Patent ID: 7547324

Claim:
An implantable spinal mobility preservation apparatus, comprising: a intermediate body having a proximal end and a distal end and including at least one flexible element positioned between the proximal end and the distal end; a proximal body including a first retention structure secured to the proximal end of the intermediate body and defining a proximal lumen, with the first retention structure comprising a first external thread oriented for engagement of an axial bore through an caudad vertebral body; a distal body including a second retention structure secured to the distal end of the intermediate body, with the second retention structure comprising a second external thread oriented for engagement of an axial bore through a cephalad vertebral body wherein the pitch of the second external thread is finer than the pitch of the first external thread to induce distraction between the caudad vertebral body and the cephalad vertebral body during implantation; and an expandable membrane secured over at least a portion of the intermediate body, the proximal body, the intermediate body, and the distal body defining a longitudinal axis, with the combination of the proximal body, the intermediate body and the distal body having an aspect ratio of greater than 1 wherein the aspect ratio is the ratio of an overall length along the longitudinal axis to a largest diameter along the overall length with the expandable membrane in an unexpanded configuration.