骨折愈合早期磁共振成像的实验研究

目的 探讨骨折愈合过程中磁共振成像(MRI)的表现及变化规律.方法 6只新西兰白兔右侧桡骨中段制造垂直长度为10 mm、断端间隙为1 mm的长斜形骨折愈合模型.左侧桡骨中段制造10 mm骨质缺损模型.于术后1、2、4、6、8、12周对动物模型行X线及MRI扫描,于术后4 周及12周行螺旋CT扫描,观察骨折愈合过程中T1序列、T2序列、T2压脂(FS-T2)序列、质子(PD)序列及质子压脂(FS-PD)序列影像学表现.结果 骨折后早期周围软组织在T2序列、FS-T2序列、PD序列及FS-PD序列显现为弥漫高信号,随着时间推移,信号强度逐渐下降,至骨折后6周恢复中等信号.骨髓腔在骨折后早期T1序列、T2序列及PD序列由正常高信号变为中等信号,随着髓腔的修复,逐渐恢复为高信号;而FS-T2序列及FS-PD序列髓腔早期显现为中等信号内混杂高信号,随着骨折愈合,混杂高信号逐渐消散.骨折后2周,在FS-T2序列及FS-PD序列发现的中等信号颗粒与之后骨痂的形成位置一致.骨质缺损模型无上述表现.结论 MRI可以比X线更早发现骨折愈合的变化,FS-T2序列及FS-PD序列对骨折愈合早期能更好地加以显像.骨折愈合早期MRI成像的变化有待于病理学的进一步验证.

Early changes of fracture healing on MRI

Objective To observe MRI presentations of fracture healing process in the early stage.Methods Six New Zealand rabbits were used in the experiment. A union model of long oblique fracture of 1 mm in bone defect and 10 mm in vertical length was created on the right radius. A model of 10 mm bone defect was created on the left radius. X-ray and MRI examinations were performed in 1 w, 2 w, 4 w, 6 w, 8 w, 12 wafter the surgery and CT examination was performed in 4 w, 12 w after the surgery. The imaging presentations at the fracture sites were observed on T1, T2, FS-T2, PD, FS-PD sequences. Results The soft tissue around the fracture site presented high signals on T2, FS-T2, PD, FS-PD sequences in the early stage of fracture healing. The signals decreased as time went on, but turned intermediate at 6 w after surgery. The signals of bone marrow turned from high to intermediate on T1, T2 and PD sequences early after the surgery,but turned high again with the healing of medullary cavity. On FS-T2 and FS-PD sequences, bone marrow presented intermediate signals mixed with high signals, but the high signals subsided as time went by. Early changes of callus formation could be observed by MRI. Callus formation at the site of fracture showed intermediate signals in FS-T2 and FS-PD images obtained at 2 w after the surgery in the fracture union model. The changes above could not be observed in the bone defect model. Conclusions Callus formation may be predicted earlier by MRI than by X ray, especially on FS-T2 and FS-PD sequences. The MRI presentations of early fracture healing are to be confirmed by pathological examinations.