科研之友
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摘要
In clinical practice, cam-out failure at the recess-screwdriver interfaces may occur when tightening or removing a bone screw. For titanium-based periarticular fixation, the literature reports have revealed that cold welding at the plate-screw interfaces makes the screw recess especially prone to cam-out failure during screw removal. In this study, the effects of the four recess shapes (cross, hexagon, star, and crest), three torque value (0.8, 1.0, and 1.2N-m), and the three interfacial misfits (0.00, 0.05, and 0.10mm) on the cam-out failure were numerically evaluated. The free-rotation angle, torque-recess angle, slippage-resisting length, and interfacial stress distribution were defined and chosen as comparison indices for the twelve recess-misfit variations. The results revealed that the interfacial slippage, torque transfer, and stress distribution are highly related to both recess shape and interfacial misfit. The stresses of all recesses and screwdrivers consistently initiate at the contact sites. However, the recess profile significantly affects the stress propagation. The stress patterns of the recess and screwdriver are quite different between the cross-star and hexagon-crest groups. The cross-star group is superior to the hexagon-crest group in terms of the torque-recess angle and slippage-resisting length over. This makes the recess of the cross-star group less stressed than its counterpart. However, the volumes of the cross and the star screwdriver are more highly stressed than the hexagon due to the irregular shape and the thinner flange, respectively. The greater torque and misfit increase the performance difference between the four recess designs. In conclusion, the geometry of the cross and star groups provide the better performance of the screw recess in terms of torque-transferring efficiency and slippage-resisting ability. If the screwdriver material is properly strengthened and the stress-concentrating corners are modified, the cross and star groups would be the optimal designs that protects and extends the lifetime of both recess and reused screwdriver.
- 出版日期2013-3
- 单位长春大学; 中央民族大学
