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At least 253 records · Page 14Linked to original sources

PubMed2006

[Reliability of direct probing isthmus of axial vertebrae to defining the screw path in atlas during Magerl technique].

OBJECTIVE: To evaluate the accuracy and reliability of atlantoaxial transarticular screw insertion (Magerl's technique) in atlas under lateral fluoroscopic monitoring without anteroposterior view. METHOD: Seventy-five consecutive patients with atlantoaxial instability, 48 males and 27 females, aged 35.1, were treated by Magerl's technique. The screw path in atlas was achieved by direct probing the isthmus of axial vertebrae then identifying its position through the atlantoaxial joint correlation. Postoperative transoral X ray and CT film were used for analysis of the position of the 150 screws in the mass of atlas. Three areas were delimitated in and around the lateral mass of atlas: area A (inside the joint face), area: B (outside the joint face but still in lateral mass), and area C area (outside the lateral mass) so as to analyze the location of screws. RESULTS: Among the 150 screws 139 (92.7%) were located in area A, 8 in area B(1) and 3 in area B(2) (7.3%), and none in area C. All cases got atlantoaxial union 3 months after operation. CONCLUSION: The method of "direct probing" is reliable for identifying the path of screw in atlas.

Adolescent↗

PubMed2000

Quantitative anatomy of the lateral masses of the atlas and axis vertebrae.

The study was carried out to determine the safe site of entry and the appropriate trajectory of the screw implantation in the lateral masses of atlas (Cl) and axis (C2) during their fixation using the plate and screw technique. Fifty dried specimens of atlas and axis vertebrae were studied. Various dimensions of the lateral masses were quantitatively measured, laying stress on their relationship with the vertebral artery foramen. As the vertebral artery foramen was present entirely in the transverse process in all specimens, screw implantation in the facet of atlas was relatively safe. Best direction of screw implantation in the facet of atlas was observed to be 15 degrees medial to sagittal plane and 15 degrees superior to axial plane. It should be implanted from the middle of the posterior surface of facet. Vertebral artery foramen formed a deep groove in the undersurface of a majority of superior facets of axis. In 15% facets, vertebral artery foramen occupied the entire undersurface of the superior facet. Safe angle for screw implantation in the facet of axis through its pedicle was seen to be 40 degrees medial to sagittal plane and 20 degrees superior to axial plane. Safe site of screw entry in the axis was superior and medial third of the posterior surface of the pedicle. Quality of cancellous bone in the lateral masses in the proposed trajectory of screw in Cl and C2 was good, providing an excellent purchase of the screw.

Axis, Cervical Vertebra↗

PubMed1999

Shear fracture through the body of the axis vertebra.

STUDY DESIGN: Three cases of a previously undescribed body fracture of the axis vertebra are presented. OBJECTIVES: To describe the radiographic features of the fracture are described, and to point out the differences to other axis body fractures regarding the mechanism of injury, stability, and treatment. SUMMARY OF BACKGROUND DATA: Fractures involving the odontoid process usually are caused by indirect forces, and they are considered unstable injuries. Anderson and D'Alonzo Type III odontoid fractures usually are hyperflexion injuries. Superior articular process fractures with or without associated odontoid peg fractures are caused by lateral hyperflexion injuries. METHODS: Three cases of body fractures of the axis vertebra are described. These fractures occur in an oblique plane shearing off in one piece the odontoid process together with one of the superior articular processes. The fragment displaces anterocaudally, and the odontoid process tilts toward the affected side. RESULTS: All fractures were managed nonsurgically. The two displaced fractures did not reduce in traction, and they had united in the displaced position after the 12 weeks of halo treatment. One patient reported only minor problems, but showed radiologic evidence of facet joint arthritis at 20 months. The second patient was lost to follow-up after discontinuation of halo treatment at 12 weeks. The only undisplaced fracture was managed in a halo body jacket for 10 weeks. The patient was pain free and had regained a full range of movement at 7 months. CONCLUSIONS: The presumed mechanism of injury in the described fracture is one of asymmetrical axial compression. The fracture can be managed safely in a halo jacket.

