生長期迷你豬施行單側下顎骨牽引性骨生成術之顳顎關節骨質組織學觀察

Abstract

牽引性骨生成術(Distraction Osteogenesis)廣泛應用於治療成長期中顱顏部發育異常的病患，使之能夠提早建立正常的生理性功能。然而文獻中關於下顎牽引性骨生成術造成顳顎關節的變化尚無定論，其中又很少將生長因素列入考量。本實驗的目的即為以生長期迷你豬為實驗對象，探討下顎進行單側牽引性骨生成術後，顳顎關節骨質組織學的變化。 實驗共計6隻具有生長潛力的迷你豬(年齡分布為5週至12週大，處於混合齒列)，分成三組：(1)實驗組A，n=1，實驗側施行單側下顎骨截斷並裝置口內延長器，術後經過7天的延遲期，每天以0.9公厘的速度逐漸延長下顎，共延長14天，延長完成後固定4週再進行犧牲。(2)實驗組B，n=2，延長完成後固定8週再進行犧牲，以觀察長期的變化。(3)控制組，n=1，以相同之規則進行牽引，開始牽引四天後，因牽引軸被豬隻撞落而無法繼續牽引，停止牽引後固定8週再進行犧牲；將之歸入控制組，以觀察同樣經過單側下顎骨截斷及放置口內延長器，但僅經過少量牽引，對顳顎關節影響之差異。(4)對照組，n=2，為與實驗組B犧牲時年齡相近的健康迷你豬，作為提供對照組織的對照。為了研究骨頭的動態變化，在實驗期間以皮下注射生物螢光染色劑的方式，進行活體的骨頭標定，再以倒立螢光顯微鏡觀察不同螢光層線之部位及分布，以觀察顳顎關節周圍骨質沈積的速率與部位。 研究結果發現，在關節軟骨下方的骨質，不論是實驗組或是對照組，由關節髁的前端到後端，都只看到在犧牲前所標定的calcein，只能顯現出成長中的豬隻，在整個下顎關節髁有相當旺盛的骨質沈積及代謝。然而在顳顎關節窩，卻可以發現到在靠近關節腔的部位，骨沈積的速率即使在固定期一個月及兩個月後，比對照組的骨沈積速率來的快，代表下顎的牽引延長，不僅外側關節髁頭受牽引的力量往關節窩接近，而影響關節髁及關節盂窩的形態、軟骨厚度及下方基質的分解，也會影響到顳顎關節窩的骨生成速率。 另外在牽引器的固定骨釘周圍，也發現大量的骨質吸收及發炎反應，而造成固定骨釘的提早鬆脫，無法提供良好的固定功能，因此無法將牽引的力量完全傳達至截斷骨的兩端，導致預期牽引量與實際牽引量產生落差。 因此，牽引性骨生成術能夠有效地延長下顎，對顳顎關節的形態及骨生成速率會產生影響，惟在形態上的變化以及可能對下顎運動功能的影響仍須更長期的追蹤觀察。

Distraction osteogenesis has been widely used in congenital anomalies to correct craniofacial deficiency. Clinically it is frequently conducted on growing patients for early establishment of normal physiological functions. However, the effects on temporomandibular joints undergoing mandibular distraction are still controversial, and the influence of growth was not taken into consideration in most of the research. In this study, we investigated the effects on bone remodeling of TMJs in growing mini-pigs in which unilateral mandibular distraction osteogenesis was performed. Six (5~12 weeks, 6~15kg weight) Lee-Sung genus of mini-pigs were divided into 4 groups: 1) Experimental group A (n=1), received osteotomy and the distractor device (Leibinger intraoral distractor) was fixed on one side of the mandible. After one-week latency period, the mandible was distracted for 2 weeks with the velocity of 0.9 mm/day. The animals were sacrificed after a consolidation period of 4 weeks. 2) Experimental group B (n=2), the animals received the similar treatment as Experimental group A, except that they were sacrificed after a consolidation period of 8 weeks. 3) Control group (n=1), the distraction was little for the distractor was broken after 4 days of distraction. And 4) Normal group, 2 healthy mini-pigs without any operation were used. To examine the changes of bone remodeling of TMJs, polychrome labeling of bone was performed. According to the bone labeling, the bone deposition and remodeling in the TMJs was very active during the entire experimental period. The thickness of cartilage of condyles decreased after 4 weeks of consolidation period, and it didn’t return to normal after 4 weeks later. The bone deposition of the glenoid fossa was more active in the experimental group then in the normal and control groups after 4 or 8 weeks of consolidation period. These findings revealed not only the condyle but also the glenoid fossa adapt to the distraction. Remarkable bone resorption around the fixation screws of distractors was also noted. Therefore, they cannot provide enough stability during the distraction. In conclusion, distraction osteogenesis is an effective way to lengthen the mandible with subtle and transient changes in bone remodeling of TMJ. A longer-term observation will reveal whether these changes would last and affect the mandibular movement and function.