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PubMed1991

Traumatic atlantoaxial dislocation without fracture of the odontoid.

Four cases of atlantoaxial dislocation without fracture of the odontoid have now been reported in patients surviving significant trauma. Experience with these cases suggest the following: 1. Atlantoaxial dislocation is compatible with survival and minimal or no long-term neurologic effects. 2. Reduction of the dislocation by traction is possible and has not resulted in significant complications, but marked instability can be present. Close medical supervision and frequent radiographic evaluation is mandatory. During reduction, the weight and angle of traction applied is changed in each phase of reduction (distraction, realignment, release). After reduction, physician-controlled, gentle flexion-extension radiographs are used to assess stability. 3. Traction should be started with light weights, care being taken to avoid overdistraction. A maximum of 15 lb traction was required for reduction in the present case. 4. Posterior surgical fusion is usually necessary because of residual instability and/or incomplete reduction, as demonstrated by postreduction supervised, gentle flexion-extension radiographs and/or CT scan. 5. There may be a small number of patients who can be treated by immobilization alone if a completely stable, anatomic reduction is obtained with traction.

Adult↗
PubMed1991

Fusion of the upper cervical spine in children and adolescents. An analysis of 17 patients.

A retrospective review of 17 immature patients who underwent posterior spinal fusion of C1-C2 or C1-C3 was performed to establish the efficacy of the procedure, to determine the incidence of complications, and to identify those at high risk for complications. All had radiographic C1-C2 instability or dislocation. Etiologies included os odontoideum, fixed rotatory subluxation, atlantoaxial subluxation, type II dens fracture nonunion, and nonunion of a Hangman's fracture. Before surgery, 10 patients were neurologically intact, and seven had neurologic findings. Associated diagnosis included Down's syndrome in three and Ehler-Danhlos in one. Follow-up averaged 25 months. One neurologically intact patient had a C2 radiculopathy that resolved by 1 year. Three patients with Down's syndrome had complications: one with a preoperative Brown-Sequard syndrome had transient worsening in the immediate postoperative period, one with a preoperative myelopathy developed a late recurrence of a severe myelopathy that required odontectomy, and another sustained an intraoperative spinal cord contusion followed by postoperative quadriplegia and death due to respiratory failure. Of seven reporting neurologic symptoms before surgery, two had residual deficit in the late postoperative period. These two represented preventable technical errors. There were two nonunions, one of which required occiput to C2 fusion. In general, posterior spinal fusion of the upper cervical spine was found to be a reliable, safe, and predictable procedure, but extra caution should be employed when considering arthrodesis in patients with ongoing spinal cord compression, fixed dislocations, and inherited ligamentous laxity.

Adolescent↗
PubMed1991

Complications of fusion to the upper cervical spine.

Forty-seven operations for posterior fusion of the upper cervical spine were reviewed for complications. Alarmingly, only 11 patients had an entirely uncomplicated course. Most complications were minor, but there were four nonunions, one requiring reoperation. Although seven patients had increased neurologic deficits after surgery, only one was permanent. There was one death due to technical error. Patients with significant instability, myelopathy, prior failed fusions, or unreducible dislocations are at high risk for perioperative neurologic complications.

Adult↗
PubMed1991

Superior facet fractures of the axis vertebra.

Nine cases of superior facet fractures of the axis vertebra are reported. In seven cases, there were associated odontoid fractures. These fractures can occur in a coronal or sagittal direction, shearing off the anterior or lateral plateau of the facet. In addition, the lateral mass of the atlas may sublux into the depressed facet fracture. The fracture complex should be well documented with conventional radiography and tomography. Computerized tomographic scanning has been found to be particularly helpful in diagnosing these fractures and other injuries about the axis or atlas. Patients with undisplaced or well-reduced facet fractures can be managed satisfactorily by conservative means, but surgery (posterior atlantoaxial fusion) should be considered for unreduced fractures in order to prevent long-term instability, nonunion, malunion, and degenerative arthritis.

Axis, Cervical Vertebra↗
PubMed1991

Posterior atlantoaxial arthrodesis. A simplified method.

