Spine - 2026-03-23 - Journal Article
Proposal of a Cervical Sagittal Classification System to Guide Surgical Treatment for Adult Cervical Deformity.
Sardar ZM, Miller R, Reyes JL, Dionne A, Coury JR, Hassan FM, Le Huec JC, Bourret S, Hasegawa K, Wong HK, Liu G, Dennis Hey HW, Kelly M, Lenke LG
Topics
Key Takeaway
A multinational normative cohort of 468 asymptomatic adults establishes mean cSVA of 19.1 mm and T1 slope of 23.0°, yielding the formula CSA = 25 − T1S (R²=0.45) as the basis for a four-type cervical sagittal classification system.
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Summary
Using the MEANS cohort of 468 asymptomatic adults across 5 countries, the authors measured cervical sagittal parameters and derived a linear regression formula (CSA = 25 − T1S, R²=0.45) to define normative alignment thresholds (cSVA threshold mean+2SD, T1S threshold mean+2SD). A four-type classification (1A, 1B, 2, 4) was proposed based on the spinal region driving deformity, with Type 3 (isolated thoracolumbar driver) absent in the normative cohort; Types 1A/1B represent compensated alignment while Types 2 and 4 indicate cervical and combined deformity, respectively.
Key Limitation
The classification system has no outcome validation in a symptomatic adult cervical deformity surgical cohort, so its ability to predict postoperative functional improvement or guide fusion extent remains unproven.
Original Abstract
STUDY DESIGN
Retrospective Analysis.
OBJECTIVE
To describe normative cervical sagittal alignment and to propose a classification system to guide clinical assessment and surgical planning.
BACKGROUND CONTEXT
Optimizing alignment is a key goal of adult cervical deformity (ACD) surgery. The purpose of this study was to understand normative alignment utilizing an asymptomatic adult cohort and to formulate a classification system that would help identify the spinal regions contributing to the cervical deformity.
METHODS
468 asymptomatic adults (18-80 y) from 5 countries (USA, France, Japan, Singapore, Tunisia) formed the Multi-Ethnic Alignment Normative Study (MEANS). The C2-C7 sagittal vertical axis (cSVA), T1 slope (T1S), and C2-C7 cervical sagittal angle (CSA; positive=kyphosis, negative=lordosis), and other sagittal parameters were measured. Linear regression was utilized to correlate the C2-C7 CSA to the T1 slope. Thresholds for the C2-C7 sagittal vertical axis and T1 slope were defined as mean+2 standard deviations. Groups were compared using ANOVA with Tukey post‑hoc test. Chi square analysis was used for categorical comparisons.
RESULTS
Mean values for C2-C7 cervical sagittal angle was -0.4° (12.7°), T1 slope was 23.0° (7.9°), C2-C7 sagittal vertical axis was 19.1 (9.8). The highest mean segmental Cobb angle was 3.2° (4.8), which was at the C4-C5 segment. The T1S-CSA mismatch was 22.6 (9.4) with an interquartile range of 9.5 - 35.7. Linear regression yielded a formula CSA=-1.1(T1S) + 24.5 (R2=0.45, P<.0001) which was simplified to CSA=25 - T1S. Four alignment types (1A/1B/2/4) were observed in the MEANS cohort. Type 3 alignment was absent. Types 1A, 1B, 2, and 4 alignment showed significant differences across cervical, thoracic, and global sagittal parameters.
CONCLUSION
We define normative cervical alignment utilizing the MEANS cohort and propose a classification system to identify the spinal region driving the cervical deformity. Types 1A-B represent well-compensated alignment. Type 2 and 3 were considered to have deformities in the cervical spine and thoracolumbar spine, respectively. Type 4 spines have a combined deformity. This can help guide the surgeon to determine the appropriate region that should be addressed with surgery.