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.
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.
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.
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