Introduction Fusion has been the primary treatment for symptomatic disc degeneration unresponsive to non-operative care. The results for two-level fusion have generally been worse than for one-level. There is little information available concerning two-level total disc replacement (TDR), and none comes from prospective studies. The purpose of this study was to analyse the results of two-level disc replacement and compare these results to single-level cases performed at the same centre.

Methods This data was collected from a single center participating in a multicentre a prospective, FDA-regulated clinical trial evaluating the ProDisc. This study is based on data from the first 105 patients (36 2-level and 69 one-level) enrolled who have reached a minimum of 12 months follow-up (data for 18 and 24 month were included if available at the time of data analysis). All patients were treated for symptomatic disc degeneration unresponsive to non-operative care. Data were collected pre-, peri-, and 6 weeks and 3, 6, 12, 18, and 24 months post-operatively. Outcome data included visual analog scale (VAS) assessing pain, Oswestry Disability Questionnaire, patient satisfaction (VAS ranging from 0 to 10), and a question asking patients if they would have the same surgery again. Within the 1-level and 2-level subgroups, pre- and postoperative data were compared to determine if there was improvement. The percentage of change in the pre- to post-operative scores was compared to determine if there were differences between the 1- and 2-level subgroups.

Results The mean estimated blood loss (1-level= 57.7 cc vs. 2-level = 76.7 cc), operative time (1-level = 61.6 min vs. 2-level = 96.7 min) and length of hospitalization (1-level=1.86 days vs. 2-level= 2.36 days) were significantly less in the single-level cases (p< 0.05). VAS pain scores improved significantly (p< 0.05) in 1- and 2-level cases. The mean improvement in 2-level cases was 58.7% and in 1-level cases 62.4% (p> 0.05). Between the one and two-level cases, there was no significant difference in the percentage of patients who would have the surgery again (86.6% vs. 77.8%; p> 0.05). The mean satisfaction score in the single-level TDR group was 8.2 and was 7.1 in the 2-level group (maximum score of 10).

Discussion This study found that both 1- and 2-level TDR results in significant improvement in pain and function scores. Patients undergoing 2-level disc replacement yielded outcomes similar to 1-level cases. These results support TDR as a viable treatment for 2-level symptomatic disc degeneration.