29. Imaging outcome at 24-month follow-up in a prospective, multicenter study of two-level cervical arthroplasty with a PEEK on ceramic artificial disc

Abstract

<h3>BACKGROUND CONTEXT</h3> The use of cervical total disc replacement (cTDR) continues to increase. The implants continually evolve with respect to design and materials. Imaging studies of these devices provides insight to their ability to provide and maintain range of motion (ROM), disc height, and depending on the implant materials, facet joint assessment. <h3>PURPOSE</h3> The purpose of this study was to evaluate the imaging outcome of a PEEK-on-ceramic artificial disc for the treatment of two-level cervical disc disease. <h3>STUDY DESIGN/SETTING</h3> Data for this study came from a prospective, multicenter, non-randomized, historically controlled FDA Investigational Device Exemption (IDE) trial evaluating the Simplify®Cervical Artificial Disc for use at two levels. <h3>PATIENT SAMPLE</h3> Two-level cTDR was performed in 182 patients treated for symptomatic cervical disc degeneration with radiculopathy/myelopathy. <h3>OUTCOME MEASURES</h3> The primary outcome measures were ROM, disc height, and heterotopic ossification (HO) of the treated levels. MRI was used to assess the facet joints. <h3>METHODS</h3> The cTDR is composed of PEEK endplates with a mobile ceramic core. Radiographic evaluations were performed preoperatively, at hospital discharge, and 6 weeks, and 3, 6, 12, and 24 months postoperatively. MRI was performed pre- and 24 months postoperatively. All images were evaluated by an independent core lab. HO was evaluated based on a 0 (normal) to 4 (bridging bone) scale. Facets joints were scored on a 4-point scale ranging from 0 (normal) to 3 (severe degeneration) based on the MRI performed pre- and 24 months postoperatively. <h3>RESULTS</h3> At the superior cTDR level, the mean ROM improved from 8.0° prior to surgery to 9.5° at 24-month follow-up. At the inferior level, the values were 6.6° and 8.9°, respectively. At both operated levels, mean disc height increased postoperatively and the increase was maintained through 24-month follow-up. At the superior index level, the preoperative mean height was 3.1 mm and at 24 months it was 4.3 mm. At the inferior index level, the preoperative height was 3.1 mm and was 4.0 at 24 months. HO rates at 24-month follow-up were, the superior index level, severe HO (Grade 3) occurred in 8 patients (5%). Bridging HO (Grade 4) was also seen in 8 patients (5%). At the inferior index level, severe and bridging HO was seen in 17 (10%) and 5 (3%) patients, respectively. There was a lack of facet degeneration progression assessed on MRI between pre- and 24-month follow-up. No patient had severe facet degeneration at either operated level at either time point. The percentage of patients with a grade of moderate facet degeneration did not change at either level 8% at the superior index level and 5% at the inferior index level. At both levels, there appeared to be patients changing from the "none" category to the "mild" category. At the superior level prior to surgery, the figures for "none" and "mild" were 62% and 30% respectively. At 24-month follow-up, the figures were 52% and 39%, respectively. A similar pattern was seen at the inferior index level. <h3>CONCLUSIONS</h3> This study adds to the expanding evidence that two-level cTDR increases and maintains ROM and disc height and through 24-month follow-up. The majority of cTDR patients did not experience bridging HO. This PEEK-on-ceramic cTDR produces minimal artifact, allowing for reliable MRI visualization. This was used to evaluate the facet joints and a lack of facet degeneration progression was found. <h3>FDA DEVICE/DRUG STATUS</h3> Simplify Cervical Artificial Disc 2-level (Approved for this indication).