Increased Risk of Lumbar Fusion Following Sacroiliac Joint Fusion in Patients With Lumbar Degenerative Disease: A Nationwide Cohort Analysis.

Study DesignRetrospective Cohort Study.ObjectivesTo evaluate the risk of subsequent lumbar fusion following sacroiliac (SI) joint fusion in patients with lumbar degenerative disease (LDD) and identify associated risk factors.MethodsPatients with undergoing SI joint fusion with concurrent diagnosis of LDD between 2010-2022 were identified in the PearlDiver Mariner Database. Those with prior lumbar fusion were excluded. A 1:10 propensity-matched control group of LDD patients without SI joint fusion was created. Logistic regression assessed the odds of subsequent lumbar fusion. Risk factors were analyzed using multivariable regression. Kaplan-Meier analysis evaluated time to lumbar fusion over 5 years.ResultsAmong 22 957 patients with LDD undergoing SI joint fusion, 4.5% required subsequent lumbar fusion. SI joint fusion was associated with significantly higher odds of subsequent lumbar fusion compared to controls (OR: 2.97 [2.77-3.19], P < 0.001). Risk factors included open SI joint fusion (aOR: 2.78), bilateral fusion (aOR: 1.97), Elixhauser Comorbidity Index ≤ 4 (aOR: 1.91), preoperative opioid use (aOR: 1.53), osteoarthritis (aOR: 1.45), fibromyalgia (aOR: 1.26), and age ≥ 70 (aOR: 1.15). Minimally invasive and unilateral SI joint fusion were associated with reduced risk. Kaplan-Meier analysis showed increased lumbar fusion risk beyond 1250 days post-SI joint fusion.ConclusionsSI joint fusion significantly increases the risk of subsequent lumbar fusion in patients with LDD, particularly following open or bilateral procedures. These findings emphasize the need for thorough preoperative risk assessment and patient counseling regarding potential long-term lumbar effects. Future research should investigate clinical outcomes and biomechanical mechanisms underlying stress redistribution after SI joint fusion.