The evaluation of cervical spine mobility without significant spondylosis by kMRI

Retrospective analysis of kinetic magnetic resonance images (kMRI). To analyse the kinematics of cervical spine inpatients without significant spondylosis and to understand the normal movement of the cervical spine as reference for future comparison. Although some studies have been conducted to describe the normal mobility of the cervical spine, prior studies did not establish a relationship between the kinematics of cervical spine and disc degeneration. Only a few studies of the kinematics of the non-degenerated cervical spine have been reported; however, they focused on single level and not all the levels of cervical spine. 468 symptomatic patients underwent upright cervical kMRI, and cervical disc degeneration was evaluated with a new grading system. This grading system consists of four grades (0–III), and the cervical spines with grade 0 and grade I discs were included in this study. Finally, 61 symptomatic patients were studied 34 male and 27 female with an average age of 41.9 years. kMRI was used to define the normal mobility of the cervical spine by calculating the translation motion, angular variation and percentage angular contribution to the total cervical spine. The translation motion of the cervical spine at each level was 0.85 ± 1.22 mm at C2/3, 1.05 ± 1.19 mm at C3/4, 0.63 ± 1.19 mm at C4/5, 0.57 ± 0.91 mm at C5/6, 0.16 ± 0.86 mm at C6/7 and −0.11 ± 0.81 at C7/T1. In general, the translation motion decreased from proximal segment to distal segment. The angular variation of the cervical spine at each level was 5.58 ± 3.86° at C2/3, 8.26 ± 4.81° at C3/4, 9.11 ± 4.87° at C4/5, 10.05 ± 5.26° at C5/6, 8.31 ± 4.30° at C6/7 and 4.87 ± 3.28 ° at C7/T1. The angular variation at C2/3 and C7/T1 was significantly lower compared to other levels (P < 0.05). The contribution of each cervical level to the total angular mobility of cervical spine was the greatest at C5/6 (21.68 ± 10.31 %) and least at C7/T1 (11.11 ± 7.60 %) (P < 0.05). This study demonstrates the normal cervical segmental mobility for the entire cervical spine using kMRI. These results will be helpful to understand the normal mobility of the cervical spine and for understanding the relationship between kinematics of the cervical spine and disc degeneration for future comparisons.