Background: Sacroiliac joint (SIJ) dysfunction is implicated in 15% to 25% of cases of chronic lower back pain, a leading cause of disability globally. Sacroiliac joint fusion (SIJF) has become an increasingly utilized treatment for refractory SIJ pain, with its adoption projected to rise significantly. While SIJF can alleviate symptoms, many patients develop contralateral SIJ pathology requiring subsequent surgery. Understanding the incidence, timing, and risk factors for bilateral SIJF is critical for improving patient outcomes, managing expectation, and guiding surgical decision-making. This study aimed to (1) determine the incidence of bilateral SIJF, (2) assess the timing between initial ipsilateral and subsequent contralateral SIJF, (3) identify risk factors associated with progression to contralateral SIJF, and (4) compare the timing to contralateral SIJF between patients presenting with unilateral versus bilateral SIJ dysfunction.

Methods: A retrospective review was conducted identifying 323 consecutive SIJFs performed between 2011 and 2024 at an integrated health care system. Three clinical cohorts were identified based on progression to SIJF. Cohort 1 included patients who underwent unilateral SIJF only. Cohort 2 patients developed contralateral SIJ pain following initial SIJF, while Cohort 3 patients had bilateral SIJ pain prior to initial SIJF. Demographics and prior spine surgical details were collected and included in multivariate analysis. Kaplan-Meier survival curves were used to evaluate the timing between SIJFs. Comparisons between groups were established with student’s t -test and chi-square analysis. Statistical significance was defined as p < .05.