| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 107 === Femurs are the thickest bones in human bodies. When people stand and move,
our femurs suffer not only axial load but also the bending load because of their
anatomical shapes and the muscles that pulling around. Nowadays locking plates are
the most popular treatments for the destruction of a femur. After the occurrence of the
bone fracture, the main support of the body weight when the patients stand and walk
all relies on the plate at the early stage of recovery. However if there is any
shortcoming of the plate design or any lack knowledge of the usage of the plates, the
plates will be broken under a fatigue load after frequently walking or excessively
using. This may result in failure of the treatment and another operation will be needed
once again.
There are two parts in this study. The first one is about the weak point of a plate.
We use finite element analysis to infer the weakest part of a plate and then we validate
the result by biomechanical tests. In the second part, we investigate the effect of the
different screw working length only by biomechanical tests.
From the result of finite element analysis, the stress concentration is on the
screw-hole edges and most of the maximum stress are near the fracture gap. It finds
out that the weak point of the plate is the screw-hole edges at the thinnest part of the
plate. In mechanical tests, although there is a great stress at the thinnest part of the
plate, the maximum stress is at the screw-hole near the middle diaphysis. This is a
result of a larger lever arm and the inferior bending of the bone. In aspect of the
working length, an longer working length has a good effect at the low fracture model,
but goes worse at a higher fracture. This comes to a result of a transform of loading.
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