正顎手術後下顎構造與運動學的變化

臨床齒顎矯正治療中，面對嚴重骨性差異(severe skeletal discrepancies)所造成的顏面畸形(dentofacial deformity)，正顎手術(orthognathic surgery)常為改善顏面部外觀(facial esthetics)及恢復正常咀嚼功能(restore the function)的治療選擇。相關於正顎手術後的外觀改善的主、客觀因素研究不少，但相關於正顎手術後的功能性(下顎運動學)改善的相關文獻卻較為闕如。本研究的目的旨在探究運用正顎手術改正下顎前突後，在相對形態改變下對於下顎運動學的影響及趨勢。本研究包含兩個部份，以十位臨床實際接受單顎下顎手術(one-jaw surgery)並以骨板固定骨端術式(rigid fixation)的患者(平均年齡為25.54歲)為研究受測對象，探討接受下顎骨後移(mandibular setback)的正顎手術術式下，型態的改變對於下顎骨運動學的影響。實驗一於正顎手術前後兩個時間點於正中咬合位下以三維立體椎狀斷層掃瞄器(cone-beam CT scanner, i-CAT)取得全頭顱立體影像，分別量取手術前後下顎骨關節頭間距(inter-condylar width)的相對位置關係，並分析相關位置改變的因素。實驗二則運用步態分析實驗室中的Vicon 512®光電系統測量在自然頭部直立(upright head position)狀態下，分別測量手術前後最大張閉口(Maximum mouth opening)、矢向及水平向邊際運動(border movement)等數值。該系統能夠建構出一個50立方公分的工作範圍、測量解析度可達0.0008mm，而最終系統測量之絕對誤差小於0.4mm。實驗結果顯示:(一)所有的受試者於進行正顎手術將前突的下顎骨後縮並以骨板堅固固定的術式後，於三維立體椎狀斷層攝影的測量下，下顎骨關節頭於水平方向位置皆有改變。(二)下顎骨運動方面，於光電系統分析手術前後運動軌跡，於最大張閉口、水平及矢狀邊際運動三種運動測量數值於手術後範圍皆有變小的趨勢。實驗結論:下顎骨後移後以堅固內固定固定骨端後，無論後移程度的多寡或是否合併側移手術，下顎關節頭位置皆有某種程度的位移，下顎骨關節頭頂端間距(Co-Co’)於手術後(T2)平均增加為1.42mm、增大範圍為0.9~2.2mm。經由手術後移後在正中咬合位(CO)兩側下顎關節頭內外單連線(Line B)與中線(Line A)夾角角度的變化大多趨勢為不變或為負值(意即關節頭朝向中線旋轉,inward rotation)。而正顎手術對於下顎骨運動學的影響，根據光學動作分析系統的初步分析，張閉口及邊際運動等動作，若從單純的線性關係(linear measurement)來看，所有的病例最大開口量皆減少，最大張口量於口外測量手術後減少平均減少為4mm、範圍為2~6mm，在統計學上具有差異。然而，若以角度來看，手術後開口量減少程度並不大，在統計學上不具有差異。解釋手術後，開口量並沒有受到太大的影響。下顎骨經過手術後移後，由其水平邊際運動的趨勢可以看出較接近中心軌跡、左右側移運動軌跡變得較為對稱；於矢狀邊際運動有較為明顯的前方導引(anterior guidance)的軌跡；咀嚼運動軌跡較為平順且範圍較小。而十位受測者手術後至目前為止(post-operation 6 months)尚無任何顳顎關節症狀(TMDs)發生。

關鍵字

正顎手術；下顎骨運動學；光電三維動作分析系統；椎狀束斷層掃描

並列摘要

Orthognathic surgery is a common treatment option for improving facial esthetics and restoring occlusal function due to severe dentofacial deformity. There were many studies searching the factors associated with facial improvement. However, little were the articles focusing on the functional improvement. Therefore, the effects y of the structural and kinematical changes after orthgnathic surgery are investigated in current study. Ten subjects (average age: 25.5 y/o) who received mandibular setback surgery (BSSO and rigid fixation) were included. Before surgery (T1) and post-surgery (T2), all subjects were arranged for CBCT scan to analyze the changes of condylar position in experiment I. In experiment II, all subjects were under upright head position calibrated with cervical range of motion instrument, maximum mouth opening between upper and lower incisor edge by using the ruler with 0.5 mm accuracy were measured. And under this position, the horizontal, sagittal and chewing stroke movements were captured and analyzed by the optoelectronic recording device (Vicon 512®). This set-up yielded a working volume of 50X50X50 cm3 with spatial resolution of 0.0008mm and absolute system measuring error being less than 0.4 mm. The present results: (1) most of the condylar position was changed in axial view after BSSO and rigid fixation. (2) in kinematical measurements, the range of MMO, horizontal, sagittal border movement and chewing stroke decreased but became more consistent with better occlusal guidance after surgery under optoelectronic analysis. The conclusion of present study : (1) there were some degree of lateral movement of the proximal segments after rigid fixation(T2), the inter-condylar width was increased 1.42 mm in average, range from 0.9~2.2 mm. Inward movement was also detected from the axial view in most of the subjects. (2) the extent of MMO and border movement were decreased in linear measurement (4 mm in average, range from 2~6 mm), but the degree of MMO when expressed in angular amount was not significantly changed after the surgery.

並列關鍵字

orthognathic surgery ； mandibular kinematics ； motion analysis system, ； cone-beam CT

參考文獻

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正顎手術後下顎構造與運動學的變化

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