椎骨整形術之生物力學研究

Abstract

經皮椎骨整型術為一種治療因骨質疏鬆症引起的椎骨壓迫性骨折之手術方法。手術目的為使用骨水泥補強椎骨骨折之處，可增進椎骨之穩定度並回復其強度。椎骨整形術雖能有效治療病患疼痛，但相關之併發症的發生仍會對患者造成不便。主要併發症為骨水泥溢流、鄰近節椎骨骨折與椎骨再骨折。併發症的發生不僅影響患者的日常生活，對併發症的治療也會對醫療資源造成負擔。本論文之研究目的為探討椎骨整型手術之併發症的發生機制，並提出有效的預防方法，以增進椎骨整型手術用於治療壓迫性椎骨骨折之長期效益。 本論文之鄰近節椎骨發生新骨折之研究中，發現新骨折發生的原因可能為強度較弱的骨質與前彎動作。使脊椎維持正常的姿態和減少過重之負載可能為椎骨發生鄰近節椎骨骨折的最佳策略。本論文之預防性椎骨整型術之研究中，顯示具骨質疏鬆症的椎骨若其位置在身體前彎力矩的支點之處，預防性地灌注骨水泥，可避免身體的重心向前位移，並防止鄰近節椎骨產生新骨折。本論文之骨水泥溢流發生機制研究中，建議術前使用斷層掃瞄檢測椎骨型態，分析椎骨表面細微之裂縫與椎體靜脈尺寸。手術過程中若能避免使骨水泥接觸椎骨裂縫與椎體靜脈位置，就可以有效地降低骨水泥發生溢流的機會。本論文之椎骨發生再骨折之研究中，發現海綿骨不均勻的變形可能是造成椎骨發生再骨折的原因。新形手術策略若能使椎骨在受疲勞負載下，內部與椎骨後側有均勻的變形，可以避免椎骨在接受骨水泥治療後發生再骨折。 本論文以豬隻與人體椎骨進行體外實驗，並以生物力學之觀點，對椎骨整型術之主要併發症做一完整的系統分析。本論文的研究成果可提供醫事人員在手術施行策略上參考準則，以降低併發症發生的機會。期許本論文之研究成果能提升椎骨整型手術之長期效益，並使患者有更好的康復情形。

Percutaneous vertebroplasty is one of surgical treatments for osteoporotic vertebral compressive fracture. During the surgery, bone cement is injected into the fractured vertebrae to recover its stability and strength. Although patients are quickly relieved of pain, the complications of vertebroplasty, including cement leakage and vertebral failure at the adjacent and the augmented level, could be devastating. The treatments for complications may increase medical expenditure. The objectives of this study are to investigate the mechanisms of vertebroplasty complications and to propose potential prevention strategies to improve the long term benefits of vertebroplasty. In the study of adjacent vertebral failure, we found the weak vertebra and flexion compression are the two risk factors for of adjacent vertebral failure. The results of this research suggest that; restoring the natural lordotic posture and reducing the magnitude of external loading seem to be the best strategies to prevent adjacent vertebral failure for an already weak vertebra. In the study of prophylactic vertebroplasty, it can be cautiously suggested that if the vertebra is osteoporotic and adjacent level is located at pivot of spinal column, the prophylactic augmentation may be an option to avoid anterior body shift effect and prevent the adjacent vertebral failure. In the study of bone cement leakage, we suggest that the integrity of vertebral structure should be examined before the operation of vertebroplasty. If surgeon could avoid bone cement infiltrating to the cortical defect and basivertebral vein, the risk of cement leakage could be minimized. In the study of augmented vertebral refracture, we found the failure mechanism of augmented vertebrae is the presence of fracture lines, which are induced by the uneven strain distribution within the vertebrae. Technique or strategy equalizing the strain distribution within the vertebrae and spinal column seems to be important in preventing the post surgery fracture. In this study, the biomechanical mechanism of vertebroplasty complications were systematically investigated using porcine and human cadaveric vertebrae. The strategies for complication reduction are suggested to increase the long term surgery efficacy on compression fracture recovery.