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PubMed2001

Biomechanical study of C2 (Axis) fracture: effect of restraint.

INTRODUCTION: In human, the cervical spine region is very susceptible to impact injury. The complex structures of C1 and C2 serve to transmit the weight of the cranium to the greatly similar structural cervical spine from C3 caudally. Application of sudden disruption forces will detach the junction of the cervico-cranium with the pars interarticularis of the neural arch of C2 from the lower cervical spine by fracturing, as in a "hangman's fracture". Severe falls or blows to the head from heavy objects will cause the fracture of the odontoid process of C2. Many biomechanical studies were conducted based on full restraint of the inferior aspects of isolated C2 to produce odontoid fracture. In this study, two different restraining conditions of C2 were adopted experimentally to determine the absolute fracture load and the corresponding fracture patterns that are common to C2. MATERIALS AND METHODS: Nine C2 vertebrae obtained from cadaver spines, ranging from 51 to 80 years, were used. Two specified restraint conditions were employed: (1) fully constrain the posterior element postero-anteriorly up to one-quarter of the inferior facet; and (2) fixing of C2 by a specially-designed rig whereby the body of C2 embedded in the pivoted cup and its inferior facets positioned on top of two lateral plates. Antero-posterior shear force was applied on the anterior articulating facet of the dens until failure. RESULTS: These specified restraint conditions had resulted in specific fracture of C2. Antero-posterior shear force ranges from 840 to 1220 N was required to cause fracture across the pars interarticularis under restraint condition 1. Failure load of between 900 and 1500 N was found to cause odontoid fracture under restraint condition 2. These values are in agreement with published data. CONCLUSIONS: The biomechanical response of C2 was specific to the mode of restraint conditions of C2. In reality, depending on the force vector applied to the head, precise posture at the time of trauma, spinal geometry, and physical properties, different types of C2 fracture patterns may happen. These findings are of potentials for the biomechanical correlation and validation study of C2 vertebra using analytical approaches, and in the surgical anterior screw fixation of odontoid fracture.

Aged↗
PubMed1980

[Variants of congenital hypoplasia of the arches of the upper cervical vertebrae and their clinical significance].

A clinico-roentgenological examination of the transitional craniovertebral division has revealed a high incidence and a great diversity of isolated underdevelopment of the arches of the upper cervical vertebra--from their fissure-like splitting to complete absence. Usually these forms create no preconditions for disturbances of any functions, do not manifest clinically, and can be regarded as variants of normal structure of the craniovertebral division.

Abnormalities, Multiple↗
PubMedDate not supplied

[Acute torticollis and its roentgen analysis].

It has hitherto been assumed without exception that A-P films of acute torticollis demonstrate neither malposture nor subluxation or (worse still) luxation of the atlas. In contrast, there is ventral subluxation of the atlas in all cases, although in about one-half of them this only become manifest in ventral flexion, with a tendency to form an angle between the odontoid process and the first cervical vertebra. In conformity with the head posture in acute torticollis, X-ray findings in the head joints are normal on A-P films. Fundamental to acute torticollis is that when the head is held in certain positions -- lateral inclination with rotation, sometimes combined with tilting of the head -- spontaneous, occasionally gradual obstruction of rotation of the atlas (and more rarely of the axis) occur; as a result, the head has to be held in these positions by force. In attempts to equalize head posture temporarily, lateral shifting of the atlas quite frequently occurs; depending on atlas rotation and the statics of the cervical spine, it may be either physiological or pathologic.

Acute Disease↗
PubMed1977

An unusual atlanto-axial dislocation. Case report.

A case is presented in which the patient sustained a complete dislocation of the odontoid process in front of the anterior arch of the first cervical vertebra. There was no fracture of the arch of C-1 vertebra. The patient was treated successfully by trans-oral excision of the odontoid process and the anterior arch of C-1. Twenty days later the patient's spine was stabilized posteriorly at C-1 through C-3 with wire and methyl-methacrylate.

Aged↗
PubMed2004

Kinematics of the upper cervical spine in rotation: in vivo three-dimensional analysis.

STUDY DESIGN: Kinematics of the upper cervical spine during head rotation were investigated using three-dimensional magnetic resonance imaging (MRI) in healthy volunteers. OBJECTIVES: To demonstrate in vivo intervertebral coupled motions of the upper cervical spine. SUMMARY OF BACKGROUND DATA: Although various in vivo and in vitro studies have identified the normal movement patterns of the upper cervical spine, no previous studies have accurately analyzed in vivo three-dimensional intervertebral motions of the upper cervical spine during head rotation. METHODS: Fifteen healthy volunteers underwent three-dimensional MRI of the upper cervical spine using a 1.0-T imager in progressive 15 degrees steps during head rotation. Segmented three-dimensional MRIs of each vertebra in the neutral position were superimposed over images taken at other positions, using voxel-based registration. Relative motions between occiput (Oc) and atlas (C1) and between C1 and axis (C2) were measured and described with 6 degrees of freedom by rigid body Euler angles and translations. RESULTS: Mean (+/- SD) maximum angles of axial rotation in Oc-C1 and C1-C2 were 1.7 +/- 1.5 degrees and 36.2 +/- 4.5 degrees to each side, respectively. Increases in angle of axial rotation in C1-C2 became smaller with increased head rotation, indicating axial rotation in C1-C2 displayed nonlinear motion. Coupled lateral bending with axial rotation was observed in the direction opposition to that of axial rotation in Oc-C1 (mean, 4.1 +/- 1.4 degrees) and C1-C2 (mean, 3.8 +/- 3.0 degrees). Coupled extension with axial rotation occurred at both C0-C1 (mean, 13.3 +/- 4.9 degrees) and C1-C2 (mean, 6.9 +/- 3.0 degrees). CONCLUSIONS: We developed an innovative in vivo three-dimensional motion analysis system using three-dimensional MRI. In vivo coupled motions of the upper cervical spine investigated using this system supported the results of the previous in vitro study.

