NASS 2020: Research Highlights from Three Top Studies

Pedicle screws, total disc replacement and more: Here are three of the top abstracts presented at the North American Spine Society conference 2020.

As a spine surgeon or other spine-health professional, you do your best to stay on top of the latest medical research. Of course, the sheer volume of abstracts, symposiums, and journals makes it impossible to keep up with it all. That’s why a research highlights section of the 2020 virtual conference of the North American Spine Society (NASS) was so valuable.

NASS 2020 research highlightsNASS 2020 conference organizers showcased abstracts throughout the conference. Get caught up here.

In "Featured Abstract Presentation: Best Papers," a session held each full day of the conference, researchers presented recent, key findings in moderated sessions. These are still available on the NASS 2020 conference website, but we’ve got three highlights for you here. 

Pedicle Screws

1. Low density pedicle screw constructs are associated with lower incidence of proximal junctional failure in adult spinal deformity surgery.

Proximal junction failure (PJF) is a common and severe complication of adult spinal deformity (ASD) surgery. Some research suggests the stiffness of posterior spinal constructs may play a role. In light of this, lead author Wesley Durand, MD, along with many collaborators, explored whether fewer mean screws per level and decreased rod stiffness were associated with lower incidence of PJF.

The retrospective cohort study analyzed results of 420 patients with ASD, a minimum two-year follow-up, and fusion of ≥5 levels. Revision surgery patients were excluded.

The study authors found that PJF occurred in about 14% of total patients: specifically, 19.4% of patients with ≥1.8 screws per level, and 9.8% of patients with <1.8 screws per level. Rod material and diameter, as well as screw density, were not significantly associated with PJF. Still, the study authors recommend further study on a potential relationship between screw density and PJF.

Lumbar TDR

2. Incidence and resolution strategies for early onset postoperative leg pain following lumbar total disc replacement.

Since lumbar total disc replacement (TDR) was introduced in the 1980s, there have been anecdotal reports of new-onset leg pain following the surgery. Noting a lack of formal investigation of the matter, researchers set out to quantify the incidence of leg pain after lumbar TDR and identify effective treatment strategies.

Scott L. Blumenthal, MD, and Richard D. Guyer, MD, both spine surgeons at the Texas Back Institute, were the lead investigators. Their study was based on prospective data collected for a U.S. Food and Drug Administration Investigational Device Exemption (FDA IDE) trial, which compared patients receiving two different brands of artificial discs.

Drs. Blumenthal and Guyer used adverse event reports to identify patients who developed new leg pain within a month of TDR surgery. They also identified four categories of treatment strategies: medication, nonoperative care, injections, and/or subsequent surgery. A few of their findings:

  • Postoperative leg pain occurred in 9.2% of lumbar TDR patients (26 out of 283)
  • The pain resolved in 76.9% of patients, often within 3 months of onset
  • Most patients were effectively treated with gabapentin or pregabalin
  • Twelve patients received other nonoperative care, such as physical therapy
  • Three patients went on to have subsequent surgery, which did not provide leg-pain relief

Though definitive conclusions can’t be drawn from this small subset of patients, the research suggests that gabapentin or pregabalin are likely effective treatments, and that surgical intervention is likely unnecessary. 

Reherniation After Decompression

3. The reherniation after decompression (RAD) score identifies patients at low risk for reherniation after lumbar decompression surgery.

Researchers have developed and validated a screening tool to identify patients with clear differences in risk for reherniation after lumbar decompression surgery.

The tool identified nine significant predictors for reherniation, including:

  • Age
  • Sex
  • Duration of preoperative symptoms
  • Paracentral disc herniation
  • Preoperative lumbar lordosis

These factor in the authors’ “reherniation after decompression” score, which identifies patients at low risk for reherniation after lumbar decompression surgery. (Paracentral disc herniations and duration of preoperative symptoms were the strongest positive and negative predictors for reherniation, respectively.)

Within the testing cohort, 16.3% patients were identified as high risk; 83.7% were identified as low risk. Nearly 30% of these high-risk patients had future reherniation, while nearly all low-risk patients did not.

Lead author Garrett Harada was asked by the moderator how his research could best be used in clinical practice. He had this to say:

 “I believe the tool [would be] best used to preoperatively counsel patients and establish postoperative expectations. It's unclear if the score can be extrapolated to other centers at this time, but roughly 99% of patients identified as low risk did not experience a future reherniation. The question remains on how best to address the high-risk patients.”

Updated on: 11/16/20
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