Elucidation of soft tissue flap histologic margins within a canine vocal fold

Background: Histologic identification of implanted soft tissues in experimental animal models can be challenging, as donor tissue often strongly resembles the recipient bed. We have encountered this dilemma following implantation of a Composite Thyroid Ala Perichondrium flap (CTAP) into a vocal fold. The CTAP procedure is the first to utilize a vascularized flap for vocal fold reconstruction, making data to confirm or refute its viability critical. The current study evaluated several tissue stains to define precisely the histologic margins of CTAPs at two weeks post-implantation in a canine model.

Methods: Initial testing exposed canine cadaveric tissues to four stains (tattoo ink, Congo red, 4’6- diamidino-2-phenylindole, and henna) across four time periods. Tattoo ink alone withstood histologic processing. An exposure of 1 minute adequately delineated CTAP boundaries. The study concluded with a canine in vivo evaluation of a CTAP exposed to tattoo ink for 1 minute. After a two-week recovery period, vocal folds were harvested and evaluated histologically.

Results: Tattoo ink proved to be a safe and effective histologic marker in vivo, where the histologic margins of the implanted CTAP were clearly demarcated by a thin band of tattoo ink, soft tissue reactions were minimal, and interference with standard, special, or immunohistochemical stain assessments did not occur.

Conclusions: Tattoo ink provides a reliable means of demarcating a CTAP within a vocal fold and demonstrated that CTAPs survive transplantation. Further, tattoo ink demarcation may serve as a useful histologic marker for those wishing to assess tissue implants in other in vivo models.