J Neurol Surg A Cent Eur Neurosurg 2012; 73 - P070
DOI: 10.1055/s-0032-1316272

Validation and Accuracy of Intraoperative CT Scan Using the Philips Allura Xper FD20 Angiography Suite for Assessment of Free-Hand Pedicle Screw Placement

A. R. Fathi 1, E. Nevzati 1, S. Marbacher 1, M. Gugliotta 1, L. Remonda 1, J. Fandino 1
  • 1Department of Neurosurgery, Kantonsspital Aarau, Switzerland

Introduction: The purpose of this study was to evaluate the accuracy and feasibility of intraoperative computed tomography (iCT) imaging using the intraoperative Philips Allura Xper FD20 angiography suite for assessment of free-hand pedicle screw placement accuracy in posterior thoracic and lumbar spine fusion.

Methods: Patients underwent conventional fluoroscopy-guided posterior pedicle screw fixation. iCT scan (Philips, Allura Xper FD20) was performed before wound closure. In case of pedicle screw misplacement, iCT scan was repeated to evaluate proper replacement. All patients had postoperative conventional CT scan. Accuracy of pedicle screw placement was assessed as follows: minor (≤2.0 mm), moderate (2.1 to 4 mm or <1 screw thread diameter), and severe displacement (>4 mm or >1 screw diameter). iCT image quality and comparison with conventional CT scan was assessed by an independent radiologist.

Results: In this study 28 consecutive patients were included (16 females, 12 males) mean age 60.8 years (19 to 76 years). A total of 192 pedicle screws were assessed (66 thoracic and 126 lumbar). Intraoperative screw replacement was needed for 11 screws (5.7%). Subsequent iCT revealed correct screw position without the need for a second replacement in these patients. On first postoperative day a CT scan was performed in all patients. All screws were correctly replaced intraoperatively, thus no patient underwent a second procedure for correction of screw position (92% accuracy level 1, 8% accuracy level 2) iCT scan quality was assessed as sufficient in all cases and assessment of screw placement revealed a high correlation (r = 0.92, p<0.05) with postoperative CT scan.

Conclusions: iCT scan is feasible and reliable to assess pedicle screw position in spine fusion surgery. Intraoperative verification of spine fusion instrumentation using iCT prevents patients to undergo additional surgery for correction of implant position.