Survival of chondrocytes in rabbit septal cartilage after electromechanical reshaping

Impact of Tissue Handling and Size Modification on Septal Chondrocyte Viability

INTRODUCTION

The physical modification of cartilage grafts during rhinoplasty risks chondrocyte death at the margins where the tissue is cut. This study compares chondrocyte viability between diced, scaled, and pate samples in human models, and further computes percent chondrocyte viability as a function of sequential dicing size in a computational model.

METHODS

Septal cartilage from 11 individuals was prepared as follows: diced (1 mm cubic), scaled (shaved to <1 mm thickness ~ translucent), pate (0.02 g of scraped cartilage surface), positive control (2 × 2 mm diced), and negative control (2 × 2 mm diced soaked in 70% EtOH). Viability analysis was performed using Live/Dead assay™ and confocal microscopy. Numerical simulation of cartilage dicing in 0.05 mm increments was performed using MATLAB assuming 250 chondrocytes/mm3 with each average chondrocyte size of 65 μm2.

RESULTS

Chondrocyte viability was similar between 1 mm diced cartilage, scaled cartilage, and positive control samples (p > 0.05). Conversely, pate samples had significantly less viability compared to positive controls, diced samples, and scaled samples (all p < 0.01 after Bonferroni correction). Pate samples had similar chondrocyte viability compared to negative controls (p = 0.36). On computational modeling, cartilage viability decreased to 50% as the diced sample was cut from 1 mm edge length to 0.7-0.8 mm. Similarly, cartilage viability decreased to 26% at 0.55-0.65 mm, 11% at 0.4-0.5 mm, and <5% at <0.4 mm edge length.

CONCLUSION

Modifying septal cartilage grafts into 1 mm diced or scaled samples maintains ideal chondrocyte viability whereas pate preparations result in significant chondrocyte death. According to computational analysis, chondrocyte viability sharply decreases as the cartilage is diced below 0.7-0.8 mm.

LEVEL OF EVIDENCE

N/A Laryngoscope, 134:4259-4265, 2024.

Electrochemical Lipolysis Induces Adipocyte Death and Fat Necrosis: In Vivo Pilot Study in Pigs

BACKGROUND

Current minimally invasive fat reduction modalities use equipment that can cost thousands of U.S. dollars. Electrochemical lipolysis (ECLL), using low-cost battery and electrodes (approximately $10), creates acid/base within fat (width, approximately 3 mm), damaging adipocytes. Longitudinal effects of ECLL have not been studied. In this pilot study, the authors hypothesize that in vivo ECLL induces fat necrosis, decreases adipocyte number/viability, and forms lipid droplets.

METHODS

Two female Yorkshire pigs (50 to 60 kg) received ECLL. In pig 1, 10 sites received ECLL, and 10 sites were untreated. In pig 2, 12 sites received ECLL and 12 sites were untreated. For ECLL, two electrodes were inserted into dorsal subcutaneous fat and direct current was applied for 5 minutes. Adverse effects of excessive pain, bleeding, infection, and agitation were monitored. Histology, live-dead (calcein, Hoechst, ethidium homodimer-1), and morphology (Bodipy and Hoechst) assays were performed on day 0 and postprocedure days 1, 2, 7, 14 (pig 1 and pig 2), and 28 (pig 2). Average particle area, fluorescence signal areas, and adipocytes and lipid droplet numbers were compared.

RESULTS

No adverse effects occurred. Live-dead assays showed adipocyte death on the anode on days 0 to 7 and the cathode on days 1 to 2 (not significant). Bodipy showed significant adipocyte loss at all sites ( P < 0.001) and lipid droplet formation at the cathode site on day 2 ( P = 0.0046). Histology revealed fat necrosis with significant increases in average particle area at the anode and cathode sites by day 14 (+277.3% change compared with untreated, P < 0.0001; +143.4%, P < 0.0001) and day 28 (+498.6%, P < 0.0001; +354.5%, P < 0.0001).

CONCLUSIONS

In vivo ECLL induces fat necrosis in pigs. Further studies are needed to evaluate volumetric fat reduction.

CLINICAL RELEVANCE STATEMENT

In vivo ECLL induces adipocyte death and fat necrosis. ECLL has the potential to be utilized in body fat contouring.

1064nm Nd:YAG laser promotes chondrocytes regeneration and cartilage reshaping by upregulating local estrogen levels

Cartilage is frequently used as a scaffolds for repairing and reconstructing body surface organs. However, after successful plastic surgery, transplanted cartilage scaffolds often exhibit deformation and absorption over time. To enhance the shaping stability of cartilage scaffolds and improve patients' satisfaction after reconstructions, we employed the ear folding models in New Zealand rabbits to confirm whether the 1064nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser could promote cartilage reshaping. There was an increase in collagen and aromatase (Cyp19) expression within the ear cartilage after laser treatment. Moreover, we have found that the Cyp19 inhibitor can inhibit the laser's effect on cartilage shaping and reduce collagen and Cyp19 expression. The overall findings suggest that treatment with 1064nm Nd:YAG laser irradiation can enhance estrogen levels in local cartilage tissues by upregulating Cyp19 expression in chondrocytes through photobiomodulation, thereby promoting the proliferation and collagen secretion of chondrocytes to improve cartilage reshaping and stability.

