Augmentation Of Absorbable Calcium Phosphate Cement For The Enhancement Of Screw: An In Vivo Biomechanical And Histological Study

Objective: To observe biomechanical and histological dynamic change of cancellous screws with calcium phosphate cement (CPC) to provide evidence for its u. se in clinic.Methods: Cancellous screws were implanted in the distal of femur and tibia of 8 mongrels to make living animal pull-out models. The screws were augmented with or without calcium phosphate cement respectively. The animals were sacrificed at 2,4,6and 8 weeks after surgery to test the maximum axial pull-out strength(Fmax, N) ,and then the specimens taken from the bone-screw interface to be investigated the histological changes after fixing,decalcificating and dyeing.Results: The maximum axial pull-out strength(Fmax, N) of screws augmented with CPC increased along with the post-operation time, and reach high at 8 weeks postoperatively. And the differences between the augmented group and the non-augmented groups were significant on statistics. The interface between bone and CPC was closely fitted, and the implanted CPC was replaced by new bone gradually. But the bone-screw interface remained a layer of fibrous tissue in the controlled group.Conclusion: When the screws ware augmented with CPC, the in vivo stability can be strengthened and increased along with the time.