title: Analysis of wear of retrieved metal-on-metal hip resurfacing implants revised due to pseudotumours.
abstract: 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.
authors.affiliation: Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA. kwan.youngmin@mgh.harvard.edu
authors.forename: Y-M
authors.initials: YM
authors.lastname: Kwon
authors.forename: S
authors.initials: S
authors.lastname: Glyn-Jones
authors.forename: D J
authors.initials: DJ
authors.lastname: Simpson
authors.forename: A
authors.initials: A
authors.lastname: Kamali
authors.forename: P
authors.initials: P
authors.lastname: McLardy-Smith
authors.forename: H S
authors.initials: HS
authors.lastname: Gill
authors.forename: D W
authors.initials: DW
authors.lastname: Murray
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D003240:Connective Tissue Diseases / Q000209:etiology / Q000601:surgery*; D005260:Female; D006104:Granuloma, Plasma Cell / Q000209:etiology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008422:Materials Testing / Q000379:methods; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation / Q000379:methods; D013314:Stress, Mechanical; D013499:Surface Properties