Predictors of Sacroiliac Joint Intervention Following Lumbar Spine Fusion

Retrospective cohort study.

To identify the prevalence and predictors of sacroiliac (SI) joint fusion following lumbar fusion surgery.

Recurrent low back pain is common after lumbar fusion surgery, with SI joint dysfunction increasingly recognized as a significant factor. Lumbar fusion restricts spinal compensatory motion, increasing stress and movement in the SI joint, which can cause pain due to its extensive innervation. Identifying risk factors for SI joint dysfunction is critical for optimizing surgical treatment and postoperative outcomes.

The PearlDiver Mariner Database was queried for patients undergoing 1-5-level lumbar fusion between 2010 and 2023. Patients requiring subsequent SI fusions were identified. Demographics, comorbidities, and surgical characteristics were analyzed using univariate and multivariate logistic regression. Time intervals between lumbar fusion and SI fusion were assessed using Cox proportional hazard regression, with survival curves generated by Kaplan-Meier analysis.

Among 509,129 lumbar fusion patients, 0.7% underwent SI fusion. Female sex, greater fusion levels, segmental instrumentation, and autograft use predicted SI fusion. Prior SI injection was the strongest predictor of SI fusion, occurring on average 3.3 years after surgery.

This study highlights the significant prevalence of SI joint fusion following lumbar fusion. The risk increases with each additional level fused, as longer constructs and rigid instrumentation exacerbate stress on the SI joint, accelerating degeneration. Key risk factors include segmental instrumentation, female sex, and osteoarthritis, with patients requiring SI injections after the procedure having the highest odds of subsequently undergoing SI fusion. These findings offer practical guidance for surgical planning, patient counseling, and postoperative monitoring for SI joint dysfunction.