Introduction: Lumbar total disc replacement (TDR) is intended to address discogenic pain and preserve functional motion between two vertebral bodies in patients with symptomatic degenerative disc disease. TDR may thus prevent long-term subsequent accelerated degeneration at adjacent disc levels. The ProDisc®-L TDR (Synthes Spine Company, L.P., West Chester, PA) was compared to circumferential spinal fusion for the treatment of discogenic pain at one vertebral level between L3-S1 and was found to be safe, effective, and superior to fusion in patients who meet the study inclusion criteria. However the safety and efficacy of lumbar TDR at two vertebral levels is still unproven. The purpose is to compare the safety and effectiveness of the ProDisc®-L TDR to circumferential spinal fusion for the treatment of discogenic pain at two vertebral levels between L3-S1.

Methods: A prospective, randomized, multi-center, FDA-regulated IDE clinical trial was conducted at 16 sites, utilizing a 2:1 randomization ratio (ProDisc®-L: Fusion). Patients were assessed pre-operatively and post-operatively at 6 weeks, 3, 6, 12, 18, and 24 months post-surgery. Each evaluation included patient self-assessments, physical and neurological examinations, and radiographic evaluation.

Results: 237 patients were treated on protocol. The patient follow-up rate was 89.6% at 24 months. Overall patient demographics showed no statistically significant differences between treatment groups in age, gender, race, smoking status, height, weight, body mass index (BMI), baseline Oswestry Low Back Pain Disability Questionnaire [Oswestry Disability Index (ODI)], or prior surgical treatment. Intra-operative data showed the ProDisc®-L group was significantly lower with regard to intra-operative time (ProDisc®-L = 132 min (range 66 – 430) min; Fusion = 275 min (range 86– 515 min), p < 0.0001), estimated blood loss (ProDisc®-L = 250 ml (range 0 – 3000 ml); Fusion = 400 ml (range 0 – 2000 ml, p = 0.0006) and hospital stay (ProDisc®-L = 4 days (range 1 – 10 days); Fusion = 5 days (range 2 – 14 days), p < 0.0001). At 24 months, 90.0% of ProDisc®-L and 86.7% of Fusion patients reported improvement in ODI from pre-operative levels and 73.3% of ProDisc®-L and 55.9% of Fusion patients met the 15 point ODI improvement criteria. Overall neurological success in the ProDisc®-L group was superior to the Fusion group (ProDisc®-L = 89.2%, Fusion = 77.9%; p = 0.0260). At all follow-up time points, the ProDisc®-L patients recorded SF-36 scores significantly higher than the Fusion group (p = 0.0523). The Visual Analog Scale (VAS) pain assessment showed statistically significant improvement from pre-operative scores regardless of treatment (p < 0.0001); at 24 months, the ProDisc®-L group showed significantly higher pain reduction than the Fusion group (p = 0.0466). VAS patient satisfaction at 24 months showed a statistically significant difference favoring ProDisc®-L patients over the Fusion group (p = 0.002). Radiographic range of motion was maintained within a normal functional range.

Discussion: Currently the ProDisc®-L TDR is only FDA approved for single level use. However, in this study, it has been found to be effective for the treatment of discogenic pain at two vertebral levels. In properly chosen patients, ProDisc®-L has been shown to be superior to circumferential fusion at two levels by multiple clinical criteria.

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.