title: Adverse local tissue reaction arising from corrosion at the femoral neck-body junction in a dual-taper stem with a cobalt-chromium modular neck.
abstract: BACKGROUND
  Femoral stems with dual-taper modularity were introduced to allow additional options for hip-center restoration independent of femoral fixation in total hip arthroplasty. Despite the increasing availability and use of these femoral stems, concerns exist about potential complications arising from the modular neck-body junction.
  
  
  METHODS
  This was a multicenter retrospective case series of twelve hips (eleven patients) with adverse local tissue reactions secondary to corrosion at the modular neck-body junction. The cohort included eight women and three men who together had an average age of 60.1 years (range, forty-three to seventy-seven years); all hips were implanted with a titanium-alloy stem and cobalt-chromium-alloy neck. Patients presented with new-onset and increasing pain at a mean of 7.9 months (range, five to thirteen months) following total hip arthroplasty. After serum metal-ion studies and metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) revealed abnormal results, the patients underwent hip revision at a mean of 15.2 months (range, ten to twenty-three months). Tissue specimens were examined by a single histopathologist, and the retrieved implants were studied with use of light and scanning electron microscopy.
  
  
  RESULTS
  Serum metal levels demonstrated greater elevation of cobalt (mean, 6.0 ng/mL) than chromium (mean, 0.6 ng/mL) or titanium (mean, 3.4 ng/mL). MRI with use of MARS demonstrated adverse tissue reactions in eight of nine patients in which it was performed. All hips showed large soft-tissue masses and surrounding tissue damage with visible corrosion at the modular femoral neck-body junction. Available histology demonstrated large areas of tissue necrosis in seven of ten cases, while remaining viable capsular tissue showed a dense lymphocytic infiltrate. Microscopic analysis was consistent with fretting and crevice corrosion at the modular neck-body interface.
  
  
  CONCLUSIONS
  Corrosion at the modular neck-body junction in dual-tapered stems with a modular cobalt-chromium-alloy femoral neck can lead to release of metal ions and debris resulting in local soft-tissue destruction. Adverse local tissue reaction should be considered as a potential cause for new-onset pain in patients with these components, and early revision should be considered given the potentially destructive nature of these reactions. A workup including serologic studies (erythrocyte sedimentation rate and C-reactive protein), serum metal levels, and MARS MRI can be helpful in establishing this diagnosis.
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, 1611 West Harrison Street, Suite 300, Chicago, IL 60612, USA.
authors.forename: H John
authors.initials: HJ
authors.lastname: Cooper
authors.forename: Robert M
authors.initials: RM
authors.lastname: Urban
authors.forename: Richard L
authors.initials: RL
authors.lastname: Wixson
authors.forename: R Michael
authors.initials: RM
authors.lastname: Meneghini
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Jacobs
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D015415:Biomarkers / Q000097:blood; D002857:Chromium / Q000097:blood; D002858:Chromium Alloys; D003035:Cobalt / Q000097:blood; D003343:Corrosion; D005260:Female; D005549:Foreign-Body Reaction / Q000097:blood / Q000175:diagnosis / Q000209:etiology* / Q000601:surgery; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011475:Prosthesis Failure / Q000009:adverse effects* / Q000209:etiology; D012086:Reoperation; D012189:Retrospective Studies; D014025:Titanium / Q000097:blood
chemical_list: D015415:Biomarkers; D002858:Chromium Alloys; D002857:Chromium; D003035:Cobalt; D014025:Titanium