- 學位論文
適用於早發性脊椎側彎自我調適生長桿之動物實驗驗證
In-Vivo Validation of a Self-Adaptive Growing Rod System for Early Onset Scoliosis
摘要
簡介：小兒早發性脊椎側彎(Early Onset Scoliosis)為10歲以下之孩童其脊椎側向彎曲或旋轉。此時期為孩童快速發育的重要階段，若不及早治療，骨骼將持續變形，使心肺功能發展受限。若是保守治療無效，則需要侵入式手術治療，治療方式是在病患體內植入生長桿，除了矯正側彎角度，並能讓脊椎保有生長的功能。生長桿可分為外力控制系統及生長導引系統兩類，外力控制生長桿能提供脊椎支撐力並保持其生長量，但缺點為需要定期侵入式延長手術，容易造成傷口感染以及孩童身心上的煎熬，磁控生長桿雖然可避免重複侵入式手術之苦，因其為新設計，機構複雜且臨床案例仍有發現併發症，整體成效如何尚未明確；生長導引生長桿優點為不須延長手術，藉由導引脊椎生長來矯正側彎，但缺點為脊椎生長量不如預期，且容易有控制側彎失敗的情形，臨床失敗率高。綜觀以上目前常見的生長桿系統問題，本研究已先初步設計出一款新型自我調適生長桿系統。 目的：本研究目的為驗證一款不須經過重複侵入式延長手術且能提供良好矯正效果與生長能力之自我調適生長桿系統。 材料與方法：本研究之自我調適生長桿系統其核心機構為可允許軸向延長之套筒連接器，其內部包含一組圓柱型棘齒與三角斜面的棘爪，搭配壓縮彈簧形成可隨著脊椎生長而單向延長的機構且能抵抗軸向壓力。於套筒上下端可另外連接桿件，使醫師能依照一般手術方法實施；為了增加穩定度，本系統加裝連接桿系統。在功能性測試方面，總共執行三次動物實驗。自我調適生長桿皆以醫療等級不鏽鋼材質製造，進行手術將其置入豬隻體內，於術後會給予豬隻良好照顧且定期拍攝植入部位的X光影像，追蹤觀察12週，並藉由量測影像中的Cobb Angle、生長桿延長量、單位椎骨高度(Vertebral Unit Height)以及更細部的椎間盤高度與椎骨高度，來評估自我調適生長桿是否會隨著脊椎生長而延長，以及植入節與非植入節間的生長情形。豬隻犧牲後，會取出自我調適生長桿作分析以及進一步採集豬隻血液與組織進行生化分析，評估其發炎反應。此外，於每次動物實驗前會對自我調適生長桿進行拉伸測試，量測每單位延長所需力量。 結果：於第一次動物實驗，因豬隻傷口嚴重感染，提早將其犧牲並取出植入物觀察，發現生長桿有輕易延長、連接處變形以及頭尾兩側的椎弓根螺釘有鬆脫情形，且於套筒內部出現黑色黏滑物質，但並無發現生長桿有損壞或是任何裂痕的現象；於第二及第三次動物實驗，先將改良後的生長桿做拉伸測試，得到每單位延長所需的力量分別為15.87及12.60牛頓。從X光影像的結果可以看出生長桿的延長量與植入節單位椎骨高度的總生長量大小相近，且植入活動節與非植入節的平均單位椎骨高度生長量也有相同的大小。於植入物取出分析部份，在第二次動物實驗中發現右側生長桿套筒與其尾部桿件連接處有螺絲鬆開的情形，但其他部位並無發現有損壞或是有任何裂痕的現象；而套筒內部皆有發現黑色黏滑物質。經過血液生化測試與組織切片染色分析，都並無發現顯著的生化病變。 結論：本研究成功將所研發之自我調適生長桿系統置入實驗豬隻體內，並驗證其在動物體內的功能與可行性。經過12週的觀察，自我調適生長桿系統能隨著脊椎的生長而延長，且安裝上自我調適生長桿並不會抑制脊椎的生長。此系統尚有不足處，仍須進一步修正及改良，並再進行測試與評估，日後將會成為一具有潛力及實用性的脊椎矯正植入物，以用來治療小兒早發性脊椎側彎，維持良好的矯正效果，減少患者重複手術開刀的需求。
並列摘要
Background. Early onset scoliosis (EOS) is a disabling condition commonly defined as the development of an abnormal spinal curve occurred in children before the age of 10. The deformity of spinal column restricts the development of cardiopulmonary function, and leads to the impairment of body growth. Invasive corrective spinal surgeries are often required for the children who ineffectively respond to conservative treatment. Surgical implantation such as spinal growing rod is used to constrain spine deformity and, at the same time, allow spine to growth. Two types of growing rod system were developed: the forced growing rod system and the growth guidance system. The forced growing rod systems constrain the spinal posture by the resistance of rigid rods. It requires periodical revision surgery as the children grow. The revision surgery increases the risk of complications such as wound infection, and causes significant impact on patients’ psychological stresses. Recently, the magnetically controlled growing rod was developed to avoid the revision surgery. However, the mechanism of this system is complicated and the complications are still found clinically. The revision surgery is not necessary for the growth guidance system. However, clinical complications such as insufficient spinal stability, spinal growth, and implant failure are frequently reported. Given the shortcomings and the disadvantages of the current systems, this study designed a novel self-adaptive growing rod system. Purpose. The