Early Results with New Disc Replacement for the Cervical SpineTwenty-five patients treated with the new Discover disc replacement for the cervical spine (neck) provide some early results from this study. The implant (manufactured by DePuy) is made of titanium with a polyethylene (plastic) insert to mimic the natural disc. It is designed to restore full motion and even incorporates the lordotic angle (curvature) of the natural spine.
The patients could have had the more traditional procedure called anterior cervical discectomy and fusion (ACDF). With ACDF, the surgeon removes the degenerative disc and fuses the two vertebral bones on either side of the disc together. Patients in this study were offered either the ACDF or disc replacement (called cervical arthroplasty).
They chose the arthroplasty. After the disc was removed, the ends of the vertebral bodies (called endplates) were smoothed down. The Discover implant was inserted into the empty disc space and positioned properly using fluoroscopy (special three-dimensional, real-time X-ray).
The surgeon was careful to choose the correct size of implant for each patient and to maintain the proper disc height. Special "teeth" built in to the implant help hold it in place until bone fills in around it. There is no need for a bone graft.
Each patient had a disc herniation with pressure on the spinal cord or spinal nerve roots. Conservative (nonoperative) care was unsuccessful in changing their symptoms. They went into the surgery knowing that if disc replacement was not possible, the surgeon would do a fusion procedure instead.
Results were assessed 12 to 18 months later using a variety of different measures. For example, before and after X-rays were compared. Pain levels, neck range-of-motion, and function were evaluated. Special tests used included the Neck Disability Index, the Japanese Orthopedic Association (JOA) scale, and Odom's Scale.
Pain relief was good-to-excellent. Motion was improved and both measures (pain relief and motion) stayed improved throughout the follow-up period. The implants remained in good position with no evidence of subsidence (sinking down into the bone).
Careful preparation of the endplates helps ensure good spinal alignment. Good contact between the implant "teeth" and the vertebral bone holds the implant in place. This placement is important to keep it from sliding too far back where it could put pressure on the spinal cord.
There were no major complications such as death. Adjacent degenerative disease (break down at the level above or below the implant) was not observed. This was the first study published with results from the new Discover artificial disc replacement device. The study was small and reported early results but the outcomes were encouraging.
The editors of the journal in which this article was published made a few concluding comments. They point out that this was a small study with many limitations. More studies of higher quality are needed before the Discover implant can be deemed safe and effective. Studies comparing results between the Discover arthroplasty and the anterior cervical discectomy and fusion (ACDF) procedure will be important as well.
Junjie Du, MD, PhD, et al. Early Follow-up Outcomes After Treatment of Degenerative Disc Disease with the Discover Cervical Disc Prosthesis. In The Spine Journal. April 2011. Vol. 11. No. 4. Pp. 281-289.
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