PMC6222224_01
Postoperative AP radiograph showing the left hip's resurfacing arthroplasty. Femoral head was 46 mm. Acetabular cup was 52 mm and was placed too vertical; malposition of the components is a risk factor for pseudotumour.
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fig1
No signs of osteolysis were found in the hip anteroposterior radiography; nevertheless, a vertical cup was noted (Figure 1).
Computed tomography of the left hip: axial (a) and sagittal (b) views show periprosthetic osteolytic lesions (arrow head) in the anterior acetabular roof. Axial views (c, d) show a polylobate cystic lesion in the retroperitoneum compromising the left iliopsoas muscle with white arrows.
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fig2
Computed tomography and an MRI demonstrated a biloculate hypodense mass of approximately 34 x 19 cm that extended from the retroperitoneum, compromising the left iliopsoas muscle and an intimate contact with the femoral vessels, to the left hip and the left femoral-cutaneous nerve (Figures 2 and 3). As the CT shows (Figure 2(d)), the intrapelvic mass was significant, so it was decided to start with a laparotomy by the coloproctology surgeon.
In the metal artefact reduction sequence magnetic resonance imaging (MARS MRI), axial T1 (a), axial T2 (b), and sagittal T1 (c) show the presence of two lesions of thick walls located anterior to the psoas and iliacus (arrows) muscle. Within the lesion, a small focus of artefact is seen (arrow heads). This finding is critical to determining that the aetiology of the pseudotumour is "metallosis."
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fig3
Computed tomography and an MRI demonstrated a biloculate hypodense mass of approximately 34 x 19 cm that extended from the retroperitoneum, compromising the left iliopsoas muscle and an intimate contact with the femoral vessels, to the left hip and the left femoral-cutaneous nerve (Figures 2 and 3).
Four images from the first step of the surgery are shown. After a midline longitudinal infraumbilical approach, the left paracolic gutter was addressed (a) to obtain access to the retroperitoneum (b); a cystic tumour was observed in intimate contact with the iliopsoas muscle and the femoral nerve and vessels (c). The pseudotumour was punctured, and a grey milky-like fluid was obtained; then, the tumour was completely resected (d).
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fig4
The lesion was completely resected, and samples were sent for biopsy and cultures (Figure 4).
Four images from the second step of the surgery are shown. Through a posterolateral hip approach, an RHA was performed. The capsule was looking distend, so it was punctured (a), after capsulotomy the pseudotumour was evident (b), all components were removed, and an anterosuperior acetabulum wall defect was observed (c). Tumour sample, liquid and the hip prosthesis removed are shown in (d).
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fig5
After complete pseudotumour resection, RHA was performed (Figure 5).
In an immediate post-RHA pelvis anteroposterior X-ray, an adequate position of the components is seen.
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fig6
Post surgery, an anteroposterior pelvic radiograph was taken (Figure 6).
Histologic view of the soft tissue mass. (a) (40x) Hematoxylin and eosin (HE) shows an infiltrate of the macrophages with brown contents and detritus inside, near a necrotic area. (b) (100x) HE shows black particulates from the prosthetic material in a reparative tissue with fibroblast and neoformation of blood vessels.
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fig7
The analyses reported an extensive aseptic inflammatory infiltrate of macrophages with detritus inside near a necrotic tissue area (Figure 7(a)). ALVAL were observed. Also, reparative tissue was found with black particulate material corresponding to the prosthetic material near the neoformation of blood vessels and fibroblast (Figure 7(b)).
MRI (a) and (b) and CT (c) and (d) images taken five years post-RHA. There were no signs of pseudotumour after an extended follow-up.
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fig8
The MRI at five years of follow-up is shown in Figure 8.