Finite Element Analysis Of Bone Cement To Strengthen The Minimally Invasive Pedicle Screw Under Different Conditions Of Osteoporosis

Objective: Using the finite element method evaluation the Percutaneous LongU-shaped hollow pedicle screw (PLU-SHPS) stability under different conditions ofosteoporosis and the stability of the PLU-SHPS whether improved by bone cement tostrengthen. For thoracolumbar fracture patients with different osteoporotic degrees onthe choice of surgical approach providing relevant biomechanical basis in the clinicalwork.Methods: Using Amira3D visualization software read L1segment CT scan data，thethickness is1mm at DICOM format and form the outline of L1. Then imported intoSolidworks software, through the assignment of L1material properties, theestablishment of normal bone, mild to moderate and severe osteoporosis L1finiteelement model. Simulated PLU-SHPS screwing surgery at mild to moderate andsevere osteoporosis L1finite element model. Then strengthen PLU-SHPS by bonecement. We conduct axial pull-out strength tests for the establishment five finiteelement models. Then analysis axial pull-out force of12nodes at PLU-SHPS and fivemodel stress map.Results: Normal bone, mild to moderate osteoporosis, mild to moderate osteoporosisby bone cement to strengthen, severe osteoporosis, severe osteoporosis by bonecement to strengthen its maximum axial pullout force were:184.3±7.7N,134.3±5.0N,179.9±4.4N,84.4±4.1N,120.6±4.3N. Its statistical analysis show，therewere significant difference (P <0.000) between the normal bone and mild to moderate osteoporosis group and significant difference between the normal bone group andsevere osteoporosis group (P <0.000), A significant difference (P <0.000) betweenmild to moderate osteoporosis group and mild to moderate osteoporosis by bonecement to strengthen group, between severe osteoporosis group and severeosteoporosis by bone cement to strengthen group had significant differences (P<0.000), There were no significant difference (P>0.05) between the normal bonegroup and mild to moderate osteoporosis by bone cement to strengthen group,butbetween the normal group and severe osteoporosis by bone cement to strengthengroup had significantly different (P <0.000).Conclusion: No matter what conditions osteoporosis, PLU-SHPS after bone cementto strengthen can significantly improve their fixed effects. In mild to moderateosteoporosis conditions, its axial pull-out force has no significant difference betweenthe PLU-SHPS by bone cement to strengthen and normal bone, But in severeosteoporosis conditions, its axial pull-out force between the PLU-SHPS by bonecement to strengthen and normal bone has significant differences. That is, in mild tomoderate osteoporosis condition, bone cement to strengthen can achieve normal bonefixation strength of PLU-SHPS, The conditions under severe osteoporosis, even if weuse bone cement to strengthen can not reach normal bone fixation strength ofPLU-SHPS. During the PLU-SHPS pulled out, the stress concentration at the end ofthe PLU-SHPS, which consistent with the pedicle screw tail often breakable in ourclinical work.