title: The effect of different bearing surfaces on metal ion levels in urine following 28 mm metal-on-metal and 28 mm metal-on-polyethylene total hip arthroplasty.
abstract: OBJECTIVE
  Recent advancements in manufacturing technology have enabled more precise tolerances and surface finishes using metal-on-metal bearing surfaces in total hip arthroplasty. The aim of this study was to compare the level of metal ions in urine after implantation of a 28-mm metal-on-metal bearing manufactured from high-carbon wrought alloy and a 28-mm metal-on-polyethylene bearing.
  
  
  METHODS
  A total of 92 total hip arthroplasty patients were prospectively randomized into two groups: those receiving metal-on-metal bearings and those receiving metal-on-polyethylene bearings. Chromium, cobalt, and molybdenum ion levels in urine were measured preoperatively and at 1 year and 2 years postoperatively.
  
  
  RESULTS
  In the metal-on-polyethylene group, there was a slight increase in mean chromium and cobalt concentrations at 2-year follow-up compared to the preoperative level (p = 0.02 for both chromium and cobalt). In the metal-on-metal group, there was a 15-fold increase in chromium and a 26-fold increase in cobalt at 2-year follow-up compared to the preoperative level (p < 0.001 for both chromium and cobalt). However, the quantity of chromium and cobalt in urine from the metal-on-metal group was not higher at 2-year follow-up than at 1-year follow-up (p = 0.5 and p = 0.6, respectively).
  
  
  CONCLUSIONS
  The 28-mm metal-on-metal bearings yield chromium and cobalt concentrations in urine that can be higher than those recommended for occupational exposure. However, our results also indicate that a steady state in wear and ion production using metal-on-metal total hip arthroplasty can occur.
authors: Department of Rheumatoid Diseases, Turku University Hospital, Paimio, Finland.
authors: H
authors: H
authors: Tiusanen
authors: K
authors: K
authors: Mäkelä
authors: M
authors: M
authors: Kiilunen
authors: P
authors: P
authors: Sarantsin
authors: E
authors: E
authors: Sipola
authors: M
authors: M
authors: Pesola
mesh_terms: D000497:Alloys; D001168:Arthritis / Q000601:surgery*; D001172:Arthritis, Rheumatoid / Q000601:surgery; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D015415:Biomarkers / Q000652:urine; D002857:Chromium / Q000652:urine; D003035:Cobalt / Q000652:urine; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D007477:Ions / Q000652:urine; D008297:Male; D061825:Metal-on-Metal Joint Prostheses; D019216:Metals, Heavy / Q000652:urine*; D008875:Middle Aged; D008982:Molybdenum / Q000652:urine; D015207:Osteoarthritis, Hip / Q000601:surgery; D020959:Polyethylene; D011446:Prospective Studies; D011474:Prosthesis Design; D016896:Treatment Outcome
chemical_list: D000497:Alloys; D015415:Biomarkers; D007477:Ions; D019216:Metals, Heavy; D002857:Chromium; D003035:Cobalt; D008982:Molybdenum; D020959:Polyethylene
keywords: Total hip arthroplasty; bearing surfaces; head size; metal ion levels; metal-on-metal; wear