由骨質疏鬆所導致股骨及脊椎骨骨折之研究

Abstract

骨質疏鬆所引起的骨折是骨科醫師執行手術的大宗。當面對這一群患者的手術時，往往會遭遇到許多困難及挑戰。在這幾年的研究當中，我們嘗試著選擇了幾項或許可以改進的部分加以研究。其結果在第二至第六章來呈現。本論文包括兩大部份: 第一部分嘗試著解決近端股骨轉子間骨折困難固定的問題以在手術當中如何改善螺釘定位的問題；第二部分嘗試改進椎體成型術的一些手術步驟，希望能減少骨水泥溢流的機會。 人體屍骨是用來作為生物力學研究上最好的材料。因為它的性質與構造，符合解剖學上的真實性。但是由於人體屍骨非常的昂貴而且取之不易，基於生物力學測試上的需要，在第二章中我們我們嘗試著利用豬隻的股骨進行生物力學的測試。但是實驗結果顯示，其生物力學的反應與我們所預期的骨質疏鬆症之反應截然不同。其原因可能是豬隻的股骨強度太高所致。從這個實驗，我們可得到一些結論: 即豬股骨不宜拿來做骨鬆症的生物力學模擬實驗。由此推論應該還可以再進一步推廣至其他研究範圍，諸如脊椎骨以及四肢骨折之骨鬆症生物力學研究，還是使用具有骨質疏鬆特質的材料為宜。 由於骨質疏鬆之故，螺釘與股骨頭接合力減少，因此轉子間骨折之固定有時容易失敗。為了增加螺釘的固定效果，在第三章中，我們改良了股骨滑動螺釘的設計，把螺釘的直徑加大，以容許橫向互鎖式螺絲穿過而可以固定在股骨頸內側。如此可以增加螺釘對近端骨片固定的效果。由於第二章研究的結果，我們知道豬股骨並不適用於骨鬆症的研究，而且人體屍骨獲得不易。為了實驗的需要，我們採用低強度的人造假骨來模擬骨鬆症股骨轉子間的骨折。經實驗結果顯示，如果在股骨滑動螺釘上加上橫向互鎖式螺絲，可以明顯的加強螺釘固定效果。因此如果臨床上有機會採用本法，或許能減少手術失敗的機率。 在股骨轉子間骨折手術時，螺釘尖端應該放置於股骨頭中心位置，而且越靠近軟骨下 (subchondral bone)越好。如此螺釘能與較硬的骨質結合，手術成功的機會較高。反之如果螺釘尖端未能打在股骨頭的中心點，則螺釘位移或穿出於股骨頭的機會增加。在美國每一年會有二十五萬人次近端股骨骨折的新病例發生。施行這種手術會有一定的失敗比例，如果失敗率以百分之五來計算，那麼ㄧ年就可能產生數千例手術失敗的個案。推究手術失敗的因素，最多還是醫師未能將螺釘打在理想的位置。因此如果有好的辦法，能增加螺釘放置的準確性，那麼手術失敗的個案就可以顯著的減少。為了以上的目的，在第四章中，我們設計了一種新的骨髓內瞄準裝置，希望能增加螺釘放置的準確度。在兩年的期間裡面，我們以六十個患者作為樣本，分兩組進行手術。ㄧ組以傳統方法利用骨折床復位及手術。第二組以新設計的骨髓內瞄準器 (intramedullary guide)協助螺釘的定位。結果發現，如果以骨髓內瞄準器輔助手術定位，可以顯著的增加螺釘定位的準確性。由於螺釘可以被打在較佳的位置，因此可以預期螺釘位移及手術失敗的機會也可以大幅度的降低。以骨髓內瞄準器輔助手術定位，也可以大幅降低手術中X-光透視的時間，這樣對於降低醫事人員以及患者的幅射劑量都很有幫助。以骨髓內瞄準器輔助手術定位，手術的時間也可以大幅度的縮短，這樣對於減低老年患者手術的併發症也有所幫助。 第五章的研究與椎體成型術有關。由於人口老化的關係，人類的骨質會隨著年紀的增長而逐漸的流失。而影響所及，脊椎骨骨折已成為人類最常見的骨折之一。目前常用的手術方法是椎體成型術(vertebroplasty)。骨水泥在低黏度高壓力的情況下注入椎體內。但是這種手術方式常會有骨水泥溢流的情形發生。如果溢流至心肺系統，有可能造成心肺衰竭;如果溢流至脊椎腔內則可能造成神經損傷。本篇研究係利用迷你手術(mini invasive open surgery)方式將骨水泥的黏度提高至黏塑性情況下送入椎體內。臨床上 6 個患者術後疼痛的情形均大幅度的減低，骨水泥也沒有溢流的情況發生。我們進一步行生物力學實驗，以證實此手術方法有效。實驗採用七個人體胸椎行壓迫性骨折以及黏塑性椎體成型術(viscoplastic bone cement vertebroplasty)。由實驗數據顯示，骨水泥以黏塑性狀態下灌注至椎體內，可以有效的增強椎體強度。因此臨床上所觀察到手術後患者的疼痛症狀得到緩解，可以由生物力學實驗的結果加以說明。由試樣的切片觀察，骨水泥與椎體骨小樑之間有很好的結合，因此黏塑性骨水泥椎體成型術可說是一種安全經濟有效的手術方式。或許可以成為傳統椎體成型術或汽球擴張椎體成型術的另一種可能替代手術方案。 總之，我們嘗試著去改良一些在骨質疏鬆症手術時所遭遇到的一些問題，希望本篇的研究結果對於後續臨床上的工作以及未來的研究會有一些的幫忙。

