The thoracoabdominal intercostal nerves: an anatomical study for their use in neurotization.

The topographic anatomy of the lower intercostal nerves is less known than that of the upper ones, except for the subcostal nerve (twelfth intercostal nerve). It is possible to use the lower intercostal nerves to neurotize the lumbar roots. We studied the anatomy of the ninth, tenth and eleventh intercostal nerves in order to specify the descriptive and topographical anatomical data that will allow their harvest in good condition. The ninth, tenth and eleventh intercostal nerves of 30 cadavers were dissected. The proximal part of the nerves in the posterior intercostal space was exposed through a posterior approach. The lateral intercostal space was exposed through a lateral approach, deep to the latissimus dorsi, that made it possible to harvest the intercostal nerve. The proximal course of the nerves in the posterior intercostal space was the same in all cases. The nerves move obliquely towards the outside to reach the lower border of the rib. The exit of the posterior intercostal space is a fibrous strait, which marks the entry of a channel between two muscular layers. We describe an aponeurotic channel in which the nerve and vessels run, immediately at the lower border of the cranial rib. The mean total length of intercostal nerve harvested by our technique was 17.86 cm for the ninth intercostal nerve, 16.95 cm for the tenth and 15.75 cm for the eleventh. Bifurcation of the intercostal nerve into a deep branch and the lateral cutaneous branch was found in the majority of the cases, 9.5-21 cm from the emergence of the intercostal nerve in the posterior intercostal space. This anatomical study of the ninth, tenth and eleventh intercostal nerves in the posterior intercostal and lateral intercostal spaces appears to us to allow reliable surgical harvesting.