Effect of Intervertebral Height on Postoperative Motion and Clinical Outcomes after Single Segment Prestige LP Cervical Arthroplasty

Abstract：Objective To analyze the influence of pre-and postoperative disc height on postoperative range of motion (ROM)and clinical outcomes after single segment Prestige LP cervical disc replacement. Methods 63 cases underwent sin-gle segment Prestige LP cervical disc replacement from February 2008 to April 2013. All patients were examined on lateral and flexion-extension radiographs. The intervertebral height and flexion-extension ROM were measured by the CANVAS,and the clinical outcomes were evaluated by Japanese Orthopaedic Association(JOA)and Neck Disability Index(NDI). The influence of pre-and postoperative disc height on postoperative ROM was investigated,and the correlation between the disc height and postoperative ROM or clinical outcomes was analyzed. Results The postoperative segmental ROM was(10. 8 ± 3. 2)°,the preoperative segmental ROM was(10. 4 ± 3. 3)° without statistical significance(P > 0. 05). The postoperative disc height was (7. 0 ± 0. 9)mm,the preoperative disc height was(4. 6 ± 1. 0)mm with statistical significance(P < 0. 05). Patients with less than 4 mm of preoperative disc height had a mean 0 . 7 ° increase in flexion - extension ROM after cervical arthroplasty( P <0. 05),whereas patients with greater than 4 mm of preoperative disc height had no change in flexion-extension ROM(P >0. 05). The postoperative ROM of patients with greater than 6 mm of postoperative disc height was 11. 3°,the postoperative ROM of those with less than 6 mm of postoperative disc height was 8. 8° with statistical significance(P < 0. 05). The postoperative ROM of patients with less than 8 mm of postoperative disc height was 11. 2°,the postoperative ROM of those with greater than8 mm of postoperative disc height was 9. 1° with statistical significance(P < 0. 05),however,there is no significant difference in postoperative JOA and NDI between them(P > 0. 05). No correlation could be found between disc height and the postopera-tive ROM、JOA or NDI. Conclusion Patients with less than 4 mm of preoperative disc height benefit more in ROM after Pres-tige LP cervical disc replacement. The optimal postoperative intervertebral disc height range to maximize ROM is between 6 and 8 mm,however,the optimal range has no effect on clinical outcomes.