Practically all methods which have been recommended for manual rotation in occipito-posterior positions of the vertex involve grasping the head with a hand in the vagina. To grasp such a smooth, globular, slippery mass securely is not easy. If such a grasp be secured the rotating force which can be exerted is inadequate in difficult cases. The attempt to grasp the head usually lifts it up to a higher plane of the pelvis, and this elevation of the head often results in diminished flexion; both undesirable occurrences.
In right occipito-posterior positions of the vertex, which, for convenience, we shall assume throughout this paper unless otherwise stated, the grasping of the occiput necessarily moves it away from the right side of the pelvis, against which it is uniformly found. This disturbance of position often leads to a serious complication.
With the occiput snug against the right side of the pelvis there
PORTER WD. A METHOD OF BIMANUAL ROTATION IN OCCIPITO-POSTERIOR POSITIONS OF THE VERTEX.. JAMA. 1907;XLIX(21):1748-1750. doi:10.1001/jama.1907.25320210020001d