Mobility of Listhesis Key in Surgical Decision Making for Spondylolisthesis

OrthoBuzz occasionally receives posts from guest bloggers. This guest post comes from Brett A. Freedman, MD, in response to two recent NEJM studies on treating spondylolisthesis.

The April 14, 2016 edition of The New England Journal of Medicine published results from two randomized clinical trials (RCTs) evaluating the benefits of laminectomy alone versus laminectomy and fusion for the treatment of specific spinal conditions in patients 50 to 80 years old, with at least 2-year follow-up. The larger study was conducted in Sweden and included 247 patients, 135 of whom had degenerative spondylolisthesis of some magnitude. In this study, the surgical technique varied and was left to the treating provider’s preference. The ultimate conclusion of this study was that adding fusion to the procedure did not result in better patient outcomes by any index measured.

Conversely, an essentially concurrent but unrelated RCT evaluating similar outcomes in a US patient population (n=66) with degenerative spondylolisthesis that measured at least 3 mm, but in which there was no instability, concluded that spinal fusion, using a standardized technique (pedicle screws and rods with iliac crest bone graft), did provide a significant clinical benefit. Specifically, this study found significant improvement in SF-36 physical-component summary scores (the primary outcome measure) and lower reoperation rates (14% vs. 34%; p=0.05) compared to decompression alone.

When two Level 1 studies published on the same day in the same high-impact journal come to divergent conclusions about the same clinical question, we must pause and look to the past. Spine surgeons have investigated decompression alone for spondylolisthesis, first by necessity (prior to the era of reliable spinal fusion) and then later in comparison to in-situ and instrumented fusion1,2. Consensus is consistent with anatomic reasoning. Dysfunctional lumbar mobile segments, especially those with preserved or excessive motion (i.e. >2 to 4 mm change on flexion-extension films), produce a mechanical pathoanatomic sequence of events that leads to critical and clinically symptomatic spinal stenosis. Addressing this first cause is paramount.

The immediate effect of surgery type is largely neutralized by the fact that the decompression component, which is common to both approaches, is principally responsible for acute improvement. Because most prospective studies are not able to reliably track patients beyond 2 to 5 years, the longer-term benefits of a solid arthrodesis of a dysfunctional spinal-motion segment compared to a simple decompression in which some of the incompetent posterior elements are further surgically removed remain largely unknown. Anecdotally, spine surgeons recognize that failures of decompression alone in mobile spondylolisthesis occur quite frequently—and that revision fusion surgery in this situation is significantly more complicated than primary decompression and fusion. That was the case in the Swedish study, where the majority of revision surgeries in the decompression-only cohort were performed at the same level as the prior surgery, versus adjacent levels in the fusion group. And, again, reoperation rates were significantly higher (>2x) in the decompression-only group in the US study.

Given conflicting data3, there likely are cofactors that need to be identified and further studied to select cases of spondylolisthesis that can be treated well with decompression alone, versus those that require the stabilizing effect of a fusion. Until then, surgeons must weigh the data available and provide the surgical option they feel is best for each individual patient.

Brett A. Freedman, MD is an orthopaedic surgeon specializing in spine trauma and degenerative spinal diseases at the Mayo Clinic in Rochester, MN

References

  1. Fischgrund JS, Mackay M, Herkowitz HN, Brower R, Montgomery DM, Kurz LT. Degenerative lumbar spondylolisthesis with spinal stenosis: a prospective, randomized study comparing decompressive laminectomy and arthrodesis with and without spinal instrumentation. Spine (Phila Pa 1976). 1997 Dec 15;22(24):2807-12.
  1. Bridwell KH, Sedgewick TA, O’Brien MF, Lenke LG, Baldus C. The role of fusion and instrumentation in the treatment of degenerative spondylolisthesis with spinal stenosis. J Spinal Disord. 1993 Dec;6(6):461-72.
  1. Joaquim AF, Milano JB, Ghizoni E, Patel AA. Is There a Role for Decompression Alone for Treating Symptomatic Degenerative Lumbar Spondylolisthesis?: A Systematic Review. J Spinal Disord Tech. 2015 Dec 24. [Epub ahead of print]

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