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PubMed1991

Os odontoideum with posterior atlantoaxial instability.

Nine patients who had os odontoideum with posterior atlantoaxial instability are reviewed. Three parameters were measured on the lateral radiographs: the distance from the os odontoideum to the spinous process of the axis in extension (Dext), the distance from the os odontoideum to the posterior arch of the atlas (Datl), and the degree of instability (Inst). Patients were classified into four groups: Group I, local symptoms (N = 3); Group II, transient myelopathy (N = 0); Group III, progressive myelopathy (N = 6); and Group IV, cerebral symptoms (N = 0). The development of cervical myelopathy was not related to degree of instability but to distance from the os to the spinous process of the axis (Dext). Dext was more than 16 mm in Group I and less than or equal to 16 mm in Group III. Five of six patients in Group III underwent myelography. Based on myelographic findings, Group III was further subdivided into two groups, Group IIIA (N = 2) and Group IIIB (N = 3), according to the following characteristics: In Group IIIA, the distance from the os to the posterior arch of the atlas was more than 13 mm, and the spinal cord was impinged between the os odontoideum and the lamina of the axis in extension and reduced in flexion. In Group IIIB, Datl was less than or equal to 13 mm, and the spinal cord was compressed at the level of the atlas during flexion and extension. Stenotic Datl of 13 mm or less specifically defined severe cervical myelopathy. Surgical treatment for cervical myelopathy in os odontoideum with posterior instability is suggested as follows: in the absence of canal stenosis of the atlas (Group IIIA), atlantoaxial fusion in a reduced position is indicated; when associated with canal stenosis of the atlas (Group IIIB), laminectomy of the atlas followed by occiput-to-C2 arthrodesis is indispensable.

Adolescent↗
PubMed1983

Fractures of the arches of the atlas: a study of their causation.

The autopsy findings in 32 accidental deaths which showed fracture(s) of the arches of the atlas have been correlated to reconstructions of the course of events in the accidents. Flexion of the head causing fracture(s) of the neural arch or odontoid process of the axis also resulted in fracture(s) of the posterior arch due to downward traction. Extension of the head causing fracture of the odontoid process of the axis gave rise to fractures of the posterior arch due to pressure from below. Tilting of the head caused marginal fractures of the anterior arch due to oblique traction. Tilting of the head also caused fracture(s) of the anterior and/or posterior arch due to transverse extension of the atlas ring and/or superior dislocation of one lateral mass in relation to the other. Oblique flexion or extension of the head resulted in similar fractures. Flexion of the head with some rotation combined with compression of the neck can cause the anterior margin of one upper joint surface of the axis to act as a wedge separating the anterior arch of the atlas from below. Extension of the head with some rotation combined with compression of the neck can lead to a fracture running through one lateral mass due to its tilting-dislocation in posterior direction. It is striking that there was no fracture of the atlas which could be ascribed to a simple and symmetric compression of the neck (classical Jefferson's fracture).

Accidents, Traffic↗
PubMed2004

Posterior screw placement on the lateral mass of atlas: an anatomic study.

STUDY DESIGN: An anatomic study evaluating the feasibility of posterior screw fixation on the lateral mass of the atlas and comparing the pullout force of C1 posterior lateral mass screws with that of occipital and C2 pedicle screws. OBJECTIVES: To study the feasibility, anatomy, and biomechanics of posterior screw fixation within the lateral mass of the atlas. SUMMARY OF BACKGROUND DATA: Occipitocervical fusion is a common choice for atlantoaxial dislocations. After that the movement of occipitocervical region will be restricted. If screws could be placed in the lateral mass of the atlas, 1) the movement of C0-C1 junction will be preserved; 2) through the screw the dislocated atlas could be pulled backward; and 3) the fractured lateral mass can be fixed using the posterior lateral mass screw directly. METHODS: Thirty atlas specimens of native adults were used to measure pertinent clinical data. Six fresh upper cervical specimens were used to observe the association of the C2 nerve and the lateral mass of the atlas. The pullout force of the C1 lateral mass was measured and compared with that of screws placed into the occiput and C2 pedicle, respectively. RESULTS: The distances from the midline to the midpoint of the C1 lateral mass, to the inner wall of the transverse foramen, and to the inner edge of the pedicle were 17.6 +/- 1.2 mm, 23.0 +/- 1.7 mm, and 14.2 +/-1.1 mm, respectively. The width and height of the C1 lateral mass were 11.6 +/- 1.4 mm and 12.7 +/- 1.0 mm, respectively. The distance between the inferior midpoint of the C1 lateral mass in the transverse plane of the midposterior arch of the atlas to the edge of the inferior atlas joint line was 4.1 +/- 0.7 mm. The width of the posterior arch at the point of vertebral artery overpass was 4.7 +/- 1.0 mm. The observation on the fresh specimens showed that the C2 nerve passes inferolateral to the C1-C2 joint and could be pulled sideways. The screw pullout force within the lateral mass of the atlas was 1818.16 +/- 422.67 N. This is significantly less than that of screws within the occiput, and there was no difference with that of a C2 pedicle screw. CONCLUSION: The width and height of the atlas lateral mass were larger than that of the C2 pedicle, and there was enough space to insert a 3.5-mm diameter screw in the atlas lateral mass over the C2 nerve. The pullout force of the screw on the lateral mass of the atlas was the same as that of the C2 pedicle screw. It is possible toinsert a 3.5-mm screw in the lateral mass of the atlas. The direction of the screw should be about 20 degrees anterosuperior in the vertical plane and 15 degrees inward in the horizontal plane. The suitable length of the screw should be approximately 22 mm inside the lateral mass.

