Risk factors of proximal junctional angle increase after selective posterior thoracolumbar/lumbar fusion in patients with adolescent idiopathic scoliosis.

PURPOSE: To analyze risk factors for an increase in proximal junctional angle (PJA) after posterior selective thoracolumbar/lumbar (TL/L) curve fusion in patients with adolescent idiopathic scoliosis (AIS).

METHODS: AIS patients that underwent selective posterior TL/L curve fusion with a minimum of 2-year follow-up were identified. Demographic and radiographic data were collected before surgery, at first erect after surgery and at final follow-up. Multiple linear regression analysis was performed to determine the relation of PJA changes during follow-up and eight potential risk factors, including locations of upper instrumented vertebra (UIV), locations of lower instrumented vertebra (LIV), length of fusion segments, types of pedicle screw alignment, lumbar lordosis (LL) at first erect after surgery, LL changes before and after surgery, sagittal vertical axis (SVA) at first erect after surgery and SVA changes before and after surgery.

RESULTS: A total of 41 patients were included in this study. There were 37 female and 4 male with a mean age of 14.7 years at surgery. PJA was increased from 5.5° immediately after surgery to 10.8° at the last follow-up (P < 0.0001). Regression analysis showed that locations of LIV, LL changes before and after surgery and SVA changes before and after surgery were risk factors for increased PJA. Pearson correlation test showed that postoperative LIV inclination was significantly correlated with PJA changes.

CONCLUSIONS: Location of LIV above or equal to L3, higher postoperative LL and deteriorative negative SVA with surgery were potential risk factors for increased PJA during follow-up. Postoperative LIV inclination more than 5ºmight be also an indicator for an increase in PJA.