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The reliability of the lateral radiograph in determination of the optimal transarticular C1-C2 screw length.

STUDY DESIGN: This study assessed the value of using lateral radiographs in evaluating the optimal screw length in transarticular C1-C2 screw fixation. OBJECTIVES: To assess the reliability of the lateral radiograph in determining the optimal transarticular C1-C2 screw length. SUMMARY OF BACKGROUND DATA: Transarticular C1-C2 screw placement is usually performed using anatomic landmarks and fluoroscopy. A lateral fluoroscopic image is valuable when directing screws in the sagittal plane, but its exact role in determining screw length has not been investigated. METHODS: Eight cervical spine specimens were used in this study. Screw placements were performed in each specimen, fixed in the exact lateral position and under direct visualization. After each placement, a lateral radiograph was taken. The odontoid process was divided into three equal portions. Another portion anterior to the odontoid process was called the anterior tubercle region. The number of screw tips appearing in each portion on the radiograph was then recorded for each placement. In addition, 30 C1 specimens were measured to evaluate the anterior part of C1. RESULTS: The results showed that 12.5% of the screws placed 2 mm short of reaching the ventral cortex and 0 mm overpenetrating the ventral cortex of the lateral mass of C1 projected in the radiograph on the anterior tubercle region, 37.5% on the anterior region of the odontoid process, and 50% on the middle region of the odontoid process. Twenty-five percent of the screws that were placed to overpenetrate, by 2 or 4 mm, the ventral cortex of the lateral mass of C1 were projected on the anterior tubercle region in the radiograph, and 50% and 62.5% were projected on the anterior region of the odontoid process, respectively. The mean vertical distance between the anteriormost point of the anterior tubercle of the anterior ring and the middle of the ventral cortex of the lateral in all specimens was 5.6 +/- 1 mm, and the mean transverse angle of the anterior ring relative to the frontal plane was 21.1 +/- 3.5 degrees. CONCLUSIONS: This results in this study indicate that a lateral radiograph may not be reliable in determining the optimal screw length, although it is valuable in directing accurate screw angle in the sagittal plane. Preoperative computed tomographic evaluation of the C1-C2 region may be helpful in estimating the location of the screw tip on the lateral radiograph during surgery.

Adult↗

Atraumatic odontoid fractures in patients with rheumatoid arthritis.

BACKGROUND CONTEXT: Instability of the cervical spine is a common problem in patients with rheumatoid arthritis. The natural course of rheumatoid arthritis in the cervical spine is well documented. However, the true prevalence of occult fractures of the odontoid process in patients with rheumatoid arthritis is not known. PURPOSE: To draw attention to the possibility of occult, atraumatic fractures of the odontoid process in patients with rheumatoid arthritis. STUDY DESIGN: We report on two cases with previously unrecognized fractures of the odontoid process. METHODS: In this case series, we review the individual radiographic findings and clinical observations in two rheumatoid patients in whom a fracture of the odontoid process was diagnosed. RESULTS: Each one of these two rheumatoid patients had an unrecognized fracture of the odontoid process without any prior history of trauma. Their fracture was identified serendipitously during workup for neck pain. CONCLUSIONS: Occult, atraumatic fractures of the odontoid process may be found in patients with long-standing rheumatoid arthritis. This injury should be suspected if previously asymptomatic patients complain about new onset of neck pain without significant trauma.

Aged↗

Fatal transdental posterior rotary subluxation of the cervical spine. A case report.

