Abstract:

Objective　To evaluate the long-term in vivo biomechanical effects of a newly developed biphasic calcium composite bone cement (geneX®)with a negative surface charge augmentation of pedicle screw.　Methods　Bilateral pedicles of lumbar vertebrae (L1~5) of 6 female sheep were ?xed with pedicle screws. One pedicle of each vertebral body was treated with a screw augmented with either geneX®（geneX® group) or PMMA (PMMA group) and the contralateral pedicle was treated with a screw without any augmentation (control group). Three months later, the sheep were killed and biomechanical tests, micro-CT analysis and histological observation were conducted on the isolated specimen vertebrae.　Results　Both the axial and vertical stabilities of the pedicle screws in geneX® group were signi?cantly enhanced compared with those in the control group (P<0.05). Micro-CT reconstruction and analysis showed that there were more bone trabeculae around the screws in geneX®　group compared with those in control group and PMMA group (P<0.05), and the bone trabeculae were signi?cantly denser than those in control group (P<0.05). Histological observation showed that geneX® was completely degraded and bone trabeculae around the screws in geneX® group were more and denser than that in the control group. Bone trabeculae held the screws tightly without any interspaces between screw and bone, which formed strong bonding between bone and screw.  Conclusions　geneX® cement augmentation of the pedicle screw increase the strength of screw-bone interface, geneX® cement augmentation of the pedicle screw may be a viable clinical option for the augmentation of pedicle screw fixation.

Key words: Pedicle screw, Biomechanical testing, Augmentation