An apparatus and method for implanting and securing an implanted medical device in a recipient. The implantable medical device of the generally includes a stimulating lead assembly that comprises an elongate carrier member having at least one stimulating element positioned thereon. The stimulating lead assembly further has an expandable portion thereon configured to be inserted into said reference structure in a first dimension, expand to a second dimension, and interact with a portion of the reference structure to help longitudinally secure the carrier member in the recipient.