STUDY DESIGN: The cervical spine of an 86-year-old man known to have a fracture of the odontoid process was removed at autopsy and dissected. OBJECTIVES: To establish the cause of death, which was not apparent. SUMMARY OF BACKGROUND DATA: Ruptures of the vertebral arteries in patients with fractures of the odontoid process are rare. Only a few reports are published in the literature. Those that address postmortem findings in patients with fractures of the odontoid process do not make any reference to associated capsular and ligamentous injuries and the resultant instabilities. METHODS: Because of legal constraints, the cervical spine was removed en bloc 1 week after the patient's death and carefully dissected. RESULTS: In addition to the known bony injury, rupture of the left vertebral artery, epidural hematoma, disruption of the posterior atlantoaxial ligaments, hemorrhage into the anterior ligamentous structures, rupture of the capsule of the right atlantoaxial joint, and stretching of the capsule of the left joint were found to be present. Displacement of the spinal cord by an epidural hematoma secondary to rupture of the left vertebral artery was recorded as the apparent cause of death. The rupture had obviously been caused by the abnormal rotation of the atlas on the axis in a clockwise direction. CONCLUSIONS: Both the fatal outcome and the pathologic examination showed that established management concepts, particularly screw fixation of a fractured odontoid process, should be reconsidered in light of the potential occurrence of transdental posterior rotary subluxation. Because the incidence of capsular, ligamentous, and vascular injuries associated with fractures of the odontoid process is still poorly understood, more autopsies would be needed. The case also raises the question of whether, in an elderly patient like ours, a fracture of the odontoid process should prompt immediate surgical stabilization.

Aged↗

Odontoid screw fixation for fresh and remote fractures.

Fractures of the odontoid process are common, accounting for 10% to 20% of all cervical spine fractures. Odontoid process fractures are classified into three types depending on the location of the fracture line. Various treatment options are available for each of these fracture types and include application of a cervical orthosis, direct anterior screw fixation, and posterior cervical fusion. If a patient requires surgical treatment of an odontoid process fracture, the timing of treatment may affect fusion rates, particularly if direct anterior odontoid screw fixation is selected as the treatment method. For example, type II odontoid fractures treated within the first 6 months of injury with direct anterior odontoid screw fixation have an 88% fusion rate, whereas fractures treated after 18 months have only a 25% fusion rate. In this review, we discuss the etiology, biomechanics, diagnosis, and treatment (including factors affecting fusion such as timing and fracture orientation) options available for odontoid process fractures.

Bone Screws↗

The tectorial membrane: anatomical, biomechanical, and histological analysis.

There is minimal information in the literature regarding the tectorial membrane. Further, information in the literature regarding the anatomy and function of this structure is often contradictory. We performed the current study to elucidate further this structure's detailed anatomy, function, and histology. Thirteen adult cadavers underwent dissection of their tectorial membranes and detailed observations and measurements were made of them. Ranges of motion of the craniocervical junction were performed before and after transection of this structure. Histological analysis was performed on all membranes. The tectorial membrane was found to attach much more superiorly than previously described and was found to be firmly adherent to the cranial base and body of the axis but not to the posterior aspect of the odontoid process. The mean thickness of this membrane was found to be 1 mm. Flexion of the head made the tectorial membrane fully taut at 15 degrees and extension made it fully taut at 20 degrees; however, there was a buckling effect (redundant tectorial membrane) noted at the level of the odontoid process in extension. With the alar and transverse ligaments cut and with flexion of the head, the middle portion of this membrane was stretched over the odontoid process, thus acting as a "hammock" that inhibited the odontoid process from moving posteriorly. The tectorial membrane did not limit cervical flexion per se but rather helped to insure that the odontoid process did not impinge into the cervical canal. Lateral flexion was not found to be limited by this structure. Histologically, parallel collagen fibers with spindle-shaped fibrocytes were observed within this membrane and near its attachment to the posterior axis, the collagen fibers were noted to be more homogenous with larger non-spindled fibrocytes. At the cranial attachment of the tectorial membrane, multiple calcified areas were noted that interdigitated with the underlying bone. Also near this cephalic bony attachment, there was an increase in the number of elastic fibers, which were found running parallel with the surrounding Type III collagen fibers. The tectorial membrane was found to attach much more superiorly than previously described. We would propose that the tectorial membrane provides for a second line of defense, preventing the odontoid process from compressing the spinal cord and by doing so, secondarily limits movement of the craniocervical juncture. This hypothesis is strengthened by the finding of many elastic fibers in the tectorial membrane. To our knowledge, our study is the first to perform a detailed histological analysis of the tectorial membrane. We hope that these data are useful to the clinician who investigates this ligament of the craniocervical region.

