Patent ID: 8292928

Claim:
An axially-extending implantable spinal fusion rod for adjusting a distance between two adjacent vertebral bodies in a spine, said rod comprising: an elongated body dimensioned for implantation along an axis extending from an access point on the anterior surface of the sacrum and for maintaining the distance between the two adjacent vertebral bodies; a first section near a leading end of the rod that has a first threading for engaging with a first vertebral body, the first threading comprising a first major diameter and a first minor diameter; a second section near a trailing end of the rod that has a second threading for engaging with a second vertebral body that is located inferiorly relative to the first vertebral body, the second threading comprising a second major diameter and a second minor diameter; and an intermediate section extending between the distal and proximal sections, the intermediate section being sized and configured for maintaining the distance between the two vertebral bodies; wherein the first major diameter of the first threading is less than the second major diameter of the second threading; wherein a first thread pitch in the first section is finer relative to a second thread pitch in the second section such that advancement of the first section distally into the first vertebral body by rotation causes an increase in distance between the first and second vertebral bodies and wherein a ratio of the axial length of the second threading to the second minor diameter is within the range of approximately 1.27 to 3.53.