![]() The authors described four types of congenital vertebral anomalies: type 1: solitary simple type 2: multiple simple type 3: complex type 4: segmentation failure. This 3D imaging allows for the evaluation of several types of laminae that were consistently found, as well as provide a more detailed appreciation of severe deformities not possible with biplanar radiographs alone. Kawakami et al 6 proposed a three-dimensional (3D) classification for congenital scoliosis utilizing 3D computed tomography (CT) reconstructions. 3 An excellent illustration of these anomalies can be viewed in a previous congenital scoliosis review by Hedequist and Emans. An incarcerated hemivertebra has no intervening disc space between the adjacent vertebrae. A partially segmented hemivertebra is fused to the neighboring vertebra on one side with an open disc space on the opposite side. 2 , 4 A fully segmented hemivertebra possesses a normal disc both above and below the anomaly. There are three main types of hemivertebrae: fully segmented (65%), partially segmented (22%), and nonsegmented/incarcerated (12%). In contrast, a hemivertebra represents complete failure of formation of half the vertebra. A wedge vertebra represents partial failure of vertebral body formation on one side but maintains two pedicles. The unsegmented bar does not contain growth plates and therefore does not grow.įailure of formation produces either a wedge vertebra or a hemivertebra. A unilateral unsegmented bar is a bony bar fusing both the disc spaces and/or facets on one side of the spine. A unilateral bar typically occurs on the concave side of a curve. 4 A block vertebra results from bilateral segmentation defects with fusion of the disc spaces between the involved vertebrae. Segmentation defects involve bony bars between adjacent segments. 3 Approximately 80% of anomalies may be classified as either failures of segmentation or formation, with 20% being a mixed form. Congenital scoliosis is classically described as a failure of segmentation, formation, or a mixed form. ![]()
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