Adolescent↗

PubMed1997

Unilateral posterior atlantoaxial transarticular screw fixation.

Bilateral posterior C 1-2 transfacet screw placement with associated posterior bone graft wiring is the accepted treatment for patients with atlantoaxial instability. This technique was modified to treat 19 patients with atlantoaxial instability and unilateral anomalies that prevented placement of a screw across the C1-2 facet. In these cases, a single contralateral transarticular screw was placed in conjunction with interspinous bone graft wiring to avoid neural or vertebral artery injury and to provide C1-2 stability. Postoperatively, all 19 patients were placed in Philadelphia collars (mean immobilization 8 weeks, range 6-12 weeks). Unilateral C1-2 facet screw fixation was needed for the following reasons: a high-riding transverse foramen of the C-2 vertebra present in 13 patients (left side in eight, right side in five), poor screw purchase in two (left side in both), screw malposition in one (left side), severe degenerative arthritis in one (right side), neurofibroma in one (right side), and fracture of the C-1 lateral mass in one (left side). Six weeks postsurgery, one patient presented with a broken screw and required occipitocervical fusion with a Steinmann pin and wire cable from the occiput to C-3 to achieve solid fusion. Solid fusions were achieved in the other 18 patients (mean follow-up period 31 months, range 14-54 months); there was no delayed screw breakage, wire breakage, or spinal instability. There were no operative or postoperative neurological or vascular complications. The authors' experience demonstrates that unilateral C1-2 facet screw fixation with interspinous bone graft wiring is an excellent alternative in the treatment of atlantoaxial instability when bilateral screw fixation is contraindicated.

Adult↗

PubMed1998

The effects of x-axis vertebral translation on projected y-axis vertebral rotation.

BACKGROUND: Few studies have quantified the projection/distortion errors that occur in anteroposterior (AP) radiographs. OBJECTIVES: To quantify the projection/distortion errors on AP radiographs caused by lateral translation of the vertebrae. To demonstrate the effect of vertebral shape on projection errors. STUDY DESIGN: Three models of increasing complexity were constructed to document the distortion. Model 1 consisted of three metal pins embedded in a piece of metal tubing that was X-rayed in three positions. Model 2, a simple model of the X-ray beam mounted on a wooden platform, allowed for translation of a vertebral model in a simulated X-ray beam and the measurement of projected points of contact between the model and rays of the simulated beam. Model 3 is a computer simulation of the X-ray beam in which a vertebral model was translated laterally to varying locations. The projected points of contact between the simulated rays and the vertebral body margins and lamina junction were measured. Model 3 also showed that vertebral body shape has a large effect on the projected axial rotation. Two other simple models were created and discussed in relation to shape-dependent projection errors. RESULTS: X-axis translation results in projected y-axis rotation. Increasing magnitudes of x-axis vertebral translation results in increasing magnitudes of projected y-axis vertebral rotation. The projected rotation is also influenced by vertebral shape. CONCLUSION: We have shown that three-dimensional lateral translation projects as axial rotation on the AP radiograph. Projection error is largely influenced by the shape of the object and by the increasing obliquity of the rays of the X-ray beam. This would seemingly create confusion and invalidate spinal listings of vertebral position obtained from the AP radiographic image.

Axis, Cervical Vertebra↗

PubMed2000

Anatomical evaluation of the groove for the vertebral artery in the axis vertebrae for atlanto-axial transarticular screw fixation technique.

