A thermally active member comprises a shape memory material. The method of placement of the thermally active member facilitates transition of shape memory material between a simple undefined geometry, such as a substantially linear shape, to a complex predetermined shape memory form, such as a coiled shape. The preferred complex geometry may be described as an intervertebral cage or cage fusion device. The device may be placed into a space surgically created between two vertebrae through an access channel that is less than one third of its final deployed cross sectional dimension.