[Prospective screw misplacement analysis after conventional and navigated pedicle screw implantation]

[corrected] The aim of this prospective study was (1) to evaluate the accuracy of pedicle screw placement using Computer - Assisted Orthopedic - Surgery (CAOS) in comparison to conventionelly image intensifier controlled pedicle screw instrumentation, (2) to compare our results with data from literature and (3) report our experiences with this technique.

Between 11/00 and 11/01 sixteen patients planned for spine surgery were subsequently recruited. Pedicle screw instrumentation was done in each patient as well with computer aided surgery (CAOS, SurgiGate-System, Medivision, Stratec Medical, Swiss) as also with image intensifier control, allowing for intraindividual comparison. Evaluation of pedicle screw placement was carried out with postoperative computed tomography (CT) or magnetic resonance imaging (MRI).

33 of altogether 36 pedicle screws inserted with Computer-Assistance (CAOS) were correctly placed (91,7%), however only 17 of altogether 24 pedicle screws inserted under image intensifier control (70,8%). The difference of frequency of screw misplacement between Computer-aided and image intensifier controlled instrumentation was statistically significant (p<0.05; chi-square test).

Computer assisted surgery reduces significantly the misplacement rate of pedicle screws and remains for experienced spine surgeons an important support in the operative treatment of complex spinal deformities in future. Additionally it can be expected that Computer-Navigation will also spread out in the field of minimal-invasive spinal surgery, e.g. the kyphoplasty. The use of this technique supports beside the medical-technical knowledge an improved three-dimensional orientation in the education of spine surgeons.