口内牵引成骨修复下颌骨缺损的生物力学研究

Intraoral distraction osteogenesis for the repair of mandibular defect——An biomechanical study

目的观察口内牵引成骨修复下颌骨体部缺损新骨形成的X线和生物力学特征。方法以beagle实验犬4条为实验对象,建立人工下颌骨体部2.0cm缺损实验模型;半年后,二期手术形成骨传送盘,固定口内牵引器,术后10d起,以0.5mm/次,每日2次的频率向恒定的方向行牵引传送骨盘,至缺损区完全封闭。固定35周后安乐处死动物,切取标本行X线摄片,测定新骨组织的弯曲极限强度和硬度并与正常骨组织比较。结果①下颌骨缺损完全封闭,传送骨盘与远端骨段形成骨性联接,新生的骨组织形态与自然下颌骨相同,不易区分。传送骨盘与对侧基骨形成骨性融合。②新骨组织形成正常皮质骨和松质骨结构,放射密度低于正常下颌骨。③压力实验DO间隙新骨组织平均极限强度(69.4±19.2)MPa,相当于正常下颌骨的(78±3.5)%。传送骨盘与基骨的连接部位平均极限强度(46.9±8.4)MPa,相当于正常下颌骨的(49.3±3.9)%。结论应用口内双端式传送牵引成骨术修复下颌骨缺损,术后35周新骨组织改建成熟为适应正常生理功能的骨质结构,为临床应用提供了实验依据。

Objective： To explore the roentgenographic and biomechanical characters of distraction osteogenesis （DO） in the treatment of mandibular defect. Methods：4 beagle dogs were used to establish 2.0 cm mandibular defect model, after 6 months, a 1.5 cm transport disc was surgically created adjacent to the defect area in an intraoral way, and intraoral device was placed on the transport disc and the base bone segments. A reconstructive plate was applied to stabilize the bone segments. After a 10 day latency period, the transport disc was advanced at a rate of 0.5 mm × 2/day until the bone fragments were docked at the planned position. 35 weeks after completion of distraction the animals were sacrificed, specimen retrieval, roentgenography and the stress testing were performed. Results：The regenerated segments were comparable with the corresponding segments of native mandible, and exact location of junction between the regerated and preexisting bone could not be determined easily. Roentgenographic revealed that the defects were reconstructed with outer cortical layer and trabecular medullary cavity of the bone. The regenerated segments remained less radiodense than the native mandible. Stress test demonstrated that the average ultimate strength of regenerated segmens was （69.4 ± 19.2） MPa,that of the corresponding normal mandible was （86.9 ± 31.9） MPa, and that of junction between transport disc and base bone was（46.9 ±8.4） MPa. Conclusion： Intraoral distraction osteogenesis may be feasible in the treatment of mandibular defect.