An access device comprises a thin-walled sheath that is insertable into a patient through a small surgically created incision. The incision may be created using a cutdown or a
percutaneous method such as that known as the Seldinger technique. Once inserted and advanced to the target
surgical site, the sheath is selectively, and controllably, expanded to a desired
diameter. The
thin wall of the sheath is fabricated from a rectangular piece of material such as
metal or plastic with two
cut edges. The rectangular piece of
metal or plastic is rolled tightly to create the small
diameter configuration that is inserted into the patient. A
cam or control member is affixed to the innermost edge of the rectangular piece of
metal or plastic. The control member extends to the proximal most portion of the sheath. By rotating the control member, the operator causes the
thin wall piece of rolled material to unfurl into a larger or smaller
diameter, depending on the direction of rotation. A mechanical lock at the distal end of the sheath permits the control member to be selectively constrained from rotation and thus lock the sheath diameter in place.