Abstract
The influence of the intravertebral length of vertebral screws on their pull out strength.
64 Cadaveric vertebrae of different lumbar levels were used. By means of Computer Tomography the length of the screw in the bone was assessed. The ratio screw length in bone to the longest possible screw in bone was built. Biomechanical Pullout tests and statistical correlation analysis were then performed
The maximum pullout strength was 1602 N and the minimum pullout strength was 96,4 N (SD 356,9 N). The maximum ratio of the inserted screw was 95,9% and the minimum was 58,8% (SD 0,7%). There is no statistically significant correlation between the ratio of the inserted screw and the pullout strength needed. Moreover, there is a statistically significant correlation between bone mass density and pullout strength (p< 0,05).
The fixation of pedicle screws is better in a non osteoporotic vertebral body. Pullout strength and bone mass density correlate significantly whereas there is no correlation between the insertion length of the screw and the pullout strength under the condition that the insertion ratio is greater than 58,8 %. Factors such as insertion angle of the screw need to be evaluated, and new techniques for pedicle screw fixation in osteoporotic vertebrae need to be developed
Correspondence should be addressed to Anastasia C. Tilentzoglou MD, General Secretary of the Board of Directors of HAOST, 20 A. Fleming Str. (N.Filothei), Gr. 15123 Maroussi, Athens Greece. E-mail: info@eexot.gr
