4. Single-level cervical disc replacement using a PEEK-on-ceramic implant: Results of a multicenter FDA IDE trial with 24-month follow up

Abstract

<h3>BACKGROUND CONTEXT</h3> Many early cervical total disc replacements (TDRs) produced motion through a ball-and-socket action, with metal endplates articulating with a plastic core. PEEK is used increasingly for spinal implants due to its mechanical properties and lack of artifact on imaging. A cervical TDR was designed with commercially pure titanium-coated PEEK endplates and a biconvex zirconia toughened alumina ceramic core. <h3>PURPOSE</h3> The purpose of this study was to compare this PEEK-on-ceramic TDR to anterior cervical discectomy and fusion (ACDF) to treat single-level cervical disc degeneration. <h3>STUDY DESIGN/SETTING</h3> This was a prospective, nonrandomized, multicenter Food and Drug Administration (FDA) Investigational Device Exemption (IDE) trial comparing the investigational group to a propensity-matched historic control group. <h3>PATIENT SAMPLE</h3> Patients received the PEEK-on-ceramic Simplify® Cervical Artificial Disc (n=150 patients from 16 sites). The historic control group included 117 propensity-matched ACDF patients from an earlier cervical TDR IDE trial employing the same inclusion/exclusion criteria. All patients were treated for single-level symptomatic cervical disc degeneration. <h3>OUTCOME MEASURES</h3> The primary outcome was a composite 5-point success classification at 24-month follow-up requiring: >15 point (of 100) improvement in Neck Disability Index (NDI) score; 2) maintenance/improvement in neurologic status; 3) no device failure; 4) no reoperation/revision/removal and/or supplemental fixation at the index level, and 5) no major adverse events. Outcome measures included NDI, visual analog scale (VAS) assessing neck and arm pain, neurological status, adverse events and subsequent surgery. Radiographic assessment included flexion/extension range of motion. Facet joints were assessed at 24 months comparing pre- to postoperative MRI images using a published 4-point scale. <h3>METHODS</h3> Evaluations were performed preoperatively and postoperatively within 2 and 6 weeks, and 3, 6, 12 and 24 months. The control was propensity match with ACDF patients from an earlier TDR vs ACDF trial, which used the same inclusion criteria and primary outcome assessments. <h3>RESULTS</h3> The overall composite success rate was significantly greater in the TDR group vs ACDF (93.0% vs 73.6%; p<0.001). Mean NDI, neck pain and arm pain scores improved significantly in both groups at all follow-up points. Mean NDI scores in the TDR group were significantly lower than ACDF scores at all follow-up points all p<0.01). Secondary surgical intervention was undertaken in 4 (2.7%) patients at the index level in the TDR group and 6 (5.1%) in the ACDF group. There were no significant differences in the rates of serious adverse events when comparing the two groups. The mean segmental range of motion of the treated level in the TDR group was 7.3° prior to surgery. This increased to 8.6° at 3-month follow-up and continued to increase to 9.6° at 24 months (p<0.001). Facet joint assessment by MRI at 24-month follow-up in the TDR group showed little change from preoperative. <h3>CONCLUSIONS</h3> The results of this study found that the Simplify® Cervical Artificial Disc produced outcomes similar or superior on some measures, including superiority in the composite success classification, compared with ACDF, for the treatment of single-level symptomatic cervical disc degeneration. ROM at the treated level increased from the preoperative value and was maintained throughout follow-up. Safety of the PEEK-on-ceramic disc was established with no device failures in the series. These results support that the device is a viable alternative to ACDF. <h3>FDA DEVICE/DRUG STATUS</h3> Simplify Cervical Disc Replacement (Approved for this indication)