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Fractures of the odontoid process of the axis create problems of specific osteosynthesis. The different techniques described so far require an external support and limit the movements of the cranio-cervical joint. These 2 drawbacks are avoided by direct screw fixation of the odontoid process in cases where conditions are favourable to this procedure.
Odontoid process fractures are commonly classified as types I through III according to the Anderson & D'Alonzo scheme. A fourth type of fracture not included in this classification has been described as "vertical odontoid fracture". These fractures are located in the vertical plan of the dens. We describe a new case of an oblique coronally oriented fracture through the odontoid process with extension to the body of C2. Our patient is a 22-year-old lady who sustained a road traffic accident with head, facial and cervical trauma. Computed tomography with 2D and 3D reconstruction characterized the fracture. We suppose that the mechanism of injury was an axial load associated with dorsal to ventral force. The patient was placed on a halo-vest for 12 weeks with good healing and no evidence of instability on flexion-extension studies 6 months later. This case demonstrates that the odontoid and C2 vertebral body fractures belong to the same spectrum and are determined by the patient's anatomy and the mechanism of the injury.
BACKGROUND: Pyogenic osteomyelitis of the odontoid process is a very rare disease associated with a variety of clinical symptoms, and previous reports have stressed the difficulties inherent in making the diagnosis. The authors present a case of osteomyelitis of the odontoid process with epidural abscess in which magnetic resonance imaging (MRI) was used in the diagnosis, assessment of the extent of concomitant epidural abscess, treatment effect, and long-term follow-up. CASE DESCRIPTION: A 68-year-old male was admitted to our hospital with cervical pain, neck stiffness, and fever. Although the diagnosis was missed at the beginning, the patient was diagnosed with osteomyelitis of the odontoid process with a paravertebral epidural abscess by MRI. The patient became asymptomatic after 3 months of antibiotic therapy. CONCLUSION: Pyogenic osteomyelitis of the odontoid process is a rare condition requiring a high index of suspicion for diagnosis. MRI examination should be considered in the diagnosis in patients with neck pain combined with fever. Serial MRI during and after antibiotic therapy provided an objective assessment of the healing rate of the lesions.
The axis from twenty-two cadavera was removed at autopsy and was sectioned in the sagittal plane to a thickness of one millimeter with use of a surface-stained block-grinding technique. Combined two and three-dimensional analysis included an evaluation of the volume of the trabecular bone, the trabecular interconnection, and the cortical thickness as well as qualitative investigation of the structure of the cancellous bone. The body of the axis, the base of the odontoid process, and the odontoid process were analyzed separately. The base of the odontoid process is a region of least resistance for fractures because of its unique microarchitecture. The mean volume of trabecular bone of the base of the odontoid process is 55 per cent less than that of the axis and the odontoid process. The base also has a markedly poorer trabecular interconnection and a cortical thickness that is one-third that of the odontoid process. In all of the specimens, trabeculae that were disconnected from the trabecular lattice (trabeculae with free ends) were demonstrated in the base of the odontoid process. The formation of microcallus in six (27 per cent) of the specimens supports the hypothesis that microfractures occur as a result of stress peaks, mechanical fatigue, and the relative insufficiency of bone in the static condition. Therefore, the base of the odontoid process can be considered as a site of predilection for fractures.
Fifteen percent of cervical spine fractures involve the odontoid process. Most odontoid fractures can be classified as Types I through III according to the scheme developed by Anderson and D'Alonzo. We report a case of a vertically oriented fracture through the odontoid process that does not fit into any of these categories. Only two such cases have been described in the literature. Our patient is an 18-year-old man who sustained an axial loading injury to his cervical spine. Plain lateral cervical tomography and computed tomography were performed to characterize the fracture and to evaluate the instability. The patient was placed in a rigid orthosis for 12 weeks, and at 6-month follow-up, he had full range of motion and showed no evidence of abnormal movement, as revealed by flexion-extension studies. This case demonstrates the shortcomings of the current classification system for odontoid fractures and value of plain tomography and computed tomography in evaluating odontoid fractures.
The odontoid process of C2 projects upward from the superior roof of the body of C2. There is a confusion about the inferior border of the odontoid. The aims of this clinical study were to describe the inferior border of the odontoid process based on the remnant of dentocentral synchondrosis in adults, and the estimation of the odontoid/body ratio in pediatric and adult ages. Sixty-six cases were included for this study. Forty-four of them were in adult ages and the remaining 22 of them were in pediatric ages. The region of occiput, C1, C2, and C3, was examined with the magnetic resonance imaging (MRI) in all cases. The length of the odontoid process was estimated by using radiological images of MR from the tip of the odontoid to the remnant of dentocentral synchondrosis. The portion located under the level of synchondrosis was considered as the body of C2. The average length of the odontoid was 18. 6 mm in pediatric and 21. 3 mm in adult cases. In adult females, the length of the odontoid process (19. 1 mm in length) was smaller than those of adult males (23. 6 mm in length). The average ratio of odontoid/body was two in pediatric and 1.8 in adult cases. This study demonstrated that the neck of the odontoid segment at the level of superior articulating facets is not the synchondrosis between the odontoid process and the body of C2. The synchondrosis is located well below the level of superior articulating facets. It can be demonstrated with sagittal and coronal images of MR in both of pediatric and adult individuals.
