Classification of Congenital Scoliosis and Kyphosis: A New Approach to the Three-dimensional Classification for Progressive Vertebral Anomalies Requiring Operative Treatment

Noriaki Kawakami, MD; Taichi Tsuji, MD; Shiro Imagama, MD; Lawrence G. Lenke, MD; Rolando M. Puno, MD; Timothy R. Kuklo, MD


Spine. 2009;34(17):1756-1765. 

In This Article

Problems of 3D Analysis

There are many problems related to establishing a new classification of congenital spinal deformity by using 3D CT reconstruction images. First of all, high-resolution CT is absolutely necessary to obtain high quality images. A slice thickness of at least 2 mm is also inevitable although we are always aware of the amount of irradiation patients are exposed. To decrease the irradiation exposure, obtaining 3D CT images of whole spinal column seems to be not always necessary. However, some congenital vertebral malformation such as mismatched complex type may exists several normal-shaped vertebrae between 2 abnormal vertebrae. Scanning on the small area may misunderstand the type of vertebral anomalies. Secondary, the radiologic technicians should be well trained and know the volume-rendering technique because a false image may be constructed during image processing (Figure 13). Third, it is necessary for the spine surgeons evaluating 3D CT reconstructed images to become accustomed with this procedure, because it is still sometimes very difficult to analyze even high resolution images.

Figure 13.

The Process of Reconstruction of 3D CT Images.
During processing a reconstruction image of the bony skeleton, not bony structure are erased gradually following masking of the soft tissue. An image demonstrating the vertebrae and ribs without erasing the bony structure can be obtained at step of Hounsfield unit 110.

We should also understand the limitations of 3D CT reconstruction imaging. First, as mentioned earlier, the disc space and pedicle cannot be imaged because of the existence of rib heads in the thoracic spine. In this case, we need to add an evaluation of multiplanar reconstruction images (coronal and sagittal reconstruction images) besides the 3D CT images. Second, it is very difficult to determine whether the narrowed disc space derives from congenital or secondary means, or whether or not growth plate facing to the narrowed disc still has the potential to grow. Finally, even high-resolution image of 3D CT has limitations in demonstrating the demarcation of 2 structures, which are in contact without any space.


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