During the past few years, several existing problems in the treatment of osteoporotic fractures were selected for study. The results are presented in chapter two to six. This essay consists of two major parts. For the first part, the task of fixation failure and aiming problems for the treatment of proximal femoral fractures were studied. In the second part, we concentrated on improving the techniques of vertebroplasty to avoid cement leakage. For the biomechanical study of proximal femoral fractures, a proper specimen is needed for testing. Because the source of cadaver specimens is scarce and the preservation of specimens is difficult.We tried to apply a porcine model to perform the mechanical test in the pilot study which is discussed in chapter 2. Unfortunately, the result was disappointing; the non-osteoporotic specimen is so tough that its performance is completely different than we had expected. So, it may not be appropriate to use non-porotic specimens to simulate the osteoporotic proximal femoral fractures. This conclusion may be expanded to other fields, such as spinal or skeletal biomechanical studies. Owing to osteoporosis, the internal fixation of proximal femoral intertrochanteric fractures can easily be failed. In order to strengthen the fixation effect in the surgery, in chapter 3 we modified the traditional Dynamic Hip Screw by increasing the diameter of the lag screw. The diameter of the lag screw is enlarged so that two transfixing screws are allowed to pass through it and be affixed to the femoral neck. We applied weak saw bone to simulate the osteoporotic proximal femoral fracture and fixation. The biomechanical results of this study showed that the strengthening effect of the modified lag screw can be significant. Because malposition of lag screw is one of the most important reasons of fixation failure, the increase in accuracy of the lag screw position is extremely important. Because the lag screw tip can be incorporated with the strong subchondral bone, and hence the chance of lag screw migration can be decreased. In order to increase the accuracy of surgery, in chapter 4, we have designed a new intramedullary guiding device. A clinical test was performed to validate the feasibility of using the guide. From the results of the study, the accuracy of the lag screw placement can be increased; so the expected fixation failure would be decreased. The fluoroscopy time can be decreased as well which is helpful for the patient and medical personnel. Other benefits of the technique are an increase in operation efficiency and a decrease in operation time as well. Vertebroplasty is commonly used in the treatment of unhealed painful vertebral fractures. The cement is injected into the fractured vertebra in low viscosity and high pressure, where cement leakage is common. Severe complications can result if cement leaks into the spinal canal and pulmonary area. To reduce the above complications, Kyphoplasty was developed; cement is injected at lower pressure and higher viscosity. However, the material cost of Kyphoplasty is high and there exists a risk of bone fragment extrusion into the spinal canal while the balloon is inflated. To avoid the above potential complications in chapter 5, vertebroplasty is performed with mini invasive open surgery. A small wound and a cavity is created at the vertebral body by a curate. When the cement is in the state of viscoplastisity, it is delivered into the cavity of the vertebral body and then tamped for compactness. We have successful experiences in 6 cases. Because cement is delivered in a high viscous state, the risk of leakage is extremely low and pain relief is excellent in all cases. To validate the biomechanical effectiveness of the above technique; we performed a biomechanical test in seven human cadaveric thoracic vertebrae. From the experimental data, the viscoplastic state bone cement vertebroplasty can restore the strength of a fractured vertebra. The restored strength can explain the clinical observed pain relief of the patient. From the macroscopic view of the sliced specimen, there was good bonding between bone cement and trabecular bone. In summary, we tried to improve the technique and solve some of the problems which are encountered in the treatment of osteoporotic proximal femoral fractures and spine compression fractures. We hope these works do help increase the efficacy of surgery and decrease complications.