties of the mammalian CNS; both during development and following CNS injury. Histologic procedures currently used to determine the relative position of structures within the CNS are presently limited in their ability to take full advantage of this system for surgical and morphometric procedures. We present here the first three-dimensional interactive digital atlas of the murine brain and skull for two genetically important strains of mice; 129S1/SvImJ and C57Bl/6J. The final resolution of these digital atlases is 54 micro m(3). These representations of the murine brain and skull, in conjunction with our development of a new, more dynamic master coordinate system, provide improved accuracy with respect to targeting CNS structures during surgery compared with previous systems. The interactive three-dimensional nature of these atlases also provide users with stereotactic information necessary to perform accurate "off-axis" surgical procedures, as is commonly required for experiments such as in vivo micro-electroporation. In addition, three-dimensional analysis of the brain and skull shape in C57Bl, 129Sv, CD1, and additional murine strains, suggests that a stereotactic coordinate system based upon the lambda and rostral confluence of the sinuses at the sagittal midline, provides improved accuracy compared with the traditional lambda-bregma landmark system. These findings demonstrate the utility of developing highly accurate and robust three-dimensional representations of the murine brain and skull, in which experimental outputs can be directly compared using a unified coordinate system. The aim of these studies is to enhance comparative morphometric analyses and stereotactic surgical procedures in mice.
Animals↗
[Functional roentgen diagnosis of the upper cervical spine].
For evaluation of the function of the upper cervical spine, especially assessment of the range of motion, functional X-rays films are useful in addition to the clinical examination. For the diagnosis of segmental instability, passive motion should be induced in order to obtain the full range. If anterior instability of the upper cervical spine is suspected, flexion-extension X-rays in the lateral view are appropriate. If a lesion of the alar ligaments is suspected, then lateral flexion X-rays films should be taken. In the normal situation, the atlas glides in the direction of bending, coupled by forced rotation of the axis. In cases with rotatory instability of the upper cervical spine, functional computed tomography should be performed. Atlantoaxial rotation of more than 52 degrees should be considered pathological as a result of a lesion of the alar ligaments. For examination of the relationship between the spinal cord and bony structures or inflammatory tissue in patients with rheumatoid arthritis, functional MRIs are helpful. Not only the exact diameter of the spinal canal can be measured during flexion and extension, but the degree of basilar impression or cranial migration of the axis can also be assessed. Optimal use of functional X-ray diagnostics, including functional the CT and MRI, is not only helpful for clinical diagnoses, but also for the planning of surgical procedures.
Cervical Vertebrae↗
[Atlanto-axial, Atlanto-occipital dislocations, developmental cervical canal stenosis in the Ehlers-Danlos syndrome (author's transl)].
Clinical, biological, histopathological and laboratory data are reported on a 13-year-old male with atlanto-axial, atlanto-occipital hypermobilities, cervical canal stenosis, hypoplastic atlas and hypoplastic first rib in the Ehlers-Danlos syndrome. He developed frequent attacks of sudden tetraplegia or tetraparesis and numbness below C2 due to trivial neck injuries. Examination revealed marked hypermobilities of all joints the cutis elastica (Fig. 1), spastic tetraparesis and fasciculation of the tongue. Occipito-atlantal hypermobility measured by Wiesel and Rhothmans' method revealed 5 mm horizontal translation (Fig. 2). Anterior and lateral dislocations of atlanto-axial joints were marked due to laxicity of the joint. Posterior decompression of C1, laminotomy of C2,3, occipito-C2 fixation with autogenous iliac "board (3 X 6 cm, rectangular board) graft" yielded favorable results with 15 months follow-up. To our knowledge, this is the first patient reported with this unusual combinations.
Adolescent↗
Os odontoideum with bipartite atlas and segmental instability: a case report.
We report on the case of a 15-year-old adolescent who presented with a transient paraplegia and hyposensibility of the upper extremities after sustaining a minor hyperflexion trauma to the cervical spine. Neuroimaging studies revealed atlantoaxial dislocation and ventral compression of the rostral spinal cord with increased cord signal at C1/C2 levels caused by an os odontoideum, as well as anterior and posterior arch defects of the atlas. The patient underwent closed reduction and posterior atlantoaxial fusion. We describe the association of an acquired instability secondary to an os odontoideum with an anteroposterior spondyloschisis of the atlas and its functional result after 12 months. The rare coincidence of both lesions indicates a multiple malformation of the upper cervical spine and supports the theory of an embryologic genesis of os odontoideum.
