Effect of stress shelter for internal fixation of mandibular fractures in dogs
LIU Shijun1，LI Xiangli2，and WANG Lijun3.
1.Department of Stomatology，Beijing Youwai Hospital，Beijing 100069，China；
2. Department of Stomatology， Hunan Provincial Corps Hospital，Chinese People’s Armed Police Forces, Changsha 410006，China；
3. Department of Stomatology，General Hospital of Chinese People’s Armed Police Forces， Beijing 100039，China
摘要 目的 对下颌骨骨折内固定术后拆除小型接骨板前后应力遮挡效应进行动物实验研究，为下颌骨骨折愈合后内固定材料的远期处置提供理论依据。 方法 18只犬中3只犬即刻处死测定下颌骨骨密度和最大断裂力，该组设为正常组。其余15只犬人为造成双侧下颌骨骨折并行双侧小型接骨板固定（每只犬右侧为实验侧，左侧为对照侧）。固定2个月后，3只犬处死双侧取板测定骨密度和最大断裂力，该组设为0月组；其余12只犬右侧（实验侧）小型接骨板全部取出，取板后再经过1、2、3、6个月后各处死3只犬取左侧（对照侧）板，分别设为1、2、3、6个月组。比较左右两侧下颌骨在骨密度、最大断裂力上的异同。 结果 1、2、3、6个月组实验侧和对照侧骨密度值比0月组高（ P <0.05），实验侧和对照侧比较各组之间差异无统计学意义。6个月组对照侧的骨密度值与正常组比较较低，差异有统计学意义（ P <0.05）。1、2、3、6个月组实验侧和对照侧与0月组比较最大断裂力值较高（ P <0.05）。实验侧和对照侧比较，各组间最大断裂力差异均无统计学意义； 6个月组对照侧与正常组比较最大断裂力值较低，差异有统计学意义（ P <0.05）。 结论 随着内固定时间的增加，在本实验中出现了应力遮挡效应。另外在内固定3个月时下颌骨实验侧和对照侧骨密度和最大断裂力值较高，说明内固定3个月时拆除接骨板可能最有利。
Abstract：Objective To compare the stress-shielding effect before and after removal of the small bone plate for mandibular fracture fixation in order to provide a theoretical basis for long-term disposal of fixed materials after healing of mandibular fracture. Methods Eighteen adult male mongrel dogs with removal of the titanium bone plate after healing of mandibular fracture were divided into groups of 0, 1, 2, 3, 6-months according to the time of internal fixation removal. Two months after internal fixation, the plates were taken out in one group with bilateral plates (0 month group) and out of the right side in the remaining four groups (experimental side). After 1, 2, 3, 6 months of internal fixation removal, the left plates were taken out and bone density and tensile stress of the left and right mandibles were compared. Results Bone mineral density of experimental and control sides in the 1, 2, 3, 6-month groups were higher than that in 0-month group ( P <0.05), and there was no significant difference between experimental and control sides in each group. Bone density of the control side in 6-month group was lower than that in normal group, with significant difference ( P <0.05). The maximum breaking strength on experimental and control sides in 1, 2, 3, 6-month groups was higher than that in 0-month group ( P <0.05).When the experimental and control sides were compared, the maximum breaking strength between the groups was not significantly different. The maximum breaking strength in 6-month group on the control side was lower than that in normal group, with significant differerce ( P <0.05). Conclusions With the increasing duration of internal fixation, the effect of stress shelter will occur. After 3 months of internal fixation, bone density and the maximum breaking strength on experimental and control sides of mandibles will increase, indicating that the best time to remove the bone fracture plate fixation is 3 months.
刘世军，李向利，王立军. 犬下颌骨骨折内固定术后应力遮挡效应的实验研究[J]. 武警医学, 2012, 23(5): 400-402.
LIU Shijun，LI Xiangli，and WANG Lijun. Effect of stress shelter for internal fixation of mandibular fractures in dogs. Med. J. Chin. Peop. Armed Poli. Forc., 2012, 23(5): 400-402.
