title: Femoral bone adaptation to unstable long-term cemented total hip arthroplasty in dogs.
abstract: OBJECTIVE
  To evaluate femoral adaptation after unstable long-term cemented total hip arthroplasty (cTHA) in dogs.
  
  
  METHODS
  Clinical study.
  
  
  METHODS
  Four dogs.
  
  
  METHODS
  Paired femurs were examined from client-owned dogs that were donated to a retrieval program after death from causes unrelated to their cTHA. Mean (+/-SEM) dog age was 10.0+/-1.5 years and implant duration was 6.0+/-1.4 years. Implanted femurs had radiographic changes associated with implant loosening and gross mechanical instability at femur retrieval. Femurs were evaluated at 3 levels relative to implant length. Cortical area and medullary area were measured at each level, and cortical porosity was assessed at each level in 4 quadrants and in 3 regions. Implanted femurs were compared with the contralateral non-implanted femurs.
  
  
  RESULTS
  Cortical area and cortical porosity were increased at all levels in femurs with unstable implants. Implanted femurs had increased porosity in all quadrants and regions at the proximal 2 levels, and increased porosity in only the cranial quadrant and mid-cortical area at the distal level, when compared with contralateral non-implanted femurs. Corresponding medullary areas were not different.
  
  
  CONCLUSIONS
  Significant histomorphometric changes occur in femurs after unstable cTHA. The patterns of periosteal bone formation and endosteal bone resorption support mechanisms of stress shielding and wear debris-mediated osteolysis as factors that may contribute to femoral adaptation and implant loosening.
  
  
  CONCLUSIONS
  Despite popularity and excellent return to function with cTHA, aseptic loosening remains a serious long-term complication. Substantial net bone loss and unfavorable environment with unstable cTHA may make revision surgery less successful.
authors.affiliation: Comparative Orthopaedic Research Laboratory, Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 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