The Feasibility of Optimal Surgical Result Prediction according to the Center of Rotation Shift after Multilevel Cervical Total Disc Replacement

STUDY DESIGN: Retrospective design/spine clinic and tertiary referral hospital. PURPOSE: This study investigated the association between shifted location of center of rotation (COR) and subsequent surgical outcomes and identified radiological parameters that corresponded to COR change after multilevel cervical total disc replacement (MCTDR). OVERVIEW OF LITERATURE: Cervical total disc replacement (TDR) maintains normal cervical kinematics after surgery. However, there is a paucity of literature analyzing the relationship between radiological shifts of COR and subsequent clinical success, especially when it comes to the issue of MCTDR switch. METHODS: This study included 24 consecutive patients treated with MCTDR following the diagnosis of multilevel cervical disc herniation or stenosis. Numeric rating scale, range of motion (ROM) at both C2–7 segment and TDR implanted levels, and location of COR at TDR level were evaluated pre- and post-MCTDR. These parameters were compared between patients who experienced successful and unsuccessful pain relief. RESULTS: The inherent CORs relatively at ventrocranial coordinates demonstrated significant migrations to dorsocaudal location, more prominent shifts for the successful group, after MCTDR switch. The unsuccessful group showed markedly reduced C2–7 ROM and reduced angular improvement at C2–7 segment and MCTDR level compared with the successful group. Postoperative C2–7 ROM was related to postoperative COR along the x-axis. CONCLUSIONS: Aside from ROM preservation at both C2–7 and TDR levels, COR restoration from ventrocranial location close to normal coordinates by posterior and inferior shifts was marked as a clinical success after MCTDR. The COR position along the x-axis after MCTDR was an important factor to determine maintenance of C2–7 ROM.