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The following results were recently published in the neurosurgical literature. These results were currently under consideration by the FDA, who cleared the Prestige ST cervical artificial disc system for use in the United States July 16th, 2007. CINN neurosurgeons Dean Karahalios, MD and Noam Stadlan, MD have been trained to implant the Prestige ST cervical artificial disc and have been selected to train other surgeons to use the device, once it is approved.

Prestige ST IDE Trial Results

Animation of Prestige Cervical Artificial Disc System

FDA Clearance Received for First Artificial Disc

Following are the results of the prospective randomized multicenter study in which the results of cervical disc replacement were compared with anterior cervical discectomy and fusion (ACDF) in patients treated for symptomatic single-level cervical degenerative disc disease (DDD).

541 patients with single-level DDD and radiating pain into the arm (radiculopathy) were enrolled at 32 sites across the country.

Approximately 50% of the patients were randomly assigned to both the cervical disc treatment group and the standard care ACDF group. Between 75-80% of the patients in both groups were followed for two years after surgery.

The Prestige ST is a two-piece device completely constructed with stainless-steel. The disc is inserted into the spine through an incision in the front of the neck. The end-plates of the device are secured using bone screws into the vertebral bodies of the spine above and below the diseased disc. The plates move using a "ball-and-trough" mechanism, with a ball portion attached to the upper end-plate and the trough is molded into the bottom end-plate.

The key results of the 2-year study are as follows:

All Prestige ST disc replacement systems maintained motion at the operative level 24 months after implantation
The Neck Disability Index (NDI) is used to measure the effects of neck pain associated with activities of daily living. The improvement in the NDI score was greater in the disc replacement group than in the fusion group at all follow-up time points (6 weeks, 3, 12, 24 months). At 6 weeks and 3 months the improvement difference in NDI score between the two groups was statistically significant, indicating that patients recover faster from artificial disc replacement than from ACDF.
The median return-to-work time for patients in the disc replacement group was 45 days, 16 days fewer than in the fusion group.
The neurological status of the patients was determined by measuring motor function, sensory function, and deep tendon reflexes. The neurological success for each of these three indicators was based on a comparison of pre-surgical status at each of the follow-up time points (6 weeks, 3, 12, 24 months). Neurological success is determined if a patient has maintained the same status or has improved. In the artificial disc group, neurological success rates exceeded 90% at all time intervals and were higher than those in the ACDF group. At 24 months, the artificial disc group success rate was 92.8% compared with 84.3% in the ACDF group. The overall rate of neurological success in the artificial disc group was statistically significantly higher than the rate in the ACDF group at both 12- and 24-month follow-up intervals.
A patient's overall success is the primary end point of the clinical trial. Overall success is based on a patient's successful outcomes with regards to NDI score (greater than a 14 point improvement from before surgery to after surgery) and maintenance or improvement in neurological status. At 12 months after surgery, the overall success rate in the artificial disc group was 77.6% compared to 66.4% in the ACDF group. At 24 months after surgery, the overall success rate in the artificial disc group was 79.3% compared to 67.8% in the ACDF group. The higher success rates in the artificial disc group at both time intervals were statistically superior.
Additional surgeries were required in both groups for adjacent-segment disease. Adjacent-segment disease is thought to occur more rapidly after fusion as increased stress and motion is redistributed from the treated segment to the other non-fused areas of the spine. In the artificial disc group, there was a statistically significant lower rate of reoperation for adjacent-segment disease than the ACDF group. Use of the artificial disc allows the diseased segment to retain motion, thereby absorbing its fair share of the stress on the spine.