Posterior Synchondrosis Research Articles

Foramen Magnum Stenosis in Achondroplasia

Achondroplasia is the most common hereditary skeletal dysplasia and is characterized by disproportionately short stature with rhizomelic short extremities [1]. The skull features include a narrowed foramen magnum, short skull base, and clivus [2]. Foramen magnum stenosis is a characteristic funding, secondary to an abnormal placement and premature fusion of the posterior synchondroses [1]. The second factor responsible for stenosis is a defect in endochondral ossification in the basiocciput that may result in an extension of the squamous occipital bone [2]. It can cause hydrocephalus and prominent emissary and meningeal veins (Figure 1). Figure 1: Sagittal T1WI revealing a narrowed stenosis of the foramen magnum and compression of the cervicomedullary junction. The most severe complication is the compression of the cervicomedullary junction, associated with severe morbidity and sudden death in younger children [1].

Sex-Related Differences in the Developmental Morphology of the Atlas: A Computed Tomography Study.

A retrospective study. To elucidate sex-related differences in the age at synchondroses closure, the normative size of the atlas, and the ossification patterns of the atlas in Japanese children. The atlas develops from three ossification centers during childhood. The anterior and posterior synchondroses, which are separate ossification centers, mimic fracture lines on computed tomography (CT). Sex-related differences of age dependent morphological changes of the atlas in a large sample size have not been reported. This study analyzed data of 688 subjects (449 boys) between 0 and 18 years old who underwent CT examination of the head and/or neck between January 2010 and July 2016. The age at synchondroses closure, anteroposterior outer, inner, and spinal canal widths of the atlas, and variations of the ossification centers were examined. Anterior synchondroses closed by 10 years in boys and by 7 years in girls. Significant earlier closure of anterior synchondroses was observed in girls than in boys (P < 0.05 at 4 and 5 years old). Posterior synchondrosis closed by 6 years in boys and by 5 years in girls. The outer, inner, and spinal canal widths increased up to 10 to 15 years in both sexes, although all three parameters in girls peaked 3 years earlier than those in boys. All parameters in boys were significantly larger than those in girls, except in the 10- to 12-year-old age category. Two or more ossification centers in the anterior arch were observed in 18.3% subjects, and 6% had midline ossification centers in the posterior arch of the atlas. Distinct sex-related differences in the age at anterior synchondroses closure and the size of the atlas were observed in Japanese children. Knowledge of morphological features of the atlas could help distinguish fractures from synchondroses. 3.

Geometrical Properties of the Human Child Cervical Spine With a Focus on the C1 Vertebra

Objective: Child dummies and injury criteria used in automotive crashworthiness environments are based on scaling from the adult and/or between children of different ages. Cartilage-to-bone ossification, spinal canal and joint developments of the spine, and strength attainments do not grow linearly from birth to maturity. Though this is known to medical professionals, age-based quantitative analyses are needed to accurately model the pediatric spine. The objective of this study was to quantify longitudinal growths of various regions of the first cervical vertebrae, responsible for transmitting the axial load from the base of the skull through the condyles to the neck/torso. Methods: Computed tomography (CT) images of 54 children from one day to 18 years of age were retrospectively used to determine the following geometrical properties: bilateral neurocentral synchondroses widths, the width of posterior synchondrosis, outer and inner anteroposterior and transverse diameters, spinal canal area, and depths of the anterior and posterior arches of the C1 vertebra. Both axial and sagittal CT images were used in the analysis. Sagittal images were used to quantify data for the anterior and posterior arches and axial images were used for all described cross-sectional parameters. Results: Geometrical properties were extracted and reported for the various parameters at 6 months; one year; 18 months; and 3, 6, and 10 years of age corresponding to the dummy family ages routinely used in motor vehicle crashworthiness research and other applications. The outer transverse diameter ranged from 4.97 to 7.08 cm; outer and inner antero-posterior diameters ranged from 2.99 to 4.18 and 2.19 to 3.03 mm; and spinal canal area ranged from 4.34 to 6.68 mm2. Other data are given in the body of the article. The growths of the first cervical vertebra quantified in terms of the above variables occurred nonlinearly with age and the degree of nonlinearity depended on the type of the geometrical parameter. Growths did not match with the simple scaling ratios based on the adult spine, used in different studies reported in the current literature. Conclusions: These early nonlinear and nonuniform age- and local geometry–specific variations should be considered in human finite element models for an accurate transfer of the external load from the atlas to the subaxial spine and to improve their fidelity and biomechanical capabilities.

