Bryan cervical arthroplasty helps halt mid-term adjacent-level degeneration

At four years postcervical TDR, 82% of patients showed preserved motion of the artifical disc.

The best advantage of one cervical disc replacement device over fusion may be the ability to keep adjacent-level disc degeneration at bay at mid-term follow-up, according to Belgian investigators.

The findings are based on 4- to 6-year clinical and radiographic results of a study conducted on the Bryan cervical disc prosthesis (Medtronic Sofamor Danek), which was used to treat patients with cervical degenerative disc disease either at one or two levels. Seventy-four single-level patients reached the 4-year postoperative follow-up.

The Bryan cervical disc is not approved by the FDA for use in the United States; it is currently being used under an investigational device exemption in a 12-center FDA trial. It received the European CE mark in 2000.

In addition to possible preservation of adjacent levels with cervical total disc replacement (TDR), investigators noted the technique preserved motion of the functional spine unit in 82% of the cases, a continuation of a trend they saw at 2 years postop, according to Jan Goffin, MD, PhD.

Goffin presented the latest results at the North American Spine Society annual meeting in Seattle, but due to time constraints only reported on the one-level surgeries.

"We had at 4 years preserved motion in 82.4% of the cases," Goffin said.

Of the 20 patients with 6-year follow-up, motion was preserved in 17 (85%). None of those patients lost motion of the artificial disc between their 4- and 6-year follow-up examinations, he said.

The study included cervical TDR patients from Leuven who underwent surgery with the Bryan implant, which consists of two porous-coated titanium alloy shells and a contained synthetic nucleus. Some were previously enrolled in a multicenter prospective European clinical trial with the Bryan disc. Others were not included in the multicenter trial but consecutively treated with the Bryan disc in Leuven through December 2002.

Using Odom's criteria as a measure of clinical success, 66 of 74 patients had outcomes that were good or excellent at 4 years postop.

Also at 4 years postop, investigators observed paravertebral ossification at the operated level on plain radiographs of 18 patients, which ended up being problematic for seven of them. In those cases, the ossification led to loss of motion at the operated level. Goffin said that the patients in his series did not take NSAIDs, which may have prevented this kind of ossification. Three of the four patients who had ossification at 6-year follow-up maintained good flexion/extension. "The issue of ossification still needs more investigation," he said.

The TDR procedure appeared to have protected 53.5% of patients who already had adjacent level degeneration at baseline (20/43) from further degenerative problems at those same levels at the 4-year follow-up. For patients who had no degeneration at the adjacent levels at the time of surgery, only 6.4% had degeneration at those levels at 4-year follow-up (2/31), Goffin said.

In the wake of fairly good results with lumbar total disc replacement (TDR), U.S. clinicians have grown more interested in cervical TDR as an alternative to fusion, where appropriate.

For more information:
Goffin J, Van Loon J, Van Calenbergh F. Cervical arthroplasty with the Bryan disc: 4-year results. #124. Presented at the North American Spine Society 21st Annual Meeting. Sept. 26-30, 2006. Seattle.
Jan Goffin, MD, PhD, is head of the Department of Neurosurgery at University Hospitals KU- Leuven, Belgium. He can be reached at +32-16-344609, fax: +32-16-344285.The authors of this study reported they received grant/research support from Medtronic Sofamor Danek.