In vivo electrochemical lipolysis of fat in a Yucatan pig model: A proof of concept study

OBJECTIVES

Traditional fat contouring is now regularly performed using numerous office^- based less invasive techniques. However, some limitations of these minimally invasive techniques include high cost or limited selectivity with performing localized contouring and reduction of fat. These shortcomings may potentially be addressed by electrochemical lipolysis (ECLL), a novel approach that involves the insertion of electrodes into tissue followed by application of a direct current (DC) electrical potential. This results in the hydrolysis of tissue water creating active species that lead to fat necrosis and apoptosis. ECLL can be accomplished using a simple voltage-driven system (V-ECLL) or a potential-driven feedback cell (P-ECLL) both leading to water electrolysis and the creation of acid and base in situ. The aim of this study is to determine the long-lasting effects of targeted ECLL in a Yucatan pig model.

METHODS

A 5-year-old Yucatan pig was treated with both V-ECLL and P-ECLL in the subcutaneous fat layer using 80:20 platinum:iridium needle electrodes along an 8 cm length. Dosimetry parameters included 5 V V-ECLL for 5, 10, and 20 minutes, and -1.5 V P-ECLL, -2.5 V P-ECLL, -3.5 V P-ECLL for 5 minutes. The pig was assessed for changes in fat reduction over 3 months with digital photography and ultrasound. After euthanasia, tissue sections were harvested and gross pathology and histology were examined.

RESULTS

V-ECLL and P-ECLL treatments led to visible fat reduction (12.1%-27.7% and 9.4%-40.8%, respectively) and contour changes across several parameters. An increased reduction of the superficial fat layer occurred with increased dosimetry parameters with an average charge transfer of 12.5, 24.3, and 47.5 C transferred for 5 V V-ECLL for 5, 10, and 20 minutes, respectively, and 2.0, 11.5, and 24.0 C for -1.5 V P-ECLL, -2.5 V P-ECLL, -3.5 V P-ECLL for 5 minutes, respectively. These dose-dependent changes were also evidenced by digital photography, gross pathology, ultrasound imaging, and histology.

CONCLUSIONS

ECLL results in selective damage and long-lasting changes to the adipose layer in vivo. These changes are dose-dependent, thus allowing for more precise contouring of target areas. P-ECLL has greater efficiency and control of total charge transfer compared to V-ECLL, suggesting that a low-voltage potentiostat treatment can result in fat apoptosis equivalent to a high-voltage DC system.

Potential-Driven Electrochemical Clearing of Ex Vivo Alkaline Corneal Injuries

Purpose

Corneal chemical injuries (CCI) obscure vision by opacifying the cornea; however, current treatments may not fully restore clarity. Here, we investigated potential-driven electrochemical treatment (P-ECT) to restore clarity after alkaline-based CCI in ex vivo rabbit corneas and examined collagen fiber orientation changes using second harmonic generation (SHG).

Methods

NaOH was applied to the corneas of intact New Zealand white rabbit globes. P-ECT was performed on the opacified cornea while optical coherence tomography (OCT) imaging (∼35 frames per second) was simultaneously performed. SHG imaging evaluated collagen fiber structure before NaOH application and after P-ECT. Irrigation with water served as a control.

Results

P-ECT restored local optical clarity after NaOH exposure. OCT imaging shows both progression of NaOH injury and the restoration of clarity in real time. Analysis of SHG z-stack images show that collagen fibril orientation is similar between control, NaOH-damaged, and post-P-ECT corneas. NaOH-injured corneas flushed with water (15 minutes) show no restoration of clarity.

Conclusions

P-ECT may be a means to correct alkaline CCI. Collagen fibril orientation does not change after NaOH exposure or P-ECT, suggesting that no irreversible matrix level fiber changes occur. Further studies are required to determine the mechanism for corneal clearing and to ascertain the optimal electrical dosimetry parameters and electrode designs.

Translational Relevance

Our findings suggest that P-ECT is a potentially effective, low-cost treatment for alkaline CCI.

Exploring feedback-controlled versus open-circuit electrochemical lipolysis in ex vivo and in vivo porcine fat: A feasibility study

OBJECTIVES

Minimally invasive fat sculpting techniques are becoming more widespread with the development of office-based devices and therapies. Electrochemical lipolysis (ECLL) is a needle-based technology that uses direct current (DC) to electrolyze tissue water creating acid and base in situ. In turn, fat is saponified and adipocyte cell membrane lysis occurs. The electrolysis of water can be accomplished using a simple open-loop circuit (V-ECLL) or by incorporating a feedback control circuit using a potentiostat (P-ECLL). A potentiostat utilizes an operational amplifier with negative feedback to allow users to precisely control voltage at specific electrodes. To date, the variation between the two approaches has not been studied. The aim of this study was to assess current and charge transfer variation and lipolytic effect created by the two approaches in an in vivo porcine model.

