There are a number of important factors in considering cervical disc replacement versus a traditional anterior cervical discectomy and fusion (ACDF) surgery. A patient may be most suitable for either cervical disc replacement or ACDF as a result of his or her symptoms or amount of disc degeneration. The options for each individual patient are best discussed with the treating physician.

It is important to remember that a disc replacement is a motion-preservation procedure and not a motion-creation procedure. This means that a discectomy does not increase range of motion. Following discectomy, even though an artificial disc has been inserted, an ankylosed or severely spondylotic disc that did not move before disc replacement is not likely to move after disc replacement.

The natural cervical intervertebral disc is an amazing mechanical structure from an engineering perspective. It has the ability to absorb a large compressive load while still providing an impressive range of motion between the bones in the neck.

Duplicating the natural disc’s form and function with a synthetic—or artificial—disc is challenging. However, several artificial cervical discs have been developed and are available as a surgical option for patients with symptomatic cervical disc problems.

What Is an Artificial Cervical Disc?

An artificial cervical disc is a device inserted between two vertebrae in the neck to replace a damaged disc.

The intent of the artificial disc is to preserve motion at the disc space. It is an alternative to the commonly performed anterior cervical discectomy and fusion (ACDF), a surgical procedure that is designed to address the pathology by eliminating motion at the diseased disc level.

Artificial disc replacement (ADR) surgery—also known as a total disc arthroplasty or total disc replacement (TDR)—is typically performed for a patient with a cervical disc herniation that is causing significant neck pain and/or arm pain that has not responded to nonsurgical treatment options and is significantly affecting the individual’s quality of life and ability to function.

The theoretical advantages of the artificial cervical disc compared with a fusion include:

• Maintaining normal neck motion
• Reducing degeneration of adjacent segments of the cervical spine
• Eliminating potential complications and issues associated with the need for a bone graftand the hardware used in ACDF surgery
• Allowing early postoperative neck motion

As with all surgeries, there are also unique potential risks and complications associated with cervical artificial disc replacement.

On October 26, 2004 the U.S. Food and Drug Administration (FDA) approved the Charité™ artificial disc for use in the US. This device treats severe, chronic low back pain by replacing the damaged or worn out spinal disc in the lower back with an artificial disc. The device is made by DePuy Spine, a division of Johnson and Johnson, Inc. The Charité artificial disc is also currently used in disc replacement surgery in more than 30 countries throughout Europe, Asia, North America, Africa and Latin America.

The Charité artificial disc is a sophisticated implant made of two metallic endplates and a plastic center that is designed to help align the spine and maintain the spine’s natural flexibility. This means that the artificial disc mimics the role of a natural spinal disc – both in maintaining the normal position of the spine and allowing the spine to bend and twist.

The artificial disc has been created as an alternative to the current surgical treatment for treating chronic low back pain from degenerative disc disease – lumbar spinal fusion surgery. In spine fusion, the surgery is designed to stop motion at the painful level of the spine. Usually, implants are used to help provide initial fixation, such as metal screws and rods and/or cages that are inserted between the vertebrae. Because the fusion eliminates the motion in the lumbar spinal segment, the pain caused by the motion is reduced or eliminated. When done correctly for the right indications, a fusion has a high success rate in reducing or eliminating the patient’s pain. However, because it limits range of motion it may transfer extra stress to discs above and below the fusion site. Because the artificial disc allows continued motion in the spinal segment, it is theorized that this may be a preferable alternative to spinal fusion surgery for patients with the right indications.

The Charité disc has been approved for use in patients who have severe lower back pain caused by degenerative disc disease and have obtained little or no pain relief after at least six months of non-surgical treatments, such as pain medications, physical therapy, injections, and/or manipulation. The FDA clearance for disc replacement is for one level of the lower spine, and it must be done at one of the two lowest levels of the spine (L4-L5 or L5-S1).

Charité Artificial Disc Study Results

The objective of the US FDA clinical trial on the Charité artificial disc was to determine whether the Charité artificial disc was any less safe and effective than the currently available spinal fusion surgery with a cage and bone graft, called an anterior lumbar interbody fusion.

The study involved a total of 375 patients enrolled in 15 spine centers located across the U.S. The initial five patients treated with an artificial disc at most centers (71 patients) were considered training cases and were not included in the results of the study. During the randomized study, 205 patients received the Charité lumbar artificial disc and 99 patients received the control surgery (anterior lumbar interbody fusion). Both operations require a similar incision in the belly. Patients were not told which type of surgery they were going to have – the fusion surgery or the artificial disc – before the surgery.

After two years of follow-up on the 304 patients in the randomized study, patients who received the Charité artificial disc did no worse than patients treated with anterior lumbar interbody fusion. The rates of adverse events from use of the artificial disc were similar to those from treatment with fusion. Based on these results, the FDA approved the Charité for commercial use in the U.S.

At the annual meeting of The Spine Arthroplasty Society, the Texas Back Institute, the principal spine center investigating the device, presented an overview of the study results. Several measures were used to determine outcomes of the study, including a 0 to 10 scale to assess pain intensity, a report by patients about their daily activities (using the Oswestry Low Back Pain Disability Questionnaire). In both the artificial disc replacement and the fusion patient groups, it was found that both the patients’ pain and functional scores improved significantly after surgery.