隨著老年人口的遽增骨質疏鬆問題已成為世界第二大流行病。骨質疏鬆使得骨折發生率增加，且多為不穩定性骨折。2018年光在亞洲就約有112萬案例髖部骨折，一年所需花費約950萬美元。台灣 邵崇榮與賴國安學者統計指出: 2002年髖關節骨折之粗發生率為每10 萬人中有643.7人發生，在所有髖部骨折的老人中轉子間骨折佔一半，且有50 ~ 60%屬於不穩定骨折。

動態式髖部骨螺釘(DHS)可提供穩定骨折較佳的治療方式，但無法將轉子間不穩定骨折中小轉子骨折碎片作有效固定，使得結構不穩定而發生cut-out及骨釘斷裂導致骨折癒合甚至於無法行走或死亡等併發症，因而增加患者及社會負擔。臨床上常見的一種骨釘失效的狀況，是骨釘與骨頭間介面無法承受固定強度而破壞而造成拔出的併發症，這使得骨折固定變得不穩固而造成骨折無法癒合。鋼絲雖常應用於外科手術，如：全人工關節置換、脊椎固定、膝關節修復，但多需倚靠臨床醫師經驗累積，來找到較佳的固定方式。

本研究目的為設計及發展鋼絲輔助DHS固定系統與其輔助器械來提供轉子間不穩定骨折(A2.1)之小轉子骨折碎片的固定，進而提升整體結構的穩定度，增加骨癒合及減少併發症發生。其特定目標包含：(1)探討DHS固定骨鬆A2.1骨折的生物力學特性，(2)發展三維鋼絲固定有限元素模型，(3)發展鋼絲固定技術以輔助DHS固定A2.1骨折並探討其生物力學效應，(4)測試不同鋼絲固定法輔助DHS固定A2.1骨折的結構剛性及降伏強度，(5)設計改良型鋼絲導引器械使鋼絲能繞過小轉子骨折碎片和(6)設計改良型DHS固定系統使鋼絲穩固的固定骨折。
本研究共分為兩個階段。第一階段：(1)使用有限元素法分析DHS固定骨鬆的A2.1骨折以分析骨折碎片的離散情形；(2)基於鋼絲材料為等向、均質且線性彈性的假設條件下，依據不同截面狀況建構不規則的鋼絲有限元素模型；(3)根據(1)分析結果來發展鋼絲固定技術並應用鋼絲有限元素模型來探討不同鋼絲固定法輔助DHS固定骨折的力學效應；(4) 使用萬能材料試驗機測試鋼絲固定法輔助DHS固定骨折的結構剛性及降伏強度。第二階段：(5)改良型Wirepasser的設計包含有兩個中空勾形結構能使鋼絲穿越及一組公母連接器，此連接器可使兩個中空勾形結構結合；(6)改良型的DHS固定系統有助於鋼絲固定，其零件包含有一個具溝槽的側板與輔助蓋板, 傳統的延遲骨釘及皮質骨骨釘所組成。
有限元素分析結果顯示在A2.1骨折中小轉子碎片會收到肌肉牽引方向朝向內側近端方向移動，根據這樣的趨勢發展出三個固定方式。並使用鋼絲有限元素模型可以成功地用於生物力學的探討，結果顯示三種固定方式均可以達到穩固的效果。在生物力學測試比較中sawbone 結果顯示有鋼絲輔助固定組別的最大承載荷重/剛性/能量均高於單純使用DHS固定，cadaver測試結果顯示在固定荷重下4種鋼絲固定方式均可提升結構剛性以減少位移。Cadaver在只使用DHS固定的疲勞測試結果發生cut-out符合臨床上的併發症。鋼絲輔助器械與鋼絲輔助DHS固定系統也都完成發展與其並使用於本研究的實驗中。
本研究指出經由鋼絲固定有限元素模擬分析的發展，有助於了解鋼絲固定的生物力學，提供鋼絲輔助DHS固定法作為臨床上治療A2.1骨折較穩定固定方式。小轉子碎片的固定在A2.1骨折固定是很重要的因素，而結合鋼絲輔助固定則可以達到輔助固定的效果以提升骨折結構穩定性。