METHODS

Charge transfer measurements from ex vivo V-ECLL and P-ECLL treated porcine skin and fat were recorded at -1 V P-ECLL, -2 V P-ECLL, -3 V P-ECLL, and -5 V V-ECLL each for 5 min to guide dosimetry parameters for in vivo studies. In follow-up in vivo studies, a sedated female Yorkshire pig was treated with both V-ECLL and P-ECLL across the dorsal surface over a range of dosimetry parameters, including -1.5 V P-ECLL, -2.5 V P-ECLL, -3.5 V P-ECLL, and 5 V V-ECLL each treated for 5 min. Serial biopsies were performed at baseline before treatment, 1, 2, 7, 14, and 28 days after treatment. Tissue was examined using fluorescence microscopy and histology to compare the effects of the two ECLL approaches.

RESULTS

Both V-ECLL and P-ECLL treatments induced in-vivo fat necrosis evident by adipocyte membrane lysis, adipocyte denuclearization, and an acute inflammatory response across a 28-day longitudinal study. However, -1.5 V P-ECLL produced a smaller spatial necrotic effect compared to 5 V V-ECLL. In addition, 5 V V-ECLL produced a comparable necrotic effect to that of -2.5 V and -3.5 V P-ECLL.

CONCLUSIONS

V-ECLL and P-ECLL at the aforementioned dosimetry parameters both achieved fat necrosis by adipocyte membrane lysis and denuclearization. The -2.5 V and -3.5 V P-ECLL treatments created spatially similar fat necrotic effects when compared to the 5 V V-ECLL treatment. Quantitatively, total charge transfer between dosimetry parameters suggests that -2.5 V P-ECLL and 5 V V-ECLL produce comparable electrochemical reactions. Such findings suggest that a low-voltage closed-loop potentiostat-based system is capable of inducing fat necrosis to a similar extent compared to that of a higher voltage direct current system.

Electrochemical Therapy of In Vivo Rabbit Cutaneous Tissue

OBJECTIVES

To examine the acid-base and histological changes in in vivo rabbit cutaneous tissue after electrochemical therapy.

STUDY DESIGN

In vivo rabbit tissue study.

METHODS

The shaved skin on the backs of female Oryctolagus cuniculi were assigned to treatments with or without tumescence with normal saline. Two platinum-needle electrodes were inserted into each treatment area and connected to a direct current (DC) power supply. Voltage (3-5 V) was varied and applied for 5 minutes. The wound-healing process was monitored via digital photography and ultrasonography until euthanasia at day 29. Treatment areas were biopsied, and specimens were sectioned through a sagittal midline across both electrode insertion sites. Samples were then evaluated utilizing light microscopy (hematoxylin and eosin, Masson's Trichrome, and Picrosirius red).

RESULTS

Treatment sites developed mild inflammation that dissipated at lower voltages or became scabs at higher voltages. Ultrasonography demonstrated acoustic shadowing with spatial spread that increased with increasing voltage application. The 4- and 5-V sites treated with saline had localized areas of increased tissue density at day 29. Although specimens treated with 3 V did not look significantly different from control tissue, 4- and 5-V samples with and without saline tumescence had finer, less-organized collagen fibers and increased presence of fibrocytes and inflammatory infiltrates.

CONCLUSIONS

Electrochemical therapy caused localized injury to in vivo rabbit cutaneous tissue, prompting regenerative wound repair. With future development, this technology may offer precise, low-cost rejuvenation to restore the functionality and appearance of dermal scars and keloids.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:E2196-E2203, 2021.

Effects of electromechanical reshaping on mechanical behavior of exvivo bovine tendon

BACKGROUND

Electromechanical reshaping is a novel, minimally invasive means to induce mechanical changes in connective tissues, and has the potential to be utilized in lieu of current orthopedic therapies that involve tendons and ligaments. Electromechanical reshaping delivers an electrical current to tissues while under mechanical deformation, causing in situ redox changes that produce reliably controlled and spatially limited mechanical and structural changes. In this study, we examine the feasibility of altering Young's modulus and inducing a shape deformation using an ex vivo bovine Achilles tendon model.

METHODS

Tendon was mechanically deformed in two different modes: (1) elongation to assess for tensile modulus and (2) compression to assess for compressive modulus. Electromechanical reshaping was applied to tendon specimens via flat plate platinum electrodes (6 V, 3 min) while simultaneously under mechanical strain for 15 min.

FINDINGS

In elongation mode, post-electromechanical reshaping samples demonstrated a significant decrease in Young's modulus compared to pretreatment samples (66.02 and 45.12 MPa, respectively, p < 0.0049). In compression mode, posttreatment samples illustrated a significant shape change, with an increase in diameter (10.62 to 11.36 mm, p < 0.05) and decrease in thickness (4.13 to 3.62 mm, p < 0.05).