Anthropometry↗
PubMed2005

Atlantoaxial transarticular screw fixation and posterior fusion using ultra-high-molecular-weight polyethylene cable.

This article attempts to evaluate the effectiveness of the ultra-high-molecular-weight polyethylene (UHMW-PE) cable system in atlantoaxial transarticular screw fixation and posterior fusion through the clinical results of 10 postoperative patients with atlantoaxial subluxation secondary to rheumatoid arthritis. Among them, one patient with only one screw placed owing to an anomalous vertebral artery had the correction loss of the 3-mm atlas-dens interval after surgery. Another patient had a second operation to remove the screw and cable after 2 years 11 months because a unilateral transarticular screw had come to protrude through the lateral mass of the atlas ventrally. All patients had achieved C1-C2 osseous fusion without any complications associated with this cable system. The UHMW-PE cable is a very useful material as sublaminar wiring in atlantoaxial transarticular screw fixation and posterior fusion.

Aged↗
PubMed1995

Anterolateral decompression of the atlantoaxial vertebral artery for symptomatic positional occlusion of the vertebral artery. Case report.

A case of repeated vertebrobasilar ischemic attacks related to head rotation (bow hunter's stroke) is reported. With head rotation of 45 degrees or more to the right, the patient would become lightheaded and feel as if she were going to lose consciousness. Angiography performed when head rotation was to the right revealed mechanical compression of the left vertebral artery at the foramen transversarium of the axis and an occluded right vertebral artery. Untethering of the vertebral artery as it passed through the foramen transversarium of the atlas in this case completely relieved the patient's symptoms. The authors conclude that contralateral vertebral artery occlusion predisposed this patient to symptomatic vertebrobasilar insufficiency secondary to ipsilateral vertebral artery mechanical stenosis induced by head turning.

Axis, Cervical Vertebra↗
PubMed1983

Indications and technique for the operative treatment of hypoplastic deformities of the odontoid process.

On the basis of four typical cases of congenital hypoplastic deformities of the odontoid process the clinical significance, symptoms, diagnosis and the indications for operative treatment of the malformations are described. It is further shown that these malformations lead to clinical manifestations only when associated with a primarily existing, or a later acquired inadequacy of the ligaments with movement-induced changes in the position of the atlas. The operative treatment recommended involves a special technique for a bilateral dorsal fixation with tibial grafts. By this operative technique a substantial or even completely stable fixation of the atlas can be achieved, in the acute phase by the stability of the tibial grafts and in the long term by the bony fusion which occurs.

Adult↗
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↗
PubMed2001

No neurological involvement for more than 40 years in Klippel-Feil syndrome with severe hypermobility of the upper cervical spine.

We report the case of a 42-year-old woman with Klippel-Feil syndrome, who showed severe hypermobility of the upper cervical spine without neurological involvement for more than 40 years. Radiographs revealed the presence of the odontoid bone and fusion of the atlas, odontoid bone, and occiput. Congenital fusion was present from the axis to C5 as a block vertebra. Lateral flexion-extension radiographs revealed severe hypermobility at the junction between the odontoid bone and the axis. Prophylactic surgical stabilization has been recommended in patients with severe hypermobility, but adjacent disc problems may possibly occur at the unfused levels in the future. We believe that early prophylactic stabilization should not be indicated for Klippel-Feil syndrome without neurological involvement only because of hypermobility.

