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

Disclosures

Spine. 2009;34(17):1756-1765. 

In This Article

An Approach to a New 3D Classification of Congenital Spinal Deformity

For the last 20 to 30 years, the classification of congenital scoliosis and kyphosis on which we developed an operative strategy for the treatment of the deformity remains the same. Many spine surgeons have encountered vertebral anomalies whose operative findings did not fit with plain x-ray findings. Once 3D analysis of the deformed vertebrae becomes possible, referring to the findings of their 3D morphology becomes inevitable for the correction of congenital spinal deformity with osteotomy. However, because of the ambiguous definition of synostosis observed in many malformed vertebrae and the detection of discordant anomalies, we need to revise the classification of congenital spinal deformity by including new information obtained by 3D analysis.

To make the story much simpler, analysis of congenital spinal deformity should be determined by orders of evaluation. The first step is counting the number of congenitally deformed vertebrae and dividing them into solitary and multiple. The second step is the analysis of formation failure of deformed vertebrae, such as the type of anterior and posterior formation failure, the site, the laterality, and the existence of discordance. The next step is the analysis of segmentation failure of abnormal vertebrae that have been already evaluated, according to the type of formation failure ( Table 1 ). If deformed vertebrae do not exhibit any signs of formation failure, the type of congenital vertebral anomaly surely belongs to the pure segmentation failure. The fourth step is the analysis of segmentation failure according the site, the type of synostosis, and the existence of discordance. The simple type and the multiple types should be evaluated in a different pathway (Figures 11, 12).

Figure 11.

Algorithm for the Solitary Type.
If only 1 congenitally abnormal vertebra exists in whole spinal column, we should follow the algorithm for the solitary type. Referring the Table 1the abnormal vertebra should be evaluated step by step. This algorithm helps to clarify the characteristics of abnormal vertebra. A indicates anterior; P, posterior; BV, butterfly vertebra; W, wedged vertebra; HV, hemivertebra; SB, spina bifida; LW, lateral wedged vertebra; H, hemilamina; IBL, incomplete bilamina; AUL, anterior unilateral; PUL, posterior unilateral; S, semisegmented; N, nonsegmented; F, fully segmented; U, unilateral; AP, anteroposterior.

Figure 12.

Algorithm for the Multiple Type.
If more than 2 congenitally abnormal vertebrae exist in whole spinal column, we should follow the algorithm for the multiple type. Referring the Table 2 the abnormal vertebrae should be evaluated step by step. The abnormal vertebrae that belong to unison type should be evaluated separately using the algorithm for the solitary type. A indicates anterior; P, posterior; U, unilateral; AP, anteroposterior (circumferential). Unison type of multiple malformed vertebrae should be evaluated using the algorithm for the solitary type.

By developing this algorithm for the evaluation of congenital scoliosis in terms of numbers of abnormal vertebrae, type of formation failure, and type of segmentation failure in separate steps, congenital spinal deformity could be mainly classified into 4 types: Type 1, solitary simple; Type 2, multiple simple; Type 3, complex; Type 4, segmentation failure ( Table 2 ). These 4 types of malformed vertebrae could be further modified by several morphologic factors, such as location, laterality, associated rib abnormalities, intracanal abnormalities, etc.

This classification has just been built up and we still have many things to do for getting acceptance in clinical usage. First, the complex type still remains uncertain and should be determined more clearly in this classification. Second, this classification should be analyzed by intra- and interobserver reliability. The aims of building up this 3D classification of congenital scoliosis and kyphosis have been to make the natural history of each congenital vertebral malformation much clearer, to identify which type of vertebral anomaly make the deformity progress and should be operated, and to assist making a strategy of surgical planning. These targets have not been investigated yet. We furthermore have to continue to advance these projects to investigate how it works for the treatment of congenital scoliosis and kyphosis, and how it is superior to the prior classifications in the future.

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