The effect of lumbar total disc replacement on the spinopelvic alignment and range of motion of the lumbar spine.

A lumbar total disc replacement (TDR) is a type of motion-preserving surgery, which aims to restore and maintain the normal range of motion (ROM) and the sagittal balance of the spine. However, little is known regarding how the spinopelvic alignment and ROM of the lumbar spine are influenced by the lumbar TDR with ProDisc. This study retrospectively analyzed the sagittal alignment and ROM of the lumbar spine in 26 consecutive patients who had undergone the TDR with ProDisc with a minimum follow-up of 24 months. A standing lateral radiograph, which included the femoral heads and dynamic flexion-extension lateral radiographs of the spine were taken before surgery and at the follow-up visit. The radiological parameters included the sacral tilt, the pelvic tilt, and the lumbar lordosis. The segmental lordosis and ROM were also measured at each operative level. Nineteen patients underwent a single-level TDR and 7 patients underwent a double-level TDR. The mean lumbar lordosis increased significantly from 30.5 degrees to 40.8 degrees in all patients who underwent TDR without any significant changes in the sacral tilt and pelvic tilt at the latest follow-up (P<0.05). In the patients who underwent single-level TDR, the mean segmental lordosis at the L5-S1 and L4-5 operative levels increased significantly from 15.8 degrees to 23.2 degrees and from 14.1 degrees to 24.9 degrees, respectively. The mean ROM at L5-S1 and L4-5 increased significantly from 7.1 degrees to 11.2 degrees and from 11.4 degrees to 14.6 degrees, respectively. The sagittal balance and ROM of the lumbar spine improved significantly after the lumbar TDR.