What is an Artificial Disc?An artificial disc is a prosthetic device inserted between the vertebrae to replace a natural spinal disc. It is designed to mimic the function of a natural disc, preserving mobility within the disc space and throughout the treated vertebral segment The spine consists of bones, discs, muscles and ligaments. The bones, called vertebrae, provide the structure for the spine, while the muscles and ligaments provide support. The discs, located between the vertebrae, function as shock absorbers and also influence the flexibility and mobility of the spine. Each spinal disc is made up of two parts:
When discs become dried out, compressed or otherwise damaged — due to age, genetics and everyday wear-and-tear — the nucleus pulposus material may extrude out of the annulus fibrosis and compress the spinal nerves and/or the spinal cord, causing neck pain, arm pain, numbness and/or muscle weakness, a condition typically referred to as degenerative disc disease (DDD). Natural discs also may acutely dislodge or herniate, causing neck and neurological symptoms in the upper extremities. When non-surgical therapies fail to provide relief from acute disc herniation and/or DDD-related symptoms, your doctor may recommend spine surgery. The goal of surgery is to remove all or part of a damaged disc (discectomy), relieve pressure on the nerves and/or spinal cord (decompression) and to restore spinal stability and alignment after the disc has been removed. Traditionally, spinal fusion has been the "gold standard" for surgically treating disc herniation or DDD. Using bone grafts and instrumentation, such as metal plates and screws, this procedure fuses, or creates a bond between two adjacent vertebrae, ideally stabilizing the segment and providing relief. This procedure has been successful in many patients; however, a potential disadvantage associated with spinal fusion is loss of motion and flexibility in the treated vertebral segment. As an alternative to spinal fusion, your doctor may recommend a surgical procedure called artificial disc replacement. This is a type of joint replacement procedure, or arthroplasty, that involves inserting an artificial disc into the intervertebral space after a natural cervical disc has been removed. The device is designed to preserve mobility within the disc space and throughout the treated vertebral segment. It is designed to function like a joint, replicating the physiological motion (flexion, extension, side bending and rotation) and alignment (height and curvature) of a natural disc. In addition to maintaining physiologic motion, potential advantages of artificial disc surgery include:
Artificial Disc Types and Design Today, there are a variety of spinal artificial discs either on the market, under development or awaiting FDA approval. Although these devices differ in materials, form and function, some universal key design considerations include:
Artificial spinal discs may be classified into two general design types:
Total disc prostheses are typically made of biocompatible materials such as stainless steel, titanium alloy, cobalt chrome, ceramic or other biomaterials such as polyethylene or polyurethane, either alone or in combination. Most of these devices, commonly referred to as articulating devices, are comprised of two or more individual components which articulate (function as a joint) to provide motion. There are, however, non-articulating devices emerging that are made of polymer materials. Artificial Disc History Although the artificial disc is a relative newcomer to the spinal orthopedics market, the technology behind joint replacement is not. Sir John Charnley introduced the first hip prosthesis in 1962 in England; the first hip replacement surgery was performed in the United States around 1969. About the same time, Dr. Frank Gunston, a Canadian orthopedist who collaborated with Dr. Charnley, introduced the first knee prosthesis. Today, hip and knee arthroplasties garner some of the highest ratings in terms of patient satisfaction — more than 90%. The first spinal disc replacement device was introduced by Dr. Ulf Fernström in Sweden in the early 1960s. The implant consisted of a steel ball that was inserted between the vertebrae to maintain the space between the vertebral bodies and the joint's mobility. Dr. Fernström implanted his device, commonly referred to as the "Fernström Ball," in more than 100 patients. His clinical results were first published in 1964. Today, research continues on a variety of different spinal disc prostheses for both the lumbar and cervical spine. Studies also are underway to evaluate other aspects of artificial disc replacement, including which types of patients are most likely to benefit from surgery, new surgical implant techniques and improved disc materials. Talk to your doctor to learn more about spinal artificial discs. To find a spine surgeon in your area, use our Physician Locator. |