Three-dimensional EOS Analysis of Apical Vertebral Rotation in Adolescent Idiopathic Scoliosis

Apical vertebral rotation (AVR) is increasingly recognized as one of the important radiographic parameters in adolescent idiopathic scoliosis (AIS). EOS enables us to precisely measure AVR by 3-dimensional reconstruction. The objective of the present study was to describe the postoperative correction and the long-term follow-up of AVR in posterior spinal fusion with direct vertebral rotation and elucidate the factors that affected the correction.

We retrospectively reviewed 153 consecutive posterior spinal fusion surgeries for AIS performed between 2009 and 2012. Among them, 55 patients who fulfilled the study inclusion criteria with complete preoperative, immediate postoperative, and last follow-up (>1 y) EOS images were included in the present study. EOS 3-dimentional reconstructions were undertaken for each patient. Postoperative AVR correction and the loss of correction were calculated.

Preoperative AVR of the major curve averaged 19 degrees (SD=7 degrees), and AVR on immediate postoperative images averaged 9 degrees (SD=6 degrees, P<0.001). AVR at final follow-up averaged 11 degrees (SD=6 degrees, P=0.06). Postoperative correction was larger in all-screw construct than in hybrid construct (55% vs. 36%, P=0.03).

The present study is the first study to measure AVR in a large population of AIS patients using EOS 3-dimensional reconstruction. We report the correction magnitude was significantly affected by the construct.

Level IV-therapeutic study (case series).