Classification(s) of Cervical Deformity

Abstract

Cervical spine deformities (CSD) are complex surgical issues with currently heterogenous management strategies. The classification of CSD is still an evolving field. Rudimentary classification schemas were initially proposed in the late 20th century but were largely informal and based on the underlying etiology (i.e. , postsurgical, traumatic, or inflammatory). The first formal classification schema was proposed by Ames et al. in 2015 who established a standard nomenclature for describing these deformities. This classification system established 5 deformity descriptors based on curve apex location (cervical, cervicothoracic, thoracic, craniovertebral junctional, and coronal deformities) and 5 deformity modifiers which helped surgeons utilize a standard language when discussing CSD patients. Koller et al. in 2019 subsequently established a classification system for patients with rigid cervical kyphosis based on regional and global sagittal alignment. Most recently, Kim et al. in 2020 proposed an updated classification system utilizing dynamic cervical spine imaging to guide surgical treatment of CSD patients. It identified 4 major groups of deformities - (1) those with "flat-neck" deformities caused by cervical lordosis T1 slope mismatch; (2) those with focal kyphotic deformities between 2 cervical vertebrae; (3) those with cervicothoracic deformities caused by large T1 slope; and (4) those with coronal deformities. Group 2 deformities most often required combined anterior-posterior approaches with short constructs, and group 3 deformities most often required posterior-only approaches with 3-column osteotomies.

Keywords: Cervical kyphosis; Cervical spine deformity; Spinal deformity.

Fig. 1.

Ames Classification for cervical spine deformity – deformities broken down into 5 deformity descriptors with 5 subsequent modifiers to account for sagittal vertical axis, horizontal gaze, cervical lordosis (CL), myelopathy, and overall SRS-Schwab classification (T, thoracic; L, thoracolumbar/lumbar; D, double curve; N, no coronal curve) [8]. CBVA, chin-brow vertical angle; TS, T1 slope; mJOA, modified Japanese Orthopedic Association; PI, pelvic incidence; LL, lumbar lordosis.

Fig. 2.

Figure demonstrating classifications of cervical sagittal balance types A-D (from left to right respectively) by Koller et al. and the European Cervical Spine Research Society [9]. SVA, sagittal vertical axis.

Fig. 3.

Three groups of sagittal deformities identified by Kim et al. [10] Dynamic images are utilized to identify the etiology of the deformity as well as plan surgical correction. “Ext” indicates extended neck lateral radiographs. Lat, lateral; Ext, extension; AP, anteroposterior.