Anatomical Rationale for Sensory Preservation in Breast Reconstruction Using a Split Thoracodorsal Flap

Autotransplantation of the thoracodorsal flap with complete preservation of its sensitivity is a pressing issue in reconstructive mammoplasty.

The aim was to study the structural features and spatial relationships of the lateral cutaneous branches (LCBs) of the intercostal nerves Th₅, Th₆, Th₇, Th₈, Th₉ and the thoracodorsal nerve (TDN) in women from the perspective of innervation of the thoracodorsal flap.

Material and methods. Anatomical dissection of the LCBs of the intercostal nerves Th₅, Th₆, Th₇, Th₈, Th₉ and the TDN along their entire course was carried out in 39 female cadavers (57–97 years of age). The coordinates of the nerve origin points were determined in relation to the clavicle and topographic landmarks. The diameter, length, direction, and angles of inclination in the anatomical planes were measured. Intrafascicular dissection was performed to identify the number of fascicles in the thoracodorsal nerve, along with their diameter, location, and functional type.

Results. In women, the LCBs of the intercostal nerves Th₅, Th₆, Th₇, Th₈, Th₉ measure 2.6 [1.5; 3.2] cm in length. They arise from the main nerve trunks between the midclavicular and anterior axillary lines, run laterally, and divide into anterior and posterior branches. The anterior branches are directed medially in an oblique downward course at an angle of 50° [42°; 55°], supplying the skin up to the parasternal line. The posterior branches turn posteriorly, follow an oblique upward course at an angle of 44° [36°; 49°] (p<0.001), and supply the skin up to the posterior axillary line. The combined length of the LCBs and their anterior branches is 7.7 [6.4; 8.5] cm; the combined length of the LCBs and their posterior branches is 7.5 [6.6; 8.6] cm (p=0.825); and the combined length of the anterior and posterior branches is 10.3 [10.0; 10.6] cm (p<0.001). The TDN is a mixed nerve. It arises from the posterior cord of the brachial plexus between the midclavicular and anterior axillary lines, located 3.0 [2.2; 3.5] cm below the clavicle and at a depth of 4.3 [3.8; 5.0] cm. In the frontal plane, the nerve deviates laterally from the vertical line at an angle of 40° [30°; 45°]; in the sagittal plane, it deviates posteriorly at an angle of 30° [20°; 35°]. The nerve consists of one motor fascicle with a diameter of 0.3 [0.30; 0.35] mm, located in the posterolateral portion, and one to three sensory fascicles with a diameter of 0.25 [0.25; 0.30] mm (p=0.005), which are situated anteromedially.

Conclusion. The differences in size, spatial distribution, and function between the LCBs of the intercostal nerves Th₅, Th₆, Th₇, Th₈, Th₉ and the thoracodorsal nerve provide the anatomical basis for preserving sensation when the split thoracodorsal flap is used in reconstructive breast surgery.

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