INTERPRETATION

Results demonstrated a tissue softening effect without lengthening deformation during elongation, and a shortening effect without compromising compressive stiffness during compression. Electromechanical reshaping's reliable, low-cost, and efficacious methodology in inducing mechanical and structural connective tissue modifications illustrates a potential for future alternative orthopedic applications. Future studies will optimize and refine electromechanical reshaping to address clinically relevant geometries and methods such as needle techniques.

The biophysical effects of localized electrochemical therapy on porcine skin

BACKGROUND

Minimally-invasive methods to treat scars address a common pathway of altering collagen structure, leading to collagen remodeling.

OBJECTIVE

In this study, we employed in situ redox chemistry to create focal pH gradients in skin, altering dermal collagen, in a process we refer to as electrochemical therapy (ECT). The effects of ECT to induce biochemical and structural changes in ex vivo porcine skin were examined.

METHODS

During ECT, two platinum electrodes were inserted into fresh porcine skin, and following saline injection, an electrical potential was applied. pH mapping, high frequency ultrasonography, and two photon excitation microscopy and second harmonic generation (SHG) microscopy were used to evaluate treatment effects. Findings were correlated with histology.

RESULTS

Following ECT, pH mapping depicted acid and base production at anode and cathode sites respectively, with increasing voltage and application time. Gas formation during ECT was observed with ultrasonography. Anode sites showed significant loss of SHG signal, while cathode sites showed disorganized collagen structure with fewer fibrils emitting an attainable signal. Histologically, collagen denaturation at both sites was confirmed.

CONCLUSION

We demonstrated the production of in situ acid and base in skin occurring via ECT. The effects chemically and precisely alter collagen structure through denaturation, giving insight on the potential of ECT as a simple, low-cost, and minimally-invasive means to remodel skin and treat scars.

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

Importance

The classic management of burn scars and other injuries to the skin has largely relied on soft-tissue transfer to resurface damaged tissue with local tissue transfer or skin graft placement. In situ generation of electrochemical reactions using needle electrodes and an application of current may be a new approach to treat scars and skin.

Objective

To examine the changes in optical, mechanical, and acoustic impedance properties in porcine skin after electrochemical therapy.

Design, Setting, and Participants

This preclinical pilot study, performed from August 1, 2015, to November 1, 2016, investigated the effects of localized pH-driven electrochemical therapy of ex vivo porcine skin using 24 skin samples. Platinum-plated needle electrodes were inserted into fresh porcine skin samples. A DC power supply provided a voltage of 4 to 5 V with a 3-minute application time. Specimens were analyzed using optical coherence tomography, optical coherence elastography, and ultrasonography. Ultrasonography was performed under 3 conditions (n = 2 per condition), optical coherence tomography was performed under 2 conditions (n = 2 per condition), and optical coherence elastography was performed under 2 conditions (n = 2 per condition). The remaining samples were used for the positive and negative control groups (n = 10).

Exposures

Platinum-plated needle electrodes were inserted into fresh porcine skin samples. A DC power supply provided a voltage of 4 to 5 V with a 3-minute application.

Main Outcomes and Measures

Tissue softening was observed at the anode and cathode sites as a result of electrochemical modification. Volumetric changes were noted using each optical and acoustic technique.

Results

A total of 24 ex vivo porcine skin samples were used for this pilot study. Optical coherence tomography measured spatial distribution of superficial tissue changes around each electrode site. At 4 V for 3 minutes, a total volumetric effect of 0.47 mm3 was found at the anode site and 0.51 mm3 at the cathode site. For 5 V for 3 minutes, a total volumetric effect of 0.85 mm3 was found at the anode site and 1.05 mm3 at the cathode site.

Conclusions and Relevance

Electrochemical therapy is a low-cost technique that is on par with the costs of suture and scalpel. The use of electrochemical therapy to create mechanical and physiologic changes in tissue has the potential to locally remodel the soft-tissue matrix, which ultimately may lead to an inexpensive scar treatment or skin rejuvenation therapy.

Level of Evidence

NA.

Anatomy and Surgical Approaches to the Rabbit Nasal Septum

Importance

The rabbit is the primary animal model used to investigate aspects of nasal surgery. Although several studies have used this model, none has provided a comprehensive analysis of the surgical anatomy and techniques used to gain access to the rabbit nasal fossae and septum.

Objective

To describe and optimize the surgical anatomy and approach to the rabbit nasal vault and septal cartilage.

Design, Setting, and Participants

In an ex vivo animal study conducted at an academic medical center, preliminary cadaveric dissections were performed on rabbit head specimens to establish familiarity with relevant anatomy and rehearse various approaches. Live Pasteurella-free New Zealand white rabbits (3.5-4.0 kg) were used to further develop this surgical technique developed here. Access of the nasal vault was gained through a midline nasal dorsum incision and creation of an osteoplastic flap with a drill. Submucosal resection was performed with preservation of the mucoperichondrium. All rabbits were monitored daily for 4 weeks in the postoperative period for signs of infection, pain, and complications. The study was conducted from June 1, 2014, to December 1, 2014.

