Lumbar Disc Replacement
The spine is composed of individual bones called vertebrae. Lumbar vertebrae are stacked one on top of another and are separated by the intervertebral discs, which act as cushions or shock absorbers. A circle of bone extends from the vertebral body back around the sac of nerves and spinal cord. This circular protective tube of bone, called the spinal canal, protects the spinal cord and spinal nerves. In the lumbar spine the spinal nerves exit the spinal canal between the vertebrae at each level. Two nerves exit each level, one on the left and one on the right. These nerves exit through openings called foramina [Figure 1].
Figure 1
The goal of lumbar disc replacement is to relieve the pain caused by pinched nerves or discogenic pain in the lumbar spine this is done by replacing a diseased or damaged disc with a specialized metal and polyethylene implant. Through a small incision in the abdomen, the diseased disc is removed from between the vertebral bodies. The end surfaces of the vertebral bodies are cleared of all diseased disc cartilage and are readied for the metal implants of the prosthesis. The vertebral bodies are spread apart to relieve the pressure on the pinched nerve root and to accept the prosthesis. Metal implants of the appropriate size are selected and inserted into the opening, and then tapped into position. The polyethylene sliding core is inserted between the implants. The spine is returned to normal posture which seats the implants into the vertebral bones and holds the sliding core in position. The position of the prosthesis is carefully evaluated visually and with x-rays. The implant is designed to preserve spinal motion and keep the lumbar spine properly aligned [Figure 2].
Figure 2
