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Complications of Cervical Disc Arthroplasty

Total cervical disc arthroplasty (artificial cervical disc insertion) is becoming increasingly popular for the treatment of cervical disc disease and arthritis. Theoretically, by preserving motion at the diseased level as opposed to cervical fusion, total disc arthroplasty will eventually provide a decrease in the number of patients undergoing additional surgery due to breakdown of the adjacent disc segments (those immediately above or below the artificial disc). Time will tell if these assumptions prove to be true, but our experience with the Mobi-C artificial cervical disc has been very positive to date (see the article entitled “Artificial Cervical Disk Surgery (Cervical Disc Arthroplasty”) for further explanation of the theoretical advantages as well as the indications and contraindications).

Artificial cervical discs previously and currently on the market have various names depending on the manufacturer, including but not limited to Mobi-C, Prestige ST, Bryan Cervical Disc, and ProDisc C. Each device is designed to preserve motion but works in a slightly different way. All are inserted via a standard anterior approach through a small incision in the anterior neck. All of these devices in general present similar risks and benefits.

Little information exists in the medical literature regarding the risks of artificial cervical disk arthroplasty due to the fact it is a relatively new procedure with limited overall experience. In addition to usual complications associated with anterior neck surgery (bleeding, infection, hematoma, swallowing difficulties, hoarseness of the voice, spinal cord or nerve root injury, etc.) complications associated with artificial cervical disk surgery include:

  1. Adjacent segment degeneration
  2. Migration of the device
  3. Heterotopic calcification
  4. Fracture of the involved vertebral segments
  5. Hypersensitivity reaction to the components of the device.

Adjacent Segment Degeneration

Adjacent segment disease is defined as a breakdown of the segments above or below the operated segment. Although several studies point to cervical disc arthroplasty (as opposed to fusion) as providing a greater chance of maintaining post-op mobility, it remains uncertain as to whether adjacent segment degeneration occurring after either procedure is the result of the natural history of cervical arthritis, altered biomechanics resulting from the surgery, or a combination of the two. Initially, it seems that the cervical range of motion decreases immediately after cervical disc arthroplasty but returns to normal within 24 months if the device functions as expected. A recent study points to a decrease in the incidence of adjacent segment disease with a two-level Mobi-C cervical disc arthroplasty. More studies are required to definitely determine whether the natural history of cervical arthritis or local changes as a result of the surgery itself are primary causes of adjacent segment disease after anterior cervical spine surgery.

Migration of the Device

Although rare, migration of the artificial disc posteriorly into the spinal canal is a serious complication, resulting in spinal cord compression and possible spinal cord injury. In addition, the device can migrate up or down into the adjacent endplates of the vertebral bodies, especially if the implant is not inserted properly or if the patient suffers from the softening of the bone as in osteoporosis. Proper surgical techniques, appropriate patient selection, and use of the correct size of the implant all lead to minimizing these complications.

Heterotopic Calcification

Heterotopic calcification refers to the unintended calcification of the artificial disc in the weeks or months after the surgery, leading to loss of movement and eventual fusion across the cervical segment. This has been reported in up to 18% of cervical disc arthroplasty patients and seems to be most common in men, elderly patients, and those patients with extensive dissection and drilling of bone during insertion of the implant. Some surgeons, including us, use medications like nonsteroidal anti-inflammatory agents (like ibuprofen) in the post-op period to minimize this complication. Avoiding extensive muscle dissection, preserving the endplates of the vertebral bodies, and minimizing drilling of bone seems to help prevent heterotopic calcification as well.

Fracture of the Involved Vertebral Segments

This complication seems to be more common in with artificial disc devices that have a structural keel down the middle of the device, designed to improve stabilization of the implant within the disc space immediately after insertion. This complication also appears to more common in patients with osteoporosis or other causes of poor bone quality or in those with extensive drilling of the vertebral endplates.

Hypersensitivity Reaction to the Components of the Device

Inflammation due to hypersensitivity to the metal components has been described in a number of metallic implants, including hips, knees, and artificial cervical and lumbar discs. Chronic inflammation at the site of the device can lead to exuberant scar tissue, resulting in nerve root and spinal cord compression with recurrence of symptoms, even if no free metal fragments occur from the breakdown of the device. Breakdown of the ultrahigh molecular-weight polyethylene core could conceivably result in particulate accumulation and chronic inflammation and progressive symptoms. Therefore, a previous allergic response to any of the components of an artificial disc device is a contraindication to disc insertion.

As artificial cervical disc insertion is a relatively new procedure, their use is continuously undergoing revision as we learn more. Complications can be minimized by appropriate patient selection; meticulous surgical technique; use of agents to minimize heterotopic ossification; and appropriate therapy after surgery to maximize outcome and preserve as much motion as possible.

If you wish to learn more or you feel you may be a candidate for insertion of an artificial cervical disc, please contact us directly at 1-888-854-9274