aim of current study is to validate a novel self-adaptive growing rods system, which is able to maintain the spinal posture and to grow with spinal column without the revision surgery. Material and Method. The self-adaptive growing rod system allows a unidirectional extension. The growing rod is composed of an external tube, an inner cylindrical sleeve, a triangular ratcheted pawl, and a spring. The rod is able to be extended freely, but at the same time, to provide resistance against axial force. The minimally required force for the extension of the self-adaptive growing rods was determined before the in-vivo test. The growing rod is connected to the commercially available bone rod, crosslinks and screws, hence surgeons can follow the tradition surgical protocol for EOS. This study completed three in-vivo experiments. The self-adaptive growing rod system, manufactured with medical grade stainless steel material, was implanted and then followed for 12 weeks. After the implementation, the pigs were closely monitored for general well-being and x-rays were taken. Cobb angle, the elongation of rods, vertebral unit height (VUH), disc height and vertebral body height were measured via the radiographs. The integrity of the device and the blood biochemical and histology analysis were then examined after the sacrifice of pigs. Result. In the first test, the pig was sacrificed due to wound infection and the implants were retrieved after one week. The retrieved growing rods system revealed that the growing rods were slightly extended on both sides, connective rods were deformed, pedicle screws were loosen in both cranial and caudal sides. Observable gunk was found within the sleeve of the device causing slight clogging. Nevertheless, the integrity of the device was satisfactory without signs of implant failure and remained functional. In the second and the third tests, the modified versions were used. The tensile tests of modified rods showed a pull force of 15.9 and 12.6 N, respectively. The radiographs showed the elongation of growing rods is similar to the total VUH augmentation among the instrumented levels. In terms of the integrity of the device, the screw loosening was observed at the caudal connective rod in the right side during the second test. The other part of the device remained intact throughout the experiment. Observable gunk was found within the sleeve of the device. No significant lesions were found in the blood biochemical and histology analysis. Conclusion. The current study successfully implanted the self-adaptive growing rod system into pigs, and validated its functionality and feasibility with the in-vivo study. After 12 weeks follow-up, the self-adaptive growing rod system could be lengthened with spinal growth, and implantation of the self-adaptive growing rods system would not restrict spinal growth. It is acknowledged that the device in its current design may not meet the requirement of medical device regulation. Designs based on the experiences of this study can further be improved.