OBJECT: The quantitative analysis of odontoid process angulation has had scant attention in the Chiari I malformation population. In this study the authors sought to elucidate the correlation between posterior angulation of the odontoid process and patients with Chiari I malformation. METHODS: Magnetic resonance images of the craniocervical junction obtained in 100 children with Chiari I malformation and in 50 children with normal intracranial anatomy (controls) were analyzed. Specific attention was focused on measuring the degree of angulation of the odontoid process and assigning a score to the various degrees. Postoperative outcome following posterior cranial fossa decompression was then correlated to grades of angulation. Other measurements included midsagittal lengths of the foramen magnum and basiocciput, the authors' institutions' previously documented pB-C2 line (a line drawn perpendicular to one drawn between the basion and the posterior aspect of the C-2 body), level of the obex from a midpoint of the McRae line, and the extent of tonsillar herniation. Higher grades of odontoid angulation (retroflexion) were found to be more frequently associated with syringomyelia and particularly holocord syringes. Higher grades of angulation were more common in female patients and were often found to have obices that were caudally displaced greater than three standard deviations below normal. CONCLUSIONS: These results not only confirm prior reports of an increased incidence of a retroflexed odontoid process in Chiari I malformation but quantitatively define grades of inclination. Grades of angulation were not found to correlate with postoperative outcome. It is the authors' hopes that these data add to our current limited understanding of the mechanisms involved in hindbrain herniation.
Pyogenic osteomyelitis of the odontoid process is a rare condition requiring a high index of suspicion for diagnosis. The three cases presented illustrate that patients with severe neck pain, aggravated by rotation, and persistent fever without apparent source should be studied carefully to exclude infection of the C1-C2 area. The unusual anatomy of the C1-C2 articulation may make routine diagnostic studies difficult to interpret. Computed tomography, magnetic resonance imaging, and 111In-labeled white blood cell scans may improve diagnostic accuracy. Treatment includes rigid immobilization, high dose antibiotics, and surgical stabilization in selected cases.
Six cases of spontaneous fracture of the odontoid process in rheumatoid arthritis are presented. Fifty-one patients with atlantoaxial subluxation in rheumatoid arthritis underwent surgery between 1981 and 1990. This included six patients (in 10%) who had subluxation accompanied by fracture of the odontoid without apparent trauma. The mean patient age was 58 years and all had a long history of rheumatoid arthritis. No trauma was considered to be the cause of the fracture. This is a fracture caused by erosion and osteoporosis of the odontoid process due to rheumatoid synovitis, aging and steroid therapy. In addition, another cause is a dynamic load produced from the instability accompanying atlantoaxial subluxation working on the odontoid in cervical extension. It is important remember that the odontoid process is susceptible to spontaneous fracture.
Fractures of the base of odontoid process are serious spinal injuries. Their treatment still remains controversial. External rigid immobilisation is the way of conservative healing. Operations by posterior approach: posterior atlantoaxial fixation, atlantoaxial transarticular screw fixation or even occipitocervical fixation limit range of head motion. Direct odontoid screw fixation preserves normal motion of C1-C2 junction. Success of this method depends on proper patients selection. The authors present description of surgical technique based on literature review and their own experience. The authors perform odontoid fixation by means of single cannulated cancellous screw guided by K-wire. This wire provides stability of broken odontoid process during procedure of screw insertion. Old fracture--1 case in author's experience--has been curetted before fixation. The authors reviewed clinical efficacity and results of direct odontoid screw fixation published in current literature.
BACKGROUND: The majority of benign spinal osteoblastomas arise from the posterior elements of the spine; there have been no published reports of the tumor in the odontoid process of the axis. Accurate preoperative localization of the tumor is important for planning minimally invasive surgery on such benign tumors. However, the magnetic resonance imaging (MRI) findings may be misleading, because peritumoral changes may be confusing. CASE DESCRIPTION: We report the case of a 20-year-old man, who presented with a 4-year history of protracted left posterior neck pain. Preoperative computed tomography (CT) revealed a discrete mixed-density mass within the odontoid process. MRI showed diffusely abnormal signal intensity and enhancement both in the odontoid process and the body of the axis, including regions from which biopsy specimens were normal or had minimal inflammatory changes. Precise preoperative localization of the tumor margins using CT and biopsy allowed for successful resection of the tumor via a transoral approach with preservation of a part of the axis and the odontoid process. Consequently, stabilization of the spine was unnecessary, and the patient remained symptom-free for 3.5 years. CONCLUSION: We reported a rare case of benign osteoblastoma of the odontoid process of the axis. The tumor was successfully resected via a transoral approach, preserving a part of the axis and the odontoid process. We have emphasized an advantage of CT over MRI for accurate localization of the tumor.
