LATEBREAKER
Causal Inference
Decompression surgery with or without fusion in subgroups with degenerative lumbar spondylolisthesis Harrison Hansford* Harrison Hansford Margreth Grotle Tore Solberg Bjørnar Berg Christian Hellum Ivar Austevoll Tor Ingebrigtsen Issa Dahabreh Hopin Lee Matthew Jones James McAuley Aidan Cashin
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 two RCTs to have no benefit beyond decompression alone and comes with increased costs and complications (Försth NEJM 2016; Austevoll NEJM 2021). However, it is suggested some subgroups benefit from additional fusion.
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.
RESULTS From 2007-2021, 3817 patients underwent surgery for DS in NORSpine. We included 1409 patients who received decompression alone and 770 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.
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 are unlikely to be meaningful.