In a total disc replacement surgery the interior, exterior, and endplates of a disc are all replaced with a single surgical implant.
Success with total disc replacement depends heavily on patient selection.1 Artificial disc replacement is recommended for degenerative disc disease that has been confirmed through a rigorous diagnostic process, including identification on an imaging scan.
Lumbar artificial disc replacement is only advised if nonsurgical treatments are ineffective after at least 6 months. This procedure is typically not recommended if a patient also has significant spondylolisthesis (slipping of one vertebra on another) or bony lumbar spinal stenosis (narrowing of the spinal canal).
Total Disc Replacement Procedure
Most total disc replacement surgeries are performed in the following steps:
- Lying on the back under general anesthesia, the spine is accessed through a small incision in the abdomen (usually 5 to 8 centimeters long). Muscles, organs, and/or blood vessels may be moved to the side to access the spine. Muscles are typically not cut in this surgical approach.
- The natural disc is removed from the disc space, including part of the cartilaginous endplates, annulus, and nucleus (a discectomy).
- A series of devices are used to measure and assess the size of the vertebral bodies and the curvature of the spine at the segment. Measurements are taken to ensure the device is properly sized and fitted.
- If disc height has been lost, it is raised to its original height using wedged instruments.
- For some devices, tracks or cuts are made into the surface of each vertebral body facing the disc space. These tracks allow the device to be fixed to the vertebral body during surgery.
- Once the disc space has been cleared and prepared, the artificial disc is implanted. Real time fluoroscopy (a live x-ray) is used during the procedure to ensure proper placement of the device.
- Tissues and blood vessels are allowed to return to their normal positions, and the wound is closed in several layers using sutures.
Artificial discs are designed to attach to the vertebrae and fit in the disc space, and each type of disc requires specific procedural steps and unique set of tools for implantation. For this reason, spinal surgeons undergo specific training for each different implant.
Total Disc Replacement Devices
There are currently two artificial disc models available on the U.S. market which differ slightly in makeup and design. A typical artificial disc device includes:
- Two endplates that attach to the vertebral bodies. Artificial disc endplates are made of a dense metal alloy. These endplates include teeth or keels on the endplates that attach to the vertebral bodies. Metal endplates may be coated with a porous layer of a different metal that encourages bone from the vertebral body to grow onto the endplate, providing extra stability.
- A central joint allowing for movement at the spinal segment. The center of an artificial disc is typically made of surgical-grade plastic (ultra-high molecular weight polyethylene) that articulates with the endplates and allows for bending and twisting at the spinal segment. Many models consist of a ball-and-socket joint, in which a rounded piece on one endplate fits into a concave portion on the other endplate. Other models currently in development include an artificial disc nucleus that attempts to provide more natural cushioning and motion.
Devices differ in where they can be implanted. For example, some devices may only be approved for implantation at the L4-L5 or L5-S1 segments, and other lumbar disc implant designs can be implanted anywhere between L3 and S1. Current lumbar devices are approved for use by the FDA only at a single spinal segment.