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Artificial Disc Replacement Surgery

Is It as Effective as Spinal Fusion?

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Artificial disc replacement is emerging as an alternative to spinal fusion for the surgical treatment of severe disc problems. Lumbar artificial disc replacement still has some hurdles to overcome before it is fully accepted into the medical community. However, cervical disc replacement has made great strides since the first cervical disc was approved by the United States Food and Drug Administration (FDA) in 2007.

Artificial Disc Replacement: A Treatment for Degenerative Disc Disease
Artificial disc replacement surgery is indicated for patients with severe degenerative disc disease (DDD).

Degenerative disc disease is a condition that can occur in the neck or low back and cause significant pain. As we age, the discs typically dehydrate and become more brittle. As the discs degenerate, they flatten out and can develop cracks in the outer layer, known as the annulus fibrosus.

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Degenerative discs can cause pain in patients for several reasons:

  • The annulus can come in contact with nerve fibers or pain receptors, called nociceptors.
  • The nerve fibers can grow into the cracks of these discs and cause pain.
  • Portions of the nucleus, or core of the disc, can bulge out and push on these fibers.
  • There are proteins in the nucleus that are chemically irritating to the nerves and can cause pain.

For some patients, removal of the offending disc alone is not enough. Spinal fusion, which immobilizes the painful disc, has long been the standard of care in patients who don't respond to non-surgical treatments. The theoretical benefits of disc replacement are to preserve motion and reduce abnormal stresses at the disc above and below the surgery.

Lumbar Artificial Disc Replacement
What makes artificial disc surgery so challenging is that unlike a ball and socket joint, such as the hip, the disc is a complex joint with motion in several planes. It is difficult to emulate the natural motion of the disc while maintaining stability.

In 2004, the FDA approved the first lumbar disc replacement.1 Use of the device skyrocketed as the implant gained popularity, fed by surgeon interest, patient demand, and optimism over this new treatment modality.

Unfortunately, much of the research showed few benefits over spinal fusion. Disc replacement leaves you with a mobile device that may wear out during your lifespan. In many patients, the indications were over-extended (that is, this treatment was given to patients who may not have been ideal candidates), and the device had to be removed or fused from behind.

Several patients didn't experience as good of outcomes as were expected.2 This led to insurances companies in the US declining coverage and the reduced use of lumbar disc replacement.

Cervical Artificial Disc Replacement
Cervical disc replacement, however, has become much more popular. This is in part to better patient selection, lower forces in the neck, and safer revision strategies.

The January 2009 issue of Spine contained a report from researchers at Washington University in St. Louis. A group of spine surgeons conducted a study to determine how artificial disc replacement compared to spinal fusion in patients with cervical degenerative disc disease. The spine surgeons reported that most patients who received an artificial disc had a speedier recovery than those who underwent a spinal fusion. The surgeons concluded that the patients who had artificial disc replacement surgery recovered just as well—or better—than those who had a spinal fusion.3

The first artificial cervical disc was approved in 2007.4 While cervical disc replacement still suffers from some of the stigma of lumbar disc replacement, it has been better received in the spine community as a whole.

To view images of cervical and lumbar artificial discs, visit our other article about artificial disc replacement surgery.

If you suffer from severe disc problems, talk to your doctor about whether you are a candidate for surgery. If you are, spinal fusion might not be your only option—artificial disc replacement may also successfully treat your back or neck pain.

Updated on: 03/16/10
Praveen V. Mummaneni, MD

Comparing Cervical Fusion with Artificial Disc Replacement
Article review written with Jau-Ching Wu, MD
Anterior cervical discectomy and fusion (ACDF) has become a mainstay in the treatment of degenerative cervical disc diseases, including arm pain and weakness. In recent years, the emerging technology of artificial disc replacement in the cervical spine has shown an advantage over ACDF-segmental motion preservation. Studies demonstrated that a patient with single level ACDF loses 7º of segmental flexion and extension and 6º of lateral rotation, whereas a patient with a cervical arthroplasty is able to maintain this motion.1 Therefore, the issue has become in whom, how, and when an artificial disc in the neck could lead to a better outcome.

In the current literature, there are 3 prospective randomized multi-center clinical studies comparing cervical artificial disc to ACDF in patients treated for single-level cervical degenerative disc disease (DDD). The largest of these studies (reported by Mummaneni et al) compared the PRESTIGE ST Cervical Disc with ACDF in a total of 541 patients.1 Secondly, Heller et al compared the BRYAN Cervical Disc with ACDF in 463 patients.2 Thirdly, Murrey et al compared single-level ProDisc-C arthroplasty with ACDF in 209 patients.3 From the above 3 relatively large scale clinical trials with a follow up duration of 2 years, we can summarize that cervical artificial disc replacement is a safe and effective alternative in treating single-level cervical disc disease in appropriately selected patients.

The current indication for cervical arthroplasty in the United States includes symptomatic one-level cervical disc disease in patients who have failed non-surgical management. Those who are not ideal candidates include patients with: 1) cervical kyphosis (abnormal neck curvature), 2) cervical spondylosis with incompetent or significantly degenerated facet [joints], 3) cervical ankylosis/autofusion (too much bone spur resulting in autofusion), 4) osteoporosis (poor bone quality), and 5) cervical trauma with ligamentous or facet injury. The classical candidate for a one level cervical arthroplasty is a 20 to 55-year-old patient with single-level cervical disc disease who has normal facet joints.

It is obvious from the data we have to date that cervical artificial disc replacement will not and cannot entirely replace ACDF. Fusion is still necessary in many degenerative diseases. Last but not least, cervical arthroplasty is unique and should not be compared to either lumbar arthroplasty or large joint (hip or knee) arthroplasty. The cervical spine is exposed to much lower loading weights than are the lumbar spine and the large joints. Longer term investigation is currently underway to further evaluate the benefits of cervical artificial disc replacement.

As Dr. Highsmith points out in his article, lumbar arthroplasty has met with more mixed results. Some centers have reported excellent outcomes and some have reported significant complications and implant migrations. It is likely that patient selection and surgeon experience plays a very important role in the success of lumbar arthroplasty.

References

  1. Mummaneni PV, Burkus JK, Haid RW, Traynelis VC, Zdeblick TA. Clinical and radiographic analysis of cervical disc arthroplasty compared with allograft fusion: a randomized controlled clinical trial. J Neurosurg Spine2007 Mar;6(3):198-209.
  2. Heller JG, Sasso RC, Papadopoulos SM, Anderson PA, Fessler RG, Hacker RJ, et al. Comparison of BRYAN cervical disc arthroplasty with anterior cervical decompression and fusion: clinical and radiographic results of a randomized, controlled, clinical trial. Spine (Phila Pa 1976)2009 Jan 15;34(2):101-7.
  3. Murrey D, Janssen M, Delamarter R, Goldstein J, Zigler J, Tay B, et al. Results of the prospective, randomized, controlled multicenter Food and Drug Administration investigational device exemption study of the ProDisc-C total disc replacement versus anterior discectomy and fusion for the treatment of 1-level symptomatic cervical disc disease. Spine J2009 Apr;9(4):275-86.
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