title: Predicting wear and blood metal ion levels in metal-on-metal hip resurfacing.
abstract: Suboptimal component position and design are thought to lead to edge wear and raised blood metal ion levels in metal-on-metal hip resurfacing (MOM-HR). These factors are thought to influence the "contact patch to rim distance" (CPRD), and calculation of this distance may improve prediction of wear and blood metal ion levels. We measured blood cobalt and chromium ion levels and the wear rates of the bearing surfaces in 165 MOM-HR retrieval cases. We then determined the contribution and effect sizes of cup inclination and version angles, component size and design, and CPRD (calculated from case-specific data) on blood metal ion levels and component wear rates. Acetabular orientation explained between 16.3% and 28.5% of the variation in wear rates and metal ion levels, whereas component size and design explained between 7.3% and 21.8% of the variability. In comparison, CPRD explained up to 67.7% of the variability, significantly greater than any other variable (all p < 0.0001). CPRD is a good predictor of wear and improves our understanding of wear performance and the mechanisms leading to edge loading.
authors.affiliation: Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex, HA7 4LP, United Kingdom.
authors.forename: Ashley K
authors.initials: AK
authors.lastname: Matthies
authors.forename: Johann
authors.initials: J
authors.lastname: Henckel
authors.forename: Suzie
authors.initials: S
authors.lastname: Cro
authors.forename: Alexander
authors.initials: A
authors.lastname: Suarez
authors.forename: Philip C
authors.initials: PC
authors.lastname: Noble
authors.forename: John
authors.initials: J
authors.lastname: Skinner
authors.forename: Alister J
authors.initials: AJ
authors.lastname: Hart
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000379:methods; D002857:Chromium / Q000097:blood* / Q000493:pharmacokinetics; D003035:Cobalt / Q000097:blood* / Q000493:pharmacokinetics; D019544:Equipment Failure Analysis; D005260:Female; D006621:Hip Joint / Q000378:metabolism / Q000601:surgery; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011474:Prosthesis Design; D012086:Reoperation; D055815:Young Adult
chemical_list: D002857:Chromium; D003035:Cobalt
keywords: hip resurfacing; metal ions; metal-on-metal; retrievals; wear