Adult↗
PubMed1986

Hangman's fracture in an infant.

A case is reported of fracture of the pedicles of the axis vertebra in an infant. Non-operative management in a Minerva cast resulted in union and full recovery without complications.

Axis, Cervical Vertebra↗
PubMed2000

Curvature and range of motion of the cervical spine after laminaplasty.

BACKGROUND: The curvature and range of motion of the cervical spine decrease after laminaplasty. However, to our knowledge these changes have not been studied prospectively. Also, the effect of laminaplasty on the mobility of the occipito-atlanto-axial joints has not been studied in detail. The purpose of our study was to prospectively evaluate the range of motion and curvature of the cervical spine, including the occipito-atlanto-axial joints, following laminaplasty. METHODS: We conducted a prospective study of twenty-six patients who underwent cervical laminaplasty. They were followed for a mean of 6.7 years (range, five to nine years). Radiographs were made before the operation and at one, three, and five years after the operation. The curvature index, the angle of each vertebra in the neutral position from the occiput to the seventh cervical vertebra, and the range of motion in the sagittal plane were measured. RESULTS: The curvature index, the angle of the axis and the sixth cervical vertebra, and the angle of the axis and the seventh cervical vertebra in the neutral position were reduced after the operation. The rate of reduction declined between the third and fifth postoperative years. On the other hand, the mean distance between the occiput and the atlas as well as the mean angle of the axis and the atlas did not change significantly. The range of motion of the axis and the seventh cervical vertebra was decreased after the operation, and it continued to decrease slowly over the study period. The range of motion of the occipito-atlanto-axial complex increased slightly, which may represent a compensation for the decreased mobility of the middle and caudad parts of the cervical spine. CONCLUSIONS: Laminaplasty diminishes lordosis and straightens the cervical spine. The range of motion and lordosis continued to decrease, though at a diminishing rate, between the third and fifth postoperative years.

Adult↗
PubMedDate not supplied

Fractures of the second cervical vertebra: Internal fixation by interlaminar wiring.

Fractures of the 2nd cervical vertebra are frequently undetected on initial evaluation. Tomography may be necessary to delineate the fracture. This is a report of 20 patients treated by internal fixation using interlaminar wiring. There was no operative mortality. Follow-up studies, an average of 25 months after operation, demonstrated satisfactory results and no evidence of delayed neurological deficit.

Adolescent↗
PubMed1989

Traumatic spondylolisthesis of the axis.

Hanging, a common method of execution, began in antiquity and continues to this date. Unfortunately, the exact cause of a victim's demise was not always obvious, and many victims died as the result of asphyxiation from the hangman's noose. In the latter part of the 19th century, scientific curiosity led to autopsy studies of the cervical spine; Paterson in 1890 first described the lethal lesion. Experimental work in 1913 demonstrated that when the hangman's knot was placed beneath the chin, death rapidly occurred because of a traumatic spondylolisthesis of the second cervical vertebra. This knot placement then became standard as the most efficient method of execution. It was not until the mid-20th century that the similarity between judicial and civilian injury was recognized. The reports were infrequent, and most of the pars interarticularis fractures resulted from automobile accidents in which the victim was thrown forward and struck his or her face against the windshield which caused sudden violent hyperextension. The similarity between civilian and vehicular injuries was recognized in 1965 by Schneider who, together with his associates, reported eight cases; it was this group who introduced the term "hangman's fracture". Garber presented his thoughts on this subject, noting that there was a difference between the forces generated by judicial hanging and those caused by motor vehicle accidents and other similar civilian injuries. The former results in axial loading and hyperextension, and, rarely, in flexion or axial loading. Since the lesion occurs at the pars interarticularis of C2, Garber suggested that a more appropriate term might be traumatic spondylolisthesis of the axis.

Axis, Cervical Vertebra↗
PubMed1991

Cervical vertebral dimensions in 8-, 11-, and 15-year-old children.

In a sample of 107 boys and girls registered at 8, 11, and 15 years of age and 22 adults the statural height and the height and length of the cervical vertebrae, measured from lateral skull radiographs, were studied. The height and length of the vertebrae increased with age among the children and were non-significantly higher for the girls in each age group. The 15-year-old girls matured earlier, reaching adult values at this age. The 15-year-old boys still showed significantly smaller values for vertebral height and length compared with the adult men. Statural height was significantly correlated with the variables for vertebral growth at 8 and 11 years, whereas there was no correlation at 15 years of age among the children who had passed the pubertal peak height. The development of the vertebrae showed similarities with earlier reported skeletal maturity indicators found in the hand-wrist area and could as such offer an alternative method of assessing maturity without the need for hand roentgenograms.

Adolescent↗