Cervical Inclination Angle: Normative Values in an Adult Multiethnic Asymptomatic Population

Abstract

Objective: The role of the craniocervical complex in spinal sagittal alignment has rarely been analyzed but it may play a fundamental role in postoperative mechanical complications. The aim of the study is to analyze the normative value of the cervical inclination angle (CIA) in an adult asymptomatic multiethnic population. Methods: Standing full-spine EOS of adult asymptomatic volunteers from 5 different coun-tries were analyzed. The CIA was analyzed globally and then in each decade of life. Different ethnicities were compared. Comparisons between different groups was performed using a t-test and statistical significance was considered with a p-value < 0. 05. Results: EOS of 468 volunteers were analyzed. The global mean CIA was 80. 2° with a maxi-mum difference of 9° between T1 and T12 (p < 0. 001). The CIA remains constant until 60 years old then decreases significantly passing from a mean value before 20 years old of 82.25° to 73. 65° after 70 years old. A statistically significant difference was found between the Ara-bics and other ethnicities with the formers having an inferior CIA: this was related to a mean older age (p < 0. 05) and higher body mass index (p < 0. 05) in the Arabics. Conclusion: The CIA remains constant until 60 years old and then reduces slightly but nev-er under 70°. This angle is helpful to evaluate the lever arm at the upper instrumented ver-tebra after an adult spinal deformity surgery and could predict the occurrence of a proximal junctional kyphosis when its value is lower than normal. Further clinical studies must con-firm this theory.