The Effect of pH on Rabbit Septal Cartilage Shape Change: Exploring the Mechanism of Electromechanical Tissue Reshaping (original) (raw)
Related papers
The Laryngoscope, 2014
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.
pH-dependent mechanisms of electromechanical cartilage reshaping
Photonic Therapeutics and Diagnostics VII, 2011
Electromechanical reshaping of cartilage is a novel modality that has significant clinical applications in otolaryngology and plastic surgery. Although EMR dosimetry has been extensively studied, little is known about the mechanisms of EMR, of which local tissue pH changes is believed to play a role. In this study, rabbit nasal septal cartilage is subject to a number of experiments aimed at elucidating pH-related changes using phenol red. The lateral extent and magnitude of pH change as well as factors that impact pH change are studied. Increasing voltage and application appear to increase the area and intensity of color change. With parameters known to produce thermal tissue injury, a transitional zone likely representing a confluence of acid-base products is noted in the region around the bend axis. Furthermore, rehydration and pH indicator application time do not appear to play a role in the quality of pH change. These simple experiments may provide insight into the role of pH changes in EMR that may allow correlation of dosimetry to tissue damage, further optimizing the clinical potential of EMR.
Annals of Biomedical Engineering, 2006
Electromechanical reshaping (EMR) of facial cartilage has recently been developed as an alternative to classic surgical techniques to alter cartilage shape. This study focuses on determining the underlying physical mechanisms responsible for shape change (stress relaxation) in mechanically deformed facial cartilage specimens exposed to constant electric fields. Flat porcine nasal septal cartilage specimens were deformed by an aluminum jig into semicylindrical shapes while a constant electric voltage was applied to the concave and convex surfaces of the specimen. Mechanical stress, electric current and resistance were measured during voltage application. Specimen shape retention was measured as retained bend angle. Total electric charge transferred in the electric circuit was calculated from the electric current measurement. Electrical resistance, transferred charge and the bend angle increase with increase in voltage application time until bend angle reaches maximum value determined by the jig geometry. Then, the bend angle decreases and electrical parameters nearly saturate. The time dependent behavior of electric current was analyzed using the Cottrell equation. The observed changes in electric current suggest that during the initial 1-2 min of EMR nonlinear diffusion determines electro-chemical reaction rates, which are then followed by a linear diffusion dominated process. Close correlation between alteration of cartilage mechanical state and change in its electrical properties suggest that an electro-chemical reaction is the dominant mechanism behind EMR.
Electromechanical reshaping of septal cartilage
The Laryngoscope, 2010
Objectives: This study describes the process of tissue electroforming and how shape changes in cartilage can be produced by the application of direct current (DC). The dependence of shape change on voltage and application time is explored. Study Design: Basic investigation using ex vivo porcine septal cartilage grafts and electromechanical cartilage deformation focused on development of a new surgical technique. Methods: Uniform flat porcine nasal septal cartilage specimens were mechanically deformed between two semicircular aluminum electrodes. DC current was applied to establish charge separation and electrical streaming potential. Voltage (0 -3.5 V) and application time (0 -5 minutes) were varied. Shape change was measured, and shape retention was calculated using analytic representation. The effect of the direction of applied current on shape change was evaluated by switching the polarities of electrodes and using parameters of 0 to 5.5 V and 5 minutes. Temperature during reshaping was monitored with a thermocouple, and surface features were evaluated using light microscopy. Results: Reshaped specimen demonstrated mechanical stability similar to native cartilage tissue. Shape retention strongly correlated with increasing voltage and application time. Only a small current (<0.1 A) through the tissue was measured. Temperature change was less than 2°C during electroforming, suggesting that electroforming likely results from some nonthermal mechanisms. Surface features indicated that electrodeposition may occur depending on electrode material and magnitude of the applied voltage. Conclusions: These find-ings demonstrate that cartilage can be reshaped through the process we have described as "electroforming" by generating intrinsic differences in charge separation with negligible heat production.
2009
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.
Photonic Therapeutics and Diagnostics V, 2009
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.
Needle Electrode-Based Electromechanical Reshaping of Cartilage
Annals of Biomedical Engineering, 2010
Electromechanical reshaping (EMR) provides a means of producing shape change in the cartilage by initiating oxidation-reduction reactions in mechanically deformed specimens. This paper evaluates the effect of voltage and application time on specimen shape change using needle electrodes. Rabbit septal cartilage specimens (20 mm × 8 mm × 1 mm, n = 200) were bent 90 • 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 min, 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 min, no clinically significant reshaping was observed. The maximum bend angle obtained was 35.7 ± 1.7 • at 8 V, 4 min.
2011
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.
Energy-based Treatment of Tissue and Assessment VI, 2011
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.
In Vivo Electromechanical Reshaping of Ear Cartilage in a Rabbit Model
JAMA Facial Plastic Surgery, 2013
Objective: To report the first successful study to date of in vivo electromechanical reshaping of ear cartilage in a rabbit model. Methods: Ears of New Zealand white rabbits were reshaped using percutaneous needle electrode electromechanical reshaping (5 V for 4 minutes) and were then bolstered for 4 weeks. Ten ears were treated, with 2 undergoing sham procedures and serving as controls. The treatment was performed using a platinum array of electrodes consisting of 4 parallel rows of needles inserted across the region of flexures in the ear. After 4 weeks, the animals were killed, and the ears were photographed and sectioned for conventional light microscopy and confocal microscopy (live-dead fluorescent assays).