| Background: The incidence of osteosarcoma is less than1%, but is higher in theadolescent population. Osteosarcoma greatly threatens the health of children andadolescents. Treatment of malignant bone tumors is an integrated process.Currently,complete removal of the tumor by surgery as well as reconstruction of bone and jointfunction after surgery is the most common way. Limb salvage surgery developed rapidlyin the past20years. But sometimes due to restriction of anatomical structure, as theneurovascular bundle, conservative separations and excisions have to be taken. Otherexisting limb salvage techniques such as thermal-based ablation may damage theligaments and tendons adjacent to the tumor, cause joint instability, limited mobility, andbring difficulties to limb reconstruction after surgery.IRE is a new tumor ablation technology which based on non-thermal effect. By applyingspecific electric field and pulses to the tumor tissue, IRE can affect the microenvironmentof tumor cells and effectively ablate the target tumor. Meanwhike, IRE spares adjacentvital tissues due to non-thermal effect in the process of ablation. Therefore IRE may havesound prospect in the treatment of bone and soft tissue tumor. Purpose: One the one hand, we try to ablate normal rabbit AT by IRE and by RFAseperately and compare the ablation efficiency, regenerative capacity of tendon tisue andbiomechanical change of the AT between this two methods. On the other hand, we alsowant apply a series of IRE pulses in a normal femur model, and then determine theeffective ablation threshold of IRE in bone tissue, observe the regeneration and healingprocess of the target region and test biomechanical properties of the ablated bonesegments.Methods: The finite element method was used to simulate the electric field intensitydistribution when applying IRE ablation on normal tendon and femur. The effectiveablation thresholds of IRE on these two tissues were determined by the softwaresimulation combined with histopathological results. Aseries of methods, includingconventional staining, immunohistochemical staining, quantification of the effective flowarea by microvascular perfusion, X-ray examination, bone mineral density test,fluorescence-labeled bone mineralization observation, biomechanical testing ofAT andfemur, etc., were used to assess processes of cell regeneration, revascularization,biomechanical properties recovery of the AT and the bone tissue after IRE ablation.Results: In the experiment of AT ablation, thermal damage of tendon caused by RFAleaded to protein denaturation and tendon rupture on the third day after treatment. It isconfirmed that the tendon tissue could not regenerate after such damage. However, byusing1800V/cm and90pulses, IRE could effectively ablate the AT, meanwhile spare thescaffold of collagen fiber. Creeping substitution of tenoblasts were found in IRE ablatedregion. Effective microvascular blood flow as well as biomechanic properties of the ATdeclined early after IRE ablation, and gradually restored to normal control level within24weeks.In the experiment of bone ablation,1800V/cm and120pulses were sufficient to ablatedtarget bone segment. After IRE ablation, obvious osteoclasts, osteoblasts and other repairactivities were found within the treated region. Although the effective microvascularperfusion area in the bone marrow cavity and the biomechanical properties of the ablatedsegment declined in the early period post ablation, they gradually returned to normal levels as well as the regeneration and healing of the ablated bone tissue. All animals postIRE ablation had free range of motion and no tendon rupture or bone fructure wereobserved.Concusion: By using combination of specific parameters, IRE could effectively ablatenormal rabbit AT and bone tissue. IRE ablates tissue with non-thermal effect and couldspare normal collagen scaffold, blood vessels and other tissue framework. All theseadvantages contribute to the regeneration and restoration of IRE ablated tissues. Byintegrating such features, IRE may be an effective ablating method for bone and soft tissuetumors. |
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