雙顎正顎手術後軟組織變化之評估：從三度空間探討及利用超音波分析

Abstract

目的：本研究之目標，為前瞻性分析第三類咬合不正病患經正顎手術後，軟組織之組成及其變化。 方法：此初步臨床研究，收集2018年7月至12月於口腔顎面外科接受雙顎正顎手術之4名第三類骨性咬合不正病患，於兩個時間點取得其醫療紀錄及影像：術前（T0：術前4週內）及術後（T1：術後6個月以上），利用三種方法分析比較軟組織組成及其變化：傳統二維分析；利用Per-vertex動畫技術之三維分析；超音波分析，同時以彈性影像及分形盒維度作軟組織特性分析。 結果：以二維技術分析軟、硬組織移動關係，發現下唇平均往後移4.425 mm、往下1.975 mm，軟硬組織移動比值是Li:L1=1.13、B’:B=0.99；上唇平均往前移1.025 mm、往下3 mm，Ls:U1=0.89；頦部軟硬組織移動比Pog’:Pog=0.86、Men’:Men=1.16。 在三維分析方面，我們發現建立基礎模型以進行術前及術後形變，並分析術後各網點位置變化，為一可行概念，然而，若要建立高解像度之優化幾何模型，需要有更強運算能力。 超音波分析結果，總體而言，術後軟組織之灰值下降、厚度及分形維度增加；以下區域之厚度改變顯著：上唇皮膚（0.080 cm, P<0.05）、下唇肌肉及全層（分別為0.121及0.365 cm, P<0.05）、頦部肌肉、皮下組織及全層（分別為0.153、0.057及0.367 cm, P<0.05）；下唇皮膚及全層之灰值有顯著差異（分別為18.768及26.221, P<0.05），此外，頦部肌肉之術後灰值變化於是否接受頦成型術病患間有顯著差異。術前在有明顯頦偏移之病患中，發現頦偏移側之咬肌厚度比非偏移側大（ 1.961 cm相對1.408 cm），而其硬度及回音性則較低，術後兩側組織特性則趨近相同。術後，頦部及下唇顯示出Type II-III之內部纖維結構，且真皮與下方組織交界不規則，上唇則具Type I纖維結構，且真皮與其下組織交界規則。 結論：以三維方法診斷、擬定治療計畫、及預測手術結果，對齒顏面畸形的正確處置非常重要。利用形變技術評估軟組織變化應為一可行方法，但須以更強的計算能力作進一步研究。超音波分析發現軟組織變化為動態性且極為複雜，其組成及位置變化於不同顏面區域會受多重因子影響，因此應避免以簡單之軟、硬組織關係開發分析軟體，宜朝個人化及區域差異性之方向做進一步研究。 關鍵詞：軟組織、三維分析、顏面超音波、彈性影像、分形維度、正颚手術

Purpose: Prospectively examine the composition and changes of soft tissues in orthognathic patients with Class III malocclusion. Methods: This preliminary clinical study recruited four patients with skeletal Class III malocclusion who underwent bimaxillary orthognathic surgery at the Department of Oral and Maxillofacial Surgery, from July to December 2018. Complete medical records were obtained at two time points: pre-surgery (T0: within 4 weeks prior to surgery) and post-surgery (T1:at least 6 months after surgery). Changes in soft tissue position and composition were analyzed through the use of conventional two-dimensional analysis, three-dimensional Per-Vertex animation technique and ultrasound analysis, with the concomitant application of elastography and fractal box dimension for soft tissue characterization. Results: Regarding soft tissue to hard tissue movement by two-dimensional analysis, the lower lip moved on average 4.425 mm posteriorly and 1.975 mm inferiorly, reporting soft to hard tissue ratios of Li:L1= 1.13 and B’:B = 0.99. The upper lip moved an average of 1.025 mm forward and 3mm downward, with Ls:U1=0.89. The mental soft tissue reported ratios of 0.86 at Pog’:Pog and 1.16 at Men’:Men. For three-dimensional analysis, we found that the idea is feasible of building a base model for both pre and post operation morphing and then analyzing the location changes after surgery at every point given in the mesh. However, higher computing power is required for the construction of models with high resolution and optimized geometry. Concerning ultrasound study, in general, decrease of grey value, and increase in soft tissue thickness and fractal dimension were observed postoperatively. Changes in thickness were significant at the upper lip skin (0.80 mm, P <0.05); muscle and total lower lip area (1.21 and 3.65 mm, respectively, P <0.05); muscle, subcutaneous tissue and total mental area (1.53, 0.57 and 3.67mm, respectively, P <0.05). The differences in grey value were significant at the skin and total area of the lower lip (18.768 and 26.221, respectively, P <0.05). Moreover, significant difference in grey value changes was observed at the mental muscle area between patients with and without genioplasty. Before surgery, in patients with significant chin deviation, the masseter muscle on the chin-deviated side showed higher thickness when compared with the non-deviated side (1.961 cm vs. 1.408 cm), but lower stiffness and echogenicity. Post-operatively, these characteristics changed to almost equal between the two sides. After surgery, the mental and lower lip area presented Type II-III internal fibrillar structure with an irregular junction of the dermis to the hypodermis; the upper lip, showed Type I structure, with a smooth junction. Conclusions: The three-dimensional diagnosis, treatment planning and prediction of surgery outcomes are of great importance for the correct management of dentofacial deformity. The idea of applying morphing technique for the evaluation of soft tissue changes is feasible, but further studies with the use of higher computing power are needed. The dynamic and complex behavior of soft tissue could be observed by ultrasound analysis, stating the multifactorial character that influence its composition and position change at the different facial areas. Concluding that a simplistic hard to soft tissue relationship for the creation of software should be avoided and research that could apply this individual and regional variability should be encouraged. Key words: Soft tissue, three-dimensional analysis, facial ultrasound, elastography, fractal dimension, orthognathic surgery.