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PubMed2006

Skull base abnormalities in osteogenesis imperfecta: a cephalometric evaluation of 54 patients and 108 control volunteers.

OBJECT: Osteogenesis imperfecta (OI), which usually results from mutations in type I collagen genes, causes bone fragility and deformities. The head is often abnormally shaped, and changes in skull base anatomy in the form of basilar impression and basilar invagination have been reported. The authors analyzed the skull base anatomy on standardized lateral cephalograms from 54 patients with OI (Types I, III, and IV) and 108 control volunteers. They were surprised to find that the previously used diagnostic measures for basilar abnormality in patients with OI were exceeded in 6.5 to 7.4% of the controls, and hence needed to be reevaluated. METHODS: The authors calculated the distance from the odontoid process to four reference lines, including a novel one, in the controls. The normal mean distances were exceeded by more than two standard deviations (SDs) in 28.3 to 35.2%, and by more than three SDs in 13.2 to 16.6% of the patients with OI. The latter figures reliably reflect the prevalence of basilar impression. As a sign of basilar invagination the odontoid process protruded into the foramen magnum or reached the foramen magnum level in 22.2% of the patients with OI, whereas none of the controls showed this feature. Platybasia (an anterior cranial base angle > 146 degrees) was present in 11.1% of the patients but in none of the controls. CONCLUSIONS: Platybasia, basilar impression, and basilar invagination were often coexpressed, but each was also present as an isolated abnormality. These three abnormalities and wormian bones were predominantly found in OI Types III and IV as well as in patients exhibiting dentinal abnormality.

Adolescent↗
PubMed2000

Biomechanical rationale for the pathology of rheumatoid arthritis in the craniovertebral junction.

STUDY DESIGN: A finite-element model of the craniovertebral junction was developed and used to determine whether a biomechanical mechanism, in addition to inflammatory synovitis, is involved in the progression of rheumatoid arthritis in this region of the spine. OBJECTIVES: To determine specific structure involvement during the progression of rheumatoid arthritis and to evaluate these structures in terms of their effect on clinically observed erosive changes associated with the disease by assessing changes in loading patterns and degree of anterior atlantoaxial subluxation. SUMMARY OF BACKGROUND DATA: Rheumatoid arthritis involvement of the occipito-atlantoaxial (C0-C1-C2) complex is commonly seen. However, the biomechanical contribution to the development and progression of the disease is neither well understood nor quantified. Although previous cadaver studies have elucidated information on kinematic motion and fusion techniques, the modeling of progressive disease states is not easily accomplished using these methods. The finite-element method is well suited for studying progressive disease states caused by the gradual changes in material properties that can be modeled. METHODS: A ligamentous, nonlinear, sliding-contact, three-dimensional finite-element model of the C0-C1-C2 complex was generated from 0.5 mm thick serial computed tomography scans. Validation of the model was accomplished by comparing baseline kinematic predictions with experimental data. Transverse, alar, and capsular ligament stiffness were reduced sequentially by 50%, 75%, and 100% (removal) of their intact values. All models were subjected to flexion moments replicating the clinical diagnosis of rheumatoid arthritis using full flexion lateral plane radiographs. Stress profiles at the transverse ligament-odontoid process junction were monitored. Changes in loading profiles through the C0-C1 and C1-C2 lateral articulations and their associated capsular ligaments were calculated. Anterior and posterior atlantodental interval values were calculated to correlate ligamentous destruction with advancement of atlantoaxial subluxation. RESULTS: Model predictions (at 0.3 Nm) fell within one standard deviation of experimental means, and range of motion data agreed with published in vitro and in vivo values. The model predicted that stresses at the posterior base of the odontoid process were greatly reduced with transverse ligament compromise beyond 75%. Decreases through the lateral C0-C1 and C1-C2 articulations were compensated by their capsular ligaments. Anterior and posterior atlantodental interval values indicate that the transverse ligament stiffness decreases beyond 75% had the greatest effect on atlantoaxial subluxation during the early stages of the disease (no alar and capsular ligament damage). Subsequent involvement of the alar and capsular ligaments produced advanced atlantoaxial subluxation, for which surgical intervention may be warranted. CONCLUSIONS: To the best of the authors' knowledge, this is the first report of a validated, three-dimensional model of the C0-C1-C2 complex with application to rheumatoid arthritis. The data indicate that there may be a mechanical component (in addition to enzymatic degradation) associated with the osseous resorption observed during rheumatoid arthritis. Specifically, erosion of the odontoid base may involve Wolff's law of unloading considerations. Changes through the lateral aspects of the atlas suggest that this same mechanism may be partially responsible for the erosive changes seen during progressive rheumatoid arthritis. Anterior and posterior atlantodental interval values indicate that complete destruction of the transverse ligament coupled with alar and/or capsular ligament compromise is requisite if advanced levels of atlantoaxial subluxation are present.

