The fifth lumbar dorsal spinal rami pass posteriorly, medial to the medial intertransversarii muscles and divide into medial and lateral branches.  The medial branches pass close to the inferior articular processes of L5 lying directly on bone between the accessory and mamillary processes in a groove, notch or foramen.

Supply
The medial branches supply the multifidus muscles in which they terminate.

The muscular distribution of the medial branches of lumbar dorsal rami is very specific; each medial branch supplies only those muscles that arise from the lamina and spinous process of the vertebra with the same segmental number as the nerve, e.g. L5 medial branches supply only those fibers from the L5 vertebra.