We describe two cases of combined fractures of the odontoid process and upper thoracic spine that have not been previously reported. The first patient, a 21-year-old man, sustained an odontoid process fracture with posterior displacement and a fracture-dislocation injury at T4/5 in a motorcycle accident. The second patient, a 66-year-old woman, fell from a cliff and sustained an odontoid process fracture with posterior displacement and a bursting fracture at T3 and T4 with rotation. The first patient exhibited complete paraplegia below the T5 level of the spinal cord. The second patient escaped neurological deficit. Both underwent anterior screw fixation of the odontoid process and posterior fusion of the upper thoracic spine. In both cases the cervical spine seemed to be in hyperextension, and the upper thoracic spine experienced sudden flexion and rotation forces.
In type-II fractures of the odontoid process, the treatment is either conservative in a halo vest or primary surgical stabilisation. Since nonunion, requiring prolonged immobilisation or late surgery, is common in patients treated in a halo vest, the identification of those in whom this treatment is likely to fail is important. We reviewed the data of 69 patients with acute type-II fractures of the odontoid process treated in a halo vest. The mean follow-up was 12 months. Conservative treatment was successful, resulting in bony union in 32 (46%) patients. Anterior dislocation, gender and age were unrelated to nonunion. However, nonunion did correlate with a fracture gap (> 1 mm), posterior displacement (> 5 mm), delayed start of treatment (> 4 days) and posterior redisplacement (> 2 mm). We conclude that patients presenting with these risk factors are unlikely to achieve bony union by treatment in a halo vest. They deserve careful attention during the follow-up period and should also be considered as candidates for primary surgical stabilisation.
Fracture of the odontoid process in young children is possibly not as rare as hitherto believed. In this paper, two more patients with this fracture are presented, and an important diagnostic clinical sign is described. Both patients sustained the injury by falling from heights no greater than sixty-one to ninety-one centimeters. In each instance, injury to the cervical spine was suspected but initial roentgenograms failed to reveal any fracture. The patients were quite comfortable when lying supine and when fully erect. Each child strongly resisted any attempt at extension of the neck and cried bitterly when brought to either the erect or the recumbent position unless the head was passively supported. This a valuable clinical sign when injury to the odontoid process is suspected. Subsequent roentgenograms confirmed the diagnosis in each instance.
The origin of transverse arterial branches that contribute to the arterial supply of the odontoid process (dens axis) is not clear. Dissections were performed on 20 injected fetal and adult human cranio-cervical junctions to demonstrate the origin of the arteries that contribute feeding branches to the arteries supplying the neck of the odontoid process. At its termination near the anterior arch of the atlas, the ascending pharyngeal artery gave off transverse branches that anastomosed with the anterior ascending arteries to the odontoid process. It also gave off a branch that traversed the hypoglossal canal and anastomosed with the posterior ascending artery. A small branch linked the posterior ascending artery to the first transverse branch. This investigation complements previous work on the arterial supply to the odontoid process.
The transoral approach to the odontoid process is considered the "gold standard" for resection of extradural lesions at this location. A completely transnasal endoscopic approach is feasible based on anatomic studies and our experience with the expanded endonasal approach for neoplasms of the cranial base. An illustrative case is presented to demonstrate the technical details of a fully transnasal completely endoscopic approach for the resection of the odontoid process. A 73-year-old woman with a long-standing history of rheumatoid arthritis presented with progressive cervicomedullary compression. Complete resection of the odontoid was achieved with no significant morbidity. This is the first reported case of a completely endoscopic resection of the odontoid using a fully transnasal route. The report demonstrates the feasibility of this approach and larger clinical series with long-term follow-up will be needed to determine the reproducibility and validation of any potential benefits.
A case of an osteoblastoma located in the odontoid process in a 7 year-old boy who presented with torticollis is reported. CT scan and MRI disclosed the lesion, but diagnosis was established by a CT-guided needle biopsy. Surgery through a transoral approach allowed total excision of the tumor. This is, to our knowledge, the first case reported of an osteoblastoma of the odontoid process.
We treated 183 patients with fractures of the odontoid process (109 type II, 74 type III) non-operatively. Union was achieved in 59 (54%) with type-II fractures. All type-III fractures united, but in 16 patients union was delayed. There was no correlation between union and the clinical or radiological outcome of the fractures. Selective vertebral angiography, carried out in 18 patients ten with acute fractures and eight with nonunion, showed that the blood supply to the odontoid process was not disrupted. Studies on ten adult axis vertebrae at post-mortem showed that the difference in the surface area between type-II and type-III fractures was statistically significant. Our findings show that an age of more than 40 years, anterior displacement of more than 4 mm, posterior displacement and late presentation contribute towards nonunion of type-II fractures.