Vertebral Fracture vs. Degenerative Spine Disease: A Retrospective Cohorts Study of the Effect of Fusion Indication on Risk of Pseudarthrosis using a National Research Network

Introduction: Spinal fusion surgery is a common procedure with over 400,000 performed annually in the U.S. This technique is utilized for stabilization in trauma and degenerative patients. Pseudarthrosis, or failure to obtain solid bony fusion, is a potential complication with an incidence of 5-35% and a major source of increased postoperative pain and morbidity.

Methods: The TriNetX U.S. Collaborative Network was queried for adults ≥18 years that underwent primary spinal fusion for either vertebral fracture or degenerative disease within the past 20 years. The cohorts were analyzed by calculation of risk ratio both before and after propensity matching for demographic and procedural factors as well as pseudarthrosis risk factors (General Cohorts). Another set of cohorts was created to model healthy patients, by exclusion of pseudarthrosis risk factors from the cohort design. Analysis was performed only after matching for demographic and procedural variables. The outcome measure was diagnosis of pseudarthrosis at 1-5 years post-surgery.

Results: The general unmatched analysis compared 178,930 degenerative patients to 31,183 fracture patients that underwent fusion at any spinal level. There was increase in relative risk for pseudarthrosis of 66.5% (P < 0.001) for degenerative relative to fracture treatment with 10,369 degenerative patients (D) and 1,085 fracture patients (F) diagnosed. The general matched cohorts each included 19,154 patients. Relative risk of pseudarthrosis was 85.6% higher in degenerative patients than fracture patients (P < 0.001; 1,138D, 613F). The matched, healthy patient cohorts each included 1,615 patients. Relative risk of pseudarthrosis increased by 195.9% for degenerative relative to fracture treatment (P < 0.001; 145D, 49F).

Conclusion : These results indicate that patients treated for degeneration with fusion have significantly greater risk of pseudarthrosis than patients treated for vertebral fractures. This relationship is present regardless of confounding variables, but more clinically relevant in otherwise healthy patients. We hypothesize that the pathophysiology of degenerative disease may influence the formation of new bone.