Anatomical measurements were studied on 40 dry axis vertebrae to determine the suitability of the groove for the vertebral artery for atlanto-axial transarticular screw fixation technique. We measured 13 parameters including three angular and 10 linear dimensions related to the groove of the vertebral artery, pedicle, and pars interarticularis and evaluated 80 measurements for each parameter. All measurements were done after placing a Kischner guide wire through the pedicle. We found that differences between measurements on the left and right sides of each vertebra were nonsignificant. In spite of the variability in measurements such as height, width, and median angle of the pedicle, the decline angle for instrumentation, the depth of the groove for the vertebral artery, and the internal height of the pars interarticularis, all of these had good symmetry. However, there were statistically significant differences between the sides in measurements for both the width (P=0.05) and the angle (P<0.02) of the pedicle allowing instrumentation and they did not show good symmetry. The risk of vertebral artery injury was found to be 22.5% per specimen, or 16.25% per screw inserted because the internal height of the pars interarticularis at point of fixation was </= 2.1 mm. In addition, we found that the pedicle width allowing instrumentation was not suitable in 12.5% of screws inserted because their values were </= 6 mm. When the width of the pedicle for instrumentation and the internal height of the pars interarticularis were both evaluated together, we also found that this technique would be extremely dangerous in 7.5% of specimens. In conclusion, the internal height of the pars interarticularis and the width of the pedicle for instrumentation should be evaluated together in thin CT sections preoperatively, because of the risk of vertebral artery injury in patients upon which atlanto-axial transarticular screw fixation is to be performed.

Atlanto-Axial Joint↗

PubMed1994

Absence of symmetry in superior articular facets on the first cervical vertebra in humans: implications for diagnosis and treatment.

OBJECTIVE: Little attention has been given to the craniovertebral articulations. Specifically, gross observations of variations of the superior articular facets on the atlas have not been described with respect to static and motion palpation findings. This study describes the anatomical variations of these facets and the clinical implications associated with asymmetrical structure. DESIGN: The superior articular facets of thirty human first cervical vertebrae were chosen for this study because the atlas constitutes the middle of the upper cervical complex and the atlanto-occipital joint contributes greatly to head movements. SETTING: The basic science research department of Logan College of Chiropractic, St. Louis, Missouri. SPECIMEN POPULATION: All available previously dissected anatomy laboratory and library specimens (30) were used in this study. All of the specimens were dry with intact facet surfaces and no regard was given to age, gender, or race. INTERVENTIONS: The atlases were studied out of situ and all soft tissue was removed so that the bony articular surfaces could be clearly viewed and photographed. MAIN OUTCOME MEASURES: Palpation and unaided visual examination were performed on 30 atlases. The shape, size, angle, texture, border, and number of superior articular facets on each atlas were recorded to determine symmetry. RESULTS: The classically described kidney-shaped facet was in fact an infrequent finding. Upon comparison of right and left sides, none (0%) of the facets were mirror images of symmetry, while 19 of the atlases (63%) had grossly asymmetrical facets, and 11 of 30 atlases (37%) had facets which were only slightly asymmetrical in regard to shape, border, depth and angle. Furthermore, 7 of the 19 grossly asymmetrical atlases (37%) had three or four separate superior articular facets. Three atlases had two facets on the left and one on the right, while two atlases had two facets on the right with a single facet on the left, and two atlases had four superior facets (two on each side). CONCLUSION: The validity of vertebral joint assessment based on the assumption of facet symmetry is challenged, impugning certain chiropractic theories and/or techniques which rely on symmetry as being "normal." To achieve symmetrical function, the anatomical structure must be symmetrical. Since true structural symmetry does not exist, true symmetry of segmental movement may not be possible.

Atlanto-Axial Joint↗

PubMed1999

Peroperative determination of safe superior transarticular screw trajectory through the lateral mass.