Adult↗
PubMed2004

Level II lymph nodes and radiation-induced xerostomia.

PURPOSE: To investigate the influence of the cranial border of electively irradiated Level II lymph nodes on xerostomia in patients with oropharyngeal cancer using three-dimensional conformal and intensity-modulated radiotherapy (3D-CRT and IMRT). METHODS AND MATERIALS: The target volumes and organs at risk were delineated on the planning CT scans of 12 patients. Two elective target volumes were delineated. The first had the transverse process of the C1 atlas and the second had the transverse process of the C2 axis as cranial border of the Level II lymph nodes. 3D-CRT and IMRT planning were performed for both elective volumes, resulting in two plans per patient and technique, called the C1 and C2 plans, respectively. Irradiation of the ipsilateral elective volume up to C1 and the contralateral up to C2 was also performed for IMRT. The normal tissue complication probability (NTCP) for xerostomia 1 year after RT was calculated using the parotid mean dose. RESULTS: The average mean dose +/- standard deviation (SD) to the contralateral parotid gland was reduced from 33 +/- 5 Gy for the IMRT C1 plans to 26 +/- 4 Gy for the IMRT C2 plans and from 51 +/- 6 Gy to 49 +/- 7 Gy for the 3D-CRT C1 and C2 plans, respectively. The associated NTCP +/- SD for xerostomia was 38% +/- 10% for IMRT C1 plans and 24% +/- 6% for IMRT up to C2 on the contralateral side, regardless of which cranial border was irradiated on the ipsilateral side. For the 3D-CRT C1 and C2 plans, an NTCP value of 74% +/- 12% and 71% +/- 15% was obtained, respectively. The NTCP for xerostomia of the ipsilateral parotid gland was 53% +/- 17% and 45% +/- 20% for the IMRT C1 and C2 plans and 89% +/- 11% and 87% +/- 12% for the 3D-CRT C1 and C2 plans, respectively. CONCLUSION: Lowering the cranial border of the Level II lymph nodes from C1 to C2, in the case of bilateral elective neck irradiation, could be considered on the contralateral side when the risk of metastasis on that side is very low. This is especially true when IMRT is used, because the relative reduction of NTCP for xerostomia 1 year after RT could be up to 68% compared with conventional conformal RT up to C1.

Cervical Vertebrae↗
PubMed2004

[Experimental study of posterior pedicle screw placement on atlas].

OBJECTIVE: To assess the possibility of placing the posterior pedicle screw on atlas. METHODS: Twenty human cadaver specimens were used to insert pedicle screws in atlas, through the posterior arch or the pedicle of C1 into the lateral mass. The screw entry point was on the posterior surface of C1 posterior arch and at the intersection of the vertical line through the center of C2 inferior articular process and the horizontal line at least 3 mm below the superior rim of the C1 lamina. The screw of 3.5 mm in diameter was placed in a direction of 10 degrees medial angle and 5 dgrees upward angle. After placement of C1 pedicle screw, the distance from C1 screw entry point to the medial-lateral midpoint of C1 pedicle, the maximum length of screw trajectory and the actual screw trajectory angles were measured. The direction of screw penetrating through the cortical of C1 pedicle or lateral mass and the injuries to the vertebral artery and spinal cord were observed. RESULTS: Forty pedicle screws were placed on atlas, the mean distance from C1 screw entry point to the medial-lateral midpoint of C1 pedicle was (2.20 +/- 0.42)mm, the maximum length of screw trajectory averaged (30.51 +/- 1.59)mm, and the actual screw trajectory angle measured (9.7 +/- 0.67)degrees in a medial direction and (4.6 +/- 0.59)degrees in a upward direction. Only 1 screw penetrated the upper cortical bone of the atlas pedicle because the upward angle was too large, and 8 screws were inserted so deep that the inferior cortical bone of the C1 lateral mass was penetrated. But no injuries to the vertebral artery and spinal cord were observed. CONCLUSION: C1 posterior pedicle screw fixation is quite accessible and safe, but the surgeons should pay attention to the angle and the depth of the screw placement.

