Artificial Disc Replacement for the neck area, referred to as the cervical spine, has been used successfully in the United States for over 15 years, beginning with the Charité® cervical disc released in 2004. More recently, artificial discs have become available for treating disc problems in the lower back, called the lumbar spine.

While the anatomy of the cervical (neck) and lumbar (low back) vertebrae and discs may be similar, the stresses experienced by the two spinal areas are vastly different. The cervical spine only supports the weight of the head. Conversely, the lumbar spine must support the weight of the head, arms and complete torso. This creates challenges when designing an artificial disc that can sustain the forces imposed on it during everyday activities and more strenuous activities like sports or exercising.

Prodisc® L Disc Replacement

Perhaps the most popular and widely studied artificial disc technologies available for the lower back is the Prodisc® L Total Disc Replacement by Centinel Spine. The Prodisc® L Artificial Disc is an alternative to spinal fusion in the lumbar spine and aims to replicate the motion of the natural spine, allowing for bending and rotating on all axes.

In traditional spinal fusion surgery the damaged disc is typically replaced with bone from a patient’s hip or from a bone bank. This bone graft then fuses to the surrounding vertebrae due to the body’s natural healing process. Fusion surgery causes the two vertebrae to become locked in place, putting additional stress on discs above and below the fusion site, which restricts movement and can lead to further disc herniation with the discs above and below the fused disc. An artificial disc replacement is intended to duplicate the function level of a normal, healthy disc and retain motion in the spine.

With the Prodisc® L, this motion preservation is achieved through the use of an artificial ball-and-socket implant. As can be seen in the above image, the artificial disc is composed of two endplates and a plastic rounded insert. The two endplates have fins that embed into the surrounding vertebrae, keeping the disc in place. The plastic insert clips into the bottom plate, completing the ball-and-socket mechanism that allows for a range of rotational and bending motion.

This is an exciting time for spine surgery as new disc technology is emerging over the next 10 years that will improve on how the lumbar disc more closely replicates the function of a normal healthy disc. Today’s versions attempt to replicate the rotational function, but they don’t provide the up and down shock absorption that a normal healthy disc provides. That is the future challenge of artificial disc design.

CONTRIBUTING AUTHOR

S. Craig Humphreys, M.D.
Fellowship-trained spine surgeon
Board Certified Orthopedic Surgeon

Dr. Humphreys is also the co-inventor of a new artificial disc for the low back called “Balanced Back”. This new artificial disc for the lumbar spine is significant in that it enables spine surgeons to replace a herniated disc from the back of the spine rather than going through the abdomen, which can be a more complex surgery working around internal organs.