11. Clinical outcome of a prospective, controlled, multicenter study evaluating two-level cervical arthroplasty with a PEEK-on-ceramic artificial disc

BACKGROUND CONTEXT

Over the past two decades, there has been increasing use of cervical total disc replacement (cTDR) with designs and materials continually evolving. Nine devices have been FDA approved for 1-level use, and the current study led to the approval of a third device for two levels.

PURPOSE

The purpose of this study was to evaluate the safety and efficacy of a PEEK-on-ceramic artificial disc for the treatment of 2-level cervical disc disease.

STUDY DESIGN/SETTING

This was a prospective, non-randomized, historically controlled multicenter FDA Investigational Device Exemption (IDE) trial evaluating the Simplify®Cervical Artificial Disc (NuVasive, Inc). The anterior cervical discectomy and fusion (ACDF) control group was derived from a propensity score matched (using subclassification) cohort of patients who participated in an earlier prospective cTDR trial using similar indications.

PATIENT SAMPLE

The cTDR group (n=182) was compared with ACDF patients (n=170). All patients had 2-level, symptomatic cervical disc disease with radiculopathy and/or myelopathy.

OUTCOME MEASURES

The primary outcome measure was classification of success at 24-month follow-up based on 4 criteria (1) at least 15-point (of 100) improvement in Neck Disability Index (NDI) scores; (2) maintenance or improvement in neurological status; (3) no serious adverse event classified as implant associated or implant/surgical procedure associated; and (4) no additional index level surgery. Secondary evaluations included NDI scores, numeric rating scales assessing neck and arm pain intensity and frequency, and patient satisfaction. Safety was assessed by adverse events and subsequent surgery at an index level.

METHODS

Patients were evaluated preoperatively, at hospital discharge, 6 weeks, and 3, 6, 12, and 24 months after surgery.

RESULTS

The overall composite success rate was statistically significantly greater in the cTDR group compared with the ACDF group (86.7% vs 77.1%; p 15 points at 24-mo follow-up) occurred in 92.9% of the cTDR group and 83.5% of the ACDF group (0.05 < p < 0.10). Mean NDI scores improved significantly in both groups by 6 weeks with cTDR scores significantly lower at 6 weeks and 3 and 6 months. Mean NDI scores in the cTDR group were 58.6 preoperatively and 14.3 at 24 months. In the ACDF group, the values were 53.6 and 17.2, respectively. In both groups, neck and arm pain improved significantly (p <0.05) by 6 weeks with improvement maintained throughout follow-up. In the cTDR group, the mean preop neck pain intensity score was 7.9 and 1.8 at 24 months. In the ACDF group, the values were 7.7 and 2.5, respectively. Improvement in arm pain followed a similar pattern with a preoperative mean value of 7.5 in the cTDR group which improved to 1.8 at 24 months. In the ACDF group, the values were 7.0 and 1.6. The ACDF scores were not superior to those in the cTDR group on any of the outcome measures. There were four subsequent surgical interventions (2.2%) in the cTDR group and 15 (8.8%) in the ACDF group.

CONCLUSIONS

The cTDR group had a statistically significantly greater overall clinical success rate compared to ACDF as well as similar to superior scores on the NDI and pain scales at all follow-up points. These results add to the growing body of literature supporting cervical arthroplasty for treating 2-level cervical disc disease with radiculopathy and/or myelopathy.

FDA DEVICE/DRUG STATUS

Simplify Cervical Artificial Disc: 2-level (Approved for this indication).