Surgical anatomy of the 10th and 11th intercostal, and subcostal nerves: prevention of damage during lumbotomy.

Purpose: In a descriptive, inventorial anatomical study we mapped the course of the 10th and 11th intercostal nerves, and the subcostal nerve in the abdominal wall to determine a safe zone for lumbotomy.

Materials And Methods: We dissected 11 embalmed cadavers, of which 10 were analyzed. The 10th and 11th intercostal nerves, and the subcostal nerve were dissected from the intercostal space to the rectus sheath. Analysis was done using computer assisted surgical anatomy mapping. A safe zone and an incision line with a minimum of nerve crossings were determined.

Results: The 10th and 11th intercostal nerves were invariably positioned subcostally. The subcostal nerve lay subcostally but caudal to the rib in 4 specimens. The main branches were located between the internal oblique and transverse abdominal muscles. The nerves branched and extensively varied in the abdominal wall. A straight line extended from the superior surface of the 11th and 12th ribs indicated a zone with lower nerve density. In 5 specimens the 10th and 11th intercostal nerves crossed this line from the superior surface of the 11th rib. In 5 specimens neither the 11th intercostal nerve nor the subcostal nerve crossed this extended line from the superior surface of the 12th rib up to 15 cm from the tip of the rib.

Conclusions: Damage is inevitable to branches of the 10th or 11th intercostal nerve, or the subcostal nerve during lumbotomy. However, an incision extending from the superior surface of the 11th or 12th rib is less prone to damage these nerves. Closing the abdominal wall in 3 layers with the transverse abdominal muscle separately might prevent damage to neighboring nerves.