Adolescent↗
Functional-adaptive anatomy of the axial skeleton of some extant marsupials and the paleobiology of the paleocene marsupials Mayulestes ferox and Pucadelphys andinus.
In this study, the axial skeletons of two Early Paleocene marsupials, Mayulestes ferox and Pucadelphys andinus, were analyzed functionally and compared to that of six South American and three Australian species of extant marsupials. In the case of the South American opossums, myological data of the epaxial musculature were collected and analyzed and osteological-myological associations were related to locomotor behavior. Various features of the vertebral column that relate to diet or to locomotor or postural patterns were pointed out. These features include: the craniocaudal development of the neural process of the axis; the position of the anticlinal vertebra; the morphology of the neural processes of the thoracolumbar vertebrae (orientation, length, and craniocaudal width); the length, orientation, and curvature of the transverse processes of the lumbar vertebrae; and the length and robustness of the caudal vertebrae. In both fossil forms the vertebral column is mobile and allows a great range of flexion and extension of the spine, more so than in most of the living didelphids. It is emphasized here that the analysis of the axial skeleton complements and improves the conclusions provided by the forelimb and hindlimb analyses. It is proposed that Mayulestes and Pucadelphys represent an ancestral morphotype suggesting that the generalized type of locomotion of Paleocene marsupials was partly terrestrial with some climbing ability.
Adaptation, Physiological↗
Craniocervical malformations.
This short survey summarises the important craniocervical dysplasias, the malformations accompanying primary neuroectodermal and secondary lesions of the neural structures and their coverings, and complex malformations. The interpretation, classification and the identification of the static and/or dynamic biomechanical pathogenesis is a prerequisite for the correct diagnosis and for assessing the indications for and the choice of any operation to be adopted.
Axis, Cervical Vertebra↗
Halo traction in basilar invagination: technical case report.
BACKGROUND: In the management of basilar invagination, traction therapy may help by pulling down the odontoid process away from the brain stem that may result in clinical and radiological improvement. We aimed to discuss the role of the halo vest apparatus traction on the reduction of severe anterior compression pathologies in basilar invagination. CASE DESCRIPTION: We describe a simple and safe cervical traction method by the halo vest apparatus that is followed by rigid posterior occipitocervical fixation and foramen magnum decompression in a patient who presented with basilar invagination and symptoms of severe brain stem compression. An MR-suitable halo vest apparatus was used for reduction of the deformity. The reduction of the basilar invagination was achieved gradually by distracting the halo crown in stages. CONCLUSION: The halo vest apparatus can be safely used in complex craniocervical junction anomalies. An effective cervical traction can be performed in basilar invagination, and reduction of the deformity may be achieved without the risk of overdistraction. In some cases, even partial reduction of the deformity may facilitate brain stem and spinal cord relief without any need of posterior decompression. Patients may benefit from ambulatory functions because bed rest is eliminated in this procedure. Neurovascular structures and the degree of the reduction can be observed on MRIs when an MR-suitable device is used.
Atlanto-Axial Joint↗
Stereotaxic atlas of the telencephalon of the weakly electric fish Gymnotus carapo.
A restraining box for the head and body of the electric fish Gymnotus carapo was constructed and coupled to a micromanipulator, permitting us to prepare an atlas of the telencephalon with stereotaxic parameters. A photograph and a schematic drawing of an animal's head is presented, showing two skin electroreceptors that were used as external landmarks. A sagittal section of the telencephalic structure is also presented, whose vertical bars indicate the frontal planes that compose the atlas. The frontal planes of the atlas consist of serial sections spaced 600 or 500 microns apart in the rostrocaudal axis. Sections mapped with acetylcholinesterase are shown, intercalated with Nissl-stained sections. The acetylcholinesterase sections proved to be useful for the delimitation of certain nuclei and for the exact localization of small fissures and fiber tracts. A brief description of major cytoarchitectural subdivision and connections of the telencephalon is provided.
Acetylcholinesterase↗