Artificial Disc Surgery: Cervical Spine
Replacement Instead of Fusion: Part 2
Cervical Disc Replacement Instead of Cervical Fusion
There is a new technique that is becoming more available worldwide. This technique involves removing the disc and then replacing it with an artificial disc. This has two main benefits:
1) Motion is maintained and the patient will not feel their range of motion is restricted.
2) Theoretically, adjacent segment disease will not occur.
Consequently, patients undergoing decompression and placement of an artificial cervical disc do not need a brace after surgery and may require less surgery on their neck in the future.
Spinal Disc Replacement: Not New
The idea of spinal disc replacement is not new. It was first attempted 40 years ago. At that time, stainless steel balls were implanted into the disc spaces of more than 100 patients. These pioneering efforts were followed by more than a decade of research on the degenerative processes of the spine, spinal biomechanics and biomaterials before serious efforts to produce an artificial disc resumed. The Bryan® cervical disc prosthesis represents a state-of-the-art disc prosthesis, although several types are now available.
Bryan® Cervical Disc System
The Bryan® Cervical Disc System is a composite-type artificial disc designed with a low friction, wear resistant, elastic nucleus with two anatomically shaped metal plates. A flexible membrane forms a sealed space and contains a lubricant to reduce friction and wear and tear. The implant allows for normal range of motion and comes in five sizes.
Figure 4 and 5: X-rays of the cervical spine after implantation of an artificial disc. Normal movement is preserved.
The initial clinical experience with the Bryan® Cervical Disc Prosthesis has been promising.
Figure 6: The Bryan® artificial disc prosthesis.
Figure 7: A skeletal model of the cervical spine showing how the artificial disc is placed.
So far the Bryan® cervical disc is available in Australia, Europe and South Africa. It is currently part of a randomized 12-center Food and Drug Administration (FDA) trial throughout the United States and should be available outside the trial in the United States in a few years.
Problems with the Bryan® Disc
The main issue with artificial discs is we do not know how long they will last. Knee and hip replacements wear out in 10-15 years, so it is probably naïve to think this artificial joint will last a lifetime. To date however, the Bryan® disc has been tested under laboratory conditions to a total of 45 human equivalent years of neck movement with only little wear noted. The ultimate effects on the adjacent levels will not be known for possibly decades.