title: Blood metal ion concentrations in metal-on-metal total hip arthroplasty.
abstract: BACKGROUND
  The hip placement with a metal-on-metal (MOM) bearing has been used for both surface replacement and total hip arthroplasty (THA). Use of MOM bearing for hip replacement reduces the wear compared to conventional bearings.
  
  
  METHODS
  We prospectively assessed 30 patients who underwent unilateral MOM THA. A control group of 30 patients who underwent metal-on-polyethylene THA using the implants as the other group, except for bearing, were accessed. Blood samples were collected preoperatively and at 3- , 6- , 9- , 12- , 15- , 18- , and 24-month intervals. Changes in mean blood metal ion concentration were compared between the MOM and metal-on-polyethylene groups.
  
  
  RESULTS
  A statistically significant positive correlation was observed between blood cobalt and chromium concentrations in all of the patients. The mean blood ion concentrations of the MOM were significantly higher than those of the metal-on-polyethylene. A statistically significant negative correlation was found between maximum blood cobalt concentration and cup version angle. The maximum blood chromium concentrations in the patients who had larger cup version angles were more likely to decrease.
  
  
  CONCLUSIONS
  We considered that cup version angle is one of the factors that have the greatest effect on blood metal ion concentration, and the target cup version angle that did not induce an increase in blood metal ion concentrations was approximately 20°.
authors.affiliation: Department of Orthopedic Surgery, Tokyo Women's Medical University, 8-1 Kawada-Cho, Shinjuku Ward, Tokyo, 162-8666, Japan. tada0403@gmail.com.
authors.forename: Tadahiko
authors.initials: T
authors.lastname: Ohtsuru
authors.affiliation: Department of Orthopedic Surgery, Tokyo Women's Medical University, 8-1 Kawada-Cho, Shinjuku Ward, Tokyo, 162-8666, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Morita
authors.affiliation: Department of Orthopedic Surgery, Tokyo Women's Medical University, 8-1 Kawada-Cho, Shinjuku Ward, Tokyo, 162-8666, Japan.
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Murata
authors.affiliation: Department of Orthopedic Surgery, Tokyo Women's Medical University, 8-1 Kawada-Cho, Shinjuku Ward, Tokyo, 162-8666, Japan.
authors.forename: Shuji
authors.initials: S
authors.lastname: Shimamoto
authors.affiliation: Department of Orthopedic Surgery, Tokyo Women's Medical University, 8-1 Kawada-Cho, Shinjuku Ward, Tokyo, 162-8666, Japan.
authors.forename: Yutaro
authors.initials: Y
authors.lastname: Munakata
authors.affiliation: Kita Shinagawa 3rd Hospital, 3-3-7 Kita-shinagawa, Shinagawa Ward, Tokyo, 140-0001, Japan.
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Kato
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods*; D001774:Blood Chemical Analysis; D016022:Case-Control Studies; D002857:Chromium / Q000097:blood*; D003035:Cobalt / Q000097:blood*; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D061825:Metal-on-Metal Joint Prostheses / Q000009:adverse effects*; D008875:Middle Aged; D011446:Prospective Studies; D011474:Prosthesis Design; D012016:Reference Values; D018570:Risk Assessment
chemical_list: D002857:Chromium; D003035:Cobalt
keywords: Angle; Cup version angle; Ions; Metal; Metal-on-metal; Total hip arthroplasty