title: Corrosion at the head-neck taper as a cause for adverse local tissue reactions after total hip arthroplasty.
abstract: BACKGROUND
  Corrosion at the modular head-neck junction of the femoral component in total hip arthroplasty has been identified as a potential concern, although symptomatic adverse local tissue reactions secondary to corrosion have rarely been described.
  
  
  METHODS
  We retrospectively reviewed the records of ten patients with a metal-on-polyethylene total hip prosthesis, from three different manufacturers, who underwent revision surgery for corrosion at the modular head-neck junction.
  
  
  RESULTS
  All patients presented with pain or swelling around the hip, and two patients presented with recurrent instability. Serum cobalt levels were elevated prior to the revision arthroplasty and were typically more elevated than were serum chromium levels. Surgical findings included large soft-tissue masses and surrounding tissue damage with visible corrosion at the femoral head-neck junction; the two patients who presented with instability had severe damage to the hip abductor musculature. Pathology specimens consistently demonstrated areas of tissue necrosis. The patients were treated with debridement and a femoral head and liner exchange, with use of a ceramic femoral head with a titanium sleeve in eight cases. The mean Harris hip score improved from 58.1 points preoperatively to 89.7 points at a mean of 13.0 months after the revision surgery (p=0.01). Repeat serum cobalt levels, measured in six patients at a mean of 8.0 months following revision, decreased to a mean of 1.61 ng/mL, and chromium levels were similar to prerevision levels. One patient with moderate hip abductor muscle necrosis developed recurrent instability after revision and required a second revision arthroplasty.
  
  
  CONCLUSIONS
  Adverse local tissue reactions can occur in patients with a metal-on-polyethylene bearing secondary to corrosion at the modular femoral head-neck taper, and their presentation is similar to the adverse local tissue reactions seen in patients with a metal-on-metal bearing. Elevated serum metal levels, particularly a differential elevation of serum cobalt levels with respect to chromium levels, can be helpful in establishing this diagnosis.
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois 60612, USA. jcooper02@gmail.com
authors.forename: H John
authors.initials: HJ
authors.lastname: Cooper
authors.forename: Craig J
authors.initials: CJ
authors.lastname: Della Valle
authors.forename: Richard A
authors.initials: RA
authors.lastname: Berger
authors.forename: Matthew
authors.initials: M
authors.lastname: Tetreault
authors.forename: Wayne G
authors.initials: WG
authors.lastname: Paprosky
authors.forename: Scott M
authors.initials: SM
authors.lastname: Sporer
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Jacobs
mesh_terms: D000328:Adult; D000368:Aged; D000886:Anthropometry; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000379:methods; D015992:Body Mass Index; D002857:Chromium; D003035:Cobalt; D015331:Cohort Studies; D003343:Corrosion; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design / Q000009:adverse effects* / Q000379:methods; D011475:Prosthesis Failure; D016459:Prosthesis-Related Infections / Q000175:diagnosis / Q000601:surgery; D020127:Recovery of Function; D012086:Reoperation; D012189:Retrospective Studies; D018570:Risk Assessment; D018709:Statistics, Nonparametric; D014025:Titanium; D016896:Treatment Outcome
chemical_list: D002857:Chromium; D003035:Cobalt; D014025:Titanium