外固定器轴向加压骨折端髓内外在体的生物力学变化(英文)

Biomechanical change in exterior and interior medullary cavity at fracture end during axial compressing of external fixator in vivo

背景:骨在体生物力学长期在体测量一直是骨科和医学生物工程学者们关心的课题,应变计在此项测量中的应用被研究多年,但并未解决长期和连续测量问题。通过设计一种新型安装方法测量及分析骨在体生物力学。目的:探讨外固定器固定骨折时轴向加压骨折端髓内、髓外的在体生物力学变化。设计:随机对照动物实验。单位:武汉大学人民医院骨外科实验室。材料:健康大耳白兔18只,雌雄不限,体质量3.6～4.2kg。方法:2004-11在武汉大学人民医院骨科实验室完成该课题研究。取健康大耳白兔18只,随机均分为两组,每组各9只。髓外测量组:采用髓腔外骨皮质粘贴应变计法,根据轴向加压0.5倍和1倍体质量分为髓外测量0.5倍组和髓外测量1倍组;髓内测量组:髓腔内骨水泥包裹应变计法,根据轴向加压0.5和1倍体质量分为髓内测量0.5倍组和髓内测量1倍组。通过定标测得应变电压变化及加压后压力衰减值,各组间进行统计学比较。主要观察指标:①两组定标曲线数据。②两组不同加压后力衰减数据。结果:①髓外测量组加压定标曲线早期变化大,达到稳态后与髓腔内趋势相同,但髓腔外应变值明显大于髓腔内。髓内测量组加压达到稳态时间短,应变绝对值较髓外测量组小。②加压后达到稳态前,髓外测量0.5倍组与髓外测量1倍组相比,衰减速度低,髓内测量0.5倍组与髓内测量1倍组相比同样结果,髓外测量组与髓内测量组相比,髓外测量组下降后有上升趋势,髓内测量组无上升趋势。达到稳态后,髓外测量0.5倍组、髓外测量1倍组均有下降趋势,髓外测量1倍组下降速度快,髓内测量0.5倍组维持一定水平。髓内测量1倍组出现波动。结论:轴向加压时骨折端髓外应变值均显大于髓内,髓内较髓外易达到稳定状态,外固定器治疗骨折时初期加压量以0.5倍体质量为宜。

BACKGROUND： Biomechanics of bone in vivo is concerned by the scholars who work for orthopaedic and medical bioengineering all the time. The application of strainmeter in this measurement has been studied for many years, but the long-term and successive measuring problems have not been solved. A new installing method for analyzing biomechanics of bone in vivoshould be considered to be explored. OBJECTIVE： To investigate the biochemical change of external fixator at both external and internal medullary cavity of anxial compressing fracture end in vivo when external fixator is used DESIGN： Randomized and controlled animal experiment SETTING： Laboratory of Orthopaedic Department, Renmin Hospital, Wuhan University MATERIALS： Totally 18 healthy white rabbits, of rather gender, with the body mass of 3.6 to 4.2 kg, were chosen. METHODS： This experiment was conducted at the laboratory of Orthopaodic ,Department, Renmin Hospital, Wuhan University in November 2004. The chosen 18 healthy white rabbits were randomly divided into 2 groups. External measuring group （Group A）： the strain guage was affixed to the tibia external cortex by 502 gauge. Internal measuring group （Group B）： strain guage coated with bone cement was installed on the tibia internal cortex. Group A and Group B were divided into two subgroups A1, A2 and B1, B2, respectively according to the pressure 0.5 time body mass and 1 time body mass. Strain voltage change and attenuation coefficient after compressing were measured with scaler. Statistical comparison was performed among the groups. MAIN OUTCOME MEASURES： ① The data of scaler curve. ② Atten- uation coefficient of different compressions. RESULTS： ① The scaler curves of Group A changed greatly during early stage. After reaching stable stage, trendline of internal and external cortex went consistent but the former value was higher than that of the latter . The time of compression reaching stable was shorter in the Group B than in the Group A, and the absolute value of strain was smaller in the Group B than in the Group A. ② Before reaching stable after compression, the attenuation coefficient was low in the Group A1 as compared with Group A2. There was the same result between Group B 1 and Group B2 group. When comparison was conducted between Group A and Group B, the curve of Group A decreased firstly, then ascended, but there was no ascending tendency in the Group B. After reaching stable, there were descending tendency in the Group A1 group and Group A2. It descended fast in the Group A2, while it kept at normal level in the Group B1 group. Fluctuation appeared in the Group A2. CONCLUSION： Strain of external medullary cavity is significantly larger than that of internal medullary cavity. It is easier to reach stable in the internal medullary cavity than in the external medullary cavity. 0.5 time of body mass is suitable at the initial period in treating fracture with external fixator.