| 摘要: | 下顎骨為人體顏面骨中最容易破損的區域之一。近年來針對下顎骨節段性缺損使用重建骨板進行重建手術治療的應用越來越廣泛，該類手術以金屬骨板貼合斷裂區域與鎖入骨釘用來固定支撐，然而儘管金屬骨板有經過彎曲疲勞測試，但有不少病患在下顎復原時發生骨板斷裂或失效現象。重建骨板會先在術前根據患者模型初步彎折，在手術中進一步微調，以達到貼合患者的下顎骨輪廓。然而過去幾乎沒有文獻在分析彎折時產生的殘留應力及其影響，導致評估骨板耐久性時過於樂觀。
本研究由實驗取得Ti-Grade.4純鈦骨板拉伸性質，以沖壓骨板的殘留應力分析驗證骨板塑性分析的可行性。建立健康與不同缺損大小(35 mm和75 mm)的下顎骨模型，利用位移控制使骨板產生殘留應力，然後施加咬合肌力，以評估骨板有、無殘留應力對於下顎骨重建骨板系統的生物力學影響。此外，進一步探討有、無於鄰近缺損處植入骨釘與骨釘垂直或傾斜植入的差異。
研究結果顯示，實驗得到的材料真實應力-應變圖，與其他文獻相似。在沖壓骨板分析中，雖然不同軟體所得的骨板應力有差異，但是在沖頭壓到底與離開時殘留應力的分布趨勢相似。在下顎骨重建骨板系統中，重建的下顎骨大缺損系統相較健康的下顎骨，在承受咬合肌力時，骨頭的最大等效應力與應變分別增加了166%與181%，顯示即使有骨板作為支撐，缺損模型的骨頭仍承受更高的應力。此外，骨板彎折處有明顯的應力提高，且大缺損模型的骨板應力比小缺損模型的大。當分析時有考慮骨板的殘留應力，則小缺損模型骨板承受咬合肌力時的應力變大，會影響骨板的耐久性。大缺損模型無論骨板有、無殘留應力，受到咬合肌力時的應力皆超過降伏強度，顯示在下顎缺損較大的病例，若無搭配腓骨進行重建，骨板有高機率會發生斷裂。在鄰近缺損處植入骨釘時，骨釘周圍的骨頭等效應變比沒植入的還要大，且正10度植入者的應變最大，顯示在鄰近缺損處植入骨釘與植入角度皆會影響整體穩定度。本研究的限制包含骨板模型寬度不一致、骨釘模型未設計螺紋、未建立顳顎關節模型、骨板預應力作用位置與大小等，這些問題需要進一步探討。
;The mandible is one of the most susceptible areas of the facial bones to damage. In recent years, the use of mandible reconstruction plate for the treatment of segmental defects of the mandible has become increasingly widespread. These surgeries involve attaching metal plates to the fractured area and securing them with screws for support. However, despite the metal plates undergoing bending fatigue tests, many patients experience plate fractures or failures during mandibular recovery. Reconstruction plate are initially bent to fit the patient’s model preoperatively and are further adjusted during surgery to fit the contour of the patient’s mandible. However, past literature rarely analyzes the residual stresses and their impacts resulting from bending, leading to overly optimistic evaluations of the plate′s durability.
This study obtained the tensile properties of Ti-Grade.4 plates through experiments and verified the feasibility of plastic analysis including residual stress analysis in stamped plates. Mandibular models with different defect sizes (35 mm and 75 mm) and a healthy model were established. Occlusal muscle forces were applied to observe the stress and strain responses of the bones. Residual stress was induced in the plates using displacement control, and then occlusal muscle forces were applied to evaluate the biomechanical impact of the plates with and without residual stress on the mandibular reconstruction system. Additionally, the effects of inserting screws near the defect site, both vertically and inclined, were investigated.
The results showed that the true stress-strain curves obtained from the experiments were similar to those in other literature. In the stamped plate analysis, although the stress varied between different software, the residual stress distribution trends were similar when the punch pressed down and retracted. The analysis of the mandibular reconstruction system revealed that the reconstructed mandible with a large defect showed a 166% increase in maximum equivalent stress and a 181% increase in strain under occlusal muscle force compared to the healthy mandible, indicating that even with plate support, the bone in the defect model endured higher stress. Moreover, there was a significant increase in stress at the bent areas of the plates, with the stress in the plate of the large defect model being higher than that in the small defect model. When residual stress was present, the plate in the small defect model experienced increased stress under occlusal muscle force, affecting the plate′s durability. In the large defect model, stress exceeded the yield strength regardless of the presence of residual stress, indicating a high likelihood of plate fracture in cases of significant mandibular defects without fibula reconstruction. When screws were inserted near the defect site, the equivalent strain around the screws was higher than in models without screws, with the highest strain observed in screws inserted at a 10-degree inclination, showing that both the insertion of screws and the insertion angle affect overall stability. Limitations of this study include inconsistent widths in the plate model, the absence of threads in the screw model, the lack of a temporomandibular joint model, and uncertainties in the location and magnitude of prestress in the plates, which require further investigation. |
