BACKGROUND
Although total disc replacement has been performed for years outside the United States, relatively little available data address clinical outcomes, particularly data from prospective studies. We report the 24- to 36-month follow-up of one center’s experience with the ProDisc-L artificial disc as part of a prospective, randomized trial comparing total disc arthroplasty to combined anterior–posterior lumbar fusion.

METHODS
The study involved clinical results for 157 patients from a single center enrolled in the US Food and Drug Administration–regulated trial comparing ProDisc-L to fusion. Only patients who had reached a minimum 24-month follow-up were included in the study. Patients were randomized to receive total disc replacement or circumferential fusion at 1 or 2 lumbar disc levels from L3 to S1, with specific inclusion and exclusion criteria. Data were collected preoperatively and at 6 weeks to 36 months postoperatively. The primary clinical outcome measures were Visual Analog Scale (VAS) scores to assess pain and Oswestry Disability Index (ODI) scores to measure function.

RESULTS
The VAS and ODI scores in both treatment groups improved significantly as early as the 6-week follow-up visit and remained significantly improved throughout the 36-month follow-up

period. Although a tendency was observed for the ProDisc-L scores to indicate more favorable outcome, the differences were not statistically significant. The proportion of patients who would have the same procedure again was greater in the total disc replacement group at all follow-up intervals, and significantly greater at the 6-month, 12-month, 24-month, and 36-month follow-up visits.

CONCLUSIONS
The results of this study indicate that the total disc replacement with ProDisc-L produces improvements in pain and function that are at least as good as those provided by circumferential fusion. During the long-term follow-up of 24 and 36 months, outcomes did not become less favorable compared with the early outcomes.

CLINICAL RELEVANCE
We found that results of total disc replacement were at least as good as those achieved with combined instrumented anterior–posterior fusion for the treatment of painful disc degeneration. Favorable results were maintained during 24- and 36-month follow-up.

Key Words artificial disc, spine arthroplasty, lumbar spine, prospective study, spinal fusion. SAS Journal. Spring 2007;1; 63–67. DOI: SASJ-2006-0003-RR

From the Texas Back Institute, Plano, Texas (Zigler, Sachs, and Rashbaum), and the Texas Back Institute Research Foundation, Plano (Ohnmeiss).

One or more of the authors or the institutions with which they are affiliated has the following disclosures: consulting agreement, funding for travel to lecture, and research and education support from the manufacturer of the ProDisc (Synthes, West Chester, Pa), and has received funding in excess of $1000.

Address correspondence and reprint requests to Jack E. Zigler, MD, Texas Back Institute, 6020 W Parker Rd, Suite 200, Plano, TX 75093 (email: jackzigler@juno.com).

This submission was received December 7, 2006, and accepted for publication March 28, 2007.

The study was conducted under a protocol approved by Presbyterian Hospital of Dallas, Texas.