gms | German Medical Science

Objective: Navigated instrumentation of atlantoaxial instability is challenged by complex anatomy, instable pathology and unreliable preoperative registration techniques. Different intraoperative image acquisition techniques enabling autoregistration of C1 and C2 promise sufficient accuracy while maintaining practicability and safety for navigated instrumentation of the atlantoaxial segment. The aim of this study was to compare accuracy and reliability of an intraoperative computer tomography (iCT) system with cone beam computed tomography (CBCT) systems in the surgical treatment of instable C1/C2 pathologies.

Methods: From July 2014 to November 2018, 47 patients with instable atlantoaxial pathologies received standardized posterior fixation using C2-pedicle screws and C1-lateral mass/translaminar screws. All screws were implanted using spinal navigation techniques with either iCT or CBCT including autoregistration and a control scan after instrumentation. The primary outcome parameter was accuracy of screw positioning two independent observers retrospectively graded. Surgical time and number of postoperative screw revisions were secondary outcome parameters.

Results: 47 patients were retrospectively analysed. All patients presented with instable C1/2 pathologies including 42 fractures, 2 tumoral destruction of C1/2 and 1 spinal tuberculosis. In 29 patients iCT and in 18 patients CBCT techniques were used for image acquisition (Zeego:9/O-ARM:9). No demographic differences were found between patient groups (p>0.05). In the iCT group a total number of 118 screws were placed with 97.5% correctly inserted and 2.5% with minor breach, without misplacement. In the CBCT group 78 screws were placed with 97.4% correctly inserted and 1.3% with minor breach. 1.3% of screws were misplaced. There was no statistical difference in screw accuracy. Surgery using iCT demanded a significantly longer surgical time (169.0 min; SD±34.0) compared to CBCT (119.8 min; SD±28.1; p<00.1). Both imaging techniques allowed sufficient evaluation of screw accuracy with only one patient requiring secondary screw revision in the CBCT group (2% of all patients; 5% of CBCT patients).

Conclusion: iCT and CBCT allow reliable, safe and accurate navigation for posterior instrumentation of atlantoaxial instability without significant differences between different systems. Both imaging techniques allow reliable intraoperative evaluation of screw placement potentially reducing the need for secondary revision surgery.