In vivo 3-D脊椎運動解析―頚椎の回旋運動

In Vivo Three-Dimensional Analysis of Spinal Motion. Kinematics of the Cervical Spine in Rotation

　われわれは，3-D MRIを用いた新しい非侵襲的3次元動態解析システムを独自に開発し，in vivoでの頭部回旋時における頚椎のカップリングモーションを捉えることに成功した．対象および方法は，健常成人に対し，頭部を15°間隔で回旋した状態にて，3-D MRI撮影を行った．各椎骨の動きの追跡は中間位の画像と回旋位で撮影した画像とで，ボリュームレジストレーションを使って3次元的にマッチングすることにより行った．結果は上位頚椎の回旋は，回旋と反対方向の側屈を伴っていた．一方，中下位頚椎の回旋は，すべての椎間で回旋と同じ側への側屈を伴っていた．また上位と中位頚椎の回旋は，後屈を，下位頚椎の回旋は，前屈を伴っていた．このような頚椎の複雑なカップリングモーションを，3次元動態のアニメーションを作成することにより，容易に理解することができた．

　We developed a novel 3-D motion analysis system and succeeded in identifying coupled motions of the cervical spine during head rotation in vivo. The cervical of spine normal, healthy volunteers was examined by 3D-MRI in 11 positions with 15° increments during head rotation. Relative motion of the cervical spine was calculated automatically by superimposing a segmented 3D-MRI of the vertebra in the neutral position over images in each position by volume registration. The mean axial rotation of the cervical spine in maximum head rotation was 1.7° at Oc/C1, 36.2° at C1/2, 1.9° at C2/3, 4.3° at C3/4, 4.4° at C4/5, 4.2° at C5/6, 2.5° at C6/7, and 1.6° at C7/T1. Coupled lateral bending with axial rotation was observed in the opposite direction to axial rotation in the upper cervical region (Oc/C1, 4.1°；C1/2, 3.8°), whereas in the subaxial cervical region it was observed in the same direction as axial rotation (C2/3, 3.7°；C3/4, 5.6°；C4/5, 5.2°；C5/6, 5.1°；C6/7, 4.6°；C7/Th1, 1.1°). Coupled extension with axial rotation occurred in the upper and middle cervical region (Oc/C1, 13.3°；C1/2, 6.9°；C2/3, 1.4°；C3/4, 2.3°；C4/5, 1.5°). In the lower cervical region, flexion was coupled with axial rotation (C5/6, 0.9°；C6/7, 2.4°；C7/T1, 3.0°). Our system not only facilitates mathematical descriptions of 3D motion, but 3D visualization of the information, and made it possible to easily understand complicated coupled motions of the cervical spine.