Developmental Morphology and Ossification Patterns of the C1 Vertebra

The first cervical vertebra (C1) is a unique ring-shaped structure and is largely cartilaginous at birth. Our objectives were to retrospectively analyze the age of closure of the synchondroses and determine age-dependent morphological characteristics of the C1 vertebra using computed tomographic (CT) scans. Helical CT scans were made in fifty-four children as part of routine imaging of patients presenting to the emergency room with head injury, to exclude cervical spine trauma. Axial and sagittal reconstruction images of the C1 ring were analyzed for widths of the anterior and posterior synchondroses, outer and inner anteroposterior diameters, outer and inner transverse diameters, inner area of the spinal canal at C1, and heights of the anterior and posterior arches. Variations in these parameters were evaluated in age groups from infancy to eighteen years. As ossification progressed, the widths of the anterior neurocentral and posterior synchondroses decreased with increasing age. Closure of the posterior synchondrosis was complete in all by thirty-six months, except in one fifty-five-month-old subject in whom the posterior synchondrosis was open. Closure of the anterior synchondrosis was generally found after thirty-six months. Growth of the mean outer and inner anteroposterior diameters, mean outer transverse diameter, and increase in canal area occurred with age up to the three to six-year group, following which measurements increased minimally or stayed relatively constant. The inner transverse diameter was largely unchanged from birth to maturity and appeared to be independent of age. Anterior and posterior ring heights showed a similar distribution, with an increase up to the nine to twelve-year age group, and relatively constant values thereafter. Data from this retrospective review of fifty-four CT scans of the cervical spine, weighted toward the youngest population, assist in understanding the age-dependent osseous anatomy and biomechanical stability of the C1 vertebra in the growing child, help to distinguish fractures from incomplete ossification, and help to formulate decisions on the use of internal fixation of C1 in the growing child.

Ossification Patterns of the Atlas Vertebra

The objective of this study was to characterize ossification patterns of the C1 (atlas) vertebra in children, to better differentiate normal variants from traumatic injury. A retrospective review of all sinus and temporal bone CT examinations was performed for the period of 2002-2009. Patients 96 months old or younger for whom C1 level was at least partially imaged were included. Patients with a history of trauma or genetic disorder-associated spinal abnormalities were excluded. A total of 1270 CT examinations were reviewed. The anterior arch of C1 was completely imaged in 841 patients (66%), and the posterior arch was completely imaged in 378 patients (30%). Multiple anterior arch ossification centers were observed in 179 of 841 patients (21%), and posterior arch variants were present in nine of 378 patients (2%). At least partial ossification of the anterior arch was seen in 113 of 147 children (77%) younger than 25 months, whereas only 14 of the remaining 694 children (2%) older than 24 months failed to show any ossification. Incomplete ossification of the anterior arch was noted in 47 of 103 patients (46%) in the 85-96-month-old category. The posterior arches were at least partially ossified in all children. Incomplete fusion of the posterior synchondrosis was seen in 17 of 108 patients (16%) older than 60 months. C1 ossification patterns and timing of synchondrosis fusion are variable. Knowledge of these patterns is important to better differentiate a normal variant from traumatic injury.

Jefferson fractures of the immature spine

Jefferson fractures of the immature spine have received little attention in the study of pediatric spinal trauma. Fractures through synchondroses are a possibility in the immature spine, in addition to fractures through osseous portions of the vertebral ring, and they create opportunities for misinterpretation of diagnostic imaging. The authors describe 3 examples of Jefferson fractures in young children. All 3 cases featured fractures through an anterior synchondrosis in association with persistence of the posterior synchondrosis or a fracture of the posterior arch. The possibility of a Jefferson fracture should be considered for any child presenting with neck pain, cervical muscle spasm, or torticollis following a head injury, despite a seemingly normal cervical spine study. Jefferson fractures in young children are probably much more common than previously recognized.

Fractures of C1 and C2 in an Infant Gazelle

Summary: Spontaneously occurring fractures of the anterior and posterior synchondroses of C1 and the superior facet of C2 of an immature mammal were analyzed. The posterior C1 injury showed comminution, with involvement of both sides of the synchondrosis. Just below the anterior C1 fracture was an incomplete, comminuted fracture of the C2 superior facet. These fractures, especially the C1 injury, appear similar to the radiographic injury patterns in skeletally immature humans. Presumably the histologic failure patterns in the child would also be similar.

Fractures of C1 and C2 in an Infant Gazelle

Spontaneously occurring fractures of the anterior and posterior synchondroses of C1 and the superior facet of C2 of an immature mammal were analyzed. The posterior C1 injury showed comminution, with involvement of both sides of the synchondrosis. Just below the anterior C1 fracture was an incomplete, comminuted fracture of the C2 superior facet. These fractures, especially the C1 injury, appear similar to the radiographic injury patterns in skeletally immature humans. Presumably the histologic failure patterns in the child would also be similar.

Radiology of postnatal skeletal development. XI. The first cervical vertebra.

Forty-four first cervical vertebra were removed from cadavers and skeletons ranging in age from full-term neonates to 14 years. These were studied roentgenographically to duplicate antero-posterior and transverse appearances without superimposition of the skull or other vertebra. Ossification was present in both posterior (neural) arches at birth. These ossification centers extended toward the rudimentary spinous process to form the posterior synchondrosis. Each also extended anteriorly into the articular facet region. The posterior ossification centers formed all the bone present in the facets. Anteromedial to each facet a neurocentral synchondrosis formed on each side of the expanding anterior ossification center. The anterior ossification center appeared between six months and two years. Normally a single center formed. However anterior ossification was some-times multifocal. Infrequently the posterior centers extended into the anterior arch and met as a single anterior synchondrosis. By four to six years the posterior synchondrosis and the anterior neurocentral synchondroses were fused. All three synchondroses fused at approximately the same time, although the posterior one often slightly preceded the anterior ones. Accordingly, the spinal canal of C1 reached maximum size at this stage of development. Further growth was then limited to periosteal addition on the external surface, leading to thickening and increased height, but without significantly altering the size of the spinal canal.