Latest knowledge on a comprehensive understanding of cervical deformity and selection of effective treatment methods using recent classification systems: a narrative review

Surgical treatment for patients with cervical spine deformities is challenging for both patients and doctors. For successful surgical treatment, mastery of processes is important to objectively evaluate and classify the degree of deformity. Recently, efforts have been increasing to systematically understand, evaluate, and effectively treat complex cervical spine deformities. Various parameters are being developed to quantify and objectively evaluate the degree of cervical spine deformity, and classification methods are being introduced to help establish the treatment scope by categorizing it according to the degree of deformity. However, a comprehensive and systematic understanding of complex deformities using only the currently introduced classification methods and related knowledge is not easy. Through this review, we aimed to introduce various classification methods and their pros and cons to evaluate cervical deformities, analyze their meaning, and provide a basic understanding of the evaluation and classification of patients with cervical spine deformities. This review also aimed to aid in the decision-making process for the treatment of cervical spine deformities by presenting a structured treatment algorithm based on recently known classification systems and lay the foundation for efficient treatment.