A Novel Cervical Sagittal Classification for Asymptomatic Population Based on Cluster Analysis

Zhaoyang Gong; Haocheng Xu; Yong Yang; Xinlei Xia; Feizhou Lyu; Jianyuan Jiang; Hongli Wang; Xiaosheng Ma

doi:10.1097/BSD.0000000000001629

A Novel Cervical Sagittal Classification for Asymptomatic Population Based on Cluster Analysis

Clin Spine Surg. 2024 Apr 10. doi: 10.1097/BSD.0000000000001629. Online ahead of print.

Authors

Zhaoyang Gong¹, Haocheng Xu¹, Yong Yang², Xinlei Xia¹, Feizhou Lyu^{1

3}, Jianyuan Jiang¹, Hongli Wang¹, Xiaosheng Ma²

Affiliations

¹ Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, China.
² Department of Orthopaedics, Lanzhou University Second Hospital, Lanzhou University, Lanzhou, China.
³ Department of Orthopedics, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China.

PMID: 38637930
DOI: 10.1097/BSD.0000000000001629

Abstract

Study design: Cross-sectional study.

Objective: To propose a novel cervical sagittal classification for asymptomatic people so as to deepen the understanding of cervical sagittal alignment.

Summary of background data: Cervical spine sagittal morphology varies in people. There is a lack of widely-accepted cervical sagittal classification method.

Methods: In all, 183 asymptomatic subjects were included. A series of global and segmental cervical sagittal parameters were measured. Subjects with cervical lordosis (CL)<0 degrees were incorporated directly into the kyphosis (K) group. For subjects with CL ≥0 degrees, a two-step cluster analysis was used to arrive at the optimal number of clusters. The results of the expressions for the subtypes were derived by graphing. The 60 randomly selected lateral cervical spine films were evaluated by 4 spine surgeons at 4-week intervals using our classification method, the Toyama classification method and the Donk classification method. The 3 classification methods' reliability was expressed by the intra-group correlation coefficient (ICC), and convenience was expressed by the measuring time. Finally, the distribution of 4 subtypes was depicted, and sagittal parameters were compared among subtypes.

Results: Four subtypes of the cervical spine were suggested: Large lordosis (LL): CL≥-1.5×T1 slope (TS)+70°; Small lordosis (SL): -1.5×TS+50°≤CL<-1.5×TS+70°; Straight (S): 0°≤CL<-1.5×TS+50°; and K: CL<0°. The measuring time for our classification method was significantly less than the Toyama classification method (P<0.001). Our classification method showed high inter-observer reliability (ICC=0.856) and high to excellent intra-observer reliability (ICC between 0.851 and 0.913). SL was the most common type (37.7%). Men had more LL type and women had more S type and K type. The proportion of S and K increased with age. Cervical sagittal parameters were significantly different among the subtypes except for C4 vertebral body (VB) angle (P=0.546), C2-C7 SVA (P=0.628) and NT (P=0.816).

Conclusions: We proposed a novel cervical sagittal classification for an asymptomatic population, which proved to be simple to implement with satisfactory reliability.