title: Segmental acetabular rim defects, bone loss, oversizing, and press fit cup in total hip arthroplasty evaluated with a probabilistic finite element analysis.
abstract: Management of segmental rim defects and bone mineral density (BMD) loss in the elderly prior to total hip replacement is unclear within classification systems for acetabular bone loss. In this study, our objectives were (1) to understand how a reduction in BMD in the elderly affects the oversizing of a press-fit cup for primary fixation and (2) to evaluate whether the location of the segmental defect affected cup fixation.
  
  
  
  A finite element (FE) model was used to simulate and evaluate cup insertion and fixation in the context of segmental rim defects. We focused on the distribution of patients over age 70 and used BMD (estimated from CT) as a proxy for aging's implications on THR and used probabilistic FE analysis to understand how BMD loss affects oversizing of a press-fit cup.
  
  
  
  A cup oversized by 1.10 ± 0.28 mm provides sufficient fixation and lower stresses at the cup-bone interface for elderly patients. Defects in the anterior column and posterior column both required the same mean insertion force for cup seating of 84% (taken as an average of 2 anterior column and 2 posterior column defects) compared to the control configuration, which was 5% greater than the insertion force for a superior rim defect and 12% greater than the insertion force for an inferior rim defect.
  
  
  
  A defect along the superior or inferior rim had a minimal effect on cup fixation, while a defect in the columns created cup instability and increased stress at the defect location.
authors.affiliation: Department of Orthopaedics, University of Illinois at Chicago, 835 S. Wolcott Ave, Room E270, Chicago, IL, 60612, USA. amirouch@uic.edu.
authors.forename: Farid
authors.identifier: 0000-0002-3002-4199
authors.initials: F
authors.lastname: Amirouche
authors.affiliation: Department of Orthopaedics, University of Illinois at Chicago, 835 S. Wolcott Ave, Room E270, Chicago, IL, 60612, USA.
authors.forename: Giovanni F
authors.initials: GF
authors.lastname: Solitro
authors.affiliation: College of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: Amit
authors.initials: A
authors.lastname: Walia
authors.affiliation: Department of Orthopaedics, University of Illinois at Chicago, 835 S. Wolcott Ave, Room E270, Chicago, IL, 60612, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Gonzalez
authors.affiliation: Department of Orthopaedics, University of Illinois at Chicago, 835 S. Wolcott Ave, Room E270, Chicago, IL, 60612, USA.
authors.forename: Aimee
authors.initials: A
authors.lastname: Bobko
mesh_terms: D000077:Acetabulum / Q000473:pathology / Q000601:surgery*; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D015519:Bone Density; D020342:Finite Element Analysis; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D010024:Osteoporosis / Q000150:complications* / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000379:methods
keywords: Cup stability; Finite element analysis; Monte Carlo simulation; THA revision; Total hip replacement; Under-reaming