Abstract
Study Design.Retrospective analysis of cervical spine Magnetic Resonance (MR) Image data in patients and normal subjects.Objectives.To introduce a method for assessment of possible rotation of head, atlas and axis by analyzing sagittal MR images, when axial image data through these upper cervical rotational segments are not available and to discuss the relevance of these findings. Background Data and Methods.In 100 routine C-Spine studies performed in patients with various complaints, positioning was controlled by comparing identical anatomical points at the anterior surfaces of the occipital condyles, the lateral masses of the atlas and the axis. Straight positioning or approximate degrees of rotation of the mentioned anatomical structures was derived by trigonometric means. Results.Sixty-two percent of the patients featured exact neutral head position (0°). In 23%, there was 2° of rotation between head and tabletop, 13% showed 4° and 2% a rotation of 6°. The atlas in 49% showed no rota- Conclusion.Even without axial images, estimation of rotation of head and upper cervical segments is possible from sagittal MR-images. While minor atlantoaxial rotation is frequent and normal and probably due to asymmetry or suboptimal positioning, in some patients it could indicate occult rotational trauma and point to fixed rotary distortion (FRD).