Aged↗

Calcium pyrophosphate dihydrate crystal deposition in and around the atlantoaxial joint: association with type 2 odontoid fractures in nine patients.

PURPOSE: To investigate the histopathologic anatomy of calcium pyrophosphate dihydrate (CPPD) crystal deposition in and around the atlantoaxial joint and the association between CPPD crystal deposition and subchondral cysts, erosions, and fracture involving the odontoid process of the axis. MATERIALS AND METHODS: One adult cadaver demonstrating calcification in the retro-odontoid area at computed tomography (CT) was selected for further radiography, CT, and magnetic resonance (MR) imaging at the C1-2 level. Anatomic sectioning and histologic evaluations were performed in the specimen. For clinical study, radiographs (n = 5), CT scans (n = 8), and MR images (n = 6) in nine patients (mean age, 74.4 years) with odontoid process fractures and CPPD crystal deposits in and around the atlantoaxial joint were reviewed. RESULTS: In the cadaveric specimen, radiography and CT demonstrated calcifications in the transverse ligament; histologic evaluation confirmed that these calcifications were CPPD crystal deposits. In all nine patients, radiography (n = 5) and CT (n = 8) also showed calcification in areas adjacent to the odontoid process, which included the transverse ligament. T1- and T2-weighted MR imaging showed a retro-odontoid mass of low signal intensity that compressed the cervical cord in six patients. CT, MR imaging, or both demonstrated subchondral cysts, osseous erosions, or a type 2 odontoid fracture in all patients. CONCLUSION: CPPD crystal deposition disease involving the C1-C2 articulation can be a clinically important entity that may place affected patients at increased risk of pathologic fracture of the odontoid process.

Aged↗

[Transoral decompression of the brain stem in a basilar impression secondary to rheumatoid arthritis. Description of a case and survey of the literature].

INTRODUCTION: The vertical subluxation or translocation of the odontoid process producing a basilar impression with compression of the brain stem is a late phenomenon in the course of rheumatoid arthritis; the appearance of symptoms in the spinal cord and the lower pairs of spinal nerves is a specific sign of this disorder. In this situation, the standard surgical aims are the decompression of the affected nerve structures followed by craniocervical stabilisation. The objective of this paper is to report on the improvement of the neurological deficit after decompressive transoral surgery (odontoidectomy), without associating any internal fixation system, in a female patient with a long history of rheumatoid arthritis and anterior compression of the brain stem caused by basilar impression and rheumatoid pannus. A survey of the literature showed that, with the odd isolated clinical case, there are no papers which describe the post operative development of surgical decompression of the brain stem carried out through an anterior approach in patients with rheumatoid subluxation of the odontoid process, without associating any internal stabilisation system. CASE REPORT: Female aged 65, diagnosed as suffering from rheumatoid arthritis at the age of 25, who was admitted with symptoms of compression of the medulla oblongata secondary to a vertical subluxation of the odontoid process. She was submitted to transoral decompression of the brain stem (odontoidectomy and removal of pannus without posterior fixation), and made surprisingly favourable post operative progress. At 15 months after the surgical decompression she led an independent life. CONCLUSIONS: The neurological improvement of our patient after the decompressive odontoidectomy suggests that the mechanical compression of the odontoid process with impaction of the brain stem was the predominant aetiological factor causing the symptoms in the medulla oblongata. Her clinical stabilisation, on the other hand, can be explained by a mechanism involving the spontaneous autofusion of the lateral masses of the atlas with the occipital condyle and with the axis. Lastly, we consider that, in certain cases of rheumatoid patients with atlantoaxial subluxation, impaction of the odontoid process in the foramen magnum and clinical features involving compression of the medulla oblongata, transoral decompression of the brain stem through an odontoidectomy is the choice initial surgical procedure, since it affords neurological improvement and clinical stabilisation. In any case, a strict neurological and radiological post operative follow up is needed in view of a possible craniocervical fixation occurring in the future.

