股骨头坏死、修复过程的MRI及与病理对照的实验研究

MR Imaging and Histologic Findings of Avascular Necrosis in a Canine Model

目的:取得股骨头坏死的MRI与病理对照的资料。材料和方法:我们采用液氮冷冻的方法将30只杂交狗制作成股骨头坏死模型。动物分以下10组:1天,7天,17天,23天,1个月,2个月,3个月,6个月,9个月及12个月。所有动物均进行平片（离体及活体）、CT、MR检查。观察坏死后股骨头的密度及信号改变情况。结果:1个月以内组,所有动物于活体时平片均未发现异常。离体后,17天后可见密度有轻度的增高。1个月及以后组活体及离体均可见不同程度的密度改变。2个月有囊变,3个月可见轻度塌陷。CT于17天即可发现有密度增高,1个月可见有囊变,2个月时可见有微骨折。MR除1天组未发现异常外,其他组均可见不同程度的信号改变。信号异常范围由小变大,至1个月后整个股骨头均可见信号异常。T1加权低信号,T2加权可见混杂信号（1个月以内）、均匀高信号（1-3个月）、高信号内出现低信号（3个月以后）。组织学改变:1天仅表现脂肪细胞肥大,7-23天可见炎性细胞渗出、纤维肉芽组织开始出现。1个月以后,主要为肉芽组织修复。塌陷的股骨头病理显示坏死的骨小梁吸收和新产生的骨小梁骨折,骨性重建不完全。结论:股骨头坏死的MR表现与病理改变是一致的;MR较CT、平片敏感。

Purpose: To examine MR and histologic changes of avascular necrosis of femoral head. Materials and Method: Thirty adult mongrel dogs were induced to develop avascular necrosis of right femoral head by freezing method with liquid nitrogen. All animals were divided into ten groups according to postoperative days 1, 7, 17, 23, and months1, 2, 3, 6, 9, 12.All dogs were examined with plain radiograph, CT and MRI. The changes of density and intensity were concerned. Results: The in vivo radiographs showed no changes within one month. The in vitro radiographs showed changes in density on days 17 and 23. The in vivo radiographs showed all sorts of changes in density after one month. A slight increase in density was seen at the first postoperative month; cystic changes at two months after operation; three month later, most dogs had some degree of collapse.CT showed cystic changes one month postoperatively; a radiolu-cent crescent line appeared two months later. Except for the first postoperative day, MR showed abnormalities starting from day 7 and a gradual increase in the size of low signal within the normally high signal marrow space. Mongrel signal was seen within one month, homogeneous signal between 1 and 3 months and nonhomogeneous signal after three months Histologic examination showed a progression of changes beginning with fat necrosis, followed by the appearance of an inflammatory infiltrate, and subsequently proliferation of fibrocytes. New bone formation was seen on day 23, and extended from the femoral neck to the head. When the head collapsed and bony repair was completed, subchondral bone tra-beculae showed resorption and fracture with a poor bony reconstruction.Conclusions: MRI of necroticfemoral head showed a good correlation with the histologic findings and was more sensitive than CT and Conventional Radiographs.