In Vivo Needle-Based Electromechanical Reshaping of Pinnae

Abstract

IMPORTANCE Electromechanical reshaping (EMR) is a low-cost, needle-based, and simple means to shape cartilage tissue without the use of scalpels, sutures, or heat that can potentially be used in an outpatient setting to perform otoplasty.OBJECTIVES To demonstrate that EMR can alter the shape of intact pinnae in an in vivo animal model and to show that the amount of shape change and the limited cell injury are proportional to the dosimetry. DESIGN, SETTING, AND SPECIMENSIn an academic research setting, intact ears of 18 New Zealand white rabbits underwent EMR using 6 different dosimetry parameters (4 V for 5 minutes, 4 V for 4 minutes, 5 V for 3 minutes, 5 V for 4 minutes, 6 V for 2 minutes, and 6 V for 3 minutes). A custom acrylic jig with 2 rows of platinum needle electrodes was used to bend ears at the middle of the pinna and to perform EMR. Treatment was repeated twice per pinna, in proximal and distal locations. Control pinnae were not subjected to current application when being bent and perforated within the jig. Pinnae were splinted for 3 months along the region of the bend using soft silicon sheeting and a cotton bolster. MAIN OUTCOMES AND MEASURESThe ears were harvested the day after splints were removed and before euthanasia. Photographs of ears were obtained, and bend angles were measured. Tissue was sectioned for histologic examination and confocal microscopy to assess changes to microscopic structure and cellular viability.RESULTS Treated pinnae were bent more and retained shape better than control pinnae. The mean (SD) bend angles in the 7 dosimetry groups were 55°(35°) for the control, 60°(15°) for 4 V for 4 minutes, 118°(15°) for 4 V for 5 minutes, 88°(26°) for 5 V for 3 minutes, 80°(17°) for 5 V for 4 minutes, 117°(21°) for 6 V for 2 minutes, and 125°(18°) for 6 V for 3 minutes. Shape change was proportional to electrical charge transfer, which increased with voltage and application time. Hematoxylin-eosin staining of the pinnae identified localized areas of cell injury and fibrosis in the cartilage and in the surrounding soft tissue where the needle electrodes were inserted. This circumferential zone of injury (range, 1.5-2.5 mm) corresponded to dead cells on cell viability assay, and the diameter of this region increased with total electrical charge transfer to a maximum of 2.5 mm at 6 V for 3 minutes.CONCLUSIONS AND RELEVANCE Electromechanical reshaping produced shape change in intact pinnae of rabbits in this expanded in vivo study. A short application of 4 to 6 V can achieve adequate reshaping of the pinnae. Tissue injury around the electrodes increases with the amount of total current transferred into the tissue and is modest in spatial distribution. This study is a critical step toward evaluation of EMR in clinical trials.LEVEL OF EVIDENCE NA.

Optimal Electromechanical Reshaping of the Auricular Ear and Long-term Outcomes in an In Vivo Rabbit Model

“…Fourteen New Zealand white rabbits (Western Oregon Rabbit Company) ranging in age from 6 to 8 months were divided into 2 groups. Group 1 (n = 7) received EMR with variables previously identified 27 for effective reshaping, including 5 V for 4 minutes (5 ears), 4 V for 5 minutes (5 ears), or no voltage application (control; 4 ears). These rabbits were killed humanely after 6 months to assess the structural integrity, cell viability, and shape retention of the ears.…”

“…23,27 To assess the viability of chondrocytes, specimens were stained with the fluorophores calcein acetomethoxy and ethidium homodimer 1 and underwent confocal microscopy (Meta 510; Carl Zeiss LSM). Digital images were recorded and analyzed.…”

“…The jig and electrodes are removed and a retainer is used to maintain the desired bend while the tissue undergoes remodeling (Figure 1). Previous work 23,27 demonstrated the achievement of stable shape change in vivo in rabbit auricles and identified EMR settings, voltage, and application time for effective reshaping and its effects on the tissue remodeling as long as 3 months after treatment. Although this interval provides significant information with respect to the acute and subacute elements of wound healing and remodeling, it does not provide information on long-term outcomes essential to clinical evaluation and applicability in humans.…”

“…18–27 Electromechanical reshaping is a non–thermal-based method that relies on chemical reduction-oxidation (redox) reaction to alter tissue matrix structure and thus change tissue stress-strain associations. To perform EMR, a mold or jig is first used to bend cartilage to a desired shape, and electrodes are inserted into regions of increased internal stress.…”

Association of Electrochemical Therapy With Optical, Mechanical, and Acoustic Impedance Properties of Porcine Skin

“…Furthermore, other studies 4,8,20,28,29 have used EMR to mimic procedures that emulate the classic cut and suture operation ex vivo and in vivo. Unfortunately, unlike EMR studies 1,6,7,12,19,20,23–26 in cartilage, quantifying the mechanical effects of ECT on skin is not tractable.…”