髁突颈横行截骨和骨折对大鼠下颌骨生长发育的影响

Effects of condylar neck ostrotomy or fracture on growth and development of mandible in rats

目的 建立年轻SD大鼠单侧髁突颈部截骨、骨折的动物模型,探讨应力改变对大鼠下颌骨及髁突生长发育的影响.方法 4周龄72只雄性SD大鼠按随机数字表法分3组,每组24只,分为截骨组、骨折组、对照组.建立大鼠单侧髁突颈部横行截骨,骨折的动物模型,观察术后1、3、5、9周髁突影像学、组织学及下颌骨解剖学的变化.检测与髁突生长发育关系密切的结缔组织生长因子（CTGF）及X型胶原（Col X）在髁突软骨中表达的变化.结果 截骨组手术侧术后1、3周髁突区膨大,髁突颈呈分离影像.骨折组手术侧术后1周髁突呈圆柱状,见骨折线.截骨组手术侧术后4个时间点下颌骨生长发育受到限制,髁突软骨的总厚度术后1周代偿性增厚为（1468.28±53.73） μm,大于骨折组手术侧;术后3、5周总厚度明显降低;术后9周与骨折组手术侧比较差异无统计学意义（P＞0.05）,但都小于对照组（P＜0.05）.截骨组手术侧CTGF在髁突软骨中的表达在术后1、3、5周分别为60.18±1.23、72.43±2.82、86.00±2.90均高于骨折组手术侧和对照组Col X表达在术后1周时为64.46±3.76,高于骨折组手术侧和对照组（均为P＜0.05）.结论 单侧髁突颈截骨,致应力改变明显,影响下颌骨及髁突生长发育,可导致手术侧、非手术侧下颌骨的不对称,并影响CTGF及Col X在髁突软骨的表达.

Objective To establish the condylar neck osteotomy or fracture rat model,and to determine the effects of stress changes on the growth and development of mandible.Methods Seventy-two SD rats of 4 weeks age were randomly assigned to unilateral condylar process osteotomy group （n=24）,fracture group （n=24） and Sham operation group （n=24）.Following construction of the models of unilateral condylar process osteotomy,the imaging characteristics,histological and anatomical changes were recorded at 1,3,5 and 9 weeks.Expressions of development-associated connective tissue growth factor （CTGF） and type X collagen （Col X） were assayed by immunohistochemical staining.Results The condyle on the operated side was enlarged and the neck separated on imaging at weeks 1 and 3 in unilateral condylar process osteotomy group.However,in fracture group,the condyle appeared to be cylindrical,which demonstrated the fracture line at week 1.Unilateral condylar process osteotomy was associated with retarded growth and development of mandible in the operated side at weeks 1,3,5 and 9.The thickness of condylar cartilage enlarged compensatorily to （1468.28±53.73） μtm at week 1 compared with that in fracture group （P＜0.05）.This was followed by a gradual decline in the thickness at weeks 3 and 5 that was not statistically different from that in fracture group at week 9 （P＞0.05）.Both groups yielded a reduced level of thickness compared with Sham operation group （all P＜0.05）.The CTGF expression at the operated side in unilateral condylar process osteotomy group was 60.18±1.23,72.43±2.82 and 86.00±2.90 at weeks 1,3 and 5,respectively,which were higher compared with those in fracture group and Sham operation group （all P＜0.05）.At week 1,Col X expression （64.46±3.76） was significantly augmented compared with that in fracture group and Sham operation group （both P＜0.05）.Conclusion Unilateral condylar process osteotomy may result in asymmetry of the mandible at operated and non-operated side as well as altered expression of CTGF and Col X in the condyle chondria,which arises from significantly altered stress and retarded development of the mandible and condyle.