![]() ![]() With true subluxation, the posterior C2 arch does not fall within 2 mm from the Swischuk line.Ĭonstitutional Variants: Occipitalization (assimilation) of the atlas is the osseous fusion of the atlas and the occiput. Pseudosubluxation may be differentiated from true subluxation by the posterior spinolaminar line, which connects the anterior cortices of the posterior C1 and C3 arches (Swischuk line). Pseudosubluxation: Physiologic motion of C2 on C3 in flexion with anterior displacement of C2 measures up to 4 mm in children under 8 years of age. The atlanto-dental interval should be normal with this pseudospread of atlas. “Pseudo-Jefferson Fracture”: Lateral offset of the C1 lateral masses compared to the lateral masses of the axis of up to 6 mm is normal in children (due to discrepancy in growth rates). If greater than 5 mm, ligamentous abnormalities need to be excluded by MRI to depict bone edema and/or ligamentous injury. Additionally, the x-ray beam should be completely perpendicular to the region of interest in order to decrease pitfalls.Ītlanto-Dental Interval: Distance between the anterior aspect of the dens and the posterior cortex of the anterior C1 ring should be less than 5 mm. If the image is taken supine, lift the patient’s shoulders from the table, because the relatively larger head of a child can diminish the lordosis. This will allow visualization of the patient’s definite cervical lordosis, which can be falsely underestimated in a supine position. In order to avoid interpretation errors, the radiographs should be obtained with neck extended and in inspiration, the patient awake in the standing or seated position, if possible. The normal prevertebral space should not be greater than 6 mm at the level of C3 however, marked buckling of the soft tissues occurs with neck flexion and in expiration. The vertebral bodies may later have anterior wedging, especially at the C3 level, which is normal in children up to 7 years of age.Įxamine the prevertebral/retropharyngeal space swelling in conjunction with the other findings. The shape of the normal vertebral body in infancy is oval on lateral view radiographs, sagittal CT reformats, and sagittal MRI. The neural arches fuse posteriorly by 2–3 years and the odontoid fuses at 3–6 years. This fusion line is called the subdental synchondrosis and can be seen up until 11 years and even later. The body of C2 fuses with the odontoid by 3–6 years. C2: Ossification center at the odontoid apex, the os terminalis or os odointoideum, normally fuses by 12 years. C1: Anterior arch fuses at 7 years while the neural arches fuse posteriorly at approximately 3 years. A normal physis can be identified by the presence of its smooth borders with subchondral sclerotic lines. Baseline radiographic studies of the cervical spine are indicated in all DS children older than 5 years of age and should be considered in all DS adults, particularly those 30 years of age and older.The craniovertebral junction ossification centers should be understood in order to prevent their misinterpretation as fractures. In all cases any complaints of cervical pain or historical/clinical findings suggestive of neurologic involvement should initiate evaluation of the cervical spine. In both the DS child and the DS adult, the cervical spine may be an area of significant potential problems. A review of the cervical spine radiographs of adults with DS, between 26 and 42 years of age, showed no subluxation but significant degenerative changes of the cervical spine with spur formation, narrowing of foramina, narrowing of the disc inner space, and osteophyte formation. This is in general agreement with previously reported ranges of 10 to 20 percent. A review of the radiographs of 34 individuals with Down syndrome (DS), between 5 and 21 years of age, demonstrated subluxation of atlantoaxial instability (C1-C2) greater than 5 mm in three of the 34 individuals (9 percent). ![]()
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