Adult↗
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↗
PubMed1981

Osteoarthritis of the alanto-axial joint.

Thirty-one patients suffering from osteoarthritis of the atlanto-axial joint are described, suggesting that this disease is not particularly uncommon. The most characteristic radiological signs are narrowing of the joint space from loss of articular cartilage, marginal cortical thickening and osteophyte formation. Histological examination in the cadaver has shown thinning and fibrillation of articular cartilage and intra-cartilaginous ossification. The radiological appearances of the atlanto-axial joint are classified in three types, lateral atlanto-axial, atlanto-odontoid and mixed. Peak age distribution occurs between 50 and 69 years of age. Patients complain of occipital pain, a stiff shoulder and paraesthesia of the fingers. Treatment was conservative in all cases except one, a 63-year-old woman with severe occipital pain. A transoral atlanto-axial fusion was performed in this case with marked improvement. The transoral approach allows fixation and curettage of the degenerative lesions.

Adult↗
PubMed1982

Morphological and functional studies on the lateral joints of the first and second cervical vertebrae in man.

The articular surfaces of the lateral atlanto-axial joints in man were analyzed with respect to their biomechanical aspects. The joint surfaces were investigated macroscopically, and the texture of the tangential fiber layer of the articular cartilage was studied with the aid of the split-line method. Furthermore, the thickness of cartilage was measured. From the results obtained the authors draw the conclusion that especially the mode of rotational movement between C1 and C2 changes within a life time. As a consequence, the distribution of stress in the lateral atlanto-axial joint is modified.

Adolescent↗
PubMed1979

The radiology of rheumatoid involvement of the cervical spine.

The radiological features of cervical spine involvement in rheumatoid arthritis are described. These include atlanto-axial subluxation, in both the horizontal and vertical planes, sub-axial dislocation, erosions, and vertebral end plate sclerosis. Detailed radiological investigation, using inclined plane radiography, auto-tomography, tomography, and myelography may all be required to demonstrate the abnormalities. Disorders of mobility can only be assessed with dynamic views and fluoroscopy and the mechanics of these derangements vary depending on the type of subluxation encountered. The cumulative effects of the lesions conform to certain characteristic patterns and include marked reduction of neck height, disorders of mobility, and changes in the capacity of the spinal canal. The discrepancy between these changes and the clinical and neurological findings is discussed.

Arthritis, Rheumatoid↗
PubMed1982

Posterior atlanto-axial fusion: a new compression clamp for laminar osteosynthesis.

A new method of dorsal arthrodesis in patients with atlanto-axial instability of different etiology is described. In three patients solid laminar osteosynthesis C1/C2 was achieved by insertion of an autogenous cortico-cancellous bone graft into the interlaminar space and by a bilateral application of the lately developed metal clamp. The technical principles of the clamp guarantee a permanent pressure on the graft and a solid initial stability in the segment. Additional external fixation and immobilization of the patient are not necessary. Complications as known from other procedures of the atlanto-axial dorsal fusion will be prevented efficiently.

Adolescent↗
PubMed2006

Anterior retropharyngeal fixation C1-2 for stabilization of atlantoaxial instabilities: study of feasibility, technical description and preliminary results.

Posterior transarticular screw fixation C1-2 with the Magerl technique is a challenging procedure for stabilization of atlantoaxial instabilities. Although its high primary stability favoured it to sublaminar wire-based techniques, the close merging of the vertebral artery (VA) and its violation during screw passage inside the axis emphasizes its potential risk. Also, posterior approach to the upper cervical spine produces extensive, as well as traumatic soft-tissue stripping. In comparison, anterior transarticular screw fixation C1-2 is an atraumatic technique, but has been neglected in the literature, even though promising results are published and lectured to date. In 2004, anterior screw fixation C1-2 was introduced in our department for the treatment of atlantoaxial instabilities. As it showed convincing results, its general anatomic feasibility was worked up. The distance between mid-sagittal line of C2 and medial border of the VA groove resembles the most important anatomic landmark in anterior transarticular screw fixation C1-2. Therefore, CT based measurements on 42 healthy specimens without pathology of the cervical spine were performed. Our data are compiled in an extended collection of anatomic landmarks relevant for anterior transarticular screw fixation C1-2. Based on anatomic findings, the technique and its feasibility in daily clinical work is depicted and discussed on our preliminary results in seven patients.

Adolescent↗