| Background and purpose Non-traumatic Avascular osteonecrosis of the femoral head( N-ANFH) is caused by blood supply lack of the bone tissue, which is also known as aseptic bone necrosis; It's a common clinical refractory disease, early diagnosis and treatment of the disease has been much concerned by clinicians. It's a huge challenge for doctors to treat these patients in time,or else it can eventually lead to lateral collapse of the articular surface and thus results in secondary osteoarthritis of the hip, causing joint deformity and having serious impact on the life quality of the patients. Risk factors of non-traumatic osteonecrosis of the femoral head include corticosteroid drugs, alcohol abuse, chemotherapy and immuno-suppressive agents and so on. It was also noted that the disease may be genetically related recently. Early detection and diagnosis can greatly influence the success of treatment of the disease,which has a great chance to save their hips.Therefore, early prediction of femoral head necrosis is very important, which may lead to early intervention, thus can avoid further developing into more severe clinical symptoms. The purpose of this study is to analyze early femoral head necrosis(before the collapse of the femoral head) in clinical diagnosis and prediction of femoral head necrosis change in aspects of blood supply by using enhanced MRI examination. And to compare the permeability difference between necrotic area and normal bone area, in order to assess the extent of necrosis and supply the basis for early diagnosis. To ensure that patients at an early stage of the disease can be treated early and condition been monitored.Materials and methods1 Subjects Patients from March 2015 to September 2015 at the First Affiliated Hospital of Zhengzhou University were included in this study. 21 patients on MRI showed unilateral femoral head necrosis of early stage were recruited, totally 42 hips. All patients underwent none biopsy, arthroscopy or other intervention measures which may affect the imaging performance before MRI examinations. Three cases out of 21 patients belong to ARCO stage I, the remaining 18 cases belongs to ARCO stage II.There were 13 males(with smoking and drinking history) and 8 females(with a history of glucocorticoids), the median age is 34 years(ranging from 21 to 49 years old). 9 patients showed different degrees of bone marrow edema in the femoral head,femoral neck and the upper section of the femoral bone; 4 patients with sacroiliac joint inflammation.All patients were scanned using a Philips 3.0T MRI machine(Ingenia) using body surface coil. All patients underwent unenhanced MRI examination, sequences include coronal T1 weighted image(T1WI), coronal T2 weighted image(T2WI),coronal and axial fat-suppressed T2 weighted images; eight of the patients underwent dynamic enhanced MRI examination,which means a three-dimensional coronal T1 dynamic contrast-enhanced sequence. Contrast agent is gadopentetate preserved amine(Gd-DTPA, Bayer), flow rate 3.0ml/kg; NS 20 ml, flow rate 2ml/s.2 Image evaluation methods All patients' images were analyzed on Phllips workstation. MRI images of all patients were analyzed and evaluated by two experienced physicians in MRI department. When the comments were inconsistent, the final consensus were reached after discussion by the two doctors. MRI measures include: the signal characteristics of femoral head osteonecrosis, necrotic area, with or without accompanying bone marrow edema and arthritic disorders. Met lab associated software is then used to obtain enhanced images of both hips and were selected appropriate Region of interest(ROI), and then measure Ktrans value, Kep value and the area under the curve(AUC),and then compare these parameters and to draw the receiver operating curve(Receiver operating curve, ROC). In the metaphysis, the head and the upper section of femoral bone were selected four ROI, representing granulation tissue(ROI1),sclerotic rim zone(ROI2), red bone marrow(ROI3), yellow bone marrow(ROI 4);Then to select two corresponding ROIs in the normal position of the control side as RBM and YBM. Further analysis of the difference of Ktrans and Kep between the four ROIs. Secondly, to compare whether there is difference of the fat fraction on both sides. Dixon sequence can finally get four images, which is positive phase sequence, reverse phase, water and fat phase image. The ROI are processed on both sides respectively using Image J. Paired t test was used for statistical analysis.3 Data Analysis The experimental data were applicated using SPSS17.0 statistical analysis software for analysis. All data using mean ± standard deviation, variance analysis and LSD-test were applied to verify the relation of Ktrans value, Kep value, and AUC value between different ROIs. Paired t-test were applied to analyze fat fraction variance between the lesion and the normal control side. P? <? 0.05 was considered statistically significant.Results There's no significant difference of Ktrans value(P = 0.314) and Kep value(P =0.379) between normal and necrotic femoral head in red marrow distribution zone.There's also no significant difference of Ktrans value(P = 0.386) and Kep value(P =0.417) between normal and necrotic femoral head in yellow marrow distribution zone.In necrotic femoral head, Ktrans value results as follows: granulation tissue > the sclerotic rim > RBM >YBM, Ktrans values between granulation tissue and sclerotic rim having a statistically significant difference(P = 0.04), Ktrans values between granulation tissue and RBM(P = 0.000) or YBM(P = 0.000) having a statistically significant difference, Ktrans values between sclerotic rim and RBM(P = 0.015) or YBM(P = 0.007) having a statistically significant difference. Ktrans values between granulation tissue and YBM having a statistically significant difference(P = 0.013).Kep values between these other ROIs showed no statistically significant difference.ROC curve analysis showed that eight cases of patients with N-ANFH DCE-MRI examination, Ktrans is the best test performance for predicting osteonecrosis of the femoral head, which up to 0.917. The analysis of fat fraction between normal and pathological side having a statistically significant difference(P = 0.001), and the necrosis side was higher than the normal side; but the fat fraction showed no significant within the two groups respectively.Conclusions1. Dynamic enhanced MRI scans play an important role in diagnosing early non-traumatic femoral head osteonecrosis;2. Ktrans and Kep value have a high diagnostic sensitivity in diagnosing and Ktrans value is more sensitive;3. Fat fraction is higher in the normal side than the necrotic femur. |
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