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The relationship of the posterior aspects of the atlas and the axis were studied in 100 normal adult volunteers. The ratio of the height of the atlantal spinolaminar line to the atlantoaxial interspinous distance was found to be remarkably constant and was less than 2.0 in all men and women. This ratio should prove helpful in detecting hyperflexion injuries isolated to the atlantoaxial level.
The computed tomographie demonstration of congenital fusion of the anterior arch of the atlas with the axis is reported and compared with the normal anatomy.
Atlanto-axial rotatory subluxation (AARS) is an uncommon condition involving dislocation and abnormal fixation of the atlas on the axis. AARS is difficult to diagnose and if improperly treated it may lead to permanent neck deformity. We report a retrospective series of patients diagnosed with AARS seen during the last five years. The children presented with neck pain, head tilt, and reduction in neck mobility. In three of the cases the condition was secondary to cervical trauma and in the fourth it was associated with otitis (Grisel syndrome). The diagnosis was established by three-dimensional computerised tomography. In three cases, the atlanto-axial fixation was cured after cervical immobilisation and physiotherapy. A posterior cervical fusion was required in the remaining case. Early detection and intensive conservative treatment constitutes the mainstay of management of AARS. Surgery is reserved for cases with irreducible or recurrent subluxation.
Cranial settling is a condition in which erosive changes of the atlantal lateral masses result in downward telescoping of the atlas onto the axis body, anterior displacement of the atlantal posterior arch, and subsequent ventral and dorsal cervicomedullary compression. Cranial settling is described in conjunction with rheumatoid basilar invagination and atlanto-axial instability, possibly representing the most life-threatening abnormality associated with rheumatoid arthritis. The authors describe a case of symptomatic cranial settling in a nonrheumatoid patient with chronic, severe, spasmodic torticollis resulting in erosive changes in the occipito-atlanto-axial complex.
In seventeen cases of irreducible atlanto-axial rotatory subluxation (here called fixation), the striking features were the delay in diagnosis and the persistent clinical and roentgenographic deformities. All patients had torticollis and restricted, often painful neck motion, and seven young patients with long-standing deformity had flattening on one side of the face. The diagnosis was suggested by the plain roentgenograms and tomograms and confirmed by persistence of the deformity as demonstrated by cineroentgenography. Treatment included skull traction, followed by atlanto-axial arthrodesis if necessary. Of the thirteen patients treated by atlanto-axial arthrodesis, eleven had good results, one had a fair result, and one had not been followed for long enough to determine the result. Of the remaining four patients, one treated conservatively had not been followed for long enough to evaluate the result, two declined surgery, and one died while in traction as the result of cord transection produced by further rotation of the atlas on the axis despite the traction.
Over 2 years, 16 patients with a total of 23 lesions of the craniovertebral junction and the upper cervical spine were treated. Clinically important aspects of diagnosis and classification are outlined. The conditions treated included fractures of the occipital condyle and atlas, dens-axis, and hanged-man fractures. Standard operative treatment, which has to be modified in cases of combined injuries, is presented. Surgery is frequently indicated, especially in elderly and polytraumatized patients. In addition, 2 cases of atlanto-occipital dislocation are described: 1 of these patients survived for 5 days after early atlanto-occipital fusion.
A new method is described for reduction and successful treatment of false articulation of dens axis and neglected complicated transdens subluxation of the atlas to the back by means of skeletal traction applied to the bones of the skull with Ilizarov's apparatus in a 8-year-old boy.
Rheumatoid arthritis frequently contributes to instability of the upper cervical spine. Rotational instability of the upper cervical spine was evaluated in rheumatoid arthritis patients using biplanar x-ray photogrammetry. Three-dimensional cervical motion and the instantaneous axis of rotation of the atlas relative to the axis were evaluated in normal and rheumatoid arthritis patients during axial rotation in the horizontal plane. Anterior atlantoaxial subluxation did not increase during axial head rotation in either the atlantoaxial subluxation or the vertical subluxation groups, while the instantaneous axes of rotation were distributed posteriorly in the dens in the RA-normal group, but were widely scattered in the atlantoaxial subluxation group.
The stability of the atlantoaxial articulation depends fundamentally on the integrity of the odontoid process and the ligaments. Ligament stability mostly is maintained by two ligaments: the transverse ligament and the alar, apical ligaments. Failure of the transverse ligament can result in anterior translation of the atlas on the axis. The anteroposterior diameter of the ring of the atlas is approximately 3 cm. The spinal cord and the odontoid process are each approximately 1 cm in diameter, approximately 1/3 the diameter of the ring. According to Steel's rule of thirds, the remaining centimeter of free space allows for some degree of pathologic displacement. The current anatomic study showed that the space available for the spinal cord was limited. The sagittal diameter C1-C2 canal is 18.71 +/- 2.88 mm (excluding 10 mm thickness of the dens and 2.91 +/- 0.69 mm thickness of transverse ligament), with the spinal cord occupying 7.73 +/- 0.87 mm of the available space. Space available for spinal cord at the level of the atlas is 3.44 +/- 1.19 mm plus 1.01 +/- 0.20 mm space anterior to the cord (anterior epidural space) and 5.64 +/- 2.22 mm space posterior to the cord (posterior epidural space), which is approximately in agreement with the normal diameter by Steel's rule of thirds.
Bilateral override of the atlas on the axis is generally attributed to a traumatic disruption of the atlas ring. Few other conditions have been described previously in association with this finding. The morphologic features to be considered and the differential diagnosis are discussed, stressing the diagnostic value of the lateral view, and of both conventional and computed tomography.
STUDY DESIGN: Case report of spontaneous Fielding and Hawkins Type I atlantoaxial rotatory fixation in a 78-year-old man after hemiplegia and homonymous hemianopsia caused by cerebral infarction. OBJECTIVES: To describe a case of spontaneous atlantoaxial rotatory fixation in old age and review previous adult cases of atlantoaxial rotatory fixation without fracture. SUMMARY OF BACKGROUND DATA: Atlantoaxial rotatory fixation in adults is a relatively rare finding and is mainly caused by trauma. To the author's knowledge, there has been no previous report of spontaneous atlantoaxial rotatory fixation in old age. METHODS: The patient's head was fixed in a 40 degrees left-rotated position. Left hemiplegia and homonymous left-side hemianopsia developed due to cerebral infarction. Computed tomography of the cervical spine clearly showed rotatory fixation of the atlas on the axis. RESULTS: Successful reduction was obtained after 1 day of skull traction. CONCLUSIONS: It was hypothesized that repeated left-rotational stress due to homonymous hemianopsia loaded to the atlantoaxial joint caused abnormal laxity of the joint.
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