A prospective study on the use of intraoperative computed tomography (iCT) for image-guided placement of thoracic pedicle screws.

BACKGROUND

Placement of thoracic pedicle screws is a technically demanding procedure. The risk of thoracic pedicle breaches range from 6.5 to 41%. Current image guidance systems consist of computer based systems utilizing preoperative CT scans or 2D/3D intraoperative fluoroscopy.

OBJECTIVE

The aim of this prospective study was to evaluate the clinical feasibility and accuracy of a new intraoperative CT (iCT) based image guidance system for thoracic pedicle screw instrumentation.

METHODS

We prospectively studied the use of iCT for the first 43 consecutive cases for which thoracic pedicle screws were inserted as part of the instrumentation for spinal fusion between April 2008 and July 2011. In every case, a post-instrumentation intraoperative check CT was done before wound closure to assess accuracy of implant placement. Outcomes were analysed with regards to the incidence of pedicle wall violations detected on intraoperative check CT imaging, and the rate of immediate intraoperative revision of misplaced screws. Pedicle violations were graded according to an established classification system.

RESULTS

A total of 261 thoracic pedicle screws (T1-T12) were inserted in 43 patients (age range 13-83). Mean follow-up was 12 months. There were 7 (2.7%) pedicle violations detected on the intraoperative check CT. Out of the seven, three were grade I (< 2 mm), two were grade II (2-4 mm) and rest two were grade III (> 4 mm) violations. Only four of the screws (1.5%) that breached the pedicle wall by more than 2 mm were immediately revised before wound closure.

CONCLUSION

The iCT based spinal neuronavigation system allowed for highly safe and accurate placement (97.3%) of thoracic pedicle screws in our institution with no neurovascular injury reported.