Arthritis, Rheumatoid↗
PubMed2004

A critical analysis of the Chiari 1.5 malformation.

OBJECT: Although the traditional nomenclature used to describe hindbrain hernias is useful, there are certainly patients in whom these morphological entities do not strictly apply. One such group is composed of patients with the more recently described Chiari 1.5 malformation in which a Chiari I malformation is seen in combination with brain-stem herniation through the foramen magnum. In an attempt to elucidate further the best surgical strategy and to refine the descriptive terminology, the authors retrospectively analyzed all cases at their institutions in which this form of hindbrain herniation was diagnosed. METHODS: The authors reviewed the database for all patients in whom Chiari 1.5 malformation had been diagnosed. Each patient had undergone a posterior fossa decompressive surgery. Magnetic resonance images were evaluated for the extent of caudal descent of the brainstem, amount of tonsillar ectopia, inclination of the odontoid process, and any brain or brainstem abnormalities. Clinical presentations and postoperative results were correlated to the aforementioned radiological findings. Twenty-two patients were identified. The obex was a mean 14.4 mm inferior to the foramen magnum, and the medulla exhibited a flattened appearance in the midsagittal plane in all patients. Syringomyelia was documented in 50% of the cases. The cerebellar tonsils were found to lie at C-1 and C-2 in nine and 13 patients, respectively. The mean angulation of the odontoid process was 84.4 degrees. No abnormalities or caudal descent of the midbrain or pons was identified. Eighteen patients experienced resolution of preoperative symptoms. Persistence of syringomyelia prompted a second posterior fossa operation secondary to progressive scoliosis in 13.6% of the patients. CONCLUSIONS: No single sign or symptom was found to be peculiar to the Chiari 1.5 malformation, although all patients in whom this diagnosis was established had undergone a posterior fossa decompressive surgery. A significant number (13.6%) of patients required repeated operation for persistent syringomyelia. Neurosurgeons may wish to consider that many patients may not respond as well to posterior fossa decompressive surgery especially if syringomyelia is present.

Adolescent↗
PubMed1998

Cartilaginous development of the human craniovertebral junction as visualised by a new three-dimensional computer reconstruction technique.

Serial transverse histological sections of the human craniovertebral junction (CVJ) of 4 normal human embryos (aged 45 to 58 d) and of a fetus (77 d) were used to create 3-dimensional computer models of the CVJ. The main components modelled included the chondrified basioccipital, atlas and axis, notochord, the vertebrobasilar complex and the spinal cord. Chondrification of the component parts of CVJ had already begun at 45 d (Stage 18). The odontoid process appeared to develop from a short eminence of the axis forming a third occipital condyle with the caudal end of the basioccipital. The cartilaginous anterior arch of C1 appeared at 50-53 d (Stages 20-21). Neural arches of C1 and C2 showed gradual closure, but there was still a wide posterior spina bifida in the oldest reconstructed specimen (77 d fetus). The position of the notochord was constant throughout. The normal course of the vertebral arteries was already established and the chondrified vertebral foramina showed progressive closure. The findings confirm that the odontoid process is not derived solely from the centrum of C1 and that there is a 'natural basilar invagination' of C2 during normal embryonic development. On the basis of the observed shape and developmental pattern of structures of the cartilaginous human CVJ, we suggest that certain pathologies are likely to originate during the chondrification phase of development.

Basilar Artery↗
PubMed1997

Clinical course of conservatively managed rheumatoid arthritis patients with myelopathy.