Main Outcomes and Measures

Surgical anatomy and techniques used to gain access to the rabbit nasal vault and harvest septal cartilage.

Results

Four Pasteurella-free New Zealand white rabbits (Western Organ Rabbit Co), ranging in age from 9 to 12 months and weighing between 3.5 and 4.0 kg, were used in this study. Initial dissections demonstrated the feasibility of harvesting septal cartilage while preserving the mucoperichondrial envelope. Access to the nasal vault through this 3-osteotomy approach allowed for maximal exposure to the nasal cavity bilaterally while maintaining the integrity of the mucoperichondrium following septal cartilage harvest. The maximum amount of bulk, en bloc, cartilage harvested was 1.0 × 2.5 cm. Following surgical dissection, all animals maintained adequate airway patency and support to midface structures. Furthermore, all specimens preserved the integrity of the mucoperichondrium, septum, vascular anatomy, and airway dynamics. No operative complications, postoperative airway compromise, or infections were observed.

Conclusions and Relevance

Access to the rabbit nasal vault and septal cartilage is feasible through a variety of surgical approaches and techniques. To date, this is the first study to meticulously document and review the surgical approaches to the rabbit nasal cavity. This approach describes a novel, 3-osteotomy method of accessing the nasal cavity bilaterally and successfully harvesting rabbit septal cartilage in a submucoperichondrial plane. The ability to preserve native anatomy and function allows for improved outcomes in translational and animal guided clinical research.

Level of Evidence

NA.

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

IMPORTANCE

The prominent ear is a common external ear anomaly that is usually corrected through surgery. Electromechanical reshaping (EMR) may provide the means to reshape cartilage through the use of direct current (in milliamperes) applied percutaneously with needle electrodes and thus to reduce reliance on open surgery.

OBJECTIVE

To determine the long-term outcomes (shape change, cell viability, and histology) of a more refined EMR voltage and time settings for reshaping rabbit auricle.

DESIGN, SETTING, AND SUBJECTS

The intact ears of 14 New Zealand white rabbits were divided into 2 groups. Group 1 received 4 V for 5 minutes (5 ears), 5 V for 4 minutes (5 ears), or no voltage for 5 minutes (control; 4 ears). Group 2 received an adjusted treatment of 4 V for 4 minutes (7 ears) or 5 V for 3 minutes (7 ears). A custom mold with platinum electrodes was used to bend the pinna and to perform EMR. Pinnae were splinted for 6 months along the region of the bend. Rabbits were killed humanely and the ears were harvested the day after splint removal. Data were collected from March 14, 2013, to July 8, 2014, and analyzed from August 29, 2013, to March 1, 2015.

MAIN OUTCOMES AND MEASURES

Bend angle and mechanical behavior via palpation were recorded through photography and videography. Tissue was sectioned for histologic examination and confocal microscopy to assess changes to microscopic structure and cell viability.

RESULTS

Rabbits ranged in age from 6 to 8 months and weighed 3.8 to 4.0 g. The mean (SD) bend angles were 81° (45°) for the controls and, in the 5 EMR groups, 72° (29°) for 4 V for 4 minutes, 101° (19°) for 4 V for 5 minutes, 78° (18°) for 5 V for 3 minutes, and 126° (21°) for 5 V for 4 minutes. At 5 V, an increase in application time from 3 to 4 minutes provided significant shape change (78° [18°] and 126° [21°], respectively; P = .003). Pinnae stained with hematoxylin-eosin displayed localized areas of cell injury and fibrosis in and around electrode insertion sites. This circumferential zone of injury (range, 1.3-2.1 mm) corresponded to absence of red florescence on the cell viability assay.

CONCLUSIONS AND RELEVANCE

In this in vivo study, EMR produces shape changes in the intact pinnae of rabbits. A short application of 4 V or 5 V can achieve adequate reshaping of the pinnae. Tissue injury around the electrodes is modest in spatial distribution. This study provides a more optimal set of EMR variables and a critical step toward evaluation of EMR in clinical trials.

LEVEL OF EVIDENCE

NA.

Monitoring of Biological Changes in Electromechanical Reshaping of Cartilage Using Imaging Modalities

Electromechanical reshaping (EMR) is a promising surgical technique used to reshape cartilage by direct current and mechanical deformation. It causes local stress relaxation and permanent alterations in the shape of cartilage. The major advantages of EMR are its minimally invasive nature and nonthermal electrochemical mechanism of action. The purpose of this study is to validate that EMR does not cause thermal damage and to observe structural changes in post-EMR cartilage using several imaging modalities. Three imaging modality metrics were used to validate the performance of EMR by identifying structural deformation during cartilage reshaping: infrared thermography was used to sense the temperature of the flat cartilages (16.7°C at 6 V), optical coherence tomography (OCT) was used to examine the change in the cartilage by gauging deformation in the tissue matrix during EMR, and scanning electron microscopy (SEM) was used to show that EMR-treated cartilage is irregularly arranged and the thickness of collagen fibers varies, which affects the change in shape of the cartilage. In conclusion, the three imaging modalities reveal the nonthermal and electromechanical mechanisms of EMR and demonstrate that use of an EMR device is feasible for reshaping cartilage in a minimally invasive manner.

