E F
E, A 5-year-old boy. The vertebral body margins appear more square. The neural arches have fused to the vertebral bodies, a process that normally occurs between the ages of 4 and 6 years. F, A 13-year-old boy. The vertebral bodies are more rectangular.
The secondary ring apophyses of the vertebral bodies have begun to appear (arrows). These typically begin to ossify at puberty, although such ossifi cation may be apparent as early as 7 years of age. These secondary ring apophyses usually fuse to the vertebral bodies between the ages of 17 and 25 years.
FIGURE 3–2, cont’d
TABLE 3-2 Developmental Anomalies, Anatomic Variants, and Sources of Diagnostic Error Affecting the Thoracic Spine*
Entity Figure(s) Characteristics
Normal ring apophyses4 3-1 to 3-3 Normal vertebral body ring apophyses may resemble fractures or limbus vertebrae Hahn venous channels5 3-4 Normal anatomy: a central horizontal vascular groove or channel that traverses the
vertebral body
These channels are quite prominent beginning with the fi rst year of life but tend to disappear with age; even when they persist into adulthood, they are of no clinical signifi cance
Spina bifi da occulta6 3-5 Extremely common developmental anomaly consisting of a midline defect within the neural arch in which the two laminae fail to fuse centrally at the spinolaminar junction
Spina bifi da occulta results in a radiolucent cleft, or an absent spinous process, or both; it occurs most frequently at the L5-S1 and T11-T12 levels
Seen as an isolated anomaly or in conjunction with other entities, such as congenital spondylolisthesis, cleidocranial dysplasia, or Klippel-Feil syndrome
Cleft usually is occupied by strong cartilage and fi brous tissue and generally is of no clinical consequence
Spina bifi da may infrequently be associated with meningomyelocele, which represents protrusion of the meninges or spinal cord, or both; meningomyelocele may result in severe neurologic abnormalities
Hemivertebra7,8 3-6; see 3-17 Vertebral body originally develops from paired chondral centers, which at a later stage form a single ossifi cation focus that is separated transiently by the notochordal remnant into anterior and posterior centers
Lateral hemivertebra results from failure of development of one of the paired chondral centers
Lateral hemivertebra might involve a normally occurring vertebra or it might be supernumerary; one pedicle may be normal or enlarged and its counterpart at the same level may be absent or hypoplastic; the incomplete segment may articulate with or be fused to the adjacent vertebra
Frequently results in congenital scoliosis and may be associated with segmentation anomalies
Dorsal and ventral hemivertebrae result from agenesis of either the anterior or posterior portion of the growth center, respectively; these occur much less frequently than lateral hemivertebrae
Butterfl y vertebra8 3-7 Incomplete fusion of the two lateral chondral centers of the vertebral body results in a central sagittal constriction of the vertebral body, which is seen on a frontal radiograph and is considered a variant of enchondral ossifi cation
Interpedicle distance of the butterfl y vertebra may be widened, and the adjacent vertebrae usually remodel to conform to the shape of the butterfl y vertebra Synostosis (block vertebra)8 2-31, 4-6 Developmental failure of segmentation of vertebral somites with subsequent fusion of
adjacent vertebrae
Often results in premature degenerative disease at adjacent vertebral levels owing to excessive intervertebral motion above and below the synostosis
Findings include waistlike constriction at the level of the intervertebral disc; complete absence of disc space or a disc represented by a rudimentary, irregularly calcifi ed structure; total height of the block vertebra is less than expected from the number of segments involved; fusion of the posterior elements (50% of cases)
Differential diagnosis: surgical fusion or ankylosis from infl ammatory arthropathy or previous infection
Tracheal cartilage calcifi cation7 3-8 Normal physiologic calcifi cation of cartilaginous tracheal rings; no clinical signifi cance
* See also Table 1-1.
FIGURE 3–3
Normal ring apophyses.4 Small triangular ossifi cation centers are present at the anterosuperior and anteroinferior corners of the vertebral bodies in this 15-year-old boy. Notching and round- ing of the adjacent corners of the vertebral bodies also are evident.This appearance of the normal vertebral body ossifi cation centers should not be confused with fractures or limbus vertebrae.
FIGURE 3–4
Hahn venous channels.5 Horizontal radiolucent grooves through the central portion of the vertebral bodies (arrows) are seen most frequently in the lower thoracic spine and represent residual venous sinus channels that accommodate vertebral veins.FIGURE 3–5
Spina bifi da occulta.6 Midline vertical radiolucent clefts in the thoracolumbar region (arrows) represent failure of union of the paired ossifi cation centers of the neural arches.FIGURE 3–6
Lateral hemivertebra.7,8 Observe the triangular appearance of the vertebral body in the lower thoracic spine. The anomalous vertebra possesses two pedicles and costovertebral articulations on the left and one pedicle and costovertebral articula- tion on the right, resulting in a congenital scoliosis. (Courtesy A.Manne, DC, Minneapolis.)