STUDY DESIGN: The clinical course of rheumatoid arthritis patients with myelopathy who do not undergo surgery was studied. OBJECTIVES: To establish a more accurate prognosis for rheumatoid arthritis patients who do not undergo surgery. SUMMARY OF BACKGROUND DATA: Cervical myelopathy has been reported in two thirds of rheumatoid arthritis patients with atlantoaxial dislocation. Atlantoaxial fusion, or occipitocervical fusion, is widely performed on these patients. However, several researchers reported serious complications from the surgery, including nonunion, worsening myelopathy, and high mortality. The natural course of disease in rheumatoid arthritis patients with myelopathy should be known before definitive treatments can be outlined. MATERIALS AND METHODS: Twenty-one rheumatoid arthritis patients with myelopathy resulting from atlantoaxial dislocation were studied. Fourteen of the 21 cases were associated with upward migration of the odontoid process. All of these patients were recommended for surgery, but they refused. Patients were reviewed by direct examination yearly. Radiographic changes and clinical course, including the survival rate, were observed. RESULTS: Atlantodental interval and Redlund-Johnell measurements deteriorated. The patients showed no neural improvement, and deterioration was found in 16 (76%) cases during follow-up. All patients became bedridden within 3 years of the onset of myelopathy. Seven of the 21 patients died suddenly for unknown reasons, 3 died of pneumonia, and 1 died of multiple organ failure. The three sudden-death cases showed progressive upward migration of the odontoid process. The cumulative probability of survival was 0% in the first 7 years after the onset of myelopathy. CONCLUSIONS: The clinical results for rheumatoid arthritis patients with myelopathy treated without surgery are extremely poor. Surgical treatment is recommended for rheumatoid arthritis patients with myelopathy.

Activities of Daily Living↗
PubMed1983

Transoral operations for craniospinal malformations.

The transoral approach to the lower third of the clivus and to the ventral aspect of the upper cervical spine is used in craniospinal malformations with or without dislocation as well as in basilar aneurysms, ventrally situated cranio-spinal tumours, fractures of the odontoid process, and in rheumatoid arthritis compressing the spinal cord. In consideration of the literature and ten personal cases the indications and techniques of the transoral approach in craniospinal malformations are discussed. According to our own experiences and those of other authors it is possible to expose the lower clivus and the cervical spine down to C2 by a midline incision of the pharyngeal wall using a mouth retractor and oral intubation. Splitting of the soft palate or resection of the hard palate are not necessary, a tracheotomy should be performed only in exceptional cases. In congenital craniospinal malformations without dislocation or instability causing a ventral compression of the spinal cord, for instance by the odontoid process, the transoral decompression is preferable to dorsal decompressing operations. In cases of pure instability without any space-occupying lesion the transoral and posterior approach are possible in order to perform a fusion. The last one seems more advantageous in these cases. In craniospinal malformations with dislocation causing a ventral and dorsal narrowing of the spinal canal, apart from the decompression a stabilization has to be achieved. In these usually complex malformations individual treatment is necessary. According to the rare cases in the literature and to our own experience a primary anterior decompression, followed by a most careful posterior stabilization seems to produce the most favourable results.

Adult↗
PubMed1991

Atlantoaxial mobility after screw fixation of the odontoid: a computed tomographic study.

Between 1979 and 1989, anterior screw fixation of the odontoid process was performed in 16 patients with fractures of the odontoid. One patient died suddenly 2 days after the operation. Postmortem examination could not disclose the cause of death. No other complication was noted. We followed 13 patients. At examinations 7 to 82 months after injury, all fractures were consolidated in reduced position. In all patients, a functional computed tomographic (CT) examination of the atlantoaxial rotation was performed. Atlantoaxial rotation measurement ranged from 7 to 38 degrees to the right (average: 25.2 degrees) and 7 to 41 degrees (average: 24.1 degrees) to the left side. Five patients presented a normal range of atlantoaxial rotation, 29 to 41 degrees; 3 had a rotation of 20 to 28 degrees; 3 a rotation of 10 to 20 degrees; and in 2, rotation was less than 10 degrees to one side. Our results suggest that anterior screw fixation is the therapy of choice for Type II and cephalad Type III dens fractures. However, significant complications have been reported by other authors. Therefore, a careful surgical technique is mandatory, and contraindications should be respected.

Adolescent↗
PubMed1989

False-positive diagnosis of an odontoid fracture by CT scan.

Although computed tomography (CT) is a valuable tool for evaluating spine trauma, it's usefulness is limited. Horizontally oriented fractures of the cervical spine, particularly type 2 fractures at the base of the odontoid process, may be difficult to detect with CT. Our case report illustrates a false-positive diagnosis of this fracture and suggests that conventional polytomography is superior to CT for demonstrating this particular lesion when minimal displacement is present.

