Do Spinoplevic Alignment Measures Obtained from Intraop CT Correlate with Postop Standing Xrays/EOS for Deformity Patients?

Introduction: We sought to understand if intraoperative spinopelvic alignment parameters when the patient is prone in the intraoperative CT scanner correlate with postoperative measurements from standing upright long cassette Xrays/EOS imaging.

Methods: Intraoperative alignment parameters were measured for patients after instrumentation in the prone position using intraoperative CT thoracolumbar scout views. The same parameters were measured on postoperative upright standing long cassette Xrays within one week after surgery and at 2-12 months postop using long cassette x-rays/EOS imaging. Alignment parameters intraop (prone) and postop (standing) were compared using linear regression and t-tests.

Results: A total of 17 patients (76.5% female, mean age 67.5 years) with spinal deformity due to varying etiology who had intraoperative prone position CT imaging and postoperative upright  standing long cassette x-rays/EOS imaging were evaluated. Pelvic incidence-lumbar lordosis mismatch (PI-LL) was similar prone (9.3° +/- 12.1°) versus standing postop within one week (10.2° +/- 10.0°), (p=0.81) and standing at 1-12 months (13.0° +/- 9.7°), (p=0.36). Lumbar lordosis (LL) was similar in the prone position (47.6° +/- 10.2°) relative to the immediate postop standing after surgery (47.4° +/- 12.1°) (p=0.941) and at 1-12 months follow up (48.7° +/- 11.2°), (p=0.796). L1 pelvic angle (L1PA) was comparable in prone position (9.8° +/- 8.0°) versus immediate postop standing (12.3° +/- 8.9°), (p=0.41), and at 1-12 months postop standing (15.5° +8.4°), (p=0.07).

Conclusion : Alignment parameters obtained from intraoperative prone CT imaging are similar to postoperative standing radiographs/EOS x-rays. Intraoperative CT imaging could inform surgeons in real time of the magnitude of PI-LL correction they have achieved.