The posterior ramus of spinal nerve (or posterior primary division) refers to the posterior division of a spinal nerve. The ramus is also known by a number of other names, posterior (or dorsal) rami (or branches or divisions) of the spinal nerves.The posterior ramus is one of two major branches of a spinal nerve that emerge after the nerve emerges from the intervertebral foramen.The posterior ramus carries information that supplies muscles and sensation to the human back.ecause each spinal nerve carries both sensory and motor information, spinal nerves are referred to as “mixed nerves.. Posterior rami carry visceral motor, somatic motor, and sensory information to and from the skin and deep muscles of the back.