髖關節術後骨質密度變化之電腦模擬分析

髖關節莖鬆動是目前人工髖關節長期植入後失敗最主要的現象，而以生物力學的考量因素來說，應力遮蔽效應是導致髖關節術後骨質流失並引發髖關節莖鬆動最重要的原因之一，由於術後髖關節莖周圍骨質所承受的應力和應變與術前正常狀態不同，在長期的作用下會促使骨質產生重建的現象，股骨近端的骨質會因而產生流失使髖關節莖無法穩定固定於骨髓腔中而導致最後手術的失敗。本研究利用已量化的數學模式描述骨質重建現象，配合影像處理、電腦輔助設計及有限元素分析法等技術於電腦中模擬人工髖關節長期植入後骨質密度的變化。電腦模擬結果顯示術後一段時間股骨內側近端骨質有變鬆之趨勢，而遠端則有變密的現象，與臨床骨質變化的結果吻合。故整合電腦斷層掃描、CAD系統以及有限元素分析法，能有效的模擬出髖關節植入後骨質變化的趨勢，此項技術加以修正、改進，日後應可作為術前臨床評估長期骨質流失的工具。
One of the recognized long-term failures of total hip replacement is the stress shielding effect. This effect is based on biomechanical point and is one of the factors that induce the bone remodeling and cause the loosening of the stem. The purpose of this study was to develop a computer simulation procedure to predict long-term bone remodeling process after total hip replacement. Imaging processing (CT), CAD system and finite element method were integrated to combine with the quantitative bone remodeling mathematical model. The results of the computer simulation showed that the bone density became sparse in the proximal region around the femoral stem and increased in the distal portion. This finding was consistent with the clinical observations. With the integration of CT, CAD system and finite element method, it is possible for the patient to be evaluated for the long-term bone remodeling process prior to the surgery of total hip replacement.