Lumbar plexus

Lumbar plexus

The lumbar plexus is a retroperitoneal structure. It is formed by the divisions of the first lumbar and the subcostal nerve roots. The main body of the lumbar spine is located within the psoas and crosses the midpoint of the L4-L5 disc space.

Iliohypogastric nerve

The iliohypogastric nerve originates from the lumbar plexus. This nerve emerges from the psoas major, crosses the quadratus lumborum, and perforates the transversalis. It supplies sensation to the skin over the lateral gluteal region above the pubis. It may or may not have a motor branch. Care should be taken not to injure this nerve during the closure of OLIF51 incision.

Ilioinguinal nerve

The ilioinguinal nerve originates from the L1 branch of the lumbar plexus. This nerve emerges from the psoas major and perforates the transversalis. It communicates with the iliohypogastric nerve and supplies sensation to the penis and scrotum in males and to the labia in females. Care should be taken not to injure this nerve during the closure of the OLIF51 incision.

Obturator nerve

The obturator nerve passes under the psoas on the medial side. It is responsible for the motor innervation of the adductor muscles. Additionally, the obturator nerve facilitates sensory innervation of the skin of the medial aspect of the thigh. Compression and stretching of the obturator nerve by retractors may lead to post-operative neural complications.

Genitofemoral nerve

The genitofemoral nerve exits the psoas near the L3 vertebral body and runs down the anterior aspect of the psoas muscle. This nerve is encapsulated in the fascial layer on the belly of the psoas. It descends obliquely forward through the psoas major muscle, emerging on the abdominal surface between the cranial third of the L3 vertebra and the caudal third of the L4 vertebra. During an OLIF25 approach, it can be temporarily mobilized, along with the psoas, to access the disc space.

Lateral femoral cutaneous nerve

The lateral femoral cutaneous nerve is found within the retroperitoneal fat. During an OLIF25 approach, it can be pinned against the anterior aspect of the iliac crest or can be stretched anteriorly by the OLIF retractor. Care should be taken during OLIF25 access to avoid this neural structure, which, if injured, could result in dysesthesia to the thigh.

Femoral nerve

The femoral nerve is located posteriorly in the oblique corridor and is most often seen traversing the midpoint of the disc space at L4-L5. Compression and stretching of the femoral nerve by retractors (e.g., in a transpsoas approach where the femoral nerve is displaced posteriorly and pressed up against the L5 transverse process) may lead to post-operative neural complications.

Sympathetic chain

The sympathetic chain consists of ganglia on both sides of the spine. If visualized during an OLIF approach, the sympathetic chain may be gently swept away from the anterior portion of the psoas and toward the anterior longitudinal ligament (ALL) with a blunt dissector such as kitner. Elements of the sympathetic chain may be contained within the adventitial layer during an OLIF51 approach. A small percentage of patients may experience lower extremity symptoms such as leg warmness if the nerve is injured.

Superior hypogastric plexus (SHP)

The superior hypogastric plexus (SHP) is a plexus of nerves below the bifurcation of the abdominal aorta. Some elements of the SHP are found within adventitial layers along the sympathetic chain during the OLIF51 approach. It controls vasomotor, pilomotor, and secretion from sweat glands to the skin of the perineum and lower limbs. It also controls the internal sphincter of the bladder. When the SHP is injured, unopposed parasympathetic input opens the sphincter and keeps it from closing during ejaculation, leading to retrograde ejaculation.