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 4mm of preoperative disc height had a mean 1.4° increase in flexion-extension ROM after cervical arthroplasty, whereas patients with greater than 4mm of preoperative disc height had no change in flexion-extension ROM. Patients with a 6-8mm of postoperative disc height had significantly higher postoperative flexion-extension ROM (11.0°±2.9) than those with less than 6mm of postoperative disc height (8.7°±3.1, p=0.01). Patients with greater than 8mm of postoperative disc height have significantly lower postoperative flexion-extension ROM (mean, 8.9°±3.2) than those with 6-8mm of postoperative disc height (p=0.03). No significant difference was found between patients with <6mm of postoperative disc height and patients with >8mm 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 4mm of preoperative intervertebral disc height have a larger ROM after cervical arthroplasty. A 6-8mm of postoperative intervertebral disc height is the optimum range to maximize ROM. However, the optimal range did not translate into better clinical outcomes.