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Case Reports
. 2014 Mar 18:2014:bcr2013202801.
doi: 10.1136/bcr-2013-202801.

Metallosis in a total knee arthroplasty

Bhairavi Vivegananthan  1 , Rohi Shah, A S Karuppiah, S V Karuppiah
Affiliations
Case Reports

Metallosis in a total knee arthroplasty

Bhairavi Vivegananthan et al. BMJ Case Rep. .

Abstract

A 70-year-old woman presented with right knee pain and a 'grinding' sensation 6 months after a total knee replacement for osteoarthritis. Clinical examination revealed a valgus deformity, patellofemoral crepitus and a reduced knee flexion. Radiographs revealed distinctive findings including the 'bubble sign', 'cloud sign' and the 'metal line sign', which are diagnostic of metallosis. Metallosis is an uncommon complication of total joint replacements, where bone and periprosthetic soft tissues are infiltrated by metallic debris from wearing of the prostheses. This usually occurs in high-wear joints such as hips and knees. Treatment for patients diagnosed with metallosis is synovectomy and a revision surgery. Our patient underwent revision surgery 5 years after her initial surgery.

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Figures

Figure 1
Figure 1
A curvilinear radiodensity referred to as the ‘bubble sign’. This is also seen in figure 2 (arrow A).
Figure 2
Figure 2
(Arrow B) An amorphous cloudy density within the soft tissues posterior to the prosthesis, known as the ‘cloud sign’. The same image also shows evidence of periprosthetic osteolysis. Arrow A shows the ‘bubble’ sign as previously mentioned.
Figure 3
Figure 3
A thin rim of increased linear density outlining a portion of the joint capsule. This is known as the ‘Metal-line Sign’, which is diagnostic of metal-induced synovitis. Other radiological findings associated with metallosis are joint effusion, pseudotumours and metallic fragmentation.
Figure 4
Figure 4
Six-month follow-up films after the revision total arthroplasty with the Oxinium prostheses, showing no loosening or wearing.
Figure 5
Figure 5
Six-month follow-up films after the revision total arthroplasty with the Oxinium prostheses, showing no loosening or wearing.
See this image and copyright information in PMC

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