用于组织工程骨构建研究的兔单一负重骨缺损模型

A defect model of femoral shaft as alone weight-bearing bone of rabbit used in construction of tissue engineered bone

目的:为组织工程骨构建及修复负重长骨缺损的研究提供标准化的实验性骨缺损动物模型。方法:本实验于2004-10/2005-04在南方医科大学南方医院组织工程实验室和实验动物研究中心完成。①测量成年新西兰大白兔5只10具股骨干标本相关解剖数据并据此改进兔股骨固定方法。②18只新西兰大白兔随机分为3组,每组6只,分别制备10mm,15mm,20mm的股骨干中段骨和骨膜缺损,普通钢板螺丝钉及钢丝固定。③术后4,8,12周分别摄X射线侧位片进行定性分析、双能量X射线骨密度测量仪(DEXA)测量骨密度进行定量分析,各时间点每组各取2只标本做组织学检查。结果:23只兔均进入结果分析。①兔股骨测量结果:股骨长度(94.1±3.0)mm;股骨干中点横径(7.4±0.4)mm,矢状径(5.8±0.4)mm;骨皮质平均厚度(1.2±0.1)mm;髓腔平均直径(4.1±0.2)mm。②大体观察:4周时各组骨缺损均为纤维组织填充;8周时10mm骨缺损组已经见到骨痂连接;12周时10mm骨缺损组骨痂坚实,无异常活动,而15mm,20mm骨缺损组均为纤维瘢痕组织填充,去除内固定后有异常活动度。③X射线观察缺损区骨生长情况:10mm骨缺损组第12周时骨缺损区图像与4周时相比有明显的新骨形成;而15mm,20mm骨缺损组各时间段均无骨性填充影像;DEXA测量结果显示10mm骨缺损组在12周时新生骨已达临近骨组织密度的一半,而15mm,20mm骨缺损组各时间段的骨密度均为零。④组织学检查:12周时10mm缺损组由新生骨和软骨组织填充,部分髓腔再通;15mm,20mm骨缺损组在12周的观察期内只有骨断端和钢板螺丝钉周围有少量骨痂生长。以上各项检查显示:10mm骨缺损组均于8～12周出现骨性愈合;15mm和20mm骨缺损组直到12周仍未见骨愈合现象。结论:钢板螺丝钉固定的兔股骨干15mm以上的实验性骨缺损不能自行愈合,可用于组织工程骨的血管神经同步构建研究。

AIM： To establish a standardized experimental defect model of femoral shaft as alone weight-bearing long bone in rabbit, this defect cannot heal spontaneously. METHODS： The experiment was carried out in the tissue engineering laboratory and experimental animal research center of Nanfang Hospital of Southern Medical University between October 2004 and April 2005. ① Relative anatomic data of 5 New Zealand white rabbits＇ 10 femurs were measured in order to guide the surgical procedure. ② Based on the analyzing the anatomic data of rabbit femur and evaluating the probable damage of the screw to bone, 18 New Zealand white rabbits were randomly divided into three groups to create the femoral shaft segmental defects of 10 mm, 15 mm, and 20 mm respectively, with 6 rabbits in each group. The broken bones were fixed by conventional plates, screws and cerclage wires.③ Radiography, dual energy X-ray absortiometry （DEXA） and histology were all undertaken to examine bone formation of defects at 4, 8, 12 weeks postoperatively, 2 rabbits were selected at each time point in the histological test. RESULTS： Totally 23 rabbits were involved in the analysis of results, ① Results of femoral measurement in rabbits： The femoral length was （94.1±3.0） mm, the transverse diameter of middle shaft of femur was （7.4±0.4） mm, sagittal diameter was （5.8±0.4） mm, average thickness of cortical bone was （1.2±0.1） mm, and the average diameter of medullary cavity was （4.1±0.2） mm. ② Gross observation： At 4 weeks, the bone defects in all the groups were filled with fibrous tissue; At 8 weeks, connection of bony callus could be observed in the bone defect group; At 12 weeks, bony callus was solid and no abnormal activity was observed in the 10 mm defect group, but complement of fibrous scar tissue and abnormal activities after removal of internal fixation were observed in the 15 and 20 mm defect groups. ③ Bone growth in the defected region observed with X-ray： In tile 10 mm defect group, the image of bone defected region at 12 weeks showed that there were more new bone fi）rmations as compared with that at 4 weeks. But in the 15 and 20 mm defect groups, no bone complement at each time poiat, DEXA results showed that the new bone at 12 weeks in the 10 mm defect group was almost half of the density of bone tissue, but the bone densities in the 15 and 20 mm defect groups were zero at each time point. ④ Histological test： At 12 weeks, the 10 mm defect group was filled with new bone and cartilage tissue and part ofthe medullary cavities were recanalized, but only small amount of bony callus growth around broken end of bone and plate screw within 12 weeks The above tests showed that bone healing occurred at 8-12 weeks in the 10 mm defect group, but bone healing still could not be observed until 12 weeks. CONCLUSION： The bone defects of 15ram and more of rabbit femoral shaft fixed by conventional plate and screws cannot heal spontaneously. This critical-sized segmental bone defect model will be available for the research of bone tissue engineering.