title: Histological features of pseudotumor-like tissues from metal-on-metal hips.
abstract: BACKGROUND
  Pseudotumor-like periprosthetic tissue reactions around metal-on-metal (M-M) hip replacements can cause pain and lead to revision surgery. The cause of these reactions is not well understood but could be due to excessive wear, or metal hypersensitivity or an as-yet unknown cause. The tissue features may help distinguish reactions to high wear from those with suspected metal hypersensitivity.
  
  
  OBJECTIVE
  We therefore examined the synovial lining integrity, inflammatory cell infiltrates, tissue organization, necrosis and metal wear particles of pseudotumor-like tissues from M-M hips revised for suspected high wear related and suspected metal hypersensitivity causes.
  
  
  METHODS
  Tissue samples from 32 revised hip replacements with pseudotumor-like reactions were studied. A 10-point histological score was used to rank the degree of aseptic lymphocytic vasculitis-associated lesions (ALVAL) by examination of synovial lining integrity, inflammatory cell infiltrates, and tissue organization. Lymphocytes, macrophages, plasma cells, giant cells, necrosis and metal wear particles were semiquantitatively rated. Implant wear was measured with a coordinate measuring machine. The cases were divided into those suspected of having high wear and those suspected of having metal hypersensitivity based on clinical, radiographic and retrieval findings. The Mann-Whitney test was used to compare the histological features in these two groups.
  
  
  RESULTS
  The tissues from patients revised for suspected high wear had a lower ALVAL score, fewer lymphocytes, but more macrophages and metal particles than those tissues from hips revised for pain and suspected metal hypersensitivity. The highest ALVAL scores occurred in patients who were revised for pain and suspected metal hypersensitivity. Component wear was lower in that group.
  
  
  CONCLUSIONS
  Pseudotumor-like reactions can be caused by high wear, but may also occur around implants with low wear, likely because of a metal hypersensitivity reaction. Histologic features including synovial integrity, inflammatory cell infiltrates, tissue organization, and metal particles may help differentiate these causes.
  
  
  CONCLUSIONS
  Painful hips with periprosthetic masses may be caused by high wear, but if this can be ruled out, metal hypersensitivity should be considered.
authors.affiliation: J Vernon Luck Sr MD Orthopaedic Research Center, Orthopaedic Hospital/UCLA, 2400 S Flower Street, Los Angeles, CA 90007, USA. campbell@laoh.ucla.edu
authors.forename: Pat
authors.initials: P
authors.lastname: Campbell
authors.forename: Edward
authors.initials: E
authors.lastname: Ebramzadeh
authors.forename: Scott
authors.initials: S
authors.lastname: Nelson
authors.forename: Karren
authors.initials: K
authors.lastname: Takamura
authors.forename: Koen
authors.initials: K
authors.lastname: De Smet
authors.forename: Harlan C
authors.initials: HC
authors.lastname: Amstutz
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D005260:Female; D005549:Foreign-Body Reaction / Q000209:etiology / Q000473:pathology* / Q000601:surgery; D006104:Granuloma, Plasma Cell / Q000209:etiology / Q000473:pathology* / Q000601:surgery; D006621:Hip Joint / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D006967:Hypersensitivity / Q000209:etiology / Q000473:pathology* / Q000601:surgery; D007592:Joint Diseases / Q000209:etiology / Q000473:pathology* / Q000601:surgery; D008297:Male; D008670:Metals; D008875:Middle Aged; D010149:Postoperative Pain / Q000209:etiology / Q000473:pathology; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D012720:Severity of Illness Index; D013314:Stress, Mechanical; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D008670:Metals
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