Physical Effects of Hydrodissection as Rationale in Otoplasty: An Experimental Anatomical Study

A multitude of operative techniques to correct prominent ears are performed routinely. The propagated techniques have one common beginning: the injection of diluted adrenaline mixed with local anesthetics. The suggested benefits of this injection are vasoconstriction, anesthesia, and hydrostatic dissection of the surgical plane. Despite its routine use and the proposed surgical effects, the concrete anatomo-histological layer, in which the diluted adrenaline and local anesthetics are injected, has never been investigated. The aim of this study is to evaluate the concrete anatomo-morphological layer of injection and assess for possible hydrostatic dissection, which may have a clinical benefit in otoplasty. Retroauricular injection with the drawing ink was performed in 26 Thiel-conserved concha followed by a histological analysis. A juxta-perichondral (n = 11) or partially intraperichondral (n = 10) injection was observed in most cases. In 3 specimens, we observed ink deposition above the perichondrium and in 2 cases a subperichondral deposition. In 3 cases, ink was observed intravascularly. The mean distance of the dissected plane to the cartilage was 349 µm. The mean thickness of the perichondrium was assessed to be 444 µm. This experimental anatomical study reliably determines the level of injection in otoplasty as juxta-perichondral or partially intraperichondral. Optimal surgical dissection, resection as well as suture placement can be considerably facilitated by a juxta-perichondral deposition of vasoactive substances and the associated volume expansion. The results of our study provide empirical rationale toward a more evidence-based action for an important step in most of the propagated techniques in otoplastic surgery.