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.