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Analysis of wear of retrieved metal-on-metal hip resurfacing implants
revised due to pseudotumours
March 2010
Link
http://www.ncbi.nlm.nih.gov/pubmed/20190305
Kwon YM, Glyn-Jones S, Simpson DJ, Kamali A, McLardy-Smith P, Gill HS, Murray
DW.
Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard
Medical School, Boston, Massachusetts 02114, USA. kwan.youngmin@mgh.harvard.edu
The presence of pseudotumours, which are soft-tissue masses relating to the hip,
after metal-on-metal hip resurfacing arthroplasty has been associated with
elevated levels of metal ions in serum, suggesting that pseudotumours occur when
there is increased wear. We aimed to quantify the wear in vivo of implants
revised for pseudotumours (eight) and of a control group of implants (22)
revised for other reasons of failure. We found that the implant group with
pseudotumours had a significantly higher rate of median linear wear of the
femoral component at 8.1 microm/year (2.75 to 25.4) than the 1.79 microm/year
(0.82 to 4.15; p = 0.002) of the non-pseudotumour group. For the acetabular
component a significantly higher rate of median linear wear of 7.36 microm/year
(1.61 to 24.9) was observed in the pseudotumour group compared with 1.28 microm/year
(0.81 to 3.33, p = 0.001) in the other group. Wear of the acetabular component
in the pseudotumour group always involved the edge of the implant, indicating
that edge-loading had occurred. Our findings are the first direct evidence that
pseudotumour is associated with increased wear at the metal-on-metal
articulation. Furthermore, edge-loading with the loss of fluid-film lubrication
may be an important mechanism of generation of wear in patients with a
pseudotumour.
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