rhizotomy: surgical procedure in which spinal nerve roots are cut; done (anterior roots) to relieve intractable pain or (posterior roots) to stop severe muscle spasms
operation: a medical procedure involving an incision with instruments; performed to repair damage or arrest disease in a living body
saponification: a chemical reaction in which an ester is heated with an alkali (especially the alkaline hydrolysis of a fat or oil to make soap)