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The Spine Blog

Friday, October 27, 2017

Long-term results of lumbar disk replacement

Concerns about the long-term durability of lumbar total disk replacement (TDR) along with mediocre outcomes has tempered enthusiasm for the procedure. Most of the industry-sponsored FDA trials had relatively short follow-up periods, so the long-term fate of lumbar TDRs has not been well-studied. In order to address this gap in the literature, Laugesen and colleagues from Denmark reported their long-term (average 10.6 years of follow-up) outcomes in 57 patients treated with lumbar TDR between 2003 and 2008. This represents an 84% response rate among patients still alive at the time of long-term follow-up, which is a rather impressive 10 year follow-up rate. All patients were diagnosed with degenerative disk disease (DDD) based on their baseline MRI and underwent one, two, or three level (only 1 patient underwent a 3 level procedure) lumbar TDR. The average age at surgery was 38.7 years, and 77% of patients were women. Back pain VAS improved by over 3 points on a 10 point scale, and there were significant improvements on the Dallas Pain Questionnaire. The SF-36 physical component score improved by 7 points, which is in the range of the minimally clinically important difference. About half of the patients reported they would have the operation again. One third of patients had undergone a fusion operation at the index level, and these patients had worse long-term outcomes than those who had not undergone a revision procedure. The authors did not report the rate of adjacent segment disease (ASD) or the rate of surgery at adjacent levels.

This is an interesting study as it provides a glimpse into long-term outcome following lumbar TDR. Outcomes were similar to what one would expect, with statistically significant albeit modest improvements on patient reported outcomes. The 33% rate of subsequent fusion at the index level is somewhat surprising, indicating that the re-operation rate is even higher if events at adjacent levels were to be included. In the 8-year follow-up of the SPORT degenerative spondylolisthesis cohort (most of whom underwent fusion), the overall reoperation rate was 22%, substantially less than observed in the current study. There are important limitations of this study that need to be considered, namely that there was no comparison group (i.e. a fusion cohort). Additionally, they did not report the reoperation rate for ASD, so it is hard to know if TDR actually reduces the rate of ASD. There is also no discussion of morbidity associated with TDR failure (i.e. fracture, vascular injury, need for revision anterior procedure). Despite these limitations, this paper does provide some insight into the long-term results for lumbar TDR. Overall, lumbar TDR resulted in modest improvements in patient reported outcomes and a relatively high 10 year failure rate. Surgical treatment for lumbar DDD (including both fusion and TDR) has historically had mediocre results, probably related to difficulties in accurately diagnosing the pain generator selecting the patients who are going to respond well to surgery. It seems unlikely that enthusiasm for lumbar TDR is going to increase anytime soon.

Please read Mr. Laugesen’s article on this topic in the November 1 issue. Does this change your view of lumbar TDR? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor