Effect of intervertebral disc height on the range of motion and clinical outcomes after single-level implantation of Prestige LP cervical disc prosthesis

Objectives: Cervical total disc replacement (TDR) is an emerging technology. Cervical arthroplasty theoretically reduces the risk of adjacent level disc degeneration and segmental instability. However, the factors that influence postoperative range of motion (ROM) and clinical outcomes are not fully understood. The aim of our study was to evaluate the effect of intervertebral disc height on the range of motion and clinical outcomes after single-level implantation of Prestige LP cervical disc prosthesis. Methods: A total of 160 patients with single-level Prestige LP cervical disc prosthesis were evaluated. Preoperative and postoperative disc height and ROM were measured from lateral and flexion-extension radiographs by the CANVAS, and the clinical outcomes were evaluated by Japanese Orthopaedic Association (JOA) and Neck Disability Index (NDI). Results: Patients with less than 4 mm of preoperative disc height had a mean 1.4 degrees increase in flexion-extension ROM after cervical arthroplasty, whereas patients with greater than 4 mm of preoperative disc height had no change in flexion-extension ROM. Patients with a 6-8 mm of postoperative disc height had significantly higher postoperative flexion-extension ROM (11.0 degrees +/- 2.9) than those with less than 6 mm of postoperative disc height (8.7 degrees +/- 3.1, p = 0.01). Patients with greater than 8 mm of postoperative disc height have significantly lower postoperative flexion-extension ROM (mean, 8.9 degrees +/- 3.2) than those with 6-8 mm of postoperative disc height (p = 0.03). No significant difference was found between patients with <6 mm of postoperative disc height and patients with >8 mm of postoperative disc height (p = 0.12). The postoperative JOA and NDI both have significant difference compared with preoperation(p < 0.05). No correlation could be found between disc height and the postoperative ROM, JOA or NDI. Conclusion: Patients with less than 4 mm of preoperative intervertebral disc height have a larger ROM after cervical arthroplasty. A 6-8 mm of postoperative intervertebral disc height is the optimum range to maximize ROM. However, the optimal range did not translate into better clinical outcomes. (C) 2016 Elsevier B.V. All rights reserved.