Modular Component Assembly Approach to Microtia Reconstruction

BACKGROUND

Current methods of microtia reconstruction include carving an auricular framework from the costal synchondrosis. This requires considerable skill and may create a substantial defect at the donor site.

OBJECTIVE

To present a modular component assembly (MCA) approach that minimizes the procedural difficulty with microtia repair and reduces the amount of cartilage to a single rib.

DESIGN, SETTING, AND PARTICIPANTS

Ex vivo study and survey. A single porcine rib was sectioned into multiple slices using a cartilage guillotine, cut into components outlined by 3-dimensional printed templates, and assembled into an auricular scaffold. Electromechanical reshaping was used to bend cartilage slices for creation of the helical rim. Chondrocyte viability was confirmed using confocal imaging. Ten surgeons reviewed the scaffold constructed with the MCA approach to evaluate aesthetics, stability, and clinical feasibility. The study was conducted from June 5 to December 18, 2014.

MAIN OUTCOMES AND MEASURES

The primary outcome was creation of a modular component assembly method that decreases the total amount of rib needed for scaffold construction, as well as overall scaffold acceptability. The surgeons provided their assessments through a Likert-scale survey, with responses ranging from 1 (disagree with the statement) to 5 (agree with the statement). Thus, a higher score represents that the surgeon agrees that the scaffold is structurally and aesthetically acceptable and feasible.

RESULTS

An auricular framework with projection and curvature was fashioned from 1 rib. The 10 surgeons who participated in the survey indicated that the MCA scaffold would meet minimal aesthetic and anatomic acceptability. When embedded under a covering, the region of the helix and antihelix of the scaffold scored significantly higher on the assessment survey than that of an embedded alloplast implant (mean [SD], 4.6 [0.97] vs 3.5 [1.27]; P = .007). Otherwise, no significant difference was found between the embedded MCA and alloplast implants (4.42 [0.48] vs 3.87 [0.41]; P = .13). Cartilage prepared with electromechanical reshaping was viable.

CONCLUSIONS AND RELEVANCE

This study demonstrates that 1 rib can be used to create an aesthetic and durable framework for microtia repair. Precise assembly and the ability to obtain thin, uniform slices of cartilage were essential. This cartilage-sparing MCA approach may be an alternative to classic techniques.

LEVEL OF EVIDENCE

NA.

Long-term in vivo electromechanical reshaping for auricular reconstruction in the New Zealand white rabbit model

OBJECTIVES/HYPOTHESIS

To demonstrate the dosimetry effect of electromechanical reshaping (EMR) on cartilage shape change, structural integrity, cellular viability, and remodeling of grafts in an in vivo long-term animal model.

STUDY DESIGN

Animal study.

METHODS

A subperichondrial cartilaginous defect was created within the base of the pinna of 31 New Zealand white rabbits. Autologous costal cartilage grafts were electromechanically reshaped to resemble the rabbit auricular base framework and mechanically secured into the pinna base defect. Forty-nine costal cartilage specimens (four control and 45 experimental) successfully underwent EMR using a paired set of voltage-time combinations and survived for 6 or 12 weeks. Shape change was measured, and specimens were analyzed using digital imaging, tissue histology, and confocal microscopy with LIVE-DEAD viability assays.

RESULTS

Shape change was proportional to charge transfer in all experimental specimens (P < .01) and increased with voltage. All experimental specimens contoured to the auricular base. Focal cartilage degeneration and fibrosis was observed where needle electrodes were inserted, ranging from 2.2 to 3.9 mm. The response to injury increased with increasing charge transfer and survival duration.

CONCLUSIONS

EMR results in appropriate shape change in cartilage grafts with chondrocyte injury highly localized. These studies suggest that elements of auricular reconstruction may be feasible using EMR. Extended survival periods and further optimization of voltage-time pairs are necessary to evaluate the long-term effects and shape-change potential of EMR.

LEVELS OF EVIDENCE

NA.

In vivo needle-based electromechanical reshaping of pinnae: New Zealand White rabbit model

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 SPECIMENS

In 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 MEASURES

The 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.

Electromechanical reshaping of ex vivo porcine trachea

OBJECTIVES

The trachea is a composite cartilaginous structure particularly prone to various forms of convexities. Electromechanical reshaping (EMR) is an emerging technique used to reshape cartilaginous tissues by applying electric current in tandem with imposed mechanical deformation to achieve shape change. In this study, EMR was used to reshape tracheal cartilage rings to demonstrate the feasibility of this technology as a potentially minimally invasive procedure to alter tracheal structure.

