Electromechanical reshaping (EMR) of cartilage is a novel technique that has significant potential for use in facial reconstructive surgery. EMR achieves permanent shape change by initiating electrochemical redox reactions in the vicinity of stress concentrations, thereby altering mechanical properties of tissue matrix. This study reports the use of a six electrode needle-based geometric configuration to reshape cartilage. Rectangular samples (24 x 12 x 1 mm) of rabbit nasal septal cartilages were bent at a right angle in a precision-machined reshaping jig. Two parallel arrays of three platinum needle electrodes were each inserted into cartilage along the bend at 3 mm from the bend line. One array served as an anode and the other as cathode. Constant voltage at 1, 2, 4, 6, and 8 volts was applied to the arrays for 2 minutes. The specimens were then removed from the jig and rehydrated for 15 minutes in phosphate buffered saline. Following rehydration, bend angles and thicknesses were measured. Bend angle increased with increasing voltage and application time. No statistically significant bending was observed below 6 volts for 2 minutes application time. Maximum bend angle of 33 ± 8 degrees or reshaping degree of 33% was observed at 8 volts applied for 2 minutes. Current flow was small (< 0.1 A) for each case. Sample thickness was 0.9 ± 0.2 mm. ANOVA analysis showed that cartilage thickness had no significant impact on the extent of reshaping at given voltage and application time. The six needle electrode geometric configuration conforms to the voltage-and time-dependent trends predicted by previous EMR studies. In the future, the reshaping properties of other geometric configurations will be explored.

The results suggest that reconstruction of the upper airways from LR-OCT imaging data may not need to account for airway curvature to be predictive of surgical effects on airway resistance. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc.

Long-range optical coherence tomography has been developed to image the upper airway, obtaining high resolution, cross-sectional images of the hollow structure. The information obtained from the anatomical structure of the airway is important to objectively identify regions of airway obstruction. This paper describes a technique to create 3D reconstructions of the upper airway from LR-OCT images. Herein we outline the necessary steps to generate these 3D models, including image processing techniques, manual tissue segmentation in Mimics, anatomical curvature bending, and the final STL model rendition. These 3D models were used to qualitatively analyze structural changes before and after surgical interventions. The reconstructions could also be used for further computational fluid dynamics analysis.

Electromechanical reshaping (EMR) of cartilage has been suggested as an alternative to the classical surgical techniques of modifying the shape of facial cartilages. The method is based on exposure of mechanically deformed cartilaginous tissue to a low level electric field. Electro-chemical reactions within the tissue lead to reduction of internal stress, and establishment of a new equilibrium shape. The same reactions offset the electric charge balance between collagen and proteoglycan matrix and interstitial fluid responsible for maintenance of cartilage mechanical properties. The objective of this study was to investigate correlation between the electric charge transferred during EMR and equilibrium elastic modulus.We used a finite element model based on the triphasic theory of cartilage mechanical properties to study how electric charges transferred in the electro-chemical reactions in cartilage can change its mechanical responses to step displacements in unconfined compression. The concentrations of the ions, the strain field and the fluid and ion velocities within the specimen subject to an applied mechanical deformation were estimated and apparent elastic modulus (the ratio of the equilibrium axial stress to the axial strain) was calculated as a function of transferred charge. The results from numerical calculations showed that the apparent elastic modulus decreases with increase in electric charge transfer. To compare numerical model with experimental observation we measured elastic modulus of cartilage as a function of electric charge transferred in electric circuit during EMR. Good correlation between experimental and theoretical data suggests that electric charge disbalance is responsible for alteration of cartilage mechanical properties.

Cryopreservation of cartilage has been investigated for decades and is currently an established protocol. However, the reliability and applicability of cartilage cryopreservation for the use in electromechanical reshaping (EMR) has not been studied exclusively. A system to cryopreserve large numbers of tissue specimens provides a steady source of cartilage of similar quality for experimentation at later dates. This will reduce error that may arise from different cartilage stock, and has the potential to maximize efficiency under time constraints. Our study utilizes a unique methodology to cryopreserve septal cartilage for use in EMR studies. Rabbit septal cartilage specimens were harvested and standardized to 20 x 8 x 1 mm, and placed in one of three solutions (normal saline, PBS, 10% DMSO in PBS) for four hours in a cold storage room at 4 degrees Celsius. Then, each cartilage specimen was vacuumed and sealed in an anti-frost plastic bag and stored in a freezer at -80 degrees Celsius for 1 to 3 weeks duration. EMR was performed using 2 and 6 volts for 2 minutes application time. Bend angle measurements of the cryopreserved cartilage specimens were compared to bend angles of fresh cartilage which underwent EMR using the same parameters. Results demonstrate that normal saline, phosphate buffered saline (PBS), and PBS with DMSO were effective in cryopreservation, and indicated no significant differences in bend angle measurements when compared to no cryopreservation. Our methodology to cryopreserve cartilage specimens provides a successful approach for use in conducting large-scale EMR studies.