Artificial intervertebral disc replacements incorporating reinforced wall sections

#This invention relates generally to surgical techniques and prosthetic components therefore and, in particular, to intervertebral disc replacement apparatus and methods of implanting the same.

#Eighty-five percent of the population will experience low back pain at some point. Fortunately, the majority of people recover from their back pain with a combination of benign neglect, rest, exercise, medication, physical therapy, or chiropractic care. A small percent of the population will suffer chronic low back pain. The cost of treatment of patients with spinal disorders plus the patient's lost productivity is estimated at 25 to 100 billion dollars annually.

#Seven cervical (neck), 12 thoracic, and 5 lumbar (low back) vertebrae form the normal human spine. Intervertebral discs reside between adjacent vertebra with two exceptions. First, the articulation between the first two cervical vertebrae does not contain a disc. Second, a disc lies between the last lumbar vertebra and the sacrum (a portion of the pelvis).

#FIG. 1 is an axial cross section through an ADR constructed in accordance with this invention;

#FIG. 2 is an axial cross section through another embodiment of an ADR according to this invention;

#FIG. 3 is an axial cross section through an alternative ADR embodiment;

#Turning now to the various drawings, FIG. 1 is an axial cross section through an ADR constructed in accordance with this invention. Area 102 represents a compressible or resilient cushioning material, such as, hydrogel, polyurethane, or other polymer, including elastomers. The outer wall 104 of the ADR includes one or more areas with increased radial stiffness. For example, note that the portion 106 of the wall in this case is intentionally thickened to increase the radial stiffness of that portion.

#In addition to thickening a portion of the wall, a different material may be used, provided either through bonding or through a change in composition. Alternatively, a material may be used that is strengthened, fortified, reinforced or otherwise stiffened through the application of energy or a chemical. For example, ultraviolet light or another form of radiation may be used to locally stiffen a section of the wall, as would be the case with certain types of polymerization techniques. Or a chemical may be injected into the wall causing a change in durometer. An advantage of these alternative techniques is that the stiffening may be carried out with the ADR in situ, perhaps through the very defect in the annulus fibrosis (AF) to be fortified.

#FIG. 2 is an axial cross section through another embodiment of an ADR according to this invention. In this case, a portion of the wall contains a material 202 with increased durometer.