| Summary: | 碩士 === 國立陽明大學 === 生物醫學工程學系 === 103 === Dynamic hip screw (DHS) is the normal treatment to femoral intertrochanteric fracture, especially in stable fracture. When using a standard barrel, however, lag screw may not slide and lose its main function if the barrel length is over the fracture site. Nevertheless, a shorter barrel increase the bending moment of lag screw because of the longer distance between the fracture site and the terminal of barrel. In order to keep the lag screw function and decrease the bending moment, we design a barrel which has 31 mm length. This study analyzed 38 mm, 31 mm, and 25 mm barrel by finite element under the hypothesis that while the barrel length over the fracture site and the barrel is approach to the fracture site, the DHS can provide a better stability than the shorter one.
In this study we simulated simple intertrochanteric fracture model using 38mm, 31mm, 25mm barrel length DHS and modified DHS under one reference load (stance phase of the gait cycle). Several different situations were analyzed, and we would discuss micromotion and θof fracture site. We also compared the stability between DHS and modified DHS.
This study shows that the 31 mm DHS barrel micromotion decreases 25.4 % than 25 mm DHS barrel and 31 mm modified DHS barrel micromotion decreases 17.2 % than 25 mm modified DHS barrel. On the other hand, θ decreases 18 % in 31 mm barrel than 25 mm barrel no matter using DHS or modified DHS. Using both DHS and modified DHS, the shorter distance between the terminal end of barrel and fracture site causes the shorter micromotion and smaller θthat shows a better stability on fracture site.
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