2 – Anatomy: The trajectory of the subcostal and iliohypogastric nerves

The subcostal (SC) and iliohypogastric (IH) nerves originate from the spinal nerve roots of T12 and L1 respectively

They run across the anterior surface of the quadratus lumborum (QL) muscle

They continue laterally and pierce the posterior aponeurotic extension of the transverse abdominis muscle and enter the TAP (transverse abdominis plane = the neurovascular fascial plane between the transverse abdominis and internal abdominal oblique muscles)

The lateral cutaneous branches of the two nerves branch off typically before entering the TAP, and these lateral branches are not covered by a classical TAP block

The lateral cutaneous branches of the two nerves innervate the iliac crest and the skin of the upper thigh between the iliac crest and the greater trochanter