Platzierung von Pedikelschrauben mit einer mechanischen Zielhilfe im Vergleich zur konventionellen Methode - erste klinische Ergebnisse

Abstract

This report evaluates a mechanical aiming device (MAD) designed to increase accuracy in pedicle screw placement. 14 patients underwent thoracic and lumbar spine instrumentation with the MAD, 83 patients with conventional technique. Patients’ charts were reviewed to assess neurologic outcomes. Postoperative CT scans were used to evaluate screw position. Pedicle widths also were recorded. Screw diameters then were related to the according pedicle widths. No patient showed new neurologic complications related to screws. In thoracic spine 3 of 24 screws (12,5 %) were placed strictly intrapedicular by the MAD, with conventional technique 16 of 70 screws (22,9 %) (P > 0.05). Descriptive statistics by box-plots showed less fluctuation of screw positions by the MAD. In lumbar spine 25 of 32 screws (78,1 %) placed by the MAD were strictly intrapedicular, 200 of 248 screws (80,6 %) with conventional technique (P > 0.05). Descriptive statistics showed similar results. Thoracic pedicles in the MAD-group were significantly smaller than those of the conventional group. There was no significant difference in lumbar pedicle widths. The analyses of screw diameters and the according pedicle widths showed a ratio of > 100 % for parts of the thoracic spine instrumented with the MAD. At first sight - similar clinical results and statistically equal screw misplacement rates - the MAD shows no advantage. Taking into account pedicle widths and screw diameters there has been disadvantageous diameter/width-ratios for the MAD in the thoracic spine. Despite that the MAD produced a statistically non-significant misplacement rate. For this reason there can be drawn the conclusion that the MAD was able to place screws in thoracic spine more accurately than conventional technique. For there was no statistically significant difference in lumbar misplacement rates and pedicle widths the MAD remains without benefit in the lumbar spine.