Accuracy of computer-assisted pedicle screw placement - An in vivo computed tomography analysis

Study Design. A computer-assisted planning and visualization system (the Orthopaedic Surgery Planning System) was tested for pedicle screw insertion in vivo. Objectives. To evaluate the system's applicability for regular intraoperative use and its accuracy for pedicle screw placement in vivo. Summary of Background Data. Pedicle screw placement poses considerable anatomic and biomechanical risks. The reported rates of screw misplacement with conventional insertion techniques are unacceptably high. It previously has been shown in vitro that computer assistance offers the potential to decrease the number of screws perforating the pedicular cortex. Methods. The accuracy of 162 pedicle screws inserted with the Orthopaedic Surgery Planning System was assessed by means oi postoperative computed tomography evaluation. Reconstructions of the horizontal, frontal, and sagittal planes were analyzed. Cortex perforations were graded in steps of 2 mm. Results. The cortex was perforated in 2.7% of pedicles. Complete preoperative computed tomography scanning of the levels to be operated on is essential to allow for a precise image reconstruction. Initial difficulties in applying he system contribute to the malplacements. A learning curve for general handling of the Orthopaedic Surgery Planning System was observed. Conclusions. The system provides a safe and reproducible technique for pedicle screw insertion. Other applications in the field of spine surgery are under evaluation.