مقاومت در برابر فرسایش میله مدولار
Abstract
1-INTRODUCTION
2-METHODS
3-RESULTS AND DISCUSSION
4-CONCLUSION
Acknowledgments
Appendix
References
Abstract
The modular neck hip prostheses mechanical failure can have several causes, separated or combined such as fretting, corrosion, wear and fatigue. Corrosion mechanism is overcome by specific heat treatment. The fatigue mechanism occurrence is delayed by forging process coupled with finishing process such as shot penning. The breakage of the modular neck becomes mainly related to fretting issues. This is firstly due to the amplitudes of micro-movements of a mismatched geometric tolerance. The effect of contact condition on the fretting behaviour should also be put in relationship with to the used material performances. This study aims to highlight the effect of design parameters on the modular stem fretting resistance. The overall analysis of the results from the design of experiments carried out have shown that a trade-off should to be found between parameters since their variation could be beneficial for fretting wear resistance while becoming unfavorable for fretting fatigue, according to the evaluation criteria.
INTRODUCTION
It has been observed that the assembly method [1] ( by hand or by impact† ) as well as the force magnitude [2], direction [3] and location [4], used to compact a modular implant could influence its fretting behavior. Viceconti [5], [6] highlights the influence of the design on the stem/neck junction fretting behavior. It has been shown that a thinner stem diameter reduce the wear by following the neck displacement through elastic deformation. This limits relative microdisplacements then decreases fretting. In addition, an oblong section has been identified as the optimal geometry that minimized the mechanical stress for the same material volume. Otherwise, the stem diameter reduction leads to limit micro-motion. Surface roughness can be used to control the stick and slip zone within the effective contact area. Kretzer’s work [7] shows that increase surface roughness tends to decrease the salted-out particles quantity. However care must be taken not to produce a notch effect that occurs when roughness is not adequately controlled. This will increase the risk of surface cracking and generate some relatively large size debris. However roughness increases the contact pressure then augments the stress level underneath.