Time course of radiologic changes after lumbar total disc replacement

Study Design: This was a retrospective observatory analysis study. Objective: The purpose of this study was to evaluate long-term safety and therapeutic effectiveness of the lumbar total disc replacement (TDR) using ProDisc-L by analyzing the radiologic changes at the index and adjacent levels in minimum 5-year follow-up. Summary of Background Data: Early successful clinical results of lumbar TDR have been reported. However, few reports have published its therapeutic effectiveness and radiologic degenerative changes at the index and adjacent segments in the long term. Materials and Methods: Forty-three patients were followed-up for at least 60 months. Radiologic changes were assessed by segmental range of motion (ROM) at the index and adjacent levels, global lumbar lordosis, and disc space height (DSH). The magnetic resonance imaging and computed tomographic scans were used to determine the facet arthrosis and intervertebral disc degeneration at the index and adjacent levels. Results: Gradual decrements of DSH restoration were observed until the last follow-up. Mean global and segmental ROM of index segments were significantly reduced (P=0.044, 0.00) at the last visit. There were 21 patients (48.8%) with no motion at index segment (ROM<0.5 degrees) at the last visit. Among the 56 segments operated on, progression of facet arthrosis was observed in 30.3% of index segments and 10.9% of adjacent segments. None of the postoperative radiologic parameters included in the present study presented significant correlation with clinical outcome. Conclusions: The study demonstrates that only half of the lumbar TDR patients can maintain segmental motion at the index level >5-year after surgery and TDR provides a good clinical outcome postoperatively regardless of motion preservation or DSH height preservation at the last follow-up. After TDR, the degenerative changes in the index and adjacent segments advanced as compared with our previous report of 2-year follow-up, however, these changes did not appear to exert negative influence upon clinical outcomes.