ACCURACY OF COMPUTER-ASSISTED PEDICLE SCREW PLACEMENT - AN IN-VIVO COMPUTED-TOMOGRAPHY ANALYSIS

Study Design. A computer-assisted planning and visualization system (t he Orthopaedic Surgery Planning System) was tested for pedicle screw i nsertion in vivo. Objectives. To evaluate the system's applicability f or regular intraoperative use and its accuracy for pedicle screw place ment in vivo. Summary of Background Data. Pedicle screw placement pose s considerable anatomic and biomechanical risks. The reported rates of screw misplacement with conventional insertion techniques are unaccep tably high. It previously has been shown in vitro that computer assist ance offers the potential to decrease the number of screws perforating the pedicular cortex. Methods. The accuracy of 162 pedicle screws ins erted with the Orthopaedic Surgery Planning System was assessed by mea ns oi postoperative computed tomography evaluation. Reconstructions of the horizontal, frontal, and sagittal planes were analyzed. Cortex pe rforations were graded in steps of 2 mm. Results. The cortex was perfo rated in 2.7% of pedicles. Complete preoperative computed tomography s canning of the levels to be operated on is essential to allow for a pr ecise image reconstruction. Initial difficulties in applying he system contribute to the malplacements. A learning curve for general handlin g of the Orthopaedic Surgery Planning System was observed. Conclusions . The system provides a safe and reproducible technique for pedicle sc rew insertion. Other applications in the field of spine surgery are un der evaluation.