An isolated contraction of the Obliquus Capitis Inferior and Rectus Capitis Posterior Major demonstrated with Musculoskeletal Ultrasound Imaging

Study design: A quasi-experimental study design Background: The motion of the suboccipital region is controlled by several groups of the smaller and larger muscle group, and these might play a role in the development of cervicogenic headache. Abnormal muscle tone can lead to abnormal movement patterns resulting in altered proprioceptive information from the mechanoreceptors in this region. Thus, abnormal muscle tone will contribute to cervical dysfunction and might result in pain, joint irritation, and poor functioning of the neck. At the same time , unilateral contraction of the suboccipital muscles could lead to rotation of the atlas. This could result in a significant translation of the spinal cord toward the side of rotation within the dural sack. This homolateral shift of the spinal cord could then lead to dural tension and possibly contribute to cervicogenic headaches. Methods: A convenience sample of 25 healthy subjects were recruited for this study. Musculoskeletal ultrasound imaging was used to measure the diameter of the Obliquus Capitis Inferior and the Rectus Capitis Posterior Major immediately following an isometric contraction into head extension and rotation. Outcomes: An isometric-induced contraction resulted in a significant change in the diameter of the obliquus capitis inferior and contralateral rectus capitis posterior major and, thus, could affect the position of atlas in the atlantoaxial joint. Discussion: The effect of an isometric-induced contraction of the obliquus capitis inferior and contralateral rectus capitis posterior major in a subgroup of asymptomatic individuals was measured using musculoskeletal ultrasound imaging. The results of this study indicate that the diameter of both muscles significantly changed with the isometric contraction. This study's findings support that suboccipital muscles can contract in isolation and, thus effect the position of atlas.