Oral Presentation Sydney Spinal Symposium 2024

Decompression with or without fusion in subgroups of people with degenerative lumbar spondylolisthesis: a target trial emulation   (108121)

Harrison J Hansford 1 2 , Margreth Grotle 3 , Bjørnar Berg 3 , Hopin Lee 2 4 5 , Christian Hellum 6 , Matthew D Jones 1 2 , Tore Solberg 7 8 , Ivar Austevoll 9 , Tor Ingebrigtsen 10 11 , Issa J Dahabreh 12 , James H McAuley 1 2 , Aidan G Cashin 1 2
  1. UNSW, Sydney, NSW, Australia
  2. Centre for Pain IMPACT, Neuroscience Research Australia, Sydney, Australia, Sydney, Australia
  3. Center for Intelligent Musculoskeletal Health, Department of Rehabilitation Science and Health Technology, Oslo Metropolitan University, P.O. Box 4, St. Olavs plass, NO-0130, Oslo, Norway
  4. University of Exeter Medical School, University of Exeter, Exeter, United Kingdom
  5. IQVIA, London, United Kingdom
  6. Division of Orthopedic Surgery, Oslo University Hospital , Oslo, Norway
  7. Institute of Clinical Medicine, The Artic University of Norway, Tromsø, Norway
  8. The Norwegian Registry for Spine Surgery, The University Hospital of North Norway, Tromsø, Norway
  9. Kysthospitalet in Hagevik, Orthopedic Department, Haukeland University Hospital, Bergen, Norway
  10. Neurosurgery, Ophthalmology and Otorhinolaryngology, University Hospital of North Norway, Tromsø, Norway
  11. Australian Institute of Health Innovation, Macquarie University, Sydney, NSW, Australia
  12. CAUSALab, Harvard T.H. Chan School of Public Health, Boston, MA, USA

Background: Lumbar spinal surgery is indicated for patients with degenerative spondylolisthesis (DS) who have minimal improvement with non-surgical care. Adding fusion to decompression has been shown in three RCTs to have no, or mininal benefit beyond decompression alone and comes with increased costs and complications (Ghogawala 2016; Försth 2016; Austevoll 2021). However, it is suggested some subgroups benefit from additional fusion (Katz 2022).

Methods: Using observational data from the NORSpine registry we emulated the NORDSTEN trial (Austevoll 2021) to compare decompression alone to with additional fusion. We included patients aged 18-80 with a diagnosis of DS and back or leg pain for ≥3mo. We excluded those with previous surgery at the level of the DS. We estimated the between-group mean difference on the Oswestry Disability Index and reoperation rate at 1-year post surgery, and risk of peri-operative complications. Subgroups investigated were: back pain intensity, BMI, sex, age, ASA score, smoking status, and difficulty walking. We adjusted for confounding using inverse probability of treatment weighting including 20 baseline clinical, sociodemographic and hospital confounders.

Results: From 2007-2021, there were 3828 cases of surgery for DS in NORSpine. We included 1419 patients who received decompression alone and 774 who received additional fusion surgery. Our primary outcome had estimate agreement with the index trial (trial=0.7/100 95%CI -2.8-4.3; emulation=1.8/100, 0.1-3.5), favoring fusion surgery. There was no additional risk of reoperation (RR=1.2, 0.89-1.84) and lower risk of complications (RR=0.62, 0.41-0.95) from decompression alone. The subgroup with back pain >6/10 had a 3.2/100 (0.6-6) greater treatment effect from fusion than those with lower pain. All other subgroups were not significantly different. These results are preliminary pending final analyses being completed in July.

Conclusion: There may be small benefits of adding fusion to decompression alone, with this effect larger in people with higher back pain. However, additional fusion comes with increased risk of adverse events and effect sizes, even in subgroups are unlikely to be meaningful.