Adolescent↗
PubMed1996

Subdental synchondrosis fracture in children: the value of 3-dimensional computerized tomography.

A case is presented illustrating the usefulness of computerized tomography (CT) with 3-dimensional (3-D) reconstruction for evaluation of a subdental synchondrosis fracture in a child. Odontoid fractures in children less than 7 years of age occur at the subdental synchondrosis and are typically diagnosed with plain x-rays. However, a delay in diagnosis is common as these injuries may not be appreciated on initial roentgenographic evaluation. The authors present a case of a 2-year-old boy with a subdental synchondrosis fracture secondary to trauma. In this patient, plain x-ray and conventional axial CT failed to definitively elucidate the child's injuries; however, the use of CT with 3-D reconstruction fully delineated the injury. The use of CT with 3-D reconstruction in evaluating children with subdental synchondrosis fractures is a valuable tool for diagnosis. The treatment of synchondrosis fractures of the odontoid process in children is immobilization of the cervical spine.

Child↗
PubMed1985

Foramen magnum syndrome caused by a dolichoodontoid process.

A 21-year-old Japanese man with basilar impression with an anomalous configuration of the odontoid process and many other vertebral anomalies is reported. We thought that posterior decompression alone would be hazardous; therefore, in one session, the odontoid tip and anterior arch of the atlas were removed transorally, and posterior fixation between the occipital squama and the lamina of C-3 using acrylic plastic was performed. This treatment resulted in marked clinical improvement and required only a short hospital stay.

Adult↗
PubMed1999

Percutaneous anterior odontoid screw fixation technique. A new instrument and a cadaveric study.

We describe a new instrument and a percutaneous technique for closed anterior fixation of odontoid fracture. The instrument which we developed consists of a telescopic tube system. This new instrument and closed fixation technique was used in six cadavers with type II odontoid fractures and to two cadavers with an intact odontoid process. Each cadaver underwent satisfactory placement of the screw to the odontoid with this technique under biplanar scopy control. After this procedure, no serious injury was found in the parapharyngeal and neurovascular areas of the necks of the cadavers, in which anatomical dissection along the track of this instrument was performed. The instrumentation and the technique as a whole is seen as reliably applicable for odontoid fracture fixation. Also, we expect to reduce operating time and hospital costs because this system is simple, easily applicable and minimally invasive.

Bone Screws↗
PubMed1990

The laterally tilted dens: a sign of subtle odontoid fracture on plain radiography.

Type III (low) odontoid fractures may be subtle on initial plain film radiographic examination. We describe a sign on the routine open-mouth view, the laterally tilted dens, which has not been previously stressed in the radiologic literature, and is an important diagnostic sign of type III fractures of the odontoid process of the axis. In a series of 82 nontraumatized patients, no odontoid angle of less than 87 degrees (3 degrees from perpendicular) was observed. In a series of type III odontoid fractures, tilting of the dens in excess of 5 degrees was present in eight (67%) of 12 cases. This may be the only readily apparent finding on the initial cervical spine series. Of eight type III odontoid fractures in which an abnormal odontoid angle was identified, it was the only definite abnormality that could be recognized prospectively in two cases (25%) and that supported very subtle findings in two other cases (25%).

Adolescent↗
PubMed1999

Pathologic odontoid fracture and benign fibrous histiocytoma of bone.

We present the case of a 44-year-old female patient, who sustained an odontoid fracture after a minor trauma (uncomplicated fall). The radiologic evaluation revealed a skeletal tumor of the second cervical vertebra together with a fracture line at the base of the odontoid process of the axis. The patient underwent surgery, the tumor was resected and the odontoid was stabilised using an autologous cortico-cancellous bone graft and a halo fixator. Histologic examination revealed benign fibrous histiocytoma, which is reported to be a very rare skeletal tumor.

Adult↗
PubMed1994

Craniovertebral junction: normal anatomy, craniometry, and congenital anomalies.

