PMC8550852_01
Right knee: (a) AP and (b) lateral radiographs at the time of presentation (February 2019).
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The patient was initially referred by the primary surgeon to our oncology clinic in February 2019 due to findings of a distal femur lesion in her right knee discovered on follow-up X-rays (Figure 1) and better seen in a noncontrast MRI.
MRI of the right knee with IV gadolinium. In the distal femur, there is low T1 signal in the sagittal (a) and axial (b) views and heterogeneously predominantly low T2 signal in the sagittal (c) and axial (d) views with a sharp rim and thin peripheral enhancement (white arrows) that is in continuity with the prosthesis and typical for osteolysis secondary to particle disease (MRI machine: Titan 3T (Toshiba)).
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MRI with IV contrast was performed to further characterize this mass in the right distal femur and rule out a malignant lesion (Figure 2).
Right knee: (a) AP and (b) lateral radiographs six months later (October 2019).
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TKA for the diagnosis of massive femoral osteolysis and impending femoral fracture. The patient was later seen preoperatively, and the pain and X-rays remained stable (Figure 3).
Intraoperative findings. (a) Lateral view of the distal femur showing massive osteolysis of the lateral condyle. (b) Top-down view of the distal femur after implant removal showing extension of the osteolysis into the canal. (c) Top view and (d) backside view of the X3  insert with no evidence of wear or surface damage. The entire polyethylene surface demonstrated yellow discoloration consistent with oxidation.
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There were massive cystic changes with some debris that we sent for pathology (Figure 4).
Histological analysis. (a, c) Multinucleated foreign body giant cells with engulfed shards of PE debris (H&E 40x). (b, d) H&E under refractile light.
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Microscopic evaluation (Figure 5) of the periprosthetic tissue revealed features typically observed when implant failure has taken place.
Right knee: (a) AP and (b) lateral radiographs at one-year follow-up.
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At one-year clinical follow-up, the patient was noted to be doing well with no changes in her radiographic examination (Figure 6).