title: Bipolar hip arthroplasty as a salvage treatment for instability of the hip.
abstract: BACKGROUND
  Recurrent instability of the hip in the absence of an identifiable cause is a challenging problem. It has been proposed that bipolar hip arthroplasty may have a role in the treatment of these complex cases. The purpose of our study was to evaluate the results of bipolar hip arthroplasty for the treatment of recurrent instability of the hip in a series of patients at our institution.
  
  
  METHODS
  We reviewed the records of twenty-seven patients who had undergone bipolar hip arthroplasty as a salvage procedure for the treatment of recurrent instability of the hip after total hip replacement. All patients had undergone at least two, and a mean of three, stabilizing operative procedures on the hip prior to the bipolar arthroplasty. The mean duration of follow-up was five years (range, two to twelve years), with no patient lost to follow-up. There were six deaths, of unrelated causes.
  
  
  RESULTS
  Bipolar arthroplasty prevented redislocation in twenty-two hips (81 percent). At the time of final follow-up, twenty-five patients (93 percent) had a stable hip. Five patients (19 percent) had had episodes of subluxation or dislocation following the bipolar arthroplasty. Two of these patients had only a single episode of dislocation that was treated successfully by immobilization. Two of the remaining three patients required a reoperation because of the instability. The hip was stabilized with the use of a constrained cup prosthesis in one of these patients, and the other patient eventually required resection arthroplasty. The third patient had continuing instability but improved function and pain relief, and a reoperation was not performed. There were a total of seven reoperations; these included revision because of disassembly of the cup in one hip, revision bipolar arthroplasty because of continuing instability in two, resection arthroplasty because of deep infection in two, revision arthroplasty because of recalcitrant groin pain in one, and revision arthroplasty because of deep infection and superior migration of the implant in one. The Harris hip score improved significantly, from a mean of 24 points (range, 5 to 45 points) preoperatively to a mean of 55 points (range, 35 to 80 points) postoperatively (p < 0.05).
  
  
  CONCLUSIONS
  We believe that, despite some potential problems, bipolar hip arthroplasty can have a role in the salvage management of recurrent instability of the hip in patients in whom other stabilization procedures have failed.
authors.affiliation: Department of Orthopedics, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: J
authors.initials: J
authors.lastname: Parvizi
authors.forename: B F
authors.initials: BF
authors.lastname: Morrey
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006621:Hip Joint; D006622:Hip Prosthesis / Q000009:adverse effects; D006801:Humans; D007593:Joint Instability / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000453:epidemiology; D012008:Recurrence; D012086:Reoperation; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome