The spine is made up of bones called vertebrae, with cushioning pads between them known as vertebral discs. Sometimes a disc becomes damaged through injury or wear, and this can cause pain. In order to relieve severe pain, and allow the person to maintain a useful range of motion in the backbone, an artificial disc replacement is sometimes used to perform the function of the original, natural disc. Artificial discs are currently available which can be used in place of cervical discs in the neck and lumbar discs in the lower back.
Older treatments involve fusing the spine around the region of the damaged disc, but this has the disadvantage that it reduces the flexibility of the backbone, which sometimes places stress on formerly healthy discs and vertebrae nearby. The newer method of artificial disc replacement allows a greater degree of back movement to be retained. Additionally, patients often experience less pain following the operation, and recover more quickly.
The procedure for artificial disc replacement is carried out under a general anesthetic, and the first step is to remove the diseased disc before installing the replacement. For a total disc replacement in the lower back, a type of disc prosthesis may be used which consists of two metal plates surrounding a mobile core made of plastic. Spikes protruding from the metal pieces fix them into the bone, which eventually grows and fuses with the plates. The plastic core allows gliding movements to occur. A different type of spine arthroplasty device, where two metal pieces articulate by way of a ball and trough, is sometimes used to replace a cervical disc in the neck.
An alternative to a total disc replacement is what is known as a disc nucleus replacement, which may be carried out if the outer part of the disc is still quite healthy. In this procedure, only the center, or nucleus, of the original disc is removed. It is replaced by a type of plastic which absorbs water and swells to fill the nucleus cavity. As the material is soft and can be compressed, it allows the disc to continue to function in a relatively natural manner.
It may take up to eight weeks for people to return to normal everyday activities after an artificial disc replacement has been carried out, although it could be longer before more vigorous exercises, such as sports, can be pursued. Possible complications include the artificial disc replacement becoming damaged or dislodged. For this reason, following surgery, patients have regular checkups for life to make sure the prosthesis is functioning normally.