title: Promising Mid-term Results With a Cup-cage Construct for Large Acetabular Defects and Pelvic Discontinuity.
abstract: BACKGROUND
  Restoring normal anatomy and achieving stable fixation of the acetabular component can be especially challenging when the surgeon must deal with severe acetabular defects and/or pelvic discontinuity. The cup-cage (CC) construct, where an ilioischial cage is cemented within a biologically fixed porous metal cup, has emerged as an excellent option to treat such challenges.
  
  
  OBJECTIVE
  We sought to determine (1) mid-term Kaplan-Meier survival; (2) clinical outcomes based on Merle d'Aubigné-Postel scores; (3) radiological outcomes based primarily on construct migration; and (4) the complication rate for a series of 67 CC procedures performed at our institution.
  
  
  METHODS
  All hip revision procedures between January 2003 and March 2012 where a CC was used (with the exception of tumor cases or acute fracture; four total cases) that had a minimum 2-year followup and that had been seen within the last 2 years were included in this retrospective review. Acetabular bone loss and presence of pelvic discontinuity were assessed according to the Gross classification. Sixty-seven CC procedures with an average followup of 74 months (range, 24-135 months; SD, 34.3) months were identified; 26 of 67 (39%) were Gross Type IV and 41 of 67 (61%) were Gross Type V (pelvic discontinuity). Postoperative clinical and radiological evaluation was done annually. Merle d'Aubigné-Postel scores were recorded and all radiographs were compared with the 6-week postoperative radiographs to evaluate for radiographic loosening or migration. Failure was defined as revision surgery for any cause, including infection.
  
  
  RESULTS
  The 5-year Kaplan-Meier survival rate with revision for any cause representing failure was 93% (95% confidence interval [CI], 83.1-97.4), and the 10-year survival rate was 85% (95% CI, 67.2-93.8). The Merle d'Aubigné-Postel score improved significantly from a mean of 6 preoperatively to 13 postoperatively (p < 0.001). Four CC had nonprogressive radiological migration of the ischial flange and they remain stable.
  
  
  CONCLUSIONS
  We believe that the CC construct is a suitable choice to treat chronic pelvic discontinuity; it also remains a reliable option for the treatment of severe acetabular bone defects if stable fixation cannot be obtained through the use of a trabecular metal cup with or without augments.
  
  
  METHODS
  Level IV, therapeutic study.
authors.affiliation: Adult Joint Reconstruction, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada. tomasamenabar@gmail.com.|Orthopaedic Surgery Department, Mount Sinai Hospital, 600 University Avenue, Suite 476A, Toronto, ON, M5G 1X5, Canada. tomasamenabar@gmail.com.
authors.forename: Tomas
authors.initials: T
authors.lastname: Amenabar
authors.affiliation: Adult Joint Reconstruction, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada.
authors.forename: Wael A
authors.initials: WA
authors.lastname: Rahman
authors.affiliation: Adult Joint Reconstruction, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada.
authors.forename: Bandar M
authors.initials: BM
authors.lastname: Hetaimish
authors.affiliation: Division of Arthroplasty, Orthopaedic Surgery Department, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Kuzyk
authors.affiliation: Division of Arthroplasty, Orthopaedic Surgery Department, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Oleg A
authors.initials: OA
authors.lastname: Safir
authors.affiliation: Division of Arthroplasty, Orthopaedic Surgery Department, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Allan E
authors.initials: AE
authors.lastname: Gross
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D005260:Female; D005548:Foreign-Body Migration / Q000209:etiology / Q000601:surgery; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis / Q000009:adverse effects; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016459:Prosthesis-Related Infections / Q000382:microbiology / Q000601:surgery; D011859:Radiography; D012086:Reoperation; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome