長骨骨髓內釘之設計與力學分析
Date Issued
2004
Date
2004
Author(s)
羅至倫
DOI
zh-TW
Abstract
Clinical reports have showed that the interlocking nailing system often fails in response to the highly concentrated stress and subsequent fatigue cracking, especially at first distal nail-holes and screws. The current study tried to develop a new interlocking nail to eliminate such a device-related problem. The new design was with thicken wall-thickness at the distal portion to increase the fatigue resistance of the distal nail-holes to the stress concentration, thus the fillet (chamfer) or enlargement of the nail-holes may be possible to facilitate the entrance of the locking screw. The stress interference at the intersections between the slots and nail-holes were also discarded by the rearrangement of the slots on the nail surface to keep away from the nail-hole edges. The self-evident advantages of the new design were to be validated by finite element analysis and biomechanical experiments.
For the finite element analysis, the mechanical influences of the muscular contractions on the femur-nail-screw construct were firstly evaluated to constitute the more physiologically reasonable loading condition. Then the parametric analysis of the design factors (e.g. nail-hole wall-thickness, slot location, nail-hole size, fillet at nail-hole edges) for the new interlocking nail was performed. The present study revealed that addition of the muscular contractions made the stress-distributing pattern of the femur-nail-screw construct more consistent with the reported studies. The predicted results of the finite-element study also supported the aforementioned postulations that the increase in distal nail-thickness, location arrangement of nail slots, and the fillet (chamfer) at the nail-hole edges significantly decrease the concentrated stress around nail-holes and screws.
In prior to biomechanical experiments, the fatigue behavior of the intruded nail at the distal portion was estimated by vertically compressing the medially inclined nail that was distally interlocked by the screw. In the current study, up to 400,000 cyclic compression ranging from 100 to 2000 N still made no any visible crack at the circumference of the nail-holes. Hence, the reported high failure rate at the distal nail-holes may be mainly attributed to the surface damage during the screw insertion rather than only the internal stressing by body weight. However, the shorter nail used in the tests may restrain the bending moment to the distal nail-holes and screw and thus protect them. Hence, the further works are worthy done to clarify the relations between the mechanical failure, surgical procedure, and experiment design.
Subjects
測試
肌肉力
長骨骨髓內釘
新設計
有限元素分析
製造
muscle force
test
new design
interlockihg nail
FEM analysis
manufacture
Type
thesis
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