Introduction: Recent improvements with adult spinal deformity (ASD) surgery techniques have expanded to include minimally invasive surgery (MIS). Risk factors for pseudarthrosis development in MIS-TLIF development have not been studied extensively
Methods: Patients undergoing MIS were stratified into groups based on undergoing TLIF (T) or not (NT). Descriptive analyses and means comparison tests identified differences in baseline parameters. Multivariate logistic regression analyses determined significant predictors for development of pseudoarthrosis. Established weights were generated for predictive variables via back-step logistic regression for a risk score to predict development of pseudoarthrosis. Risk score was then validated via Receiver Operating Characteristic (ROC) curve method analysis. Categories via conditional inference tree (CIT) analysis-derived thresholds were tested for thresholds correlating to high risk.
Results: 465 patients included (59.9±14.7yrs, 27.3±5.3kg/m2, CCI: 1.63±1.6, FI: 3.12±1.65), with 34.4% (n=160) underwent TLIF. Cohort mean baseline SVA was 15.45±34.40mm, PI-LL 1.41±12.17°, and PT 16.24±8.80°. There were no differences in baseline age, gender, BMI, or baseline deformity between groups. A predictive risk score for pseudoarthrosis was developed with the following preoperative variables: age, frailty, history of diabetes, osteoporosis, depression, ASA grade, baseline L4-S1, and baseline T1PA. Using ROC, this predictive risk score generated an AUC of 0.87. Following CIT machine learning, thresholds for the Risk Score were derived: >5 No Risk (NoR), 3-5 Low Risk (LowR), 2-3 Moderate Risk (ModR), and < 2 High Risk (HighR). The rates of pseudoarthrosis for each category were: NoR – 0%; LowR - 1.6%; ModR – 9.3%; HighR – 24.3%. TLIF patients had overall the following pseudoarthrosis rates according to Risk Score: 5.9% NoR, 9% LowR, 2.7% ModR, 1.9% HighR. TLIF patients in HighR had 2.3 times lower risk with surgical prophylaxis (OR: -2.27 [1.79, 2.31] p=.004). Additionally, the use of BMP-2 lowered the risk significantly in those in HighR (p=.032).
Conclusion : Our study developed a pseudarthrosis risk score for TLIF patients. In those with high risk, surgical prophylaxis and BMP-2 demonstrated positive effects in patient outcomes, thus further enhancing justification for their use.
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