液氮冷冻法诱导犬股骨头缺血性坏死模型MRI影像与病理观察

Observation on the MRI image and pathology image of the canine model with femoral head avascular necrosis induced by liquid nitrogen frozen

目的:从MRI影像和病理表现2个方面研究液氮冷冻法诱导的犬股骨头缺血性坏死模型。方法:选取12只健康成年雄性Beagle犬,通过手术暴露其右侧股骨头后用一铁制漏斗套于股骨头,将100～150 mL液态氮倒入漏斗内,并维持冷冻3 min,用37℃温盐水将股骨头复温。左侧股骨作为对照。造模后即开始观察实验犬的一般情况,造模后1个月随机选取6只Beagle犬进行双侧股骨头MRI扫描及病理学检测,造模后2个月对剩余6只Beagle犬进行双侧股骨头MRI扫描和组织病理学检测。结果:①MRI扫描。造模后1个月可见实验侧股骨头内于T1W上出现均质低信号,T2W信号升高,STIR信号升高更为明显,呈散在、点状分布于股骨头内;关节腔内可见少量关节积液;股骨头形态规则,边缘光滑,大小与对侧正常的股骨头一致。造模后2个月实验侧股骨头内于T1W上呈低信号,T2W上呈略高信号,STIR上呈略高信号;关节腔内积液;股骨头边缘不规则,变扁,变小;股骨头碎裂。②组织病理学观察。造模后1个月实验侧骨膜不完整,软骨部分脱落,软骨层变薄,软骨细胞排列紊乱;骨小梁稀疏变细,结构紊乱,有碎片出现,骨细胞陷窝空疏,骨细胞核固缩,部分血管栓塞;骨髓腔内造血组织明显减少,细胞数目及网状结构较正常稀疏,可见到大量脂肪细胞、多形核细胞、炎性细胞浸润,脂肪细胞体积增大,有的融合成泡状。造模后2个月实验侧关节面破坏严重,组织结构紊乱、破碎,关节软骨表层脱落、碎裂,软骨细胞排列紊乱,切线层变薄,同源软骨细胞数减少,软骨下潮线区变薄,钙化带与软骨下骨小梁不连续,呈"倒钟乳"状,软骨内可见到破骨细胞性骨吸收,形成髓腔。软骨下血管内可见血栓形成。骨基质中有大量的空骨陷窝,仅见少量骨细胞散在,细胞核固缩偏移。骨小梁稀疏、变细、不完整,出现微骨折,或骨小梁碎裂、紊乱,部分溶解呈片状。破骨细胞散在其间,骨髓组织坏死明显,有纤维组织增生修复,脂肪细胞肥大,也可见到其坏死、崩解后留下的空腔。骨髓内见出血区,造血细胞减少,大量脂肪细胞聚集,部分融合成大泡。结论:液氮冷冻法诱导的犬股骨头缺血性坏死模型符合股骨头坏死病变的一般规律,具有良好的重复性,是股骨头缺血性坏死的理想模型。

Objective：To study the canine model with femoral head avascular necrosis induced by liquid nitrogen frozen from the 2 aspects as MRI image and pathology image.Methods：Twelve healthy adult male beagle dogs were chosen for building models.Iiron funnel was set on the dog＇s right lateral femoral head exposed by operation,then 100 to 150 milliliter liquid nitrogen was infunded into the funnel and frozen state was maintained for 3 minutes,and next,the rewarming of femoral head was proceeded with 37℃ warm saline.The left lateral femoral head was served as the control.The general conditions of the experimental dogs were observed after modeling at once.One month after the modeling,6 beagle dogs were randomly chosen for MRI scanning and pathology testing in their bilateral femoral heads,and the same procedures were given to the other 6 dogs two months after the modeling.Results：①On the aspect of MRI scanning：one month after modeling,homogeneous low signals appeared on T1W images of the femoral head in experimental side,and signals enhanced on T2W images.Meanwhile,signals which scattered in a punctate pattern in the femoral head,enhanced more significantly on STIR images.A small amount of hydrops articuli was found within joint cavity.The shape of the femoral head was regular,while its edges were smooth and its size was consistent with the contralateral normal femoral head.Two months after modeling,low signals appeared on T1W images of the femoral head in experimental side,and slight hyperintensity signals appeared on T2W images and STIR images.There was hydrops articuli in joint cavity.The femoral head had irregular edges and appeared flat and smaller,or even broken into pieces.②On the aspect of pathological observation：one month after modeling,the following phenomenon appeared in the femoral head in experimental side as incomplete periosteum,partly loss of cartilage,thinner cartilage layer,disordered arrangement of cartilage cells;thinner and sparse trabecular bone with disordered structure and fragments;bone cells with loose and empty lacunes,karyopyknosis and partly embolismed blood vessel;significantly reduce of hematopoietic tissue in marrow cavity,less cells amounts and looser networks compared with the normal situations,appearance of infiltration with large amount of adipocyte,polymorphocyte and inflammatory cells,increased volume of adipocyte with some merged into bubbly shape.Two months after modeling,the following phenomenon appeared in the femoral head in experimental side as serious destruction of articular surface,disordered and shattered organization structure,abscission and fragmentation of articular cartilage surface,disordered arrangement of cartilage cells,thinner tangential layer,reduced amounts of isogenous chondrocytes,thinner tidal lines under the cartilage,discontinuation between calcified zone and subchondral trabecular bone which formed a shape as inverted stalactite,appearance of medullary cavity formed by osteoclastic bone resorption within cartilage;formation of thrombus in the subchondral vascular;large amount of empty bone lacunas and small amount of scattered bone cells in bone matrix,excursion and pyknosis of nucleus;sparse,thinner and incomplete bone trabecula with microfracture,or shattered and disordered bone trabecula with some merged into laminar shape;existence of scattered osteoclasts,prominent necrosis of myeloid tissue,appearance of fibroplasia repair,hypertrophy of fat cells with some of their left cavities after necrosis and disintegration;appearance of bleeding area in bone marrow,reduced amount of hematopoietic cells,aggregation of large amount of fat cells with some merged into bulla.Conclusion：The canine model with femoral head avascular necrosis induced by liquid nitrogen frozen,which is consistent with the general rule of femur head necrosis and is good in reproducibity,is a kind of ideal model for femoral head avascular necrosis.