Low Risk of Adjacent Segment Degeneration Found Following Lumbar Total Disc Replacement

Richard D. Guyer, MD, comments on the findings from 5-year follow-up study data he presented at NASS 2017.

Total disc replacement in the lumbar spine was associated with a relatively low (<10%) risk of adjacent segment degeneration in a multicenter, prospective, randomized study presented by Richard Guyer, MD, at the North American Spine Society (NASS) 32nd Annual Meeting October 27, 2017 in Orlando, Florida. The study was one of the “Best Papers” presented at the meeting.

The findings are based on 5-year follow-up data from patients who underwent total disc replacement with the activeL (n=135) or ProDisc-L (n=63) device at one of 14 sites. All patients were treated for single-level symptomatic degenerative disc disease and had failed conservative treatment previously. The study was designed to compare pre- to post-operative changes of the disc adjacent to the level receiving total disc replacement.

“X-rays were obtained in flexion/extension, neutral lateral, and anterior/posterior, at each study visit,” explained Dr. Guyer, who is Co-Director of the Center for Disc Replacement at Texas Back Institute in Plano and Associate Clinical Professor of Orthopaedics at the University of Texas Southwestern Medical School in Dallas. The x-rays were analyzed by an independent laboratory (Medical Metrics). Adjacent segment degeneration was defined as an increase of 1 or greater grades on the Kellgren-Lawrence scale, comparing pre-operative to five-year follow-up benchmarks.1
Radiographic view of the spine superimposed on a woman’s back.Radiographic view of the spine superimposed on a woman’s back.The researchers also investigated whether range of motion at the total disc replacement level or age (<40 vs >40) were associated with a risk for adjacent segment degeneration.

Range of Motion and Age Linked to Risk for Adjacent Segment Degeneration
Adjacent segment degeneration was found in 8.8% of patients who received the activeL device compared to 19% of those who received the ProDisc device (P<0.05), Dr. Guyer told the audience. “The results were the same whether or not we used the Kellgren-Lawrence or the Zigler adjacent segment degeneration scale,” he said.

As shown in the Figure (below), the percentage of patients with adjacent segment degeneration decreased with each additional degree of range of motion at the total disc replacement level. For patients with ≥8-degree range of motion at the total disc replacement level 2.3% developed adjacent segment degeneration. For patients with a range of motion of ≤3-degrees, approximately 10% developed this condition.
Rate of adjacent segment degeneration decreased with increasing range of motion at the total disc replacement level. Rate of adjacent segment degeneration decreased with increasing range of motion at the total disc replacement level. Reprinted with permission from Richard Guyer, MD.Figure. Rate of adjacent segment degeneration decreased with increasing range of motion at the total disc replacement level. Reprinted with permission from Richard Guyer, MD.

The findings “suggests a protective effect of motion in preventing an increase in stress from the level above the total disc replacement,” Dr. Guyer said.

Patients aged >40 years had a significantly greater rate of adjacent segment degeneration than patients <40 years of age (19.6% vs 5.0%; P<0.01). The average age of patients who developed ASD was 43.2 years compared with 38.9 years in those who did not develop this condition.

“The higher rate of adjacent segment degeneration among older patients is multifactoral and not quite understood, but it may be attributable to the natural aging process,” Dr. Guyer said.

Conclusion
“The results of this prospective five-year, follow-up study suggest that the adjacent segment degeneration rate was 8.8% for the activeL,” Dr. Guyer reported. This rate is similar to 9.2% rate previously reported by Zigler et al in a five-year follow-up study of the ProDisc-L device.1 In that previous study, the adjacent segment degeneration rate following total disc replacement was significantly less than following fusion (28.6%).1

“This study lends further support that increased motion—for example, with the activeL device that was studied in this reported—reduces adjacent segment disease,” Dr. Guyer said. “These findings finally verify the holy grail for those of us who have dedicated decades to disc replacement. We now have substantiated proof that this is correct.”

Disclosures
Richard D. Guyer, MD’s disclosures.

Updated on: 11/10/17
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