Comparison of 2 Lumbar Total Disc Replacements Results of a Prospective, Randomized, Controlled, Multicenter Food and Drug Administration Trial With 24-Month Follow-up

Study Design. This was a prospective, randomized, controlled multicenter study with 24-month follow-up. Objective. The purpose of this study was to evaluate the safety and effi cacy in a Food and Drug Administration Investigation Device Exemption of a new lumbar total disc replacement (TDR) by comparing it to an earlier TDR approved for sale. Summary of Background Data. Randomized trials have reported TDR to produce results similar or superior to lumbar fusion. Results for various TDRs seem to be similar, but differences in study design and outcome measures pose challenges in defi nitively comparing devices. The purpose of this study was to perform a direct comparison of 2 lumbar TDRs in a prospective, randomized trial. Methods. TDR was performed in 457 patients from 21 sites (261 patients in the investigational group (Kinefl ex-L Disc; metal-on-metal design anchored with keels, 204 randomized and 57 nonrandomized training cases), and 196 in the control group (CHARITE artifi cial disc; metal with polyethylene core with teeth for anchoring; 190 randomized and 6 nonrandomized training cases). All patients were treated nonoperatively for single-level symptomatic disc degeneration for at least 6 months prior to surgery. Perioperative data were collected. Clinical outcome data were collected prospectively, as approved by the Food and Drug Administration, through 24-month follow-up. Primary outcome measures used were the Oswestry Disability Index, visual analogue scales assessing pain, patient satisfaction, and reoperations. Success was defi ned to be at least 15-point improvements in Oswestry Disability Index scores, no reoperation, and no major adverse events. Radiographical measures included range of motion, disc space height, and assessment for device migration, subsidence, and fusion at the TDR level. Results. There were no signifi cant differences between the groups when comparing operative time, blood loss, or length of hospital stay. Both groups improved signifi cantly on Oswestry Disability Index and visual analogue scale scores (P < 0.01) with no differences between the groups. Success rates were similar (68.1% investigational vs. 67.4% control). At 24-month follow-up, 94.1% of the investigational group and 91.9% of controls were satisfi ed with outcome. Reoperation was performed in 10.3% of the investigational group and 8.4% of the control group. Conclusion. This prospective, randomized, controlled study comparing 2 TDRs, the fi rst to the authors' knowledge, found the devices produced very similar clinical outcomes. Both groups improved signifi cantly by 6 weeks postoperatively and remained improved throughout follow-up with a high patient satisfaction rate.