Alendronate treatment improves bone-pedicle screw interface fixation in posterior lateral spine fusion: an experimental study in a porcine model.

The bone-screw interface has been indicated as the weak link in pedicle screw spine fixation. Bisphosphonate treatment may have the effect of improving bone-screw interface fixation in spine fusion by inhibiting bone resorption. An experimental study was conducted using a porcine model to evaluate the influence of alendronate treatment on bone-pedicle screw interface fixation. Eleven pigs in the treatment group received alendronate 10 mg/day orally for three months postoperatively. The other 11 pigs served as a control group. Posterior lateral fusion with the CD Horizon pedicle screw system was performed with autograft on the lumbar spine on all animals. Biomechanical torsion test and histomorphometric parameters of screw fixation were evaluated three months after the operation. The maximum torque and initial angular stiffness of the treatment group was higher than that of the control group, but there was no statistical significance. The bone-screw contact surface was 23.3 +/- 10% for the treatment group and 9.8 +/- 5.9% for the control group (P < 0.01). This study indicated that alendronate treatment increased bone purchase of stainless steel screw surfaces.