Osteoporosis has become the second most common epidemics in the world due to the increase of elderly population. In 2000, International Osteoporosis Foundation (IOF) reported that among 9 million osteoporosis-related bone fractures worldwide, 1.6 million are hip fractures, 1.4 million are vertebral fractures and 1.7 million are forearm fractures.
In 2018, the total number of hip fractures in Asian countries was 1.12 million and the direct medical cost was USD 9.5 billion [1]. Although using dynamic hip screw(DHS) on stable intertrochanteric hip fracture fixation has been successful and led to fracture healing for the past 20 years, DHS fixation on unstable femur fractures(A2.1) has a failure rate exceeding 50% [2, 3], especially in osteoporotic patients. Bone screw uses for fracture fixation in orthopedic surgery and generally provide solid resistance against unidirectional axial loading forces. In clinical, one of the screw failures is break in the bone-screw interface and cause pullout result due to the weak of bone quality or large pro-drill hole. Screws are therefore at risk of adverse postoperative outcomes secondary to failure of bone fixation, especially in Osteoporosis patient. DHS alone could not provide the stable fixation in A2.1 unstable intertrochanteric fracture. Although the wire fixation is usually incorporated with orthopedic device to enhance the fixation, the methods of the wiring techniques still rely highly on the surgeon’s experiment.

The purpose of this research is to design and develop a wire reinforced DHS fixation system to provide a more stable fixation for lesser trochanter fragment on osteoporotic TypeA2.1 fracture in order to enhance bone healing and reduce the failure rate. More specifically, this research is aimed to:
(1) biomechanically investigate the DHS fixation on osteoporotic unstable intertrochanteric fracture ( fracture A2.1); (2) develop a 3-D finite element model of wire fixation; (3) develop wire fixation techniques for lesser trochanter fragment fixation; (4) biomechanically test the wire incorporated with DHS fixation system on fracture A2.1; (5) develop twinned wirepasser for passing wire around the lesser trochanter fragment; and (6) develop a wire incorporated DHS fixation system for A2.1 unstable fracture fixation with wire.

This research is divided into two phase. In the first stage: (1) finite element method (FEM) is used to analyze the displacement condition of bone fragments for A2.1 fracture with DHS fixation; (2) Develop 3-D FEM mesh model of wire which is tied on irregular surface of bone geometry. Wire is based on ideal physical property of wire with homogenous, isotropic and linear elasticity, 3-D 20-nodes solid elements(SOLID186) (3) based on the outcomes of (1), three different wiring techniques are proposed, and FEM is used to validate these techniques incorporated with DHS fixation on A2.1 fracture; (4) biomechanical property of wire incorporated with DHS fixation on sawbone and cadaver with A2.1 fracture is conducted through universal material machine. In second phase: (5) A twinned wirepasser is developed. The design consists of two cannulated hooks for passing wires and a connector to provide adjustable connection for these hooks; (6) An wire incorporated DHS is designed that contains a side plate with special shallow groove to house wire.

The results of FE analysis of DHS fixation on A2.1 fracture indicate that the lesser trochanter (LT) fragment is displaced toward the proximal and medial direction by ilipsoas muscle traction. Based upon the direction of fragment migration, this research has developed three wiring techniques. 3-D FEM model of wire has been successfully developed and applied to biomechanical investigation. The results of FE analysis of wire incorporated DHS fixation on A2.1 fracture shows that these three wiring techniques all provide stable fixation without high stress concentration. The results of biomechanical testing between sawbone indicate that the structure maximum load, stiffness and yielding strength have significantly increased when wire is incorporated with DHS fixation. In static biomechanical testing of cadaver femur, the stiffness was compared between five different wire fixation models and then a fatigue model was tested in cycle loading with DHS fixation. Wiring fixation shows enhanced stability in static test results, and the cut-out failure model in the fatigue test that was identical to the clinical failure model “cut-out”. The twinned wirepasser and wire incorporated DHS fixation system have also been developed.
Lesser trochanteric fragment fixation is a crucial concern in the stability of A2.1 unstable fracture, and the combination of a wiring technique with DHS is beneficial for achieving better stability.
Keywords: wire, dynamic hip screw, finite element method, unstable intertrochantic fracture

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