Can Discharge Radiographs Predict Junctional Complications? A Decision Tree Analysis

Study Design: Retrospective cohort study. Objectives: To determine if standing pre-discharge radiographs can predict the development of junctional complications. Materials and methods: Adult spinal deformity patients who underwent fusion of the lumbar spine (>= 5 levels, LIV pelvis) were included. All patients underwent full-length standing radiographs before hospital discharge. Outcomes of interest included 2-year radiographic PJK and proximal junctional failure (PJF). Patients were stratified into 3 exclusive groups: No PJK, PJK, and PJF. Chi-square automatic interaction detection (CHAID) decision tree analysis was utilized to identify pre-discharge proximal junctional angle (PJA) thresholds associated with increased risk of PJK or PJF. Results: The 117 study patients had a mean age 65.8 +/- 8.5, BMI 27.2 +/- 4.9, PI-LL 23.3 +/- 17.4, TPA 27.2 +/- 11.5. Sample was stratified into 64 (54.7%) No PJK, 39 (33.3%) PJK, 14 (12.0%) PJF. No differences were detected between cohorts in discharge alignment, preop-discharge change, or offset from age-adjusted alignment targets (P > .005). Decision tree analysis showed that the first branch point depended on the UIV, as most patients with an UT UIV did not develop PJK or PJF (no PJK, 67.4%). For patients with an LT UIV, a second branch point occurred based on the Delta PJA. 89.5% of LT patients with a Delta PJA < 4.3(degrees) were free of radiographic PJK and PJF. The third branch point occurred based on the PJA at discharge. Thus, the highest risk group was comprised of Delta PJA >= 4.3 degrees and PJA > 15.5(degrees), as 57.1% of developed PJF and 28.6% PJK. Conclusion: Most patients with a lower thoracic UIV, preop-discharge Delta PJA >= 4.3(degrees), and discharge PJA > 15.5(degrees )develop PJF.