title: Gluteal muscle fatty atrophy is not associated with elevated blood metal ions or pseudotumors in patients with a unilateral metal-on-metal hip replacement.
abstract: OBJECTIVE
  There are no international guidelines to define adverse reaction to metal debris (ARMD). Muscle fatty atrophy has been reported to be common in patients with failing metal-on-metal (MoM) hip replacements. We assessed whether gluteal muscle fatty atrophy is associated with elevated blood metal ion levels and pseudotumors.
  
  
  METHODS
  263 consecutive patients with unilateral ASR XL total hip replacement using a posterior approach and with an unoperated contralateral hip were included in the study. All patients had undergone a standard screening program at our institution, including MRI and blood metal ion measurement. Muscle fatty atrophy was graded as being absent, mild, moderate, or severe in each of the gluteal muscles.
  
  
  RESULTS
  The prevalence of moderate-to-severe gluteal muscle atrophy was low (12% for gluteus minimus, 10% for gluteus medius, and 2% for gluteus maximus). Muscle atrophy was neither associated with elevated blood metal ion levels (> 5 ppb) nor with the presence of a clear (solid- or mixed-type) pseudotumor seen in MRI. A combination of moderate-to-severe atrophy in MRI, elevated blood metal ion levels, and MRI-confirmed mixed or solid pseudotumor was rare. Multivariable regression revealed that "preoperative diagnosis other than osteoarthrosis" was the strongest predictor of the presence of fatty atrophy.
  
  
  CONCLUSIONS
  Gluteal muscle atrophy may be a clinically significant finding with influence on hip muscle strength in patients with MoM hip replacement. However, our results suggest that gluteal muscle atrophy seen in MRI is not associated with either the presence or severity of ARMD, at least not in patients who have been operated on using the posterior approach.
authors.affiliation: a Coxa Hospital for Joint Replacement , Tampere , Finland .
authors.forename: Aleksi
authors.initials: A
authors.lastname: Reito
authors.affiliation: a Coxa Hospital for Joint Replacement , Tampere , Finland .
authors.forename: Petra
authors.initials: P
authors.lastname: Elo
authors.affiliation: a Coxa Hospital for Joint Replacement , Tampere , Finland .
authors.forename: Jyrki
authors.initials: J
authors.lastname: Nieminen
authors.affiliation: a Coxa Hospital for Joint Replacement , Tampere , Finland .
authors.forename: Timo
authors.initials: T
authors.lastname: Puolakka
authors.affiliation: a Coxa Hospital for Joint Replacement , Tampere , Finland .
authors.forename: Antti
authors.initials: A
authors.lastname: Eskelinen
mesh_terms: D000273:Adipose Tissue / Q000473:pathology; D000328:Adult; D000367:Age Factors; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000379:methods; D002081:Buttocks; D016009:Chi-Square Distribution; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006104:Granuloma, Plasma Cell / Q000150:complications* / Q000473:pathology; D006622:Hip Prosthesis / Q000009:adverse effects; D006801:Humans; D007477:Ions / Q000097:blood; D008297:Male; D061825:Metal-on-Metal Joint Prostheses / Q000009:adverse effects*; D008670:Metals / Q000097:blood; D008875:Middle Aged; D009133:Muscular Atrophy / Q000209:etiology* / Q000473:pathology; D011475:Prosthesis Failure; D012189:Retrospective Studies; D018570:Risk Assessment; D012737:Sex Factors; D018709:Statistics, Nonparametric
chemical_list: D007477:Ions; D008670:Metals