Abstract: A method of treating a herniated intervertebral disc includes inserting a heat-transfer area of a tube containing a fluid into a spinal column and transferring heat between the tube and a tissue. Vapor flows from an evaporator zone of the tube to a condenser zone and liquid flows from the condenser zone to the evaporator zone. Insulation material can be removed from the tube to adjust the heat-transfer area of the tube. The tube is configured such that when a temperature of a heat portal area of the tube is changed fluid changes state and flows to the heat-transfer area. The tube also contains a wick structure to assist liquid flow by way of capillary action. In addition, the tube includes a flexible segment that conforms to the inner curved surface of the annulus fibrosus of the intervertebral disc.