大鼠股骨外固定架螺钉效能验证模型的建立及评价

Establishment and evaluation of a validation model for the efficacy of external femoral fixator screws in rats

背景:为了解决外固定螺钉的诸多并发症,各种改性螺钉层出不穷,但缺少合适的动物模型及评价方法用于验证其效能,尤其是模拟真实载荷。目的:探讨构建一种简单合理高效的SD大鼠外固定架螺钉效能验证模型及评价方法。方法:雄性成年SD大鼠30只,行右侧股骨截骨术,安装自制外固定架系统,在术后当天以及术后1,2,4,6周行常规X射线摄片。期间观察大鼠活动,术后6周统一取材,进行右侧大腿股骨带钉标本大体观察、生物力学测定、micro CT、钉道环境三维重建分析和组织学观察。结果与结论:①大鼠股骨骨折外固定模型造模时长为(20±5)min;②实验过程中大鼠一般情况及活动情况良好;③大体观察,30只股骨带钉标本中28只(93%)实现骨性愈合;1只(3%)愈合不良假关节形成,伴螺钉严重松动合并近端钉道周围大面积骨溶解;1只(3%)螺钉轻度松动合并严重钉道感染;1只(3%)仅出现严重钉道感染;模型总体一致满意率为90%(27/30);④X射线片显示,术后6周大鼠右侧股骨螺钉均固定在位、无松动,骨形态恢复,原断端位线良好,周围未见游离体,右侧髋膝在位;⑤Micro CT 3D分析,术后6周,模型大鼠内钉道周围骨密度(0.4267±0.0887)mg/cm2,骨体积分数(3.1252±1.0042)%,骨小梁数目(0.0003±0.0001)/μm;大鼠各参数分布情况进行正态性检验,总体趋于稳定,呈正态性分布;⑥苏木精-伊红染色显示,钉道周围区域被大量增生的肉芽组织修复,边缘可见新生的骨组织;Von Kossa染色显示,钉道周围均存在广泛的黑色或棕黑色的钙盐沉积;⑦生物力学测定,螺钉拔出力为(130.4167±35.0080)N,总体趋于稳定,呈正态性分布(P=0.2456);⑧结果表明,构建的SD大鼠股骨外固定架螺钉效能验证模型及评价方法,从组织学、影像学、生物力学3个层次进行评价分析,可对钉道情况进行全面的测评,且设计科学合理、手术过程简单、成功率高,具有较好的科研、临床应用价值。

BACKGROUND:In order to solve the complications of external fixation screws,various modified screws have emerged,but there is a lack of suitable animal models and evaluation methods for validating their efficacy,especially for simulating real loads.OBJECTIVE:To construct a simple,rational and efficient model that can be used to validate the efficacy of external fixator screws in Sprague-Dawley rats and establish the corresponding evaluation methods.METHODS:Thirty male adult Sprague-Dawley rats underwent the right femoral osteotomy,followed by fixation with a homemade external fixator system.Routine X-ray films were taken on the day after operation and 1,2,4,and 6 weeks after operation.During this period,the activity of rats was observed.At 6 weeks after operation,the rats were euthanized,and the right thigh femur with screw specimens were taken for general observation,biomechanical measurement,micro-CT,three-dimensional reconstruction analysis of the screw path and histological observation.RESULTS AND CONCLUSION:The modeling time of external fixation model of rat femoral fracture was(20±5)minutes.The general condition and activity of rats were good during the experiment.In general,28(93%)of the 30 femoral specimens with screws achieved bone healing;1 case(3%)had poor pseudoarthrosis formation with severe screw loosening accompanied by large osteolysis around the proximal screw path;1 case(3%)had mild screw loosening combined with severe screw path infection;1 case(3%)only had severe screw path infection.The overall satisfactory rate of the model was 90%(27/30).Radiological findings revealed that the right femoral screws were fixed in place without loosening,the bone morphology was restored,the broken end was well aligned,no free body was seen around the broken end,and the right hip and knee were in position at 6 weeks after operation.Micro-CT three-dimensional analysis showed that body mineral density,bone volume fraction,and the number of bone trabeculae around the internal screw path were(0.4267±0.0887)mg/cm2,(3.1252±1.0042)%,and(0.0003±0.0001)/μm respectively,at 6 weeks after operation.Intra-model group distribution and normality test were performed,and all the data tended to be stable and normally distributed.Hematoxylin-eosin staining showed that the area around the screw path was repaired by a large amount of proliferating granulation tissue,and new bone tissue was visible at the edges.Von Kossa staining revealed the presence of extensive black or brownish-black calcium deposition around the screw path.Biomechanically,the screw extraction force was(130.4167±35.0080)N,which tended to be generally stable and normally distributed(P=0.2456).To conclude,the validation model and evaluation method for the efficacy of external femoral fixator screws in Sprague-Dawley rats can be evaluated from three aspects:histology,imaging and biomechanics,and the screw path can be comprehensively evaluated.The design is scientific and reasonable,the procedure is simple,and the success rate is high.Therefore,this validation model has good value for scientific research and clinical application.