- 學位論文
應用於脊椎背根神經節電刺激系統的可回收固定器之研發
Development of a Retrievable Implantable Anchor for Dorsal Root Ganglion Stimulation
摘要
根據歷年來的統計，越來越多人受到神經病變的折磨，例如帕金森氏症、癲癇、類風溼關節炎、下背痛等慢性神經疾病。因為神經受損通常無法藉由藥物根治，因此病患必須尋求額外的治療途徑。電刺激系統是一項已經被證明能夠阻絕神經痛覺傳遞的技術，例如下背痛就可以利用電刺激來治療，只是治療並非一勞永逸，病人必須定期回醫院進行手術。而長期植入式的電刺激系統能解決此一問題，已漸漸成為慢性疼痛病患的選擇。 背根神經節(Dorsal root ganglion，DRG)是位於脊椎神經中重要的神經節點，同時掌管身體與內臟間的神經傳遞，也包括慢性疼痛患者受損的痛覺神經元。因此刺激DRG能夠有效地紓緩不正常的痛覺傳遞。雖然DRG在脊椎中的位置可以預測，但其周圍的結構並不適合固定。一般的植入式神經電刺激系統包含主要的電極線、內部放電器、與外部控制器。本篇研究設計且製造了一款類傘架型式的固定器，安裝於電極線前端隨著微創手術埋入病患體中並固定於DRG附近。固定器的材質是具有生物相容性且機械性質良好的聚醚醚酮(polyetheretherketone，PEEK)。固定器的尺寸必須夠小才能經由微創導管手術進入人體，輸送過程中固定器的傘狀結構保持彎曲狀態，電極線到達DRG附近後再將外套抽出使傘狀固定器自行張開，讓傘骨提供足夠的固定能力。將來若是電刺激系統失去療效，也能利用固定器本身的可活動機構來減少回收時對病患所造成的損傷。 本篇研究中證明了相較於以往的長期植入式電極，傘狀固定器提供了更強的固定能力。實驗設計將固定器埋入明膠與豬肉中進行抗拉測試，結果顯示固定器的抗拉能力優於一般的電極線。目前DRG電刺激手術須仰賴外科醫生的技術，將軟性電極線纏繞於複雜的脊椎骨中來提供固定能力。未來擬將固定器與植入式電極線結合，成為一套全新的DRG神經電刺激系統，屆時醫生便可以把電極線經由簡單的路徑直接固定在病患的DRG附近進行治療。
並列摘要
Statistics have shown that more and more people suffered from chronic neurological disorders, such as Parkinson’s disease, epilepsy, rheumatoid arthritis, and other pain caused by dysfunction of nerves. Since neuropathic pain is caused by damage of somatosensory nervous system and seldom cured via pharmacological treatment, patients have to look for other therapies. Electrical stimulation on specific nerves has been proven therapeutic in several chronic disorders. However, stimulation therapy on sufferers of chronic diseases is not once and for all. Discomforts will come back just in a period of time. To avoid the injury caused by stimulation surgeries repeatedly, permanently implantable medical electrical stimulation systems are usually used in sufferers. Dorsal root ganglion (DRG) is an important neuronal structure lying along the vertebral column by the spine. DRG can influence both somatic and visceral activities, and contains the primary sensory neurons that represent the key flow of sensory information, including the feelings of pain. As a result, stimulating specific DRG can relieve chronic pain condition caused by spinal injuries. Though DRG which consists of cell bodies along the dorsal roots of spinal nerves is a convenient target for stimulation because of its expectable location disposed external to the epidural space, the weak fixation ability makes it difficult to stimulate fluently. To overcome this predicament, a three-dimensional anchor is devised to provide fixation mechanism for the stimulation system. A permanently implantable stimulation system comprises a stimulating lead, an implantable pulse generator (IPG), and an external controller for patients. The designed anchor is attached to the tip of the lead, inhibiting the unexpected movement and dislodgement of the electrodes. The umbrella-like anchor is made of polyetheretherketone (PEEK), a kind of biocompatible polymer with strong mechanical properties. The dimensions of the anchor must be small enough to be suitable for minimally invasive surgery. The beams on the anchor are initially folded inward alongside the lead while fitted into and constraint by the lumen of an introducer implanted by surgeons. After inserting out of the introducer, the beams then spread out, transforming back to their original state to stick in subcutaneous tissues. The lead is consequently positioned and fixed in muscle tissues near the target DRG. Furthermore, the anchor also possesses the ability to be retreated back form the tissues once the dysfunction of stimulation occurs. In this thesis, umbrella-like anchor has been proven its advantages of fixation mechanism over prior permanently implantable medical electrical stimulation systems. In-vitro experiment is conducted, in which a lead with an anchor is delivered into gelatin and pork spine respectively to simulate the real situation of implantation. The results show that the anchor provides great fixation ability than normal lead. In the future, the anchor will be developed to combine with DRG stimulation systems adequate for minimally invasive surgery. The lead can be implanted near DRG through straight paths instead of complicated routes across the spinal vertebra, making it conveniently performed by the doctors and reducing the damage caused by the implanting surgery at the same time.