The craniovertebral junction (CVJ) comprises the occiput, atlas, and axis and is visible in most magnetic resonance (MR) imaging studies of the brain. Craniometric measurements used in radiologic assessment of CVJ anomalies include the Chamberlain line, Wackenheim clivus baseline, Welcher basal angle, and atlantooccipital joint axis angle. Most anomalies of the occiput are associated with decreased skull base height and basilar invagination, the latter being a primary developmental anomaly in which the vertebral column is abnormally high and prolapsed into the skull base. Occiput anomalies include condylus tertius, condylar hypoplasia, basiocciput hypoplasia, and atlanto-occipital assimilation. Most atlas anomalies produce no abnormal CVJ relationships and are not associated with basilar invagination. These anomalies include aplasias, hypoplasias, and clefts of the atlas arches and "split atlas" (ie, posterior arch rachischisis associated with anterior arch rachischisis). Except for fusion anomalies, abnormalities of the axis are primarily confined to the odontoid process and are not associated with basilar invagination. These anomalies include persistent ossiculum terminale, odontoid aplasia, and os odontoideum. With the widespread availability of MR imaging, which is well suited for evaluating the CVJ because of its direct sagittal imaging capabilities, renewed understanding of CVJ anatomy and anomalies is important for all radiologists.

Adolescent↗
PubMed1993

Biomechanics of odontoid fracture fixation. Comparison of the one- and two-screw technique.

Direct anterior screw fixation of odontoid fractures has become more prevalent clinically. No biomechanical study, however, has determined whether one or two screws should be used. This study measured the stability of the odontoid process after fracture and internal fixation with one or two screws. Internal fixation of Type II odontoid fractures did not restore the original stability of the intact specimen, direct internal fixation with one or two screws provided 50% of the stability of the unfractured odontoid, and no significant differences between the one- and two-screw technique was found under loading to failure, although the two-screw technique provided increased stiffness in extension loading.

Biomechanical Phenomena↗
PubMed2002

Retro-odontoid pseudotumor in diffuse idiopathic skeletal hyperostosis.

STUDY DESIGN: A rare case of retro-odontoid pseudotumor combined with diffuse idiopathic skeletal hyperostosis is presented. OBJECTIVE: To discuss the pathomechanism of retro-odontoid pseudotumor in diffuse idiopathic skeletal hyperostosis. SUMMARY OF BACKGROUND DATA: Reports describing craniovertebral manifestations of diffuse idiopathic skeletal hyperostosis are quite rare. Only two cases of an atlantoaxial subluxation and one case of an odontoid fracture have been reported. Myelopathy resulting from retro-odontoid pseudotumor combined with diffuse idiopathic skeletal hyperostosis has not been reported previously. METHODS: A 74-year-old man presented with spastic tetraparesis caused by a retro-odontoid pseudotumor combined with diffuse idiopathic skeletal hyperostosis. Transoral removal of the extradural mass combined with a dorsal atlantoaxial fusion was performed using a titanium frame with sublaminar cable wiring. RESULTS: Yellowish amorphous material extruded from between the odontoid process and the arch of C1 when the anterior capsule had been incised. The retro-odontoid mass was very firmly attached to the hypertrophied ligaments. The mass therefore had to be sharply dissected away to expose the dura. The histologic appearance of the mass consisted of poorly cell-degenerated ligament, fibrocartilage, and fibrin. There was a focal proliferation of small vessels, but no significant inflammatory component and no evidence of neoplasia. The ligaments appeared fibrillated, disintegrated, and fragmented. After surgery, the patient's neurologic function improved. CONCLUSIONS: This is the first reported case of a retro-odontoid pseudotumor combined with diffuse idiopathic skeletal hyperostosis. The secondary transfer of mechanical stress to the atlantoaxial segment was presented as a pathomechanism underlying the formation of this retro-odontoid pseudotumor.

Aged↗
PubMed1993

A biomechanical study of odontoid fractures and fracture fixation.

The purpose of this study was to measure the stability of the odontoid process after fracture and subsequent screw fixation. To accomplish this, we mechanically reproduced Type II and Type III odontoid fractures on isolated C2 vertebrae by varying the direction of load. These fractures were subsequently stabilized with a single 3.5 mm screw and retested for multidirectional stability and load to failure. Reduced and instrumented specimens were found to have a stiffness equivalent to one half of that of the unfractured odontoid. Load to failure was also slightly less than one half of the original fracture force (average 160 lb). Screw failure was by a cut-out mechanism in all Type III fractures and by bending of the screw in all Type III fractures. Our findings, in conjunction with the existing literature, strongly suggest that Type III fractures result from extension forces, whereas Type II fractures result from lateral or oblique loading forces. Single screw fixation of an odontoid fracture will provide stability equal to approximately one half that of the unfractured bone.

Aged↗