Controlled-Potential Electromechanical Reshaping of Cartilage

An alternative to conventional "cut-and-sew" cartilage surgery, electromechanical reshaping (EMR) is a molecular-based modality in which an array of needle electrodes is inserted into cartilage held under mechanical deformation by a jig. Brief (ca.2min) application of an electrochemical potential at the water-oxidation limit results in permanent reshaping of the specimen. Highly sulfated glycosaminoglycans within the cartilage matrix provide structural rigidity to the tissue through extensive ionic-bonding networks; this matrix is highly permselective for cations. Our studies indicate that EMR results from electrochemical generation of localized, low-pH gradients within the tissue: fixed negative charges in the proteoglycan matrix are protonated, resulting in chemically induced stress relaxation of the tissue. Re-equilibration to physiological pH restores the fixed negative charges, and yields remodeled cartilage that retains a new shape approximated by the geometry of the reshaping jig. Changing shape: In a molecular-based alternative to "cut-and-suture" cartilage surgery, electrodes are inserted into tissues held under mechanical deformation. Electrolysis at the water-oxidation limit generates highly localized regions of low pH that chemically relax the stressed tissue. Re-equilibration to physiological pH yields cartilage permanently remodeled to the new shape of the jig.