A simplified method of posterior atlantoaxial arthrodesis allowing immediate stabilization and mobilization is described. This method of fixation has been used since 1984 in 33 cases, with the indications being nonunion of odontoid peg fractures, atlantoaxial dislocation, and other traumatic conditions about the axis. A solid fusion was noted in all 33 patients by 3 months postsurgery, and the complication rate was minimal. This method of atlantoaxial arthrodesis is simple, allows immediate mobilization, controls rotation and lateral bending, and is inexpensive.

Adult↗
PubMed1991

Cineradiographic motion analysis of atlantoaxial instability in os odontoideum.

Cineradiography was used to study six patients with os odontoideum. Atlantoaxial kinematics was analyzed with the relative motion of the atlas on the axis. In all cases, the tracing of the anterior arch was straight in the sagittal plane, whereas the posterior arch moved in two different configurations: straight and S-shaped. In cases of S-shaped configurations, the anterior translation occurred in the neutral position. Such translation could threaten the stability of the atlantoaxial complex fixed with posterior wiring because circumferential wires allow the laminas to rotate in the sagittal direction. In patients with os odontoideum, pathomechanics of the atlantoaxial joint should be examined with cineradiography in order biomechanically to determine the soundest fixation.

Adolescent↗
PubMed1991

Screw fixation of odontoid fractures and nonunions.

Surgical treatment of odontoid fractures has usually been carried out by C1-2 arthrodesis rather than by fracture fixation. An alternative treatment of compression screw fixation was used to treat selected acute odontoid fractures and nonunions. Ten patients were operated on. A variety of lag-screw types were used to compress and secure the fracture. Screw placement was considered excellent in five cases; in four, the screw tip protruded through the posterosuperior cortex of the dens by 1-3 mm. One patient died as a result of multiple injuries 2 days after surgery. In all other cases, including four cases of odontoid pseudarthroses, the fractures achieved solid union. It was concluded that screw fixation can be used for the successful treatment of selected odontoid fractures and nonunions.

Adult↗
PubMed1991

Failure of halo vest to prevent in vivo motion in patients with injured cervical spines.

Forty-two patients with cervical spine injuries immobilized in halo vests were studied prospectively to determine in vivo vertebral segmental motion. Lateral radiographs taken in the supine and upright positions within 5 days of injury demonstrated intervertebral motion. At noninjured levels, the positional change accounted for an average 3.9 degrees of angulation with the greatest motion occurring between the occiput and C1 (8.0 degrees). At the injured levels, sagittal plane angulation averaged 7.0 degrees and translation averaged 1.7 mm between the two positions. Fracture site motion did not correlate with either the fracture type or the injury level. Fracture site motion greater than 3 degrees of angulation or 1 mm of translation was observed at 35 (77%) of 45 injured levels. When treating patients who have unstable cervical injuries with halo vests, supine and upright radiographs should be obtained. If excessive motion is present, alternative methods of treatment should be considered.

Adolescent↗
PubMed1992

Computerized tomography in persons with Down syndrome and atlantoaxial instability.

Atlantoaxial instability has been reported to occur in 9-31% of persons with Down syndrome. The authors studied a subsample of patients with this chromosomal disorder who had both routine roentgenograms and computerized tomographic examinations. Computerized tomography revealed numerous skeletal anomalies of the C1-C2 region as well as spinal cord compression that were not visualized on plain roentgenograms. In addition, an apparent discrepancy of the atlanto-dens interval measurements between the two procedures was noted. The measurements of the plain roentgenograms were significantly greater than those obtained by computerized tomography, which is due to the magnification factor in plain roentgenograms.

Atlanto-Axial Joint↗
PubMed1992

Morphology of the dens. A quantitative study.

Morphometric studies of the dens of the second cervical vertebra were performed on a sample of one hundred twenty bones from the Hamann-Todd Collection. Data were collected on the longitudinal and transverse dimensions of the dens, as well as the size of the dens relative to the centrum of C2. Relationships of dens dimensions to body size and sexual dimorphism were evaluated. In both longitudinal and transverse mean dimensions, the dens in males was slightly, but significantly larger (5-10%) than in females. The relative distributions of dens dimensions were consistently skewed toward the higher values in males and the lower values in females. Body height or weight were not significantly correlated with dens dimensions, and were therefore poor predictors of the size of the dens. Implications for screw fixation of fractures of the dens are discussed.

Adult↗
PubMed1993

Surgically related upper cervical spine canal anatomy in children.