STUDY DESIGN

Controlled laboratory study using ex vivo porcine tracheae.

METHODS

The natural concavity of each porcine tracheal ring was reversed around a cork mandrel. Two pairs of electrodes were inserted along the long axis of the tracheal ring and placed 1.5 millimeters from the midline. Current was applied over a range of voltages (3 volts [V], 4V, and 5V) for either 2 or 3 minutes. The degree of EMR-induced reshaping was quantified from photographs using digital techniques. Confocal imaging with fluorescent live and dead assays was conducted to determine viability of the tissue after EMR.

RESULTS

Specimens that underwent EMR for 2 or 3 minutes at 4V or 5V were observed to have undergone significant (P < .05) reshaping relative to the control. Viability results demonstrated that EMR reshaping occurs at the expense of tissue injury, although the extent of injury is modest relative to conventional techniques.

CONCLUSION

EMR reshapes tracheal cartilage rings as a function of voltage and application time. It has potential as a minimally invasive and cost-efficient endoscopic technology to treat pathologic tracheal convexities. Given our findings, consideration of EMR for use in larger ex vivo tracheal segments and animal studies is now plausible.

The Effect of pH on Rabbit Septal Cartilage Shape Change: Exploring the Mechanism of Electromechanical Tissue Reshaping

INTRODUCTION

Electromechanical reshaping (EMR) involves the application of an electrical current to mechanically deformed cartilage to create sustained tissue shape change. Although EMR may evolve to become an inexpensive and reliable way of producing shape change in cartilage during reconstructive surgery, the precise mechanism of EMR is unknown. We aim to examine the isolated effect of protonation (pH) on shape change in cartilage.

METHODS

Nasal septal cartilages of rabbits were mechanically deformed and placed in a rigid jig. The deformed cartilages were submerged in isotonic phosphate buffered saline baths (osm = 290 mmol/Kg) with a pH of 3 (N = 51), pH of 7 (N = 51), and a pH of 11 (N = 51) for 15 minutes. Following re-equilibration, specimens were removed from their jig and the angle change from baseline was measured using digital micrometry.

RESULTS

Significant shape change was noted in all specimens, with an angle change of 33.6°, 33.3°, and 32.0° experienced by the pH of 3, 7, and 11 groups, respectively. Despite a trend toward increased shape change in the acidic treatment, there was no significant difference between groups.

CONCLUSIONS

Although current evidence indicates that dynamic oxidation-reduction reactions within the extracellular matrix of cartilage may be implicated in EMR-induced shape change, when pH was isolated as a single variable it was not sufficient to produce cartilage shape change.

In-depth analysis of pH-dependent mechanisms of electromechanical reshaping of rabbit nasal septal cartilage

OBJECTIVES/HYPOTHESIS

Electromechanical reshaping (EMR) involves reshaping cartilage by mechanical deformation and delivering electric current to the area around the bend axis, causing local stress relaxation and permanent shape change. The mechanism of EMR is currently unclear, although preliminary studies suggest that voltage and application time are directly related to the concentration and diffusion of acid-base products within the treated tissue with little heat generation. This study aims to characterize local tissue pH changes following EMR and to demonstrate that local tissue pH changes are correlated with tissue damage and shape change.

STUDY DESIGN

Ex vivo animal study involving EMR of rabbit nasal septal cartilage and biochemical estimation of tissue pH changes.

METHODS

The magnitude and diffusion of acid-base chemical products in control (0V, 2 minutes), shape change (4V, 4 minutes; 6V, 1, 2, 4 minutes; 8V, 1, 2 minutes), and tissue damage (8V, 4, 5 minutes; 10V, 4, 5 minutes) parameters following EMR are approximated by analyzing local pH changes after pH indicator application.

RESULTS

There is a direct relationship between total charge transfer and extent of acid-base product diffusion (P <0.05). A "pH transition zone" is seen surrounding the bend apex above 8V, 2 minutes. Colorimetric analysis suggests that small local pH changes (10(-8) hydrogen ions) are at least partly implicated in clinically efficacious EMR.

CONCLUSIONS

These results provide additional insight into the translational applications of EMR, particularly the relationship among pH changes, shape change, and tissue injury, and are integral in optimizing this promising technology for clinical use.

Ex vivo electromechanical reshaping of costal cartilage in the New Zealand white rabbit model

OBJECTIVES/HYPOTHESIS

Determine the effective electromechanical reshaping (EMR) parameters for shape change and cell viability in the ex vivo rabbit costal cartilage model.

STUDY DESIGN

Ex vivo animal study combined with computer modeling to guide electrode placement and polarity selection.

METHODS

Rabbit costal cartilages were secured in a jig that approximated the shape of the rabbit auricle framework. Finite element modeling was used to select the initial electrode geometry, polarity, spacing, and estimate dosimetry parameters. Porcine costal cartilage was utilized to refine the selection of dosing parameters. Parametric analysis was performed to determine the effect of voltage and application time on tissue shape change. Next, rabbit rib cartilage was reshaped, varying voltage and application time to identify the lowest parameters to produce acceptable shape change mimicking native auricular cartilage. Acceptable qualitative shape change was determined on a five-point Likert scale analyzed using one-way general linear analysis of variance. Confocal microscopy with live/dead cell viability analysis determined the degree of injury and the distribution of live and dead cells.

