Comparative Randomized Clinical Study Between the Discectomy with Prosthetic Disc Nucleus (PDN) Device Implantation and Discectomy only in treatment of Degenerative Lumbar Disc Disease

Abstract

The normal disc is a umque mixed structure largely comprised of two types of tissue a tough, outer fibrous portion (annulus) and a softer inner part (nucleus). The annulus is built much like a laminated automobile tire, measuring about 10-15 mm in both height and thickness36• The collagen fibers of the outer ligamentous ring, or annulus, are laid down in 15 to 20 multiple plies, with the fibers inserted into the superior and inferior vertebral bodies of each segment at roughly a 60 degree angle in both directions, binding the adjacent vertebrae together99. Inside the thick fibrous band is the hygroscopic, vaguely encapsulated, semifluid nucleus positioned like the liquid core of a golf ball. This gel serves to keep the annulus tight (like the air inside the tire) 98. In discal degeneration, the sequence usually follows a

pattern: as the nucleus loses its water-binding ability and deflates, as though the air had been let out of a tire, the height descends and the annulus buckles36• Discal mechanics change. As the laminated plies begin to separate, both circumferential and radial tears may occur96 .