Clinical and Radiologic Findings After Multilevel Cervical Total Disk Replacement: Defining Radiologic Changes to Predict Surgical Outcomes

Objective This study compared the radiologic parameters between preoperation and postoperation for patients who underwent multilevel cervical total disk replacement (MCTDR) and assessed which parameters were related to successful clinical outcomes after MCTDR. Methods The study included a consecutive series of 24 patients who were treated with MCTDR following the diagnosis of multilevel cervical disk herniation or stenosis. Numeric Rating Scale, C2-7 sagittal vertical axis, range of motion (ROM) of C2-7 segment, and total disk replacement (TDR) implanted levels were evaluated at pre- and post-TDR. These parameters were compared between patients who experienced successful and unsuccessful pain relief. Results Numeric Rating Scale scores were reduced while C2-7 sagittal vertical axis improved significantly after MCTDR. C2-7 flexion was significantly decreased (P < 0.05), while its extension showed trends toward considerable (P = 0.088) increase, thereby maintaining original C2-7 ROM without statistical significance. TDR flexion was decreased (P < 0.05), while its extension changes were stationary, consequently resulting in a significant decrease in TDR ROM (P < 0.05). The unsuccessful group showed markedly reduced ROM and lack of ROM angular change maintenance at both the C2-7 and MCTDR levels (P < 0.05) compared with the successful group. Conclusions MCTDR was effective in reducing pain and improving cervical lordosis in patients with multilevel cervical disk herniation or stenosis. Despite a significant decrease in the flexion angle, it could maintain C2-7 ROM presumably by compensating with C2-7 extension angle increase. Clinical success after MCTDR was crucially related to retaining original C2-7 ROM and minimizing ROM angular changes at both the C2-7 and MCTDR levels.