PMC2800008_01
A 28-yr-old woman with pain in both hips, which occurred at gestation 32 weeks in the left hip and immediately after delivery in the right. Anteroposterior radiograph obtained 1 week postpartum shows marked osteopenia in both proximal femurs.
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F1
Plain radiographs taken at 1 week postpartum showed diffuse osteopenia in both proximal femora, which was more marked in the left side (Fig. 1).
MR images taken at 2 weeks postpartum demonstrate the presence of a typical bone marrow edema pattern in both proximal femurs. T1-weighted coronal image (upper) shows decreased signal intensity area in the femoral head, neck, and intertrochanteric areas. With gadolinium enhancement (lower), the decreased intensity area was markedly enhanced.
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F2
No definite MR crescent sign was detected (Fig. 2).
Serial radiographs taken during follow-up. (A) Anteroposterior radiograph obtained at 4 weeks postpartum shows marked osteopenia in both proximal femurs. The bone density in the left side had increased and that in the right side had decreased slightly as compared with radiographs taken at 1 week postpartum (Fig. 1). (B) Anteroposterior radiograph obtained at 7 weeks postpartum shows increased osteopenia in the right femoral head. However, bone density in the left femoral head had recovered markedly. At this time, the left hip pain had almost completely disappeared. (C) Anteroposterior radiograph obtained at 11 weeks postpartum shows markedly increased bone density in both femoral heads. At this time, the right hip pain had almost completely disappeared. (D) Anteroposterior radiograph obtained at 20 weeks postpartum shows complete bone density recovery in both femoral heads. Slight dimpling (arrow) is observed in the superolateral end of the right femoral head, and this was persistent on anteroposterior radiograph taken at one year postpartum.
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F3
Bone densities of proximal femora recovered in parallel with symptomatic improvement (Fig. 3).
On MR images taken at 7 weeks postpartum, the bone marrow edema in the left proximal femur had decreased markedly, whereas bone marrow edema persists in the right proximal femur. At this time, left hip pain had almost completely disappeared.
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F4
Follow-up MR images taken at 7 weeks postpartum showed markedly reduced bone marrow edema in the left and increased bone marrow edema in the right. (Fig. 4).
Serial coronal 3D-CT images taken during follow-up are shown. Coronal CT image of a healthy young woman (control) shows well-oriented vertical primary compression trabeculae with normal bone density in both femoral heads. Image obtained at 4 weeks postpartum (4 w) shows reduced bone density in both proximal femurs, and a loss of thickness and continuation of vertical primary compression trabeculae. Area of irregular spotty increased bone density (arrowhead) is observed in the left femoral head immediately below the subchondral bone plate. Breakages of the subchondral bone plate (short arrows) and a sclerotic line (long arrow) obliquely crossing vertical primary compression trabeculae are observed in the right femoral head. Image taken at 11 weeks postpartum (11 w) shows a marked increase in trabecular density in both femoral heads. Area of irregular spotty bone density (arrowhead) is also observed in the right femoral head. Image taken at 20 weeks postpartum (20 w) shows almost normal appearing vertical trabeculae in both femoral heads. The irregular spotty bone density decreased. Image taken at one year postpartum (1 y) shows normalized vertical trabeculae in both femoral heads. The irregular spotty bone density has decreased further at this stage.
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F5
Coronal multiplanar reformation (MPR) CT images were taken serially to evaluate the condition of trabecular bone of the femoral heads (Fig. 5).