Cervical disc replacement after prior fusion comparable to primary replacement

The reoperation rate with a prior adjacent fusion was higher than that seen in primary procedure patients.

Early results from the first U.S. investigational device exemption trial investigating cervical total disc replacement adjacent to a prior anterior cervical discectomy and fusion show clinical outcomes similar to primary disc replacement.

Frank M. Phillips, MD, and colleagues compared the results of 123 patients who underwent primary cervical disc replacement with a porous-coated motion disc (PCM, Cervitech Inc.) to a cohort of 23 patients who underwent cervical disc replacement with the same device adjacent to a prior single-level fusion.

The investigators discovered that both groups showed statistically significant improvements from baseline to 6-week follow-up regarding Neck Disability Index (NDI), neck Visual Analog Scale (VAS) and arm VAS scores and these improvements were maintained throughout the 1-year follow-up. However, the investigators found no significant differences between the groups for these outcomes.

"Excellent" clinical outcome

"The PCM disc replacement adjacent to a prior cervical discectomy and fusion was associated with an excellent clinical outcome, with improvement in clinical symptoms and neck disability," Phillips said during his presentation at Spine Week 2008. "The extent of improvement is comparable to those seen in patients undergoing PCM disc replacement as a primary procedure."

Each group had two revisions, leading to a 1.6% complication rate for the primary group vs. 7.7% for the adjacent-to-fusion group. An X-ray evaluation also revealed that the adjacent-to-fusion group showed hypermobility preoperatively and postoperatively.

"This study would support the biomechanical data that it is a more challenging environment with increasing mobility at levels adjacent to a fusion," Phillips said. "We saw an acceptable complication [profile], although our data suggest that with the adjacent-to-fusion approach, you may have a high complication rate in terms of the reoperation [rate] that was seen for a primary PCM disc replacement."

The investigators studied data from five sites participating in a larger FDA trial. The study included patients with a primary diagnosis of radiculopathy or myelopathy and allowed those with a prior single-level fusion. The groups of patients that Phillips and his colleagues studied were similar in age, gender, weight and height.

Patients in the adjacent-to-fusion group had a mean time of 7.1 years from their prior fusion to the investigated procedure. Most patients in the primary group had surgery at the C5-C6 level, while most of the adjacent-to-fusion patients were treated at the C6-C7 level. Twelve patients in the adjacent-level group had the PCM device placed above the prior fusion level and 13 had it placed below the level.

Motion maintained

The investigators found no significant differences between the study groups regarding operative time or blood loss. Baseline measures showed that 85% of primary patients did not have dysphagia but 45% had mild or moderate dysphagia at 6 weeks postop. However, the rate of dysphagia returned to baseline levels at 1 year. The investigators found similar findings in the adjacent-to-fusion group and found no difference in dysphagia at any time point between the groups.

Four patients in the study were revised to a single-level fusion. One patient in the primary group underwent revision for ongoing neurologic symptoms and one patient in the adjacent group was revised for device migration. Each group had one patient revised for ongoing neck pain.

The primary group showed 8° of motion on preop X-rays and 5° at postop, while the study group showed 9° preoperatively and 10° postoperatively.

"Motion was maintained in both groups, but this would support the biomechanical data with the adjacent-level groups having a higher range of motion both before they get the PCM and after they get the disc replacement."

For more information:
Frank M. Phillips, MD, can be reached at Rush University Medical Center, Midwest Orthopaedics, 1725 W. Harrison St., Suite 1063, Chicago IL 60612; +1-312-432-2339; e-mail: frank.phillips@rushortho.com. He receives research support for staff and materials from Cervitech Inc.

Reference:
Phillips FM, Regan JJ, Cappuccino A, et al. Cervical disc replacement in patients with and without previous adjacent level ACDF surgery. Paper C1. Presented at Spine Week 2008. May 26-31, 2008. Geneva.