COMPARATIVE ANALYSIS FOR THREE FIXTURES OF PAUWELLS-II BY THE BIOMECHANICAL FINITE ELEMENT METHOD.

Little is known about why and how biomechanics govern the hypothesis that three-Lag-Screw (3LS) fixation is a preferred therapeutic technique. A series models of surgical internal-fixation for femoral neck fractures of Pauwells-II will be constructed by an innovative approach of finite element so as to determine the most stable fixation by comparison of their biomechanical performance. Seventeen sets of CT scanned femora were imported onto Mimics extracting 3D models; these specimens were transferred to Geomagic Studio for a simulative osteotomy and kyrtograph; then, they underwent UG to fit simulative solid models; three sorts of internal fixators were expressed virtually by Pro-Engineer. Processed by Hypermesh, all compartments were assembled onto three systems actually as "Dynamic hip screw (DHS), 3LS and DHS+LS". Eventually, numerical models of Finite Elemental Analysis (FEA) were exported to AnSys for solution. Three models for fixtures of Pauwells-II were established, validated and analyzed with the following findings: Femoral-shaft stress for c (3LS) is the least; Internal-fixator stress (MPa) for a (DHS) = 1 9 6. 9 7 > b (DHS + LS) = 8 8. 3 7 > c (3 LS) = 6 3. 8 1 ; Integral stress (MPa) for a (DHS) = 1 9 5. 3 5 > b (DHS + LS) = 8 6. 7 2 > c (3 LS) = 6 4. 6 0 ; displacement of femoral head (mm) for a (DHS) = 1. 0 6 8 > c (3 LS) = 1. 0 1 0 > b (DHS+LS) = 0.735; displacement of femoral shaft (mm) for c (3 LS) = 0. 7 1 4 > a (DHS) = 0. 5 3 3 > b (DHS+LS) = 0. 4 7 5 ; and displacement of fixators for c (3 LS) = 0. 9 8 2 > a (DHS) = 0. 9 7 3 > b (DHS + LS) = 0. 7 0 6. Mechanical comparisons for other femoral parks are insignificantly different, and these data can be abstracted as follows: the stress of 3LS-system was checked to be the least, and an interfragmentary displacement of DHS+LS assemblages was assessed to be the least". A 3LS-system should be recommended to clinically optimize a Pauwells-II facture; if treated by this therapeutic fixation, breakage of fixators or secondary fracture is supposed to occur rarely. The strength of this study is that it was performed by a computer-aided simulation, allowing for design of a preoperative strategy that could provide acute correction and decrease procedure time, without harming to humans or animals. [ABSTRACT FROM AUTHOR]