Aged↗

[Dorsal stabilization in dislocated fractures of C-1 and C-2 vertebrae with Palacos and wiring].

During 1 year 6 patients with dislocated fractures of C-1 and C-2 vertebrae (fractures of the odontoid process) and 1 patient with a pseudarthrosis of the odontoid process have been treated. 6 patients have been treated surgically by internal fixation of the arch of C-1 and C-2 spinous process by wiring and plastic material (Palacos). No complications occurred. The advantage of the method was early mobilization of the patients and reduction of hospitalization. Clinical and radiographic follow-up studies showed stable fusion on Flexion-extension X-rays and boney union of the fracture of the odontoid process.

Adolescent↗

[Ossiculum terminale (Bergmann). Differential diagnosis of an odontoid fracture of the Anderson I type].

We describe a case of the rare entity of a persistent ossicle on the top of the odontoid process. In a short review of the literature, we show developmental abnormalities of the odontoid process and its etiologies. The terminal ossicle (Bergmann) plays an important role in the differential diagnosis of a fracture of the odontoid process type I in adults using the classification of Anderson and D'Alonzo. If fracture and instability is excluded by plain radiographs, computed tomography and/or MRI, there is no need for additional therapy.

Accidents, Traffic↗

[Acute bacterial meningitis and foramen magnum syndrome as a presentation of odontoid osteomyelitis. A case report].

A 77-year-old male was hospitalized with a 6-day history of severe posterior cervical pain and headache. An initial lumbar puncture revealed polymorphonuclear pleocytosis indicating pyogenic meningitis. The blood and throat cultures on admission were positive for Staphylococcus aureus. A combination of ceftriaxone and ABPC, both of which were sensitive to the pathogen, were intravenously administered for one month, by which he responded well as to the meningitis. However, he was found to have persistent neck pain, and wasting and weakness of the shoulder girdles, which were associated with polyneuropathy-like sensory loss. Neuroimaging studies disclosed a partial destruction of the odontoid process, subluxation of the atlantoaxial joint, MRI evidence of an inflammatory pseudomass formation dorsal to the odontoid process and an increased uptake of radionuclide on bone scanning, all of which were indicative of osteomyelitic processes at the region of the axis; i.e., the meningitis was thought to be secondary to osteomyelitis of the odontoid process and hence the foramen magnum syndrome characteristic to this particular case was explained by the compression of the cervicomedullary junction due to the pseudomass. To our knowledge, this is the first case of primary odontoid osteomyelitis to be reported in Japan.

Acute Disease↗

Three dimensional CT evaluation of occipito-atlanto-axial dislocation in rheumatoid arthritis.

Involvement of the upper cervical spine, with possible instability and dislocation of the atlanto-axial-cervico-occipital joints in patients with rheumatoid arthritis (RA), is routinely monitored with conventional radiographs. As disease progresses severe interpretation problems occur, especially when looking for cranial migration of the odontoid process. The aim of the present study was to evaluate whether three dimensional CT examination should be considered for such monitoring. After clinical and biochemical examination of 20 consecutive patients, diagnostic information about cranial migration of the odontoid process was obtained by conventional radiograms and by three dimensional CT examination. When using conventional radiographs the odontoid process and the its relation to the skull base could be outlined in 8 of the 20 patients. whereas all bony structures could be well demonstrated on the CT examination and the degree of cranial migration into the foramen magnum could be quantified. Three dimensional CT should be considered as a reliable examination for monitoring RA patients with involvement of the upper cervical spine and a possible cranial migration of the odontoid process.

