title: Severe metal-induced osteolysis many years after unipolar hip endoprosthesis.
abstract: BACKGROUND
  Modularity of the femoral head-neck junction provides increased intraoperative flexibility to the surgeon. Complications of this modularity include damage to the trunnion, with subsequent bone and/or soft tissue loss from adverse reactions to metal debris.
  
  
  METHODS
  We describe two cases of severe metal-induced osteolysis and soft tissue damage requiring revision 10 and 13 years following implantation of a unipolar endoprosthesis. Damage to the trunnion resulted in severe acetabular and trochanteric osteolysis and soft tissue loss requiring complex revision surgery.
  
  
  METHODS
  Several reports have shown the trunnion, the head-neck interface, and the neck-stem couple as the causes of this early failure secondary to metal ion release from mechanical fretting corrosion or from crevice corrosion at these modular interfaces. These reports have been in association with a total hip prosthesis rather than a unipolar endoprosthesis. Revision of a unipolar endoprosthesis is most commonly attributable to stem loosening or acetabular erosion from the large femoral head articulating on the host acetabular cartilage and not owing to failure of the trunnion.
  
  
  CONCLUSIONS
  Trunnion damage resulting in a severe reaction to metal debris with acetabular osteolysis, erosion of the greater trochanter, and loss of the abductor mechanism can occur years after implantation of a cementless unipolar endoprosthesis. This raises questions regarding long-term safety of the modular interface of a contemporary cementless stem and a large-diameter unipolar head. We recommend long-term followup of patients with a unipolar endoprosthesis as early recognition and treatment are required to avoid a potentially complex revision.
authors.affiliation: Division of Orthopaedic Surgery, McGill University, Montreal, QC, Canada.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Mann
authors.forename: Dylan
authors.initials: D
authors.lastname: Tanzer
authors.forename: Michael
authors.initials: M
authors.lastname: Tanzer
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D003343:Corrosion; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D015745:Granuloma, Foreign-Body / Q000209:etiology; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008670:Metals; D010014:Osteolysis / Q000175:diagnosis / Q000209:etiology* / Q000601:surgery; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D012086:Reoperation; D012720:Severity of Illness Index; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D008670:Metals