title: Femoral bone adaptation to stable long-term cemented total hip arthroplasty in dogs.
abstract: OBJECTIVE
  To quantify long-term bone adaptation after stable cemented total hip arthroplasty (cTHA) in dogs.
  
  
  METHODS
  Clinical study.
  
  
  METHODS
  Fourteen dogs.
  
  
  METHODS
  Femoral specimens were collected from client-owned dogs that were donated after death because of causes unrelated to their cTHA. Mean (+/-SEM) dog age was 11.4+/-0.7 years and implant duration was 5.3+/-0.7 years. Implant stability was established from radiographic signs and gross mechanical stability. Femurs were evaluated at 3 levels based on implant length: proximal stem (PS), mid-stem (MS), and distal to stem (DS). Cortical area, medullary area, and porosity were measured at each level. Implanted femurs were compared to contralateral nonimplanted femurs.
  
  
  RESULTS
  Cortical area and cortical porosity were significantly increased in implanted femurs compared to nonimplanted femurs. Cortical area was increased at the MS and DS levels, and porosity was increased at the PS and MS levels in implanted femurs. Porosity was greatest in the endosteal region at the PS and MS levels in implanted femurs.
  
  
  CONCLUSIONS
  Significant differences in femoral geometry and cortical porosity were detected after long-term stable cTHA. Net bone loss proximally and increased bone mass distally support stress shielding as a important mechanical factor associated with bone adaptation. Distribution of porosity shifts to endosteal regions after long-term cTHA.
  
  
  CONCLUSIONS
  Significant site-specific femoral adaptation occurs in response to stable cTHA and may precede implant loosening.
authors.affiliation: Comparative Orthopaedic Research Laboratory, Department of Surgical Sciences, University of Wisconsin-Madison, School of Veterinary Medicine, 2015 Linden Drive, Madison, WI 53706, USA.
authors.forename: Mary Sarah
authors.initials: MS
authors.lastname: Bergh
authors.forename: Peter
authors.initials: P
authors.lastname: Muir
authors.forename: Mark D
authors.initials: MD
authors.lastname: Markel
authors.forename: Paul A
authors.initials: PA
authors.lastname: Manley
mesh_terms: D000818:Animals; D019644:Arthroplasty, Replacement, Hip / Q000662:veterinary*; D001843:Bone Cements; D016723:Bone Remodeling; D004285:Dogs; D005269:Femur / Q000503:physiopathology*; D006619:Hip Dysplasia, Canine / Q000601:surgery; D006622:Hip Prosthesis / Q000662:veterinary*; D015207:Osteoarthritis, Hip / Q000601:surgery / Q000662:veterinary; D011475:Prosthesis Failure / Q000662:veterinary
chemical_list: D001843:Bone Cements