Home Japanese values The influence of bone marrow edema for the assessment of necrotic lesion boundaries in patients with osteonecrosis of the femoral head

The influence of bone marrow edema for the assessment of necrotic lesion boundaries in patients with osteonecrosis of the femoral head

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This study was approved by our institutional review board. It was conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all patients prior to the study. MRI was performed on 828 hips in 588 patients with ONFH between January 2005 and February 2016. Among them, we retrospectively reviewed 72 consecutive hips in 55 patients who underwent CE MR imaging examination for the reason that it was difficult to assess the limit of necrosis. lesion due to EMB after subchondral collapse (ARCO stage III or higher, Fig. 1) or it was difficult to differentiate ONFH from subchondral insufficiency femoral head fracture or transient osteoporosis of the hip, by MRI without injection19.

Figure 1

Diagrams showing the 2019 revised systems of the Association Research Circulation Osseous (ARCO) and the Japanese Investigation Committee (JIC). ARCO stage I, low intensity T1 band on MRI imaging with no specific findings on standard radiographs; Stage II, delineating sclerosis without collapse on standard radiographs; Stage IIIA, collapse less than or equal to 2 mm; stage IIIB, collapse greater than 2 mm; Stage IV, osteoarthritic changes. In this study, 55 hips are classified as stage IIIA and 17 hips as stage IIIB. JIC type A, the necrotic zone occupies the middle third or less of the weight-bearing part; Type B, middle two-thirds or less; Type C1, more than two-thirds but not extending to acetabular rim; Type C2, more than two-thirds and extending to the acetabular rim. In this study, 55 hips are classified as stage IIIA and 17 hips as stage IIIB, and 4 hips are type B, 30 hips are type C1 and 38 hips are type C2.

Thirty-two hips were treated by transtrochanteric anterior rotation osteotomy, 2 hips by transtrochanteric posterior rotation osteotomy, 10 hips by transtrochanteric curved varus osteotomy and 26 hips by prosthetic replacement. Two hips were observed continuously without surgical treatment. Three of 44 (6.8%) cases treated with joint-sparing procedures underwent prosthetic replacement due to osteoarthritic change after osteotomy (2, 4, and 4 years, respectively). One case (2.2%) underwent prosthetic replacement due to pseudarthrosis at the osteotomy site caused by deep infection after surgery. The survival rate was 91.0% (criteria: prosthetic replacement), with an average of 9.1 years after osteotomies (range, 5 to 15 years). The ONFH stage (ARCO classification revised 2019) and the location of the affected lesion (Japanese Investigation Committee (JIC) classification) are shown in Fig. 116.20. A delimiting sclerosis was present on 51 hips (70.8%) on the AP or lateral radiograph21.

MRI images were obtained with a 1.5 T MRI unit (Achieva 1.5 T; Philips Healthcare, Best, The Netherlands) in 52 hips and a 3.0 T MRI unit (Achieva 3.0 T; Philips Healthcare , Best, Netherlands) in 20 hips . After obtaining T1-weighted, fat-saturated (FS) T2 spin-echo images (coronal only) (repetition time/echo time[TR/TE]= 400–540/10–18ms, FST2; 3000–4709/80–100), CET1-weighted images with fat saturation (TR/TE = 620–700/10–18) were obtained by administering 0.2 ml/kg gadopentetate dimeglumine (Magnevist; Bayer Pharma , Berlin, Germany). All sequences had a slice thickness of 5 mm with a gap between slices of 1 mm and a field of view of 360 × 360 mm. The duration of the MRI imaging examination was 30 to 40 min. T1-, FST2-, and CET1-weighted images were available in 68 of 72 hips (94.4%) in the coronal plane, and unenhanced, CET1-weighted images were available in 67 of 72 hips (93.1%) in the coronal plane. oblique-axial plane. plane (parallel to the axis of the femoral neck) (Fig. 2). According to medical records, the mean time from onset of hip pain to MRI examination was 4.7 months (range: 0.5 to 19 months).

Figure 2
Figure 2

Flowchart demonstrating image selection from the coronal and oblique-axial planes of MRI. * Osteonecrosis of the femoral head, Gadolinium, Fat-saturation.

In the coronal plane, necrotic lesion boundaries were assessed by medio-lateral necrotic angles using T1-weighted and FST2-weighted MR images on midline coronal slice, and were compared with those of CET1-weighted MR images. (Fig. 3). In the oblique axial plane, necrotic lesion boundaries were assessed by AP necrotic angles using T1-weighted MRI images on a midline oblique-axial slice and compared with those of CET1-weighted MRI images ( Fig. 3). When the necrotic angles between the T1- or FST2- and CET1-weighted images differed by more than 10°, the case was defined as a difference group (Fig. 3). Degrees of BME extension (BME grade) were classified as grade I (into the femoral head), grade II (beyond the femoral head but into the femoral neck), and grade III (beyond the femoral neck ) using all slices of T1, FST2 and CET1 on the coronal and oblique axial planes (Fig. 4). Assessments were made by two observers (SI and TU), who are orthopedic surgeons and have extensive experience in diagnostic imaging. To assess the intra- and inter-observer reproducibility of boundary assessments between necrotic and live bone comparison between unenhanced and CET1 images, and BME grade assessments, the reliability of the measurements was assessed using statistics. kappa. A kappa value of 0.21 to 0.4 indicates fair agreement; 0.41–0.6, moderate agreement; and 0.61–0.8, substantial agreement. A value > 0.81 is considered nearly perfect22.

picture 3
picture 3

Method for evaluating the limit of the necrotic lesion. (a) The medial and lateral limits of the necrotic lesion are assessed on the two non-enhanced median coronal T1s (arrows), saturated fat (FS) T2 (arrows) and contrast-enhanced (CE) T1 images (arrows). When the difference of more than 10° between the angles α, β and γ is observed, the case is classified as difference group. In this example, the angles α, β and γ are respectively 118°, 97° and 98°. Therefore, this case is classified as T1 coronal image difference group and FST2 coronal image no difference group. (b) The anterior and posterior limits of the necrotic lesion are assessed on both the unenhanced mid-oblique-axial T1 (arrows) and CET1 images (arrows). When the difference of more than 10° between the angles δ and ε is observed, the case is classified as a difference group. In this example, the angles γ and δ are 129° and 115° respectively. Therefore, this case is classified in the difference group.

Figure 4
number 4

Method for evaluating the degree of extension of the BME. category I; The BME is limited to the femoral head. Class II; The BME exceeds the femoral head but remains in the femoral neck. Class III; The BME goes beyond the femoral neck to reach the trochanteric region.

After comparing the necrotic lesion boundaries between the non-enhanced and CE MR images, all hips were divided according to the differences between the two images. Statistical analyzes were performed using the chi-square test or Fisher’s exact probability to compare gender, history of steroid or alcohol use, stage, type, and presence of delimiting radiological sclerosis between the two groups. Age, BMI and time since the start of the MRI examination were compared between the two groups using the you-test. The BME grade between the two groups and the relationship between the time since the start of the MR imaging examination and the BME grade were analyzed using the Mann-Whitney scale you test and the Wilcoxon signed rank test, respectively. Multivariate analysis was performed to identify parameters associated with differences in necrotic lesion boundaries between CE and unenhanced MRI images using stepwise logistic regression with variable selection (P Pvalues ​​

Ethical approval and consent to participate

This retrospective study was approved by the Kyushu University Institutional Review Board for Clinical Research (NO. 2019-584). Written informed consent was obtained from all patients prior to the study.