139 CORRELATION OF THE VOLUME OF INJECTED CEMENT USING CEMENT AUGMENTED PEDICLE SCREWS WITH THEIR PULLOUT STRENGTH. A CADAVER STUDY

Abstract

The radiological and biomechanical assessment using cement augmented cannulated pedicle screw (Biomet^®, Omega 21^®) and the correlation of the cement volume to the pullout strength needed for each screw

Cadaveric vertebrae of different lumbar levels were used. Through cannulated pedicle screw a definite volume of cement was applicated. The bone volume occupied by cement was assessed by means of segmentation after Computer Tomography. Biomechanical Pullout tests and statistical correlation analysis were then performed

The maximum pullout strength was 1361 N and the minimum pullout strength was 172 N (SD 331 N). The maximum cement volume was 5,29 cm3 and the minimum 1,02 cm3 (SD 1,159). The maximum cement diameter was 26,6 cm and the minimum cement diameter was 20,7 cm (SD 1,744). There is statistically significant correlation between the pullout strength and the injected cement volume (p< 0,05).

The cannulated pedicle screw was used for a better fixation in the vertebral body. The cement augmentation with this technique is easier and seems to be safer than cement augmentation of non cannulated screws. Pullout strength of the cannulated screws correlates positively with the cement volume. It is though not influenced either by the total vertebral volume or by the ratio cement volume to vertebral volume or by the maximum diameter of the cement drough