醫用超音波輔助骨水泥硬化與放熱行為之研究

Abstract

聚甲基丙烯酸甲酯骨水泥是一種被廣泛運用於骨科手術中的骨水泥，通常被用作固定植入的人工假體，有時也作為骨頭的人工替代物填入骨裂與空隙中。在原料充分混合後，骨水泥會依據情況使用不同的方式填塞致所需部位。有時為了減小侵入性，手術上會使用針筒將骨水泥注射至指定部位並等待其固化。然而，在等待的過程中，未固化的骨水泥很可能流竄至四周，造成嚴重程度不等的併發症。 醫療用超音波因為具有加熱與增快物質傳遞的功能，期望可以運用在以下的研究中，達到加速骨水泥的固化的效果，並加以控制骨水泥固化的時間與位置。實驗結果顯示：在開放系統中，商用Simplex P骨水泥固化時間在超音波輔助下由14分鐘縮短至5分鐘。另外，超音波在通過高密度組織（例如：骨頭）後，仍具有顯著的輔助作用，固化時間得以縮短至6分鐘。並且隨著超音波參數不同，固化曲線出現了雙峰與平頂現象。 同時，研究發現當施加的強度增加時，超音波的空蝕現象除了加速骨水泥的固化外，亦會使骨水泥中的孔洞數量與大小增加。施加超音波對固化後骨水泥的強度影響也因骨水泥流動性不同而有程度上的影響。當超音波瓦數增加至4瓦時，高流動性Simplex P骨水泥的降伏強度會由原本的96 MPa下降至65MPa。

Acrylic-based bone cements have always been an important role in orthopedic surgeries. It has been widely applied to anchor artificial implants as well as filling bone voids and cracks. Mostly, the cements are either hand-kneaded or injected into the desired location during their working phases. But one of the problems related to injection is that cement leakages may occur after injection since cements usually possess low viscosities during injection. These leakages could lead to complications such as spinal compressions and blood vessels thermal damage. With the ability to generate heat and accelerate mass transfer, medical ultrasound was applied to speed up the polymerization reaction of the bone cements in the present study. Results showed that with the aid of ultrasound, the setting time of commercial Simplex P bone cement could be shortened from 14 min to 5 min. Even after the attenuation through hard tissues, ultrasound still showed a remarkable influence by shortening the setting time to 6min. Two-peak phenomenon and plateaued curves were also observed depending on the ultrasound operation parameters. When the operating intensities increased, the cavitation effect of ultrasound also increased the pores’ sizes and amounts of the bone cements. This resulted in the decrement of yield strengths of Simplex P bone cements from 96 MPa to 65 MPa when the operation intensity was increased to 4 W.