Insertional torque of the lumbar pedicle screw during surgery

The purposes of this study were to determine if the intraoperative insertional torque of pedicle screws correlates with the degree of osteoporosis and if insertional torque can be used as a predictor of screw loosening and clinical results in elderly patients. Pedicle screw fixation was performed in 25 patients. Their mean age at the time of surgery was 72.2 years (range 65-79 years). The mean follow-up period was 2.8 years (range 1.0-4.8 years). The insertional torque of the pedicle screws was measured using a Kannon-type torque wrench with a special connector. In the present study, 136 screws were evaluated. The mean insertional torque was 12.2 +/- 5.0 kgf x cm. A negative relation was found between insertional torque and the grade of osteoporosis. Roentgenograms showed the radiolucency of 18 screws in eight patients. Radiolucency appeared as early as 6 months postoperatively. However, there was no significant relation between insertional torque and the presence of screw loosening. Furthermore, there was no significant difference in the clinical results between patients with low insertional torque and those with high insertional torque. This study demonstrated that intraoperative insertional torque is not an objective predictor of screw loosening or clinical results.