title: High Failure Rate of Modular Exchange With a Specific Design of a Constrained Liner in High-Risk Patients Undergoing Revision Total Hip Arthroplasty.
abstract: Addressing recurrent instability in patients with poor bone stock and inadequate abductor tensioning remains a challenge in revision total hip arthroplasty. One treatment method is implantation of a constrained liner. The purpose of this study was to determine clinical outcomes, redislocation rate, and revisions of a focally constrained liner in a high-risk patient cohort.
  
  
  
  Fifty-eight hips between 2008 and 2011 underwent implantation of a focally constrained liner. Nineteen were placed concurrent with acetabular component revision and 39 were placed into a well-fixed acetabular shell. Mean age was 69 years and mean number of previous ipsilateral hip surgeries was 4.2. At mean follow-up of 3.5 years, we analyzed clinical outcomes, redislocation, and revisions.
  
  
  
  Mean Harris Hip Scores was 74. Fourteen hips (24%) were revised and 3 hips (5%) required reoperation at final follow-up. Eleven hips (19%) redislocated at a mean time to dislocation of 12.2 months; 31% (11 of 36 patients) that underwent modular exchange specifically for instability redislocated. Risk factors for redislocation included number of previous surgeries (P = .013), implantation of a 28 mm femoral head (hazards ratio 12.8), revision indication of instability (P = .04), and modular exchange with constrained liner implantation without acetabular shell revision (P = .01).
  
  
  
  Implantation of a focally constrained liner in revision total hip arthroplasty for recurrent instability has a high failure rate, especially with a modular exchange. Although concurrent acetabular revision had a lower redislocation rate, the decision to revise a well-fixed cup should be weighed with potential complications associated with cup revision.
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Chalmers
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.
authors.forename: Diren
authors.initials: D
authors.lastname: Arsoy
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.
authors.forename: Rafael J
authors.initials: RJ
authors.lastname: Sierra
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.
authors.forename: David G
authors.initials: DG
authors.lastname: Lewallen
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Trousdale
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D015331:Cohort Studies; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D012307:Risk Factors; D016896:Treatment Outcome
keywords: cemented liner; constrained liner; dislocation; instability; modular exchange; revision total hip arthroplasty