Anatomical variations and coding of the intra-trunk pathways in the thoracodorsal nerve

Abstract

Aim. To study anatomical variations of the intra–trunk pathways in the thoracodorsal nerve bundles and to develop a system for their coding.Materials and methods. After fixation in a 2% solution of acetic acid using the MBS-10 stereomicroscope, we performed macro- and microscopic intra-trunk dissection of thoracodorsal nerve bundles in 121 specimens obtained from 105 corpses of males and females who died at the age of 40–97 years. Using the obtained findings, we compiled a database in the MS Excel 12.0 software and determined the number of anatomical variations in absolute and relative (% from 121 specimens) units.Results. The study revealed that the thoracodorsal nerve is a mixed nerve, which consists of 1 motor and 1– 3 sensory bundles that variously pass through the spinal nerves, trunks, and the axillary nerve with the formation of 20 intra-trunk pathways. In 77% of cases, sensory bundles arising from the thoracodorsal nerve pass through the posterior bundle, the posterior division, the middle trunk, and the C7 spinal nerve or the inferior trunk and the C8 spinal nerve. In 22% of cases, the thoracodorsal nerve has one or, rarely, two duplicate sensory pathways besides the main one. In 93% of cases, the motor bundle to the thoracodorsal nerve passes through the C7 spinal nerve and the middle trunk, the posterior division, and the posterior bundle. Coding the anatomical variations of the intra-trunk pathways in the direction of sensory bundle «posterior bundle → posterior division → trunk → spinal nerve; motor bundle ← posterior bundle ← posterior division ← trunk ← spinal nerve allows to briefly yet clearly and fully display the morphological diversity of the nerve anatomy.Conclusion. The identified anatomical variations of the intra-trunk pathways can be useful in the diagnosis of injuries and diseases. They expand indications for the use of spinal nerves, trunks of the brachial plexus, and the thoracodorsal nerve in reconstructive surgery.