Introduction: While the Free TRAM flap has become routine as one standard for autologous breast reconstruction in tertiary centers, attempts to improve somatosensory outcome have remained elusive. Preliminary reports show improved sensation with microneurorrhaphy, but there have been many variablilities in these techniques. Initial reports using the lateral branch of the fourth intercostal nerve have not been widely adopted due to difficulties identifying constant anatomic landmarks and preserving adequate lengths of donor nerve. With the rise in popularity of vertical breast reduction patterns and medially based pedicles empirical evidence has been mounting that the dominant sensory supply to the nipple and medial breast may indeed arise from medial perforating intercostal nerves. In this report, we describe a series of breast reconstructions in which microneurorrhaphy has been accomplished routinely with the use of medial intercostal nerves. We describe in detail the anatomic considerations of both the donor nerve supply and its relation to functional sensory nerve preservation of the TRAM harvest.

Objective: To identify the anatomic variability of both the medial intercostal nerve supply to the breast following mastectomy and the recipient site sensory TRAM flap anatomy, evaluating their usefulness in routine innervation of the free TRAM flap.

Methods: A series of 30 consecutive patients undergoing free TRAM breast reconstruction either immediate or delayed, were studied intraoperatively in an attempt to provide innervation to the flaps.

Results. The anatomic detail in the course of the intercostal sensory nerves is described. Nerves could be identified readily in most cases. In the majority of cases (N=26) the third intercostal nerve was identified and found the be 1.5 –2.0 mm in diameter with two to three fascicles, similar to in size to a digital nerve. In all patients in which suitable recipient and donor nerves were identified microneurorrhaphy was performed using standard microepineural technique. The presence of preoperative irradiation correlated with the difficulty in identifying adequate donor intercostal sensory nerves. Recipient site TRAM sensory anatomy was more highly variable, and three distinct patterns of innervation were identified of the 11th and 12th intercostal nerves: epimysial, superficial intramuscular, and less frequently, submuscular.

Conclusion: Anatomic variability of sensory nerves is demonstrated in the harvest of the TRAM flap while the recipient site shows relative anatomic consistency. Thus, immediate reinnervation of the free TRAM is indeed possible and should be routine for most plastic surgeons facile in microsurgery. Size match and adequate length for anastomoses has been demonstrated in all cases. Further studies will determine the usefulness of the technique and the completeness of somatosensory return. Since many variable also contribute to the final degree of innervation of the TRAM flap such as thickness of the native mastectomy flaps, variable preservation of the internal mammary perforators and lateral intercostal perforators, the presence of post-operative irradiation, further studies will determine whether routine reinnervation will prove beneficial.