RESULTS

The minimum acceptable deformation of rabbit costal cartilage was found at 4 V-3 minutes. Viability analysis of cartilage reshaped at 4 V-3 minutes demonstrates cell injury extending 2 mm away from each electrode with viable cells found between the electrodes.

CONCLUSIONS

The EMR parameters of 4 V-3 minutes demonstrates appropriate shape change producing grafts that resemble the native auricle and contains the viable cells adequate for clinical evaluation. The rabbit auricular reconstruction model using EMR is a feasible one.

Changes in the tangent modulus of rabbit septal and auricular cartilage following electromechanical reshaping

Transforming decades' old methodology, electromechanical reshaping (EMR) may someday replace traditionally destructive surgical techniques with a less invasive means of cartilage reshaping for reconstructive and esthetic facial surgery. Electromechanical reshaping is essentially accomplished through the application of voltage to a mechanically deformed cartilage specimen. While the capacity of the method for effective reshaping has been consistently shown, its associated effects on cartilage mechanical properties are not fully comprehended. To begin to explore the mechanical effect of EMR on cartilage, the tangent moduli of EMR-treated rabbit septal and auricular cartilage were calculated and compared to matched control values. Between the two main EMR parameters, voltage and application time, the former was varied from 2-8 V and the latter held constant at 2 min for septal cartilage, 3 min for auricular cartilage. Flat platinum electrodes were used to apply voltage, maintaining the flatness of the specimens for more precise mechanical testing through a uniaxial tension test of constant strain rate 0.01 mm/s. Above 2 V, both septal and auricular cartilage demonstrated a slight reduction in stiffness, quantified by the tangent modulus. A thermal effect was observed above 5 V, a newly identified EMR application threshold to avoid the dangers associated with thermoforming cartilage. Optimizing EMR application parameters and understanding various side effects bridge the gap between EMR laboratory research and clinical use, and the knowledge acquired through this mechanical study may be one additional support for that bridge.

Electromechanical reshaping of costal cartilage grafts: a new surgical treatment modality

OBJECTIVES/HYPOTHESIS

Needle electrode-based electromechanical reshaping (EMR) is a novel, ultra-low-cost nascent surgical technology to reshape cartilage with low morbidity. EMR uses direct current to induce mechanical relaxation in cartilage that is first deformed into a required geometry, which in turn leads to permanent shape change. The objective of this study was to determine the effect of EMR voltage and time on the shape change of costal cartilage grafts.

STUDY DESIGN

EMR of ex vivo porcine costal cartilage.

METHODS

Graft specimens obtained from the central core of porcine costal cartilage were bent at a 90-degree angle with a custom jig and then reshaped via EMR. The effects of voltage (3-7 V) and application time (1-5 minutes) on the amount of shape change were systematically examined. Bend angles were analyzed using analysis of variance and paired t tests to determine significant reshaping times at each voltage setting.

RESULTS

There is a threshold for voltage and time above which the retention of bend angle is statistically significant in treated specimens compared to the control (P < .05). Above the threshold of 3 V, shape retention initially increased with application time for all voltages tested and was then observed to reach a plateau. Shape retention was noted to be greatest at 6 V without a rise in temperature.

CONCLUSIONS

EMR provides a novel method to bend and shape costal cartilage grafts for use in facial plastic surgery. A low voltage can reshape cartilage grafts within several minutes and without the heat generation. This study demonstrates the feasibility of EMR and brings this minimally invasive procedure closer to clinical implementation.

Needle electrode-based electromechanical reshaping of rabbit septal cartilage: a systematic evaluation

Electromechanical reshaping (EMR) provides a means of producing shape change in cartilage by initiating oxidation-reduction reactions in mechanically deformed specimens. This study evaluates the effect of voltage and application time on specimen shape change using needle electrodes. Rabbit septal cartilage specimens (20 x 8 x 1 mm, n = 200) were bent 90 degrees in a precision-machined plastic jig. Optimal electrode placement and the range of applied voltages were estimated using numerical modeling of the initial electric field within the cartilage sample. A geometric configuration of three platinum needle electrodes 2 mm apart from each other and inserted 6 mm from the bend axis on opposite ends was selected. One row of electrodes served as the anode and the other as the cathode. Constant voltage was applied at 1, 2, 4, 6, and 8 V for 1, 2, and 4 minutes, followed by rehydration in phosphate buffered saline. Samples were then removed from the jig and bend angle was measured. In accordance with previous studies, bend angle increased with increasing voltage and application time. Below a voltage threshold of 4 V, 4 minutes, no clinically significant reshaping was observed. The maximum bend angle obtained was 35.7 ± 1.7 º at 8 V, 4 minutes.