Noninstrumented Posterolateral Lumbar Fusions Continue to Fade Relative to Instrumented Posterolateral Approaches for Lumbar Degenerative Spondylolisthesis Over the Past Decade.

Introduction: Although posterolateral lumbar fusions (PLFs) were historically routinely performed without instrumentation, instrumentation has become ubiquitous in this setting. Recent assessments of noninstrumented PLFs practices are lacking.

Methods: Lumbar degenerative spondylolisthesis patients undergoing noninstrumented or instrumented single-level PLFs (with or without interbody) were identified from 2012 to 2022 M170 Ortho PearlDiver. Univariable analysis identified differences in patient characteristics. Yearly utilization trends were tracked and analyzed using simple linear regression/overall F-tests. Ninety-day postoperative adverse outcomes were compared using multivariable logistic regression with 4:1 matching for patient age, sex, and Elixhauser comorbidity index. Five-year lumbar revision surgery rates were assessed using Kaplan-Meier survival analyses and log-rank tests.

Results: A total of 117,796 (95.8%) instrumented and 5147 (4.2%) noninstrumented PLF lumbar degenerative spondylolisthesis patients were identified. Noninstrumented PLFs declined from 5.52% to 3.49% from 2012 to 2022 (P < 0.001). These were more common in older, male, osteoporotic patients, varied by insurance and region, and were more often performed by orthopaedic surgeons. After matching, no notable differences were found between instrumented versus noninstrumented cases in 90-day aggregated adverse events or 5-year lumbar revision surgery rates.

Discussion: For lumbar degenerative spondylolisthesis, noninstrumented fusion represents a small and declining percentage of PLFs over the past decade, with usage varied by clinical and nonclinical patient characteristics. No differences were found in 90-day aggregated postoperative adverse events and 5-year lumbar revision surgery rates, suggesting that instrumentation can be safely performed and that both approaches had similarly durable results. These findings support considering noninstrumented PLFs in select cases when the safety, utility, or cost-benefit of instrumentation is questioned.