Takahiro Ishii

Kinematics of the cervical spine during lateral bending were investigated using a novel system of three-dimensional motion analysis. To demonstrate in vivo intervertebral coupled motions of the cervical spine during lateral bending of the neck. No previous studies have successfully documented in vivo three-dimensional intervertebral motions of the cervical spine during lateral bending. Twelve healthy volunteers underwent three-dimensional magnetic resonance imaging (MRI) of the cervical spine in 7 positions with 10° increments of lateral bending. Relative motions of the cervical spine were calculated automatically by superimposing a segmented three-dimensional-MRI of the vertebra in the neutral position over images of each position using volume registration. Mean maximum lateral bending of the cervical spine to one side was 1.6° to 5.7° at each level. Coupled axial rotation opposite to lateral bending was observed in the upper cervical levels (Oc-C1, 0.2°; C1–C2, 17.1°), while in the subaxial cervical levels, it was observed in the same direction as lateral bending except for at C7–T1. Coupled flexion-extension motion was small at all vertebral levels (<1.1°). We succeeded in identifying in vivo coupled motions of the cervical spine in lateral bending for the first time.

Three-dimensional intervertebral motions of the subaxial cervical spine during head rotation were investigated in healthy volunteers using three-dimensional magnetic resonance imaging (MRI). To document intervertebral coupled motions of the subaxial cervical spine during rotation. In vivo three-dimensional kinematics of the subaxial cervical spine in rotation have not previously been well described, since they are too complicated to follow using conventional radiography or computed tomography techniques. Ten healthy volunteers underwent three-dimensional MRI of the cervical spine in 11 positions with 15° increments during head rotation using a 1.0-T imager. Relative motions of the subaxial cervical spine were calculated by automatically superimposing a segmented three-dimensional MRI of the vertebra in the neutral position over images of each position using volume registration. Three-dimensional motions of adjacent vertebrae were represented with 6 df (6 degrees of freedoms) by Euler angles and translations on the coordinate system defined by Panjabi, then visualized in animations using surface bone models. Mean axial rotation of the subaxial cervical spine in maximum head rotation (69.5°) was 2.2° at C2–C3, 4.5° at C3–C4, 4.6° at C4–C5, 4.0° at C5–C6, 1.6° at C6–C7, and 1.5° at C7–T1. Coupled lateral bending with axial rotation was observed in the same direction as axial rotation at all levels (C2–C3, 3.6°; C3–C4, 5.4°; C4–C5, 5.0°; C5–C6, 5.3°; C6–C7, 4.9°; C7–T1, 1.2°). Coupled extension with axial rotation occurred in the middle cervical region (C2–C3, 1.4°; C3–C4, 2.3°; C4–C5, 1.5°), while in the lower cervical region, flexion was coupled with axial rotation (C5–C6, 0.9°; C6–C7, 2.4°; C7–T1, 3.0°). We investigated intervertebral motions of the subaxial cervical spine during head rotation using a three-dimensional imaging system, and obtained the first accurate depictions of in vivo coupled motion. These findings will be helpful as the basis for understanding abnormal conditions.

Study Design. Kinematics of the upper cervical spine during head rotation were investigated using three-dimensional magnetic resonance imaging (MRI) in healthy volunteers. Objectives. To demonstrate in vivo intervertebral coupled motions of the upper cervical spine. Summary of Background Data. Although various in vivo and in vitro studies have identified the normal movement patterns of the upper cervical spine, no previous studies have accurately analyzed in vivo three-dimensional intervertebral motions of the upper cervical spine during head rotation. Methods. Fifteen healthy volunteers underwent three-dimensional MRI of the upper cervical spine using a 1.0-T imager in progressive 15° steps during head rotation. Segmented three-dimensional MRIs of each vertebra in the neutral position were superimposed over images taken at other positions, using voxel-based registration. Relative motions between occiput (Oc) and atlas (C1) and between C1 and axis (C2) were measured and described with 6 degrees of freedom by rigid body Euler angles and translations. Results. Mean (± SD) maximum angles of axial rotation in Oc–C1 and C1–C2 were 1.7 ± 1.5° and 36.2 ± 4.5° to each side, respectively. Increases in angle of axial rotation in C1–C2 became smaller with increased head rotation, indicating axial rotation in C1–C2 displayed nonlinear motion. Coupled lateral bending with axial rotation was observed in the direction opposition to that of axial rotation in Oc–C1 (mean, 4.1 ± 1.4°) and C1–C2 (mean, 3.8 ± 3.0°). Coupled extension with axial rotation occurred at both C0–C1 (mean, 13.3 ± 4.9°) and C1–C2 (mean, 6.9 ± 3.0°). Conclusions. We developed an innovative in vivo three-dimensional motion analysis system using three-dimensional MRI. In vivo coupled motions of the upper cervical spine investigated using this system supported the results of the previous in vitro study.