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|Title: ||保留髖關節置換手術之生物力學研究;The Biomechanical Investigations for Preserving Hip System Replacement|
|Issue Date: ||2015-09-23 14:46:56 (UTC+8)|
;Total hip replacement (THR) is the most common treatment modality in hip osteoarthritis. Despite improvements in shape, material, and coating for hip stem, both stress shielding and aseptic loosening have been the major drawbacks of stemmed hip arthroplasty. Some non-stemmed systems were developed to avoid rasping off the intramedullary canal and evacuating the bone marrow due to stem insertion. At present, the non-stemmed design resulted in cup loosening and central bar fracturing in clinically because it was insufficient in the restriction.
In this study, many cup systems with minimal removal of the healthy neck were investigated to evaluate their biomechanical effects on the proximal femur and implants. The finite-element models of one intact, stemmed, resurfacing, cylinder, parallel, cross and nail femora were developed. The resurfacing and cylinder were selected as the representative of the ready-made implants. The parallel, cross and nail systems were selected as the representative of the custom-made implants. The stress distribution and interface micromotion were selected as the comparison indices. The biomechanical experiment were using cylinder, parallel and cross models to compare stability on the cup design and two screw constructions. The finite element analysis results showed that both stress distribution of all non-stemmed femora are consistently more similar to the intact femur than the stemmed one. Around the proximal femur, the stem definitely induces the stress-shielding phenomenon. The custom-made system with the anatomy-shaped cup can make intimate contact with the neck cortex and reduce the bone-cup micromotion and the implant stress. Comparatively, the reamed femoral head provides weaker support to the resurfacing cup causing higher interfacial micromotion. All the screws of the non-stemmed systems were highly stressed to serve as the potential for the failure of plastic yielding or fatigue cracking. The biomechanical experiment results showed that the stiffness of the custom-made cup and assisted screw with the cortical bone were better than the contrapositions.
In conclusion, the reserved femoral neck could act as the load-transferring medium from the acetabular cup, femoral neck to the diaphysial bone, thus depressing the stress-shielding effect below the neck region. If the hip-cup construct can be definitely stabilized, the non-stemmed design could be an alternative of hip arthroplasty for the younger or the specific patients with the disease limited only to the femoral head.
|Appears in Collections:||[機械工程研究所] 博碩士論文|
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