Identifying Predictors of Failed Back Surgery Syndrome Following Lumbar Spine Surgery

Study Design. Retrospective cohort study from a tertiary academic medical center. Objective. To build a prognostic machine learning model to predict 1-year FBSS incidence following lumbar spine surgery Summary of Background Data. A minority of patients who undergo degenerative lumbar spine surgery will have persistent postoperative pain, characterized as “Failed Back Surgery Syndrome” (FBSS). Adequate preoperative identification of patients at risk of having an undesirable outcome after surgery is an essential part of a spine surgeon’s workflow. While several studies have proposed mechanisms and risk factors for FBSS, no studies have developed a prognostic machine learning model to quantify and functionalize predictions. Methods. A cohort of lumbar fusion and lumbar decompression surgeries was queried from a tertiary academic medical center from 2002-2022. Patient and operative characteristics were systematically extracted for each surgery. Several machine learning algorithms were employed and optimized to predict FBSS occurrence within 1 year of surgery. SHAP feature importance values were computed for the top performing model. Results. A total of 10,128 unique lumbar decompression surgeries and 2,890 unique lumbar fusion surgeries were included. The Random Forest model had the highest performance of tested models (AUROC of 0.715 for lumbar decompression, 0.701 for lumbar fusion). For lumbar decompression, the top three predictors of FBSS were absence of microdiscectomy, lack of preoperative immunosuppressant usage, and preoperative benzodiazepine usage. For lumbar fusion, prior FBSS diagnosis, lack of preoperative immunosuppressant usage, and operating room duration were the most important predictors. Other key variables spanned several domains including preoperative medication usage, patient demographics, and operative indications and characteristics. Conclusion. This study demonstrates the successful creation of a prognostic machine learning model for prediction of FBSS within 1 year postoperatively. These models, after external validation, have the potential to be instrumental aspects of a spine surgeon’s workflow. Level of Evidence. 3