PMC4109228_01
(a) AP radiograph of the right hip. A focal area of subchondral lucency is present involving the superolateral aspect of the right femoral head (arrow). (b) The follow-up radiograph taken 5 months later reveals near complete destruction of the femoral head. (c) CT scan of the right hip in the axial plane shows loss of the femoral head with two bone fragments within the hip joint (arrows).
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Initial plain films of her right hip and pelvis showed femoral head lucencies compatible with subchondral cysts (but no definite fracture) and moderate diffuse articular joint space loss with flattening of the femoral head (Figure 1(a)). Over a 5-month span, there was complete destruction of the right femoral head, erosion of the right acetabulum, and lateral subluxation of the proximal femur (Figure 1(b)). CT pelvis with contrast (Figure 1(c)) showed fragmented bone within the acetabular fossa, which was remnants of the femoral head resorption process.
(a) Axial proton density with fat saturation sequence through the right hip joint (a) shows destruction of the femoral head (arrow) and a complex joint effusion (arrowhead). (b) Axial T1 fat saturated sequence after gadolinium reveals synovial thickening and enhancement (arrow).
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Magnetic resonance imaging (MRI) of the right hip showed extensive synovial hypertrophy consistent with inflammatory arthritis (Figure 2). There were also minimal bone marrow edema and a fluid collection in the iliopsoas bursa extending posteriorly to the sciatic notch and enlargement of the hip joint capsule (Figure 2).
(a) Papillary, hyperplastic, chronically inflamed synovium is shown with abundant fibrin covering the surface and multiple fragments of bone being degraded by histiocytes and multinucleated giant cells. (b) At higher magnification, fibrin is seen on the surface of the synovium with a hyperplastic synovium consistent with chronic inflammation. (c) Fibrin and bone are detailed at 40x magnification showing multiple bone fragments which is typical of a rapidly destructive joint process. (d) Bone is seen being further broken down by multinucleated giant cells.
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In order to definitively differentiate between chronic sepsis, malignancy, and a chronic inflammatory process, an open biopsy of the hip was performed by the orthopaedic service, which showed overall morphology with features of chronic inflammation, fibrosis, multinucleated giant cell reaction with dystrophic calcification, and reactive synovial proliferation (Figure 3).