Adult↗

[Bony malformations of the cranio-vertebral junction and its clinical relevance (author's transl)].

A statistical analysis is performed in 86 cases suffering from osseous malformation of the cranio-vertebral junction. The material consists of 71 cases with basilar impression, 8 cases with hypoplasia or absence of the odontoid process, and 7 cases with a congenital atlanto-epistropheal dislocation. The patients are clinically asymptomatic in 23 cases, and are marked by a para-respectively tetraparesis in 28 cases, by bulbar-pontine-cerebellar disorders in 24 cases, and by syringomyelia in 11 cases. A control group is included consisting of 30 cases without neurological symptoms and with a normal radiological finding of the cranio-vertebral region. The following measured values are taken in consideration to perform a statistical calculation using the simple variance analysis: The height of the odontoid process above of McGregor's line, the distance between the back of the odontoid process and the inner limit of the arch of C1, and, concerning the groups with hypoplasia of the odontoid process process and with atlanto-axial dislocation, the narrowing of the spinal canal at the level of C1 dependent on movements of the head. The measured values are referred to the different clinical syndromes and are described and divided according to its statistical significance related to the clinical groups.

Adolescent↗

Anterior surgery of the upper cervical spine.

The authors report the results obtained in a series of more than 80 cases submitted to 76 operations of the upper cervical spine by transoral approach with a minimum follow-up of two years. The cases include: 15 unstable fractures or non-union of the odontoid processes; 28 cases of post-traumatic instability of C1-C2 level without fracture of the odontoid process; 13 cases of rheumatoid arthritis with instability at C1-C2; 14 cases of severe anomalies of the craniovertebral junction, often associated with basilar impression and spinal cord compression, of which 7 cases presented with tetraparesis; 6 malignant tumors. The method used involves an anterior transoral approach, more often without tracheotomy, and with exposure of the anterior aspect of the atlas and of the odontoid process by means of a midline incision of the posterior wall of the pharynx. When spinal cord lesion was present, decompression and reconstruction by bone grafts taken from the iliac crest were performed. In nearly all of the cases osteosynthesis with an anterior plate was used. Complications were mild. There were two cases of infection, observed at the onset of our experience, which were resolved after removal of the instrumentation. There was loosening of a screw in three cases; this was eliminated through the digestive tube with no consequences. There were no early intra- or postoperative deaths. Consolidation was obtained in most of the patients, and only in three cases did we observe a loss of postoperative reduction. Among patients affected with tetraparesis we observed many cases of neurological recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Cervical Vertebrae↗

Treatment of basilar invagination by atlantoaxial joint distraction and direct lateral mass fixation.

OBJECT: The author discusses the successful preliminary experience of treating selected cases of basilar invagination by performing atlantoaxial joint distraction, reduction of the basilar invagination, and direct lateral mass atlantoaxial plate/screw fixation. METHODS: Twenty-two patients with basilar invagination-in which the odontoid process invaginated into the foramen magnum and the tip of the odontoid process was above the Chamberlain, McRae foramen magnum, and Wackenheim clival lines-were selected to undergo surgery. In all patients fixed atlantoaxial dislocations were documented. The 16 male and six female patients ranged in age from 8 to 50 years. A history of trauma prior to the onset of symptoms was documented in 17 patients. Following surgery, the author observed minimal-to-significant reduction of basilar invagination and alteration in other craniospinal parameters resulting in restoration of alignment of the tip of the odontoid process and the clivus and the entire craniovertebral junction in all patients. In addition to neurological and radiological improvement, preoperative symptoms of torticollis resolved significantly in all patients. The minimum follow-up period was 12 months and the mean was 28 months. CONCLUSIONS: Joint distraction and firm lateral mass fixation in selected cases of basilar invagination is a reasonable surgical treatment for reducing the basilar invagination, restoring craniospinal alignment, and establishing fixation of the atlantoaxial joint.

Adolescent↗