Sensory Reinnervation With Subcutaneously Embedded Innervated Flaps: An Experimental Study in Rats

Abstract

Background: In breast reconstruction, both aesthetic outcomes and sensory function are important for postoperative quality of life. Innervated flaps are useful in reconstruction after conventional mastectomy (CM), which leaves a large portion of the skin paddle exposed on the body surface. However, whether they are also useful in skin-sparing mastectomy (SSM) and nipple-sparing mastectomy (NSM) remains unclear. This study aimed to examine the usefulness of innervated flaps in restoring sensation after SSM and NSM using a rat model.

Methods: Dorsal cutaneous nerves of rats were entirely eliminated except for the medial branch of the dorsal cutaneous nerve of thoracic segment 13, resulting in an innervated field surrounded by a denervated field. The innervated field was elevated as an innervated island flap and then subcutaneously embedded, with the skin paddle deepithelialized entirely (NSM group, n = 5) or except at the center (SSM group, n = 6). In the control model (CM group, n = 5), the flap was sutured back into its original position. Postoperative changes in the mechanonociceptive field were evaluated using the cutaneous trunci muscle reflex test. Immunohistochemical evaluation of regenerated nerves in the new mechanonociceptive field was performed at postoperative week 12.

Results: In the SSM and CM groups, the mechanonociceptive field expanded around the skin paddle. In the NSM group, a new mechanonociceptive field appeared at postoperative week 4 and expanded thereafter. Areas of the mechanonociceptive field at postoperative week 12 did not differ significantly between the SSM and NSM groups, but were significantly smaller compared with the CM group and comparable to original flap areas. Histologically, S100- and PGP9.5-positive nerve fibers were observed in the dermis of the new mechanonociceptive field and subcutaneous flap tissue.

Conclusions: Subcutaneously embedded innervated island flaps induced nerve regeneration and sensory reinnervation of the denervated skin, suggesting that innervated flaps may also be useful in reconstruction post-SSM/NSM.