Progression of Adjacent-level Degeneration After Lumbar Total Disc Replacement: Results of a Post-hoc Analysis of Patients With Available Radiographs From a Prospective Study With 5-year Follow-up

STUDY DESIGN. Post-hoc analysis of 5-year follow-up data from a randomized, multicenter trial. OBJECTIVE. The aim of this study was to investigate the incidence of progression in radiographic adjacent-level degeneration (ΔALD) from preoperative assessment to 5 years after total disc replacement (TDR) and the relationship of these changes with range of motion and clinical adjacent-level disease. A secondary objective was to compare adjacent-level degeneration (ALD) outcomes between TDR and fusion. SUMMARY OF BACKGROUND DATA. Fusion is associated with high rates of ALD in symptomatic lumbar disc degeneration. TDR may reduce this risk. METHODS. In total, 175 patients with single-level, symptomatic, lumbar disc degeneration who had received activL or ProDisc-L and had a preoperative and 5-year postoperative radiograph available were included. Over 5-year follow-up, ΔALD was defined as an increase in ALD of ≥1 grade and clinical ALD was defined as surgical treatment at the level adjacent to an index TDR. Matching-adjusted indirect comparisons were conducted to compare ALD outcomes after TDR (current trial) with those after fusion (published trial). RESULTS. At 5-year follow-up, 9.7% (17/175) of TDR patients had ΔALD at the superior level. In patients with preoperative ALD at the superior level, most (88% [23/26]) showed no radiographic progression over 5 years. The rate of clinical ALD was 2.3% (4/175) and none of these patients had ALD at baseline. For each degree of range of motion gained at the TDR level, there was a consistent decrease in the percentage of patients with ΔALD. After matching and adjustment of baseline characteristics, TDR had a significantly lower likelihood of ΔALD than fusion (odds ratio 0.32; 95% confidence interval 0.13, 0.76). CONCLUSION. The rates of ΔALD and clinical ALD in this TDR population were similar to those previously reported in the literature for TDR at 5-year follow-up. TDR had a significantly lower rate of ΔALD than fusion. Level of Evidence: 3