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Abstract
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Although a pseudotumor is a known complication of metal-on-metal (MoM) total hip arthroplasty (THA), a malignant process should be ruled out before surgical intervention.
We present a case of a 62-year-old patient, who was believed to have a MoM related pseudotumor for years turning out to be an angiosarcoma.
After primary implantation, the patient presented 16 years later with a cup loosening, which was diagnosed by performing a SPECT CT. Prior to revision surgery in January 2017, we performed a CT scan of the hip, which showed a new solid mass, likely a MoM related pseudotumor, reaching from the left hip into the pelvis.
In 02/2019, a prosthesis joint infection (PJI) was suspected, due to new pain in the upper leg and a suspect SPECT-CT scan and a joint sample showing Staph. Epidermidis. A revision surgery was performed with no confirmation of an infection.
In 08/2019 the patient presented with recurrent posterior dislocation and requiring inlay change. 3 weeks later the patient was readmitted with massive exudation of the wound and a hemoglobin of 45 g/L. The performed CT scan showed only the known mass believed to be a MoM Pseudotumor. The patient was treated as a PJI with debridement and implant retention, no active bleeding was found intraoperatively. After continuing secretion, even with negative pressure wound dressing another revision was necessary.
Prior to surgery CT-Angio was obtained, showing again no active bleeding. Our hematologists could not find a disorder explaining the bleeding. After the second revision, the bleeding continued, and with an active blood loss of unknown origin, the patient was referred to the University hospital of Basel (USB).
After several further revisions without stopping the bleeding the pseudotumor was suspected to be the origin of the blood-loss, the mass was excised en bloc as R2 resection showing an angiosarcoma. Post R2 resection there were no further surgical options. Palliative radiotherapy was performed, stopping the bleeding.
It is discussed that long-existing MoM pseudotumors can transform into a malignant process. Angiosarcoma are rare with >1% of all soft tissue sarcoma. Survival rates post diagnosis range from 6-16months.
After this case, we recommend to confirm the diagnosis of a pseudotumor with with MARS-MRI and histological analysis of every unknown mass resected in joint replacement surgery.
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