[Stability of pedicle screws. 2: Maximum pullout force with reference to bone density].

Maximum pullout strength of pedicle screws in osteoporotic cadaver spines are tested. Bone mineral density was measured before by two noninvasive methods (QCT, DRA). Pullout direction was axial to screw axis. 210 N to 920 N were reached from D1-S1. There is a high correlation between bone mineral density and pullout strength (r = 0, 8-0.9). Augmentation of osteoporotic pedicles with bone cement increases screw stability nearly to that one of non-osteoporotic spines.