MRI studies of the upper spines of 121 children were evaluated to precisely define the sagittal anatomy at C1 in the pediatric population. The diameters of the spinal cord, bony canal, space available for the cord (SAC), dens+atlanto-dens interval (ADI), and "free" space were measured. The results demonstrate an accelerated growth in the C1 canal, dens + ADI, and SAC during the first four years after birth. Steel's rule of thirds was shown to roughly hold true throughout childhood. Neonates have an average SAC diameter of 12.4 mm, a value less than the 13 mm dimension commonly used to define relative stenosis in children.

Adolescent↗
PubMed1993

The trabecular anatomy of the axis.

This article describes the internal anatomy of C2. Although some C2 specimens showed a high density of trabecular bone throughout, a feature noted in all specimens was a void or very hypodense area of bone located immediately beneath the dens. The observed nonuniform distribution of trabecular bone within the axis is considered to have an effect on internal fixation of this bone. The good cancellous bone quality consistently observed in the lateral masses and beneath the facets, as well as near the bony end plates, suggests that these areas may be reasonable sites for the insertion of internal fixation devices. The hypodense area observed in the upper portion of C2 would suggest that fixation devices inserted through this area may obtain relatively poor purchase and may be prone to cut-through failure.

Axis, Cervical Vertebra↗
PubMed1993

Cervical spine surgery in rheumatoid arthritis: improvement of neurologic deficit after cervical spine fusion.

Ninety of 110 consecutive patients with rheumatoid deformities of the cervical spine surgically treated had associated neurologic deficits. Fifty-five patients had atlantoaxial subluxation. In this group, there were 16 Ranawat Class I patients (normal), 21 Class II (weakness, hyperreflexia, dysesthesia), 13 Class IIIA (paresis and long-tract findings but can ambulate), and five Class IIIB (quadriparesis and inability to ambulate). After C1-C2 stabilization, 94.8% improved at least one class. Twenty-two patients had AAS-SMO (atlanto-axial subluxation and superior migration of the odontoid) only one before surgery was Class I, five Class II, eight Class IIIA, and eight Class IIIB. Seventy-six percent improved at least one class after surgery. Nineteen had isolated subaxial subluxation (SAS). Three were Class I, two Class II, nine Class IIIA, and five were Class IIIB. After surgery, 94% improved at least one class, and all were ambulating. Fourteen had combined AAS-SMO-SAS deformities. There were no Class I patients, only four Class II, four Class IIIA, and six Class IIIB. After surgery, 71% improved. The four deaths that occurred in the immediate postoperative period were Class IIIB. Fifteen patients had worsening or recurrence of their symptoms. Thirteen of these were related to the later development of subaxial subluxation. Neurologic symptoms and recovery were related to severity of the deformity. Those with SMO had greater neurologic deficits and worse results. In general, neurologic recovery is encouraging even in the IIIB patient. Earlier surgery should be done, however, particularly before SMO develops, if possible.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Os odontoideum with vertebral artery occlusion.

A 21-year-old man developed signs of brainstem damage after being injured while playing rugby. Cervical x-ray films showed os odontoideum, and angiography revealed persistent occlusion of the right vertebral artery at the level of the second cervical spine. These findings indicated that atlantoaxial dislocation caused by os odontoideum may have induced vertebral artery occlusion, leading to brainstem infarction.

Adult↗
PubMed1994

Posterior atlantoaxial fusion. A new internal fixation device.

STUDY DESIGN: Biomechanical and clinical testing of an atlantoaxial posterior fixation device. OBJECTIVES: The authors tested an internal fixation device to maintain the atlas and axis in an anatomic relationship while fusion occurs. The device should also facilitate intraoperative reduction of any residual anterior atlantoaxial subluxation. The device should allow the use of cancellous rather than cortical bone graft. SUMMARY OF BACKGROUND DATA: Previous techniques of atlantoaxial fusion were not universally successful, and the quality of reduction was assessed infrequently. METHODS: Biomechanical testing of the fixator and clinical use in two "problem" patients requiring atlantoaxial fusion. RESULTS: Biomechanical testing indicated the device should be successful. Clinical testing was successful. CONCLUSION: The new fixator facilitates posterior atlantoaxial fusion in an anatomical position.

Atlanto-Axial Joint↗