STUDY DESIGN: Computerized anatomic reconstruction of the dry axis vertebra was performed to determine radiologic guidelines for safe superior transarticular screw trajectory. OBJECTIVES: To reconstruct the transarticular screw trajectory, using computer-aided design techniques, and develop a technique that provides real-time intraoperative guidance during screw placement. SUMMARY OF BACKGROUND DATA: A recent osteometric study of 50 dry specimens of the axis noted significant vertebral artery groove anomalies in 22% of specimens. There are presently no anatomic or radiologic guidelines to help surgeons avoid an enlarged vertebral groove, despite the fact that a safe screw trajectory through the lateral mass is primarily dependent on the its depth and the internal height of the lateral mass. METHODS: Using computer-aided design techniques, we re-analyzed the vertebral grooves of 50 dry specimens and mapped minimum and corrected safe superior trajectories for any given depth of this groove. This knowledge was extrapolated to spiral computed tomographic scan data, which was used to develop the clinical method for safe superior trajectory. Real-time fluoroscopy was used to apply the method intraoperatively. RESULTS: Internal height less than 2.1 mm or values less than 0.85 for the ratio of the mean internal height over the mean vertebral groove depth would result in unacceptable risk to vertebral artery injury and improper screw purchase. With every 0.5-mm increase in groove depth, the angle of trajectory increases by 1 degree at a pedicle length of 30 mm. There is an inverse linear relation between the superior angle of trajectory and the pedicle length (2 degrees = 5 +/- 0.5 mm). Screw diameter-dependent trajectory correction is required (3.5 mm = 7 degrees). CONCLUSIONS: Before atlantoaxial transarticular surgery, vertebral groove depth should be evaluated and a safe screw trajectory angle should be plotted to determine anatomic suitability. This trajectory angle can be used with intraoperative real-time fluoroscopy to guide the surgeon during screw insertion.

Atlanto-Axial Joint↗

PubMed1978

Atlantoaxial malformation in a 46,XY, 17q+ child.

A child with 46,XY, 17q+ chromosome aberration and unusual skeletal abnormalities had the presenting symptom of respiratory arrest after a fall and minor head trauma. He exhibited proportionate short stature, peculiar facies with antimongoloid slant, simian creases, postaxial hexadactyly, metatarsus adductus deformity, and anomalous penoscrotal configuration. Delayed speech and mild mental retardation were also present. Atlantoaxial dislocation secondary to odontoid process hypoplasia was demonstrated. Additional skeletal abnormalities included dysplastic changes in the first and fourth metacarpals, the middle phalanx of the second finger, and hypoplasia of the first metatarsal, with medial insertion of the great toe. Treatment consisted of halo jacket cast and fusion of the occiput to C1, C2, and C3. Early detection and preventive surgery for atlantoaxial dislocation is necessary to prevent neurological deficit and possibly death by respiratory failure.

Axis, Cervical Vertebra↗

PubMed1981

Atlantoaxial subluxation. An unusual complication after local anesthesia for tonsillectomy.

After tonsillectomy, atlantoaxial subluxation occurred in two patients. Operations had been performed with the use of local anesthesia, and it was assumed that, during the injection of anesthetics, bacteria infected the prevertebral space. The initial symptoms of the prevertebral space infection were neck pain and stiffness; the movements of the neck were minimal, and opening of the mouth caused pain due to spasm of the deep cervical muscles. Both patients had persistent fever. The roentgenographically observed subluxation developed in one to two months after tonsillectomy. One of the patients was treated only with antibiotics; the other patient required atlantoaxial spondylodesis. Healing of the subluxation lasted about six months in both cases.

Adult↗

PubMed1976

Myelopathy in infancy complicating congenital atlantoaxial dislocation.

Two infants had congenital atlantoaxial dislocation associated with myelopathy. One of them, a 3-month-old girl, showed anterior dislocation of the atlas on the axis, and had extreme weakness of the extremities. Another patient, an 8-month-old boy, showed tetraplegia, and posterior dislocation with absent odontoid process was demonstrated radiologically. These cases add another cause to the varied etiologies of floppiness in early infancy.

Axis, Cervical Vertebra↗

PubMed1956