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Cervical disc replacement shows greater function, mobility than fusion
At one year postop TDR improved flexion/extension while fusion restricted motion.
The motion-sparing advantages offered by a semiconstrained total disc prosthesis make it a promising alternative to discectomy and fusion for treating cervical spondylosis and degenerative disc disease based on results presented at the North American Spine Society annual meeting.
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Investigators from centers in California and Colorado, two of 12 centers involved in an FDA investigational device exemption (IDE) trial for the Prodisc-C [Synthes Spine] total disc replacement (TDR) device, presented evidence the implant is safe and effective at short-term follow-up.
The prospective randomized trial compared results in patients who underwent cervical TDR to those who had anterior cervical discectomy and fusion (ACDF).
“When we looked at the Visual Analog Scale (VAS), neck disability index (NDI), SF-36 and neurological function, there wasn’t any difference at 18 months. The NDI in the Prodisc-C (group) demonstrated some significant improvement at 1 and 2 years and there have been no implant-related complications,” Michael E. Janssen, DO, said.
127 patients studied
Janssen, of Spine Education and Research Institute in Denver, presented results of 87 patients enrolled in the IDE trial at his center and those Daniel Murrey, MD, of Charlotte Orthopedic Specialists, Charlotte, N.C., treated.
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A post-surgery analysis conducted at another center revealed relatively normal range of motion in patients undergoing TDR, according to Ben B. Pradhan, MD, of The Spine Institute at St. John’s Health Center, Santa Monica, Calif., who presented results in 40 patients with cervical degenerative disc disease enrolled in the same trial and treated at his institution.
In Pradhan’s investigation, 24 patients were randomized to the cervical TDR group and 16 to the ACDF group. Investigators used VAS, NDI, SF-36 and other scores preoperatively and to assess postop outcomes at 6 weeks, 3, 6, 12 and 18 months.
Some 24- and 36-month follow-up data were available for patients at both centers.
Demographics for patients at all the centers were similar, the investigators said.
Treating spondylosis
Janssen and colleagues treated patients with cervical spondylosis; 48 men and 28 women were enrolled in the total disc replacement arm of the study and 26 men and 38 women were randomized to ACDF surgery. He reported on 44 patients who underwent cervical TDR to implant the Prodisc-C implant via a standard approach (42.7 years old, average) vs. 45 patients who had ACDF surgery with allograft and plating (44.6 years old, average).
Level C5-6 was the one most commonly treated in both arms of the study, Janssen said.
In comparing their results, at 18 months postop, investigators detected similar improvements in both groups for motor and neurologic function, arm and neck pain based on the VAS score, NDI and SF-36 mental scores. However, those in the Prodisc-C group exhibited more function based on SF-36 physical scores compared to the fusion group (P=.004).
Differences noted
“There were data points at 3 months and 12 months which suggest an improvement of the motion preserving technology compared to that of fusion,” Janssen said.
At 6, 12 and 24 months, more patients who had TDR surgery were satisfied with the procedure than patients in the control group.
“It appears, at least in the early evaluation of the largest subset of North American patients, that this implant for this particular disease is safe and effective,” Janssen said. Confirmation of any trends toward greater outcome differences cannot be made until longer-term data are received, he said.
Motion preservation
Pradhan reported results on patients with up to 3 years postop follow-up. “Patient satisfaction was high in both groups at 70% to 85%,” he said.
Patients who underwent TDR could maintain fairly normal neck range of motion. For example, preoperatively patients in the fusion group had 9° of flexion/extension that deteriorated to 1° or basically no motion.
However, flexion/extension motion “was well-preserved from 11° to 12.5° in the disc replacement group,” Pradhan and colleagues wrote in their abstract.
Similarly, TDR patients experienced preservation of side bending motion postoperatively, going from 5.9° preoperatively to 5°. Those with fused discs lost more than 4° of that motion. All patients Pradhan reported on saw marked improvement in arm and neck pain, much of which was maintained for up to 2 years postop.
Investigators for both studies reported few major complications, but the patients with TDR that Janssen discussed lost more blood than those having a fusion.
One patient in Pradhan’s study randomized to receive the Prodisc-C implant needed a fusion to manage continued pain and another in the ACDF group had a nonunion. But investigators found no difference in complications between the two groups, he said.
The Prodisc-C disc arthroplasty system is not FDA approved for use in the United States and is only used investigationally.
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Images: Janssen ME |
For more information:
- Delamarter RB, Bae HW, Kropf M, et al. Cervical disc replacement: 2 to 3-year range of motion and clinical outcomes follow-up with the Prodisc-C prosthesis.
- Janssen M, Datta J, Murrey D, et al. Cervical disc arthroplasty: Preliminary results of a randomized prospective study of ACDF versus Prodisc-C for the management of cervical spondylosis. #125. Presented at the North American Spine Society 21st Annual Meeting. Sept. 26-30, 2006. Seattle.
- Michael E. Janssen, DO, is with the Spine Education and Research Institute, 905 Grant St., Suite 100, Denver, CO 80229. He can be reached at 720-540-7374, fax: 720-540-7379, or drmjanssen@aol.com. He has indicated that he is the chairman of AOSpine International and has a consultant arrangement with Synthes Spine.
- Ben B. Pradhan, MD, is with The Spine Institute at St. John’s Health Center, 1301 20th St., Suite 400, Santa Monica, CA 90404. He can be reached at 310-828-7757, fax: 310-828-6847, or bpradhan@hotmail.com.
- Drs. Delamarter and Pradhan have indicated that they have received grant and/or research support from Synthes Spine. Drs. Janssen and Murrey have indicated that they have received grant and/or research support from Synthes Spine.