Proximal junctional failure amongst 167 patients undergoing thoracolumbar fusion for adult spinal deformity

Introduction: Proximal junctional failure (PJF) is a severe form of junctional disease with high morbidity. Analyzing patient-related and surgical factors associated with PJF will inform preoperative patient selection, intraoperative decision making, and postoperative monitoring.

Methods: Patients who underwent thoracolumbar fusion with pelvic fixation for adult coronal and sagittal spinal deformity were retrospectively reviewed from 2014 – 2021 at the University of Pennsylvania. Clinical, demographic, surgical, and spinopelvic parameters were extracted to study development of PJF. PJF was defined as instability at the UIV causing neurologic deficit, fracture at UIV or UIV +1, screw pullout, and >20 degree increase in the proximal junctional angle (PJA). Data was analyzed using wilcoxon rank sum and chi square analysis for continuous and categorical variables, respectively.

Results: 167 patients (65.2 +/- 9.4 yrs, 69.3% female, 90.1% white) were identified with median 2-year follow-up (IQR 1.3-3.2). 21 (12.6%) patients developed PJF. 12 patients with PJF (57.1%) required extension of fusion. There was no difference in clinical and demographic variables including age, race, gender, smoking status, BMI, and height. >2 posterior column osteotomies (PCOs) was associated with higher rates of PJF (p = 0.03). Use of hooks, cement at UIV +1, and construct ending in the upper or lower thoracic spine was not associated with PJF. Patients with PJF had higher postoperative T1-slope (34.1 vs 28.2 degrees, p = 0.0001), which was not present on preoperative XR (27.6 vs 29.2 degrees, p 0.3). Patients with PJF had larger PJAs (21.8 vs 4.3 degrees, p 1.01*10-10) and PI-LL mismatch (9.8 vs 2.6 degrees, p = 0.09) with less lumbar lordosis (-45.5 vs -52.6 degrees, p = 0.01).

Conclusion : PJF following spinal deformity causes high rates of reoperation. Higher post-operative T1-slope may shift compressive loads to the anterior spinal column increasing risk of PJF development.