title: A prospective study of ceramic-on-metal bearings in total hip arthroplasty at four-year follow-up: clinical results, metal ion levels, inflammatory factor levels, and liver-kidney function.
abstract: BACKGROUND
  Despite the theoretical advantages of ceramic-on-metal (CoM) bearings observed in laboratory settings, limited clinical data are available to support in vitro results. Our present study prospectively investigated the clinical results, serum metal ion levels, inflammatory factor levels, and liver-kidney function in a cohort of patients who received total hip arthroplasty (THA) with CoM bearings.
  
  
  METHODS
  The cohort comprised 82 THAs in 71 patients (41 men and 30 women), with a mean age of 54 (range 22-77) years. The mean follow-up was four years. All patients completed pre- and postoperative clinical assessment using the Harris Hip Score, Short Form-12, Western Ontario and McMaster Universities Osteoarthritis Index, and radiographic analysis. The serum metal ion levels of cobalt, chromium, molybdenum, and titanium were measured using high-resolution inductively coupled plasma mass spectrometry, and were compared with normal reference values. Inflammatory factors including C-reactive protein, erythrocyte sedimentation, and interleukin-6 levels, and liver-kidney function including alanine aminotransferase, aspartate aminotransferase, total bilirubin, creatinine, and blood urea nitrogen, were measured in our hospital clinical key laboratory.
  
  
  RESULTS
  At the end of the follow-up period, all clinical assessments showed a statistically significant improvement. Although the inflammatory factor levels and liver-kidney function were within normal ranges, the serum levels of metal ion were significantly elevated compared with normal values: cobalt, 2.8 μg/L; chromium, 2.2 μg/L; molybdenum, 0.9 μg/L; and titanium, 2.1 μg/L. Spearman's correlation analysis showed an association between cobalt, chromium, and titanium metal ion levels and BMI values.
  
  
  CONCLUSIONS
  Our study demonstrated that the use of a CoM THA was clinically effective and that metal ion levels were significantly elevated at midterm follow-up. Whether the elevated metal ion levels may reduce adverse reactions is unknown, and long-term follow-up is needed.
authors.affiliation: Department of Orthopaedic Surgery, West China Hospital, West China Medical School, Sichuan University, 37# Guoxue Road, Chengdu, 610041, Sichuan, People's Republic of China, zengyigd@126.com.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zeng
authors.forename: Bo
authors.initials: B
authors.lastname: Zheng
authors.forename: Bin
authors.initials: B
authors.lastname: Shen
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Zongke
authors.initials: Z
authors.lastname: Zhou
authors.forename: Pengde
authors.initials: P
authors.lastname: Kang
authors.forename: Fuxing
authors.initials: F
authors.lastname: Pei
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D002097:C-Reactive Protein / Q000032:analysis; D002516:Ceramics; D002857:Chromium / Q000097:blood; D003035:Cobalt / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D015850:Interleukin-6 / Q000097:blood; D007677:Kidney Function Tests; D008111:Liver Function Tests; D008297:Male; D008875:Middle Aged; D008982:Molybdenum / Q000097:blood; D011446:Prospective Studies; D011474:Prosthesis Design; D013997:Time Factors; D014025:Titanium / Q000097:blood; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D015850:Interleukin-6; D002857:Chromium; D003035:Cobalt; D008982:Molybdenum; D002097:C-Reactive Protein; D014025:Titanium