適用於L5-S1前側路椎體融合術之可變形椎間籠設計

Abstract

背景簡介：側路前腰椎融合手術為目前臨床醫師較新穎之手術路徑選擇，多份臨床報告顯示此手術能有效改善病人症狀，在術後骨融合率及併發症比率方面，皆與其他路徑腰椎融合手術相比無顯著性差異；但是此手術方法在手術時間及術中血量流失有明顯地下降，進而促進醫療成本的降低。然而，此手術於L5-S1節有一限制，因L5-S1椎間盤兩側，有骨盆包覆而阻擋手術路徑。微創手術日漸流行，已被證實有效降低術中血量流失及住院天數。欲打破以上限制，針對L5-S1側路前腰椎融合手術發展一款專門的新型微創手術器械是有必要性的。 目的：本研究針對L5-S1側路前腰椎融合手術擬開發一款具備植入轉向功能之手術器械，以避開於手術路徑的骨盆，進而將植入物植入椎間盤位置。此外，為了恢復椎體間高度及椎間盤之穩定性，本研究並開發一款同時具備高度及水平擴張功能之可變形椎間籠。 方法：根據上述需求設計出多款手術器械及椎間籠並經臨床醫師評估後持續進行改良修正，使用有限元素法針對設計成果進行靜態結構分析，評估機構強度足以承受脊柱所施予軸向附載與否，選定最佳設計進行加工製作原型，並利用假體模型進行手術模擬，測試機構整體操作便利性。 結果：我們將機構原形最終版本進行有限元分析，機構足以承受2000牛頓軸向附載，且在機構最薄弱處安全係數仍大於2，並且將加工成品進行假體植入模擬成果，驗證此機構能確實閃避骨盆結構對稱植入L5-S1椎間盤位置，並能垂直與水平撐開，達到穩定椎節的目的。 結論：本研究成功開發出一款適用於L5-S1微創側路前腰椎融合手術且達成上述功能需求之椎間籠及其配合手術器械，具備高度擴張恢復及維持椎體間高度、水平擴張功能增加椎間籠放置後的穩定性、並植入轉向避開兩側骨盆將椎間籠植入椎間盤位置。經由有限元分析模擬得知此機構強度足夠承受人體脊柱所施予軸向附載，並能順利植入假體模型。就目前所知市面上無類似產品，相信本研究在未來手術應用上具備相當開創性及新穎性。

Background: Oblique lumber interbody fusion (OLIF) is an innovative selection of surgery path for clinical surgeons. Clinical reports have shown that this procedure can improve multiple symptoms of patient effectively. In postoperative bone fusion and complication, the results of this procedure is similar to the paths of other lumbar interbody fusion, but at the benefit of less surgery time and blood loss. However, this procedure in the L5-S1 section remains a surgical challenge because of the blocking of surgery path by the pelvis. In order to overcome the restrictions, there is a need to develop a minimally invasive surgical instrument specifically for L5-S1 oblique lumbar interbody fusion. Objective: To develop a surgical device for L5-S1 OLIF surgery with the function of controlling the implant direction to avoid the pelvis blocking in the surgery path. In addition, in order to restore the intervertebral disc height and stability, this device should be able to expand vertically and horizontally after implantation. Methods: Four prototypes that fulfill the above requirements were developed. The feasibility of all the designs was examined and subsequent modification were undergone. After the mechanism was confirmed, Finite Element (FE) simulation was used to confirm if the design meet the clinical biomechanical requirement. The final version of the device was physically manufactured for the simulation of the surgery procedure with a lumbar phantom to test the operational convenience and feasibility. Result: In finite element analysis, the result demonstrated the final version version could withstand 2000 N axial loading. The version four was physically manufactured and tested with a phantom. It showed this device can rotate, and expand vertically and horizontally after the implantation. Conclusion: We designed a device that is suitable for the L5-S1 minimally invasive oblique lumbar interbody fusion (MIS-OLIF). This design can be expanded vertically with the restoration of the disc height, expanded horizontally to increase the disc stability and changed the direction of implantation simultaneously. To the best of our knowledge, there is no similar products on the current market. We believe that this study has great novelty and potential in the future surgical application.