gms | German Medical Science

Objective: Minimally invasive spine surgery (MISS) for percutaneous pedicle screw insertion reduces soft tissue trauma, blood loss and postoperative pain. However, the benefit of MISS in combination with spinal navigation largely remains unknown because common imaging solutions for spinal navigation, such as 3D C-arm fluoroscopy, are hampered by a limited scan volume and susceptible to artefacts, particularly in multilevel MISS requiring the use of percutaneous screw extenders. Therefore, we investigated the applicability, precision and screw accessibility in multilevel MISS with intraoperative computed tomography (CT)-based spinal navigation.

Methods: After attachment of the navigation tracking device to a spinous process or the iliac crest, a first intraoperative CT scan with automatic co-registration was performed to allow navigated, percutaneous and guide-wire assisted pedicle screw implantation with screw extenders. Following implantation but before rod fixation and with in-situ screw extenders, a second intraoperative screw assessment CT scan was performed to permit immediate screw repositioning, if required. Intraoperative workflow, screw accuracy according to Gertzbein and Robbins and screw accessibility were reviewed and analyzed by an independent observer.

Results: Between 2015 and 2016, 19 patients (12 female, 7 male; median age 66 years, range 36 – 86) underwent multilevel MISS with screw extenders and intraoperative CT-based spinal navigation. The indications for surgery were trauma (47%), degenerative disease (21%), tumors (16%) and infections (16%). A total of 170 pedicle screws were implanted. The median number of instrumented segments was 5 (range 1-10). Intraoperative CT-based screw assessment was possible for each screw despite in-situ screw extenders. Based on this assessment, 3 screws required navigated repositioning due to lateral (n=2) and medial (n=1) pedicle breaches >4mm. The overall screw accuracy was determined at 97.6%.

Conclusion: Intraoperative CT-based spinal navigation for multilevel MISS with screw extenders is generally feasible and ensures high pedicle screw accuracy rates with the possibility of simple and safe navigated screw repositioning despite in-situ screw extenders, which improves workflow by allowing immediate screw revision before rod reduction and fixation.