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.